INDUSTRIAL SEWER DEMAND MODELING: APPLICATIONS AND LIMITATIONS
Alastair Moore
BSc., University of British Columbia, 1990
RESEARCH PROJECT SUBMITTED IN PARTIAL FULFILLMENT OF
THE REQUIREMENTS FOR THE DEGREE OF
MASTER OF NATURAL RESOURCES MANAGEMENT in the
School of Resource and Environrnentd Management Report No. 247
O Alastair Moore 1999 SIMON FRASER UNIVERSITY August 1999
Al1 rights reserved. This work may not be reproduced in whole or in part, by photocopy or other means, without permission of the author. National Library Bibliothèque nationale 1+1 ,,nada du Canada Acquisitions and Acquisitions et Bibliographie Services services bibliographiques 395 Wellingîon Street 395. rue Wellington OnawaON K1A ûN4 OcrawaON K1A Wb4 canada canada
The author has granted a non- L'auteur a accordé une licence non exclusive licence allowing the exclusive permettant à la National Library of Canada to Bibliothèque nationale du Canada de reproduce, loan, distribute or sell reproduire, prêter, distribuer ou copies of this thesis in microfonn, vendre des copies de cette thèse sous paper or electronic formats. la forme de microfiche/lfilm, de reproduction sur papier ou sur format électronique.
The author retains ownership of the L'auteur conserve la propriété du copyright in this thesis. Neither the droit d'auteur qui protège cette thèse. thesis nor substantial extracts fkom it Ni la thèse ni des extraits substantiels may be printed or otherwise de celle-ci ne doivent être imprimés reproduced without the author's ou autrement reproduits sans son permission. autorisation. Abstract Rapid population growth in the Greater Vancouver Sewerage and Drainage District (GVS&DD) means that industrial customers are placing increased pressure upon limited sewer system capacity. GVS&DD managers must satisfy fùture industrial demand wi thout ignoring public concems over local air and water quality, transportation, and burdensome municipal taxes. Long-term comprehensive wastewater management and planning, including a reliable industrial sewer demand forecast, are needed.
This paper develops and then evaluates potential applications and limitations of an industrial sewer demand forecasting mode1 for the Vancouver area. Although relatively small in volume, industrial wastewater discharges cmoAen account for significant, and oftentimes variable, flow and pollutant loadings at district wastewater treatment plants (WWTPs). A survey of other North Amencan jurisdictions indicates that industrial sewer demand forecasts are not comrnon. The benefits of a more robust forecast of sewer demand are nevertheless becorning more evident; the cost of misreading the friture include environmental damage and social welfare and economic losses.
The model relies on the assumption that industrial employment and industrial wastewater discharges are correlated. From this assumption, baseline forecasts are produced through 2021 for industrial flow, biochemical oxygen demand, and total suspended solids for each of the region's five wastewater treatment plants. However, a lack of industrial employment and output data produces forecast uncertainty and prevents model verification. Forecast uncertainty means that the model can only be used to sirnulate relative impacts of policies, regulations, or changes in economic conditions on industrial flow and loadings.
Additional data are needed before the forecasts can be considered accurate. Consequently, the report recommends that additional industrial employment and output data be collected if the benefits of such an undertaking are estimated to exceed the costs. In memory of my mother Acknowledgements
This project was made possible by the support of many people. First, 1 would like to thank the Greater Vancouver Regional District (GVRD)for their financial support. Specifically, 1 am very gratefiil for the encouragement, data, and reviews that were offered by my former GVRD colleagues; Hew McConnell, Cristina Jacob, Jeff Gogol, Paul Kadota, Ralph Perkins, and the staffat Source Control.
Dr. Chad Day and Dr. Michael Bradford comprised my supervisos. committee and deserve my heartfelt gratitude for their guidance and encouragement. In addition to the formal help provided by my committee, I received endless encouragement from my fdlow students and staff members in the School of Resource and Environmental Management. For their friendship and support 1 am very thankful.
1 would also like to thank Maria, Bogue, Anne, and my father Bryan, for their boundless encouragement and support over the years. This work was also inspired by my mother who's memory serves as a constant reminder of what life is al1 about.
Finally, 1 reserve my most special thanks for Dominica-my fellow student, colleague, and wife. What it would have been like to complete this work without you, 1 care not to imagine. With you by my side however, this project has been nothing short of a pleasure! ABSTRACT ...... ACKNOWLEDGEMENTS ...... V TABLES ...... rr...... VUI FIGURES ...... IX ACROrYYMS ...... X CHAPTER 1 .INTRODUCTION ...... 1 BACKGROUND...... 1 Challenges Facing Wastewater Utilities...... 1 STUDYCONTEXT ...... 6 PROBLEMSTATEMENT ...... 7 IMPORTANCE OF AN INDUSTRIALSEWER DEMAND MODEL ...... 8 PURPOSEAND OBJECTIVES...... 12 SIGNIFICANCEOF RESEARCH ...... 13 STUDYMETHODOLOGY ...... 14 Literature Revïew ...... 14 Strrvey of North Amencan Jurisdictions ...... 14 Data Collecrion .....*...... 14 Model Development and Evaluation ...... 15 SCOPE...... 15 REPORTORGANIZATION ...... 16 CHAPTER 2 .MUNICIPAL WASTE WATER ...... 17 SEWERDEVELOPMMT IN NORTHAMERICA ...... 17 Treaiment Levels ...... 19 Treabnent Process by-Products ...... -7 -7 P rinciple Wastewater Contponents ...... 23 SEWERDEVELOPMMT IN GVRD ...... 24 MUNICIPALEFFLUENT AND THE ENVIRONMENTIN THE GVRD ...... 26 Wastewater Treatment Plants ...... 27 Regulations ...... 32 Cost Drivers ...... 36 Impacts of Municipal Efluent on the Environment ...... 37 INDUSTRIAL WASTEWATER...... 38 Potential to Disrupt Trearment Procas ...... 39 Industrial Flow and Loadings in G VS& DD ...... 40 Industrial Wasrewarer by IVWTP ...... 42 Environmental Regutarions and Enforcement ...... 43 Source Control ...... 45 INDUSTRIAL WASTEWATER:SPECIAL ISSUES ...... 49 Impacts on Sewer Operations ...... 49 Changes in Indusirial Sewer Deniand ...... 49 Wastewater Limits ...... 50 Industrial Flexibility and Innovation ...... 52 SUMMARY...... 53 CHAPTER 3 .SEWR PLANNING AND DEMAND FORECASTING ...... 54 PLANN~NGOVERVIEW ...... 54 Planning in the GVS&DD...... 54 SEWERDEMAND FORECASTING OVERVIEW ...... 59 BENEFITSOF A RELIABLEINDUSTRIAL SEWERDEMAND FORECAST IN GVS&DD...... 61 FORECASTINGTECHNIQUES ...... 62 Time Extrapolation ...... 62 Bivariate Modeis ...... 63 Per Capita Requirements Method ...... 63 Multivanate Models ...... 63 Econometrïc Demand ~Models...... 64 Sewerage Requirernents Approach ...... 64 IWR-MAIN Warer Demand Forecasting Model ...... 65 SURVEY OF NORTHAMERICAN SEWERDEMAND FORECASTMG APPROACHES ...... 67 GVS&DD ...... 67 North America ...... 70 SURVEYRESULTS ...... 75 OBSTACLESTO INDUSTRIAL SEWERDEMAND FORECAS~G M GVS&DD ...... 78 CWTER4 .GVS&DD INDUSTRIAL SEWER DEMAND FORECASTING MODEL ...... 80
DATA...... ,...... 84 Significant Industrial Dischargers ...... 84 Industrial Wastewater Data ...... 85 Industrial FVastewater Data Processing ...... 86 Total Employment Data Processing ...... 88 G VS&Di3 Permined Cornpanies: His ton-cal Employment Data ...... 95 MODELCALIBRATION ...... 95 Daily Flow Coeficients and BOD and TSS follutant Concentrations ...... 95 Landfill Contributions ...... 97 Model Verifcation ...... 97 BASELINERESULTS ...... 98 Drscussio~...... 99 Model Applications ...... 100 Assumprions und Limitations ...... 100 Surnmary ...... 115 CHAPTER 5 .MODEL APPLICATION AND SIMULATION ...... 116 SCENARIOSIMULATION ...... 116 Simulation Results ...... 117 CHAPTER 6 .CONCLUSIONS AND RECOMMENDATIONS ...... 123 CONCLUSIONS...... 123 Current State of Industrial Sewer Demand Forecasting ...... 123 Model Applications ...... 124 Model Limitations ...... 124 Saverage System Management and Environmental Quality ...... 126 RECOMMENDATIONS...... 128 APPENDIX 1: WDUSTRY SUBSECTOR CHARACTERIZATIONS ...... ,.. 129 APPENDIX 2: INDUSTRlAL SEWER DEMAND MODEL MPUT SHEET ...... 157 GVS&DD WASTEWATERTREATMENT PLANTS: 1995 RECORDOF COMPLIANCE...... 35 GVS&DD SEWERAGEAND DRAINAGEUNIT SYSTEM COSTS - 1996 ...... 36 GVS&DD 1997 WASTEWATERTREATMENT PLANT INDUSTRIAL FLOWAND LOADMGS...... 41 GVS&DD TOP-UNKEDINDUSTRY SECTORS FOR DISCHARGESTO -S ...... 43 CURRENTGVS&DD WASTEWATERFLOW AND LOADINGS:ACTUAL AND PROJECTIONS...... 69 NORTHAMERICAN SURVEY RESULTS ...... 77 GVS&DD SEWERAGEAREAS AND WASTEWATERTREATMENT PLANTS ...... 81 INDUSTRIAL SUBSECTORSIN GVS&DD ...... 85 INDUSTRIALSUBSECTORS OPERAT~NG WITHIN EACH SEWERAGEAREk ...... 89 TOTALGVS&DD EMPLOYMENT...... 91 GVS&DD INDUSTRIALEMPLOYMENT ...... 94 INDUSTRlAL FLOWCOEFFICIENTS. POLLUTANT CONCENTRATIONS AND CORRE~ONFACTORS ...... 96 BASELINEFORECAST: INDUSTRIAL FLOWAND LOADINGS...... 98 PERCENTAGEOF REGIONALEMPLOYMENT CONTRIB~D BY MANUFACTURING SECTOR (ESTIMATESAND PROJECTIONS)...... 111 FIGURE1 SUSTAINABLEMANAGEMENT FRAMEWORK FOR OPTIMAL PROTECTION OF RECEIVING WATER QUALITY...... 9 FIGURE2 CURRENT RZAMEWORK FOR SEWERAGE SYSTEM MANAGEMENT AND PROTECnON OF RECEIVMG WATER QUALITY...... 11 FIGURE 3 MAP OF GVS&DD SEWERAGEAREAS AND FACILITES...... 31 FIGURE 4 INDUSTRIAL CONTRIBUTIONS TO WWTP ~UFLUENTFLOW AND LOADINGS(1 997) ...... 42 FIGURE5 TRENDSCN PERCENTAGEOF TOTALREGIONAL EMPLOYMENT CONTAINED WITHINGVS&DD SEWERAGEAREAS: 1991 - 2021 ...... 57 FIGURE6 MODELCONCEPTUALIZATION ...... 82 F~GURE7 INFLUENCEOF PRODUCTWITYINDICES ON FSA DAILY NDU US TRIAL LOADINGFORECASTS ... 102 FIGURE8 INFLUENCEOF PRODUCTIVITYINDICES ON FSA DAILYINDUSTRIAL FLOWFORECASTS ...... 102 FIGURE9 FSA INDUSTRIALFLOW: 90%, 50%, AND 25% CERTAMTYRANGES & 10% S.D...... 104 FIGURE 10 FSA INDUSIRIAL FLOW:90%, 50%. AND 25% CERTAMTYRANGES & 20% S.D...... 105 FIGURE1 1 FSA INDUSTR~ALFLOW: 90%, 50%, AND 25% CERTAW RANGES & 30% S.D...... 105 FIGURE12 FSA INDUSTRIAL BOD: 90%, 50%, AND 25% CERTAINTYRANGES & 10% S.D...... 106 FIGURE13 FSA INDUSTR~ALBOD: 90%, 50%, AND 25% CERTAM~RANGES & 20% S.D...... 106 FIGURE 14 FSA INDUSTRIALBOD: 90%. 50%, AND 25% CERTAM~RANGES & 30% S.D...... 107 FrGuRE 15 FSA INDUSTRIAL TSS: 90%, 50%, AND 25% CERTAW RANGES & 10% S.D...... 107 FIGURE16 FSA INDUSTRIALTSS: 90%, 50%. AND 25% CERTAM~RANGES & 20% S.D ...... 108 F~GURE17 FSA INDUSTRIALTSS: 9096, 50%. AND 25% CERTA~NTYRANGES & 30% S.D...... 108 FIGURE18 FRASERSEWERAGE AREA: FLOWSENSITIVITY TO ERRORSîN GMS EMPLOYMENTPROJECTIONS ...... 110 F1GuR.E 19 FRASERSEWERAGE AREA: BOD SENSITIV~TYTO ERRORSIN GMS EMPLOYMENTPROJECTIONS ...... 110 FIGURE20 FRASERSEWERAGE AREA: TSS SENSITIV~TYTO ERRORSM GMS EMPLOYMENTPROJE~ONS ...... 111 FIGURE2 1 FRASERSEWERAGE AREA: FLOWSENSI~VITY TO CHANGES CN 2006 & 2021 INDUSTRIAL EMPLOYMENTPERCENTAGE PROJE~ONS ...... 112 FIGURE 22 FRASERSEWERAGE AREA: BOD SENS~TIVITYTO CHANGESW 2006 & 202 1 INDUSTRIAL EMPLOYMENTPERCENTAGE PROJECTIONS ...... 112 FIGURE23 FRASERSEWERAGE Am: TSS SENSI~INTO CHANGES IN 2006 & 2021 INDUSTFUAL EMPLOYMENTPERCENTAGE PROJECTIONS ...... 113 FIGURE24 FSA FLOW:BASELME & SCENARJOSIMULATION CONDITIONS ...... 118 FIGURE25 FSA BOD & TSS: BASELINE& SCENARJO SIMULATION CONDITIONS ...... 119 FIGURE26 MANAGEMENTFRAMEWORK FOR SEWERAGE SYSTEM MANAGEMENT AND PROTECïiON OF RECEIVMG WATER QUALITY AFïER ADDITION OF MDUSTRIAL SEWER DEMAND MODEL ...... 127 Acronyms
ADWF Average Dry Weather Flow BOD Biochemical Oxygen Demand CEPA Canadian Environmental Protection Act CERCLA Comprehensive Environmental Response, Compensation, anc3 Liaibility Act (US) of 1980 CMHC Canada Mortgage and Housing Corporation CRD Capital Regional District (Victoria) CS0 Combined Sewer Overflow CTM Contacts Target Marketing CWA Clean Water Act DFO Department of Fisheries and Oceans DSM Demand-side Management FSA Fraser Sewerage Area GCA Growth Concentration Area GDP Gross Domestic Product GIS Geographicd Information System GMS Growth Management Strategy GVRD Greater Vancouver Regional District GVS&DD Greater Vancouver Sewerage and Drainage District-an ami of the GVRD LIWSA Lulu Island West Sewerage Area LRSP Livable Region Strategic Plan LWMP Liquid Waste Management Plan NAICS North American Industrial Classification System NSSA North Shore Sewerage Area NWLSA Northwest Langley Sewerage Area OCP Officia1 Comrnunity Plan PF Peaking Factor POTW Publicly Owned Treatment Works PWWF Peak Wet Weather Flow RCRA Resource Conservation and Recovery Act SEPH Survey of Earnings, Payroll and Hours SIC Standard Industrial Classification SWMM Storm Water Management Mode1 TSS Total Suspended Solids TWG Technical Working Group VSA Vancouver Sewerage Area WMA Waste Management Act WSSC Washington Suburban Sanitary Commission WTP Wastewater Treatment Plant Chapter 1 - Introduction
Background
Challenges Facing Wastewater Utilities Those responsible for providing wastewater collection and treatment services in j urisdictions across North Amenca face many challenges today. Management of local governent responsibilities such as water supply, roads, environmental quality, public safety, and sewers, is complicated by persistent debates conceming optimal service levels and acceptable trade-offs. Sewerage management, once seen as a relatively straightforward business, is now dominated by many concems. These include: rapid urban population growth; increasingly stringent environmental regulations; public health concems; financial rationalization; the cost of maintaining old and inefficient facilities; and satisfying an ever-increasing dernand for services. Challenges facing sewerage facility managers in the Greater Vancouver Regional District (GVRD) pose no exception to this description. The impacts of rapid population growth are already evident and predictions suggest that pressures on sewer infrastructure will only increase in intensity with tirne.
Population Growth "OnIy 1 in 10 people Iived in cities when this century began; more than half will by the century's end" (Brown 1992). This prediction is reflected in the rapid population and economic growth observed in GVRD over the last decade. Between 199I and 1996, the growth rate in the region was higher than in any other metropolitan area in Canada. Population in the region increased by 230,000 people (14.3%) to 1,832,000, more than twice the national average. The growth rate for the previous five year period was even higher at 16.1% (GVRD 1997: 8), highlighting the need for expansions and upgrades to the sewerage system. In addition, the Greater Vancouver Regional District Sewage Review Panel is concemed that the increase in population in areas south of the Fraser River and east of GVS&DD will cause liquid waste problems for the district. It believes this emerging problem can only be addressed by way of regional planning in respect of the Fraser River valley and delta, fiom Chilliwack to Georgia Strait. By the year 202 1, based on existing official community plans, which are subject to amenciments to accommodate additional density, the populations of Kent, Matsqui and Abbottsford will more than double and the populations of Mission and Chilliwack will triple. The highest population growth rates will be found in the eastern sectors of the valley. The panel recomrnended that the Greater Vancouver Regional District's Liquid Waste Management Plan (LWMP) be stnictwed in the context of the region as a whole and not as an artificial segment of the region (Lidstone et al. 1993: 7).
Environmental Regulations The natural environrnent in GVRD has succumbed to the affects of prolonged pollution by the region's inhabitants over the past 60 years. Both the Burrard Inlet and the Fraser River show disturbing signs of environmental damage. Wastewater discharges, as sewage has corne to be known, has played a major role in environmental damage according to the Report of the Sewage Treafment Review Panel written by the panel as part of GVRD's Iiquid waste management planning process (Lidstone et al. 1993: 1). The quality of the waters surrounding Vancouver generally range fiom 'fair' to 'poor'. Sewage effluent is acknowledged by the district to be a significant source of contaminants to this degraded receiving environrnent (Sierra Legal Defense Fund 1994: 9). In support of this assessrnent of local water quality, citizens of the region identified improving the sewerage system's environmental protection performance as a priority in Creafing Our Future (GVRD 1992: 6). This led to development of a long-range plan that identified close to 51 billion worth of sewerage system upgrading to be completed by 2004 (GVRD 1997).
If US experience is an indicator of what lies ahead in terms of environmental liability for sewerage service providers, Canadian wastewater utilities can expect increasing pressure to act di ligentl y to protect the environment. The Comprehensive Environmental Response, Compensation, and Liability Act of 1980-CERCLA or Superjiund-is a potential time bomb for American municipalities that operate publicly owned treatment works (POTW). There is serious doubt whether US POTWs will be exempt fiom liability under the act. Evidence of the impact of CERCLA can be seen in a nurnber of US court decisions including the following. The Washington State District Court jury found the Washington Suburban Sanitary Commission (WSSC) negligent for not preventing or replating specific industrial discharges that eventually leaked out of the collection system and into the groundwater table. WSSC argued that because the Resource Conservation and Recovery Act (RCRA) and CIean Water Act (CWA)allow limited levels of hazardous materials to be discharged to publicly owned treatrnent works, WSSC should not be held liable for PCE leakage from sewer pipes because leakage was foreseeable. The court said that leakage of PCE was not foreseeable because Congress expects POTWs to keep facilities in good repair. (Gmmbles 1997). Histoncally, Canadian environmental legislation has lagged behind the US by roughly 10 years. If so, GVS&DD may view this and other US cases as an early waming for increasingly stringent regulations and the requisite liabilities that go along with them.
Public Health Throughout history, concentrations of population have always been associated with large- scale water and wastewater supply facilities. When public health and safety became mandatory, the sanitary revolution of the late nineteenth and early twentieth centuries increased the dependence of urban civilization on wastewater treatrnent and disposa1 systems. The dependence is no less evident today in the Vancouver area.
When untreated or inadequately treated sewage is dumped or overflows into lakes, rivers, and oceans, it contaminates already fiagile ecosystems, and can cause disease or death for many species. It aIso exerts a domino effect on the entire food chain. Some toxins accumulate in fish and other aquatic organisms. Wastewater pollutes surface water, and ground water, in some cases. As contamination spreads, and vital food, water, and other natural resources becorne increasingly toxic, hurnans feel the impact of this ecological imbalance (Sierra Legal Defense Fund 1994: 32). The comectivity between sewage discharges and human health is evident throughout GVRD as regular beach closures occur in swnmer months due to the hazard to human health posed by high fecal colifonn counts (Sierra Legal Defense Fund 1994: 8). Again, in GVRD's Creating Our Future public consultation process, the citizens of the area expressed their support to programs that ensured public health protection; adequate wastewater treatment is seen as cntical if this goal is to be achieved.
Financial Rationakation Wastewater collection and treatment agencies are expected to serve social objectives related to the rationai management of resources; at the same tirne, they must remain viable as business enterprises. The Sierra Legal Defense Fund's report entitled, The National Sewage Report Card (1994: 3), claimed: "Sewage treatment is undoubtedly the responsibility of municipal governments. However, without federal and provincial fùnding, the cost of treatment deters most cities fiom upgrading facilities" (Sierra Legal Defense Fund 1994: 3). This view is not universal however. In his book, 73e Municipality S Rofe in Water Management (1966), Eric Beecrofi claimed:
The federal and provincial governments share costs of for example-roads, bridges, hospital construction and, to an increasing extent, public housing, urban renewal and urban transportation-on the grounds that these services are beneficial to the country as a whole. It is astonishing that water supply and water pollution, despite their special importance to human health and economic efficiency, are still lefi to depend upon the slender financial resources of the municipalities. Surely, they should be in the category of works of universal concern requiring cost-sharing and mutual assistance in research and planning?
To address persistent problems associated with increased and more diverse demand for sewerage services, many utilities have invested in capital expansion projects at their own expense. However, the high cost of sewerage infiastructure expansions has prompted many to question traditional service supply options.
Faced with growing public debt, unernployrnent and increasing taxes, the public is becoming increasingly concerned about the costs of upgrading and maintaining the quality of the region's air, land, and water. These concerns are translating into demands for greater accountability fiom decision-makers: consideration of al1 issues, direct participation in the process of identimng and evaluating options, and involvement in decision-making. (GVRD 1996: 80) No longer cm utilities afford to simply design and build more sewer infhstructure to satisQ growth demands. Instead, wastewater management systems must be designed and operated in such a way that they consider multiple objectives while still providing a basic level of service. To accomplish this, innovative approaches to sewerage system management must be identified.
Aging Facilities Operation and maintenance of old and inefficient sewerage facilities is extremely costly, but the alternative, that is, to construct new facilities, also cornes at a tremendous cost to taxpayers. Deciding if and when to replace aging sewerage system infrastructure presents a formidable challenge to decision-makers in GVRD.
GVRD budgeted spending increases in 1999 are alrnost exclusively related to upgrades to water and sewer utilities. Sewerage and drainage expenditures in 1999 will increase by 11 percent to $1 19.9 million, while capital expenditures will reach $1 15 million. To address continuing problems caused by an expanding population, the required capital and operating costs for completing regional projects could exceed $3 billion within 10 years. Over half of this amount is required for liquid waste management, $750 million for secondary treatment at the Annacis and Lulu plants, and potentially $1 billion for storrnwater treatment and combined sewer overfiow resolution (Lidstone et al. 1993: 1). Currently, 38 cents per day, up fiom 35 cents in 1998, is the cost that the average household in GVRD pays to handle and treat sewage. Politicians and wastewater system planners in the GVRD will have to find ways to ensure that appropriate service leveis are maintained while keeping costs at levels that the public is willing to accept.
Satisfying lncreasing Oemand for Sewer Services The traditional response to increasing demand for wastewater treatment capacity was the development of additional supply. In planning for urban wastewater treatment systems, the challenge is to determine the optimum combination of al1 alternatives to balance supply and demand (Baumann et al. 1997: 8). Social criteria for evaluating development are becoming more refined and the role of local and regional wastewater utilities is enlarging. For these and other reasons it is increasingly important to cultivate precision and reliability in determinhg demand, forecasting demand, and evaluating various economic, technologie, and social determinants of demand for wastewater treatment. The old paradigm of designing the cheapest reliable supply with little attention to demand determinants, pricing structure, and financial policies is no longer suitable Q3auman.n et al. 1997: xi).
Sfudy Contexf While a significant portion of this study reflects expenences of municipal wastewater utilities across North America, the primary focus is on the wastewater utility operating in the Vancouver area This utility, known as the Greater Vancouver Sewerage and Drainage District, is one axm of the Greater Vancouver Regional District (GVRD).
GVRD is a voluntary partnership of 20 municipalities and two electoral areas representing some 2.0 million people. Acting as a regional government body, GVRD provides essential services to member comrnunities more economically, efficientiy, and equitably than could be achieved at a local level. GVS&DD, operating within GVRD, is a regional entity created by a collection of 18 municipalities in order to provide a crucial regional service to those same municipalities. Al1 things being equal, member municipalities have equal rights to extract services fiom the regional sewerage systern according to its needs.
