Anaerobic Baffled Reactor (ABR)

An anaerobic baffled reactor (ABR) is an improved Septic Tank with a series of baffles under which the wastewater is forced to flow. The increased contact time with the active biomass (sludge) results in improved treatment.

The upflow chambers provide enhanced removal and digestion of organic matter. BOD may be reduced by up to 90%, which is far superior to its removal in a conventional Septic Tank.

Design Considerations

The majority of settleable solids are removed in a sedimentation chamber in front of the actual ABR. Small-scale stand-alone units typically have an integrated settling compartment, but primary sedimentation can also take place in a separate Settler or another preceding technology (e.g., existing Septic Tanks). Designs without a settling compartment are of particular interest for (Semi-) Centralized Treatment plants that combine the ABR with other technologies, or where prefabricated, modular units are used. 

Typical inflows range from 2 to 200 m3 per day. Critical design parameters include a hydraulic retention time (HRT) between 48 to 72 hours, upflow velocity of the wastewater below 0.6 m/h and the number of upflow chambers (3 to 6). The connection between the chambers can be designed either with vertical pipes or baffles. Accessibility to all chambers (through access ports) is necessary for maintenance. Usually, the biogas produced in an ABR through anaerobic digestion is not collected because of its insufficient amount. The tank should be vented to allow for controlled release of odorous and potentially harmful gases.

Appropriateness

This technology is easily adaptable and can be applied at the household level, in small neighbourhoods or even in bigger catchment areas. It is most appropriate where a relatively constant amount of blackwater and greywater is generated. A (semi-) centralized ABR is appropriate when there is a pre-existing Conveyance technology, such as a Simplified Sewer.
This technology is suitable for areas where land may be limited since the tank is most commonly installed underground and requires a small area. However, a vacuum truck should be able to access the location because the sludge must be regularly removed (particularly from the settling compartment).
ABRs can be installed in every type of climate, although the efficiency is lower in colder climates. They are not efficient at removing nutrients and pathogens. The effluent usually requires further treatment.

Health Aspects/Acceptance 

Under normal operating conditions, users do not come in contact with the influent or effluent. Effluent, scum and sludge must be handled with care as they contain high levels of pathogenic organisms. The effluent contains odorous compounds that may have to be removed in a further polishing step. Care should be taken to design and locate the facility such that odours do not bother community members.

Operation & Maintenance

An ABR requires a start-up period of several months to reach full treatment capacity since the slow growing anaerobic biomass first needs to be established in the reactor. To reduce start-up time, the ABR can be inoculated with anaerobic bacteria, e.g., by adding fresh cow dung or septic tank sludge. The added stock of active bacteria can then multiply and adapt to the incoming wastewater. Because of the delicate ecology, care should be taken not to discharge harsh chemicals into the ABR.

Scum and sludge levels need to be monitored to ensure that the tank is functioning well. Process operation in general is not required, and maintenance is limited to the removal of accumulated sludge and scum every 1 to 3 years. This is best done using a Motorized Emptying and Transport technology. The desludging frequency depends on the chosen pre-treatment steps, as well as on the design of the ABR.

ABR tanks should be checked from time to time to ensure that they are watertight.

References

Further Readings

  • Cover image of a reference book or miscellany.

    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.

  • Cover image of a reference book or miscellany.

    BORDA (Editor) (2009): EmSan - Emergency Sanitation. An innovative & rapidly installable solution to improve hygiene and health in emergency situations. Bremen: Bremen Overseas Research and Development Association . URL [Accessed: 26.03.2010]. PDF

    This source presents the DEWATS emergency sanitation service package, including options for different types of prefabricated materials, developed by BORDA.

  • Cover image of a reference book or miscellany.

    FOXON, K.M.; BUCKLEY, C.A. (2006): Guidelines For The Implementation of Anaerobic Baffled Reactors for On-Site Or Decentralised Saniation. Durban: University of KwaZulu-Natal. URL [Accessed: 03.01.2011]. PDF

    This paper provides a framework within which a process engineer can design an anaerobic baffled reactor for the treatment of a specific domestic wastewater.

  • Cover image of a reference journal article.

    FOXON, K.M.; PILLAY, S.; LALBAHADUR, T.; RODDA, N.; HOLDER, F.; BUCKLEY, C.A. (2004): The anaerobic baffled reactor (ABR)- An appropriate technology for on-site sanitation. In: Water SA 30, 5. PDF

    The publication analyses the appropriateness of anaerobic baffled reactors (ABRs) for on-site primary sanitation in low-income communities. COD removal in domestic wastewater by a pilot ABR (3000L) was assessed. Results indicate that COD was sufficiently reduced for the reuse of the water in agriculture, but not for directly discharging it into natural surface or groundwater bodies.

  • Cover image of a reference book or miscellany.

