Biogas Settler

Compiled by:
Eawag (Swiss Federal Institute of Aquatic Science and Technology), Denise Staubli (seecon international gmbh), Dorothee Spuhler (seecon international gmbh)
Adapted from:
TILLEY, E.; ULRICH, L.; LUETHI, C.; REYMOND, P.; ZURBRUEGG, C. (2014)

Executive Summary

A settler is a primary treatment technology for wastewater; it is designed to remove suspended solids by sedimentation. It may also be referred to as a sedimentation or settling basin/tank, or clarifier. The low flow velocity in a settler allows settleable particles to sink to the bottom, while constituents lighter than water float to the surface. The liquid phase continues to further treatment steps after a relatively short hydraulic retention time, while the sludge is kept in the tank for several months to years. In airtight settlers, known as anaerobic biogas settlers, sludge is transformed to biogas via anaerobic digestion. The reactors are round or square - much like a septic tank, but with biogas collection. Biogas thus recovered can be transformed into heat, light or any other energy. The remaining slurry is almost pathogen free and can be used as a soil amendment (optionally after an aerobic composting post-treatment or drying/humification in a sludge drying bed). Biogas settlers are most often used at community or institutional level as first treatment step of decentralized wastewater treatment systems (DEWATS) for the pre-treatment of biodegradable domestic or industrial wastewaters.

In Out

Blackwater, Faecal Sludge, Greywater, Brownwater, Faeces, Excreta, Organic Solid Waste

Fertigation Water, Biogas, Compost/Biosolids

Introduction

 TILLEY et al. (2014)

Schematic of a biogas settler. Source: TILLEY et al. (2014)


Sedimentation is also used for the removal of grit (see pretreatement technologies), for secondary clarification in activated sludge treatment (see activated sludge), after chemical coagulation/precipitation, or for sludge thickening. This technology information sheet discusses the use of settlers as primary clarifiers, which are typically installed after a pretreatement technology, and specifically focuses on the use of one type of settlers, the anaerobic biogas settlers (see also anaerobic digestion).

 Fergus (2005)

Primary settling tank with automatic skimmer. Source: unknown.

Settlers can achieve a significant initial reduction in suspended solids (50-70% removal) and organic material (20-40% BOD removal) and ensure that these constituents do not impair subsequent treatment processes.

Settlers may take a variety of forms, sometimes fulfilling additional functions. They can be independent tanks or integrated into combined treatment units. Several other technologies in this Compendium have a primary sedimentation function or include a compartment for primary settling:

o    the septic tank, where the low sludge removal frequency leads to anaerobic degradation of the sludge.

o    the anaerobic baffled reactor and the anaerobic filter both usually include a settler as the first compartment. However, the settler may also be built separately, e.g., in municipal treatment plants or in the case of prefabricated, modular units.

o    the biogas reactor, which can be considered as a settler designed for anaerobic digestion and biogas production.

o    the Imhoff tank and the upflow anaerobic sludge blanket reactor, designed for the digestion of the settled sludge, prevent gases or sludge particles in the lower section from entering/returning to the upper section.

o    the waste stabilisation ponds, of which the first anaerobic pond is for settling

o    the sedimentation/thickening ponds, which are designed for the solid-liquid separation of faecal sludge

o    the solids-free sewer, which includes interceptor tanks at the building level.

Biogas settlers function much like septic tanks with the difference that biogas is recovered. Biogas, a mixture of methane (CH4) and carbon dioxide (CO2) can be used either directly for cooking and lighting or it can be transformed into heat in a gas heater system or into combined heat and power (CHP) in a cogeneration unit (MES et al. 2003; JENSSEN et al. 2004; WRAPAI 2009). Find more information in the small-scale conversion of biogas to electricity or the direct use of biogas factsheet. The nutrient-rich remaining sludge can be used as fertilizing soil amendment in agriculture (see also Reuse of Urine and Faeces in Agriculture and Reuse of Blackwater and Greywater). The liquor, optionally after further treatment, can be used for fertigation.

 terranet.or.id, borda-sea.org, whrefresh.com, BUNNY & BESSELINK (n.y.) and greenspec.co.uk

Anaerobic biogas settlers are often part of decentralised wastewater treatment systems (e.g. DEWATS) and function as a primary settling treatment that allows for collection of biogas. SOURCE: D.SPUHLER 2010 adapted from: terranet.or.id, borda-sea.org, whrefresh.com, BUNNY & BESSELINK (n.y.) and greenspec.co.uk

Design Considerations

The main purpose of a settler is to facilitate sedimentation by reducing the velocity and turbulence of the wastewater stream. Settlers are circular or rectangular tanks that are typically designed for a hydraulic retention time of 1.5-2.5 h. Less time is needed if the BOD level should not be too low for the following biological step. The tank should be designed to ensure satisfactory performance at peak flow. In order to prevent eddy currents and short-circuiting, as well as to retain scum inside the basin, a good inlet and outlet construction with an efficient distribution and collection system (baffles, weirs or T-shaped pipes) is important.

Depending on the design, desludging can be done using a hand pump, airlift, vacuum pump, or by gravity using a bottom outlet. Large primary clarifiers are often equipped with mechanical collectors that continually scrape the settled solids towards a sludge hopper in the base of the tank, from where it is pumped to sludge treatment facilities. A sufficiently sloped tank bottom facilitates sludge removal. Scum removal can also be done either manually or by a collection mechanism.

The efficiency of the primary settler depends on factors like wastewater characteristics, retention time and sludge withdrawal rate. It may be reduced by wind-induced circulation, thermal convection and density currents due to temperature differentials, and, in hot climates, thermal stratification. These phenomena can lead to short-circuiting.

Several possibilities exist to enhance the performance of Settlers. Examples include the installation of inclined plates (lamellae) and tubes, which increases the settling area, or the use of chemical coagulants.

Design Principles of a Biogas Settler

Biogas settlers are similar in construction and design as fixed-dome or floating drum biogas plants (see also small-scale biogas digesters). However, in opposition to biogas reactors, biogas settlers are designed for the retention of biomass and are thus typical high-rate biogas reactors. Other high-rate biogas plants are anaerobic baffled reactors (ABRs); anaerobic filters; and up-flow anaerobic sludge blanket reactors. High-rate biogas reactors are characterised by a mixed flow regime: the liquid (e.g. flushing, anal cleansing or greywater) flows through (continuous flow), while the sludge (e.g. faeces, paper etc.) is retained (batch) and treated over a long time until it is removed and used as fertiliser. Thus, biogas settlers are characterised by relatively short hydraulic retention times (HRT) for the liquor and high sludge retention times (SRT) for the solid fraction (organics and inorganics). The settled sludge is transformed into biogas by anaerobic digestion (see also anaerobic treatment of waste and wastewaters). Gas bubbles to the top of the reactor are collected for use.

