25 April 2023

Anaerobic Filter

Author/Compiled by
Rohit Bhagwat (Ecosan Services Foundation (ESF))

Executive Summary

An Anaerobic Filter (AF) is a fixed-bed biological reactor used for treating wastewater having non-settable and dissolved solids. As wastewater flows through the filter, particles are trapped and organic matter is degraded by the biomass that is attached to the filter material. There are two main types of AF viz. up-flow and down-flow filters. AFs are considered as one of the most useful system at high organic loading rates for treatment of low and high strength wastewaters (TAY & SHOW 1998). AFs are widely used as secondary treatment in DEWATS.

Source: McCarty 1964; Bodik 1999; Sanimas 2005
A high degree of waste stabilisation.
Low production of by-products i.e. waste biological sludge.
Low nutrient requirements.
No oxygen requirements.
Useful end product i.e. Methane.
Source: McCarty 1964; Bodik 1999; Sanimas 2005
Relatively high temperatures required for optimum operation.
Dilute wastes may not produce sufficient methane.
Clogging of matrix.
Master mason required for high-quality plastering work.

The contents of this factsheet are results of the Indo-European Project NaWaTech- “Natural Water Systems and Treatment Technologies to cope with Water Shortages in Urbanised Areas in India”, co-financed by the EC and the DST – India.

Design and Construction Principle

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F7 Anaerobic Filters
Anaerobic Filter


AF may consist of cylindrical or rectangular tanks having an enclosed fixed or floating media within the reactor. AF operates as a flow-through contact process and most of the times it is operated in up-flow mode (YOUNG and YANG 1989). Whilst designing the AFs, parameters including characteristics of wastewater, volumetric organic loading, flow velocity, physical features, gas collection and the solid separation need to be addressed. The design should also consider Solid Retention Time (SRT), Hydraulic Retention Time (HRT), allowable head-loss, and backwash requirements (if any) along with the media to be used in the system (TCHOBANOGLOUS et al. 2003). “Typical filter material size ranges from 12 to 55 mm in diameter. Ideally, the material will provide between 90 to 300 m2 of surface area per 1 m3 of reactor volume. The water level should cover the filter media by at least 0.3 m to guarantee an even flow regime. A HRT of 0.5 to 1.5 days is typical and recommended. A maximum surface-loading (i.e. flow per area) rate of 2.8 m/d has proven to be suitable” (TILLEY et al. 2008). At lower temperatures, bacterial activity decreases and it results in lower treatment performance. Hence in cold climate countries, only a small separated portion of the sewage, namely the primary and secondary sludge are treated anaerobically, however requiring heavy insulation and heating system, while the bulk of the volume, the wastewater, is treated aerobically (VAN HAANDEL and LETTINGA 1994).

Operation and Maintenance

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Process parameters need to be monitored closely viz. temperature, pH, effluent concentration, gas production (TCHOBANOGLOUS et al. 2003). AFs are less energy intensive. The seeding is required in order to grow the anaerobic bio culture on the filter media. In case of fixed film filter, the hydraulic load must correspond to the upstream velocity and must correspond to the organic load. Desludging is periodical. Backwash is required in case of clogging of the filter media. Appropriate management of flammable gases like methane is necessary either by collection, venting or burning in the air. O & M of anaerobic filters require skilled staff.

Cost Considerations

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Construction costs are low in case filter materials are locally available. Neither moving parts nor technical energy needed for operation of AF. Manual or vacuum desludging required annually and back-washing of filter materials may be required every five to ten years (SANIMAS 2005).

Experiences in Europe and other Cities of the World

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The first models of fixed film AF were designed during 1968 whilst the down-flow anaerobic filters were scaled fully in 1983 (IRWIN n.y.). Since then these systems are being used in the world. The AF is being used for beverage, food-processing, pharmaceutical and chemical industries due to its high capability of bio-solids retention (ERSAHIN et al. n.y.). Anaerobic Filters are being used in countries including Brazil, Colombia, Mexico (CAKIR 2004) and they are rarely employed in U.S. onsite applications (COREA 1998). BODIK et al. (2000) undertook a research for finding economically and technologically suitable technology for treating municipal wastewater. Based on the experiments and observations, it was found that the use of Upflow Anaerobic Filter reactor is potential technology for treating of wastewater produced by small communities in comparison with UASB. He further states that this technology is relatively cheap and could be a technological solution for the post-communist countries (Central & Eastern European countries), where there is a high demand for a larger number of smaller WWTPs.