    KOOTTATEP, T.; SRI-ANANT, W.; ANTOINE, M.; SCHERTENLEIB, R. (2004): Potential of the Anaerobic Baffled Reactor as decentralized Wastewater Treatment System in the Tropics. Klong Luang and Duebendorf: School of Environment, Resources and Development (SERD)/Asian Institute of Technology (AIT) and Water and Sanitation in Developing Countries (SANDEC) at the Swiss Federal Institute for Environmental Science (EAWAG). URL [Accessed: 03.01.2011]. PDF

    The anaerobic baffled reactor (ABR) could be a valuable alternative to conventional septic tanks. In this study, 3 lab-scale experimental ABR (2 baffles with and without anaerobic filter, respectively, and 3 baffles) were studied and compared to a conventional 2 chambers septic tank. The experimental units were fed with a mixture of septage and sewage in order to imitate the characteristics of toilet wastewater from households.

  • Cover image of a reference book or miscellany.

    LEMOS CHERNICHARO, C.A. de (2007): Anaerobic Reactors. London: International Water Association (IWA) Publishing. URL [Accessed: 01.11.2013]. PDF

    Anaerobic Reactors is the forth volume in the series Biological Wastewater Treatment. The fundamentals of anaerobic treatment are presented in detail, including its applicability, microbiology, biochemistry and main reactor configurations. Two reactor types are analysed in more detail, namely anaerobic filters and especially UASB (upflow anaerobic sludge blanket) reactors. Particular attention is also devoted to the post-treatment of the effluents from the anaerobic reactors. The book presents in a clear and informative way the main concepts, working principles, expected removal efficiencies, design criteria, design examples, construction aspects and operational guidelines for anaerobic reactors.

  • 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.

    MOREL, A.; DIENER, S. (2006): Greywater Management in Low and Middle-Income Countries, Review of Different Treatment Systems for Households or Neighbourhoods. Duebendorf: Swiss Federal Institute of Aquatic Science (EAWAG), Department of Water and Sanitation in Developing Countries (SANDEC). URL [Accessed: 19.05.2010]. PDF

    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).

  • Cover image of a reference book or miscellany.

    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.

  • Cover image of a reference book or miscellany.

    SPERLING, M. von; LEMOS CHERNICHARO, C.A. de (2005): Biological Wastewater Treatment in Warm Climate Regions Volume 1. London: International Water Association (IWA) Publishing. URL [Accessed: 01.11.2013]. PDF

    Biological Wastewater Treatment in Warm Climate Regions gives a state-of-the-art presentation of the science and technology of biological wastewater treatment, particularly domestic sewage. The book covers the main treatment processes used worldwide with wastewater treatment in warm climate regions given a particular emphasis where simple, affordable and sustainable solutions are required. The 55 chapters are divided into 7 parts over two volumes: Volume One: (1) Introduction to wastewater characteristics, treatment and disposal; (2) Basic principles of wastewater treatment; (3) Stabilisation ponds; (4) Anaerobic reactors; Volume Two (also available in the SSWM library): (5) Activated sludge; (6) Aerobic biofilm reactors; (7) Sludge treatment and disposal.

Case Studies

  • Cover image of a reference book or miscellany.

    BORDA (Editor) (2007): Community Based Sanitation — SANIMAS. Islamic Centre An Nawawi, Purworejo, Central. DEWATS Indonesia and Bremen Overseas Research and Development Association (BORDA). PDF

    Case study of the construction a DEWATS system for 190 of students and teachers comprising a sedimentation step, an anaerobic baffle reactor (ABR) and an expansion chamber, which consisting of 7 compartments. The effluent is discharged into river/waterbody.

  • Cover image of a reference book or miscellany.

    BORDA (Editor) (2008): Decentralized Wastewater Treatment System - DEWATS. Animal Products Development Centre, Bureau of Animal Industry (APDC-BAI). Bremen: Bremen Overseas Research and Development Association (BORDA). PDF

    The Animal Products Development Centre, Bureau of Animal Industry (APDC-BAI) together with Bremen Overseas Research and Development Association (BORDA) developed together 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.

  • Cover image of a reference book or miscellany.

    BORDA (Editor) (2008): Decentralized Wastewater Treatment System - DEWATS. Manjuyod Public Market. Bremen: Bremen Overseas Research and Development Association (BORDA) . URL [Accessed: 26.03.2010]. PDF

    The wastewater from Manjuyod’s public market is treated in a decentralized system (DEWATS) composed of four different components: a settling tank; a anaerobic baffled reactor which reduces the BOD/COD content from 20% to 85%; a planted gravel filter; and finally a polishing pond.

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

    MOREL A.; DIENER S. (2006): Ecosan Greywater Demonstration Project. Case study from Kuching, Malaysia. In: MOREL, A.; DIENER, S. (2006): Greywater Management in Low and Middle-Income Countries, Review of Different Treatment Systems for Households or Neighbourhoods. Duebendorf, 76.

