Msc Thesis MWI SE 2014-24

MANAGEMENT AND OPERATION OF ONSITE WASTEWATER TREATMENT SYSTEMS - AN ANALYSIS OF SUCCESS FACTORS Herath Mudiyanselage Udayakantha Herath MSc Thesis MWI SE 2014-24 April 2014 MANAGEMENT AND OPERATION OF ONSITE WASTEWATER TREATMENT SYSTEMS - AN ANALYSIS OF SUCCESS FACTORS Master of Science Thesis by Herath Mudiyanselage Udayakantha Herath Supervisors Prof. Damir Brdjanovic Mentors Dr. M.Ronteltap Dr. M. Mulenga Dr. Christoph Luethi Mr. M.G. Sherpa Examination committee Prof. D. Brdjanovic Dr. M. Ronteltap Dr. C. Luethi This research is done for the partial fulfilment of requirements for the Master of Science degree at the UNESCO-IHE Institute for Water Education, Delft, the Netherlands Delft April 2014 ©2014by Herath Mudiyanselage Udayakantha Herath. All rights reserved. No part of this publication or the information contained herein may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, by photocopying, recording or otherwise, without the prior permission of the author. Although the author and UNESCO-IHE Institute for Water Education have made every effort to ensure that the information in this thesis was correct at press time, the author and UNESCO- IHE do not assume and hereby disclaim any liability to any party for any loss, damage, or disruption caused by errors or omissions, whether such errors or omissions result from negligence, accident, or any other cause. Abstract The main objectives of this research are to identify the main challenges and success factors of operation and management of the DEWATS system at Nala in Nepal; including analyse the performance of the system; and to make recommendations on how the system can be improved and how lesions can be applied to similar type of systems in peri-urban areas of Nepal. In order to achieve the objectives; sampling and laboratory analysis of wastewater samples collected at various points were performed. Additionally, a household survey covering 20% of the total households in the area, semi structured interviews with key groups related to operation and management of the treatment system and data collection from grey literature were carried out. Sampling was carried out in the coldest months of the year, after 6-9 months from the start of the operation in the treatment plant. According to the results, although the treatment system achieves considerable removal efficiencies (more than 80% for COD and more than 93% for TSS), effluent quality was below the required effluent standards, in case of organic matter and pathogen removal. Therefore, further treatment steps would be necessary, if treated effluent is discharged to the surface water. However, reuse of treated wastewater for irrigation is a viable option. High level of treatment may therefore not be needed and most of the farmers are already willing to use the treated wastewater in their fields. However, Ammonia concentration was high even in the effluent and therefore, precautions have to be taken to avoid ammonia toxicity for the crops. Selecting minimum wastewater temperature has a large effect on design of anaerobic baffled reactors and constructed wetlands and that was a major factor to overestimate the quality of effluent in the design. Therefore, selecting a realistic minimum wastewater temperature is very important in design, when further applying this type of treatment systems. A well established community organization with high public participation, vibrant leadership and team spirit engaged in operation and management of the treatment system is vital. Successful community involvement activities including the success of Community Led Urban Environmental Sanitation (CLUES) approach were major success factors for institutional sustainability. Treatment system is financially sustainable, if it is possible to operate with limited staff and getting voluntary community participation for most of the activities. Key words: DEWATS, Operation and management, Nepal, Anaerobic baffled reactor, Constructed wetlands i MANAGEMENT AND OPERATION OF ONSITE WASTEWATER TREATMENT SYSTEMS - AN ANALYSIS OF SUCCESS FACTORS Acknowledgements First of all, I would like to thank Eawag-Sandec for giving me an opportunity to do this research. Special thanks to my mentors Dr. Mariska Ronteltap and Dr. M. Mulenga from UNESCO- IHE, Dr. Christoph Luethi from Eawag and Mr. Mingma Sherpa from Nepal and my supervisor, Prof. Damir Brdjanovic, for their guidance and motivating me to make this research a success. Thanks for all who helped in the field work at Nepal. Special thanks to Mr. Mingma Sherpa, who helped me lot from the first day, after I came to Nepal, Mr. Bipin Dangol, my research assistants; Mr. Buddha Bajracharya and Mr. Roshan Chaulagain. Also, ENPHO gave me all the facilities to work at their office and did all the