 SPUHLER 2010).

Anaerobic digestion: complex organic molecules, proteins and fats are broken down in a four step process in to a mixture of methane (CH4) and carbon dioxide (CO2) and some trace gasses. The biogas can be collected and the CH4 used as a combustible. Source: D.SPUHLER (2010).

Biogas settlers can achieve up to 80 to 85 % of removal of biological oxygen demand (BOD) and chemical oxygen demand (COD) (WSP 2007), but the efficiency strongly depends on the settling properties of the organic matter and the HRT and SRT. As a large fraction of the organic matter is volatilised into biogas, sludge production is very low and the reactors need to be emptied only once every several years (i.e. = SRT).

Biomass retention in the biogas settlers may be achieved by gravity settling. Thus, as in any settling unit there needs to be an outlet for the supernatant liquid in the upper part of the reactor on the opposite site from the inlet. Baffles of any kind further enhance the retention of the biomass by holding back unsuspended solid compounds of the inflowing wastewater.


 SPUHLER (2006) and GTZ in BALASUBRAMANIYAM (2008)

A floating-drum biogas settler with the outlet being placed slightly below the supernatant level (left). Fixed dome biogas settler Nicarao design (right): 1. Mixing tank with inlet pipe and sand trap. 2. Digester. 3. Compensation and removal tank. 4. Gasholder. 5. Gas pipe. 6. Entry hatch, with gastight seal. 7. Accumulation of thick sludge. 8. Outlet pipe for sludge. 9. Reference level and outlet for liquor. 10. Supernatant scum, broken up by varying level. Source: SPUHLER (2006) and GTZ in BALASUBRAMANIYAM (2008)

 adapted from HEEB (2009)

A biogas settler with baffle in the middle to enhance settling of solids and retain biomass. Source: adapted from HEEB (2009)


Application of biogas settlers

Anaerobic biogas settlers are most often used as a primary settling treatment in decentralised wastewater treatment systems (e.g. DEWATS). In a typical DEWATS, biogas settlers are followed by a secondary anaerobic treatment using fixed-bed reactors (e.g. ABRs or AFs) and a tertiary aerobic treatment for polishing (surface, horizontal or vertical flow constructed wetlands or maturation ponds) (SCHMIDT 2008; MUELLER 2009). The final effluent can be used for fertigation. The requirement of treatment of the liquor flowing out of the settler depends on the HRT (WAFLER 2008). In the case of small plants, with relatively high HRTs, fixed-bed reactors may not be required if the liquor is reused for fertigation.

Biogas settlers as a primary treatment are adapted best to receive black- and brownwater and industrial high-strength wastewater as long as the wastes are biodegradable (e.g. slaughterhouse wastewater). Brownwater from urine diverting toilets has the advantage to contain less nitrogen than blackwater. This nitrogen is in the form of ammonia, which will be transformed into carbon dioxide, ammoniac and urea, both toxic to bacteria (MANG 2005).

 LEBOFA (n.y.)

Sketch of biogas reactor replacing a septic tank as part of a DEWATS system. Wastewater as well as kitchen and garden waste enter the digester and are broken down to biogas and fertile water. The advantage of such systems is that they need to be less often emptied than septic tank and that both, water and the biogas can be reused. Source: LEBOFA (n.y.)

Greywater can be added to the system after the biogas settler to be treated along with the supernatant coming from the settling unit. Besides these wastes which are brought to the DEWATS system by sewers, they can also be used for the off-site treatment of faecal sludge or night-soil from on-site sanitation systems (optionally other organic wastes can be added for co-digestion), which have been transported to the decentralised system by cartage (EAWAG/SANDEC 2008; MULLER 2009). The remaining sludge is generally more or less hygienised, depending on the SRT and the mixing of the old sludge with the new one. As anaerobic digestion mostly removes organics, large amounts of the nutrients remain in the sludge, making it to a valuable solid fertiliser. Almost 100 % of the phosphorus and about 50 to 70 % of the nitrogen as ammonium remains in the digested sludge (JOENSSEN 2004). To enhance the stabilisation of the sludge before reuse, it can be transformed into humus by small or large-scale composting (e.g. together with organic wastes) or further proceeded in drying beds (planted or unplanted) or thickening ponds and settling tanks. After these steps, the final product will be hygienically safe.

 SCHMIDT (2005)

A decentralised treatment station of faecal sludge with a primary biogas settler. Source: SCHMIDT (2005)

Health Aspects/Acceptance

To prevent the release of odorous gases, frequent sludge removal is necessary. Sludge and scum must be handled with care as they contain high levels of pathogenic organisms; they require further treatment and adequate disposal. Appropriate protective clothing is necessary for workers who may come in contact with the effluent, scum or sludge.

In strictly anaerobic biogas settlers, most of the pathogens are destroyed (FAO 1996). However, the state of hygienisation of the effluent slurry of biogas digesters strongly depends on the influent concentration in pathogenic microorganisms, the retention time, the temperatures and the mixing of the old sludge with the fresh one. High temperatures and long retention times are more hygienic (SASSE 1988). If more than 55°C were achieved for one to a few days inactivation can be considered as efficient (SCHOENNING & STENSTROEM 2004). To enhance the stabilisation of the remaining sludge before reuse aerobic composting is an adapted post-treatment.

Costs Considerations

The costs of settlers mainly depend on their size and type. Investment cost of anaerobic settlers is moderate and the potential of self-help for construction is relatively high. However, planning and design requires skilled labour and experienced experts. Both biogas and fertilising sludge make biogas sanitation technology highly interesting from an economic point of view.

Operation & Maintenance

In settlers that are not designed for anaerobic processes, regular sludge removal is necessary to prevent septic conditions and the build-up and release of gas which can hamper the sedimentation process by re-suspending part of the settled solids. Sludge transported to the surface by gas bubbles is difficult to remove and may pass to the next treatment stage.

Frequent scum removal and adequate treatment/disposal, either with the sludge or separately, is also important.

Anaerobic settlers do have to be emptied less frequent as the organic material is partly  transformed into gas. Accumulated slurry in the bottom of the reactor needs to be de-sludged every two to five years, depending on the type of reactor (UNEP 2002, MANG 2005). For the operation and maintenance of anaerobic biogas settlers, operational requirements are very low and no professional operator is required as long as the plant is well maintained by skilled users. Starting with the seeding of some sludge form a septic tank or another anaerobic digester speeds up the digestion and prevents the digester from running acid (SASSE 1998).

