Planted Drying Beds

A planted drying bed is similar to an Unplanted Drying Bed, but has the added benefit of transpiration and enhanced sludge treatment due to the plants. The key improvement of the planted bed over the unplanted bed is that the filters do not need to be desludged after each feeding/drying cycle. Fresh sludge can be directly applied onto the previous layer; the plants and their root systems maintain the porosity of the filter.  

This technology has the benefit of dewatering and stabilizing the sludge. Also, the roots of the plants create pathways through the thickening sludge that allow water to easily escape.

The appearance of the bed is similar to a Vertical Flow Constructed Wetland. The beds are filled with sand and gravel to support the vegetation. Instead of effluent, sludge is applied to the surface and the filtrate flows down through the subsurface where it is collected in drains.

Design Considerations

Ventilation pipes connected to the drainage system contribute to aerobic conditions in the filter. A general design for layering the bed is: (1) 250 mm of coarse gravel (grain diameter of 20 mm); (2) 250 mm of fine gravel (grain diameter of 5 mm); and (3) 100 to 150 mm of sand . Free space (1 m) should be left above the top of the sand layer to account for about 3 to 5 years of accumulation.

Reeds (Phragmites sp.), cattails (Typha sp.) antelope grass (Echinochloa sp.) and papyrus (Cyperus papyrus)are suitable plants, depending on the climate. Local, non-invasive species can be used if they grow in humid environments, are resistant to salty water and readily reproduce after cutting.

Sludge should be applied in layers between 75 to 100 mm thick and reapplied every 3 to 7 days, depending on the sludge characteristics, the environment and operating constraints. Sludge application rates of 100 to 250 kg/m2/year have been reported in warm tropical climates. In colder climates, such as northern Europe, rates up to 80 kg/m2/year are typical. Two or more parallel beds can be alternately used to allow for sufficient degradation and pathogen reduction of the top layer of sludge before it is removed.

The leachate that is collected in the drainage pipes must be treated properly, depending on where it is discharged.


Appropriateness

This technology is effective at decreasing the sludge volume (down to 50%) through decomposition and drying, which is especially important when the sludge needs to be transported elsewhere for end-use or disposal.Because of their area requirements, planted drying beds are most appropriate for small to medium communities with populations up to 100,000 people, but they can also be used in bigger cities. If designed to service urban areas, planted drying beds should be at the border of the community, but within economic reach for motorized emptying operators.

Health Aspects/Acceptance

Because of the pleasing aesthetics, there should be few problems with acceptance, especially if located sufficiently away from dense housing. Undisturbed plantations can attract wildlife, including poisonous snakes.

Faecal sludge is hazardous and anyone working with it should wear protective clothing, boots and gloves. The degree of pathogen reduction of the sludge will vary with the climate. Depending on the desired end-use, further storage and drying might be required.

Operation & Maintenance

Trained staff for operation and maintenance is required to ensure proper functioning. The drains must be maintained and the effluent properly collected and disposed of. The plants should have grown sufficiently before applying the sludge. The acclimation phase is crucial and requires much care. The plants should be periodically thinned and/or harvested. After 3 to 5 years the sludge can be removed.

References

Further Readings

  • Cover image of a reference book or miscellany.

    ANDREOLI, C.V. (Editor); SPERLING, M. von (Editor); FERNANDES, F. (Editor) (2007): Sludge Treatment and Disposal. London: International Water Association (IWA) Publishing. URL [Accessed: 01.11.2013]. PDF

    Sludge Treatment and Disposal is the sixth volume in the series Biological Wastewater Treatment. The book covers in a clear and informative way the sludge characteristics, production, treatment (thickening, dewatering, stabilisation, pathogens removal) and disposal (land application for agricultural purposes, sanitary landfills, landfarming and other methods). Environmental and public health issues are also fully described.

  • Cover image of a reference book or miscellany.

    VERHAGEN, J.; CARRASCO, M. (2013): Full-Chain Sanitation Services That Last. Non-Sewered Sanitation Services. The Hague: International Water and Sanitation Center (IRC). URL [Accessed: 07.08.2013]. PDF

    This paper sets out a framework for the delivery of non-sewered sanitation services that last, are accessible to all and are at scale. The framework is based on IRC International Water and Sanitation’s (IRC) experience and lessons learnt from its engagement in non-sewered sanitation service at scale.