The powers and functions of the sewerage district, which became part of the Greater Vancouver Regional District in 1971, are exercised by the administration board consisting of most of the same municipal representatives as those appointed to the GVRD's Board of Directors. The GVS&DD Board exercises the powers and functions of the Greater Vancouver Sewerage and Drainage District in order to construct, maintain, and operate the district's collection and treatment system. A commissioner, appointed by the board and subject to its authority, has responsibility for the day-to-day management of the sewerage and drainage system. When it first joined GVRD,the Greater Vancouver Sewerage and Drainage District was comprised of 13 member municipalities, whereas today, there are 18 municipalities in the sewerage district (GVRD 1999). Daily nearly one billion liters of wastewater, including sewage and stom runoff, are collected fiom municipal sewerage systems in 450 kilometers of GVS&DD interceptor sewers. Wastewater flow is distx-ibuted to five treatment plants; two that provide pnmary treatment, and three that provide secondary treatment. The sewerage system, covering more than 1,000 square kilometers and serving a population of 1.8 million is one of the largest in North America.
Sewers built early in the century were designed to convey domestic wastewater only. Today, however, GVS&DD's collection and treatment system receives wastewater fiom a number of residential, commercial and institutional, and industrial sources. This study focuses on only the industrial customer category. It is expected that this body of work will be used in conjunction with similar studies conducted on the remaining customer groups. Emphasis is placed on factors aflecting industrial wastewater discharges fYom industrial operations within the sewerage district, past, present, and fùture. The tirnefiame for this study extends from approximately 1990 to 202 1.
GVS&DD is seeking new tools to deal with the uncertainty inherent in managing a sewerage system effectively. Research on the profile of al1 customer categories is needed before decisions and policies about the fiiture can be made. An information gap concerning the industrial wastewater component of total wastewater flows in the region was identified. The existence of this gap, and the desire to fil1 it, motivated this study.
Problem Statement GVS&DD is committed to achieving the objectives contained in the document entitled, Creating Our Future (GVRD 1992). Of greatest importance to GVS&DD are the objectives which refiect the public's desire to simultaneously ensure both a healthy environment, and a robust economy. While GVS&DD managers have the will to meet these somewhat opposing objectives, certain tools needed to achieve success are missing. Specifically, the absence of an accurate sewer demand forecasting tool to predict demand means that the district continues to be hstrated in its attempts to set policy, meet regulations, and expand treatment capacity. The district continues to incur costs of over- and under-supply of treatment capacity and, consequently, denigrates the quality of the environment or the economic health of the region-possibly both. This paper begins to address this problem by investigating the feasibility of a sewer demand forecasting mode1 for one of the three customer categories, namely, the industrial sector.
Importance of an lndustrja! Sewer Demand Model According to public demands expressed in Creating Our Future, the desired quality of receiving waters should determine stringent water quality standards and, subsequently, equally stringent limits on eMuent fiom the district's WWTPs. Continuing on this track, wastewater treatment plant managers, knowing the limits that effluent fiom each plant is required to meet, would cal1 on the support of source control, liquid waste planners, regional planners, and accurate demand forecasts. Data fiom these sources could be combined to manage sewer demand in a manner that allows al1 wastewater entering plants to be treated adequately pnor to discharge to the environment (fig. 1). In this way the desired health of receiving waters, and the treatment capacity of sewerage facilities, would govern upstream access and usage. RECEMNG WATER QUALrrV
GVS&DD KNOWS HOW MUCH CAPAClfV TO BUlLD & WHEN TO BUlLD IT IN I
Direction of information. policy
Figure 1 Sustainable management framework for optimal protection of receiving water quality. Although attractive, the schematic presented in figure 1 does not apply in GVS&DD today. Instead, the current schematic appears more inverted and reflects little connectivity between receiving water quality objectives, treatment plant performance, and total sewer demand (fig. 2). The three custorner groups-residential, commercial, and industrial- collectively detemine what flow and loadings each treatment plant receives. As a result, treatment capacity is often exceeded, permit violations occur, and environmental damage results. In the absence of changes to provincial and federal govemment water quality standards, an industrial sewer demand mode1 will help to build a more direct interrelationship between treatment plant operations, and projections of demand from the industrial sector. If planners have good information as to the level and timing of future sewer demand, they will be better able to ensure effluent limits are met by providing adequate treatment capacity on time and under financially more controllable circumstances. Under these more sustainable conditions the health of receiving waters are afforded maximum protection. GVS&DD UNSURE OF DEMAND, AMOUNT OF CAPACIT'Y TO BUILD, & WHEN TO BUlLD fT IN ORDER TO QROTECT RECENING WATER QUALIN.
Direction of informaiion B policy
Direction of industrial ,,,fl, C ,,,fl, -RECEMNG WATER Figure 2 Current framework for sewerage system management and protection of receiving water quality. Purpose and Objectives The purpose of this study is to determine the degree to which industrial sewer demand forecasting in GVS&DD is feasible and beneficial to residents of the area The objectives are, a) to develop an industrial sewer demand model for use in GVSⅅ b) identiq the potential applications and limitations of the forecasting model; and c) to make recommendations to enhance sewerage system management and planning in GVS&DD.
To achieve these objectives, a nurnber of questions are investigated: How do industrial wastewater discharges impact on sewerage facifities and the environment and how would an industrial sewer demand model serve to enhance and protect each?
What is the quality and quantity of the wastewater discharged by the industrial sector in GVS&DD and what is the current industrial sewer demand profile?
What is the current status of sewer demand forecasting in GVS&DD and other jurisdictions across North Arnerica?
What are the benefits of an industrial sewer demand forecasting model?
What data are needed to develop an industrial sewer demand model, and if data gaps exist, what data sources cmserve as substitutes? Significance of Research This study represents an important step toward a better understanding of the myriad challenges facing sewer utility planners and forecasters in GVS&DD. Senior staff in the Sewerage and Drainage Department at GVS&DD identified the need for this research. They intend to combine sirnilar research conducted on nonindustrial customer groups with hdings from this study in order to generate a comprehensive sewer demand forecast. Former manager of the Sewerage and Drainage Department at GVRD, Hew McConnell, recognized the need to be able to forecast flow and loadings at GVS&DD treatment plants. In a 16 September 1996 memo, Mccomell stated: ". . . we need to organize a process that forecasts loadings by each of the residential, commercial and industrial sectors."
The forecasting mode1 developed as part of this study is significant for a nurnber of reasons. It, a) will enhance sewerage system management and environmental quality by inverting the diagrarn in figure 2 so that it reflects the more sustainable design presented in figure 1; b) represents a rare attempt to generate an industry-specific forecast of wastewater flows and loadings; c) utilizes data from the industrial subsectors operating within the sewerage district in the mode1 calibration process; and d) is universal, meaning that it cmbe adopted by other local govermnents with onIy minor modifications if appropriate data were available.
Slow or zero growth in tuban population, or the availability of excess systern capacity in other North Arnerican jurisdictions, have minimized the need to develop disaggregated forecasts of sewer demand. However, the importance of this study is likely to become more pronounced as more sewer utilities encounter either increased sewer demand resulting from rapid population growth, or questions about fùture capacity requirements. ln both cases, accurate forecasts of the overall sewer demand profile will be required as planners seek to identifL suitable future sewer service options and alternatives. By virtue of the data collection and analysis required to complete this body of work, valuable characterization information about al1 of the industrial sectors operating in the region was produced. Further, future data collected annually by the district can be incorporated into the mode1 structure, resulting in an increase in the amount of hi~torical data available, and thus, an enhancement of forecast accuracy.
Study Methodology
Literature Review A review of the literature on forecasting theory identifies popular forecasting approaches and demonstrates the degree to which refinernent of industrial wastewater forecasting has been ignored. As a proxy for industrial wastewater demand forecasting, industrial water demand forecasting is used. The similarity between the two provides a useful hework from which to understand causal factors affecting industrial demand for sewer services. Also, historical references are also reviewed in order to help understand the processes that contribute to conditions that presently exist in GVS&DD.
Survey of North American Jurisdictions In order to better assess where the Greater Vancouver Sewerage and Drainage District currently is with respect to industrial sewer demand forecasting, a survey of other jurisdictions in Canada and the United States was conducted. Pnmary data for the survey were obtained through in-depth interviews with utility managers and planners across Canada, and to a lesser extent, the US. Effort was made to survey utiliiies from a variety of economic, clirnatic, and geographical regions within Canada. In addition, the City of Seattle was surveyed owing to its proximity to Vancouver, similar population, economy, and climate.
Data Collection Industrial waste discharge permit monitoring data were obtained in cooperation with the GVS&DD's Source Control Division, and the City of Vancouver's Pollution Control Department. Together, GVS&DD and the City of Vancouver administer approximately 240 waste discharge permits--issued to industrial operations-in the region. Waste discharge permit monitoring requirements necessitate that permit holders submit regular wastewater discharge monitoring results. These data form the foundation of the modeling process.
In addition, a review of the literature provided wastewater characterization data for the types of industry that currently exist within GVS&DD's boundaries. These data were collected to help venQ the data obtained fiom the characterization of industrial discharges within the district.
Historical industrial employment data for companies operating in the region were obtained by way of a voluntary survey. Surveys requesting past employment data were sent to al1 companies holding vatid waste discharge perrnits as of 1998. In addition, demographic, and economic data were obtained fiom journals, reports, and interviews with tocal forecasters.
Model Development and Evaluation Conceptualization and development of the industriai sewer demand forecasting model was directed by data availability and intended friture model uses. The model was cornpartmentalized to reflect GVS&DD's five geographically identified sewerage areas and the WWTPs that treat wastewater fiom each of those areas. Given projections of industrial ernployment and estimates of unit coefficients for industrial flow, and concentrations for biochzmical oxygen demand (BOD) and total suspended solids (TSS), forecasts were generated through 202 1.
Error analyses and a scenario simulation were conducted to evaluate model performance. This process helped to bound model forecasts and identie data gaps and sensitivity to mode1 assumptions.
Scope This research focuses on the industrial sector operating in the GVS&DD. It does not attempt to address the residential and commercial sectors. A sewer demand model is developed for the industrial sector. Model assumptions, and the consequent parameter values used in the model, provide a starting point for evaluating the forecasting process. The mode1 developed as part of this research is intended to generate discussion conceming the relative strengths and weaknesses of industrial wastewater forecasting, as much as it wiIl act as a practicable tool for use by GVS&DD planners and managers.
Repott Organization The first chapter outlines the background to this research, the methodology used, and study context. In the second chapter, a discussion on municipal wastewater management reviews, a) the history and development of the sewer system in the district and across North America; b) the impacts of municipal effluent on the natural environment and the underlying forces which threaten to perpetuate current problems, and; c) wastewater characteristics of the industrial sector in GVS&DD and the challenges that this sector poses for sewer planners. Chapter 3 examines current sewerage system planning and forecasting methods utilized both in GVS&DD, and other North American jurisdictions. Conceptualization and development of the industrial sewer demand forecasting model, plus results of the baseline forecast are described in chapter 4. A scenario simulation demonstrating how the model works, and the ways in which it contributes to a more sustainable sewerage system mar,agement design, comprises chapter 5. Finally, chapter 6 contains a surnmary of research findings and presents recommendations. Chapter 2 - Municipal Wastewater
Sewer Development in North America Prior to the latter half of the nineteenth century, it was unusual for cities to provide comprehensive water supply and wastewater collection service with piped connections to most buildings. Households normally relied on privies or cesspools for disposa1 of human waste and water-using activities were few and infiequent, compared to current lifestyles. However, as urban systems began expanding to meet the needs of the population, water use, and thus wastewater production, levels rose dramaticdly (E3aumann et al. 1997: 2).
Although the sewer has existed in various shapes and sizes around the globe and among civilizations for hundreds of years, its history in North America spans little more than 100 years. Treatment of public sewage in the United States and Canada began about a century ago, and some primary treatment of wastewater by manufacturing plants probably dates back that far also (Gelg 1976: 3). The evolution of the modem day sewer system in most major North American cities has, to a large degree, followed a remarkably consistent path regardless of the city one examines.
Early sewers were designed to convey sanitary and storm wastes fiom residences and businesses directly into neighboring waterways while industrial operations typically discharged wastewater directly into the receiving environment. As early as 1850, sanitarians in major urban centers throughout North America claimed that wastewater discharged through faulty sewers, which ultimately produced stagnant ponds of filth, were the cause of significant heaith problems including choiera and typhus. Scientific evidence quickly confirmed this hypothesis and helped establish the medical profession as the primary proponents of an improved sanitation system. Concurrent with this social realization, engineers began to identi@ themselves as professionals, and soon asserted themselves as the appropriate managers of the much needed sewer infrastructure (Goldman 1997: 1 19). Disparities in wealth often resulted in inequitable access to sewer senices; relatively affïuent neighborhoods would ofien finance and install sewer pipes to remove their own liquid wastes, only to extend those same pipes into the backyards of their less affluent neighbors (Goldman 1997: 42). Construction of uncoordinated and isolated local sewer pipe networks across North America prompted some to cal1 for an integration of existing and future sewer infiastructure. Engiish sanitarian, Edwin Chadwick, described the inefficient and labyrinthian sewers of London by stating:
Were pins or machines made as sewers or roads are constructed, shah or pins would be made without reference to heads - in machines screws would be made without sockets and it may be confidently stated, there would not be a safe or perfect and well-working machine in the whole country. (Goldman 1997: 97)
Circumstances in major urban centers across the continent improved during the late 19Ih, and early 20* centuries, as old sewers were painstakingly integrated into more comprehensive sewer systerns. Rapid expansion of the economy and major metropolitan areas after World War II greatly increased water pollution, which attracted attention fiom a more aware public and spurred appropriate legislation (Gelg 1976: 3). By the 1950s, environrnental degradation resulting fkom untreated discharge of sanitary wastes into local watexways prompted rnany citizen groups of large uhan areas in North America to lobby politicians to develop special municipal agencies with overarching authority with respect to sewers. These agencies were responsible for the collection of wastewater fiom a number of local municipalities and cities, and its treatment in order to protect public health and improve overall environmental quality. Since the middle of the century, federal and provincial environmental legislation, as well as infrastructure subsidies, resulted in most wastewater utilities expanding service area boundaries to satisfL an increasing demand for sewerage services. Demand for sewerage services in urbanized areas has continued to grow over the second half of the century due to continuing health concems and increasing corporate liability for spills of industrial wastewater to the environment. Treatment Levels There exist varying categones of treatrnent within the domain of municipal wastewater treatment. Depending on the effluent quality desired, sewerage utilities can select either preliminary, primary, secondary, or tertiary treatment systems.
Preliminary In this mode of treatment, grit, and solid material are screened out before sewage receives Mertreatment or is released into the environment. Although a series of screens can provide fairly thorough removal of Iarger debris, prelirninary treatment is usually no more than a process which makes sewage effluent less offensive to the eye, without significantly reducing the level of suspended solids, biochemical oxygen demand, toxins, or bacteria. For example, Victoria uses only preliminary treatment before discharging its sewage into the ocean (Sierra Legal Defense Fund 1994: 36).
Primary Primary treatment invoives the removal of large solids and floating substances through settling and screening. This meth~dof treatment is usually defined as a physical process in which the sewage flow is slowed down and solids are separated tiom liquids. A large portion of the suspended solids settle naturally due to gravitation. The thicker part of the wastewater-the sludge-is then removed tiom the bottom and disposed of in a variety of ways. FIoatable solids, oil, and grease are usually skimmed off the surface and the clearer liquid is removed and discharged into the receiving erivironment. Settling tanks are cornrnonly used for the primary stage of sewage treatrnent. Lagoons-constnicted or naturally occurring holding ponds-also provide effective sedimentation conditions and, in some cases, meet secondary treatrnent standards. For smaller cities with the space necessary for lagoons, this is a popular method of sewage treatment. Conventional prirnary treatment generally removes 25 - 40% of the biochemical oxygen demand and 40 - 60% of the total suspended solids. With the aid of chemicals, sedimentation can be accelerated, reducing these two contaminants by about 50% and 90% respectively. Secondary Secondary treatment is a biological treatment process used to reduce suspended solids, biochemical oxygen demand, and some contaminants. Secondary treatment is the step following primary treatment. Also known as biological treatment, it Merreduces the arnount of solids by fostering the consumption of organic material by organisms in the wastewater. The fundamental process involved at the secondary level is biological oxidation. Ln this process, oxygen is provided to aid microorganisms to break down organic matter, considerably reducing the suspended solids and biological oxygen demand. Oxygen is a crucial component of this treatment stage. If oxygen is not supplied to the rnicroorganisms during the treatment process, dissolved oxygen in the water will be depleted as organic matenal breaks down after discharge to the receiving environment, and aquatic organisms will suffer. Because high oxygen dernand in sewage poses a serious threat to the aquatic environment, ihe degradation of organic material before discharge reduces the toxicity of the effluent.
If oxygen is not available when organic material begins to break down, anaerobic-non- oxygen requiring-processes of decay will produce compounds such as methane, hydrogen sulfide, and ammonia These substances are often produced in the forrn of gas, sometimes resulting in strong odors and toxicity to aquatic biota. Air-activated sludge and biological filters are just two of the many ways in which sewage can be exposed to biological processes.
Air-activated sludge is a treatment method whereby air is blown through the sewage, a process known as aeration, as it sits in a sedimentation tank. As a comrnunity of numerous types of microorganisms develops, the organic material is consumed and the clearer liquid is periodically decanted off and fiesh sewage allowed into the tank. As this process continues, and the settled sludge mixes with newer sewage, organisms build up and gradually a culture develops, capable of oxidizing organic material in the sewage within 4-8 hours. At this point the sludge is considered activated. After mixing and aeration, the sludge is transferred into a final settling tank where the clarified liquid is removed for discharge and the activated sludge is settled out and either removed for fùrther treatment and disposal or retwned to the first tank for re-use in the activation stage.
Biological filters are made up of layers of stones, gravel, and sand, and depend on biological processes sunilar to those of the activated sludge method. Organisms living on the surfaces of the rocks and stones break down the sewage as it flows through the layers. Although activated sludge usually achieves lower levels of suspended solids than biological filters and fbrther reduces biochemical oxygen demand, it does not remove as much ni trogen, nor does it have as large a range of organisms which work to break down organic material. The activated sludge method is less expensive and requires less space than filters, and so is generally more popular. Secondary treatment provides an 85-95% reduction in biochemical oxygen demand and suspended solids, and removes 90-99% of colifonn bactena (Sierra Legal Defense Fund 1994: 38).
Secondary treatment plants, however desirable from an effluent quality perspective, have some drawbacks associated with them. The secondary treatment process relies on the persistence of a population of bacteria for optimal performance. Disturbance of the environment in which the bacteria operate due to fluctuations in the pH of treatment plant influent, or the introduction of other toxic waste strearns, may result in system failure.
Tertiary Tertiary treatment is sirnilar to, but more thorough than, secondary treatment. It is generally used to reduce nutrient concentrations and Merreduce toxic contarninants. Tertiary treatment includes a variety of processes that are added to secondary treatment to respond to particular water quality problems. Substances such as nitrogen, phosphorous, and arnmonia may also be removed during tertiary treatment. The technologies used in tertiary treatment depend on the specific characteristics of the sewage. Microstrainers or sand filters can be used to fiirther remove suspended solids and reduce BOD. Other techniques can be used to remove nitrogen, phosphorus, and ammonia. Certain advanced forms of tertiary treatment can remove some metals, chemicals, and other types of contaminants. Treatment Process by-Products tiquid Effluent Among other components, the process of treating wastewater generates treated liquid effluent that is discharged into the receiving environment via the outfall of a treatment plant. It is vital that the quality of a plant's emuent be suitable for discharge into the local receiving waters. The quality and quantity of effluent is influenced by dimal, seasonal, and meteorological conditions.
Biosolids Biosolids are produced at wastewater treatment plants from the organic material removed during the sewage treatment process. There are a number of different processes to make biosolids. GVRD collects sewage sludge at wastewater treatment facilities, digests the sludge using biological and thermal processes, then dewaters it to produce biosolids for recycling. The digestion process takes place in mesophilic digesters where temperatures are maintained at approximately 90 to 105" Fahrenheit. Biosolids can be recycled as an organic fertilizer and soil amendment. Ninety-nine percent of al1 bacteria, pathogens, and viruses, are killed by the digestion process at the wastewater treatment plants. The GVRD's biosolids program, called utr ri for^, recycles al1 of the biosolids GVS&DD produces. Nutrifor biosolids are used to enhance tree growth, produce top soi1 for highway projects, fertilize farmland, reclaim mine waste rock piles and tailings ponds, recover old landfills, and prevent soil erosion in parks (GVRD 1999).
Methane The GVRD saves several hundred thousand dollars each year by recycling methane-rich gas from the wastewater treatment process to generate electncity at three of its five treatment plants (GVRD 1999).
Grit and Scum During the primary treatment stage, wastewater flows through grit removal and sedimentation tanks. In grit removal tanks, sand, cinders, and course grit are removed from the wastewater flow, washed, and hauled to an off-site landfill. This prevents the accumulation of deposits in piping, and unnecessq Wear of mechanical equipment in the succeeding processes. Scum, composed mainly of oil and grease, foms a floating layer in the sedimentation tanks. This material is skimmed off and sent directly to digesters for treatment.
Odors Biological breakdown of organic material can ofien generate fou1 odors if anaerobic conditions are aI1owed to persist. Vigorous aeration of wastewater during the treatment process helps mitigate odor problems. In cases where odors persist, air filters and scrubbers are employed.
Owing to its age-nearly 30 years-some key mechanical components of the Iona plant are due for replacement to maintain system reliability. A recent article in the Vancouver Sm reported on a senous mechanical failure at the Iona wastewater treatment plant. In the article the author wrote, ". . . barnyard smell down by the Fraser . . ." were blamed on "mechanical problems at the Iona sewage treatment site . . ." (Sarti 1998: B 1). In this situation, extreme odors were generated when one of the plant's six sludge digesters failed. A crack in the roof of the digester resulted in the discharge of partially digested sewage sludge into the outdoor aeration and settling lagoons. This, in tum, led to the release of strong and noxious odors to the atmosphere.
Principle Wastewater Components Wastewater quality is comrnonly assessed through mesures of two pollutants: biochemical oxygen demand and total suspended solids. Together, these two wastewater components give a reasonable characterization of the water body in question.
Total Suspended Solids (TSS) Suspended solids are particles of matter which float in the liquid wastewater. These solids, when present in significant arnounts, cmprevent sufficient sunlight from reaching underwater plant fife, greatly reducing growth and productivity. When algal growth is inhibited, for example, a food shortage cm develop for organisms higher up the food chain, upsetting the delicate balance of the entire ecosystem. Suspended solids in flowing waters cm cause abrasions on the gills of fish and exposed membranes of other aquatic organisms. These solids eventually settle on river, lake, or sea bed, srnothering bottom- dwelling organisms and creating oxygen-deficient conditions. Toxins found in sewage eMuent bind to sinking particles and make the bottom uninhabitable for many species of organisms that are typically found in that environment. Since suspended solids partial 1y consist of organic material, they contribute to an increase in the biochemical oxygen demand BOD of sewage effluent (Sierra Legal Defense Fund 1994: 33).
Because of the harmful impacts of excessive TSS in municipal effluent, the province regulates concentrations of fhis parameter by including specific limits in waste management permits issued to treatment plants. The concentration of total suspended solids is one of the principle measures used to evaluate the strength of wastewater and to determine the efficiency of treatment units.
Biochemical Oxygen Demand (BOD) Measures of biochemical oxygen demand provide a good estimate of the oxygen demand exerted on a receiving water body by a waste, and also gives an indication of the arnount of organic matenal in a waste which can be assimilated by oxygen consuming bacteria as food. BOD reduces available dissolved oxygen in receiving waterways, deprives organisms of an adequate oxygen supply, and generally impairs the aquatic environment.
Flow Effluent flow fiom the District's five WWTPs is regulated by the province. This is done, not so much from a hydraulic perspective, rather, from a contaminant loading perspective. Simply, too much flow containing signifiant concentrations of pollutants will create too much strain on the receiving water environment. In addition, managing flow is of vital importance to GVS&DD because of the major problems caused by flooding of sewerage facilities.
Sewer Development in GVRD The history of sewers in the greater Vancouver area does not differ greatly fiom the pattern described above. The first sewers were installed in the 1880's by the municipalities of Vancouver, Point Grey, South Vancouver, and Burnaby. As conduits to convey waste away from human settlements and into local waterways without treatment, these first sewers worked well. However a sense of municipal self dependence, and therefore autonomy, resulted in poor sewer system coordination between neighboring municipalities. It was not until 1914 that the sarne municipalities joined forces to plan for, and provide, centralized wastewater collection facilities, effectively marking the origination of the regional sewerage system. In order to accomplish this task, the Joint Sewerage and Drainage Board was created by an act of the provincial Legislature (GVRD 1993: 1). The sewer system master plan, drafled in 19 13, was implemented by the new board and served as the basis for management decisions until the early 1950's. Concerns over public and environmental health gave rise to a second and more comprehensive master sewer plan in 1953. The Rawn Repori, as this plan came to be hown, called for the treatment of wastewater and the establishment of two sewerage areas in the region; one comprised the North Shore and the other the Burrard Peninsula. Significant institutional changes were necessaxy to implement the recomrnendations. Provincial legislation that is still in effect today was passed in 1956, giving rise to the Greater Vancouver Seweruge and Drainage District Act (GVRD 1993: 2).
The Greater Vancouver Sewerage and Drainage District was established in accordance with the terms of the GVS&DD Act (1956). The district is responsible for the construction, maintenance, operation, and administration of the major sewerage and drainage facilities that together constitute the district's system. To execute these responsibilities, GVS&DD can borrow funds, write bylaws, resolutions and orders, and establish uses to which its facilities may be put and by whom they may be used. The sewer agency operated as an independent body until it joined the Greater Vancouver Regional District in 197 1. GVS&DD is currently responsible for providing sewerage services to its 18 member municipalities in a cost-effective and equitable manner while maintaining both environmental quality and WWTP effluent quality within perrnitted lirnits. An amendment to section 55 of the GVWAct in 1995 now provides a cost allocation mechanism based on flow, rather than on assessments, as was previously the case. Sewerage system expenditures incurred entirely within a municipality are paid for by the municipality. Similar expenditures that are incwred over an area that crosses municipal boundaries are apportioned on the basis of proportionate flow among the municipalities involved (GVS&DD 1997). The total area served by GVS&DD facilities is divided into five sewerage areas including the Vancouver Sewerage Area, North Shore Sewerage Area, Lulu Island West Sewerage Area, Fraser Sewerage Area, and the Northwest Langley Sewerage Area.
