A Preliminary Study on Potential of Developing Shower/Laundry Wastewater Reclamation and Reuse System

Chemosphere 52 (2003) 1451–1459 www.elsevier.com/locate/chemosphere

A preliminary study on potential of developing shower/laundry wastewater reclamation and reuse system

Weizhen Lu *, Andrew Y.T. Leung

Department of Building and Construction, City University of Hong Kong, Kowloon, Hong Kong, HKSAR, PR China

Abstract

With the ever-increasing urban population and economic activities, water usage and demand are continuously increasing. Hence, finding/re-creating adequate water supply and fully utilizing wastewater become important issues in sustainable urban development and environmental benign aspect. Considering Hong KongÕs situation, e.g., lack of natural fresh water, domination of municipal wastewater, etc., developing wastewater reclamation and reuse system is of specific significance to exploit new water resource and save natural fresh water supplied from Mainland China. We propose and have carried out some preliminary studies on the potential of categorizing municipal wastewater, developing grey and storm water recycling system in public housing estate, investigating the feasibility and potential of using reclaimed grey water, etc. Since there is very limited experience in grey water recycling, such initial studies can help to understand and increase knowledge in utilizing grey water, to foresee the feasibility of developing new water resource, to estimate the cost-effectiveness of reclaiming grey water in metropolitan city. 2003 Elsevier Ltd. All rights reserved.

Keywords: Potable; Potential; Shower/laundry water; Water resource; Wastewater reclamation and reuse

1. Introduction densely populated international world-trading center (with population density of 6000 persons/km2) has suf- Water is a limited and, in the mean time, the most fered water shortage for most of its 160-years history. strategically important resource on earth (Spivy, 2002). Currently, the major single source of fresh water comes Water is essential for urban, industrial, and agricultural from Guangdong Province, Mainland China. Such needs. It is estimated that the consumption of fresh supply system can be traced back to 1960 when it was water by domestic usage takes up to 70–80% of the total ﬁrst formulated for receiving a supply of 22.7 million volume of wastewater globally (Harrison, 1999; Asano, cubic meters a year. It provides and annually increases 2002). Such ration in Hong Kong is even higher due to by 30 million cubic meters from 690 million cubic meters the migration of major industries further north to in 1995 to 840 million cubic meters in 2000. During Mainland China in recent years. Besides, Hong Kong 1986, water from Guangdong represented only about itself is almost totally lacking in natural water resources 52% of the total demand. In 1996, the annual supply has due to the hard granite base yields no appreciable un- been raised to 720 million cubic metres, which is over derground water and there are no sizable lakes or riv- 70% of Hong KongÕs demand. Such ratio keeps in- ers. Finding adequate water supplies has always been a creasing in recent years and the demand for fresh water problem for Hong Kong over the past 150 years. This is also raised continuously. Besides, since 1863, Hong Kong government has established series rainfall catchment reservoirs for collecting and storing the rainfall * Corresponding author. Tel.: +852-2784-4316; fax: +852- water as reservation, e.g., Pok Fu Lam reservoir 1863 2788-7612. (9000 m3 capacity), Wong Nai Chung reservoir 1899 E-mail address: [email protected] (W. Lu). (150 000 m3 capacity), Tai Tam Byewash reservoir 1904