At a Glance

Working Principle

Biogas settlers are often used as a primary settling treatment and function much like septic tanks, with the difference that biogas is recovered. Wastewater and organic wastes are introduced in an airtight reactor, solids settle to the bottom, where they are decomposed by anaerobic digestion and transformed to biogas and fertilising slurry. The supernatant flows to further treatment steps or the storage tank to be reused for irrigation.

Capacity/Adequacy

Biogas settlers are most suited for decentralised wastewater treatment systems at household, community or institutional level. They are applicable in both urban and rural areas as long as the wastewater contains sufficient organic matter and is biodegradable.

Performance

80 to 85 % BOD; Relatively high pathogen removal; N and P remain in the sludge; HRT of some days; SRT of several years

Costs

Low capital and low operating costs

Self-help Compatibility

Expert design is required and the construction needs to be supervised; operation staff needs to receive training to understand the functioning. Can be constructed with locally available material.

O&M

De-sludging every 2 to 5 years; Checking for gas-tightness should be done regularly.

Reliability

Resistant to shock loading. Reliable if operated and maintained well.

Main strength

High removal of organic pollutants without any requirement for energy; Generation of biogas and fertiliser (compost).

Main weakness

Expert design is required; The organic and solid content in the influent needs to monitored.

Applicability

The choice of a technology to settle the solids is governed by the size and type of the installation, the wastewater strength, the management capacities and the desirability of an anaerobic process, with or without biogas production.

Technologies that already include some type of primary sedimentation (listed above) do not need a separate settler. Many treatment technologies, however, require preliminary removal of solids in order to function properly. Although the installation of a primary sedimentation tank is often omitted in small activated sludge plants, it is of particular importance for technologies that use a filter material. Settlers can also be installed as stormwater retention tanks to remove a portion of the organic solids that otherwise would be directly discharged into the environment.

Biogas settlers are often used as primary settling treatment in DEWATS at the community or institutional level and the products (biogas and fertilising sludge) are best being reused on-site. Depending on the HRT, biogas settler effluents may require further treatment (e.g. in a ABR or constructed wetland) before reuse in fertigation. The sludge can be used as nutrient rich soil amendment, optionally after aerobic composting as post-treatment or drying/soilisation in a sludge drying bed. High ambient temperatures increase biogas production and sludge stabilisation. At low average temperature (below 15ºC mean temperature) biogas production is not interesting form an economical point of view.

Biogas settlers are a cost-effective treatment with low maintenance and operation. However, design and construction of biogas digesters demand exact knowledge of the influent characteristics (e.g. daily wastewater production, hourly peak flow, BOD/COD content) and climatic conditions (daily average temperatures, annual minimal temperatures etc.). Therefore, carful preliminary investigations and expert planning and design are required.

Advantages

  • Simple and robust technology
  • Efficient removal of suspended solids
  • Relatively low capital and operating cost
  • Generation of biogas and fertilizer
  • Avoids greenhouse gas emissions
  • Underground construction possible (low space requirement and high acceptance)
  • Low risk of odours and resistant against shock loads
  • Long life span if maintained and operated correctly

Disadvantages

  • Experts are required for the design of the reactor and skilled labour is required for the construction of a gas-tight tank
  • Frequent sludge removal for settlers that are not designed for anaerobic processes
  • Effluent, sludge and scum require further treatment
  • Short-circuiting can be a problem
  • Slurry may has to be further treated before reuse (i.e. post-composting)
  • Gas production at low temperatures is not interesting from an economic point of view
  • TS and BOD content as well as C/N ration need to be appropriated

References Library

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CRITES, R.; TCHOBANOGLOUS, G. (1998): Small and Decentralized Wastewater Management Systems. New York: The McGraw-Hill Companies Inc.

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EAWAG/SANDEC (Editor) (2008): Faecal Sludge Management. Lecture Notes. (= Sandec Training Tool 1.0, Module 5). Duebendorf: Swiss Federal Institute of Aquatic Science (EAWAG), Department of Water and Sanitation in Developing Countries (SANDEC). URL [Accessed: 23.05.2012].

ECKENFELDER, W.W.; PATOZKA, J.B.; PULLIAM, G.W. (1988): Anaerobic Versus Aerobic Treatment in the USA. In: Proceedings of the 5th International Symposium of Anaerobic Digestion, 105-114 . URL [Accessed: 05.08.2010].

FAO (Editor) (1996): Biogas Technology - A Training Manual for Extension. Support for Development of National Biogas Programme (FAO/TCP/NEP/4451-T) . Consolidated Management Services Nepal (P) Ltd. and Food and Agriculture Organization of the United Nations (FAO). URL [Accessed: 19.04.2010].

GTZ (Editor) (2007): MDG monitoring for urban water supply and sanitation. Catching up with reality in Sub-Saharan Africa. German Technical Cooperation (GTZ). URL [Accessed: 25.01.2011].

HEEB, F. (2009): Decentralised anaerobic digestion of market waste. Case study in Thiruvananthapuram, India. Duebendorf: Swiss Federal Institute of Aquatic Science and Technology (EAWAG). URL [Accessed: 27.04.2010].

ISAT (Editor); GTZ (Editor) (1999): Biogas Basics. (= Biogas Digest, 1). Information and Advisory Services on Appropriate Technology (ISAT) and German Agency for Technical Cooperation GmbH (GTZ) . URL [Accessed: 19.04.2010].

JENSSEN, P.D.; GREATOREX, J.M.; WARNER, W. S. (Editor) (2004): Sustainable Wastewater Management in Urban Areas. (= Kapitel 4. Kurs WH33, Konzeptionen dezentralisierter Abwasserreinigung und Stoffstrommanagement). Hannover: University of Hannover.

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LEBOFA, M. (n.y.): Demand Oriented Biogas Technology Extension in Lesotho. Technologies of Economic Development. URL [Accessed: 16.08.2010].

MANG, H. P. (2005): Biogas Sanitation Systems. (= Ecological sanitation course). Beijing: Chinese Academy of Agricultural Engineering.

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MUELLER, C. (2009): Decentralised Co-Digestion of Faecal Sludge with Organic Solid Waste. Case Study in Maseru, Lesotho. Duebendorf: Swiss Federal Institute of Aquatic Science (EAWAG), Department of Water and Sanitation in Developing Countries (SANDEC). URL [Accessed: 27.04.2010].