  • Cover image of a reference book or miscellany.

    HEINSS, U.; KOOTAATEP, T. (1998): Use of Reed Beds for Faecal Sludge Dewatering. A Synopsis of Reviewed Literature and Interim Results of Pilot Investigations with Septage Treatment in Bangkok, Thailand. Duebendorf and Bangkok: Swiss Federal Institute of Aquatic Science (Eawag), Department of Water and Sanitation in Developing Countries (Sandec) and Asian Institute of Technology (AIT). PDF

    This study project tested reed beds for their ability to treat septage.

  • Cover image of a reference book or miscellany.

    HEINSS, U.; LARMIE, S.A.; STRAUSS, M. (1998): Solids Separation and Pond Systems for the Treatment of Faecal Sludges in the Tropics . Lessons Learnt and Recommendations for Preliminary Design . Duebendorf: Swiss Federal Institute of Aquatic Science (EAWAG), Department of Water and Sanitation in Developing Countries (SANDEC). URL [Accessed: 12.04.2010]. PDF

    The report sets out to provide guidelines for the preliminary design of faecal sludge treatment schemes comprising solids-liquid separation and stabilisation ponds. The document is based on the results of collaborative field research conducted by the Ghana Water Research Institute and SANDEC on full and pilot-scale faecal sludge (FS) treatment plants located in Accra, Ghana.

  • Cover image of a reference book or miscellany.

    HEINSS, U.; LARMIE, S.A.; STRAUSS, M. (1999): SOS - Management of Sludges from On-Site Sanitation. Characteristics of Faecal Sludges and their Solids-Liquid Separation. Duebendorf and Accra: Swiss Federal Institute of Aquatic Science (EAWAG). PDF

    This document gives an overview on the characteristics of different sludges as well as monitoring results and recommendations for design of solid-liquid separation. It is based on a field report.

  • Cover image of a reference book or miscellany.

    HEINSS, U.; STRAUSS, M. (1999): SOS - Management of Sludges from On-Site Sanitation. Co-treatment of Faecal Sludge and Wastewater in Tropical Climates. Duebendorf and Accra: Swiss Federal Institute of Aquatic Science (EAWAG). URL [Accessed: 21.04.2010]. PDF

    This article provides operational and design guidance for the co-treatment of faecal sludge in waste stabilisation ponds and in activated sludge sewage treatment plants. Problems which may arise when highly concentrated faecal sludge is not properly included in the design of the co-treatment system are also discussed.

  • Cover image of a reference book or miscellany.

    KLINGEL, F. ; MONTANGERO, A. ; KONE, M.; STRAUSS, M. (2002): Fecal Sludge Management in Developing Countries - A Planning Manual. Duebendorf: Swiss Federal Institute for Environmental Science (EAWAG). URL [Accessed: 23.06.2010]. PDF

    This manual is a first approach to provide guidance on strategic planning of faecal sludge management. The study took place in the City of Nam Dinh, in Vietnam. The main principles for strategic sanitation planning have been adopted from the guide “Strategic Planning for Municipal Planning” from GHK Research and Training Ltd.

  • Cover image of a reference book or miscellany.

    MONTANGERO, A.; STRAUSS, M. (2004): Faecal Sludge Treatment. Duebendorf: Swiss Federal Institute of Aquatic Science (EAWAG), Department of Water and Sanitation in Developing Countries (SANDEC). URL [Accessed: 10.06.2010]. PDF

    This document reviews current practices of faecal sludge management and treatment.

  • Cover image of a reference book or miscellany.

    MONVOIS, J.; GABERT, J.; FRENOUX, C.; GUILLAUME, M. (2010): How to Select Appropriate Technical Solutions for Sanitation. Cotonou and Paris: Partenariat pour le Développement Municipal (PDM) and Programme Solidarité Eau (pS-Eau). URL [Accessed: 19.10.2011]. PDF

    The purpose of this guide is to assist local contracting authorities and their partners in identifying those sanitation technologies best suited to the different contexts that exist within their town. The first part of the guide contains a planning process and a set of criteria to be completed; these assist you in characterizing each area of intervention so that you are then in a position to identify the most appropriate technical solutions. The second part of the guide consists of technical factsheets which give a practical overview of the technical and economic characteristics, the operating principle and the pros and cons of the 29 sanitation technology options most commonly used in sub-Saharan Africa.

