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Night soil/sludge treatment: update 7
Information Dissemination
Ghana Project Workshop
A two-day national workshop on faecal sludge treatment was held in Ghana from Dec. 4-5, 1997. It marked the termination of four years of collaborative field research between the Water Research Institute (WRI) of Ghana and EAWAG/SANDEC. The workshop attracted some 30 participants comprising government officials, consultants, entrepreneurs and representatives of support agencies, including invited specialists from Tanzania, Benin and Mali. The Workshop coincided with the initial stage of the 4th phase of the Urban Environmental Sanitation Project co-funded by World Bank/IDA which comprises the five major cities of Ghana. Faecal sludge treatment plants shall be designed and implemented in all five cities as part of the overall project. The Workshop served to publicise the results of the four years of field research, the recommendations originating from them and the gaps-in-knowledge still remaining and to be addressed through further field and action research. The Workshop served as a lively platform for the discussion of acute FS management problems in Ghana and in other countries.
The Workshop lead to the following set of issues/researchable questions warranting further applied field and action research:
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reducing toxicity to algae caused by high levels of ammonia in faecal sludge liquor (suggested measures to be tested: surface aeration; ammonia stripping over cascades; effluent recirculation; lime dosing);
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assessing the suitability of deep anaerobic ponds and of anaerobic digestion in treating FS, particularly high-strength, undigested sludges from unsewered public toilets and bucket latrines;
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assessing the current practice of traditional use of untreated FS in agriculture and its possible integration into improved FS management schemes;
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Helminth egg monitoring in existing FS treatment schemes to asses the degree of FS hygienisation achieved; and
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SANDEC will produce a workshop report which will be available free-of-charge from EAWAG/SANDEC.
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Publication of Documents on FS Treatment
WRI and SANDEC have jointly published the following discussion paper:
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Heinss, U., Larmie S., Strauss, M. (1998). Solids Separation and Pond Systems for the Treatment of Faecal Sludges in Tropical Climates - Lessons Learnt and Recommendations for Preliminary Design. SANDEC Report no. 05/98, EAWAG.
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The report is available upon request and free-of-charge from EAWAG/SANDEC or from WRI, Mr. S.A. Larmie, P.O. Box M 32, Accra, Ghana (Tel +233-21-77 95 15; fax +233-21-77 71 70).
Other forthcoming discussion papers are:
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Heinss, U., Strauss, M. (1998). Co-Treatment of Faecal Sludge and Wastewater - A Literature review. EAWAG/SANDEC; and
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Heinss, U., Larmie, S.A., Strauss, M. (1998). Solids-Liquid Separation of Faecal Sludges. I: Settling/Thickening Tank Performance and Design - Results of a Monitoring Campaign Conducted in Accra, Ghana. II: Use of Reed Beds for Sludge Dewatering - A Literature Review. EAWAG/SANDEC and WRI.
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Overview of SANDEC's Completed, Current and Planned R+D Activities in FS Treatment
Table 1 is a summary of SANDEC's completed, ongoing and planned/committed collaborative field research projects on FS treatment.
SANDEC's Collaborative Field Research on Faecal Sludge Treatment (as of January 1998)
Completed investigation
Accra (Ghana), Water Research Institute
(WRI) - Settling/thickening + anaerobic ponds (full-scale) + drying beds; 1993-97.
Manila (Philippines), National Engineering Centre, University of The Philippines - Use of septage for the recultivation of damaged soils (yard-scale studies); 1996-97>
Ongoing and planned investigations
Bangkok (Thailand), Asian Institute of Technology (AIT) - Planted sludge drying beds for FS humification, Anaerobic and attached- growth WSP; 1996-99; 1997-99.
Rosario(Argentina),University of Rosario, Dept. Hydraulic & Sanitary Engineering - Co-treatment of septage and wastewater; 1998-1999.
Summarised Results of Ongoing and Completed Field Research
Planted sludge drying beds (field research at AIT)
Field experiments were started in April 1997. Septage from the city of Bangkok is thereby treated on three parallel pilot drying beds each being 5x5 m in size and planted with cattail (Typha). Septage is loaded twice a week at rates equivalent to 80, 125 and 250 kg total solids/ m2 of bed surface·year. Results obtained from 6 months of FS loading are:
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solids content of drying sludge at the end of one week of drying: ~ 50 %; and
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removal of constituents in the percolate (as compared to the raw septage levels; Unfiltered COD and BOD, Kjehldahl nitrogen, susp. solids: ~ 95 %.
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Experiments will continue through the whole of 1998 in order to allow the assessment of the long-term performance, behaviour and operation of the cattail planted beds and to judge the suitability of constructed wetland for septage treatment.
Soil reclamation using septage (field research at the University of the Philippines' National Engineering Centre, UPNEC, Manila; completed).
The objective of the joint project was to answer the basic question whether the cultivation potential of soils which have been devastated by the volcanic ash produced by the Mt. Pinatubo eruption in 1991 and washed down into the intensively cultivated flood plains may be reclaimed by using septage. The project whose yard-scale experimental phase lasted from January - July 1997 yielded the following results:
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manila septage is high in plant nutrients and low in heavy metals;
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the use of septage on devastated soils is likely to enhance the growth of pioneer grass as well as of vegetable, as compared to not applying any extra nutrients/soil conditioner; and
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the use of septage is likely to lead to increased water holding capacity and organic matter contents in the treated soil.
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Co-Treatment Field Research Coming up in Argentina
Field research collaboration will be established between the University of Rosario's Dept. of Hydraulic & Sanitary Engineering and EAWAG/SANDEC on the subject of co-treating septage and wastewater. Field investigations will be conducted at a municipal treatment plant. The plant will comprise two ponds operated in parallel to pretreat septage (separate off and digest solids, in particular) and three ponds in series to co-treat wastewater and the septage supernatant. Field work is expected to start in the second half of 1998. The investigations will focus both on treatment performance with respect to COD, BOD, solids, ammonia, helminth eggs and faecal coliforms, and on operational aspects, including the management of process sludges, potential risks of ammonia toxicty to algae, pond operation.
Updated 31/01/03
Maintained by f.odhiambo@lboro.ac.uk and j.fisher1@lboro.ac.uk
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