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GUTTERER, B.; SASSE, L.; PANZERBIETER, T.; RECKERZÜGEL, T.; ULRICH, A. (Editor); REUTER, S. (Editor); GUTTERER, B. (Editor) (2009): Decentralised Wastewater Treatment Systems (DEWATS) and Sanitation in Developing Countries. Loughborough University (UK): Water Engineering and Deveopment Centre (WEDC). URL [Accessed: 20.03.2014].

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Further Readings Library

Reference icon

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

This is the Arabic version of the Compendium of Sanitation Systems and Technologies. The Compendium gives a systematic overview on different sanitation systems and technologies and describes a wide range of available low-cost sanitation technologies.


Reference icon

ASIKAINEN, V. (2004): Environmental Impact of Household Biogas Pants in India — Local and Global Perspective. (= Master Thesis). Jyvaskyla: University of Jyvaskyla.

In this study, the environmental impacts of biogas technology in India were studied when biogas as a cooking fuel substitutes bio-fuels (fuel wood, dung and crop residues) and fossil fuels (Kerosene and LPG)


Reference icon

BALASUBRAMANIYAM, U.; ZISENGWE, L.S.; MERIGGI, N.; BUYSMAN, E. (2008): Biogas Production in Climates with long cold Winters. Wageningen: Wageningen University . URL [Accessed: 20.04.2010].

This study analyses the feasibility and potential production of biogas in countries with a cold climate, with emphasis on Romania, Kyrgyzstan, Georgia, Kazakhstan and Armenia. The results are compared with China, Nepal and Bolivia. The study also carefully reviews existing literature before suggesting the same technology for the colder target communities. It also contains recommendations on whether to use the plants on household or community level afterwards.


Reference icon

CRITES, R.; TCHOBANOGLOUS, G. (1998): Small and Decentralized Wastewater Management Systems. New York: The McGraw-Hill Companies Inc.

Decentralised wastewater management presents a comprehensive approach to the design of both conventional and innovative systems for the treatment and disposal of wastewater or the reuse of treaded effluent. Smaller treatment plants, which are the concern of most new engineers, are the primary focus of this book.


Reference icon

DEKELVER, G.; RUZIGANA, S.; LAM, J. (2005): Report on the Feasibility Study for a Biogas Support Programme in the Republic of Rwanda. Netherlands Development Organisation (SNV) . URL [Accessed: 09.04.2010].

This report presents the findings of a study conducted by Ministry of Agriculture (MININFRA) and SNV to assess the feasibility to set-up and implement a national programme on domestic biogas in Rwanda.


Reference icon

EAWAG/SANDEC (Editor) (2008): Faecal Sludge Management. Lecture Notes. (= Sandec Training Tool 1.0, Module 5). Duebendorf: Swiss Federal Institute of Aquatic Science (EAWAG), Department of Water and Sanitation in Developing Countries (SANDEC). URL [Accessed: 23.05.2012].

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.


Reference icon

GTZ (Editor) (2007): Feasability Study for a National Domestic Biogas Programme in Burkina Faso. German Technical Cooperation (GTZ) GmbH. URL [Accessed: 21.04.2010].

This feasibility study resumes the current situation in Burkina Faso regarding social aspects, water and energy issues, agricultural and livestock sector activities, sanitation and environmental topics. It analyses the technical feasibility of currently available biogas digester designs for standardization and massive dissemination in the context of Burkina Faso. Also an outline of a National Domestic Biogas Programme is presented.


Reference icon

GUTTERER, B.; SASSE, L.; PANZERBIETER, T.; RECKERZÜGEL, T.; ULRICH, A. (Editor); REUTER, S. (Editor); GUTTERER, B. (Editor) (2009): Decentralised Wastewater Treatment Systems (DEWATS) and Sanitation in Developing Countries. Loughborough University (UK): Water Engineering and Deveopment Centre (WEDC). URL [Accessed: 20.03.2014].

This document speaks about waste water and sanitation strategies in the developing countries. It also advocates the use of DEWATS as sustainable treatment of waste water at a local level backing it up with case studies from different countries. It describes various options available for sanitation and waste water treatment. It gives an idea of planning and executing CBS programs.


Reference icon

MANG, H.-P.; LI, Z. (2010): Technology Review of Biogas Sanitation. (= Technology Review ). Eschborn: Deutsche Gesellschaft für Internationale Zusammenarbeit (GIZ) GmbH. URL [Accessed: 17.06.2013].

This document provides an overview and introduction on biogas sanitation (anaerobic digestion) for blackwater or for brown water, or excreta treatment for reuse in developing countries. The main technologies discussed are biogas settlers (BSs), biogas septic tanks, anaerobic baffled reactor (ABRs), anaerobic filter (AFs) and upflow anaerobic sludge blanket reactors (UASBs).


Reference icon

MOREL, A.; DIENER, S. (2006): Greywater Management in Low and Middle-Income Countries, Review of Different Treatment Systems for Households or Neighbourhoods. (= SANDEC Report No. 14/06). Duebendorf: Swiss Federal Institute of Aquatic Science (EAWAG), Department of Water and Sanitation in Developing Countries (SANDEC). URL [Accessed: 19.05.2010].

This report compiles international experience in greywater management on household and neighbourhood level in low and middle-income countries. The documented systems, which vary significantly in terms of complexity, performance and costs, range from simple systems for single-house applications (e.g. local infiltration or garden irrigation) to rather complex treatment trains for neighbourhoods (e.g. series of vertical and horizontal-flow planted soil filters).


Reference icon

MUENCH, E. (2008): Overview of anaerobic treatment options for sustainable sanitation systems. In: BGR Symposium "Coupling Sustainable Sanitation and Groundwater Protection". URL [Accessed: 23.04.2010].

PDF presentation about condominium-level biogas digesters for the transformation of human faeces. Biogas basics as well as two case studies (from Germany and India) are presented.


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PETER-FROEHLICH, A.; BONHOMME, A.; OLDENBURG, M. (2007): Sanitation Concepts for Separate Treatment of Urine, Faeces and Greywater (SCST) – Results. EU-Demonstration project.

Report of a European project with the objective to develop new sustainable sanitation concepts that have significant ecological and economic advantages compared to conventional end-of-pipe-systems. For this purpose, a demonstration plant was constructed and analysed in order to generate experiences on design, installation and operation.


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ROBBINS, D.M.; LIGON, G.C. (2014): How to Design Wastewater Systems for Local Conditions in Developing Countries. London: International Water Association (IWA). URL [Accessed: 20.01.2015].