  • Cover image of a reference book or miscellany.

    STRANDE, L. (Editor); RONTELTAP, M. (Editor); BRDJANOVIC, D. (Editor) (2014): Faecal Sludge Management. Systems Approach for Implementation and Operation. London: IWA Publishing. URL [Accessed: 16.07.2014]. PDF

    This is the first book to compile the current state of knowledge on faecal sludge management. It addresses the organization of the entire faecal sludge management service chain, from the collection and transport of sludge, to the current state of knowledge of treatment options, and the final end use or disposal of treated sludge. It presents an integrated approach that brings together technology, management, and planning, based on Sandec’s 20 years of experience in the field. It also discusses important factors to consider when evaluating and upscaling new treatment technology options. The book is designed for undergraduate and graduate students, engineers, and practitioners in the field who have some basic knowledge of environmental and/or wastewater engineering.

  • Cover image of a reference book or miscellany.

    STRAUSS, M.; DRESCHER, S.; ZURBRUEGG, C.; MONTANGERO, A.; OLUFUNKE, C.; DRECHSEL, P. (2003): Co-composting of Faecal Sludge and Municipal Organic Waste. Swiss Federal Institute of Aquatic Science (EAWAG), Department of Water and Sanitation in Developing Countries (SANDEC) and International Water Management Institute (IWMI). URL [Accessed: 23.06.2010]. PDF

    The document gives an overview on the combined composting of (faecal) sludges and organic solid waste based on a pilot project in Kumasi, Ghana. Results of the investigation should help the city’s waste management department to develop its biosolids management strategy and enable the project team to develop guidelines for planners and engineers on the option of co-composting.

  • Cover image of a reference journal article.

    STRAUSS, M.; LARMIE, S.A.; HEINSS, U. (1997): Treatment of sludges from on-site sanitation — Low-cost options. In: Water Science and Technology 6, 129.URL [Accessed: 23.06.2010]. PDF

    Published in 1997, this article gives an overview on current literature-based knowledge regarding faecal sludge treatment along with results and conclusions from field research.

  • Cover image of a reference book or miscellany.

    TILLEY, E.; ULRICH, L.; LUETHI, C.; REYMOND, P.; ZURBRUEGG, C. (2014): Compendium of Sanitation Systems and Technologies. 2nd Revised Edition. Duebendorf, Switzerland: Swiss Federal Institute of Aquatic Science and Technology (Eawag). URL [Accessed: 28.07.2014]. PDF

    This compendium gives a systematic overview on different sanitation systems and technologies and describes a wide range of available low-cost sanitation technologies.

Case Studies

  • Cover image of a reference journal article.

    KONE, D.; KENGE, I. (2008): Technology Transfer – Forage Plants Used in Faecal Sludge Dewatering Beds in Sub-Saharan Africa. In: Sandec News 9. PDF

    In collaboration with the Asian Institute of Technology (AIT), Bangkok, Eawag has previously demonstrated that constructed wetlands, especially in Thailand, offer a viable solution for the treatment of faecal sludge. However, since the characteristics of sludge vary widely from one region to another, appropriate indigenous plants had to be identified so as to ensure successful operation of these facilities.

  • Cover image of a reference book or miscellany.

    KONE, D.; STRAUSS, M. (2004): Low-cost Options for Treating Faecal Sludges (FS) in Developing Countries - Challenges and Performance. Duebendorf: Water and Sanitation in Developing Countries (SANDEC), Swiss Federal Institute for Environmental Science (EAWAG). URL [Accessed: 23.06.2010]. PDF

    This article analyses and discusses the performances of low-cost technology for treating faecal sludges in developing countries. It shows that where septic tanks are the predominant type of on-site sanitation installations, septage is the only or predominant type of faecal sludge generated. It also shows that constructed wetlands, settling tanks/ponds, or unplanted drying beds might prove suitable as a pre-treatment.

  • Cover image of a reference chapter of a book/miscellany.