The Vancouver Sewerage Area (VSA) which comprises rnost of Vancouver, the University Endowment Lands, and parts of Burnaby and Richmond, with a population of about 480,000, is served by the Iona Island Wastewater Treatment Plant. The Lions Gate WWTP provides treatment for the North Shore Sewerage Area (NSSA) which is comprised of the District of West Vancouver, the City of North Vancouver, and the District of North Vancouver, with a population of about 160,000. The western portion of the City of Richmond, where most of the City's 120,000 residents live, comprises the Lulu Island West Sewerage Area (LIWSA). The Fraser Sewerage Area (FSA) covers an area with a sewered population of about 740,000, and includes most of Burnaby, New Westminster, Port Moody, Port Coquitlarn, Coquitlam, Pitt Meadows, Maple Ridge, Surrey, Delta, White Rock, the City of Langley, and the Township of Langley. Finally, the Northwest Langley Sewerage Ar~a(NWLSA) consists of the small Walnut Grove Region of Langley.
Municipal €muent and the Environment in the GVRD The inhabitants of the greater Vancouver area have long passed the point where their polluted water can be dispersed with no observable results. When untreated or inadequately treated sewage is dumped or overfiows into lakes, rivers, and the ocean, it contaminates fiagile ecosystems and cm cause disease or death for many species. Dissolved oxygen in the water column is depleted as a result of the biological activity involved in the breakdown of organic material by bacteria. The more organic material dumped into these waters, the more oxygen is consumed, and the less chance such environments have of recovenng after the discharge of po llutants is terminated. When the dissolved oxygen reaches very low levels, aquatic organisms die (Sierra Legal Defense Fund 199: 33).
Ultirnately, the cumulative impacts of discharged municipal wastewater on the environment exert a domino effect on the entire food chain. Some toxins accumulate in fish and other aquatic organisms. Wastewater pollutes surface water, and groundwater in some cases. As contamination spreads and vital food, water, and other naturai resources become increasingly toxic, humans too feel the impact of this ecological imbalance (Sierra Legal Defense Fund 1994: 32).
In addition to BOD and TSS, heavy metals and other persistent inorganic and organic toxins are found in municipal wastewater, such as: mercury, arsenic, lead, silver, oil, grease, and hydrocarbons. Some of these compounds can remain in the environment for a long time. Some heavy metals and organic compounds accumulate in organisms and are passed up the food chain to predator species. The concentration of toxins increases with each successive level of the food chah This process, known as biomagnification, is one way through which contaminants in sewage effluent can reach and affect humans. For instance, plankton eaten by a fish may carry a certain amount of mercury and, as the fish continues to eat plankton its level of mercury increases. By the time the fish is caught and consumed by a hwnan, its mercury level could be considerable.
Vancouver receiving water quality generally ranges nom 'fair' to 'poor'. 'Fair' water quality is described by GVRD as causing "occasional impairment of use" and 'poor' water quality is described as resulting in "consistent restrictions in water uses and documented biological impacts." Sewage emuent is acknowledged by GVRD to be a significant source of contarninants to this degraded receiving environment (Sierra Legal Defense Fund 1994: 9).
Wastewater Treatment Plants GVS&DDts five treatment plants treated 416 billion liters of sanitary sewage and storm water in 1995 (fig. 3). Prior to 196 1, when the first treatment plant-Lions Gate-was built, virtually no wastewater was treated before discharge into receiving waters. In 1992, primary treatment was rendered to more than 98 per cent of al1 wastewater generated in the region. The hvo per cent not treated at present is mdylost as a result of combined sewer overflows that occur during heavy rainstorms. The WWTPs differ in size and treatment process, discharge receiving environment, regulatory requirements, and the relative contributions of flow and loadings fiom the three principle customer groups, residential, commercial and institutional, and industrial.
With the exception of the Northwest Langley plant, which provides secondary treatment to plant influent, the region's wastewater historically received only primary treatment prior to discharge into the receiving waters. However, recent upgrades to the Lulu Island West and Annacis Island treatment plants means that these two plants will also provide secondary treatment by the end of 1999. The Lions Gate plant discharges into Burrard Inlet, the Iona Island plant into Georgia Strait, and Lulu, Northwest Langley and Arinacis plants discharge into the Fraser River.
The ongoing upgrades and expansions to the Lulu and Annacis wastewater treatment plants illustrate the effects of stringent environrnental legisiation, public pressure, and increased sewer demand in the region. These capital projects are needed to meet hture demand and effluent criteria and wiil cost close to $1 billion. Although the capacity expansions are forecast to satisfL demand into the next millennium, fiirther capacity increases at both of these plants are forecast by 2006. Upgrades to the remaining three wastewater treatment plants including: Lions Gate, lona Island, and Northwest Langley, are also included in GVS&DD Liquid Waste Management Plan (LWMP) (GVRD 1996: 10). All five wastewater treatment plants require upgrades to help minimize, or elirninate, current violations of regulatory conditions. lona Island Wastewater Treatrnent Plant The Iona Island wastewater treatment plant was put into service in 1963 to serve the Vancouver Sewerage Area, which includes the City of Vancouver, the University Endowment Lands, parts of Richmond including the Vancouver International Airport, and Burnaby (fig. 3). The sewerage area consists of some of the oldest sewers in the region, many of which are combhed sewers installed between 25 and 80 years ago. Originally designed to serve a collection system dominated by combined sewers, the Iona plant can accommodate wet weather flows up to five times the average dry weather flow, consequently, it consistently meets permitted effluent flow limits (GVRD L 996: 4 1). Plant treatment capacity was doubled in 1973 and expanded a mer30 per cent in 1982.
The sewer system tributary to the Iona Island WWTP is mainly an outdated design. Dunng dry weather al1 sanitary wastewater is transported to the plant by a nehivork of large interceptors and purnping stations; however, during wet weather, stormwater runoff overloads the cornbined sewer systern, causing overflows to Bumd Inlet and the North Arm of the Fraser River.
In 1988, $40 million in plant improvements were completed, including construction of an eight kilometer-long deep sea outfall, much of it built on, or under, the Iona Jetty. The jetty, extending five kilometers into the Strait of Georgia, is one of a number of multiuse facilities developed by the district.
Lions Gate Wastewater Treatment Plant Commissioned in 1960, the Lions Gate plant serves the North Shore Sewerage Area, which includes the City of North Vancouver, the District of North Vancouver, and the District of West Vancouver (fig. 3). Plant influent receives primary treatment prior to being discharged into Burrard Inlet via an outfall located under the Lions Gate Bridge. Owing to numerous hydraulic expansion projects, treatrnent capacity at the Lions Gate plant today is seven times greater than when it opened in 1961. Yet, wet weather flows, heavily influenced by inflow and infiltration throughout the collection system, frequently exceed the plant's hydraulic capacity and result in discharge of untreated wastewater to Burrard Inlet. Iindustrial operations in the North Shore Sewerage Area only contribute 3- 4% of total Lions Gate treatment plant influent flow and BOD and TSS loadings (table 3) Annacis Island Wastewater Treatment Plant Put into service in 1975, the Annacis plant's capacity was increased by 63 per cent in 1984 to serve 14 member municipalities and a total population of 800,000. However, by 2006, the Fraser Sewerage Area is expected to have a population of nearly one million. The Annacis Island WWTP is currently beuig upgraded to increase the treatment capacity to rneet future growth, and to provide secondary wastewater treatment to meet environmental standards. Predesign work for upgrading the plant to secondary treatment started in mid- 199 1. The secondary upgrades, scheduled to be completed by 1999, will not only improve emuent quality and the health of the lower Fraser River, into which the plant discharges, but also provide sufficient hydraulic and treatment capacity to serve increased population growth to 2006. Based on current population projections, the Annacis plant will require further expansion in 2006. However, the magnitude of the expansion work will depend on the possible diversion of wastewater f?om the Annacis plant to the Northwest Langley secondary plant (fig. 3).
Lulu Island West Wastewater Treatment Plant The City of Richmond is served by the Lulu Island West Wastewater Treaîment Plant (fig. 3). Located on the Main Arm of the Fraser River on the city's southern perimeter, the Lulu plant was put into service in 1973 and expanded in 1988 to provide treatment capacity for the 120,000 residents that live within the Lulu Island West Sewerage Area. Together with the Annacis wastewater treatment plant, the Lulu plant is currently undergoing an upgrade to secondary treatment capacity that is scheduled to be completed by 1999. The size and cost of the secondary treatment facilities at the Lulu and Annacis plants are based on current growth trends and flows in the sewerage areas to the year 2006 (GVRD 1996: 39). Figure 3 Map of GVS&DD Sewerage Areas and Facilities The Lulu plant is unique in the region as it serves an entirely separated sewer system where al1 of GVS&DD's intercepter sewers operate under pressure during peak flow conditions. In addition, al1 wastewater kom the City of Richmond's arterial sewers must pass through city pump stations prior to enûy into GVS&DD main lines. As a consequence, the collection system in Richmond is described as "self-lirniting", in that peak flows can not exceed the installed capacity of the pump stations (GVRD 1996: 53). As a consequence, when there is more sewage than the system can handle, it backs up in the city's system derthan GVS&DD's system.
Northwest Langley Wastewater Treatment Plant Within the Township of Langley are the 879 hectare Walnut Grove community, and the Northwest Langley wastewater treatment plant that serves the area. In 1996 GVS&DD assumed responsibility for capital projects related to upgrades at the treatment plant. Cost-benefit analyses are being conducted to detemine the feasibility of divcrting portions of Fraser Sewerage Area flow to the Langley plant in an effort to reduce stress on the Annacis Island treatment plant.
Regdations Liquid wastes from municipal sewerage facilities may be discharged directly to receiving waters. GVS&DD, as a discharger of liquid wastes, is regulated by both the provincial and federal govenunents. However, only the provincial government places restrictions, that it deems appropriate to protect the receiving environment, on municipal discharges via waste management permits. Environment Canada and the Department of Fisheries and Oceans are involved in the review process for discharges to anadromous fish bearkg waters, and navigable waters. In addition, the federal governrnent may take action under the Fisheries Act in the case of a discharge that is harmful to fish (GVRD 1988: 2-1).
Federal Acts The Fisheries Act was originally passed at the twn of the century and is Canada's strongest protection fiom water pollution. Section 36(3) provides for penalties of up to $1 million and/or imprisonment for every day 4'deleterious" substances are discharged into "waters Erequented by fish." Raw municipal sewage has repeatedly been found by the courts to constitute a "deleterious" substance. Ln fact, even effluent samples fiom secondary treatrnent plants occasionally fail the standard test accepted by the courts and the federal Department of Fisheries and Oceans @FO) as the appropnate test to determine the "deleterious" nature of an end-of-the-pipe sarnple. The Fisheries Act is enforced by the federal DFO, Environment Canada, and provincial Ministry of Environment.
Under Canada's constitution, the provinces have pnmary responsibility for natural resources and property matters; however, the federal govemment also has overlapping jurisdiction in relation to its power over "costal and inland fisheries". This joint jurisdiction has been informally divided in some provinces by special agreement, but the legal responsibilities of both levels of government remain. Although it is the federal DFO's prerogative and duty to enforce the Fisheries Act, it is a power that is used very rarely, and generally only then in the case of isolated spills rather than to deal with chronic offenders, In British Columbia, in the 15 years fiom 1977 to 1993, there were only three prosecutions filed by the federal government against municipalities for sewage eff'luent-despite the fact that the Greater Vancouver Regional District openly admits that it is in chronic violation of the act, and the fact that Victoria, Prince Rupert, and a number of smaller municipalities continually discharge untreated sewage into the ocean. The federal government seems to be attempting to grapple with its failure to enforce, and the widespread violation of, the Fisheries Act. In 1992, the federal Ministry of Environment prepared two reports dealing with enforcement policy in relation to municipal offences - Municipal Wastewater Deposits that. due to their Deleterious Nature, Violate Section 36(3) of the Fisheries Act and the Poiicy on Cornpliance and Enforcement of the Fisheries Act. To date, these reports have not been released to the public. Most provincial governments either take full responsibility for en forcing the Fisheries Act, or their duty in this area is concurrent with, but separate fiom, that of the federal govemment. Unfortunately, the provinces' collective prosecution record is no better than that of the federai government. For example, in BC, the provincial government has never charged a municipality for normal sewage discharges. There are two other federol statutes that contain sections pertaining to sewage discharges. The Canada Water Act entitles the govemment to designate any waters as a "water quality management area", and to then use extensive powers to maintain the quality of water in that area- This part of the Act has never been used. The Canadian Environmental Protection Act (CEPA) also has the potential to apply to municipal sewage. Part IV governs the dumping of waste into the ocean and requires that permits be obtained before sewage disposa1 takes place. This Act has not yet been explored with respect to municipal sewage (Sierra Legal Defense Fund 1994: 32).
Provincial Acts In 1982, the provincial government replaced the Polhfion Control Act (1 967) with the Waste Management Act (WMA). The province regulates GVS&DD's wastewater treatment works by issuing waste management permits, under WMA, for effluents fiom each of the district's plants. The pemits are issued by the BC Ministry of Environment and then held by the Greater Vancouver Sewerage and Drainage District. The value of benefits resulting fkom wastewater discharge limits contained in the permits include: improved human health and water quality; nonuse gains, such as current or future habitat use; and reduced interference at WWTPs.
GVSBDD Cornpliance with Waste Management Permits Al1 five of the region's treatment plants have violated permits on several occasions (Sierra Legal Defense Fund 1994: 8). Under WMA, the province has issued waste management permits to GVS&DD for each of the five wastewater treatment plants. Permits contain effluent limits for BOD, TSS, and flow, at al1 but one plant-the Annacis plant has additional limits for oil and grease, dissolved iron, and toxicity. GVS&DD is responsible for regularly monitoring plant effluents, and subsequently, reporting the resuIts to the province.
Plant effluent exceedances of BOD, TSS, and flow limits specified in provincial and federal pemits are shown in table 1. Table 1 GVS&DD Wastewater Treatment Plants: 1995 Record of Cornpliance* Wastewater Lulu hnacis Iona Northwest Treatment Island Lions Gate Island Island Langley Plant i West No No No No No Target Exceedances Exceedances Exceedances Exceedances Exceedances
Actual BOD Concentration %2 Wh 15h "/lu %7 Daily Load 2rn1132 '%32 NA '1132 NA TSS
Concentration Ohas 1h8S Olws '1- Daily Load %s "1385 NA "lks NA
Flow z'hs 1 1 "136s 1 '"hs 1 "l385 * Exceedances/number of tests Source: GVRD.Greater Vancouver Sewerage a: Drainage District. Sewerage and Drainage Department. 1996. Long Range Plan - 1997 - 2006. Burnaby, BC: GVRD. 10.
Chronic violations of waste management permits, threats from the federal government to prosecute under the Fislieries Act, and mounting public pressure ultimately forced GVS&DD to commit to secondary upgrades at the Lulu and Annacis plants. The decision to upgrade the two plants followed considerable discussion over the relative merits of secondary treatrnent, the lack of scientific data in support of the upgrades, and potentially larger benefits to be reaped fiom alternative management strategies. In 1994, GVS&DD stated officially that it would refuse to continue with secondary upgrade work at Annacis and Lulu WWTPs without federal fùnding and a guarantee of immunity fkom prosecution under the Fisheries Act (Sierra Legal Defense Fund 1994: 8). This approach to negotiations reflects the District's view stated in its Liquid Waste Management Plan: Stage 1 (1989):
. . . there are generally insufficient, suitable, environmental data to describe the nature, extent, and cause of environmental contamination and degradation within the region. A coordinated, comprehensive monitoring program is required throughout the region to determine the sources and relative significance of specific contaminants, and to provide a foundation for effective liquid waste management planning efforts. (GVS&DD 1996) GVS&DD recognizes that the emuent fiom its 5 WWPs constitute a significant portion of the contarninants which are found in local waterways, yet, the district remains unconvinced as to the exact magnitude of the impact on the environment, and actively lobbies senior govements to permit continued environmental monitoring studies before being forced to commit to Mercostly remediation initiatives.
Cost Drivers In large part, flow, biochemical oxygen demand, and total suspended solids determine operation and maintenance as well as capital costs for wastewater treatment plants. It is the responsibility of GVS&DD to ensure that BOD, TSS, and flow emuent limits contained in the provincial waste management permits approved for each of the district's five plants are met. Sizing treatment facilities depends, to a large degree, on the level of BOD and TSS removal which is required to meet the appropriate limits.
Maintaining satisfactory effluent quality is important. To accomplish this goal, managers must ensure sufficient treatrnent capacity and that adequate funds for upgrade and expansion projects necessary to meet effluent limits are available. In this way, BOD and TSS play a pivotal role in determining treatrnent costs. Similady, permitted flows and peak flows determine the required hydraulic capacity of a treatment plant, and consequently, influence the cost of facilities.
The estimated costs for each cost driver, by plant, are show in table 2 below. These costs Vary fiom year-to-year based on a variety of factors including: changes in total flows and loads, capacity expansions, and changes in fixed costs.
Table 2 GVS&DD Sewerage and Drainage Unit System Costs - 1996 WWTP Flow ($lm3) BOD ($/d) TSS ($lm3) Annacis 0.181 0.156 0.438 Lulu 0.1 13 O. 164 0.388 Lions Gate O. 129 0.130 0.41 2 Impacts of Municipal Effluent on the Environment Dumping raw sewage is technically illegal. Under the federal Fisheries Act, discharge of substances "deleterious to fish" into fish-bearing waters is a major offence punishable by fines of up to $1 million, and impnsonment- Many Canadian municipalities are chronic offenders. Yet charges are rarely laid. Such inaction is unfortunate seeing that in standard toxicity tests, sewage effluent from Vancouver and Victoria regularly killed al1 the test fish in minutes (Sierra Legal Defense Fund 1994: 3).
Twenty-one species of waterfowl breed in the Fraser River Basin (Canada 1993: 20). Municipal wastewater discharges contribute significant contaminant loadings to the Fraser Estuary. Over 90% of greater Vancouver's annual sewage discharges come fiom the Iona, Lulu and Annacis Wastewater Treatment Plants. The combined discharges fiom these three sources is enough to fil1 BC Place Stadium 160 tirnes, and amounts to roughly 30% of al1 wastewater that enters the Fraser River Estuary (Canada 1993: 95). Even though municipal discharges represent only 0.2% of the average flow of the Fraser River, during winter low flow conditions, the effluent can reside in the eshiary for up to 1.7 days with tides moving back and forth. Subsequent increases in the amount of time that wastewater discharges remain in the estuarine environment increase the likelihood that contaminants and heavy metals may become bound up in sediments or plants. In 1995, emuents fiom the Annacis and Lulu Island treatment plants were determined to be toxic to fish in more than half of the laboratory toxicity tests (GVRD 1996a: 10). Chinook salmon are particdarly susceptible to Fraser River Estuary water quality issues because juveniles spend up to one year in the estuary before going to sea (Canada 1993: 95). In an average year, 800-million juvenile salmon and steelhead migrate out of the Fraser Estuary and 10-million adults pass through on their way upstream to spawn. There are at least 87 species of fish and shellfish in the Lower Fraser. It supports the highest density of wintering waterfowl, shorebirds, and birds of prey in Canada. The Fraser River is the greatest producer of salmon of any river in the world (Canada 1993: 20).
In 1989, stage 1 of GVS&DD's Liquid Waste Management Pian reported that the environmental quality of 14 out of 21 receiving waterbodies in the greater Vancouver area was rated as being in either fair or poor condition. Treated emuent fiom District WWTPs as well as raw, untreated sewage continues to contribute to the problem. However, various improvements to the district's facilities have significantly reduced the quantity of contaminants discharged into local waterways (GVS&DD 1996). The decision to upgrade the two plants was motivated by significant public pressure and persistent violations of federal and provincial environmental regulations. It is believed that achievement of secondary treatment at the Annacis and Lulu plants will lead to great1y improved effluent quality, and therefore improved environmental quality along the lower Fraser River.
Regardless of system improvements, the volume of raw sewage discharged fiom GVS&DD system annually is sufficient to cover the City of Vancouver to a depth of 0.5 meters, or 2 feet, according to a report prepared by the Sierra Legal Defence Fund. This is equivalent to 62 billion liters per year, or 16% of total flow (Sierra Legal Defense Fund 1994: 9). GVS&DD estimates the voIurne of raw sewage discharged to be only 0.05% of total annual flows (GVS&DD 1996). Seven years later, in 1996, the waterbody ratings were the same.
Indus trial Wastewa ter During the Iast three decades, industrial effluents have grown more complex with the use of an increasing quantity and variety of potentially toxic materials in manufacturing processes. At the same time, an increased awareness of, and desire to prevent, detrimental impacts of direct industrial discharges to the receiving environment have resulted in many industries in urban areas comecting to municipal wastewater systems for disposa1 of their liquid wastes. Industry has corne to rely on municipal wastewater services as a cost effective method of waste disposal.
Treatment facilities in the Greater Vancouver Sewerage and Drainage District were designed to accommodate pnmarily domestic, or residential, wastewater which has relatively consistent average characteristics in terms of per capita flow and quality. However, in addition to residential wastewater, GVS&DD sewerage facilities also receive wastewater fkom commercial and institutional, and industrial customers. Unlike domestic wastewater, liquid waste fiom commercial and industrial operations cm Vary widely in quality and quantity, and often requires pretreatrnent prior to discharge to municipal and district sewers.
Wastewater discharged fiom the industrial sector in GVS&DD is quite diverse in its characteristics; the quantity, quality and even timing of discharges varies fkom one industrial sector to another, fiom one sewerage area to another, and fiom one Company to another. The entire GVS&DD generated an average of 1.Zbillion liters per day of wastewater in 1997; the industrial sector contributed 74 million liters per day (6%) to this regional total (GVRD 1998: 10).
Potential to Disrupt Treatment Process Industrial wastewater contains many chemical compounds, but the extensive list of contarninants can be reduced to include the principle contaminants of concern. These include: chemical oxygen demand, biochernical oxygen demand, total suspended solids, oil and grease, phenols, amrnonia, phosphorous, sulfate, cyanide, and trace elements. While al1 of these contaminants contributc to overall WWTP effluent toxicity, this study focuses on BOD and TSS.
Industry has the capacity to discharge about three times as much organic pollutants and twice as much suspended solids as an equal volume of municipal effluent (Gelg 1976: 5). Further, industrial operations have been identified as having the potential to "knock" the treatment process off balance by discharging occasional large volume, short-duration, or high-strength waste streams into the collection and treatment system. The impacts of such occurrences may include treatment plant effluent quality permit violations or environmental contamination due to temporary bypasses of wastewater treatment processes.
Secondary treatment is reliant upon the persistence of a healthy colony of bacteria for effective treatment. Industrial discharges of large volume and high strength waste have the potential to change the environmental conditions, upon which the bacteria rely, and ultimately cause the treatrnent process to fail. To guard against this situation, GVRD has identified source control as a key tool for achieving target contaminant concentrations in the influent to the new secondary treatment facilities. Recognizing the potential impacts that industriai discharges can have on plant operations, GVRD's Liquid Waste Management Plan states: '"ïarget contaminant concentrations for the influent will be set to pratect the secondary treatment process, maintain acceptable contaminant levels in sludge, and protect the receiving water environment" (GVRD 1996: 39). Risks fiom residential and commercial and institutional wastewater on secondary treatment processes are not considered as great as those fiom industrial wastewater.
In April 1998 a failure in one of the digesters at the Iona Island WWTP resulted in partially treated sludge being pumped into sewage settling ponds. The problem arose after a vent in the roof of one of the six digesters was broken due to a build-up in grease. Without the vent operating properly, the ability to control the environmental conditions within the digester was lost. Organics in the sewage sludge are normally 'broken down' and neutralized by bactena which grow and persist in the digesters. However, the bacterial colonies are susceptible to oscillations in environmental conditions. When the vent rnalfunctioned and changed those conditions, the bacteria were wiped out. Although this digester failure was due to excessive grease build-up in one of the digesters, it demonstrates quite clearly the impact that an 'upset' digester cm have on human health and system operations. Industrial discharges, often characterized as "high-strength" and "high-volume" have the potential to disrupt the environmental conditions that the bacteria, and thus the treatment process, rely upon (Sarti 1998: B 1).
Industriai Flow and Loadings in GVS&DD The contribution of industrial wastewater to total influent flow and Ioadings at the region's five wastewater treatment plants varies as seen in tabie 3 and figure 4. It can be seen that although industrial flow often contributes a relatively small percentage to total plant influent, BOD and TSS concentrations in the wastewater cm result in disproportionate daily industial loadings of these contaminants. This is illustrated by data in table 3 that show daily industrial loadings of BOD to the Iona Island WWTF in 1997 to be 33% of total plant influent loadings, and industrial flow to the same plant as only 4% of total influent flow. The BOD concentration of industrial wastewater is greater than the concentration in residential and commercial and institutional wastewater (GVRD 1998: 9). In the case of the Iona Island WWTP, the low voIume, high BOD strength industrial wastewater, results in industry effectively laying claim to a significant arnount of the Iona Island WWTP's available BOD treabnent capacity. Currently, the aggregated flows and loadings fiom permitted industrial operations comprise approximately 80% of al1 industrial flows and loadings in the GVS&DD.