This manual provides guidance in the design of wastewater systems in developing country settings. It promotes a context-specific approach to technology selection by guiding the user to select the most suitable technologies for their area. It provides tools and field guides for source characterization and site evaluation, as well as technology identification and selection. This manual is primarily addressed to private and public sector service providers, regulators and engineers/development specialists in charge of implementing wastewater systems.


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ROUSE; ROTHENBERGER, S.; ZURBRUEGG, C. (2008): Marketing Compost. A Guide for Compost Producers in Low and Middle-Income Countries. Duebendorf: Water and Sanitation in Developing Countries (SANDEC), Swiss Federal Institute for Environmental Science (EAWAG). URL [Accessed: 05.05.2010].

This guide describes a marketing approach to composting, and is intended to help compost producers run more viable initiatives by unlocking the value of their product. The handbook does not cover everything there is to know about marketing, but starts with the basics and introduces the key principles and techniques. These include understanding the ‘marketing environment’, identifying appropriate target customer groups, and developing and promoting products to suit the market.


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SCHMIDT, A. (2008): Decentralized Wastewater treatment system. In: 3rd WISA Appropriate Technologies Conference 20-21 October 2008 Accra, Ghana. URL [Accessed: 16.08.2010].

PDF presentation on decentralised wastewater treatment systems (comprising biogas production and reuse of sludge and effluent water) at household or community level.


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SINHA, S. (2005): DEWATS linked Biogas. (= PDF presentation). Bangalore: Bremen Overseas Research and Development Agency (BORDA) India . URL [Accessed: 13.04.2010].

PDF-presentation on decentralised wastewater treatment systems (DEWATS) comprising a biogas settler; an anaerobic baffled reactor; a planted gravel filter and finally a storage tank for reuse for irrigation.


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SINHA, S.; KAZAGLIS, A. (n.y.): BIOGAS and DEWATS, a perfect match?. Bremen: Bremen Overseas Research and Development Agency (BORDA). URL [Accessed: 13.04.2010].

The resources gained from DEWATS-linked biogas digesters (gas for cooking), when combined with adequate social interventions, have resulted in increased acceptance of the DEWATS installations by communities and institutions. Two case studies in Bangalore, India illustrate this approach of the Bremen Overseas Research and Development Association (BORDA).


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SUSANA (Editor) (2009): Links between Sanitation, Climate Change and Renewable Energies. Eschborn. (= SuSanA fact sheet 09/2009). Sustainable Sanitation Alliance (SuSanA) . URL [Accessed: 05.09.2010].

This factsheet of Sustainable Sanitation Alliance describes the impact of greenhouse gases on climate change and focuses on the advantages of renewable energies. Therefore many different technologies like production of biogas or short-rotation-plantations are mentioned.


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U.S. EPA (2003): Wastewater Technology Fact Sheet: Screening and Grit Removal. Washington: Environmental Protection Agency (EPA). URL [Accessed: 20.03.2014].

The following document is Wastewater Technology Fact Sheet describing the pre-treatment processes of screening and grit removal using different technologies.


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UNEP (Editor) (2004): Chapter 4. Wastewater Technologies. In: UNEP (Editor) (2004): A Directory of Environmentally Sound Technologies for the Integrated Management of Solid, Liquid and Hazardous Waste for SIDS in the Caribbean Region. Nairobi, 63-125.

Comprehensive overview (in form of factsheets) on the different components of wastewater treatment systems (collection, transfer, onsite treatment, centralised and decentralised treatment, reuse, sludge management and disposal) adapted to the Caribbean Region. Industrial wastewater treatment is also discussed.


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WENDLAND, C. (2008): Anaerobic Digestion of Blackwater and Kitchen Refuse. (PhD Thesis). (= Hamburger Berichte zur Siedlungswasserwirtschaft). Hamburg: Institut fuer Abwasserwirtschaft und Gewaesserschutz (AWW), Technische Universitaet Hamburg-Hamburg (TUHH). URL [Accessed: 11.03.2010].

Thesis assessing the anaerobic treatment of blackwater (toilet wastewater) from vacuum toilets without and with kitchen refuse and its potential for reuse and resources management sanitation concepts.


Case Studies Library

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APEIS (Editor) (2003): Biogas Plants Based on Night Soil. Asia-Pacific Environmental Innovation Strategies (APEIS), Research on Innovative and Strategic Policy Options (RISPO). (=Good Practices Inventory). Sulabh International and Agency for Non Conventional Energy and Rural Technology (ANERT).

The government of India started its biogas development project in 1981 as one of its programs designed to meet rural energy needs, especially for cooking. One of the solutions to the problem was the introduction of the concept of pay-and-use toilets championed by the Sulabh International Social Service Organisation, a non-profit voluntary organisation pioneering in the field of sanitation in India. The biogas generated is used largely for public lighting. Sulabh community toilets linked to biogas plants are generating energy and fertilizer, and some of them have attached health care facilities as well.


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ASHDEN (Editor) (2005): Biogas plants providing sanitation and cooking fuel in Rwanda. London: The Ashden Awards for Sustainable Energy. URL [Accessed: 13.04.2010].

The Kigali Institute of Science, Technology and Management (KIST) has developed and installed large-scale biogas plants in prisons in Rwanda to treat toilet wastes and generate biogas for cooking. After the treatment, the bio-effluent is used as fertiliser for production of crops and fuel wood.


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BORDA (Editor) (2008): Decentralized Wastewater Treatment System -DEWATS. Animal Products Development Center, Bureau of Animal Industry (APDC-BAI). (= Sustainable Sanitation – Project Data Sheet). Bremen: Bremen Overseas Research and Development Association (BORDA).

The Animal Products Development Centre, Bureau of Animal Industry (APDC-BAI) together with Bremen Overseas Research and Development Association (BORDA) jointly developed this DEWATS system in the view of a resources-saving and environmental friendly management of slaughterhouses and meat processing wastes in the Philippines. The system comprises a closed small-scale sewer system, an anaerobic digester, an anaerobic baffled reactor (ABR), an anaerobic filter (AF) and an aerobic planted filter as a final step to reduce odours.


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BUTARE, A.; KIMARO, A. (2002): Anaerobic technology for toilet wastes management: the case study of the Cyangugu pilot project. In: World Transactions on Engineering and Technology Education 1, 147-152.

This article addresses the potential of anaerobic technology in the treatment and management of toilet wastes at schools, camps and prisons. It is based on the pilot project that was set up at Cyangugu prison in October 2000, Kigali, Rwanda.


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GEF (Editor) (n.y.): Biogas from Sewage and Residual Waters in an Educational Institution, Ecuador. The Global Environment Facility (GEF) Small Scale Grants Programme, United Nations Environment Programme (UNEP). URL [Accessed: 28.04.2010].