Experiences in India

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Anaerobic Filters are widely used in hot climates, where domestic wastewaters have high organic content (COREA et al. 1998). A pilot study was carried out for a community of 300 people near city of Auroville in Tamil Nadu, where the AF has been used in combination of Reed Bed Technology to treat domestic wastewater from the community (CPCB 2008).

BANU et al. (2007) studied a hybrid system of Anaerobic Filter and Upflow Anaerobic Sludge Blanket (UASB) to treat domestic wastewater. They termed this hybrid system as Hybrid Upflow Anaerobic Sludge Blanket (HUASB). The team collected the domestic wastewater from Nessapakkam Sewage Treatment Plant, Chennai, India. This sewage was treated with HUSAB and they found that COD removal varies from 75-86% and the BOD removal efficiency was in the range of 70-91%. They concluded their study by stating that “HUSAB appears to be a promising alternative for the treatment of domestic wastewater in developing countries like India”. Ecosan Services Foundation (ESF) and seecon gmbh in 2008, constructed a Decentralised Wastewater Treatment System (DEWATS) at Adarsh College, Badlapur, India; where AF was used in combination with Anaerobic Baffle Reactor (ABR) as a secondary treatment system. This DEWATS caters 8 m3/day of wastewater generated by the college students (ZIMMERMANN et al. 2009). In 2010, two DEWATS systems involving AFs were installed and made operational for boy’s hotels block and admin office at Tata Dhan Academy at Madurai. Both the systems cater wastewater generated by 300 people (GOETZENBERGER 2010). CDD - BORDA has implemented 3 DEWATS systems in the City of Nagpur, India catering population of 4,420 which generates over 344 m3 of wastewater. Anaerobic Filters are the crucial part of secondary treatment in these DEWAT systems (BHANDARKAR 2013).


For more information please visit: Anaerobic Filter


The research leading to these results has received funding from the European Union Seventh Framework Programme ([FP7/2007-2013]) under Grant Agreement N° [308336] and the Department of Science and Technology of the Government of India  DS.O DST/IMRCD/NaWaTech/ 2012/(G).
Library References

Treatment of Domestic Wastewater Using Upflow Anaerobic Sludge Blanket Reactor

This paper presents the findings of the study on treatment of domestic wastewater using a laboratory scale Hybrid Upflow Anaerobic Sludge Blanket (HUASB) reactor.

BANU, J.R. ; KALIAPPAN, S. ; YEOM, I.T. (2007): Treatment of Domestic Wastewater Using Upflow Anaerobic Sludge Blanket Reactor. In: Journal of Environmental Science and Technology: Volume 4 , 363-370. URL [Accessed: 20.03.2015]

Dissemination of DEWATS in Large and Medium Towns in Maharashtra State

CDD Regional Cooperation Office Nagpur and the CDD network Partner have been lobbying at Maharashtra Government level to incorporate decentralize wastewater treatment systems (DEWATS) into government policy for treatment of wastewater in urban and peri-urban areas

BHANDARKAR, S. (2013): Dissemination of DEWATS in Large and Medium Towns in Maharashtra State. Bremen Overseas Research and Development Association (BORDA) South Asia URL [Accessed: 19.05.2013]

Anaerobic Treatment of the Municipal Wastewater Under Psychrophilic Conditions

The article discusses possibilities of municipal wastewater treatment in various types of anaerobic reactors (UASB, UAF, AnSBR). The temperature during corresponding laboratory experiments varied between 9–23 °C. Real wastewater from WWTP Bratislava-Petržalka and synthetic substrate were used in the experiments. The HRT values for reactors were found to be 10–46 h. Treatment of municipal wastewater with the AnSBR and UAF system has shown more positive results in laboratory scale studies then the UASB system. The mean removal efficiency of COD depended on the type of anaerobic reactor, temperature, used HRT and was found between 37–48% (UASB), 56–88% (AnSBR) and 46–90% (UAF).