(1.36 million m3 capacity), New Kowloon reservoir shower and laundry discharges to reuse level. The study 1906, Shek Lei Pui reservoir 1925, Kowloon Byewash aims to arouse the attention of relevant parties (both reservoir 1931, Tai Lam Chung reservoir 1957, Shek Pik official and social organizations) to promote and sup- reservoir on Lantau Island 1963, Plover Cove reservoir port the development and processing of municipal 1973 (170 million m3 capacity), High Island reservoir wastewater for reuse in Hong Kong territory. 1978 (281 million m3 capacity), etc. Although the com- pleted reservoirs can supply certain amount of fresh water to urban use, such resources are unstable and 2. Background information and previous studies uncontrollable due to the seasonal variations and the uneven distribution of rainfall. Hence, seeking and de- Population growing and scarcely increase of new veloping new water resources are significant to stabilize water sources have stipulated a variety of water man- the water supply and further improve the living standard agement measures during the last few decades, including in Hong Kong (WSD annual report, 2001). the processing and reuse of water for many purposes. In fact, to save the fresh (potable) water resource, These measures include the use of highly treated mu- Hong Kong has two water supply systems to comple- nicipal wastewater to augment and conserve the raw ment the daily urban needs. One is the fresh water water supply. Such investigation has special significance supply system for potable usage. The other is the sea to excavate the new water resource and improve the water supply system for flushing usage. As a metropo- built environment in metropolitan city like Hong Kong. litan city with the highest population density in the Wastewater utilization is closely related to the genera- world, the daily sewage amount generated by the com- tion, collection, transfer and transport, treatment, dis- munity exceeds 2.3 million cubic meters. Among this, posal and reuse of wastewater that is in accordance with domestic usage takes up 53%, non-domestic 21% (e.g., the principles of public health, economics, engineering hotel, hospital, schools, sports centre, etc.), restaurants conservation, aesthetics, and other environmental fac- 17%, government 4%, bleaching and dyeing 2%, food tors along with political constraints. It also encompasses manufacturing 1%, textile industry 1%, laundries 1%, see all administrative, financial, legal, planning, and engi- Fig. 1 (DSD annual report, 2001). It can be seen that the neering functions in solving problems related to waste- domestic and non-domestic wastewater mainly contri- water (Cheremisinoff and Cheremisinoff, 1993; NRC, bute to the sewage discharge in Hong Kong. These two 1998; Al-Sulaim and Asano, 2000; Bryan, 2000; Henze kinds of sewages provide large sources for reclamation et al., 2002). Problems associated with wastewater utili- and may be used as new water resources. The treated zation in todayÕs society are complex because of the wastewater, especially shower and laundry water after quantity and diverse nature of the domestic and indus- first usage of fresh water, is a valuable resource, which trial wastewaters generated. Wastewater discharges are can be available for secondary usage, and, if under good classified based on whether they are from municipalities purification, for potable purpose again. This article re- or industries (Burton and Stensel, 2002). In Hong Kong, ports a preliminary investigation and discusses the po- municipal wastewater dominates and is usually dis- tential of development of wastewater recycle system to charged from residences, commercial and institutional collect, filter, and purify domestic wastewater from facilities. Domestic water usage, and, the resultant wastewater, is affected by climate, community size, development density, community affluence, dependability and quality of water supply, and water conservation requirements or practices. Hence, any wastewater utilization programme should include the monitoring of the quality and quantity of wastes produced. Tables 1–3 show the typical wastewater flow rates from residential, commercial, and institutional sources in Hong Kong. It can be seen from these tables that large amount of municipal wastewater is generated daily from various users in Hong Kong. Among these users, 7 out of 13 sources (over 50%) contain shower/laundry activities. It can be seen that the unit percentages of shower/laundry discharge in residential, commercial, and institutional sources are quite high, e.g., the unit percentage of laundry in commercial source is about 53% to the total unit consumption of commercial usage, the unit per- Fig. 1. Distribution of water consumptions by sewage ac- centage of shower/laundry in institutional source achi- counting in Hong Kong (2001). eves about 80% to the total unit consumption, etc. W. Lu et al. / Chemosphere 52 (2003) 1451–1459 1453

