Resource Recovery from Faecal Sludge Using Constructed Wetlands
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Resource Recovery from Faecal Sludge using Constructed Wetlands A survey of the literature UWEP Working Document Herbert Aalbers February 1999 Nieuwehaven 201 tel : +31 182 522625 2801 CW Gouda fax : +31 182 550313 the Netherlands e-mail: [email protected] Copyrights The research for this publication received financing from the Netherlands Development Assistance (NEDA), Ministry of Foreign Affairs. Citation is encouraged. Short excerpts may be translated and/or reproduced without prior permission, on the condition that the source is indicated. For translation and/or reproduction in whole, WASTE should be notified in advance. Responsibility for the contents and for the opinions expressed rests solely with WASTE. This publication does not constitute an endorsement by the financier. WD10.doc 2 Resource recovery from faecal sludge using constructed wetlands WASTE, February 1999 PREFACE In the sanitation sector there is growing attention for issues of sustainability. This interest is expressed in, for example, an increasing number of initiatives that are focused on the closing of water and nutrient cycles and the recovery and reuse of these resources. There is not much experience with resource recovery from non-sewered on-site sanitation facilities in developing countries. In this respect is has been very challenging to give a state-of-the-knowledge of resource recovery from faecal sludge using wetlands. It was not always easy to retrieve the literature, so I am grateful to the persons who contributed to this report by sending information, reviewing the draft document and giving general support. I would like to mention several people, because without their contribution this report would not have been as it is. First, I want to mention Martin Strauss and Udo Heinss (SANDEC, Switzerland), who have a broad experience in faecal sludge treatment. They took time to read the draft and made valuable comments on the contents and structure of the document. They were an essential source of information. Also, I would like to thank Annelies Balkema (Eindhoven University of Technology, the Netherlands), Gregory Rose (IDRC, Canada) and Dhrubajyoti Ghosh (CMW SA, India) for sending information, reference lists and comments. Finally, I would like to thank all the people of WASTE for their support and co-operation. Herbert Aalbers February 1999 Resource recovery from faecal sludge using constructed wetlands 3 WASTE, February 1999 TABLE OF CONTENTS ABBREVIATIONS..................................................................................................................................................6 GLOSSARY.............................................................................................................................................................7 SUMMARY.............................................................................................................................................................9 CHAPTER 1 INTRODUCTION............................................................................................................................11 1.1 Public health ..............................................................................................................................11 1.2 Resource recovery with wetlands...............................................................................................11 1.3 Objectives and scope this report................................................................................................12 CHAPTER 2 NEIGHBOURHOOD SCALE ........................................................................................................15 2.1 Advantages ................................................................................................................................15 2.2 Disadvantages............................................................................................................................16 CHAPTER 3 FAECAL SLUDGE.........................................................................................................................17 3.1 Human excreta...........................................................................................................................17 3.2 Faecal sludge .............................................................................................................................18 3.3 Nightsoil ....................................................................................................................................18 3.4 Sewage sludge............................................................................................................................19 3.5 Comparison................................................................................................................................20 CHAPTER 4 SLUDGE TREATMENT................................................................................................................21 4.1 Solids/liquid separation .............................................................................................................21 4.1.1 Gravity solids/liquid separation.........................................................................................21 4.1.2 Mechanical solids/liquid separation ..................................................................................22 4.2 Digestion....................................................................................................................................23 4.3 Incineration and combustion......................................................................................................23 4.4 Composting................................................................................................................................24 4.4.1 Composting processes.......................................................................................................24 4.4.2 (Co-)composting of faecal sludge .....................................................................................27 4.5 Disposal and discharge ..............................................................................................................29 4.6 Lagooning..................................................................................................................................29 CHAPTER 5 WETLANDS FOR SLUDGE TREATMENT.................................................................................31 5.1 Natural wetlands ........................................................................................................................31 5.2 Constructed wetlands.................................................................................................................31 5.2.1 Emergent macrophyte systems ..........................................................................................32 5.2.2 Free floating macrophytes and fish ponds.........................................................................37 5.2.3 Submerged macrophyte based systems .............................................................................41 4 Resource recovery from faecal sludge using constructed wetlands WASTE, February 1999 CHAPTER 6 RECOVERY OF THE RESOURCES FROM WETLANDS..........................................................43 6.1 Direct reuse of Faecal Sludge ....................................................................................................43 6.1.1 Agriculture ........................................................................................................................43 6.1.2 Aquaculture.......................................................................................................................45 6.2 Reuse of Faecal Sludge treatment products ...............................................................................45 6.2.1 Use of the effluent of ponds and wetlands.........................................................................45 6.2.2 Use of the biomass of wetlands and ponds........................................................................46 6.3 Integration of treatment and reuse systems ................................................................................51 6.3.1 Mali...................................................................................................................................51 6.3.2 Vietnam.............................................................................................................................52 6.3.3 India ..................................................................................................................................52 6.3.4 Mexico ..............................................................................................................................53 6.3.5 Bangladesh........................................................................................................................55 6.3.6 China.................................................................................................................................55 CHAPTER 7 CONCLUSIONS AND RECOMMENDATIONS ..........................................................................57 REFERENCES.......................................................................................................................................................59 ANNEX 1...............................................................................................................................................................65 ANNEX 2...............................................................................................................................................................66