    WAFLER, M. (2006): Chapter 3. Pilot Project "Navsarjan Vocational Training Institute Dalit Shakti Kendra". In: WAFLER, M.; HEEB, J. (2006): Report on Case Studies of ecosan Pilot Projects in India. Eschborn. URL [Accessed: 26.04.2010]. PDF

    The main aim of the project was to avoid manual scavenging of excreta and to improve the sanitation situation at the Navsarjan Vocational Training Institute. The technical solution proposed was source separation (grey-/blackwater) and reuse. Greywater is separately treated and reused in the garden while the urine and faeces (blackwater) are directly introduced into a biogas plant. Digested sludge is dried on basic drying beds and used as compost for the garden. UDDT were also installed. The concept was implemented and evaluated for its social and cultural acceptability, sustainable and hygienic safety.

  • Cover image of a reference book or miscellany.

    ZIMMERMANN, N.; WAFLER, M. (2009): Decentralized Wastewater Mgmt at Adarsh College, Badalapur, Maharashtra, India. Eschborn: Sustainable Sanitation Alliance (SuSanA). URL [Accessed: 22.05.2012]. PDF

    This case study reports the development of an ecologically sound sanitation concept at Adarsh Bidyaprasarak Sanstha's College of Arts & Commerce. It comprises separate urine collection and a DEWATS system for the treatment of black- and greywater consisting of biogas settler, an anaerobic baffled reactor, and anaerobic filter, a horizontal flow wetland and a polishing pond.

Awareness Material

  • Cover image of a reference journal article.

    STRAUSS, M.; BARREIRO, W.C.; STEINER, M.; MENSAH, A.; JEULAND, M.; BOLOMEY, S.; MONTANGERO, A.; KONE, D. (2003): Urban Excreta Management - Situation, Challenges, and Promising Solutions. In: IWA Asia-Pacific Regional Conference Bangkok, Thailand.URL [Accessed: 23.06.2010]. PDF

    The objective of this paper is to render planners, decision makers, and consultants aware that faecal sludge management (FSM) should form an integral part of the urban development planning process. For this, three illustrative cases are presented, based on which an array of measures or tools, as well as institutional/regulatory, financial/economic, and technical aspects are discussed.

Training Material

  • Cover image of a reference book or miscellany.

    EAWAG/SANDEC (Editor) (2008): Faecal Sludge Management. Lecture Notes. Duebendorf: Swiss Federal Institute of Aquatic Science (EAWAG), Department of Water and Sanitation in Developing Countries (SANDEC). URL [Accessed: 23.05.2012]. PDF

    This module pays special attention to the haulage, treatment and reuse or disposal of faecal sludge. It covers both technical and non-technical (socio-cultural, economic, political etc.) aspects and provides practical information on design, financing and planning of faecal sludge treatment plants.

  • Cover image of a reference book or miscellany.

    EAWAG (Editor); SANDEC (Editor) (2008): Faecal Sludge Management. Pdf Presentation. Duebendorf: Swiss Federal Institute of Aquatic Science (Eawag), Department of Water and Sanitation in Developing Countries (Sandec). URL [Accessed: 23.05.2012]. PDF

    A presentation about faecal sludge management in developing countries.

  • Cover image of a reference book or miscellany.

    MONTANGERO, A.; STRAUSS, M. (2004): Faecal Sludge Treatment. Duebendorf: Swiss Federal Institute of Aquatic Science (EAWAG), Department of Water and Sanitation in Developing Countries (SANDEC). URL [Accessed: 10.06.2010]. PDF

    This document reviews current practices of faecal sludge management and treatment.

  • Cover image of a reference book or miscellany.

    SASSE, L. ; BORDA (Editor) (1998): DEWATS. Decentralised Wastewater Treatment in Developing Countries. Bremen: Bremen Overseas Research and Development Association (BORDA). PDF

    Exhaustive report on technological, operational and economic aspects of decentralised waste water treatment systems. Spreadsheet examples support the reader in designing and planning waste water treatment systems components.

  • Cover image of a reference book or miscellany.

    UNEP (Editor); MURDOCH UNIVERSITY (Editor) (2004): Environmentally sound technologies in wastewater treatment for the implementation of the UNEP/GPA "Guidelines on Municipal Wastewater Management". The Hague: United Nations Environment Programme Global Programme of Action (UNEP/GPA), Coordination Office. PDF

    Technical information on environmentally sound technologies in wastewater treatment.

Important Weblinks

  • http://www.unep.or.jp/ [Accessed: 23.06.2010]

    Link to the online version of the “International Source Book On Environmentally Sound Technologies for Wastewater and Stormwater Management” from the United Nations Environmental Programme. This section is about drying beds.