Table 3 GVS&DD 1997 Wastewater Treatmeot Plant Industrial Flow and Loadings Annacis Lulu Island Narthrest Iona Island Lions Gate Wnf 1 1 / 1 Langley 1 1 I I 1
* - - . ~kr(l~dfday) Industrial Discharge 21.183 42.702 4.172 4.533 1.488 587 439 110 66.9 8.17 WWTP - Total Influent 1 1 1 Oh of Influent (1997) 4 1 O 4 7 18 1996 4 Il 4 7 16 1995 4 11 4 8 20 1994 4 13 3 3 20 BOD (tonsidry) Industrial Discharge 21.103 19.442 0.367 1.969 0.5 WWTP - Total Influent 63.08 76 13.78 12.86 2.43 % of Influent (1997) 33 26 3 15 2 1 1996 35 3 1 3 17 20 1995 32 28 4 19 3 3 1994 26 34 3 2 1 51 TSS (toddry) - Industrial Discharge 7.18 7.732 0.483 1.72 1 0.237 WWïP - Total Influent 62.33 72.78 16.5 1 1.58 2.74 % of Influent (1997) 12 11 3 15 9 1996 20 15 2 7 6 1995 18 15 3 6 20 Figure 4 Indushial Contributions to WWTP Influent Flow and Loadings (1997)
Iona Island WTP gX,
Annacis Island WTP
800
Lions Gate WWTP Bo0 TSS 3%
Island West WWTP 100 TSS 13%
Northwest Langiey WWTP
Fbw BO0 TSS
8%
1 ndustrîal Wastewater by WWTP Each of the five UrWTPs in the district is impacted by a unique set of industrial operations (table 9). The two top ranked industry sectors, with respect to the size of their contributions to total industrial flow and loadings at each WWTP are shown in table 4. Di fferences in the composition of industry subsectors that impact each treatment plant mean that wastewater management strategies for a specific plant often need be tailored to satisfactonly accommodate flows and BOD and TSS loadings which industry discharges to sewer.
Table 4 GVS&DD TopRanked Industry Sectors for Discharges to WWTPs
1 WWTPlSewerage Are. 1 Diily Flow ( Daily BOD Loadiag T Ddly TSS Loading 1. LandfiIl 1. Brewerïes 2. Papcr (exccpt newsprint) 2. Dairy & Milk Producrs ~~~~~j~ Island/FS~ MilIs Wholesaie-Distributors
1 1 1. Soft Drink & Icc 11. SoftDrink&Icc 1 1. Safood Product Manufactunng Manufacturing Prepantion & Lu'u Island Watl 2. Sofituood Vmem ,& 2. AIlOthcrFood Pachging LIWSA Plywood Mills Manufacturing 2. AIIOtherFood Manufacturing 1. Landfills 1. Marine Cargo Handling 1. Manne Cargo Handling Lions Gate/NSSA 2. Manne Cargo Handling 2. Landfills 2. Landfills
1. Fruit & Vcgetablc 1- PoultryProccssing 1. Poultry Pnxessing Canning. Pickling & Northwest Langleyl 2. Fruit & VegeLable 2. Fmit&Vegetabk Wing Canning. Pickling & Canning. Pickling & NWL 2. Poultry Processing Dm% Dviw
1. Brewmies 1 Fat & Oil Rtfining & 1. Fat & Oil Refining & Blending Blending Iona IslandNSA 2. Pemleum Refineries 2. Breweries 2. Brewenes
Environmental Regulations and Enforcement Many municipalities' bylaws are outdated and do not effectively limit the kinds of contaminants found in today's municipal sewerage systems. However, lax enforcement of bylaws and regulations is an even greater obstacle to effective source control than ineffective legislation. Prosecution of offenders is generally seen as a last resort. Municipal or district authorities prefer to negotiate with an offender and to arrive at an agreement to upgrade pretreatment facilities, rather than file charges or levy fines. However, many operators tend to postpone improvements while continuing to violate regulations and discharge waste which cannot be adequately treated at a municipal plant. Strict enforcement of pennits would motivate industrial operators to meet these standards quickly. In order to enforce source control regulations, an extensive monitoring program must be in place. Many municipalities lack the staff to perfonn tests to ensure that standards are being met, and monitoring is ofien conducted only in response to a cornplaint. Insufficient resources to support thorough monitoring at the municipal, provincial, and federal levels of goverment will lead to more violations. Left unchecked, offenders will continue to pollute the environment without penalty (Sierra Legal Defense Fund 1994: 32).
Contrary to this rather bleak view of industrial en forcement, there is evidence of an increasing willingness by US courts to hold Company officials liable for illegal wastewater discharges to municipal sewerage facilities. William Williamson, foreman of the City of New Haven, Connecticut, Signs and Markings Division, was charged with ordering city employees to dump highly flammable solvents and paint waste into a collection system in 1995. If found guilty, Williamson faces a maximum prison sentence of up to 6 years for Clean Water Act violations. Also, the owner of River City Plating in San Antonio, Texas, his son, and an employee were found guilty of discharging waste metals into the city collection system fiom 1988 to 1994. Each faces up to 3 years of imprisonment and up to $250,000 in fines (WEF 1996: 10)
On September 8, 1997, the US District Court of the Southern District of Texas (Houston) sentenced Attique Ahmad, former owner of the Conroe, Texas, Spin-N-Market gasoline station, to 1 year in prison and ordered him to pay more than $27,000 in cleanup costs. Ahmad had pleaded guilty to pumping 17.7 m3 of gasoline fiom a leaking underground storage tank into the Storm and sewer system on Jan. 25, 1994. Gasoline in the sewer system could have caused an explosion so children fiom two nearby schools were evacuated. The dumping shut down the Conroe WWTP and contarninated Possum Creek, a tributary to Houston's major drinking water source (Wallace 1997).
Also, a manufacturer that discharged radioactive material to a Cleveland, Ohio, WWTP was ordered to pay a $250,000 lump sum fine and a further $1 million in 36 monthly installments. The discharge polluted solids during treatment, and caused three lagoons that stored incinerated biosolids ash to become radioactive, and subsequently interfered with biosolids disposa1 (Wallace 1997: 16). Although not a sewer-related prosecution, a recent successfül prosecution of Money's Mushrooms in Langley for violation of the GVRD's Air Quality Bylaw supports the claim that environmental regulations in the Lower Mainland, ofien considered ineffective, are maturing and gaining force. Moneyts Mushroorns, found guilty in provincial court of causing air pollution as a result of excessive odors from its composting operation in Surrey, was fined $100,000, under the Greater Vancouver Regional District's Air Quality Bylaw. In addition, GVRD and Money's have agreed that Money's will not appeal the conviction or sentence. The success of this local air quality bylaw in court will likely pave the way for similar prosecutions under GVS&DD's Sewer Use Bylaw (GVRD 1998a).
Source Control One of the strategies employed by local govemments to regulate discharges to the sewer, and prevent illegal discharges like those described above, is to establish a Source Control program. Source control involves the regdation or elimination of substances entering a municipal sewerage system, and is a vital component of any treatment and disposa1 process. By restricting the type and volume of material discharged into the wastewater flow, source control programs hction as an alternative to the conventional practice of removing or treating pollutants at the 'end of pipe'. This preventative approach to waste management is more effective and considerably less expensive than attempts to rehabilitate polluted ecosystems. Effective source control reduces the overall wastewater flow, conserving water and energy. With smaller volumes to process, sewerage systems can work more efficiently. If persistent toxins were prevented fiom entering the sewage flow, the characteristics of wastewater and the type of treatment required would change drarnatically. The effiuent discharged into the environment would be significantly less toxic; and the sludge, which would no longer contain high levels of untreatable substances, would become a usehl resource. In this form, sludge can be used as a soi1 conditioner on fields, as landfill for projects such as mine reclamation, composted and sold as fertilizer for smaller gardens, or applied in reforestation projects (Sierra Legal Defense Fund 1994: 44). GVS&DD's Source Control Division was created in 1990 to adrninister Sewer Use Bylaw No. 164, and develop and manage the source control program as part of the sewerage and drainage senices provided by the district to its member municipalities. The program's primary goal is to regulate and control waste discharges to the District's sewerage and drainage system, at source. Administratively, control of nondomestic waste is accomplished through issue, administration, and enforcement of authorizations, permits, and codes of practice. Controlling discharges at source is key to prevention of high contaminant levels in the sewerage and drainage works which could compromise worker safety and health, interfere with the operation of the collection system and treatment works, or pass through the system into the environment without adequate treatment.
With respect to the allocation of resources dedicated to regulating the three wastewater customer groups, GVS&DD's Source Control Division expends 72% of available regulatory resources on industrial users, 21% on commercial and institutional users, and 7% on residential users (GVRD 1998b: 13). The high level of attention the industrial sector receives, relative to its minor contribution to overall regional fl~w(6%), suggests the degree to which discharges fiom this sector can impact regional sewerage facilities, and hence the significance of this sector with respect to overall management of GVS&DD sewerage system.
GVS&DD Sewer Use Bylaw No. 164 In 1990, Sewer Use Bylaw No. 164 was adopted by GVS&DD, providing the regulatory basis to control nondomestic discharges to the district's sewerage and drainage system. Under the bylaw, the district is empowered to impose requirements on the direct or indirect discharge of nondomestic waste to district facilities. Control of nondomestic waste can take the form of prohibition of certain types of waste, restrictions on contaminant concentrations, reductions in contaminant loadings, and allocations of discharge volumes. The bylaw is adrninistered by the district's Source Control Division, except within the City of Vancouver boundaries, where City of Vancouver staff handle this task.
GVSCLDD Waste Discharge Pennits GVS&DD Source Control activities are founded in law and receive authorization fiom the GVS&iDD Act, the Waste Management Act, and Sewer Use Bylaw No. 164. Under the bylaw, discharge pennits are required for: nondomestic waste discharges over 300 m3 in any 30 consecutive day period; restricted waste-waste which exceeds a defined set of concentration limits; and trucked waste-waste that is hauled to the treatment plant by truck-such as septic tank and grease trap contents. Not al1 industrial operations in GVS&DD are pennitted, and therefore are not monitored by the Sewerage and Drainage Department's Source Control Division (GVRD 1997a). Operations that are pennitted are required to submit wastewater monitoring data on a regular basis-usually monthly.
Permit Corn pliance From 1990 to 1995 the primary focus of the source control program was the implementation of the waste discharge permit system and the development of administrative procedures for cornpliance monitoring and enforcement. During 1994 and early 1995 an enforcement strategy was developed. The strategy is intended to improve compliance performance by industrial permit holders, by way of a fair, consistent, and reasonable approach. A key component of the strategy is the Source Control Non- Compliance List, which is intended to serve as a strong deterrent to noncompliance, and encourage industries using the district's sewerage works to proactively manage their discharges in accordance with the terms and conditions of their permits. The Non- Compliance List is published twice per year, in April- Generally, rnost companies whose operations are govemed by sewer permits administered by the district remain in cornpliance with permit regdations (GVRD 1998). However, GVS&DD believes that inclusion on the noncompliance list sends a clear message to industries that they must, at al1 times, proactively manage their discharges to maintain compliance, ratfier than wait for enforcement in response to violations. The October 1988 noncornpliance list contained the narnes of eight companies. Six of those were ordered to commit to compliance programs, one failed to complete a compliance program, and another was ordered to cease discharge of a waste Stream that posed a serious safety risk to sewer workers. The noncornpliant operations included food processing, poultry processing, meatpacking, lead srnelting, and chemical production companies (GVRD 1998). Ail of these operations contribute either one or al1 of the parameters of concern in this study: BOD, TSS, and flow. Sewer violations include unlawful discharges of poilutants such as oil, grease, acids, solids, and heavy metals into local sewer pipes. Excessive amounts of these waste products pose health hazards to sewer workers, affect treatment plant operations, and threaten the environmentai quality of local waters where treated sewage is discharged. Companies that do not achieve and maintain compliance with the conditions of their sewer discharge permits are subject to a range of escalating actions. Those actions can include denial of a waste discharge petmit, an order to stop discharging, or ultimately legal action that can result in fines of up to $10,000 per day. As a deterrent to those tempted to discharge wastewater unlawfülly into the district's sewers, Sewer Use Bylaw No. 164 provides for a daily fine not exceeding $10,000 for each day an offence occurs. The Sewage Treatment Review Panel flagged this section of the bylaw stating: A source control bylaw under Section l8(2) of the Waste Management Act may provide for a fine not exceeding $1 0,000. The Savage Treatment Review Panel suggests GVRD request the Crown provincial to arnend this provision to provide for greater fines. This is because courts on prosecutions seldorn assess the maximum fine and so a fine of, Say, $2,000 may be tantamount to a license to discharge with equanimity. (Lidstone et al. 1993: 16) Indus trial Wastewatec Special Issues Impacts on Sewer Operations Of crucial significance to the evolution of wastewater management has been the changing functionality of the sewerage system. The change in customer mix fiom predominantly residential to a larger group of users including commercial and institutional, and industrial operations is clear. Due to the high cost and practical difficulty of replacing old sewerage facilities to adequately acconunodate the demands of the new customer mix, original pipes and treatment facilities that were designed only for sanitary waste, now receive waste flows and contaminants for which they were not originally intended. The inclusion of high-strength wastes fiom the commercial and industrial sectors in the sanitary sewer system force utilities to increase their peak conveyance and treatment capacity beyond that level typically required by an equivalent residential population. As a consequence, per capita sewerage system costs have risen disproportionately. Also, in urban centers across North America, use of older sewerage facilities for purposes other than that for which they were designed, coupled with age-related failures, has led to increased surface inflow and groundwater infiltration through cracks in pipes and joints. This, in turn, has merstressed facilities and led to an increase in the frequency in the number of uncontrolled spills to the environment. Changes in Industrial Sewer Demand To the extent that different urban areas contain different mixes of manufacturing industry, total industrial demand for sewerage system capacity can vary greatly among different cities. Industrial water use has changed considerably in the past 25 years; it has fallen quite drarnatically, not just relative to the volume of output or employment but also in absolute terms. In California, for example, industrial fieshwater intzke fell fiom 1.33 million acre-feet in 1973 to 0.86 million acre-feet in 1983 despite the growth in the California economy during that decade. The evidence suggests that the downward trend in industrial water use has continued, albeit at a slower rate. While higher water prices and changing manufacturing technology played some role, the main reason for the decline in industrial water use was water pollution control regulation by federal and state govements since the early 1970s, which has greatly encouraged manufacturing fims to recycle water and reduce their wastewater discharges. This fact illustrates the idea that planners and anaiysts treat water supply and wastewater disposa1 as separate items because they are often administered by separate agencies. However, this overlooks the economic linkages between them which arise because intake water supply and wastewater disposa1 both generate water use costs for industry. They may involve different technological choices, but those choices are interdependent; the costs of water supply are likely to affect decisions on wastewater disposal, just as the cost of wastewater disposa1 is likely to affect decisions on water intake and use (Baumann et al. 1997: 34). In 1981,47% of total provinciai industrial output was accounted for by industrial operations in the Greater Vancouver Regional District (GVRD 1988: 3-1). Although the current vaIue of this statistic is not lcnown precisely, the fact remains that the greater Vancouver area continues to be home to a significant industrial community. With respect to industrial wastewater, a large proportion of industrial liquid waste is produced by a small number of firms, and thus these firms exert disproportionate pressure on public sewerage resources (GVRD 1988: 4-2). Yet, the firms contributing the most wastewater to the sewerage system are, in many cases, also the largest employers in the region. Wastewater Limits The pnnciple objective of GVS&DD's source control program is to regulate wastewater discharges fiom al1 sewer user groups so as to prevent harmful impacts that these discharges might have on sewerage works, the wastewater treatment process, and the receiving environment. Invariably, achieving this objective requires that quality and quantity limits be placed on wastewater discharges; and that limits be placed on industrial discharges, in particular, owing to this sector's capacity to impact normal sewerage operations. A successfùl source control program is one that consistently achieves its wastewater quality and quantity control objective, while providing industries with a viable waste disposal service consistent with local govemment policy. Concentration limits applied to industrial wastewater discharged to sanitary sewer are included in waste discharge permits issued by GVS&DD. In general, the limits are consistent with the concentrations used to define restricted waste in the regional sewer use bylaw. Limits imposed on the wastewater quality and quantity fiom industrial operations ofien impact their financial viability. Consequently, industry groups ofien question the validity and rationality of sewer discharge limits. Many industry groups in GVS&DD seek site- specific and situation-specific limits, yet at the same time, state their unwillingness to provide additional fùnding for the regional staff required to determine these tailored limits (GVRD 199%: 8). The president of the National Academy of Engineering in the US, Robert White, stated, Cornpliance with environmental laws and regulations can add significant costs to the production of goods and senices as it protects environmental values. The cost of US environmental regulation was $1 15 billion in 199 1 and is currently thought to be closer to $170 billion. What if a Company has incurred cornpliance costs to satis@ regulations that tum out to have beeri unwarranted because they were based on inadequate or incorrect scientific information? (Josephson 1993 : 778) In a survey of 800 US Chamber of Commerce members, a majority of respondents said that instead of issuing environmental regulations across the board without first seeking adequate input frorn stakeholders, they wished the governrnent would tailor regulations to specific industries. Ninety-one percent of the survey respondents said that federal agencies should be required to use risk assessments to develop environment, health, and safety regulations. They also said that compliance through enforcement should be replaced by compliance through assistance and industry self-policing (WEF 1996: 34). This view is fiequently echoed by industries operating within GVS&DD. Unfortunately, the use of risk assessments to develop environment and health regulations does not guarantee valid and rational limits. Like highway speed limits, where absolute and defensible limits for dllocations and conditions exist, there is an understanding that in the absence perfect knowledge, a carehlly considered and reasonably cautious wastewater limit will suffice. In order to meet more stringent regulations, industry ofien invests in "end-of-pipe" or "black-box" technologies to treat wastewater. This approach is contrary to the view that in the long run, assuming no change in product mix, the least costly method of reducing water pollution is by the introduction of new capital equipment. Further, new production facilities typically cause less water pollution than old equiprnent, and end-of-pipe treatment of wastewater is usually more costly than changes to capital equipment (Gelg 1976: 11). Faced with more stringent limits on wastewater quality, GVS&DD industry express concem over: the "hi& cost of doing business in the region", local industry's inability to compete globally, and the possibility of significant job losses in the sector (GVRD 1997b: 5). Industry representatives on GVS&DD's Technical Working Group stated that between 1992 and 1996,4,900 jobs were lost. However, during the same period there was a net increase of 101,300 jobs in the GVRD, thereby suggesting that overall, industry is not fleeing the region as suggested ( GVRD 199%: 7). If a goal of the community or the region is to encourage industrial expansion, then the provision of wastewater treatment services without restrictive discharge limits could be seen as vital for healthy economic development. The debate, then, focuses on the degree to which a community ought to risk environmental degradation in the narne of jobs. Industrial Flexibifity and Innovation By virtue of the fact that industry has more alternatives to central treatment than residential and commercial customers, they have the ability to adapt and change their processes to minimize costs. Stringent regulations are often precursors to innovation in the industrial sector. This is due, in part, to the fact that abatement efforts, whether in the form of process change, water reuse, or water treatment, often result in savings that at least partially offset the cost of abatement. For example, efforts to reduce water use and contamination of wastewater usually also conserve energy and matenals. It is a basic econornic fact that industry witl seek the least costly method of achieving abatement (Gelg 1976: 9). "Historically, industry tends to be quite innovative in finding ways to comply with environmental regulations that are less expensive and less burdensome than those suggested by regulators" (Denning 1998). Another example of industrial innovation occurred in Shakapee, Minnesota, in 1994. The Rahr Malting Company wanted to build a plant to treat wastewater fkom its expanded malt production facilities. A permit to discharge to the Minnesota River was denied because the available point-source loading had previously been allocated to regional WWTPs. Fearing the compounded impacts fiom Rahr's carbonaceous BOD loadings and the loadings fiom future commercial, residential, and industrial growth in the region, the Minnesota Pollution Control Agency decided to ailow for growth in the latter only. In order to continue with plant expansions, the Company successfiilly negotiated with the agency to employ tradable effluent permits to solve this problem. Rahr purchased tradable effluent credits from other dischargers in order to ensure a loading-neutral outcome (Wallace 1997: 18). This type of solution is made possible by industry's ability to "choose" when, where, and how to discharge waste, a luxury not generally afiorded to the residential and commercial sectors. in addition, evaluation of the merits of this solution could be greatly enhanced by an industrial sewer demand simulation model. Summary Industrial wastewater discharges impact significantly upon GVS&DD treatment facilities. lndustry continues to want access to GVS&DD sewer services in response to increasingly stringent regulations imposed on discharges to local watenvays. However, by virtue of the quantity and quality of industrial wastewater, district infrastructure and treatment processes remain at risk without aggressive source control measures. Rather than simply responding to an endless growth in industrial sewer demand, GVS&DD will benefit from the ability to manage this demand through the use of tools that will assess the impacts of new demand on district facilities. In this way, treatment plant, and pipe capacity, along with environmental quality, can be factored into strategies for managing industrial demand for sewer services. Evidence shows that the industrial sector is capable of adapting to new management strategies; specifically, to those strategies that enhance the operation of district facilities and improve environmental quality. Such gains can be made in part through utilization of the industrial sewer demand model. Chapter 3 - Sewer Planning and Demand Forecasting Planning Overview Traditional sewer supply planning emphasizes the goals of minimizing prices and maintaining system reliability, while assuming that demand is a "given" that cannot be altered by a utility. Oriented toward a wastewater utiIity's financial planning process, this fonn of planning assumes a very high Ievel of reliability, avoidance of nsk, and utility ownership of al1 facilities. The final plan ofien recornmends construction of a large-scale wastewater treatment facility. It has been shown that construction of oversized treatrnent plants tends to "direct'' growth, rather than respond to itt resulting in uncontrolled urban sprawl (Arnold 1979: 184). Due to the fact that such planning is conducted internally by utility planners, managers and politicians, the public-at-large, outside experts, and govemment regulators ofien have little or no involvement in the planning process. Consequently, the resulting plan tends to be narrowly focused and exclusionary. Since the late 1970s, traditional supply planning has proven to be an ineffective process for some utilities. It is particularly unresponsive to the environmental, financial, and political constraints of the 1980s and 1990s; the large construction projects which are often recommended have encountered significant public opposition (Baumann et al. 1997: 19). It also ignores the important contribution to supply that can be obtained fiom comprehensive demand-side management programs. These can include water conservation programs, technology subsidization programs, user fees, public education, and incentives for water reuse and recirculation. GVRD commenced a comprehensive regional planning initiative in 1990 which begun to address some of the shortcomir,gs of the historical approach to sewer utility management. The Livable Region Strategic Plan and was the result of the initiative. Planning in the GVS&DD GVRD Livable Region Strategic Plan The Greater Vancouver Regional District, committed to the Creating Our Future vision and a stated desire to create a healthy and sustainable region, has developed a strategic plan entitled the Livable Region Strategic Plan (LRSP). Completed and approved in 1996, the plan was developed in response to public concem over uncoordinated urban sprawl and its associated problems including: the threat to farmland and other green spaces, increased pollution, greater distances between jobs and homes, and the unnecessarily high costs of supplying public senices and utilities (GVRD 1996b). Four strategic policies comprise the core of LRSP including: protection of the green zone; building of complete communities; achievement of a compact metropolitan region; and an increase in transportation choices. The strategic plan calls for a larger share of residential growth to be accornrnodated in the Burrard Peninsula municipalities, the North East Sector, North Surrey, and North Delta. Concentrating growth in these areas will allow more people to tive closer to their jobs, and will make better use of public transit and comrnunity services. Cornmunities in the central and eastem Fraser Valley will continue to grow, but at a slower pace. Fraser Valley communities will also be more complete, with a balance between job and residential gowth. The objectives and policies included in the plan strongly influence regional growth patterns which in tum influence the operation and management of sewerage facilities. Further, the industrial sector responds to regional and municipal planning objectives, tending to establish operations in financialiy strategic locations. Men large industrial enterprises either move between GVS&DD sewerage areas, or migrate into sewerage areas from outside the district, in pursuit of favorabIe business environments, impacts on treatrnent plants can be significant. Such large-scale movements often occur with little waming. Sewerage system planners and managers are left scrambling to decide on a strategy to accommodate the increased industrial flow and loadings. Historically, growth in the region was uncoordinated-each municipality secured its own autonomous growth strategy-meaning that GVS&DD spent much of its time responding in a haphazard manner to municipal requests for sewerage services, rather than playing a coordinating role. As a result, GVS&DD was prevented fiom achieving system efficiencies normally attainable by a regional utility. Today, GVRD has greater powers to direct land use patterns as a result of a 1996 amendment to the BC Municipal Act. Official Community Plans: Context Statements In accordance with the terms of the BC Municipal Act, the minister of municipal affairs and housing confirmed GVRD's Livable Regional Strategic Pian as a regional growth strategy in February 1996 (GVRD 1997~).It sets out region-wide targets for the accommodation of households, population, and employment growth. The aim is to manage the region's growth through sustainable land use and transportation development. In addition, recognition of the plan as a regional growth strategy brought about a number of important changes to the manner in which regional planning has traditionally been conducted. In 1996, the Growth Strategies Act established a regional focus to local land- use patterns, and gave GVRD greater power in this regard. Al1 20 municipalities within the district must submit regional context statements to GVRD for approval. The statements must explain how officia1 comrnu~typlans (OCPs) for the next two decades fit into the overall Livable Region Strafegic Plan (Munro 1998: Al). Fwther, the regional context statements must show how the municipality will contribute to achievement of the plan's objectives (GVRD 1997~).The regional context statements have since been received by the GVRD