The project built a biogas digester in a School in Ecuador into which human and animal waste is deposited in order to produce biogas (methane), and fertilizer. During the school year, the waste of 500 people is required to operate the system effectively. During the summer, manure from surrounding farms and vegetable matter is used.


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GLUECKLICH, D.; FRIES, N. (n.y.): Sanitary Block - Biogas Plant. Fundamentals of Ecological Planning and Building. Weimar: Bauhaus-Universitaet Weimar.

This poster presents a sanitary block in Ghana. The wastewater and nutrient concept for the sanitary block includes the separation of the different flow streams, such as pure urine, urine-water mixture, blackwater and greywater, in order to optimise the system design and to collect the urine and urine-water mixture as a fertiliser. Blackwater is treated in a fixed-dome biogas settler.


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JHA, P.K. (n.y.): Recycling and reuse of human excreta from public toilets through biogas generation to improve sanitation, community health and environment. New Delhi: Sulabh International Academy of Environmental Sanitation. URL [Accessed: 12.08.2010].

This paper has been written by the Director General Sulabh International Academy of Environmental Sanitation, which is well known for the installations of over 100 biogas linked public toilets in India. It gives an overview on the Sulabh approach and deals with many issues in brief way, including technical, social and economical aspects.


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ISAT (Editor); GTZ (Editor) (1999): Biogas - Country Reports. (= Biogas Digest, 4). Information and Advisory Services on Appropriate Technology (ISAT) and German Agency for Technical Cooperation GmbH (GTZ). URL [Accessed: 19.04.2010].

The information service on biogas technology has been developed and produced on the behalf of the GTZ project Information and Advisory Service on Appropriate Technology (ISAT). Volume IV summarises over 20 case studies from biogas sanitation as an appropriate technology in developing countries.


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LEBOFA, M. (n.y.): Demand Oriented Biogas Technology Extension in Lesotho. Technologies of Economic Development. URL [Accessed: 16.08.2010].

Paper on the demand-oriented introduction of household-level biogas reactors.


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MARTIN, C. (2005): Urban Ecological Sanitation – Kuching is paving the way. Sarawak (Malaysia): Natural Resources and Environment Board (NREB). URL [Accessed: 20.03.2014].

This document tells us about the pilot project carried out by NREB at Hui Sing Garden, Kuching, Sarawak. It talks about the holistic approach towards integration of ecological sanitation and waste water treatment processes applied at a city level to fight the problem of river water pollution.


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MUELLER, C. (2009): Decentralised Co-Digestion of Faecal Sludge with Organic Solid Waste. Case Study in Maseru, Lesotho. Duebendorf: Swiss Federal Institute of Aquatic Science (EAWAG), Department of Water and Sanitation in Developing Countries (SANDEC). URL [Accessed: 27.04.2010].


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MUELLEGGER, E. (Editor); LANGERGRABER, G. (Editor); LECHNER, M. (Editor) (2011): Biogas Systems. (= Sustainable Sanitation Practice, 9). EcoSan Club. URL [Accessed: 24.10.2011].

During the last years a number of biogas systems have been installed as part of sanitation systems. Issue 9 of Sustainable Sanitation Practice (SSP) on „Biogas systems“ shows successful examples. The first paper presents results from a study in Kerala, India, for digesters on a household level. The second paper shows the results of a long-term implementation program for biogas systems in Lesotho. The third paper presents first results of a digester constructed in a small village in Morocco.


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MUENCH, E.; MANG, H.P.; SCHULTES, G.; PANESAR, A. (2005): Ten years of operational experiences with the ecosan-biogas plant at a family-owned farm and restaurant in Germany. (= 3rd International Conference on Ecological Sanitation 23 - 26 May 2005, Durban, South Africa). Pretoria: Council for Scientific and Industrial Research (CSIR). URL [Accessed: 13.04.2010].

Case study form a agricultural complex (containing farm, restaurant and slaughter house), which uses an integrated concept where wastewater and waste of the entire farm (agricultural activity, households, slaughter house and restaurant) are beneficially reused in a biogas plant. Today, about 10% of the German agricultural biogas plants are co-digesting household sewage along with the animal wastes. Unfortunately, the European standard for organic agriculture is not (yet) allowing this practise for certified agriculture.


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OTTER-WASSER (Editor) (2009): Ecological housing estate, Flintenbreite, Luebeck, Germany - draft. (= SuSanA - Case Studies). Eschborn: Sustainable Sanitation Alliance (SuSanA). URL [Accessed: 25.04.2010].

In the Flintenbreite in Luebeck, Germany, blackwater is collected in vacuum toilets. Together with organic wastes from the kitchen it is converted to biogas. Greywater is treated in a reed-bed filter. The project demonstrated the consistent utilisation of ecological building materials, the use of self-sustaining, integrated energy and wastewater concepts, and the implementation of innovative energy saving technologies, with a minimisation of interference in nature, and a responsible, integrative and active cohabitation of the inhabitants.


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RIECK, C.; ONYANGO, P. (2010): Public toilet with biogas plant and water kiosk, Naivasha, Kenya. (= SuSanA - Case Studies). Eschborn: Sustainable Sanitation Alliance (SuSanA). URL [Accessed: 12.12.2012].

A sanitation unit (toilet, hand wash basins, a urinal and showers) and a water kiosk were constructed for a public bus park (design sale was 1000 visitors per day). This projects aimed to improve living conditions of the residents and travellers by providing environmentally-friendly sanitation solutions with a focus on the reuse of the human waste as a resource and to find a business-oriented solution that creates economic incentives for the water sector institutions to invest in sanitation and to generate income for private operators.


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SINHA, S. (2005): DEWATS linked Biogas. (= PDF presentation). Bangalore: Bremen Overseas Research and Development Agency (BORDA) India . URL [Accessed: 13.04.2010].

PDF-presentation on decentralised wastewater treatment systems (DEWATS) comprising a biogas settler; an anaerobic baffled reactor; a planted gravel filter and finally a storage tank for reuse for irrigation.


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VOEGELI, Y.; LOHRI, C.R.; GALLARDO, A.; DIENER, S.; ZURBRUEGG, C.; EAWAG (Editor) (2014): Anaerobic Digestion of Biowaste in Developing Countries. Practical Information and Case Studies. Duebendorf: Swiss Federal Institute of Aquatic Science and Technology (Eawag). URL [Accessed: 03.03.2013].

