Anaerobic Baffled Reactor 1 Martin Wafler, seecon international gmbh

Anaerobic Baffled Reactor


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Martin Wafler, seecon international gmbh


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Contents

1. Concept

2. How it can optimize SSWM

3. Design principals

4. Treatment efficiency

5. Operation and maintenance

6. Applicability

7. Advantages and disadvantages

8. References

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Background and working principal (adapted from U.S. EPA 2006, SASSE 1998)

1. Concept

Cut-away view and longitudinal section of an ABRSource: SANIMAS (2005), MOREL & DIENER (2006)

• physical and biological (anaerobic) treatment of wastewater

• integrated sedimentation chamber for pre-treatment of wastewater

• alternating standing and hanging baffles

• wastewater passes through the sludge to move to the next compartment

• solid retention time (SRT) separated from hydraulic retention time (HRT)

• high treatment rates due to enhanced contact of incoming wastewater with residual sludge and high solid retention

• low sludge production



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Construction of different toilet blocks connected to twopre-fabricated fibreglass reactors comprising a settling chamber, an aerobic baffled reactor and a final anaerobic filter unit

Source: BORDA 2009

Examples

1. Concept



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Biogas settler as settlement compartment (near completion) at Pestalozzi School, ZambiaSource: http://www.germantoilet.org/

Examples

1. Concept



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The ABR under construction, down pipes and perforated slabs to support filter media in the Anaerobic Filter (AF) sections, pouring ABR’s concrete slab at Pestalozzi School, Zambia

Source: http://www.germantoilet.org/

Examples

1. Concept



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ABR (part of DEWATS) at Adarsh Vidyaprasarak Sanstha’s College of Arts & Commerce, IndiaSource: N. Zimmermann

Examples

1. Concept



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ABR (part of DEWATS) at Sunga Wastewater Treatment Plant, Kathmandu, NepalSource: N. Zimmermann

Examples

1. Concept



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2. How it can optimize SSWM

• treatment of all wastewater (grey-, black- and/or industrial wastewater) that it is fit (after secondary treatment) for reuse and/or safe disposal

• allows for recovery of biogas, which can be used as a substitute to e.g. LPG or fuel wood in cooking



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3. Design principals

ABRs start with settling chamber for larger solids and impurities

(SASSE 1998) followed by series of at least 2 (MOREL & DIENER 2006), sometimes up to 5 (SASSE 1998) up-flow chambers

Hydraulic Retention Time (HRT) is relatively short and varies from only a few hours up to two or three days (FOXON et al. 2004; MOREL & DIENER 2006;

TILLEY et al. 2008)

up-flow velocity is the most crucial parameter for dimensioning, especially with high hydraulic loading. It should not exceed 2.0 m/h (SASSE 1998; MOREL & DIENER 2006).

organic load <3 kg COD/m3/day. Higher loading-rates are possible with higher temperature and for easily degradable substrates (SASSE 1998)



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4. Treatment efficiency

Treatment performance of ABRs is in the range of (SASSE 1998; MOREL & DIENER

2006; BORDA 2008)

•Chemical Oxygen Demand (COD) removal: 65% to 90%,•Biological Oxygen Demand (BOD) removal: 70% to 95%,•Total Suspended Solids (TSS) removal: up to 90% (SINGH 2008)

•Pathogen reduction: low

Superior to BOD-removal (30% to 50%) of conventional septic tank (UNEP 2004).



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• inoculate („seed“) ABR with active anaerobic sludge from e.g. septic tank to speed up start-phase

• allow bacteria to multiply, by starting with 1/4 of daily flow, and then increasing loading rates over 3 months

• long start-up time do not use ABRs when need for treatment is immediate

• check for water-tightness regularly and monitor scum and sludge levels

• remove sludge every 1 to 3 years (preferably by vacuum truck or gulper to avoid that humans get in direct contact with sludge)

• leave some active sludge in each compartment to maintain stable treatment process

• take care of advanced treatment and/or safe disposal of sludge Source: adapted from SASSE 1998, TILLEY et al. 2008, EAWAG/SANDEC 2008



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Use of “straight handle” (left) and “Z-handle” (right) brushes for cleaning of down-ward pipesSource: K.P. Pravinjith


Examples



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Measuring sludge levelsSource: K.P. Pravinjith


Examples



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6. Applicability

• be installed in every type of climate, although efficiency is affected in colder climates (TILLEY et al. 2008)

• suited for household level or for small neighbourhood as DEWATS (Decentralized Wastewater Treatment System)

(EAWAG/SANDEC 2008)

• suited for industrial wastewaters• be designed for daily inflows in a range of some m3/day up to

several hundreds of m3/day (FOXON et al. 2004; TILLEY et al. 2008)

• in general, installed underground and therefore appropriate for areas where land is limited

• been pre-fabricated from e.g. fibreglass and used as final step for emergency sanitations (BORDA 2009)



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Disadvantages:

•needs expert design

•long start-up phase

•needs strategy for faecal sludge management

•effluent requires secondary treatment and/or appropriate discharge

•clear design guidelines are not available yet

•low reduction of pathogens

Advantages:

•extremely stable to hydraulic shock loads

•high treatment performance

•simple to construct and operate

•no electrical requirements

•low capital and operating costs, depending on economy of scale

•low sludge generation

•biogas can be recovered

7. Advantages and disadvantages



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8. References

BORDA (2009): EmSan - Emergency Sanitation. An innovative & rapidly installable solution to improve hygiene and health in emergency situations (Concept Note). Bremen: Bremen Overseas Research and Development Association (BORDA)

EAWAG/SANDEC (2008): Sanitation Systems and Technologies. Lecture Notes. (=Sandec Training Tool 1.0, Module 4). Duebendorf: Swiss Federal Institute of Aquatic Science (EAWAG), Department of Water and Sanitation in Developing Countries (SANDEC)

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 Vol. 30 No. 5 (Special edition)

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 and Technology (Eawag).

SANIMAS (2005): Informed Choice Catalogue. PPT-Presentation. BORDA and USAID

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



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8. References

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. 654-660

TILLEY, E., LUETHI, C., MOREL, A., ZURBRUEGG, C., SCHERTENLEIB, R. (2008): Compendium of Sanitation Systems and Technologies. Duebendorf and Geneva: Swiss Federal Institute of Aquatic Science (EAWAG) & Water Supply and Sanitation Collaborative Council (WSSCC)

U.S. EPA (2006): Emerging Technologies for Biosolids Management. (=EPA 832-R-06-005). United States Environmental Protection Agency, Office of Wastewater Management

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Anaerobic Baffled Reactor 1 Martin Wafler, seecon international gmbh