Table 1 Table 3 Typical wastewater ﬂow rates from residential sources (DSD; Typical wastewater ﬂow rates from institutional sources (DSD; WSD annual report, 2001) WSD annual report, 2001) Source Unit Flowrate Source Unit Flow rate (l/unit, day) (l/unit, day) Range Typical Range Typical Apartment Hospital Bed (shower/ 473–908 624 High-rise Person (shower/ 132–283 189 laundry) laundry) Employee 19–57 38 Low-rise Person (shower/ 189–302 246 laundry) Prison Inmate (shower/ 284–567 435 laundry) Employee 19–57 38 Individual residence Typical home Person (shower/ 170–340 264 School, daily laundry) With cafe- Student (shower) 57–113 95 Better home Person (shower/ 227–378 302 teria, gym, laundry) shower Luxury home Person (shower/ 283–567 360 With cafe- Student 38–76 57 laundry) teria only Older home Person (shower/ 113–227 170 Without Person 19–64 42 laundry) cafeteria and gym Total 1531

Total 1319

Table 2 Typical wastewater flow rates from commercial sources (DSD; stable sources of shower/laundry discharge exist. The WSD annual report, 2001) shower/laundry wastewater possesses the potential, from Source Unit Flowrate both qualitative and quantitative aspects, for reclama- (l/unit, day) tion and reuse as secondary usage at least. Such rec- Range Typi- lamation and reuse of shower/laundry discharge is cal important to save/augment water supply, and of signifi- Airport Passenger 7.5–15 11.3 cance to improve urban environment. Wastewater reclamation and reuse is one element of Automobile Vehicle served 26.5–49 38 water resource development and management, which service station Employee 34–56 45 provides an innovative and alternative option for agri- Customer 4–19 11 culture, municipality, and industries. The water pollu- Bar Employee 38–60 49 tion control efforts in many countries have made treated Toilet room 1040–1520 1280 effluent from municipal wastewater available that may (laundry) be an economical augmentation to the existing water Department Employee 30–45 38 supply when compared to the increasingly expensive and store Customer 34–56 40 environmentally destructive new water resources development. In the planning and implementation of wastewater Hotel Guest (shower) 151–212 181 reclamation and reuse, the intended wastewater reuse ap- Employee 26–49 38 plications govern the degree of wastewater treatment Laundry/ 1700–2460 2080 machine required and the reliability of wastewater treatment processing and operation. It is necessary to investigate Office Employee 26–60 49 the potentials of reuse of municipal wastewater and the Restaurant Meal 7.5–15 11.3 corresponding constraints. In principle, wastewater or any marginal quality waters can be used for any purpose Shopping center Employee 26.5–49 38 provided that they meet the water quality requirements Parking space 3.8–7.6 7.6 for the intended use. Table 4 lists the identification of seven categories of reusing municipal wastewater along Total 3917 with the potential constraints (Olsson and Newell, 1999). Fig. 2 shows the types and volume of wastewater Tables 1–3 also imply that, in Hong Kong, not only the reuse in California and Japan in 1996 (Al-Sulaim and municipal wastewater dominates, also the abundant, Asano, 2000). It can be seen that, among these seven 1454 W. Lu et al. / Chemosphere 52 (2003) 1451–1459

Table 4 Categories of municipal wastewater reuse and potential constraints Wastewater reuse categories Potential constraints Agricultural irrigation Crop irrigation Eﬀect of water quality, particularly, salts on soils and crops; Public health Commercial nurseries concerns related to pathogens (bacteria, viruses and parasites) Landscape irrigation Park, school yard Surface and groundwater pollution if not properly managed; Marketability of Freeway median crops and public acceptance; Reclaimed wastewater constituents related to scaling, Golf course corrosion, biological growth, and fouling Cemetery Greenbelt Residential Industrial reuse Cooling Public health concerns, particularly aerosol transmission of organics and Boiler feed pathogens in cooling water and pathogens in various process water Process water Heavy construction