BODIK, I. ; HERDOVA, B. ; DRTIL, A.M. (2000): Anaerobic Treatment of the Municipal Wastewater Under Psychrophilic Conditions. In: Bioprocess Engineering: Volume 22 , 385-390. URL [Accessed: 20.03.2015]

Anaerobic Treatment of Low Strength Wastewater

Anaerobic wastewater treatment is becoming an accepted technology for treating various types of wastewater. It is frequently used for medium to high strength wastewater (2,000 to 20,000 mgIL COD), but has had fewer applications to low strength wastewater 1,000 mgIL COD) especially in developed countries. In order to understand the applicability of anaerobic treatment for low strength wastewater, such as domestic wastewater, a literature review was performed. The review showed two main variations of anaerobic wastewater treatment techniques (anaerobic filter and upflow anaerobic sludge blanket reactor) and a number of modifications of these two themes in 34 different countries with influent COD ranging from 58 mgIL to 62,000 mgIL.

CAKIR, F.Y. (2004): Anaerobic Treatment of Low Strength Wastewater. Dissertation. Los Angeles: University of California URL [Accessed: 20.03.2015]

Anaerobic Filters for On-Site Sewage Treatment

Septic tank soakage pit systems have been the common- est form of sewage disposal in urban and suburban Sri Lanka, where only parts of the Capital, Colombo, is served by a central sewer network. Virtually none of the other major cities and towns have any form of central sewer network. Even in Colombo, the coverage remains poor, with an estimated 1.7 million people (approximately 80 per cent of the metropolitan population of Greater Colombo) being dependent on on-site systems for sewage disposal (Fernando, 1994)

COREA, E.J.H. GAMAGE, I.R. WICKRAMANAYAKE, P.N. (1998): Anaerobic Filters for On-Site Sewage Treatment. (= Sanitation and Water for All: Proceedings of the 24th WEDC Conference Islamabad, Pakistan ). Leicestershire: Water, Engineering and Development Centre (WEDC) URL [Accessed: 20.03.2015]

A Study of Pilot Project on Decentralised Treatment & Recycling of Domestic Wastewater

Document on the decentralised treatment & recycling of domestic wastewater in Auroville Universal Township Tamil Nadu, India.

CPCB (2008): A Study of Pilot Project on Decentralised Treatment & Recycling of Domestic Wastewater. An Integrated Approach to Water Management at Sangamam Community - A Village Model in Out-Skirts of Auroville Universal Township Tamil Nadu. New Delhi: Central Pollution Control Board (CPCB) URL [Accessed: 09.04.2013]

Anaerobic Treatment of Industrial Effluents: An Overview of Applications

This chapter intends to bring together the knowledge obtained from different applications of the anaerobic technology for treatment of various types of industrial wastewaters. The first part of the chapter covers brief essential information on the fundamentals of anaerobic technology. The remainder of this chapter focuses on various anaerobic reactor configurations and operating conditions used for the treatment applications of different industrial wastewaters. Examples of applications that reflect the state-of-the-art in the treatment of industrial effluents by high rate anaerobic reactors are also provided.

ERSAHIN, M.E. OZGUN, H. DERELI, R.K. OZTURK, I. (2011): Anaerobic Treatment of Industrial Effluents: An Overview of Applications. In: GARCIA, F.S. (2011): Waste Water - Treatment and Reutilization. Rijeka: 3-28. URL [Accessed: 09.04.2013]

Commencement of Operation of Two DEWATS at Tata-Dhan Academy, Madurai

Tata-Dhan Academy (TDA) is a development school in India with a mission of creating development professionals to work with the poorest sections of the society. Graduates of the Academy work with organizations that, in turn, work directly with the community. TDA offers Post-Graduation courses in Development Management for those interested in becoming development professionals.

