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and E in different years (1996-2002) were sampled. The systems in Blocks C (1996) and D (1996) were old and from the R & D phase and the systems in Blocks B (2001) and E (2002) were from the promotion and installation phase. Out of the 4 systems, soak pits were present in the systems of Blocks B and C and absent in the systems of Blocks D and E. Samples from each of the biogas based sewerage systems were collected from the locations as shown in Figure 6.5. The wastewater was collected for testing from the following points: (1) from inside a connection pit at the end of lane collecting waste from 24 plots, (2) from inside an inlet tank just in front of the biogas chamber, (3) from inside a hydraulic chamber, and (4) from inside a soak pit. When there was no soak pit, sample 4 was collected from the outlet pipe of the hydraulic chamber as it discharged wastewater into the canal or big surface drain of the area. Sample 5 was collected from the canal at the point where the effluent was discharged. Raw wastewater was also collected from the connection pit of a pit latrine that was not connected to the biogas based sewerage system. In most of the following collection points 2 (inside inlet tank), 3 (inside hydraulic chamber) and 4 (inside soak pit), the wastewater was found in a solidified state in most of the facilities except for the facility in Block D. Thus, the sampling was done by either rubbing/cutting the solidified waste or by collecting the overflowing wastewater. It was observed during the sample collection that most of the sampling points, particularly biogas chamber, hydraulic chamber and all the soak pits, were buried a few to several meters under the surface as concrete roads were constructed on top of them. The digging and breaking of the roads to such depth was not an easy task, as much care was necessary not to damage the system itself while digging up the road. Due to this difficulty, it was not possible to reach a biogas based sewerage system in Block A to collect samples, thus excluding Block A from the analysis. According to the local people, the systems were not cleaned or opened since their installation. This was due to the fact, as mentioned earlier, that it was not an easy task to reach the systems. It appeared that the sewage was solidifying and being deposited in the different chambers, leading the untreated wastewater to flow over the solidified sewage in the biogas chamber and hydraulic chamber in three out of the four sampled systems (this occurrence is known as short-circuiting). Therefore, the waste was not given a chance to sufficiently decompose, which indicated inadequate treatment. In addition, one of the systems was also observed to be leaking wastewater from the hydraulic chamber. The results of this chemical analysis are summarized in Table 6.3. The bio-chemical condition of the systems can be observed from the data in Figures 6.6-6.9. Referring to Figures 6.6-6.9, the overall treatment of wastewater in general showed problems, as very little difference was observed when the influent (point 2) and effluent (point 4) of the different biogas systems were compared. It is not easy to comment on the merits of the individual components of each of the systems, because there were too many operational variations on how each system was functioning and the size of the sample was too small for a concise comparison (4 out of 20 systems). Table 6.3: Results of the chemical analysis of the wastewater from each biogas based sewerage system. 44
According to the structural guideline for the human-waste treatment facilities using anaerobic digestion, Japan (Japan Waste Management Association, 1978), the appropriate conditions to achieve the removal of BOD by 80% or to below 2,500 mg/l by anaerobic digestion are as follows; • Retention time: 30 days • Temperature: 37±2°C • pH: 6.5-8.2 • Carbon/Nitrogen ratio: 25-30 Considering these appropriate conditions, it seems that the retention time of the biogas chamber of the systems in Bauniabad was not enough. Furthermore, this problem of insufficient retention time possibly became more serious due to the solidification of waste inside the chambers that was observed in some cases, causing the waste to shortcircuit through the system. 45
Page 2 and 3: Authors Dr. Bilqis Amin Hoque, Envi
Page 5 and 6: Contents Foreword 5 Executive Summa
Page 7 and 8: Foreword Water and sanitation (WS)
Page 9 and 10: drinking water. All the various sam
Page 11 and 12: Lessons Learned and Recommendations
Page 13 and 14: List of Tables, Figures, Maps and P
Page 15: List of Abbreviations and Acronyms
Page 18 and 19: Photo 1.1 : A Street in Bauniabad P
Page 20 and 21: Chapter 1 Introduction 1.1 Backgrou
Page 22 and 23: Bauniabad was established as a spec
Page 24 and 25: 2.2 Water and Sanitation Educationa
Page 26 and 27: system in Bauniabad. For the trial
Page 28 and 29: scopes (financial resources) to obs
Page 30 and 31: Chapter 3 Methodology The cross-sec
Page 32 and 33: Chapter 4 Social Variables The soci
Page 34 and 35: when the people found the biogas ba
Page 36 and 37: Table 5.1: Physical performance and
Page 38 and 39: As the supply was not continuous, t
Page 40 and 41: It was observed that initially thos
Page 42 and 43: Chapter 6 Sanitation Sanitation pro
Page 44 and 45: 6.3 Costs and Financial Aspects The
Page 48 and 49: The effluents from the systems of B
Page 50 and 51: 48 • There should be research and
Page 52 and 53: 7.4 Observations of Water Use Pract
Page 54 and 55: Chapter 8 Lessons Learned and Recom
Page 56 and 57: the people had access to safe hygie
Page 58 and 59: Appendix 1 Summary Report of the Fi
Page 60 and 61: 14:00-15:30 Technical Session II co
Page 62 and 63: Appendix 2 Base Line Survey Form St
Page 64 and 65: SANITATION S-1: Use of Latrine:
Page 66 and 67: Table A-3.1: Results of the analysi
Page 68 and 69: 66 Table A-4.1: Sources of water us
Page 70 and 71: Table A-4.3: Sanitation practices i
Page 72: 70
Page 75 and 76: human poverty. UNDP, New York. UNIC
Page 77: Edited by L.S. Clesceri, A.E. Green

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