Board. The Strategic Planning Department has reviewed the statements and is now confident that al1 member municipality officia1 cornrnunity plans are consistent with the objectives of the Livable Region Strategic Han (Perkins 1998). The LRSP contains current estimates of municipal growth capacities. It is the GVRD Board's intention that, as comrnunity plans are reviewed and updated, the municipal growth capacities will change to support realization of the region-wide targets. According to the LRSP, the region will see emphasis placed upon the development of five regional town centers, thirteen municipal centers throughout GVRD, and improved transit comdors between the centers. In effect, the town and municipal centers will exist like islands within a sea of green zones and agricultural lands. In addition, a more densely populated Grorvth Concentration Area (GCA),defined as that area including the Burrard Peninsula municipalities, the North East Sector municipalities, North Surrey and North Delta, will develop, thereby helping to minimize urban sprawl through valuable agricultural land in the eastem municipalities. This pattern of growth is subsequently expected to effect levels of employment within sewerage areas within GVS&DD (fig. 5). As the population of the region increases, a greater percentage of people will work in the GCA. Figure 5 Trends in Percentage of Total Regional Employment Contained Within GVS&DD Sewerage Areas: 1991 - 2021 -- - -- Change in Municipal Employment am Percent of Total Regional Employrnent (1991 - 2021) : fEstlrnater & Forocarts -- Fraser Sewerage Area 3001 -- -C Vanmuver Sewerage Area Lulu Island West Sewerage Area 20% -- North Shore Sewerage Area 1985 1990 1995 2000 2005 2010 2015 2020 2025 Year The alternative, "business as usual" growth scenario will result in increased urban sprawl throughout the Fraser Valley. Maintaining autonomous municipal planning authority would result in continued urban sprawl in the eastern municipalities. Providing sewer services to each municipaiity according to its particular preferences, rather than in accordance with the requirements of the population in the entire region, poses many problems for GVS&DD. Planning for the level and location of future sewer demand by a regional service provider, such as GVS&DD, is fiustrated when its pnmary custorners- the municipalities-are not required to coordinate their planning objectives. Now that GVRD municipalities are required to dovetail OCPs with GVRD's Livable Region Strategic Plan, this problem is largely mitigated. Also, with respect to regional growth strategies, GVRD is now required to provide works and services in a manner consistent with achievement of the strategic plan. These changes in procedure are especialIy important with respect to industrial land use planning. The ability and propensity of industry to move around the region in response to changing land values or econornic conditions threatens to impact significantly on industrial wastewater management objectives. A single industrial discharger can have an impact on treatment plant operations equivalent to that of a small residential subdivision. Therefore, if a major operation moved from one sewerage area to another without notice, treatment plant operations at one or both of the plants involved could be significantly effected. For these and other reasons, the region is celebrating the return of a regional planning fiamework. Liquid Waste Management Plan In 1989, GVRD completed stage one of an extensive, region-wide study to find the most cost-effective and environmentally acceptable method for disposing of liquid wastes in the region. This project was a first step in the development of a regional Liquid Wasfe Management Plan (LWMP)-a provincially mandated undertaking (GVRD 1996: xi). The objective of the LWMP is to, "manage liquid wastes in a manner that enhances the environmental quality of the region's receiving waters" (GVRD 1996: 9). Stage one of the plan considered a range of issues, including upgrading wastewater treatrnent plants to meet increased demand and more stringent regulations, controlling combined sewer overflows and stormwater ninoff, and increasing controls on the quality of industrial effluent discharged into sewers. Stage one work indicated that expenditures in excess of S 1 billion over the following 20 years would be required to address these issues (GVRD 1999). Work is now under way on stage two of the LWMP. It will include: implementation of secondary treatrnent at the Annacis and Lulu Island treatment plants by the end of 1998, and March 3 1, 1999 respectively; increased measures for control of industrial discharges to sewers; facilities to control combined sewer overfiows; and development of a regional strategy for controlling stormwater runoff (GVRD 1999). A 1996 LWMP update report stated, The public has consistently said it wants to improve the environmental quality of the region's receiving waters but are concemed about cost. The cost of sewerage and drainage upgrading is high and there are competing priorities in the region, such as drinking water quality, solid waste disposal, air quality, transportation, and heaith services. With this in mind, the region will use a "balanced approach" to planning aimed at finding an acceptable balance between regdatory objectives, public values, environmental science, costs, and benefits. ( GVRD 1996: iii) It is anticipated that both the Lulu and Annacis plants will require upgrade and expansion work by 2006 in order to satisQ growth. The LWMP directs upgrades and expansions to sewerage infiastructure. The plan also addresses many other liquid waste management issues facing the region. Forecasting sewer demand is a necessq component of the LWMP as the design and scheduling of facilities relies on this type of information. Consequently, it is anticipated that a more accurate demand forecasting tool will enhance the liquid waste management planning process. Sewer Demand Forecasting Ovewiew Long-range forecasts of friture demand for sewer senices are indispensable to the efficient management of municipal sewerage facilities. Forecasts, and the planning activities which rely on them, determine the investments which sewer utilities make, or forego. Forecasts are conditional because they contain assumptions regarding future levels of sewer demand, future economic conditions, and future disposa1 prices. Any forecast is an estimate of the most likely level of fùture sewer demand, given that al1 of the underlying assumptions prove correct. Accordingly, forecasting methodology is as much concerned with finding the appropriate assumptions as with calculating expected wastewater discharge rates given the assumptions. In general, sewerage system forecasts are made infiequently. Often forecasts undergo small-scale updating to reflect new operating conditions. The forecasts usually focus on aggregate wastewater flows, including unaccounted-for inflow and infiltration. Specifically, the focus of the forecast is total wastewater arriving at a treatment plant, not wastewater discharged by any particular customer category. Yet, it is often desirable to analyze trends exhibited by customer groups in order to understand the sensitivity of wastewater generation to broader social and economic changes (Baurnann et al. 1997: 79). In addition, forecasts often focus on only one measurement dimension. For example, maximum daily flow, or total annual flow. Many forecasts are based on the per capita requirements method, an approach that goes back to the very first wastewater forecasts. Today, many existing forecasting practices re!y, for the most part, on the notion of per capita wastewater coefficients. Surveys by Corps of Engineers planners in the United States, and of state and local water planners in Australia, confïrm that per capita methods are used more often than any other method (Jones et al. 1984: 64). In this method, aggregate sewer demand is expressed as the product of residential population and a per capita wastewater coefficient. This relationship is projected into the future, using expected future population and extrapolated values of the per capita coefficient. Because only aggregate sewer demand is considered, per capita forecasts are insensitive to differing commiinity structures or wastewater generation patterns. The contribution of non-residential-industrial and commercial-sectors to total sewer demand is implicitly assumed to remain relatively unchanged throughout the forecast period. In spite of its popularity, the per capita approach has shortcomings (Jones et al. 1984: 64). The results of aggregate forecasts are not usefül for many planning tasks, such as the consideration of water conservation on total demand-measures which selectively alter water use in one or two user sectors. Also, the sensitivity of fùture sewer demand to alternative assumptions regarding fùture economic and demographic change cannot be detemined. Attempts to correct some of these deficiencies by developing disaggregate forecasts have been harnpered by heavy data collection and processing requirements. Further, the inclusion of additional explanatory variables creates the need to forecast future values for those variables, multiplying data requirements in areas where data may not be readily available. The choice of forecasting method should balance, for each application, the benefits of more advanced and complex techniques against the cost and difficulty of data collection and analysis (Jones et al. 1984: 50). Benefifs of a Reliable lnduswal Sewer Detnand Forecasf in GVS&DD A sewer demand forecasting model attempts to predict future demand by modeling the present and projecting into the hture. A clearer picture of future levels of sewer demand would benefit GVS&DD for a number of reasons. Perhaps the most popular use to which a sewer demand forecast could be put is the sizing of new infiastructure. Typically, it is argued that it is "better to be safe than sorry" in sizing sewerage facilities. However, such conservatism canies a cost in excess capacity which may place an unreasonable payment burden on initial system users or, in the case of excess interceptor sewer capacity, may allow for unplanned sprawl or expansion devefopment dong the Lines of interceptor systems not planned for in community growth plans (Amold 1979: 184). A reliable forecast of demand cm help to minimize risks such as these. A reliabIe forecast of fbture flow and loadings to a treatrnent plant can help utilities manage and maintain receiving water quality. Knowledge about the anticipated quantity and quality of municipal effïuents increases the likelihood that mitigation strategies are well timed and effectively designed. Similady, it may allow system planners to better understand the fùture interconnectedness of currently disconnected portions of the sewerage system, thereby facilitating the coordination of works conducted on each. Further, such a forecast may help prioritize sewerage facility maintenance and repair projects by determining fiiture system usage rates, and consequently, estimates of facility life expectancies. A reliable forecast can also aid decision-makers to identiQ those strategies or policies that wiil result in optimization of current and planned sewer infrastructure investrnents. Also, an industrial sewer demand model may enhance the decision making process by first presenting a view of the future, then allowing the future to be altered by changing starting conditions and assumptions used in generating the original prediction. In this way, alternative strategies for meeting new sewer demand cm be evaluated. An industrial sewer demand forecast-a product of this study-will contribute to the development of a total sewer demand forecast for GVS&DD, and hence, to the achievement of some, or possibly all, of the goals listed above. A forecasting tooi which helps to explain some of the factors which determine industrial wastewater flow and loadings will provide greater resolution to the aggregate sewer demand forecast. An understanding of the role that infiuencing factors play in determining demand from the industrial sector will make the overall sewer demand forecast more representative of the "tme" future. Detennining the optimal forecasting technique required to achieve these goals is the topic of the next section. Forecasting Techniques Baumann et al dehed a forecast as a "statement about the future" which "implies the existence of method, perhaps a mathematical model or at lest a calculation of some sort." Further, that "no forecast can be guaranteed" and, "at best, forecasts provide decision maken and others with a sense of what can happen in the future", not what will happen. Finally, they asserted that "it is not the job of a forecaster to Say what should happen" (Baumann et al. 1997: 81). A nurnber of different forecasting or modeling techniques are comrnonly used to detennine sewer demand, An oveniew of the more popular arnong these is presented next. Time Extrapolation In Time E;rtrapolation, wastewater generation can be represented as a time series, with past observations fitted to a smooth curve by graphical or mathematical curve-fitting methods. Once the curve is fitted, forecasting is done simply by extending the curve into the future. The underlying assurnption here is that the level of wastewater generation is explained by the passage of time and that al1 other variables, such as population, price, employrnent, are either uncorrelated with wastewater generation or perfectly correlated with time. This approach, however, is highly subjective, using very little data. It attempts to explain wastewater generation in terms of a variable, time, which by itself explains nothing (Baumann et al. 1997: 85). Bivariate Models In this form, the future is explained in terms of a single variable, usually population. Using the linear form: D - a+bX Where: D - demand for sewerage services X - explanatory variable a,b = coefficients This mode1 can be used to forecast total or specific customer demand. Also, D may also be a rneasure of average annual, sumrner season, or maximum daily wastewater discharge (Baumann et al. 1997: 85). Per Capita Requirements Method In this method, the mode1 is represented as follows: Where: D - average daily aggregate demand P - population b - per capita discharge rate This method can be applied to disaggregate or aggregate sewerage system use. The per capita method assumes that a single explanatory variable like population provides an adequate explanation of sewerage system usage. Other variables are assumed to be either unimportant or perfectly correlated with population. This method is generally considered to have a large subjective content, especially when applied to aggregate demand. However, reduced variabiiity in per capita rates within a specific customer group tends to improve the robustness of disaggregated demand forecasts. The data requirements for this method are modest, only wastewater discharge data and population are needed. Multivariate Models In order to alleviate some shortcomings of the simple per capita method, this method includes characteristic unit use coefficients for disaggregated user groups. As the sectors and categories to be forecast become srnaller, it becomes more and more reaçonable to explain wastewater discharges within the sector or category in terms of a single variable. Coefficients from multiple user groups can be combined to produce forecasts that are sensitive to factors effecting individual user groups, such multivariate models take the following form: Where: D - wastewater discharge per unit time Xi - explanatory variable i a, bl, b2, . . .b, = coefficients The use of a multivariate model reduces the degree of subjectivity in an analysis, and makes better use of available data. It is for these reasons that multivariate models generally represent an improvement on bivariate models. One drawback of this approach is that the model reflects correlation rather than causation- There is also a risk of incorporating spurious correlations, which may appear in historical data but are not likely to be repeated in the future (Baurnann et al. 1997: 89). Econometric Demand Models Models of this type differ from multivariate models in that they are based on theory, and in their form, express the most likely causal relationships between explanatory variables and total demand. Using principles and techniques of econometrics, models can be developed that describe the true economic demand for a service. The literature does not include any cases where econometric demand models have been applied to sewer demand forecasting; they have seen only limited use in the context of residential water forecasting (Baumann et al. 1997: 88). Sewerage Requirements Approach Baumann et al stated that the traditional method of forecasting industrial water use is what is referred to as the water requirements approach. This postulates that water use in an industriai establishment varies proportionately with the scale of production in that establishment, where scale is measured in terms of physical units of output, dollar value of output, or the size of the labor force ernployed in the establishment. Although the authors make no specific mention of industrial wastewater, it is possible to extend their cornments to the disposa1 side of the industrial water use cycle. Accordingly, the sewerage system capaciw requirements approach, as it rnight be referred, would postulate the same theory as that used in the wafer requirements approach. By accepting the interchangeability of the water requirements and sewerage systern capaciîy requirements approaches, the principies of the former cm be applied to the latter. In doing so, forecasting industrial sewer demand would result in either of the following equations: Where Xi - wastewater discharge fiom an establishment in the ith type of industry Yi - production by the establishment Ei - number of employees in the establishment Ai - wastewater discharge per unit of output in the ith type of industry Br - wastewater discharge per employee in the ith type of industry In this case Ai and Bi are treated as constants-they vqby industry i but are fixed over al1 establishments in an industry. IWR-MAI N Water Demand Forecasting hrlodel Indeed, over the last two decades, water planners have begun using disaggregated water generation forecasts, which take into account differences in the socioeconomic characteristics of the resident and no~esidentialpopulation, as well as seasonal variations in economic and climatic conditions of a study area. The IWR-MAIN Water Demand Analysis Software was developed as a water-planning tool that provides a thorough, disaggregated approach to water demand forecasting and analysis (Baumann et al. 1997: 22). The IWR-MAIN model is a commonly used model for estirnating water use. Although it focuses on water use, the direct relationship between water use and wastewater discharge warrant a brief description of this forecasting tooi. The IWR-MAIN Model is based on the MAIN II System developed in the late 1960s by Hittman Associates, Inc., for the US Office of Water Resources Research (later Office of Water Research and Technology). The IWR-MAIN Model was designed to permit considerable disaggregation of industrial water use. Per employee water use coefficients for 104 selected three-digit Standard Industrial Classification (SIC) codes are used in the model (Jones et al. 1984: 78). Water use per employee coefficients, contained in IWR- MAIN, are the result of 10 years of research effort devoted to collecting data on employment and water use for various establishments throughout the US. Data for approximately 7,000 establishments were collected for this purpose. The water use coefficient for the manufacturing sector-SIC codes 20 through 394s470 liters per employee per day; 2,784 establishments were surveyed to generate this nurnber (Baumann et al. 1997: 102). Total industrial water use is calculated by multiplying manufacturing employment by a unit use coefficient (Jones et al. 1984: 8 1). The close relationship between industrial water use and industrial wastewater discharge allows a reasonably direct cornparison between the industrial water demand forecas~g module included in IWR-MAIN, and the industrial wastewater demand forecasting being investigated in this body of work. The model of water use in the nonresidential- commercial and industrial-sector is: - Qi f (GEDi, 6,b, Pi, CDD, Oi) Where: Qi = category-wide water use in gallons per day GEDi = per employee water use in gallons per employee per day Ei - category-wide employrnent L, - average productivity (of labor) in category i - Pi - marginal price of water and wastewater services in category i CDD = cooling degree days - Oi - other variables known to affect comrnercial/industrial water use Although this theoretical nonresidential model is included in IWR-MAiN, the absence of elasticities for price, productivity, cooling degree days, or other variables means that the current default calculation is based upon volume per employee per day coefficients for non-residential sectors. The form of the equation is: Qi = (GEDi x Ei) Survey of Nom American Sewer Demand hrecasting Approaches In order to better assess the current status of the Greater Vancouver Sewerage and Drainage District's industrial sewer demand forecasting efforts, a survey was conducted of other jurisdictions in Canada and the United States. Survey results are discussed below and summarized in matrix form. They provide an "at a glance" look at forecasting methods employed by local governments across the continent. Jurisdiction-specific issues and municipal staff comrnents and observations related to demand forecasting initiatives are included. In selecting jurisdictions to be surveyed, an attempt was made to compile data fiom a variety of climatic, geographical, and economic regions within Canada. In addition, Seattle, the rnost proximate American city to GVRD, was selected because of its similar size and coastal location, and the need for this study to have an understanding of the American experience in the context of sewer demand forecasting. Two objectives are met by conducting a survey of sewer demand forecasting methodologies employed by other North American jurisdictions. It helps demonstrate the range in complexity and significance of forecasting methods utilized by other local governments that differ in size and location. Also it provides a fiarnework within which GVS&DD's current forecasting initiatives can be viewed. GVS&DD Increased dernand for sewerage services in GVS&DD fiorn al1 three customer groups has demonstrated the need for comprehensive wastewater management planning. Strategies for allocating limited available sewerage conveyance and treatment capacity among customers are now needed as are the means by which proposed system expansions cm be evaluated. It is therefore becorning increasingly important for sewer utility managers to identiQ both the allocation strategy which wilt optimize current system capacity, and the amount and timing of fitture treatment capacity. In the past, "business as usual" growth assumptions and municipal officia1 community plans were employed in the development of regional population projections in the Greater Vancouver Regional District. Two or more scenarios were included with ali estirnates of future growth patterns in the region. However, in 1998 the Strategic Planning Department identified one growth scenario referred to as the "Growth Management Scenario" as that which is most likely to be realized in the îüture (Perkins 1998). Consequently, flow and Ioading forecasts for the region's five WWTPs are now expected to reflect population projections expected under the Growth Management Scenario. This scenario assumes coordinated gr0 wth throughout the region according to GVRD 's Livable Region Strategzc Plan. For the purposes of forecasting GVS&DD industrial wastewater flow and loadings in this study, the Growth hfanagement Scenario, and its related employment forecast, are used. GVRD has relied heavily on its understanding of sewerage system capacity constraints for justimng capital expansion projects. Further, to forecast fiiture sewer demand and consequently plan for system expansions, GVS&DD relied upon extrapolated population growth figures. Population trend analysis yields straight-line forecasts of the future. However, changing demographics, fluctuating economic conditions, and technological advancements ofien distorted the straight-line growth assumption and therefore increased risk and uncertainty in planning for the fbture. The size of plant expansions are based on accommodating peak flows, not base flows. Average dry weather flow (ADWF) projections are based on historical per capita dry weather fiows for each sewerage area, population projections, growth densities, and the extent and condition of the sewerage system (Peddie 1997). In order to accommodate peak wet weather flows (PWWF), an estimation of this variable is made by multiplying the projected average dry weather flow by an assurned or estirnated peaking factor (PF). The PF is estimated based on assumptions for development density and contributory areas, as well as measured values of inflow and infiltration, and estimated impacts of combined sewer overflow (CSO) management prograrns (GVRD & ABR 1992). in order to avoid sewer back-ups in the streets, as well as residences, businesses, and waterbodies, GVS&DD c~mentlysizes its wastewater facilities based on peak volume of wastewater flow anticipated during a storm of the scale this region experiences approximately once every twenty years. Total forecast flow and historical influent concentrations for BOD and TSS, are then multiplied together in order to calculate future treatment plant influent loadings. Current flow and loading projections for 3 of the district's 5 wastewater treatment plants are shown in table 5. Table 5 Current GVS&DD Wastewater Flow and Loadings: Actual and Projections Sewerage Parameter 1993 1994 1995 1996 2001 2006 201 1 2016 2021 Area Flow 358 419 416 466 516 559 602 641 (Mu4 BOD - 72,710 81,490 77,872 87,247 96,565 104,464 112,602 119,840 CKg/d) Fraser Tss - 57,821 68,732 67,195 73,425 81,268 87,915 94,764 100,855 (Wd) Se wered ------Population Flow 54 55 57 65 65 73 80 88 95 , Wd) 10.205 12,699 12,178 12,433 13,790 15,443 17,035 18,618 20,201 Lulu Island (Kg/d) West TsS ' 12,159 12,970 10,742 10,115 13,156 14,733 16,251 17,762 19,273 (Kg4 Sewered - - - 139,400 158,500 177,500 195,800 214,000 232,200 Population Flow - - - 6,939 - 16,705 - - - _ (m34 l BOD - - - 1,988 - 4,905 - - - Northwest (Kg/d) Langley TSS - - - 1,805 - 4,350 - - (Wd) Sewered - - - 16,977 - 41,098 - - - Population Source: Memo from Craig feddie to A. Moore Octr97 SoutAiëii FloWsLlnd Lou& Projections - Compass Resource Management Demand Forecasting - L WMP Contributions of wastewater fkom industrial and commercial operations are included as a component factor of the per capita flow coefficient. It is assurned that the ratio of wastewater contribution hmindustrial and commercial areas to wastewater contributed by the residential population remains constant. Population projections for the sewerage areas served by the plants are provided by the GVRD's Strategic Planning Department. Greater Vancouver Sewerage & Drainage District sewer demand forecasts coincide with either updates of the Liquid Waste Management Plan which typically occur every 4-5 years, or system expansion and upgrade project requirements. The current planning horizon for the LWMP is 2036. GVS&DD is currently experimenting with a neural network approach to estimating or forecasting sanitary flows under dry-weather conditions. Neural networks are nonlinear and attempt to capture complex interactions between input variables in order to generate an output value. The hope is that the neural network approach can be used to estimate, more accurately, increases in wastewater resulting fiom population growth or land use changes. '"With a more realistic estimation of actual conditions, a comparison with design vzlues will identiQ available capacities for future growth and allowances for inflow and infiltration" @jebbar and Kadota 1997). Also, better understanding of the level of service provided by existing facilities can be determined. North Arnerica Capital Regional District (CRD) There is no comprehensive regional sewer demand forecast in the CRD. Instead, member rnunicipalities provide CRD with municipality-speci fic sewer demand forecasts- measured in units of flow only-which are based on municipal land-use projections, population projections, and traditional design wastewater unit flow rates. Municipal forecast data consequently provide CRD with information regarding the appropriate sizing of trunk sewers and treatrnent facilities. Currently, CRD is developing a geographical information system (GIS) mode1 which will integrate known sewer flow data with population/land-use projections to yield a more detailed area-specific sewer demand forecast (Fe11 1997). The CRD does not develop a sewer demand forecast specifically for the industrial sector due to the relatively low level of industrial activity in the region. However, forecasts based on analyses of flow and loading data collected at district facilities, coupled with source control monitoring data, are possible (Fe11 1997). Sarnpling results indicate that most industrial sources discharge wastewater that exceeds CRD regulations for BOD and TSS. Regardless of this observation, the resultant contaminant loads received at the twc? sewer outfalls located at Macaulay Point and Clover Point, fail to result in significant permit exceedances (Waxman 1992: 6-1 1). In addition, industrial loads fail to impact significantly on CRD's collection and treatment system. In accordance with standard sewer design classifications, the industrial discharge component is broken down into the following broad categories: light, medium, heavy. This broad breakdown structure allows for the calculation of population equivalents and unit flow and loading rates. Sewer demand forecasts, rather than being conducted on a regular basis for the entire region, are developed in response to specific project requirernents. The Sannich Peninsula Treatment Plant, and the Western Cornmunities Trunk sewer projects both required demand forecasts in order that cost sharing formulae couid be developed for those member municipalities serviced by the new tmnk lines (Fell 1997). City of Kelowna In the City of Kelowna, staff in the Works and Utilities Department generate sewer demand forecasts employing information obtained from municipal OCPs and population projections. Future flows in the tdsewers and at the WWTP are predicted using the Sanitaty System Analysis SAlVSYS Mode1 which is run using municipal population growth and distribution data in conjunction with both standard design and historical per capita unit flow rates (Berry 1997). Again, industrial flows are asswned to change in proportion to residential population and are therefore included in the per capita unit flow rates. City staff monitor flows constantly and use this data to generate annual forecasts which contribute to capital improvement planning, Source control initiatives and inflow and in filtration programs. The City of Kelowna has developed a comprehensive Wastewater Management Plan that