GOETZENBERGER, J. (2010): Commencement of Operation of Two DEWATS at Tata-Dhan Academy, Madurai. Bremen Overseas Research and Development Association (BORDA) South Asia URL [Accessed: 19.05.2013]

A Primer on Anaerobic Filters

Anaerobic fixed-film reactors were developed in 1968 and have grown to represent an advanced technology that has been used effectively for treating a variety of industrial wastes. A number of variations have been developed in the intervening years including the fully packed upflow anaerobic filter (AF) , the fully packed downflow anaerobic filter and the upflow hybrid anaerobic filter (HAF).

IRWIN, T. (n.y): A Primer on Anaerobic Filters. Fundamentals and Applications. n/a: Engineering Fundamentals URL [Accessed: 08.04.2013]

Informed Choice Catalogue

This informed choice catalogue for community based wastewater treatment technologies helps to identify suitable sanitation options and facilitates the assessment of different sanitation system components with regard to stakeholder preferences. A powerful tool for technical bottom-up planning giving overall information about technical options at a "glance".

SANIMAS (2005): Informed Choice Catalogue. pdf presentation. BORDA and USAID URL [Accessed: 29.05.2019]

Media-Induced Hydraulic Behavior and Performance of Upflow Biofilters

Laboratory studies were conducted to assess the influence of media-related factors such as porosity, specific surface, and pore size on hydraulic behavior and performance of upflow anaerobic biofilters (ABFs).

TAY, J. ; SHOW, K. (1998): Media-Induced Hydraulic Behavior and Performance of Upflow Biofilters. In: Journal of Environmental Engineering: Volume 124 , 720-729. URL [Accessed: 20.03.2015]

Compendium of Sanitation Systems and Technologies

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

TILLEY, E., LUETHI, C., MOREL, A., ZURBRUEGG, C. and SCHERTENLEIB, R. (2008): Compendium of Sanitation Systems and Technologies. Duebendorf, Switzerland: Swiss Federal Institute of Aquatic Science and Technology (EAWAG) and Water Supply and Sanitation Collaborative Council (WSSCC) URL [Accessed: 15.02.2010] PDF

Decentralised Wastewater Management at Adarsh College Badlapur, Maharashtra, India

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 biogas settler, an anaerobic baffled reactor, and anaerobic filter, a horizontal flow wetland and a polishing pond.

ZIMMERMANN, N. WAFLER, M. THAKUR, P. (2009): Decentralised Wastewater Management at Adarsh College Badlapur, Maharashtra, India. (= SuSanA - Case Studies ). Eschborn: Sustainable Sanitation Alliance (SuSanA) URL [Accessed: 22.09.2010]
Further Readings

The Application of Anaerobic Filter for Municipal Wastewater Treatment

This paper presents results of the lab-scale anaerobic filter and pilot-scale units of anaerobic baffled filter used for municipal wastewater treatment by low temperature.

BODIK, I. ; HERDOVA, B. ; KRATOCHVIL, K. (1999): The Application of Anaerobic Filter for Municipal Wastewater Treatment. In: Chemical Papers: Volume 54 , 159-164. URL [Accessed: 20.03.2015]

Development of an Improved Anaerobic Filter for Municipal Wastewater Treatment

Development of an improved reactor configuration of anaerobic filter was carried out for the elimination of clogging of filter media. The experiments over different hydraulic retention times (HRTs) indicated that the HRT of 12 h was the most appropriate one for the system studied while treating the municipal wastewater, which resulted 90% and 95% BOD and COD reduction, respectively. Reduction up to 95% in suspended solids concentration could be achieved without any pretreatment. The specific biogas yield obtained was 0.35 m3 CH4/kgCODr with 70% of CH4 content in the biogas generated from the system at the HRT of 12 h. Operational problems such as clogging of filter media were not observed throughout the period of study over 600 d.