This book published by Eawag/Sandec compiles existing and recently generated knowledge on anaerobic digestion of urban biowaste at small and medium scale with special consideration given to the conditions prevailing in developing countries. Written for actors working in the waste and renewable energy sector, the book is divided into two parts: Part 1 focuses on practical information related to the anaerobic digestion supply chain (substrate-, process-, and product chain), and Part 2 presents selected case studies from around the world.


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WAFLER, M. ; HEEB, J.; STAUB, A.; OLT, C. (2009): Pour-flush toilets with biogas plant at DSK Training Institute. Gujarat, India - Draft. (= SuSanA - Case Studies). Eschborn: Sustainable Sanitation Alliance (SuSanA). URL [Accessed: 25.04.2010].

The project described aimed at avoiding manual scavenging of faecal products and at improving the sanitation situation at the Navsarjan Vocational Training Institute. Now 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. UDDTs were also installed. The concept was implemented and evaluated for its social and cultural acceptability, sustainable and hygienic safety.


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XIANGJUN, Y.; WANG, H. (2003): Integrated systems on biogas production, non-polluted agricultural production and sanitation in rural China. In: Proceedings of the 2nd international symposium, F. 7th-11th April, Luebeck, Germany, 601-606.

This paper introduces three typical biogas systems which regard anaerobic fermentation of human and animal “wastes” as a key technology, and which link sanitation and biogas production with agricultural use of digested effluents.


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ZIMMERMANN, N.; WAFLER, M. (2009): Decentralized Wastewater Management at Adarsh College, Badalapur, Maharashtra, India. (= SuSanA - Case Studies). Eschborn: Sanitation Alliance (SuSanA). URL [Accessed: 25.04.2010].

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


Awareness Raising Material Library

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JENSSEN, P.D.; HEEB, J.; HUBA-MANG, E.; GNANAKAN, K.; WARNER, W.; REFSGAARD, K.; STENSTROEM, T.A.; GUTERSTRAM, B.; ALSEN, K.W. (2004): Ecological Sanitation and Reuse of Wastewater. Ecosan. A Thinkpiece on ecological sanitation. Norway: The Agricultural University of Norway. URL [Accessed: 19.04.2010].

This paper shows that there are comprehensive experiences and available technologies that meet new and sustainable sanitation requirements. Ecological sanitation constitutes a diversity of options for both rich and poor countries, from household level up to wastewater systems for mega-cities and needs to become recognised by decision-makers at all levels.


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NATURGERECHTE TECHNOLOGIEN (Editor); Bau- und Wirtschaftsberatung (TBW) GmbH (Editor) (2001): Anaerobic treatment of municipal wastewater treatment. (= Technical Information W3e). German Agency for Technical Cooperation GmbH (GTZ) and German Appropriate Technology Exchange (GATE). URL [Accessed: 11.03.2010].

Technical information on the advantages and main technologies of anaerobic digestion treatment for wastewaters in developing countries.


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NATURGERECHTE TECHNOLOGIEN, BAU- UND WIRTSCHAFTSBERATUNG (TBW) GmbH (Editor) (2001): Decentralised Wastewater Treatment Methods for Developing Countries. GTZ and GATE.

Different operation and maintenance options are presented with respect to sustainable plant operation, the use of local resources, knowledge, and manpower.


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TUHUS-DUBROW (2008): Waste? Not. In: The Boston Globe. URL [Accessed: 21.02.2010].

Critical article on conventional end-of-pipe wastewater approaches, introducing some alternatives such as biogas digester, arborloos or the fossa alterna.


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WAFLER, M. (2009): Reuse of Energy (Biogas). (PPT presentation). (= Ecosan Training Courses for TSC officials). Wien: seecon international GmbH.

PPT presentation on the advantages of biogas reuse.


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WELL (Editor) (n.y.): Using Human Waste. (= WELL Technical Briefs, 63). Loughborough: Water and Environmental health at London and Loughborough (WELL). URL [Accessed: 26.04.2010].

This Technical Brief introduces the main issues one needs to consider to both control the process and optimize the benefits gained from using human waste, whilst minimizing the risks.


Training Material Library

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D’AMATO, V. (2010): Webinar on Decentralized Wastewater Treatment Systems: Processes, Design, Management, and Use. November 23: Focus on Decentralized Wastewater System Design: Part 1. (= Webinar Series). Conservation Technology Information Center, US Environmental Protection Agency (EPA), and Tetra Tech. URL [Accessed: 15.05.2014].

US EPA Webinar on decentralized wastewater management with presentations on technical systems such as septic tanks and grease traps.


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EAWAG/SANDEC (Editor) (2008): Faecal Sludge Management. Lecture Notes. (= Sandec Training Tool 1.0, Module 5). Duebendorf: Swiss Federal Institute of Aquatic Science (EAWAG), Department of Water and Sanitation in Developing Countries (SANDEC). URL [Accessed: 23.05.2012].

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.


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FAO (Editor) (1996): Biogas Technology - A Training Manual for Extension. Support for Development of National Biogas Programme (FAO/TCP/NEP/4451-T) . Consolidated Management Services Nepal (P) Ltd. and Food and Agriculture Organization of the United Nations (FAO). URL [Accessed: 19.04.2010].

This manual contains a complete set of training materials on various topics around the large-scale dissemination of domestic (agricultural) biogas systems, including a system approach to biogas technology, biogas programmes, reuse of slurry, subsidy and institutional financing, quality standards and monitoring and evaluation issues.


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ISAT (Editor); GTZ (Editor) (1999): Biogas - Application and Product Development. (= Biogas Digest, 2). Information and Advisory Services on Appropriate Technology (ISAT) and German Technical Cooperation (GTZ) GmbH . URL [Accessed: 19.04.2010].

The information service on biogas technology has been developed and produced on the behalf of the GTZ project Information and Advisory Service on Appropriate Technology (ISAT). Volume II emphasises the design and operation of biogas plants.


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ISAT (Editor); GTZ (Editor) (1999): Biogas Basics. (= Biogas Digest, 1). Information and Advisory Services on Appropriate Technology (ISAT) and German Agency for Technical Cooperation GmbH (GTZ) . URL [Accessed: 19.04.2010].

The information service on biogas technology has been developed and produced on the behalf of the GTZ project Information and Advisory Service on Appropriate Technology (ISAT). Volume I tells you all you need to get an overview on biogas sanitation systems, from history over process and operation parameters to social, political and cultural issues.


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ISAT (Editor); GTZ (Editor) (1999): Biogas - Country Reports. (= Biogas Digest, 4). Information and Advisory Services on Appropriate Technology (ISAT) and German Agency for Technical Cooperation GmbH (GTZ). URL [Accessed: 19.04.2010].