establishes planning priorities for the next 50 years. However, a 20-year senicing plan is referred to for more detailed sewerage system planning requirements. With respect to BOD and TSS, Mr. Berry, Utilities Engineer for the City of Kelowna, States that, "forecasts for these contarninants are not considered to be important due to the low strength of the wastewater and the relatively small amount of industrial activity in the region". Industrial loadings of BOD and TSS are regulated by way of loading-based limits included in discharge permits issued by the City (Fell 1997). City of Calgary Total system sewer demand forecasts use growth scenario-based population projections-low, medium, high-which consider net migration, demographic changes, land-use patterns, employment data, and economic activity forecasts. Ln addition, water consumption data are combined with civic census data to help build a sewer demand forecast to the year 2050 for flow and loadings with respect to conveyance and treatment. For classification purposes, sewer users are designated as: residentiai, small commercial, large commercial. Although flow and loadings are forecast, flow receives the most attention as it is considered more limiting than BOD and TSS loadings (Bohn 1997). Yearly changes in per capita unit flow and loading rates are monitored and compared with growth projection assumptions. Only trends in the rate of annual change in flows and loadings, inconsistent with growth projections, will result in the long-term sewer demand forecast being recalibrated (Bohn 1997). City of Regina With a current population of 180,000, the City of Regina has not experienced significant population growth in the past and does not anticipate to do so in the future according to Walter Friesen, Environmental Engineer with Regina's Municipal Engineering Department. Consequently, the city does not have a long-term forecast for sewer demand. Instead, conveyance and treatment system expansions and upgrades are guided by the Planning Department's Development Plan that provides sewer planners with land-use ~Iassifrcationsand projections. Sizing of tnuik sewers depends to a large degree upon "institutionalized" design criteria for various land-use sectors. Interestingly, the city has a number of trunk sewer lines that previously required "twinning" to accommodate flows; poor sewer demand forecasts are to blarne for the shortfall in capacity (Friesen 1997). Metro Toronto Metro Toronto, which operates the major artenal trunk sewers and four WWTPs in the Toronto area, uses a sewer demand forecast for planning purposes. The forecast is based on residential population and employrnent projections provided by Metro Toronto's Planning Department. Due to the fact that the area within Metro Toronto's jurisdiction is fully developed, non inflow- and infiltration-related growth is expected to corne only as a result of rezoning (Chessie 1997). A hydraulic model of the sanitary sewer system quantifies current hydraulic loads and remaining capacity in trunk sewers rather than providing a forecast of future system flows. Based on model predictions, some relief sewers will be required by the 201 1. Patrick Chessie of Metro Works points out that with respect to deciding what capacity a proposed trunk sewer should have, there seerns to be an incongruence between tirnelines for population forecasts-40 to 20 year horizon-and sewer life-spans-100 to 200 years. An inability to forecast far enough into the future so that the sewer capacity continues to meet sewer demand at the end of its life-span encourages Metro Toronto to install very large diameter trunk sewers, sized according to construction-based design criteria (Chessie 1997). Future industrial sewer demand is calculated by combining "fixed flow rate" and 'bits of zoned land" factors with projected land-use plans. To calculate current flows fiom the commercial and institutional and industrial sectors, residential flows-based on water meter records-are subtracted fiom total WWTP influent flows. Needless to Say, this exercise does not differentiate between industrial and commercial and institutional flows, nor does it address BOD and TSS loadings from these sectors. As a consequence, Metro Toronto is unable to benefit from wastewater policies and regulations aimed specifically at either the industrial or commercial and institutional sectors-the two are essentially inseparable. Ottawa-Carleton Sewerage system planning in the Ottawa-Carleton area relies upon Canada Mortgage and Housing Corporation's CMHC Cohort Survival Mode1 to develop population, demographic, and employment projections. In addition, hydraulic forecasts for conveyance and treatment facilities are generated using the Storm Water Management ModeZ N SWMM N which has been applied to the regional unicipality's sewerage system. In order to help refine nonresidential sewer demand forecasts and optimize capital investments, per employee or per square foot factors are being researched for the industrial and commercial and institutional sectors. Regional employment surveys, conducted every 5 years, yield information on the number of employees by sector. When these sweys are coupled with historical industrial and commercial and institutional demand data, they will yield per employee or per square foot factors. Kevin Cover, of the Planning and Development Approvals Department believes that this level of detail will provide better resolution to the demand forecast than simple per hectare unit flow rates. Halifax Regional Municipality Standard design criteria and land use forecasts are used to size sewerage facilities in the Halifax Regional Municipality. Less than half of the wastewater generated in the municipality is treated by three tertiary WWTPs. The remaining wastewater is not treated prior to discharge into Halifax harbor. Predesign work for an advanced primary WWTP to serve the City of Halifax and the City of Dartmouth will result in a plant capacity equal to that necessary to serve a population 1.8 times the current population of the two cities. A key assumption of the predesign report was that increases in influent flows and loadings to the plant would be due only to inflow and infiltration, with no expected contribution from population increases in the 20-year planning horizon. Consequently, municipal staff do not feel that a detailed sewer demand forecast is required (Tomar 1997). Metro Seattle Metro Seattle has recently completed a planning process called Wastewater 2020 Plus aimed at assessing the long-term wastewater conveyance and treatment needs of Metro Seattle. The planning process relied upon a forecast of sewer demand which used projections of population and employment. Base sanitary flow estimates for al1 three major sectors were estimated by multiplying unit flow factors-based upon past studies and hisrorka1 flow measurements-by either population or employment projections (HDR 1994: 1-7). Population and employment projections were calculated fiom census data and Washington State Employment Security Department commercial and industrial employment estimates. These estimates were based on econometric models that took into consideration local, state and federal economic and demographic factors. in addition, geographical information system technology was used to help manage data spatially. With this information, Metro Seattle has developed a sewer demand forecast, disaggregated to the major sector level until the year 2050 by extrapolating from the plan's 2020 horizon. Due to the availability of customer-specific unit flow factors and employment information on industrial subsectors, Metro Seattle can generate sewer demand forecasts down to the industrial subsector level (Peterson 1997). However, a lack of data on the projected spatial distribution of employment prevents Metro Seattle fiom precisely allocating flow to specific sewerage seMce areas. Survey Results The results of this survey demonstrate that there is considerable consistency with respect to the general methodology employed by jurisdictions to forecast sewer dernand. In al1 cases, population projections are combined with agreed upon unit flow rates to arrive at estimates of future hydraulic requirements. Certainly, there is vanability in the degree of forecast mode1 complexity. For example, the City of Regina applies standard design per area unit flow rates to industrial land quantity figures to generate estimates of friture flows, while Metro Seattle employs complex econometric models and geographic information system technology to estimate flows at a disaggregated industrial level. This variability, it would appear, is caused by differences in the perceived need for resolution in the total system demand forecast down to the industrial level by utility planners and managers. Some jurisdictions have high growth and a consequent need for a comprehensive sewer demand forecast, while other jurisdictions anticipate little or no growth, and consequently feel no need for any resolution past the most broad level, that being the total system dernand forecast. Survey participants in jurisdictions with sewer demana forecasts al1 agreed that increased resolution in their forecasts would be desirable. However, due to the cost of fine tuning demand forecasts, most participants expressed a belief that such an endeavor would be unlikely to satisv a cost-benefit test. Al1 those surveyed agreed that a reliable sewer demand forecast would help to optimize both returns on capital investments and the remaining capacity of existing sewerage facilities. The results of the survey show that there is variation in the way local govements manage, perceive, or conduct forecasts. This variation is due to differences in a nurnber of factors including: the age and capacity of the sewer system; future development and growth potentials; local economies; governent regulations; and availability of human resources and hding. The fact that al1 jurisdictions surveyed conduct some degree of sewer demand forecasting reinforces the notion that sewer utility management can be enhanced through demand forecasting. However, it should be noted that little attention has been paid by other jurisdictions specifically to industrial sewer demand forecasting. Instead, emphasis is generally placed upon the development of a total system sewer demand forecast which includes conveyance and treatment facilities, and al1 three sectors-residential, commercial and institutional, industrial. Table 6 North American Survey Results lndwtrirl Secîor Freqmcy and Canadian a sewered Smm ûemand Horiron of Seuwr Pop. D_ng -and Jurisdicüons Mahoddo~y 1 ForeCaSb (x Anmcis Secondvy .Uultiply historiu1Iy derivtd with No indusaial foreust Coincide loru Island Primary Vancouver ADWF unit flow fxton by pop Industid flow/loadings updates of LWMP. Seweraga & and luid-use projections hm Lions Gate Primary includcd in aggrcgate Ycar 2036 planning Lulu Secondary Drainage OCPs and LivabIe Rcgion forcc;ist. horizon. Disîrict Strategy growth assumptions. Langlcy Secondary Badon WWrP Core arc3 of cm: loading figures and Depemdent upon Capital Use municipal land-use fine scrcening. projections; planning or Source Conml &ta projcct-specific Regionaf Synich Peninsula &gineering population Flow rates bascd on rcquimnmts. and Gulf Islands: 2" District - projections: ditional design derived population 25 year plmning Victoria trcatrnentfseptic wastemta flow rata. cquiwlents (Wiumm horizon. fields. 1992). Dependent upon projcct-spccific Two Secondary Input pop projection figures from NO industriai foreust. conditions- Toul ms. City of OCPs into 'SANSYS" model. Indusmal flow regiowl flows One mtsmjority Not Kelowna Model uses standard mgincering included in per capita rommnally. of flows. ûther mts available. wastewaicr flow rata. figures. 20 yem planning discharge hmthrec horizon. indusaial plants. Two Teniiuy ~parately;total Flows/loads foreras using pop No indusmal foreas. Ws. 'Oreust City of and land-use projection &ta. dw Indumial flownoads zzd Lyge plant: Calgary census &ta and histoncaI per included in per upita 550.000 rn3/day reviewedjupdated Small plant: capita watcr consurnption ratcs. figurcs. annually. 73,000 m'/&y Y- 2050 planning I horizon. Apply sm&rd engineering City of One Tertiary for al1 wtewatcr flow rata to pop and wastcmter. Regina land-use projections. Coincidcntal with Apply historiully bascd per Use stanw indusrrial Four Secondiuy mtiorul census. Metro cipita wtewata flow nta .per wsrtewJter WWrPs for al1 -. Yur 201 I planning (îdjusted to include al1 seciors) to flow ma. pop projections, horizon. Toronto 1 One Secondwy Regional 1 Included in wnm1 Apply historiully bved per toul systm forccast. WWrP for al1 aru On pcr Municipality capita and pcr wastcwater Year 202 t planning wytewater. WICWatET fl0~KileS. Capacity: of Ottawa- flow ntcs to pop and land-use horizon. projections. 1,000,000 m'/day Halifvr & Dytmouth: No Dependent upon treament. Town of 135 project-specific Apply smdud engineering Bradford & Halifm sewered Regional wastcwata flow rata to pop and No indusmal forcust rcquiments. County: Thm 215 un- 20 year planning Municipality land-w projections. WWïPs: Pn'mary, scaered horizon. Secondvy & Terticrry I I Coincide with updltcs of Puget (bd Apply indus. Sound Regional Two WWTPs. Apply unit flow factors on flowAoad factors to Councii pop Rimary- 133 MGD past studics and mesud flows) cmploymcnt Secondary - 103 to pop and ernployment forecasts. forec3srs. MGD projections. Year 2050 planning 1 horizon. Obstacles to lndustrial Sewer Demand Forecasting in GVSaDD The current practice in GVS&DD is to aggregate sewer demand forecasts. Although there is a stated desire to disaggregate forecasts, a lack of historical industry-specific data- absent because previously it was not needed for aggregate forecasts-means that this task will be difficuit. Further, existing institutionalized structures may not adequately support efforts to collect and process the additional data required for disaggregated forecasts. Conservative forecasts are usually higher than the most likely vaiue, so as to reduce the probability of constructing facilities which tum out to be inadequate. Although, building large facilities usually generates economies of scale, planning in this way has a significant cost, of course. It leads to systematic overbuilding and pemanently higher capital costs. A forecast that was purposely skewed downward would also imply a cost. Facilities wouId be systematically underbuilt, sacri ficing economies of scale and increasing the probability of system failure. The advent of large scale and cornprehensive sewer systems followed massive public outcry over the impacts of poor sanitation services on comunity and environmental health. A supposedly precise forecast that leads to a system failure, and consequently, to a release of untreated wastewater into a street or local waterway, is anathema to the public conscience- It is far safer to ask the public to pay for oversized treatment plants, built on the basis of conservative estimates of future demand, than it is to deal with the negative fallout from a discharge of raw sewage from an undersized treatrnent facility. Ironically, design engineers overbuild because they know excess sewerage system capacity will eventually be needed; however, the same people are typically loathe to ensure oversized environmental buffering capacity in anticipation that one day it also will be needed. A robust forecasting mode1 of any sort requires accurate data in order to be valid and perform well. Unfortunately, because of strict proprietary interests within the industrial sector, obtaining data on manufactunng processes, or production and employment levels, is often difficult. David Dunlop, of the Uniformed Textile Service Association, claimed, "Industrial laundries process many different types of items Eom many industries, and to try to characterize our industry based on one facility is ludicrous" (Dunlop 1998: 10). GVS&DD's Technical Working Group (TWG)-comprised of representatives from sixteen industnal operations îhat discharge wastewater into GVS&DD's sewerage system- expressed concern regarding the asswnption that industrial employment and sewer demand are correlated (Carley 1998). The advisory group daims that each Company has a unique mix of factors that influence production and manpower including: consumer trends, interest rate changes, local, regional, provincial, national, and foreign economy projections, commodity price factors, global competition trends, and capital availability and risk factors. The advisory group also state that, ". . . the models used by industry to predict demand and changes in production are dynamic, complex and confidential" (Carley 1998). Data, necessary to verifL forecast accuracy is expected to remain scarce in the greater Vancouver region. Chapter 4 - GVSBDD industrial Sewer Demand Forecasting Model By definition, a model is a simplification and representation of the knowledge we have about a system. If a model cm provide an accurate representation of a system, it can be used to conduct experirnents which othencise would not be possible. In this study, the system of interest comprises the industrial sector operating within the area served by GVS&DD, and the district wastewater treatment plants into which wastewater fiom these enterprises ultimately flows.The benefits of a sewer demand mode1 have been discussed previously, yet the feasibility of such an endeavor has yet to be investigated. What follows is a description of the modeling conceptualization and development process. Geographical Context Eighteen voluntary member municipalities comprise the Greater Vancouver Sewerage and Drainage District. Although, it does not cover the exact geographical area of GVRD, GVS&DD is often assumed to be geographically analogous to GVRD. The total area served by GVS&DD facilities is divided into five sewerage areas including the: Vancouver Sewerage Area, North Shore Sewerage Area, Lulu Island West Sewerage Area, Fraser Sewerage Area, and the Northwest Langley Sewerage Area. The boundaries of the 5 sewerage areas and the location of the wastewater treatment plant which serves each (fig. 3) masks differing levels of industrial activity that occur within the boundaries of each sewerage area- Model Objectives The industial sewer demand forecasting model was developed to fulfil two objectives: 1. Calculate the magnitude of industrial flow and loadings to each of the district's 5 WWTPs during the forecasting horizon, 1996 to 202 1; and 2. Allow "what if" scenarios to be run in order to evaluate service options. Model Description Conceptually, the model relies on the correlation between industrial sewer demand and industrial employment. It uses denved per employee flow coefficients and poilutant concentrations to generate outputs that characterize industrial sewer demand. The survey of techniques used by other jurisdictions to forecast sewer demand suggests that this approach is likely to achieve a satisfactory level of output resolution. The following sewerage areas and their respective wastewater treatment plants are included in forecasts. Table 7 GVS&DD Sewerage Areas and Wastewater Treatment Plants seyve*-*m;i -, . . . . ' lwetTm&mplamii - ..., ;-1' ..ci .. Vancouver (VSA) Iona Island Lulu Island West (LIWSA) Lulu Island West Fraser (F SA) Annacis Island North Shore (NSSA) Lions Gate Northwest Langley (NWLSA) Northwest Langley L The current forecast horizon for this model is fiom 1996 to 202 1, with intermediate forecast years of 200 1,2006,20 1 1,2016, and 202 1. However, the horizon cm be extended to suit the needs of the user. A lack of historical data on industrial sewer demand and industrial employrnent prevented the use of regession analysis to establish model parameters. A generalized conceptualization of the model is shown below (fig. 6), followed by a description of model processes. First, BOD and TSS-pollutant-concentrations were calculated for each industry subsector operating in GVS&DD. Second, daily per employee flow coefficients were calculated for al1 industry subsectors. Third, for each of the 5 sewerage areas, average pollutant concentrations and an average daily per employee flow coefficient were calculated. Fourth, total industrial employment within a sewerage area was multiplied by the daily per employee flow coefficient to generate a total daily industrial flow to a specified treatment plant. Finally, total daily industrial flow within a sewerage area was multiplied by the average BOD and TSS concentrations-calculated for the same sewerage area-to generate total pollutant loadings. $F Calculate BOD Calculate Daily Per 3 Concetrations for Employee Flow Concentrations for Ir' - each Industry Cdcients by each Induitry Subsector Industy Subsector Identify 'Significant' ldentify 'Signifiant' Identify 'Significant' Industry Suimectorr Industry Subecton lndrnty Subsectors Openting in Sawwage Opemting in Sewerage Operrting in Sewsnge Area and Use ta Area and Use to Ama and Use to Generate Average Generros Avcrrge Ganemtm Average lklow Wow eelow 3 Figpre 6 Mode1 Conceptualization Ma fhematical Relationships In order to generate forecasts of total industriai flow and BOD and TSS loadings at the region's five wastewater treatment plants, component data were manipulated via the fo 1lowing relationships: - Qi industrial wastewater flow to WWTP i (m3/day) industriai employrnent in sewerage area j (nwnber of employees) per employee flow coefficient in sewerage area J (L/emp loyee/day ) where: industrial BOD loading to WWTP i (kglday) as above concentration of industrial BOD in sewerage areaj (mg/L) TSSi = where: TSSi = industrial TSS loading to WWTP i (kg/day) - Qi as above [TSS,] = concentration of industrial TSS in sewerage areaj (mg/L) Also: Ei - 100% of manufacturing sector employrnent within sewerage area Fi - j-specific industry subsector per employee flow coefficients + j-specific industry subsectors pODj]= j-specific industry subsector BOD concentrations + Z j-specific industry sectors [TSS,] = j-specific industry subsector TSS concentrations + X j-specific industry sectors Note: i = Annacis Island WWTP,Iona Island WWTP,Lions Gate WWTP, Lulu Island West WWTP, or Northwest Langley WWTP and j = FSA, VSA, NSSA, LIWSA,or NWLSA Data The data used in model development include: GVS&DD industrial wastewater quality and quantity data; North Arnerican industrial wastewater data; GVS&DD industrial employment data; GVRD employrnent forecasts; local industry employment data; and census data. A discussion of data collection and processing methods follows. In addition, a 1995 wastewater inventory project, undertaken by GVS&DD source control, was used to identify 'significant' industrial wastewater dischargers. Significant Industrial Dischargers An analysis of GVS&DD's current industrial sewer dernand profile with respect to BOD, TSS, and flow was first conducted using 1995 inventory data. Key industrial sectors and individual companies having significant impact on the district's collection and treatment facilities were identified following an analysis of the demand profile. GVS&DD's source control prograrn was created in 1990 to administer Sewer Use Bylaw No. 164, a bylaw adopted by GVS&DD in the sarne year. Under the bylaw, discharge permits are required for: nondomestic waste discharges over 300 m3 in any 30 consecutive day period; restricted waste which exceeds a defined set of concentration limits; and trucked waste such as septic tank and grease trap contents. It is assumed that by using these criteria to decide whether or not a waste discharge permit is required, the source control prograrn necessarily captures the significant industrial operations in the region. Currently, there are roughly 240 permitted industrial-nondomestic-discharges in GVS&DD (GVRD 1997a). A model is a simplified representation of the real world, and consequently, to model the behaviors of the more than 240 companies requires some effort to reduce the nurnber of cornpanies down to a more manageable number. For the purpose of this exercise, it was necessary to identifjr only those companies, and thus industry sectors, that contribute sign$cant flow and loadings to each of the five WWTPs. The 1995 source control inventory disaggregates total WWTP flow and loadings into the three main sectors including: residential; commerciaVinstitutiona1; and industrial (GVRD 1997a); these data were used to identiS. significant dischargers. First, industrial dischargers within a specific sewerage area were sorted according to the magnitude of their individual flow, BODYand TSS loadings. Second, starting with the Company contributing the largest flow and loadings and proceeding down the list, companies were selected sequentially until the summed total of al1 their flow and loadings amounted to 80% of the total industrial flow and loadings received at each of the five WWTPs. The final list was then sorted according to Standard Industrial Classification SIC and North Amencan Industrial Classification System NAICS codes, thereby identifying which industrial sectors or specific industries produced the most dramatic impact on the treatment plants. This procedure was repeated for flow, BOD,and TSS. This analysis identified the specific industrial sectors upon which this sewer demand forecasting initiative focuses. Moreover, it serves to highlight the industrial sectors for which wastewater characterizations will be made. An analysis of industrial flow and loadings to the five WWTPs in the district demonstrated that only 60 companies in the region accounted for 80% of total industrial flow and loadings at the WWTPs. Further, the 60 compa~eswere represented by only 27 industry subsectors (table 8). Thus, the original 240 plus permitted industrial dischargers were filtered to yield a more manageable, but nonetheless representative, group of 27 industry subsectors. The industrial sewer demand forecasting mode1 focuses on the 27 industry subsectors that were found to contribute significant wastewater flow and loadings to the District's WWTPs. Table 8 Industrial Subsectors in GVS&DD 1 Industrial Subsectors Operating- - in GVS&DD I Airport Operations Landfills Petroleum Refineries Breweries Industrial Laundries Plywood Butter & Cheese Dairy Marine Cargo Poultry Chernical Mfg, Meat Processing Recyclable Paper CoatindEnmavindHeat Treating Milk Manufacturing Re fxigerated Warehouse - - - - - J CommerciaI Bakeries Newsprint Mills ' sanit& Paper Mills Fish & Seafood Product Wholesaler. Non-iron Metal Smelting Seafood Packaging Fresh Fruit & Veg. Wholesaler Other Food Manufacturing Soft Drink Manu facturing Fruit & Veg. Canning Other Snack Food Sugar Manufac turing lndustrial Wastewater Data Wastewater discharge monitoring data for al1 pexmitted companies in GVS&DD were provided by the GVRD's Source Controt Division. Self monitoring data are submitted to source control by permitted industrial operations on a regular basis. In addition, fùrther data on industrial wastewater discharges are collected by GVS&DD sarnpling staff; these data were also used in this study. Data on annual flow, annual tons of BOD, and annual tons of TSS received at WWTPs, dating back to as early as 1990, were used in this modeling exercise. To compliment industrial wastewater data obtained fiom GVS&DD, additional data were collected fiom various reports and wastewater studies. Industrial wastewater characterization data fiom other North American jurisdictions serve to validate and venQ the data obtained within GVS&DD. I nd ustrial Wastewater Data Processing For each of the 27 industry sectors, an attempt was made to generate per employee flow coefficients and average pollutant-BOD and TSS-concentrations. Appendix 1 contains characteristic discharge information for each industrial subsector. Al1 27 industry subsectors are listed and under each sector heading is a list of GVS&DD pennitted companies corresponding to that sector. hdustry sectors are identified by an SIC code number, an NAICS Code, and a corresponding descriptor phrase. For each parameter-flow, BOD and TSS-average coefficients and concentrations are presented for both GVS&DD data and data obtained fiom literature sources. Characteristic BOD and TSS Pollutant Concentrations BOD and TSS pollutant concentrations were calculated for the permitted companies belonging to the 27 significant industrial sectors operating in GVS&DD. To do so, company- speci fic daily contaminant loadings were calculated fkom industry wastewater monitoring data and summed with the daily loadings fiom other companies operating in the same sector. Summed daily permittee loadings were then divided by sumrned daily permittee flows to obtain an average industry sector pollutant concentration for both BOD and TSS. In addition, characteristic wastewater BOD and TSS concentrations for a number of the sectors were obtained fiom various literature sources. Values fiom the available body of literature are usefiil in that they often represent the aggregation of data fiom more than one jurisdiction. These BOD and TSS concentrations were simply averaged to generate a literature derived average concentration. The industry sector characterization spreadsheets (Appendix 1) provide one discharge factor that includes GVS&DD source control industry self monitoring data alone, one discharge factor that includes only literature data, and one aggregate discharge factor that combines both literature data and Source Control data into one composite value. Final industry sector pollutant concentrations for BOD and TSS are derived from an averaging of GVS&DD and literature data. Characteristic Per Employee Daily Flow Coefficients Daily per employee flow coefficients were calculated for the permitted companies belonging to the 27 significant industrial sectors operating in GVS&DD. Daily flow coefficients for each sector are based on GVS&DD source control data only. Average daily company wastewater flow was divided by the total number of company employees to generate a daily per ernployee flow coefficient. The flow coefficient for a given year is calculated by averaging individual company flow coefficients for the same year. The final industry sector flow coefficient is calculated by averaging the yearly figures. Sewerage AreaSpecific Flow Coefficients and Pollutant Concentrations A distinction between different types of daily flow coefficients and pollutant concentrations must be made. Although flow coefficients for companies and industry subsectors have been defined, it is important not to conhise these with sewerage area-specific flow coefficients and pollutant concentrations. Daily flow coefficients that characterize entire sewerage areas were calculated by averaging the flow coefficients of the industry subsectors identified earlier as being significant contributors to industrial wastewater flow within the sewerage area of interest (table 9). In order to run scenario analyses, industry subsector flow coefficients can be adjusted to simulate the effects of policies or economic conditions. Adjustrnents made to industry sector flow coefficients subsequently affect the sewerage area flow coefficient due to the fact that the former are used to derive the latter. Similarly, BOD and TSS pollutant concentrations that characterize entire sewerage areas were calculated by averaging the pollutant concentrations of the industry sectors identified earlier as