Groundwater recharge Groundwater replenishment Trace organics in reclaimed wastewater and their toxicological effects Salt water intrusion Subsidence control Recreational and environmental uses Lakes and ponds Health concerns of bacteria and viruses; Eutrophication due to nutrients; Esthetics Marsh enhancement including odor Streamflow augmentation Fisheries Snowmaking Non-potable urban uses Fire protection Public health concerns about pathogen transmission by aerosols; Effect of water Air conditioning quality on scaling, corrosion, biological growth and fouling; Potential cross- Toilet flushing connections with potable water systems Potable reuse (repurified water) Blending in water supply Trace organics in reclaimed wastewater and their long-term toxicological effects; Pipe to pipe water supply Esthetics and public acceptance; Public health concerns on pathogen and viruses transmission

categories, the target of potable reuse demands the high- usage, potable use. Such target proposes a challenging est standard of water quality of wastewater reclamation task and an exciting research area. Many sound studies and is not yet completely achieved to date. Although the need to be carried on further. situations are different from case to case, the usage of reclaimed water presents potentials, to certain degree, in various purposes. Agricultural irrigation is the most 3. Proposed scheme of wastewater reclamation commonly target for reusing wastewater. From Table 4 and Fig. 2, it can be foreseen that the reclamation and As mentioned above, the most potential applications reuse of wastewater proposes significant challenges in of wastewater reclamation in Hong Kong include land- addressing the environmental problems relating to the scape irrigation (limited), non-potable urban use, and, management of water, especially to water scarcity area the most challenging target, potable reuse. Such waste- like Hong Kong. water reclamation and reuse planning require the sup- Considering situations in Hong Kong, i.e., no in- port of whole society including public recognition, dustrial and agricultural demands of wastewater, and financial aid, and, sometimes, legislation through gov- no need of groundwater recharge, etc., the potential ernment. Municipal wastewater contains many chemi- wastewater reuses may include landscape irrigation cals, which present known or potential health risks if (limited), non-potable urban use, and, the most potential ingested (Haller, 1995). Hence, wastewater reclamation W. Lu et al. / Chemosphere 52 (2003) 1451–1459 1455

