ORGANIC STABILIZATION AND NUTRIENTS PRODUCTION WITH RESOURCE RECOVERY FROM ANAEROBIC PASTEURISATION DIGESTER LATRINE

Abstract

Pit latrines are the most common human excreta disposal systems in low- income countries. Their use is on the rise as countries aim to meet the sanitation-related target of the Millennium Development Goals. However, there is concern that they discharge chemical and microbial contaminants to groundwater. Furthermore, pit latrines have no option for resource recovery and recycling of materials. This study aimed at assessing the suitability of Anaerobic Pasteurisation Digester latrine (APDLs) in organic matter reduction, organic nutrients production and resource recovery from the final effluent. The study hypothesises that there are no organic reduction, no nutrients produced and no resources can be recovered. Three toilet systems were installed at Sogomo with different digester feed stocks, namely: one with faeces and urine (North station), another with urine, feaces and food scrubs (Central station) and the last one with urine diversion (South station). The three toilet systems were installed for approximately, twenty adult users for each. The Digesters installed consisted of a movable built floating gas holder (dome), heater and heat exchanger. Chemical Oxygen Demand (COD) and Biological Oxygen Demand (BOD) were used to determine the organic reduction. BOD was measured using the winker method and COD was done by the refluxing method. Colorimetric technique was used to analyse total nitrogen and direct method was used for total ammonia analysis, where effluent samples were treated with strong base and the mixture distilled. Ammonia was quantitatively expelled and was absorbed in excess of standard acid solution. The excess acid was back titrated in the presence of methyl red indicator. The ammonia contained in the final effluent was used as the raw material for production of recoverable resources from the system including ammonium hydroxide, ammonium chloride, ammonium sulphate and ammonium nitrate this was done by the acid base reaction. Statistical analysis was carried out using two-way ANOVA by SPSS computer aided programme version 21.0.The BOD percentage reductions in North, South and Central stations were 89.48 %, 92.60 % and 90.09% respectively. The COD reduction in South and Central stations showed a mean of 95 % while the north station had a mean of 93 %. South, North and Central station had mean values of 6.22 mg/l, 5.74 mg/l and 5.50 mg/l of total nitrogen in the digested effluent respectively. Total ammonia values in the digested effluent were 12.35 mg/l, 11.76 mg/l and 10.76mg/l at south, central and north station respectively. The values of total ammonium ions in the digested effluent were 15.91 mg/l, 13.97 mg/l and 15.22 mg/l at south, north and central stations respectively. Therefore, with high and increasing human populations, the ADPLs are suitable for organic matter reduction. The three ADPLs final effluent could be used as organic fertilizer because it contained more than 4.50 mg/l of total nitrogen which is greater than the recommended nitrogen requirement by plants of 3.20 mg/l. The ADPLs technology has a great potential of replacing pit latrines.