being significant contributors to industrial wastewater pollutant loadings within the sewerage area of interest. Industry sector-specific pollutant concentrations which charactenze existing GVS&DD industrial discharges were calculated by averaging the yearly average figures described above. Total Employment Data Processing The mode1 relies upon historical, and estimates of future, municipal manufacturing sector employrnent data to derive industrial flow and loading forecasts to 202 1. The correlation between industrial and manufacturing sector employment is assumed to be sufficiently robust to allow the latter to be substituted for the former in this modeling exercise; within GVS&DD member municipalities and sewerage areas, manufacturing employment is considered to be a good indicator of industrial activity (GVRD 1988). The scope of this work does not aliow for a new forecast of employment in GVSⅅ rather it relies upon the results of previous forecasting work. GVRD's Strategic Planning Department has forecast total employment figures for the entire region and for individual municipalities in the region to the year 2021. The employment projections are considered to be reasonable predictions of fhretotal employment levels according to the assumptions contained in the GVRD's Growth Management Scenario; a scenario that is consistent with the goals of the regions Livable Region Strategic Plan. The projected figures are based on the results of recent demographic rnodeling efforts, Statistics Canada data, and current officia1 community plans of municipalities and electoral districts located within GVRD. The employment forecast adopted by the Strategic Planning Department is based on approximately thirty years of regional employment data provided by Statistics Canada's Suntey of Eamings, Payroll and Hours (SEPH), and British Columbia gross domestic product data for the same period. Moreover, the forecast is based on the historical relationship between these two data series. In order to generate a robust estimate of future employment, time series data on the number of people employed by major industry sector with a sufficient number of observations to identify trends and correlations were deemed Table 9 Industrial Subsectors Operating within each Sewerage Area Industrial Subsectors Operating in Specified Sewerage Areas VSA FSA LWSA NSSA NWLSA Al1 Other Food Dry-Cleaning & Breweries Fish & Seafood Mmufactunng Laundry Services Commercial Bakcria Frcsh Fmit & Fruit & Vegebble Brewenes & Frozcn Bakay Vegetablc Wholesaln- Marine Cargo Handling Canning. Picking & Product Manufacturing Distributon Dr~inl3 Butter Cheese & Dry & Lumber. Plywood & Condensed Dais. Dairy & Products Millwork Wholesaler- Iiindfills Poultry Processing Wholesaler-Distributors Produccs Mfg. Disvibutors Coating, Engnving. Non-Ferrous Meut Hardwood Veneer & Heat Transfer & Allied except Aluminum Plywood Mills Activities Srnelting & Refining Rccychblc Paper and Dry-Cleming & Marine Cargo Handling Papaboard Wholcsaler- Laundry Services Distributors Rende!ring & Mat Fat & Oil Refining & Newspnnt Mills Proccssing from Blending Carcasses Fresh Fruit & Seafood Product Vegetable Wholesaler- tandfills Prepantion & Dismbutors Packaging Other Snack Food Soft Dnnk & Ice Petroleum Re fincries Manufacturing Manufactunng Paper (except Plywood MilIs newsprint) Mills Poultry Processing Peimleum Refineries I I I Refngcntcd Poulay Processing Warchousing & Storage 1 Rcndering & Meat Sanirary Paper Product Proccssing from Mmufaicturing Carcasses Seafood Pmduct Son ürink & Ice Prcpantion & Manufacturing Packaging Sugîr Manufactunng necessary (GVRD 1992a). The SEPH data series, with some minor modifications and additions, was selected by GVRD to help build the employment forecast based on the fact that it was the only information source with a sufficiently long historical time series. Histoncal employment figures for the industrial sewer demand forecasting mode1 were obtained f?om survey of eamings, payroll, and hours conducted by Statistics Canada in 199 1 and 1996 (GVRD 1995). Additional employrnent figures for 1994 were obtained fiom GVRD's Strategic Planning Deparûnent (GVRD 1996~). Total GVS&DD Employment Data Total employment figures for municipalities in the GVRD were obtained fiom Statistics Canada and GVRD's Strategic Planning Department. Estimates and projections of total employment for the municipalities in the five GVS&DD sewerage areas for the years 1991, 1994,1996,2006 and 202 1 are shown in table 10- Table 10 Total GVS&DD Employment Total Employment Figures - GVS&DD and Member Municipalitios: Hktorical Estimates and Futun Projections - . . -- -- Municipality 199t Bumaby 93.485 New West 26,980 Delta 29.885 Coquitlam 25,920 Port Coquitiam 13.0ô0 Port MoodyfBelcam 5570 Surrey 77.365 White Rock 6.145 Lang leys 34.695 Pitt Meadows/Maple Ridge 16.975 Fraser Sewemge ha 330.080 VancowerlüEL 333.330 345.079 278.865 391.750 455.000 Vancouver Sewerage Ars8 333.330 345.079 278.865 391.750 455.000 Richmond 1 85.690 93.641 74.565 105.800 125.750 Lulu Island West Sewemge -8 85.690 93.641 74.565 105.800 125.750 District of North Vancouver 21,565 45.265 27,250 32,400 - 47.234 City of North Vancouver 22.81 5 24.600 29.750 35.400 -- r - ~art!~Shore Sewerage Ares 1 %,MO 1 m.454 1 90.315 1 72.650 1 86.450 Data Sources: Statistics Canada. 199 I and 1996 Ccnsus - Labour Force Survey. 199 1 and 1996 ernployment figum. GVRD. "Greater Vancouvcr Key Facts: A Statistical Profile of Grcater Vancouvcr. Canada". Stntegic Planning Department. GVRD. 1997. GVRD. Total Municipal Ernployrnent Figures for che GVRD:2006 and 2021. Unpublishcd data fmm Strategic Planning Dcpmcnt. GVRD. Septembcr 1998. To date, the GVRD has only forecast total employment figures for each municipality for the years 2006 and 202 1. These data are consistent with the assurnptions included in the Growth Management Scenario. For this study, the assumption is made that industrial employrnent is analogous to manufacturing sector employment. Total projected GVS&DD employment for 2006 and 2021 was calculated by summing the Growth Management Scenario data provided by the Strategic Planning Department. Total Regional Industrial Employment Data Forecasters at the Urban Futures institute in Vancouver have forecast regional employment for the ten major industry subsectors through 202 1. Histoncal employment data-the dependent variable-for each subsector was regressed agakt historical BC GDP-the independent variable-to generate a linear regression equation that reflects the relationship betsveen sectoral employment and provincial GDP. Assuming that this relationship will continue into the forecast horizon, estimates of sectoral emplojment were made using the projected estimates of GDP in the linear regression equation. Total industial-manufactUriag-employment in GVS&DD for 2006 and 202 1 was calculated by multiplying estimates of total regional employment for 2006 and 202 1 by estimates of the percentage of total regional employment projected to be contributed by the manufacturing sector in the same years. The latter were provided by the Urban Futures Institute paxter 1998). In order to generate municipal industrial employment figures, additional manipulations were necessary. Municipal Industrial Employment Data The level of ZOO6 and 202 1 industrial employment within GVS&DD municipalities was calculated by multiplying the total regional manufacturing employment-calculated above-by a percentage figure equal to that portion of 1996 regional employment accounted for by the manufacturing sector within each municipality. The municipal industrial employment figures for 1991 and 1996 are based on estimates provided originally by census data. Figures for 1994 were estimated by GVRD's Strategic Planning Department. Municipal manufactunng employment projections for 200 1,20 1 1 and 20 16 were calculated using standard trend analysis tools included with the Microsoft EXCEL spreadsheet application. 'Trend analysis' was conducted using 1991, 1994, 1996,2006, and 202 1 municipal manufactunng employment data. Structural changes to employment in GVS&DD, and to most dancenters across North Arnerica, mean that the manufacturing sector is expected to experience a decrease in its proportional share of total regional employment. The Urban Futures Institute predicts that manufacturing sector employment may only increase 25% from 1996 levels by the year 202 1. Conversely, the number of employees in the commercial service sector is expected to almost double over the sarne time period (Baxter 1998). This will undoubtedly impact industrial wastewater flow and loadings in the region. Northwest Langley Sewerage Area: Manufacturing Employment The drainage basin for the Northwest Langley (NWL) treatrnent plant lies within the boundaries of the Fraser Sewerage Area (FSA). However, in order to determine plant- specific flows and loadings, industrial employment figures were calculated based on the idea that some industrial employment in the Township of Langley contributes wastewater discharges to the Northwest Langley WWTF', and not the Annacis Island WWTP. In order to estimate this percentage split, the percentage of industrial land within the boundaries of the Fraser Sewerage Area that in fact comprises the Northwest Langley WWTP drainage basin was detennined and multiplied by the total industrial employment of the Fraser Sewerage Area. Further, the resulting NWL sewerage area employment figure was then subtracted fiom the original industrial employment figure for the FSA to generate a final industrial employment figure for the FSA. Hence, the employment data for the FSA in table I 1 are net of the Northwest Langley sewerage area employment figures. This approach yields a 96% to 4% split between industrial employrnent served by the Annacis Island, and the Langley plants, respectively. Table Il GVS&DD Industrial Employment Bumaby lO.So0 11.365 9255 New West 3.M 3.274 3,285 Deita 5.793 7.914 6.325 Coq uitla rn 2,080 2.441 5.200 Port Coquiüarn 2.075 2.543 3,0= Port belca cana 1215 915 1 .O40 Surrey 10.095 11.191 19.895 White Rock 170 136 635 Langle~s 4.m 5.094 6555 Pitt Me.dbm/Maple Ridge 2205 1 2.410 4,045 Fmsor Seweng. &u 1 41.736 1 46." 1 9."2 'NOIUWES! Langley a3-Irainage an 1. 1. 1. 1 1. 1. 1sange 8 1. 1. 1. 1. Fraser Sewerage Area 41.736 46.- 1 57.932 55.26!5 63.193 63.568 67.m 69.153 'Vanmuver Sewerage Area 27.910 W.735 1 25.745 27.537 28.050 28.933 29.634 30.696 'Lulu Island West Se- Ana 14,errb 1s.a~1 1.4~' il.ua/ 8.lzr 92x1 8.- 6.893 Nonh Shore Seweage Area , 4.645 5.840 1 6300 - 6083 6.763 6.862 7251 7.407 T5.N Sewerage Ares 1 .~7 1.174 1 1.453 1.386 1,sm 1.595 1.699 1.7% GLaauu 1 m.rw S4,m.Q 1 n.ru 1 10l.a~ 1Or.rir 1 liv~ao 114.~1 1ir.irr Data Sources: 1991 Estirnates: GVRD, "The Employed Labour Force by hdustry Sector & Place of Work in Metro Vancouver". Strategic Planning Department, GVRD,January 1995. P. 35. Original Source of Data: Statistics Canada - 1991 Census. 1994 Estimates: GVRD. "Greater Vancouver Key Facts: A Statistical Profile of Greater Vancouver, Canada". Strategic Planning Department, GVRD. 1997. P. 3 1. 1996 Estirnates: Statistics Canada. 1996 Census Data. Labour Force Survey for GVRD Municipalities. Statistics Canada, 1998. 2006 and 2021 derived industrial employment figures for GVRD municipalities based on Total Employment data (forecast by GVRD Sîrategic Planning Department under Growth Management Scenario). Total industrial employment in 2006 and 2021 for GVRD, based on forecast of percent of total employment contributed by manufacturing sector (Urban Futures Institute, May 1998). Total industrial employment distributed arnong municipalities according to 1996 distribution percentages, or 'Specified %. 200 1, 20 1 1,2016 forecasts of industrial employment by municipality derived by extrapolation of 1991, 1994, 1996,2006 & 202 1 industrial ernployment data using Trend Analysis' tools. GVS&DD Perrnitted Companies: Historical Ernployment Data Employment data for pennitted companies operating in GVS&DD were used to develop accurate per employee flow coefficients. Historical company employment data were obtained directly fkom permitted industrial enterprises within GVS&DD. A survey questionnaire was mailed to al1 240 pemittees requesting historical employment information. The response rate was approximately 50%. Moreover, roughly one third of the 60 'signi ficant ' industrial permittees-as described in Sign ~jicant Industrial Dischargers above-responded to the survey. For those companies that failed to respond, proxy data were used including, employment data included in industrial permittee files maintained by source control, and data fiom the Contacts Target Marketing (CTM) database, 1997 edition. Unfortunately, in most cases the latter two sources of information provided only one employment data point, whereas the swvey generated up to eight employment data points for one company. As shown in Appendix 1, employment figures obtained through the survey process were preferred over those obtained via the company files or the CTM database. If, however, no employment figures were available from the survey or the company's file for 1996 or the June 1996 to July 1997 period, CTM database values were used. Mode1 Calibration Daily Flow Coefficients and BOD and TSS Pollutant Concentrations Industrial sewer demand forecasts rely on per employee flow coefficients, BOD and TSS pollutant concentrations, and manufacturing sector employment. The 'driving' variable in the model is manufacturing sector employment within a particular sewerage area. The 'forcing' variables, on the other hand, include per employee flow coefficients and BOD and TSS pollutant concentrations for the same sewerage area. The product of the sewerage area-specific per employee daiIy flow coefficient, and the estimated or projected ernployrnent for the sewerage area, yields the total daily industrial flow for that sewerage area. Further, multiplying total daily flow by the BOD or TSS pollutant concentration for the sarne sewerage area, produces an estimate of the total daily industrial BOD and TSS loadings at a specified WWTP. In order to calibrate, or fit the model, forcing variables were adjusted to reflect the conditions that were observed in GVS&DD in 1995, the only year for which comprehensive industrial sewer demand data exists for individual sewerage areas. GVS&DD does not disaggregate sewer demand. Therefore, no historical customer- specific demand profiles exist, with the exception of 1995 when source control conducted a system-wide wastewater inventory. Ln the absence of additional observed data, the model has been 'fitted' to 1995 inventory data. To fit the model to 1995 conditions, flow coefficients and pollutant concentrations were adj usted using correction factors. Correction factors were required to correct the discrepancy between actual 1995 total industrial flow and pollutant loadings, and the projections generated by the model. In the adjustment process, sewerage area-specific flow coefficients and pollutant concentrations were multiplied by selected factors that resulted in 1994 total daily industrial flow and pollutant loadings being slightly less than 1995 levels, and 1996 values being slightly higher. The degree to which calculated sewerage area flow coefficients and pollutant concentrations required adjustment varied fkom one sewerage area to another (table 12). Table 12 Industrial Flow Coeificients, Pollutant Concentrations and Correction Factors 1 1 ~aiiv~er I 1 1 Correction- ~ Factors ~mdo~ee Daily Per Sewerage Area FI- PODI [T'SI (mQn) ~mployee coefficient (mon) Flow Pool [TW (umplda~) Coefficient Vancouver 746 1,293 524 0.125 0.990 0.930 I Fraser 841 42 1 213 0.080 0.330 0.450 It 1 North Shore 1 568 1 96 1 86 1 0.040 1 0.230 1 0.055 Lulu Island 570 45 1 166 0.250 0.600 0.350 West Northwest 755 427 228 0.200 0.900 Langley 0.600 The need for correction factors to fit the model serves to illustrate the limitations of the assumption that al1 manufacturing sector employees contribute equal flow and pollutants to the sewer system. Clearly, not al1 of the people employed in the manufactunng sector, actuaIly influence industrial sewer demand. Office administrators and clerical staff do not oRen affect the arnount of wastewater discharged fkom an industrial operation. Hence, on a per employee basis, we do not expect al1 manufacturing sector employees to contribute wastewater discharges of equal quantity and quality. Moreover, flow coefficients and pollutant concentrations derived in this study were calculated from Company data collected fiom significant industrial dischargers-those companies which impact regional sewerage facilities substantially. ln this way, the wastewater characteristics of this exclusive group of companies are not likely to be representative of the industrial sector as a whole. Wastewater monitoring data for al1 industrial enterprises in GVS&DD were not available; source control waste discharge permits are issued only to companies that discharge large volumes of wastewater, or wastewater classified as restricted waste. This policy necessarily omits industrial operations that discharge either smaller wastewater volumes, or wastewater with less contamination. The precise cumulative impacts of these 'small ' discharges is largely ignored; GVS&DD estimates that currently permi tted companies account for approxirnately 80% of total industrial wastewater discharges (GVRD 1997a). Landfill Contributions The landfill sector's daily flow coefficient was not assigned the usual per employee unit of measure due to the poor relationship between employment and flow in these operations. Instead, a flow volume with literdday nits were used for this sector. Ln accordance with this convention, sewerage areas with one or more landfills in their drainage basin simply received an appropriate percentage of the total land fil1 flow value. There are three landfills in GVS&DD. Two discharge into the fraser sewerage area and one discharges into the north shore sewerage area. The model includes an adjustable parameter value that assigns a proportionate percentage of the total landfill flow value, based on the number of landfills within the particular sewerage area of interest. Model Verification The objectives of the model were to forecast industrial flow and loadings to each of the district's 5 MPsduring the forecasting horizon. The model was evaluated to determine if it was functioning as designed. The evaluation process confirmed that calculations performed by the model are done so according to the conceptua1 hework outlined earlier in this chapter (fig. 6). Thus, for a given level of friture industrial employment- derived fiom GVRD Growth Management Strategy (GMS) municipal employment forecasts-a forecast of industrial sewer demand is generated for each of the 5-year time intervals throughout the forecast period. Also, total industrial sewer demand is divided into total daily industrial flow, BOD, and TSS. In addition, the mode1 structure allows scenarios to be simulated and evaluated. Hypothetical scenarios involving changes to: the spatial distribution of rnanufacturing sector empioyment; quaiity or quantity of industrial wastewater within a sewerage area, or industry subsector; or the level of manufacturing sector employment in the entire region, can be simufated. Baseline Results Projections of baseline industrial wastewater flow and loadings within each sewerage area are presented below (table 13). The Annacis Island plant, which serves the FSA, showed the most dramatic growth in flow and loadings, while the Iona Island plant, which serves the VSA, actually showed a decrease in total industrial flow and loadings. Table 13 Baseline Forecast: Industrial Flow and Loadings - --- - Industrial Flow and Losdings Under GVRD Growth Management Scenario % Change Sewerage Ama Parameter 1995 2001 2006 2011 2016 2021 (1995 - 2021) Flow (m3lday) 40.086 47.984 54.653 ] 54.985 58.486 59.666 49 Fraser 'BOD(kg/day) 18.620 20.223 23.033 1 23.173 24.649 25.146 35 TSS (kglday) 8,783 10.215 11.634 11.705 12.450 12.701 " 45 Flow (m3lday) 3.500 4.432 4,632 4.758 4.921 5.069 45 Lulu Island West BO0 (kglday) 1.652 1.997 2.087 -' 2.144 2.218 2.284 38 TSS (kglday) 509 735 768 789 816 840 65 Flow (m3lday) 4.136 4,204 4.590 4.646 4.867 4.952 20 North Shore BOD (kdday) 406 406 443 448 470 478 18 TSS (kgfday) 339 361 394 399 418 425 25 Flow (m3lday) 960 1,052 1,202 1.210 1.289 1,316 37 Northwest Langley BOD (kglday) 437 449 514 51 7 551 562 29 TSS (kglday) 233 240 274 276 294 300 29 Flow (m3lday) 19.293 20.538 , 20.921 , 21,581 22.102 22,894 19 Vancouver BOD (kglday) 24.822 26,557 27.052 27,905 28.579 29,603 19 TSS (kglday) 9,992 10.758 10,958 1 1.304 11.577 11.992 20 Flow(m3lday) 67,975 78,209 85,998 87,179 91.W 93.896 38 GVS6DD BO0 (kg/day) 45,938 49.632 53.129 54.188 56.466 58.073 26 J TSS (kddayl 19.856 22.308 1 24.029 24.473 25.555 26.259 32 Baseline forecasts of flow and loadings, at 5-year incrernents fiom 2001 to 2021, were calculated based on Growth Management Strategy asswnptions about employment and the assumption that industrial wastewater quality will not change fiom current levels. Total GVS&DD flow-a summation of the flow fiom the 5 WWTPS-is forecast to increase frorn 67,975 m3/day in 1995 to 93,896 m3/day by 2021, a 38% increase. The FSA and LIWSA are forecast to see the largest percentage increases in industial flow49% and 45% respectively-between 1995 and 2021. Industrial flow in the NSSA and VSA are forecast to increase by only 20% and 19%, respectively, over the same time period. Between 1995 and 2021, industrial BOD and TSS loadings are forecast to reflect the characteristics of flow projections. The Annacis Island plant, which serves the FSA, is projected to see 35% increases in industrial BOD and 45% increases in TSS loadings through the forecast horizon. Industrial TSS loadings are projected to increase 65% in the LIWSA, rising from 509 kg/day in 1995 to 840 kg/day in 2021. Discussion Although the forecasts are not definitive, they provide an idea of the level of industrial contributions to wastewater flow and loadings over the next 2 decades. The baseline forecast indicates that industrial flow and loadings to al1 5 treatment plants will increase 1 8% to 65% between 1995 and 202 1, depending on the treatment plant. However, total employment in the region is expected to increase approximately 85% over the same period. This observation is consistent with the prediction that industrial activity, and therefore industrial employment, in the region is expected to increase at a decreasing rate leading up ta 202 1 (GVRD 1993a: 5). in addition, growth in manufacturing sector employment is forecast to be the lowest among a11 sectors over the next 25 years. Assuming that model parameter values are correct throughout the forecast horizon, the model can be used to generate industrial dernand forecasts for al1 5 treatment plants at 5- year intervals through 202 1. In addition, it cm be used to conduct simple scenario analyses to answer "what if. . ." questions. Model Applications Scheduling facility upgrades and expansion projects to coincide with demand requires a reliable forecast. Without such a tool, financial and environmental costs can accrue. The baseline forecast presented in table 13 provides estimates of industrial sewer demand for each WWTP at 5-year intervals through 202 1. Uncertainty in the baseline forecast exists, thus, al1 forecasts must be interpreted with this in mind. However, the implications of a reliable forecast are noteworthy. Currently, GVS&DD treatment plants are designed according to standard engineering design principles. Average dry weather flow (ADWF) is calculated by multiplying a per capita flow coefficient by projected population. Peak wet weather flow, which detemines maximum plant capacity, is calculated by multiplying ADWF by a peaking factor. The peaking factor can Vary, but usually assumes a value between 1.5 and 2.0. WWTP design parameters are therefore broad estimations at best. Rapid and unequally distributed growth throughout the region highlights the limitations of this generalized approach to system planning. The mode1 developed here can help refine the estimate of future sewer demand by identifj4ng the magnitude, characteristics, and timing of industrial sewer demand, and thereby improve GVS&DD's ability to accurately schedule expansion projects. The results of which include, project financing cost savings fkom well timed borrowing, improved WWTP plant performance, and improved receiving water quality-a consequence of adequate treatment capacity being available when and where it is needed. Assumptions and Limitations As with any model, the industrial sewer demand mode1 relies upon a number of key assumptions. Below are a List of model assumptions and a discussion of the influence that each has on model outputs. Assumption 1 Manufachuing sector employment data can reasonably be used as an indicator of industrial activity. The model uses manufacturing employment as a predictor of industrial wastewater flow and loadings. nie assumption is that industrial employment provides some ineasure of economic activity and that wastewater flow and loadings are directly correlated with the level of regional economic activity. However, as discussed in the section on model calibration, correction factors were required to ensure that model forecasts 'fit' actual 1995 flow and loading data. Therefore, employment figures were correcteci in order to yield reasonable model outputs. The model is consequently limited by its reliance upon industrial employment to predict wastewater flow and Ioadings. Industrial production is considered a superior indicator of industrial water use and wastewater discharges (PMCL 1996: 43). The use of industrial employment as the sole predictor of flow and loadings assumes that productivity-the amount of output per ernployee-remains constant through time. If flow and loadings are predicted more accurately using production figures, the mode1 would benefit fkom the inclusion of expected productivity levels which would convert industtial employment into production levels. An understanding of how industrial productivity is likely to change over time would likely benefit model accuracy. Researching or developing productivity indices is not included in the scope of this study. However, in order to demonstrate the influence that such an index might have on model outputs, productivity indices for the textile manufacturing category were used to adjust industrial employment in the Fraser Sewerage Area (figures 7 & 8). Figure 7 Influence of Productivity Indices on FSA Daily Industrial Loading Forecasts FSA Oaily BO0 and TSS Loadings: Influence of Producthrity Indkes +800 (Emp) +TSS (-PI ,800 (Emp x PL) +TSS (Emp x P.I.) Figure 8 Influence of Productivity Indices on FSA Daily Industrial Flow Forecasts FSA Daily Fkw: lnfhrence of Pmducthriîy Indices Including the textile manufacturing productivity index in the mode1 caused industrial flow and loadings to increase 17% by 202 1. Assumption 2 Industrial wastewater âata included in GVS&DD7s1995 inventory project are completely accwate. Inventory data included in GVS&DD's 1995 inventory project were subject to quality control procedures (GVRD 1997a). Further, the inventory included data for al1 industrial permittees in the region, and therefore can be considered comprehensive. For these reasons, 1995 serves as a good 'control' year against which forecasts can be adjusted. No additional industrial flow and loadings data exist which means that 1995 data must serve as the lone 'control' point for model 'fitting'. Calibrating the model to a single data point-1995 inventory data- biases model outputs and does not allow for the inclusion of short- or long-term historical trends in the model forecast. Assumption 3 Correction factors used to adjust dai1y per employee fïow coefficients and poiiutant concentrations to fit 1995 ‘contrai' âata account for the discrepancies ôetween, a) the wastewater quantity and quality of perniitted indushial operations, and b) wastewater quantity and quality of aii manufacturing sector enterprises combined-which include pemiitted and unpermitted soukes. GVS&DD has defined the industrial sector as including all companies to which waste discharge permits have been issued (GVRD 1997a). However, the nurnber of people employed by permitted companies in the district is a fraction of the number employed in the larger manufacturing sector-the sector for which employment forecasts are available. Correction factors are therefore needed to relate manufacturing sector employment to characterizations of industrial flow so that when the two are multiplied, results show consistency with 1995 data. Without additional data to serve as 'control', there is no way to determine how reliable the correction factors are. An analysis of the impact of uncertainty in estimates of correction factors illustrates the degree to which model outputs rely on these parameters (figures 9 - 17). Ctystal Ball, a forecasting and nsk analysis computer prograrn, was used to conduct an analysis of the impact of uncertainty in correction factor estimates. Three simulations were conducted using standard deviations of IO%, 20%, and 30%, respectively. In this way, uncertainty in correction factor estimates were incorporateci into simulation results. A normal distribution was assurneci for each correction factor, and 2,000 trials were nin to complete each simulation. Simulated forecasts for flow, BOD, and TSS for each 5-year time interval were generated. The graphs include bands which represent the certainty ranges into which the actual values of the forecasts fall. The band that represents the 90% certainty range shows the range of values into which a forecast has a 90% chance of falling. Results of these analyses show that the range in forecast values, regardless of the certainty level, does not vary greatl y. Only the size of the range increases wiîh larger assumed standard deviations. Figure 9 FSA Industrial Flow: 90%, 50%, and 25% Certainty Ranges & 10% S.D. - -- - -- FSA Industrial Flow - 10% Std. Deviation 85.000 Cerîainties Centered on Medians -- Note: y-axis units are 'm'/day' Figure 10 FSA Industrial Flow: WOA,50%, and 25% Certainty Ranges & 20% S.D. - - -- FSA Industrial Flow - 20% Std. Deviation -- 2006f 2011f 2016f Certainües Centered on Medians Note: y-axis units are 'm3/day' Figure 11 FSA Industrial Flow: 90%, 5076, and 25% Certainty Ranges & 30% S.D. FSA Industriai Flow - 30% Std. Deviation ----- Certainües Centered on Medians ----. Note: y-axis units are 'm3/day' Figure 12 FSA Industrial BOD: 90%, 50%, and 25% Certainty Ranges & 10% S.D. -- -- FSA Industriai BOD - 10% Std. Deviation 40.000 - - Note: y-axis units are 'kdday' Figure 13 FSA Industrial BOD: 90%, 50%, and 25% Certainty Ranges & 20% S.D. 1 FSA Industriai BOD - 20% Std. Deviation 1 Certainües Cenlered on Medians - -A Note: y-axis units are 'kdday' Figure 14 FSA Industrial BOD: 90%, 5074, and 25% Certainty Ranges & 30% S.D. FSA Industriai BOD - 30% Std. Deviation - Note: y-mis unit5 are 'kglday' Figure 15 FSA Industrial TSS: 90°h, 50%, and 25% Certainty Ranges & 10% S.D. - FSA Industriai TSS - 10% Std. Deviation 20.000 Cerlainties Centered on Medians . ------Note: y-axis unit~are 'kg/dayl Figure 16 FSA Industrial TSS: 90%, 50%, and 25% Certainty Ranges & 20% S.D. FSA Industrial TSS - 20% Std. Deviation 