Fig. 2. Types and volumes of wastewater reuse in Japan and California (Al-Sulaim and Asano, 2000). and reuse involve considerations of public health and quirements, and public policy wherein the desire to also require close examinations of infrastructure and conserve rather than develop available water resources facilities of planning, wastewater treatment plant site, may override economic and public health consider- treatment reliability, economic and financial analyses, ations. Through integrated water resources planning, and water utility management involving effective inte- the use of reclaimed wastewater may provide sufficient gration of water and reclaimed wastewater. Whether flexibility to allow a water supply agency to respond to wastewater reuse is appropriate or not depends upon short-term needs as well as increase long-term water careful economic considerations, potential uses for the supply reliability without constructing additional stor- reclaimed water, stringency of waste discharge re- age or conveyance facilities at substantial economic and 1456 W. Lu et al. / Chemosphere 52 (2003) 1451–1459 environmental expenditures. Thus, wastewater reuse about whether and how to implement a water reuse has a rightful place and an important role in optimal project. Monetary analysis falls into two aspects: eco- planning and more efficient management and use of nomic analysis and financial analysis. Economic ana- water resources for society (White, 1987; Rowe and lysis focuses on the value of the resources invested in a Abdel-Magid, 1995; Burton and Stensel, 2002). Plan- project to construct and operate it, measured in mon- ning for wastewater reuse can be divided into three etary terms and computed in the present value. The stages: basic result of the economic analysis is to answer the question: Should a water reuse project be constructed? • conceptual planning, The financial analysis addresses whether a water reuse • feasibility investigation, project is financially feasible. The project sponsor will • facilities planning. need a source of capital and sources of revenue to pay for debt service and operation costs for both the pro- 3.1. Conceptual planning posed wastewater reuse project and any existing facilities. Thus, the equally important question to answer in During conceptual planning stage, a potential project the financial analysis is: Can a water reuse project be is sketched out, rough costs are estimated, and a po- constructed? tential reclaimed water market is identified. Some initial A common misconception in planning for wastewater surveys and site investigations are required to obtain the reuse is that reclaimed wastewater represents a low-cost records of wastewater amount from main residential new water supply. This assumption is generally true only sites, crowded commercial building groups (e.g., Cen- when wastewater reclamation facilities are conveniently tral, Causeway Bay, Mong Kwok), public altitudes to located near large users and when no additional treat- the idea of wastewater reclamation, etc. If the concept ment is required beyond the water pollution control appears worthwhile, feasibility investigation takes place facilities from which reclaimed water is delivered. The next. conveyance and distribution systems for reclaimed water represent the principal cost of most proposed water reuse projects. Recent experience in California indicates 3.2. Feasibility investigation that approximately four million dollars in capital cost are required for each one million m3 per year of re- The feasibility investigation includes: (a) performing claimed water made available for reuse. Assuming a a market assessment for reclaimed wastewater; (b) as- facility life of 20 years and a 9% interest rate, the am- sessing the existing water supply facilities and devel- ortized cost of this reclaimed water is US$0.5/m3, ex- oping some preliminary alternatives; (c) developing or cluding operation and management costs (Al-Sulaim identifying the alternative non-reclamation facilities, and Asano, 2000). The main steps in wastewater recla- such as wastewater treatment for stream discharge mation and reuse plan include: (a) study area charac- or constructing dams and reservoirs for future water teristics, (b) water supply characteristics and facilities, supply, with which to compare a proposed water re- (c) wastewater characteristics and facilities, (d) treat- use option; and (d) performing a preliminary screening ment requirements for discharge, reuse and other re- of wastewater reuse alternatives to consider technical, strictions, (e) potential water reuse customers, (f) project economic and financial attractiveness, and other con- alternative analysis, (g) recommended plan, (h) constraints such as public health protection. If wastewater structing financing plan and revenue program. Fig. 3 reclamation and reuse appear viable, then detailed shows the outlines of wastewater reclamation and reuse actual planning can be pursued, refined facilities al- plan. The wastewater reclamation project is a compli- ternatives developed, and a final facilities plan pro- cated one that involves many parties from the society to posed. contribute together. Considering Hong KongÕs situations, assessments on 3.3. Facilities planning current or potential water resources has been carried out and results are listed in Table 5. Table 5 presents the A key task in planning a wastewater reclamation results of a preliminary study on current available and project is to find potential customers who want and potential water resources. The results indicate that the know how to use reclaimed wastewater for their ap- water from Dongjiang River is still a major fresh water plications. Whether a user is capable of using reclaimed resource to Hong Kong in next decade; the municipal wastewater depends on the quality of effluent available wastewater may become another water source due to its and its suitability for the type of use involved. Al- abundant supply and relatively low cost; the purification though technical, environmental, and social factors are of sea water and increase of rainfall catchment areas considered in project planning, monetary factors usu- would claim higher costs, good quality land resources, ally override other issues when decisions are made etc., and may not be suitable to be considered as alter- W. Lu et al. / Chemosphere 52 (2003) 1451–1459 1457

Fig. 3. Outline of wastewater reclamation and reuse plan. natives of water supply augment in Hong Kong. The 4. Proposed processes of shower/laundrywastewater HKSAR government intends to proceed the scheme of reclamation municipal wastewater reclamation. The paper presented here aims to invoke the awareness and attention of In Hong Kong, wastewater mainly comes from do- whole society to protect and save our water resources, to mestic, commercial, and rainfall sewer, etc. These waste- promote challenging research topics, and to suggest water resources need to be collected to a combined sewer possible way to achieve the targets. ﬁrst, and then pumped into wastewater treatment plant 1458 W. Lu et al. / Chemosphere 52 (2003) 1451–1459