BODKHE, S. (2008): Development of an Improved Anaerobic Filter for Municipal Wastewater Treatment. In: Bioresource Technology: Volume 99 , 222-226. URL [Accessed: 20.03.2015]

Feasibility Study of Upflow Anaerobic Filter for Pre-Treatment of Municipal Wastewater

Anaerobic reactors have been successfully installed in full-scale plants world-wide for treating high-strength industrial wastewater over the years. Recently, there has been significant interest in exploring this technology for treating low-strength domestic wastewater as well. Previously, it was thought that this was not practical as methane fermentative process was considered too slow to be able to treat the increasing volume of domestic sewage at a high rate. With technological advances and better understanding of anaerobic microbial characteristics in recent years, there is a potential that under control conditions, such barriers can be gradually overcome. The perspectives of using anaerobic pre-treatment for domestic sewage are discussed in this report to replace the conventional treatment methods. Feasibility of upflow anaerobic filter (UAF) in place of activated sludge process to pre-treat domestic wastewater is studied in this research.

KAVITHA K. (2009): Feasibility Study of Upflow Anaerobic Filter for Pre-Treatment of Municipal Wastewater. Master's Thesis. Singapore: Departement of Civil Engineering, National University Singapore URL [Accessed: 20.03.2015]

Treatment of Low Strength Domestic Wastewater Using the Anaerobic Filter

A laboratory scale anaerobic filter packed with synthetic high surface area trickling filter media was used to treat a low strength domestic wastewater averaging 288 mg 1−1 COD. The filter was operated for 60 days after reaching steady-state at 20, 25, 35°C at a loading rate of 0.02 lb COD ft−3 day−1 and 24 h hydraulic retention time. Filter effluent BOD5 averaged 38 mg 1−1 providing an average removal rate of 79%, and effluent COD averaged 78 mg 1−1, corresponding to a 73% removal rate. Removal efficiencies showed very little sensitivity to daily fluctuations in influent wastewater quality. The filter performance at 25 and 35°C was not significantly different, but BOD and TSS removal efficiency declined a: 20°C. Gas production averaged 0.027 ft−3 of gas per ft3 of influent wastewater, or 1.875 ft3 of gas per pound of influent COD. Gas composition averaged 30% nitrogen, 65% methane, and 5% carbon dioxide. Ammonia nitrogen and sulfides both increased during treatment. It is concluded that the anaerobic filter is a promising candidate for treatment of low strength wastewaters and that post treatment for sulfides and ammonia may be necessary.

KOBAYASHI, H.A. ; STENSTROM, M.K. ; MAH, R.A. (1983): Treatment of Low Strength Domestic Wastewater Using the Anaerobic Filter. In: Water Research: Volume 17 , 903-909. URL [Accessed: 20.03.2015]

Anaerobic Waste Treatment Fundamentals

This paper deals with the process of waste treatment that has not been too well understood and consequently has not been as widely used as it might deserve. Part One discusses the advantages and disadvantages of anaerobic waste treatment, conventional practices and the present concepts of the microbiology and chemistry involved. Parts Two and Three will cover the environmental requirements for achieving control of the anaerobic process and preventing or correcting toxicity in the system. Part Four will outline the application of these various concepts in treatment plant design.

MCCARTY, P.L. (1964): Anaerobic Waste Treatment Fundamentals. In: Public Works: Volume 95 URL [Accessed: 20.03.2015]

The Anaerobic Filter for Waste Treatment

An entirely new anaerobic treatment process has been found to be particularly effective for the treatment of low strength soluble organic wastes.

YOUNG, J.C. ; MCCARTY, P.L. (1969): The Anaerobic Filter for Waste Treatment. In: Journal (Water Pollution Control Federation), Research Supplement to:: Volume 41 , 160-173. URL [Accessed: 20.03.2015]

Compendium of Natural Water Systems and Treatment Technologies to cope with Water Shortages in Urbanised Areas in India

The Compendium of NaWaTech Technologies presents appropriate water and wastewater technologies that could enable the sustainable water management in Indian cities. It is intended as a reference for water professionals in charge of planning, designing and implementing sustainable water systems in the Indian urban scenario, based on a decentralised approach.

BARRETO DILLON, L. ; DOYLE, L. ; LANGERGRABER, G. ; SATISH, S. ; POPHALI, G. (2013): Compendium of Natural Water Systems and Treatment Technologies to cope with Water Shortages in Urbanised Areas in India. Berlin: EPUBLI GMBH URL [Accessed: 11.12.2015]

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