30.000 -- CefiainCies Centered on Medians Note: y-ais units are 'kg/day' Figure 17 FSA Industrial TSS: 90%, 50%, and 25% Certainty Ranges & 30% S.D. ----- 1 FSA Industrial TSS - 30% Std. Deviation 1 Certainties Centered on Medians Note: y-mis units are 'kg/day' Assumption 4 The employment forecasts contained in GVRD's Gmwth Management Strategy are reasonable projections of riitme levels of employment in the region, and consequently, economic activity in the region. Growllt Management Strafegy employment forecasts provided b y GVRD reflect objectives contained in municipal OCPs, and therefore, can be considered reliable. The model relies upon these data to calculate total regional industrial employment. Total regional industrial employment is distributed among GVS&DD municipalities to calculate industrial flow and loadings for each sewerage area. The sensitivity of mode1 outputs to changes in Growth Management Strategy (GMS) projections for total regional employrnent was tested. Total regional employment estimates were adjusted upward, 5% and 1076, and downward, by equal increments. Results (figures 18 - 20) indicate that 2021 model outputs for daily flow, BOD, and TSS loadings fluctuate +/- 1 1% &om the baseline GMS outputs. This level of variability represents under and overestimates of daily flow, BOD, and TSS loadings equivalent to 5,090 m3/day, 2,145 kg/day, and 1,084 kg/day, respectively. Moreover, industrial flow projections for the Annacis WWTP in 2021 can range between 47,000 m3/day and 58,000 m3/day if total regional employrnent levels turn out to be 10% more or less than the current GMS forecast values (fig. 18). Also, daily BOD loadings cmrange between 20,000 kg/day and 24,500 kg/day (fig. 19), and daily TSS loadings can range between 10,000 kg/day and 12,500 kglday, if actual levels are +/- 10Y0 of GMS forecasts (fig. 20). Mcdel outputs are indeed sensitive to enors in GMS employment forecasts and vary proportionately with fluctuations in total regional employrnent forecasts. Figure 1% Fraser Sewerage Area: Flow Sensitivity to Errors in GMS Employment Projections Figure 19 Fraser Sewerage Area: BOD Sensitivity to Errors in GMS Employment Projections Figure 20 Fraser Sewerage Area: TSS Sensitivity to Errors in GMS Employment Projections Assumption 5 Percentages rep-ting the ratio of manufâcturing sector employment to total regional employment in 2006 and 2021, as forecast by The Urban Futures Institute, are ~easonable projections of fbture conditions in the =@on. Table 14 Percentage of Regional Employment Contributed by Manufacturing Sector (Estimates and Projections) In 199 1, the manufacturing sector accounted for 1 1.1% of total regional employment. By 1996, this figure dropped to 10.2% (table 14). Further changes are forecast for the region's employment profile over the next two decades. Growth in the service sector is expected to account for an increasing share of total regional employment, while the manufacturing sector is expected to show an overall decrease in size over the same period, dropping to 8.4% by 202 1. These are key assumptions upon which the mode1 relies. To test the impact of these assumptions, predicted percentages were adjusted upward in two increments- 0.5% and 1 .O%-and downward in increments of similar magnitude. The results show that modet outputs are sensitive to changes in the projected values for the percentage of total regional employment contributed by the industrial sector (figures 21 - 23) in 2006 and 202 1. As shown, the corresponding changes in daily industrial flow, BOD, and TSS loadings, resulting from a 1.0% under or overestimate are, 6,059 m3/day, 2,553 kg/day, and 1,289 kg/day, respectively. As a percentage of the flow and pollutant loadings expected under the Growth Management Stmfegy conditions, these results differ by approximately +/- 12%. Figure 21 Fraser Sewerage Area: Flow Sensitivity to Changes in 2006 & 2021 Industrial Employment Percentage Projections Figure 22 Fraser Sewerage Area: BOD Sensitivity to Changes in 2006 & 2021 Industrial Employment Percentage Projections Figure 23 Fraser Sewerage Area: TSS Sensitivity to Changes in 2006 & 2021 Industrial Employment Percentage Projections Assumption 6 Future distribution of total regionai industriai employment among GVS&DD municipalities continu& to reaect 19% patterns. The model assumes that the level of employment contnbuted by the industrial sector within a rnunicipality will remain constant through time. Percentage values for 1996 (table 14) are applied to each 5-year tirne interval in order to apportion total regionai industrial employrnent into sewerage areas. As show in table 15, the percentage values for the FSA rose 12.3% between 1991 and 1996 while the remaining sewerage areas experienced less dramatic changes. Fixed percentages are used in the model due to the lack of information regarding future industrial employment distribution patterns. Understanding the uncertainty associated with this assumption is important as industrial wastewater discharges will undoubtedly change in response to shifts in location of employment. Yet, the answer to this question lies outside the scope of this study, and therefore, is not addressed. Table 15 Distribution of Regional Industrial Employment Within Sewerage Areas Percent of Regional Industrial Employment Located in Sewerage Area Sewerage Area Lulu Island West 16.3% 16.4% 7.5% North Shore 5 -2% 5.9% 6.3% Northwest Langley 1 1.2% 1 1.2% 1 1.5% Assumption 7 For the purposes of characteripng industry sector wasttwater, the inclusion of some 'nonsignificant' pdttddischargers to inctcase the size of the sectord âatabase, is reasonable and serves to impmve the overall characterization of an industrial sector's wastewater. Including data from al1 permitteci companies, rather than just companies designated 'significant discharger', in the calculation of subsector daily flow coefficients and pollutant concentrations, improves the representativeness of these estimates. The influence of extremely high flow and concentration values, typical of significant dischargers, are offset by lower values observed arnong nonsigni ficant dischargers. The combination of the two data sets produces an average that incorporates the variability observed in subsector flow and pollutant concentration values. Assumption 8 Average concentrations of BOD and TSS in industriai wastewater will remah the same throughout the forecast horizon. The assumption that pollutant concentrations will not change over time means that total industrial loadings will be solely dependent on industrial flows. The validity of this assumption was not investigated in this study. However, the model includes a function that allows changes to pollutant concentrations to be incorporated into model forecasts. The role of changes in wastewater pretreatment levels over time as a result of regulation or economic incentives is acknowledged to effect average pollutant concentrations. However, investigation of the nature of the influence of these forces is outside the scope of this study. Summary The industrial sewer demand model relies upon several key assumptions. Understanding the degree to which model outputs may vary as a result of uncertainty in these model assumptions is vital to assessuig the accuracy of the forecast. The structure of the model is simple and therefore, it is easy to see the impact of assumption variability on outputs. In the preceding analyses, each assumption was examined separately, however, it is reasonable to expect that al1 assumptions will Vary simultaneously. Mode1 output uncertainty produced by adjusting single assumptions is signifiant as seen above. It is anticipated that the possible range in outputs will grow to an even greater Ievel if all model assumptions are allowed to Vary simultaneously. How wide the range of possible model outputs can be to still provide a reliable forecast will be up to the user to detemine. Chapter 5 - Model Application and Simulation As discussed in chapter one, the absence of a reliable forecast of industrial sewer demand contributes to increased sewerage service costs, violations of WWTP permit limits, environmental damage, and missed opportunities for evaluating demand-side management strategies. In this chapter, a scenario simulation demonstrates how the model can be used to mitigate these shortcomings, and ultimately enhance system management. The industrial sewer demand model can be used to run simulations. Model parameter values cm be altered conveniently to simulate the impacts of environmental and economic regulations, employment trends, technological change, and social policy, on forecast values. Moreover, costs and benefits resulting from these types of factors can be calculated and compared with the baseline forecast in order to evaluate relative impact measurements. However, interpretation of model simulation results must acknowledge the Ievel of uncertainty that each input parameter contributes to model outputs. Scenario Simulation In this scenario a source control policy that causes breweries in VSA and FSA to reduce their flow by half, while maintaing BOD and TSS concentrations at current levels between 2001 and 201 1, is run and evaluated. The anticipated results of this policy include reductions in fùture flow and loadings at the Iona Island and Annacis Island WWTPs. En implementing the policy, four objectives are met including: reduction in sewerage service costs; avoidance of permit limit violations; delayed expansion of treatrnent capacity levels at both plants; and, protection of receiving water quality. This simulation helps to illustrate how the industrial sewer demand mode1 can facilitate incorporation of GVS&DD financial, legal, and environmental objectives into liquid waste management planning. This scenario is plausible as it partially reflects an actual investigation that GVS&DD managers conducted into dramatic increases in BOD loadings at the Iona WWTP in 1997. A substantial increase in the number of BOD permit violations at the Iona plant in 1995 resulted in the plant being piaced on the provincial permit non-cornpliance list. This list is published biannually by the Province and identifies operations whose comp!iance reccrd during the reporting petiod was of concem to the ministry. A total of 25 BOD concentration exceedances were observed at the Iona plant between 1991 and 1995, 16 of which occurred in 1995. On the days when violations occumed, BOD loadings ranged from 68,000 kg/day to 107,000 kg/day. An audit of plant processes and a residential source study failed to explain the problem. A small nuniber of industrial operations in the Vancouver Sewerage Area were identified as probable contributors to the problem. Although the hypothetical source control policy used in this exercise does not reflect the actual outcome of the 1997 Iona investigation, it does represent a good example of the uses to which the industrial model can be put. Running this simulation demonstrates how the model can improve sewerage system management, and consequently, how expenditures, WWTP permit violations, and environmental darnage can al1 be avoided. In order to nin the scenario simulation, daily flow coefficient for the brewery subsector were reduced by half. FSA and VSA daily industrial per employee flow coefficients fkom 200 1 through 20 11 were updated to reflect these hypothetical changes to brewery subsector flow. BOD and TSS concentrations were maintained at current levels through 201 1, implying that in this scenario, the brewery subsector was able to reduce overall BOD and TSS loadings in such a way that concentrations remained constant. Industrial employment levels and distribution patterns were not altered as part of this scenario, although alterations to these two model components are possible. Simulation Results Unlike an aggregated sewer demand forecast, the industrial sewer demand model is capable of simulating the effects of changes that occur at the industrial subsector level. Examples of changes include: economic trends and shifis, increased or reduced labor costs, environmental or public health regulations, trade regulations, and financial incentives. O ften, changes such as these impact specific subsectors only, leaving other subsectors unaffected. The industrial sewer demand model allows the impacts, caused by a trend or change that does not impact uniformly across industrial subsectors, to be incorporated into a forecast. In this scenario, the brewery subsector is motivated by an unspecified trend or force to reduce its flow by half, and maintain its BOD and TSS concentrations at cwrent levels. The unspecified trend or force does not impact any other subsectors, thereby making this a highly probable situation. Service Cost Savings The resulting savings in flow and loadings, summed over ten years during which the hypothetical conditions prevail, are shown graphically (figures 24, 25). Tabulation of the results, including service cost savings, are shown in table 16. In addition, results show that both FSA and VSA are effected by the change in brewery subsector discharges due to the fact that the subsector contributes to total industrial flow and loadings in both sewerage Figure 24 FSA Flow: Baseline & Scenario Simulation Conditions - FSA Fkw (1995 - 2021) Figure 25 FSA BOD & TSS: Baseline & Sceaario Simulation Conditions ,- -- FSA BO0 & TSS (1 995 - 2021) Between 2001 and 20 11, reductions in overall industrial discharges are estimated to generate savings of 18,000 m3 of flow, 22,500 kg of BOD, and 9,800 kg of TSS. From GVS&DD perspective, these forecast reductions represent a cost avoidance. For every cubic meter of flow, or kilogram of BOD or TSS it is not required to treat, GVS&DD saves money. 1996 GVS&DD unit service cost estimates were applied in order to generate cost savings for both sewerage areas (GVS&DD 1996). The net present value of cost savings under simulation conditions is $1,860,530 (table 16). Table 16 Scenario Simulation Results The cost of having the brewery subsector reduce its flow and pollutant concentrations, although not specified in this scenario simulation, may then be compared to the $1.9 million cost savings expected under these conditions. For example, if the brewery subsector was motivated to reduce its discharge by a GVS&DD demand-side management (DSM) policy, the cost of the DSM initiative could be compared with projected savings in order to gain a better understanding of the ments of such a policy. Ln the event that projected gains were sufficiently large, GVS&DD may elect to subsidize industry's efforts to reduce flow and loadings instead of investing in traditional supply options. Similar examples of DSM have occurred in the power supply sector, resulting in cost savings fiom delayed construction of power generating capacity. The scenario simulation summarized in table 16 serves to illustrate the way in which the industrial sewer demand mode1 can be used to evaluate the costs and benefits of a DSM strategy. The ability to evaluate DSM service strategies is important to GVS&DD as the district cm no longer satisQ increased demand by simply building more treatment capacity. Rationalization of inhtnicture budgets, projected increases in regional population, and increasingly stringent environmental regulations, mean that paying for an endless supply of end-of-pipe treatmmt capacity will no longer be financially, politically, or practically feasible. Simulating the effects of new strategies will undoubtedly be needed and the industrial sewer demand model cm faciiitate this undertaking. lmproved Permit Corn pliance GVS&DD wastewater treatment plants are permitted by the provincial government under the BC Wuste Management Act. Each treatment plant must observe permit limits for the volume of effluent it discharges, as well as the maximum concentrations and daily loadings permitted for BOD and TSS. Plant staff monitor effluent quality daily and provincial regdators review the results. Plant effluent quality that exceeds permit limits constitutes a violation of the permit. Sadly, GVS&DD has Iacked the ability to predict, or manage sewer demand before it is discharged by the industrial sector. By the time industrial wastewater arrives at a treatment plant, it is too late to respond. In this way, GVS&DD has been forced to only react to changes in industrial sewer demand, rather than manage it, resulting in fiequent permit violations. The ability to aim for, and ultimately cause, reductions in flow, BOD, and TSS loadings represents an opportunity to avoid permit violations, and is therefore a tremendous improvement over current management practices. Simulations that show reductions in indusûial flow, BOD, and TSS can demonstrate the potential impact that various policies or regulations might have on the fiequency of permit violations, and thereby support implementation of such policies and regulations. Delayed Expansion of Treatment Capacity In the same way that the model can illustrate improvements in permit compliance resulting fiom various policies or regulations, it can also be used to identifjr opportunities for delayed capacity expansions. Financing large projects is often extremely expensive. The ability to delay financing costs represents a financial gain to GVS&DD. Yet, understanding the degree to which expansion projects can be delayed relies on a reliable forecast of demand. The reductions in industrial flow, BOD, and TSS, shown in the simulation, reflect a reduction in industrial sewer demand and ultimately, a possible delay in terms of the need for an increase in treatment capacity. It is unlikely that the GVS&DD policy used in this scenario would be sufficient to cause a major expansion project to be delayed. However, larger, farther reaching policies may well have the force to dampen industrial demand below the level which would otherwise require an expansion of treatment capacity. Again, the industrial sewer demand model can be used to simulate the impacts on capacity requirements that various policies and regulations might have, and thereby give an idea as to the possible financing savings that might result. Protection of Receiving Water Quality GVS&DD treatment plants discharge contaminants into the Fraser River, Burrard Inlet, and the Straight of Georgia Unfortunately, emuent f?om WWTPs have been identified as major contributors to the degradation of these local waterways. This is due partly to GVS&DD's inability to forecast what level of industrial flow and contaminants are Wcely to corne down the pipe at any given time. Each plant has a limited treatment capacity. When this capacity is exceeded, wastewater is inadequately treated, effluent quality is reduced, and environmental damage results. With respect to protecting the quality of these waterways, it is assurned that permit limits imposed on emuent fiom GVS&DD treatment plants are sufficieot to ensure that water quality is maintained. Therefore, accurately forecasting industrial sewer demand will provide managers with an opportunity to effectively manage industrial wastewater, before it amives at the treatment plants, in such a way that WWTPs are better able to remain in compIiance with permit limits. In this way, improved receiving water quality can be realized. AIthough not likely to occur in the near tùture, the scenario descnbed here nonetheless serves to demonstrate one application of the industrial sewer demand forecasting model. Similar exercises cmbe conducted whereby the effects of industrial water conservation measures, or sharp declines in the economy, are evaluated to detemine the relative impacts of these large scale events on industrial flow and loadings at the region's WWTPs Chapter 6 - Conclusions and Recommendations This study investigates the applications and limitations of an industrial sewer demand forecasting model in an effort to improve management of the GVS&DD sewerage system, and ultimately enhance receiving water quality. Conclusions and recommendations £iom this study are based on: a review of forecasting methodologies employed in other Canadian municipalities; analysis of historical and current industrial wastewater characteristics, both in and outside of the GVSⅅ analysis of the precision and accuracy of the model; analysis of model assumptions; and results of a scenario simulation exercise. This final chapter describes the state of current forecasting techniques and the impetus for reliable industrial sewer demand forecasting; summarizes current model applications; identifies model deficiencies with respect to its reliability; describes to what extent sewerage system and environmental imperatives may be able to control and direct industrial sewer demand; and provides recommendations for further research. Conclusions Current State of Industrial Sewer Demand Forecasting The conclusions fiom a survey of Canadian municipalities and Seattle, Washington, are that accurate sewer demand forecasting is rare. instead, total sewer demand is calculated based on per capita flow coefficients and a forecast of total population. However, most survey respondents indicated that they saw a benefit to having a reliable, and disaggregated, sewer demand forecast, and that the absence of such a forecast was due mainly to the absence of a forecasting tradition. Of those surveyed, Seattle, Washington, is the only city that generates a separate forecast for industrial sewer demand, yet this forecast is not disaggegated to the subsector level. Although not common today, reliable and disaggregated industrial sewer demand forecasts are showing signs of becoming increasingly important to effective management of sewerage systems. increased demand for limited treatment capacity, strong public demand for environmental protection, and continued government cutbacks, are revealing the benefits of such a forecasting tool to utility managers across North America. In addition to the need for an accurate forecast of industrial sewer demand, there are clear signs that an ability to evaluate both conventionai and alternative supply strategies, capable of meeting that demand, is also important. Model Applications The forecasting model developed in this study relies on the assumption that industrial dernand for sewer senices is duectly related to industrial employment. Per employee flow coefficients, BOD, and TSS concentrations for each industrial subsector, and for each sewerage area, can be multiplied by industrial employment to generate forecasts of industrial flow and loadings at 5-year intervals through 202 1. The model produces a baseline forecast of industrial wastewater contributions to each of the district's five wastewater treatrnent plants. This forecast provides an idea as to the magnitude of future industrial sewer demand in the region. GVS&DD managers can examine the forecast to identiQ changes in industrial demand for sewer services through time. Significant uncertainty, discussed in the next section, means that forecasts must be used with caution. A disaggregated model structure, compnsed of 27 unique industrial subsectors and 5 sewerage areas, allows GVS&DD managers to adjust subsector level model parameters during simulations. Consequently, simulations are better able to incorporate the impacts of both small- and large-scale factors that alter industrial sewer demand. Although littte reliance can be placed on simulation results, they do provide a range of possible forecast values within which a user can be assured the tnie value will fall. It is then up to the user to determine what level of uncertainty he or she is willing to accept. Depending on the acceptability of model forecasts, scenario analyses can be conducted to determine the resulting impacts on model outputs. This capability represents a substantial benefit to sewerage system managers as it allows alternative service strategies to be evaluated based on a common measure. Model Limitations Model use is limited by the absence of complete historical data. A lack of data on historical industrial flow and loadings received at district WWTPs means that model verification is impossible. The only year for which industrial flow and loadings were inventoried, and for which industrial employment data exists, is 1995. As a consequence, model calibration relies on 1995 as the sole control point. Further, historical trends are not incorporated into the baseline forecast and extrapolations into the future are impossible. Analysis of the impacts of parameter uncertainty reveals wide ranges in possible forecast values. Assuming a moderate degree of uncertainty in parameter values-standard deviation of 10%-the 90% certaine range includes values between +/- 17% of the forecast mean. Additional forecast uncertainty is caused by a lack of idormation regarding the reliability of the assumption that employment is an accurate determinant of industrial activity. Without a better understanding of the relationship between industrial employment and industrial activity, or output, the use of industrial employment alone to detemine industrial flow will be in doubt. Deviations fiom the asswned direct relationship between industrial employment and wastewater flow have the potential to significantly distort forecast values. Although the model has the capacity to incorporate user-specified changes in industrial wastewater characteristics over time, it makes no attempt to predict these values. Baseline forecasts assume that curent industrial flow, BOD, and TSS levels remain constant. Mode1 forecasts will remain in doubt until the validity of these assurnptions are confimed. Inconsistencies between the geographical boundaries of sewerage areas and standard Statistics Canada enumeration areas, used for employment forecasts, necessitated significant data manipulation to allocate employment to municipalities within specific sewerage areas. Such manipulations, no matter how carefiilly performed, also contribute to model error, Merlimiting its use. Sewerage System Management and Environmental Quality As discussed in chapter 1, the needs of industry, together with the needs of the commercial and residential sectors, have traditionally determined wastewater flow and loadings in GVS&DD. District wastewater treatment plants have historically been forced to accept what wastewater flowed their way, removing as much of the harmhl pollutants as possible, prior to discharge to the receiving environment (fig. 2). This situation has resulted in a reduced capacity to plan for, and manage, fùture demand, increased service costs, and damage to receiving waters. A reliable industrial sewer demand model could help GVS&DD to better understand, and there fore, manage fûture industrial wastewater flow. However, the limitations of the industrial sewer demand model, outlined above, mean that GVS&DD still does not have a reliable forecast of industrial demand. Consequently, the industrial sewer demand model fails to help GVS&DD managers achieve the desired structural form (fig. l), as hoped. Instead, an interim fom (fig. 26) characterizes where GVS&DD is with respect to sewerage system management and environmental quality. The diagram in figure 26 includes the industrial sewer demand model as a component. Although, as depicted, information is generally flowing into the model. One exception is the double-headed arrow between the rnodel and source control. This feature recognizes that GVS&DD's Source Control Division currently uses the model to simulate sewer policies and regulations. However, simulation results produced by source control staff acknowledge the high level of uncertainty inherent in model forecasts. In its current state, the industrial sewer demand model is not capable of accurately forecasting industrial sewer demand. Therefore, the structure of figure 26 lies somewhere between a sustainable management fonn (fig. 1) and the historical management form (fig. 2). Until enough data are compiled and added to the model, the situation depicted in figure 26 will persist. Industry and the other two sectors will continue to detemine total sewer demand; treatment capacity will continue to be sized and built based on broad, and often expensive, design principles; opportunities to exploit demand-side management opportunities will be missed; and the quality of receiving waters will continue to suffer. GVSIDO UNSURE O DEMAND, AMOUNT OF CAPACiTY TO BUILD, & WHEN TO BUILD iT IN ORDER TO PROTECT RECEMNG WATER QUALITY. Direction of infornion. policy ador rcguluion Figure 26 Management framework for sewerage system management and protection of receiving water quality after addition of industrial sewer demand model. Pressure on sewer services will undoubtedly continue in GVRD as the region's population continues to grow. Whereas in the past there was little incentive for sewer utilities to differentiate between individual customer groups in demand forecasts, recent expenence shows that sewer use by the residential, commercial, and industrial sectors is highly variable and worth a closer look. The industrial wastewater forecasting model examines the industrial sector in GVRD as a distinct and quantifiable user group. For a given year, it generates a forecast of the magnitude of industrial flow, BOD, and TSS loadings, based on estimates of industrial employment and industrial wastewater quality within a sewerage area. The incorporation of additional data over time will serve to improve the accuacy of the model. Until more information is obtained and incorporated into the model structure, forecasts can continue to be used in the decision making process, but only with the understanding that model outputs remain approximations of real world conditions. Recommendations A lack of histoncal industrial employrnent and output data currently limits the use of the industrial sewer demand forecasting model. The benefits of a reliable industrial sewer demand forecast illustrate the need for these data, yet the cost of collecting employment and output data is unclear. It is therefore recommended that the cost of industrial employment and output data collection be calculated. Further, these costs should be compared to potential benefits arising fkom a reliable forecast. If this analysis concludes that the benefits of data collection exceed the costs, it is recommended that data collection be coordinated by municipalities in GVS&DD. Data collected should be added to the industrial sewer demand mode1 to improve its accuracy. Appendix 1: lndustry Subsector Characterizations rvYW 1iM -'- (IdzzzL z,z y--= LI* "8, '"1 z,*;((t:-1 ,", 111 1") I", 1 II Il..., -w*- .Y-- ------ Pu.l mi -1-d - I 1 I mi 1 1 III œYI.cu3-a tiInl.l.l.l.l r0*1*0w r .roio*rolhil. 1 Irc)w*r*rocn-v 1- 1- 1-1 no-cc.~ (dm- IW t 111 II am ).II tw mu IYL YI *~--I19 lll\lGM R.I..~v --v &':: '.y (LI 11~1*~vt~mwmn el* Ml 1 ---il I I I 1111 ta I 01 ,ni *mctinrra~i amtarnircmurm.~~ WWO~M 1It .ra owo Wt ~rc)-nt..wrv J e0e~o~gpue Bu(snoye~e~peie~e0t~p~ IntlNI I I III I I 1 I 1 ! !!!!!I m I I 1 t ; * -1, 1 ici ; i 1 1 I II--* Appendix 2: lndustrial Sewer Demand Model Input Sheet GVSDD Industrial Wastewater Forecas!lnq Model- Output Sheet I SIwrnga Anis Industdal Florn and Lordlnps undrt GVRO Grmlh Manr~mrnlSwnirlo References Arnold, David S. 1979. The Practice of Local Government Planning. Washington, D.C.: The International City Management Association. Barnes, D, C.F. Forster, S.E. Hrudey, Eds. 1984. 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