    The city of Kuching is currently lacking a wastewater treatment plant, and the local subsurface conditions make a conventional centralised wastewater system expensive to implement. Most buildings are equipped with two separate wastewater outlets, one outlet for blackwater and one for greywater. The proposed system treats greywater from nine households, and consists of a baffled septic tank, followed by a dosing chamber from where the greywater flows into four vertical down-flow, single-pass aerobic biofilters before reaching a subsurface horizontal-flow planted filter. Finally, the treated greywater is discharged into a stormwater drain.

  • Cover image of a reference book or miscellany.

    NASR, F.A.; DOMA, H.S.; NASSAR, H.F. (2008): Treatment of domestic wastewater using an anaerobic baffled reactor followed by a duckweed pond for agricultural purposes . pdf presentation. Egypt: Water Pollution Control Department. URL [Accessed: 26.03.2010]. PDF

    In this study, an anaerobic baffled reactor (ABR) was fed continuously with domestic wastewater at four HRTs ranging from 8 to 24 h and corresponds to organic loading rates ranging from 0.67 to 2.1 kg COD/m3/day. The ABR effluent was fed to a DWP operating at 10 and 15 days. The performance of the ABR at the four HRTs gave satisfactory results.

  • SINGH, S.; HABERLA, R.; MOOG, O.; SHRESTA, R.R.; SHRESTA, P.; SHRESTA, R. (2009): Performance of an Anaerobic Baffled Reactor and Hybrid Constructed Wetland treating high-strength Wastewater in Nepal- A model for DEWATS . In: Ecological Engineering 35, 654.

  • Cover image of a reference book or miscellany.

    SUSANA (Editor) (2010): Decentralized Wastewater Management at Adarsh College Badalapur, Maharashtra, India. Factsheet. Eschborn: Sustainable Sanitation Alliance (SuSanA). URL [Accessed: 12.01.2011]. PDF

Training Material

  • Cover image of a reference book or miscellany.

    EAWAG/SANDEC (Editor) (2008): Sanitation Systems and Technologies. Lecture Notes . Duebendorf: Swiss Federal Institute of Aquatic Science (EAWAG), Department of Water and Sanitation in Developing Countries (SANDEC). PDF

    Lecture notes on technical and non-technical aspects of sanitation systems in developing countries.

  • Cover image of a reference book or miscellany.

    EAWAG/SANDEC (Editor) (2008): Sanitation Systems and Technologies. Exercise: Anaerobic Baffled Reactor (ABR). Duebendorf: Swiss Federal Institute of Aquatic Science (EAWAG), Department of Water and Sanitation in Developing Countries (SANDEC). PDF

    Exercise on the dimensioning of am anaerobic baffled reactor.

  • Cover image of a reference book or miscellany.

    EAWAG/SANDEC (Editor) (2008): Sanitation Systems and Technologies. Exercise: Anaerobic Baffled Reactor (ABR). Duebendorf: Swiss Federal Institute of Aquatic Science (EAWAG), Department of Water and Sanitation in Developing Countries (SANDEC). PDF

    Exercise on the dimensioning of am anaerobic baffled reactor.

  • Cover image of a reference book or miscellany.

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

    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).

Important Weblinks

  • http://watsanexp.ning.com [Accessed: 21.08.2014]

    This site is dedicated to individuals, groups, or institutions interested in improving the quality of life and health of their communities through wastewater treatment. The tools and information contained here are provided to help with planning, building and operating low cost wastewater systems.

  • http://youtu.be/n9EzBNuR0cM [Accessed: 21.08.2014]

    This film is on sanitation post tsunami. It's a case study about East Devdhanam in Trichy (Tamil Nadu), where Community Based Sanitation-DEWATS has been quite successful.

  • http://youtu.be/Ow2scqvsoLo [Accessed: 21.08.2014]

    The video shows DEWATS-engineers and community facilitators during a whole process of implementation of a DEWATS approach at Khoualuang Primary School in Vientiane Capital, Lao P.D.R.

  • http://youtu.be/zTqE-8j9Unw [Accessed: 21.08.2014]

    This video shows how the Decentralised Wastewater Treatment System (DEWATS) works in Aravind Eye Hospital in Tamil Nadu.

  • http://www.gpa.unep.org [Accessed: 23.02.2010]

    The Train-Sea-Coast GPA is an active inter-agency collaboration between the UNESCO-IHE Institute for Water Education, the EU ACP Water Facility, the UN DOALOS, UNDP, GEF and UNEP/GPA. It aims to train experts and local, regional and international instructors in coastal populations. The compendium of technologies offers a description of several technologies for wastewater treatment suitable for typical physical conditions in Small Islands Developing States (SIDS) and low income coastal countries.