hard work of testing samples in a limited time frame. Lot of gratitude for the people in Nala, office bearers and staff of Nala Drinking Water and Sanitation Committee and CIUD project office and the operator of the treatment plant for their great support at the field work of my research. It was a nice experience for me to work with a group of very friendly people in a nice country. I very much appreciate support of every one, who helped me for my research although I could not mention all the names here. iii Table of Contents Abstract i Acknowledgements iii List of Figures vii List of Tables viii Abbreviations x 1. Introduction 1 1.1. Problem statement, Research objectives, Research questions and Hypothesis 1 1.1.1. Problem statement 1 1.1.2. Research objectives 3 1.1.3. Research questions 3 1.1.4. Hypothesis 3 1.2. Wastewater treatment in Nepal 3 1.2.1. Wastewater related legislation in Nepal 4 1.2.2. Centralized wastewater treatment in Nepal 5 1.2.3. Decentralized wastewater treatment in Nepal 5 1.3. The concept of Decentralized wastewater treatment systems (DEWATS) 6 1.4. Treatment modules used in DEWATS systems 7 1.4.1. Settler/ Septic tank 7 1.4.2. Biogas reactor 8 1.4.3. Anaerobic baffled reactor 8 1.4.4. Anaerobic filter 9 1.4.5. Horizontal subsurface flow constructed wetland 10 1.4.6. Vertical subsurface flow constructed wetland 11 1.4.7. Waste stabilization ponds 12 2. Materials and Methods 13 This chapter contains a description about DEWATS system at Nala, which was selected for this study and various methods used for collection of data required to achieve the objectives. 13 2.1. Decentralized wastewater treatment system at Nala 13 2.1.1. Location 13 2.1.2. Situation before implementation of the treatment system 13 2.1.3. Design of the treatment system at Nala 14 2.1.4. Treatment components 15 2.1.5. Sewer system 17 2.1.6. Implementation of the project of wastewater treatment 17 2.1.7. Community Led Urban Environmental Sanitation (CLUES) approach 18 2.1.8. Current situation of the system 18 2.2. Sampling and laboratory analysis 18 2.2.1. Sampling 18 2.2.2. In-situ measurements 21 2.2.3. Laboratory analysis 22 iv 2.2.4. Climatic conditions at the sampling period 22 2.3. Semiformal interviews 22 2.3.1. Household survey 23 2.3.2. Semiformal interviews with operation and management staff 23 2.3.3. Semiformal interviews with office bearers of the community organization 23 2.4. Literature review 23 2.5. Data collection from grey literature 23 2.6. Evaluation of the existing design 23 2.7. Analysis of the results 24 3. Results 27 This chapter contains results of the study. It includes performance results of the treatment system obtained from sampling, in-situ measurements and laboratory analysis and also the results obtained from other methods like semi structured interviews and data collected from grey literature. However, the sampling was carried out 6-9 months after the commencement of the operation at the treatment system. Also, sampling was performed at the coldest months of the year. Therefore, microbial activity in ABR and constructed wetlands might not be well established and cold temperature might also reduce it. 27 3.1. Technical performance of the treatment system 27 3.1.1. Flow rate 27 3.1.2. pH 29 3.1.3. Wastewater temperature 30 3.1.4. Solids removal 31 3.1.5. Organic matter removal 32 3.1.6. Nutrient removal 35 3.1.7. Pathogen removal 39 3.1.8. Summary of the discharge water quality 41 3.1.9. Climatic conditions of the sampling period 42 3.2. Results for analysis of Institutional and social aspects 42 3.2.1. Household information 43 3.2.2. Current situation of sanitation in households 44 3.2.3. Public involvement and acceptance of the current treatment system 45 3.2.4. Sludge treatment system 47 3.2.5. Treated wastewater reuse potential 47 3.2.6. Sewer system 48 3.2.7. Results from semiformal interviews with operation and management staff and office bearers of the community organization 48 3.3. Results for financial analysis 49 3.3.1. Income for the community organization 49 3.3.2. Capital expenditure 49 3.3.3. Recurrent expenditure 50 4. Discussion 51 4.1. Comparison of performance results with similar studies 51 4.1.1. Settler 51 4.1.2. Anaerobic baffled reactor 52 4.1.3. Horizontal subsurface flow constructed wetlands 53 4.1.4. Treatment system as a whole 54 4.2. Comparison of results with the original design 55 4.3. Redesign of treatment system with measured data 56 4.3.1. Redesign of settlers 56 4.3.2. Redesign of Anaerobic baffled reactors 59 v 4.3.3. Redesign of Horizontal subsurface flow constructed wetlands 61 4.3.4. Redesign of Constructed wetlands with anaerobic filters 63 4.4. Comparison of measured effluent quality with theoretical values 66 4.4.1.

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