The information service on biogas technology has been developed and produced on the behalf of the GTZ project Information and Advisory Service on Appropriate Technology (ISAT). Volume IV summarises over 20 case studies from biogas sanitation as an appropriate technology in developing countries.


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ISAT (Editor); GTZ (Editor) (1999): Biogas - Costs and Benefits and Biogas – Programme Implementation. (= Biogas Digest, 3). Information and Advisory Services on Appropriate Technology (ISAT) and German Agency for Technical Cooperation GmbH (GmbH) . URL [Accessed: 19.04.2010].

This information service on biogas technology has been developed and produced on the order of the GTZ project Information and Advisory Service on Appropriate Technology (ISAT). Volume III discusses the micro- and macro-economic viability of biogas sanitation systems.


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MANG, H. P. (2005): Biogas Sanitation Systems. (= Ecological sanitation course). Beijing: Chinese Academy of Agricultural Engineering.

This PDF-presentation gives a good introduction to biogas sanitation as a sustainable and ecological sanitation approach. Basic principles and main features are illustrated. Some design considerations are also addressed.


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MANG, H.P.; JURGA, I.P. (2005): Biogas Sanitation Systems. International Conference on Ecosan. Beijing: Chinese Academy of Agricultural Engineering. URL [Accessed: 12.08.2010].

PowerPoint compilation of Chinese Experience on Ecosan and Biogas.


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MANG, H. P. (n.y.): Introduction in the technical design for anaerobic treatment systems.

Powerpoint presentation on the design of anaerobic treatment systems. Questions are answered concerning the applicability, the advantages and disadvantages as well as the up-scaling of such measures.


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SASSE, L. (1988): Biogas Plants. German Appropriate Technology Exchange (GATE) and German Agency for Technical Cooperation (GTZ) GmbH. URL [Accessed: 15.05.2012].

This rather old document still gives a good overview on biogas technology. It is intended to help designers of a biogas plant to be able to distinguish between valid and invalid solutions.


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SASSE, L. (1991): Improved Biogas Unit for Developing Countries. German Appropriate Technology Exchange (GATE) and German Agency for Technical Cooperation (GTZ) GmbH. URL [Accessed: 25.04.2010].

This booklet reflects seven years of experience of the Biogas Extension Service (BES) of CAMARTEC (Centre for Agricultural Mechanization and Rural Technology) in Arusha/Tanzania, which was carried out in cooperation with the GTZ from 1983 to 1986. It is meant as a teaching aid in agricultural colleges and as a reference book for professionals working in the field of rural biogas extension.


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

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.


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SCHMIDT, A. (2005): Treatment of sludge from domestic on-site sanitation systems, septic tanks and latrines. Septage. Bremen: Bremen Overseas Research and Development Association (BORDA).

A DEWATS system for the treatment of faecal sludge from on-site sanitation is presented. It comprises an anaerobic digester (where biogas is produced), an anaerobic stabilisation reactor, an anaerobic baffled reactor and an aerobic gravel filter.


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WAFLER, M. (2008): Training Material on Anaerobic Wastewater Treatment. (= Ecosan Expert Training Course). Aarau: Seecon GmbH.

This training manual emphasizes basics of biogas technology as well as design principles and technical considerations. A sample design exercise and some technical drawings and sketches are also given.


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WSP (Editor) (2007): Philippines Sanitation Source Book and Decision Aid. pdf presentation. Washington: Water and Sanitation Program.

This Sanitation Sourcebook distils some of the core concepts of sanitation in a user-friendly format so that the book can serve as a practical reference to sanitation professionals and investment decision-makers, particularly the local governments. The annexe contains a practical collection of factsheets on selected sanitation system options.


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EPA (Editor) (1997): Wastewater Treatment Manuals – Primary, Secondary and Tertiary Treatment. Wexford: Environmental Protection Agency (EPA). URL [Accessed: 28.08.2014].

This manual on Primary, Secondary and Tertiary Treatment sets out the general principles and practices which should be followed by those involved in the treatment of urban waste water. It provides criteria and procedures for the proper management, maintenance, supervision, operation and use of the processes and equipment required for the secondary treatment of wastewater


Important Weblinks

http://www.youtube.com/ [Accessed: 01.05.2014]

This video with a virtual tour of a water resource recovery facility — commonly called a wastewater treatment plant — discusses how these facilities recycle the water and waste we flush down the drain. Water resource recovery facilities can also recover nutrients, generate energy, and create biosolids for use as fertilizer. This tour takes viewers through primary, secondary, and advanced treatment as well as the plant headworks and biosolids treatment process. It is developed by the Water Environment Federation and Gage 3D Studios (www.gage3d.com).

http://www.youtube.com/ [Accessed: 14.05.2014]

This video explains how to perform an activated sludge mixed liquor suspended solids settling test using a settlometer. This allows computing the settling abilities of the wastewater.

http://www.youtube.com/ [Accessed: 14.05.2014]

This video shows the wastewater (Primary Clarifier) math demonstration.

http://www.youtube.com/

This video explains basics of clarifiers, the designing and state point analysis.

http://www.borda-net.org [Accessed: 26.04.2010]

This is the homepage of the Bremen Overseas Research and Development Association (BORDA), which has contributed strongly to the development of decentralized wastewater treatment (i.e. DEWATS) the past decades.

http://www.unapcaem.org/act_detail.asp?id=311 [Accessed: 26.04.2010]

This webpage presents the proceedings of the International Seminar on Biogas Technology for Poverty Reduction and Sustainable Development, jointly sponsored by the United Nations Economic and Social Commission for Asia and the Pacific (UNESCAP) and the Ministry of Agriculture of China (MOA) (18 to 20 October, 2005, Beijing). Utilisation of household biogas systems and large-scale biogas systems as a means to boost rural economy, while contributing to rural poverty reduction and sustainable development are discussed.

http://www.snvworld.org/en/Pages/re-Publications.aspx [Accessed: 28.04.2010]

The Netherlands Development Organisation (SNV) library hosts an extensive choice of domestic biogas reports from around the world domestic biogas.

http://www.flickr.com/photos/gtzecosan/sets/72157623382874630/show/ [Accessed: 28.04.2010]

This Flickr slideshow shows different low-cost biogas plants from all over the world.

http://www.fao.org/docrep/T0541E/T0541E00.htm [Accessed: 26.04.2010]

This review is intended to up-date students, practitioners and consultants concerned with Biogas technologies, and to contribute to bringing biogas systems to a more advanced stage, and thereby to achieve a palpable impact in developing countries. Technical, social, environmental ad economic issues are addressed.