Table 5 Assessment of current/potential water resources Sources Unit price (HK$/m3) Advantage Disadvantage Dongjiang River, Canton province, PRC 4.5 currently Stable Worry of water quality upstream Cheapest at moment Reclamation of municipal wastewater 5.3 approximately Abundant resources Long-time to be accepted by public Puriﬁcation (Reclamation) of sea water 7.7 approximately Unlimited sea water resource High cost Occupy high quality land resource on coast Increase of rainfall catchment areas 9.1 approximately NA Unstable resource Occupy quality land resource Highest cost for further treatment before discharge. Similar to cate- gory of solid wastes, we propose to categorize the wastewater from domestic/commercial buildings ﬁrst, i.e., Shower/laundry Rainfall wastewater Shower/laundry stream separate shower/laundry water from other wastewater, collection from wastewater commercial sites collect shower/laundry water to combined sewer, and then collection from pump into treatment plant. The proposed scheme can be domestic sites started from the design stage of a newly developed residential/town site. Figs. 4 and 5 present the schematic processes of shower/laundry wastewater reclamation. It can be seen that the quality control is a key step to guar- antee the quality of reclaimed water in the wastewater reclamation system. It should be mentioned that quality Combined sewer control also includes the monitoring of bio-organics (Basin for secondary water) growth and migration, which proposes a challenging task to such wastewater treatment system (Leggett, 2001). Fig. 4. Wastewater collection system.

Fig. 5. Treatment processes of wastewater. W. Lu et al. / Chemosphere 52 (2003) 1451–1459 1459

5. Conclusions Bryan, E.H., 2000. Research needs for developing innovative water and wastewater treatment technologies. Water Sci- This paper proposes a challenging topic of develop- ence and Technology 42 (12), 61–64 (special issue). ment of shower/laundry wastewater reclamation and Burton, F.L., Stensel, H.D., 2002. Wastewater Engineering: reuse to the society. The topic concerns the public Treatment and Reuse. McGraw-Hill Ltd., USA. Cheremisinoff, N., Cheremisinoff, P., 1993. Water Treatment awareness of limited natural water resource, the reser- and Wastewater Recovery. PTR Prentice Hall, Inc., A vation of natural water resources, the potential solution Simon & Schuster Company, Englewood Cliffs, NJ, USA. to augment water resource, and the promotion of better Drainage Services Department, HKSAR: 2001, Annual report. urban environment. It involves many factors relating to Haller, E.J., 1995. Simplified Waster Water Treatment Plant different parties in the society. The feasibility and prac- Operations. Technomic Publishing Co. Inc., USA. ticability of the scheme mainly depend on the public Harrison, R.M., 1999. Understanding Our Environment––An altitude and the support of whole society, which is al- Introduction to Environmental Chemistry and Pollution. most in the half way if such support acquired. Further The Royal Society of Chemistry, Redwood Books Ltd., studies are required to deeply understand the water re- UK. source and usage target in Hong Kong. Henze, M., Harremo€ees, P., Cour Jansen, J.L., Arvin, E., 2002. Wastewater Treatment––Biological and Chemical Pro- cesses. Springer-Verlag, Berlin, Heidelberg, Germany. Acknowledgements Leggett, D.J., 2001. Rainwater and Greywater use in Buildings: Best Practice Guidance. CIRIA Publishing, UK. National Research Council (NRC), 1998. In: Dobbs, D.A. The work described in this paper was supported by (Ed.), Issues in Potable Reuse. National Academy Press, Strategic Research Grants # 7001371 (BC) and 7001463 Washington DC, USA. (BC) from, City University of Hong Kong, HKSAR. Olsson, G., Newell, B., 1999. Wastewater Treatment Systems–– Modelling, Diagnosis and Control. IWA Publishing, UK. Rowe, D.R., Abdel-Magid, I.M., 1995. Handbook of Waste- References water Reclamation and Reuse. Lewis Publishers, USA. Spivy, W., 2002. There is no new water, US Water News, 3–5. Al-Sulaim, J., Asano, T., 2000. Wastewater Reclamation and Water Services Department, HKSAR: 2001, Hong KongÕs Reuse. New Age International (P) Ltd. water, Annual report. Asano, T., 2002. Water from (waste) water––the dependable White, J.B., 1987. Wastewater Engineering. Edward Arnold water resource. Water Science and Technology 43 (1), 24–33. Publisher, UK.