Field Assessment of Wastewater Treatment Facilities
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FIELD ASSESSMENT OF WASTEWATER TREATMENT FACILITIES IN THE OAXACA VALLEY, MEXICO HUMBOLDT STATE UNIVERSITY By Peter H. Haase A Master’s Project In Partial Fulfillment Of the Requirements for the Degree Master of Science Environmental Systems International Development and Technology May 2010 FIELD ASSESSMENT OF WASTEWATER TREATMENT FACILITIES IN THE OAXACA VALLEY, MEXICO HUMBOLDT STATE UNIVERSITY By Peter H. Haase Approved by the Master’s Project Committee Robert Gearheart, Major Professor Date Brad Finney, Committee Member Date Arne Jacobson, Committee Member Date Chris Dugaw, Graduate Coordinator Date Jená Burges, Vice Provost Date ABSTRACT FIELD ASSESSMENT OF WASTEWATER TREATMENT FACILITIES IN THE OAXACA VALLEY, MEXICO By Peter H. Haase Latin America and the Caribbean is the most urbanized region in the developing world. However, less than 10 percent of domestic and industrial wastewater is properly treated, causing severe environmental, health, social and economic problems. Over the past several years, Mexico has undertaken significant sanitation projects including wastewater treatment projects. State and federal water agencies have assisted both semi-urban and rural communities construct over 80 municipal wastewater treatment plants in the State of Oaxaca in southern Mexico. From July 2006 through February 2008, an investigation was conducted to evaluate ten (10) wastewater treatment systems in Oaxaca, Mexico. Nine (9) systems utilized vegetated gravel bed treatment systems and the tenth system used wastewater stabilization ponds. The objectives of the investigation were to understand the factors that motivated the communities to install wastewater treatment systems, select the type of systems, costs of the systems, and to review the design and construction of the projects. The evaluation also evaluated the social, political, economic and technical factors affecting the performance, operation and maintenance of the plants. The study found that the majority of the systems were in poor operating condition. The poor operating systems resulted from various factors including engineering designs using dated and inaccurate design criteria, inadequate operation and maintenance, and in some instances substandard construction practices. iii TABLE OF CONTENTS ABSTRACT………………………………………………………………………………iii LIST OF TABLES………………………………………………………………………. vii LIST OF FIGURES…………………………………………………………………….. viii INTRODUCTION…………………………………………………………………………1 Literature Review………………………………………………………………….4 Setting…………………………………………………………………………….. 4 Methods……………………………………………………………………………4 Study Findings……………………………………………………………………. 5 Conclusions and Recommendations……………………………………………… 5 LITERATURE REVIEW………………………………………………………………… 6 Economic Impacts of Wastewater Discharge……………………………………...6 Investment to Water Supply and Sanitation Sector………………………………. 9 Level of Wastewater Treatment…………………………………………………. 13 Constraints to Improved Sanitation and Wastewater Treatment………………... 16 Inadequate and Poorly Maintained Infrastructure……………………….. 16 Inappropriate Technology……………………………………………….. 18 Financial Constraints……………………………………………………. 21 Insufficient Operation and Maintenance………………………………… 22 Conclusions……………………………………………………………………… 23 SETTING………………………………………………………………………………... 25 State of Oaxaca………………………………………………………………….. 25 Oaxaca Valley…………………………………………………………………… 29 Setting…………………………………………………………………… 30 Physiography……………………………………………………………..31 Mountain Zones…………………………………………………. 31 Piedmont………………………………………………………… 31 High Alluvium……………………………………………………32 Low Alluvium…………………………………………………… 32 Climate…………………………………………………………………... 33 Temperature……………………………………………………... 34 Rainfall…………………………………………………………... 34 Evaporation……………………………………………………… 37 Annual Water Deficit……………………………………………. 37 Surface Water Resources………………………………………………... 38 River (Rio) Atoyac………………………………………………. 38 River (Rio) Salado/Tlacolula……………………………………. 39 Groundwater Resources…………………………………………………. 40 Etla Valley Groundwater Basin…………………………………. 40 Tlacolula Valley Groundwater…………………………………... 41 Zimatlan Valley Groundwater…………………………………... 42 iv Water Use………………………………………………………………... 42 Economics……………………………………………………………….. 42 Governance……………………………………………………………… 45 Education…………………………………………………………………47 Health Care……………………………………………………………… 48 Water and Sanitation Infrastructure……………………………………... 49 Water Supply……………………………………………………………. 49 Wastewater Treatment…………………………………………………... 50 Project Costs……………………………………………………...54 METHODS……………………………………………………………………………… 56 Community Selection Process……………………………………………………56 Procedures for Community Visit, Facility Inspection and Data Collection……...57 Technical Evaluation of Wastewater Treatment Plants…………………………. 60 Agency Interviews………………………………………………………………. 61 Communities Visited……………………………………………………………. 61 RESULTS……………………………………………………………………………….. 63 Overview………………………………………………………………………… 63 Community Description…………………………………………………………. 65 Peri-Urban Communities………………………………………………... 65 San Andres Huayapam………………………………………….. 65 San Sabastian de Tutla…………………………………………... 73 Santa Lucia del Carmen…………………………………………. 77 Regional Towns…………………………………………………………. 81 Tlacolula de Matamoros………………………………………… 81 San Francisco Telixlahuaca………………………………………85 Rural Communities……………………………………………………… 89 Santo Domingo de Tomaltepec………………………………….. 89 San Tomas Mazaltepec………………………………………….. 92 Teotilan del Valle………………………………………………... 95 San Dionisio de Ocotepec………………………………………. 99 San Pablo de Mitla……………………………………………... 103 Summary of Findings…………………………………………………………... 107 General Findings……………………………………………………….. 107 Community Field Assessment Summary………………………………. 109 Community Factors…………………………………………….. 109 Governance……………………………………………...109 Education………………………………………………..110 Economic Status………………………………………...110 Employment and Income………………………………. 110 Technical Factors………………………………………………. 113 Engineering Design and Plant Sizing………………….. 113 Construction…………………………………………… 113 Operation and Maintenance……………………………. 114 Operation Status………………………………………... 114 Disposal and Reuse 114 v Ambient Water Quality………………………………… 116 Managerial and Financial Factors……………………………… 118 CONCLUSIONS AND RECOMMENDATIONS…………………………….. 122 Conclusions…………………………………………………………….. 122 Recommendations……………………………………………………… 125 REFERENCES………………………………………………………………… 127 APPENDIX A – TECHNICAL EVALUATION OF WASTEWATER TREATMENT SYSTEMS……………………………………………………...130 vi LIST OF TABLES Table Page 1 Investment by IDB and WB in Water Supply and Sanitation Project…....... 11 2 Sanitary Sewers and Wastewater Treatment Coverage in Latin America and Cuba………………………………………………………….. 15 3 Type of Wastewater Treatment in Latin America and Cuba………………. 17 4 Summary of Various Constraints or Factors Leading to Water and Sanitation Project Failures…………………………………………………. 24 5 The Background Statistics on the Demographics for the Country of Mexico and the State of Oaxaca……………..…………………………….. 29 6 Summary of Historic Climatic Data for Oaxaca Valley Region………….... 36 7 Water and Sanitation Coverage in Oaxaca and Other States of Mexico…... 49 8 Type and Number of Community Wastewater Treatment Plants…….......... 51 9 Capital Costs for Five Three-Stage Anaerobic Treatment Systems……….. 55 10 Location and Population Information for Each Community………………. 62 11 Water Quality Data for Wastewater Treatment for Tlacolula……………... 84 12 Community Factors Assessment…………………………………………… 112 13 Summary of Evaluation of Plant Sizing and Design Criteria……………… 115 14 Technical Factors Assessment……………………………………………... 117 15 Managerial and Financial Factors………………………………………….. 120 vii LIST OF FIGURES Figure Page 1 Relief Map of Oaxaca and Region…………………………………………. 26 2 Municipal Boundaries in the State of Oaxaca……………………………… 27 3 Map of Oaxaca Valley and Major Rivers………………………………….. 30 4 Map of the Valley of Oaxaca to Show Main Physiographic Zones………... 33 5 Map of Oaxaca Valley and Predominant Soil Types………………………. 34 6 Mean Monthly Temperature in Oaxaca City………………………………. 35 7 Mean Monthly Precipitation in the City of Oaxaca………………………... 36 8 Mean Monthly Evaporation in the City of Oaxaca………………………… 37 9 Pattern of Annual Water Deficit for the City of Oaxaca…………………... 37 10 Photo of Rio Atoyac in the City of Oaxaca………………………………... 39 11 Photo of Rio Salado, Oaxaca, Mexico……………………………………...40 12 Typical Layout of First Generation Wastewater Treatment System with Anaerobic Digester and Vegetated Gravel Bed………………………. 53 13 Typical Layout of a Three-Stage Anaerobic Treatment Plant at Santo Domingo Tomaltepec……………………………………………….. 54 14 Map of Community Site Visits…………………………………………….. 62 15 Satellite Image of San Andreas Huayapam………………………………... 66 16 Aerial Photo of Wastewater Treatment Plant ………….………………….. 68 17 Treatment Plant Headworks (bar screen and grit chamber) and Anaerobic Digester…………………………………………………………68 18 Upflow Anaerobic Rock Filter……………………………………………..69 19 Vegetated Gravel Beds……………………………………………………..69 viii 20 Effluent from Upflow Anaerobic Rock Filter and Vegetated Gravel Bed…69 21 Outlet Control Box with Adjustable Pipe outlet…………………………… 70 22 Covered PVC Piping Detail at Treatment Plant…………………………… 71 23 Satellite Image of San Sebastian de Tutla………………………………….. 74 24 Aerial Photo of Wastewater Treatment Plant for San Sebastian De Tutla……………………………………………………………………. 75 25 Photos of Vegetated Gravel Bed and Surfacing Effluent………………….. 75 26 Final Effluent Quality San Sebastian de Tutla……………………………... 76 27 Satellite Image of Santa Lucia del Camino………………………………… 78 28 Inlet and Outlet Weir Configuration for Up Flow Anaerobic Rock Filter………………………………………………………………….