This study aimed at estimating the sanitizing effectiveness of urea treatment by studying the inactivation kinetics of selected indicator microorganisms. Finished composts from a composting toilet were inoculated with indicator microorganisms and subjected to different urea concentrations (0.5–2% w/w) and temperatures (22, 32 and 42°C). The inactivation kinetics parameters were determined in relation to pH, ammonia content and temperature during treatment time. The results show that urea addition to compost enhanced inactivation of microorganisms. The decline in number of E. coli and Enterococus followed a linear reduction, while that of Ascaris lumbricoides eggs followed a linear reduction plus shoulder. The inactivation rate constants of all microorganisms tested were positively correlated to the increase of NH3(aq) concentration and temperature. The relationship between the inactivation rate of microorganisms, ammonia through urea concentration and temperature were established. Therefore, the best decimal decay of E. coli, Enterococus and A. lumbricoides eggs occurred with 2% w/w urea concentration at 42°C within 0.9, 1.1 and 1.4 days, respectively. E. coli was the most sensitive microorganism to urea treatment, while Enterococcus and A. lumbricoides eggs showed resistance, especially at lower temperatures. Urea treatment has proved to be an efficient option for safe reuse of compost from composting toilets.

The study aimed to reduce the storage time of urine treatment and assess the quality of treated urine after Solar DISinfection (SODIS) method. Microbiological analyses were performed on urine samples taken before each sunlight exposition, between 10am and 4pm at a frequency of 1 h, during which temperature was measured in PET bottles (1.5 L). The initial concentrations of Escherichia coli (E. coli) and Salmonella in unstored urine were 106 and 103 CFU/100 mL respectively. The combined effect of temperature and UV radiation increased inactivation efficiency of E. coli at 5 log units. On the other hand, 98% of Salmonella were inactivated in less than 3 h of continuous exposure between 12am and 3pm with temperature varying between 50 and 65 °C in PET bottles. The k values showed that the inactivation rate of Salmonella tested was accelerated when the temperature was above 50 °C. Then, the results indicated that the first-order exponential decay model is suitable to predict the inactivation of Salmonella in urine by SODIS the best way. General results showed that after 3 days of exposure to sunlight, urine collected via eco-toilet becomes bacteriological sanitized and therefore can be used in agriculture.

Greywater is a valuable additional water source for agriculture in arid and semi‐arid countries subject to water scarcity. However, the impacts of applying greywater to agricultural land in the Sudano‐Sahelian regions are not adequately understood. This study evaluates the impacts of using greywater, treated by the High Rate Algal Ponds system (HRAPs), on soil characteristics and okra growth and yield in the Sudano‐Sahelian regions. The methodology consisted of growing okra under four different irrigation conditions: (i) treated greywater (TGW); (ii) fresh well water (FWW); (iii) TGW and chemical fertilizer (TGW + FERT) and (iv) FWW and chemical fertilizer (FWW + FERT). The test beds were sampled before and after cultivation to analyze soil pH and sodicity status (e.g., sodium absorption ratio: SAR). The okra growth, fruit yield and total dry biomass were recorded. Fresh fruit weight is significantly higher with TGW (761.17 ± 53.69 kg.ha−1) compared to FWW (497.15 ± 100.02 kg.ha−1) and FWW + FERT (307.93 ± 100.04 kg.ha−1). This result likely occurs due to the nutrients (e.g., nitrogen) present in TGW. Conversely, the average SAR of soil irrigated with TGW + FERT (12.47) and TGW (8.83) are significantly higher than those of the soil irrigated with FWW (2.92) and soil before cultivation (0.95). Therefore, it is recommended that soil salinity or/and sodicity is monitored when irrigating with TGW and that well water is used for every third irrigation cycle to prevent soil degradation though increased salinity. Overall, the appropriate reuse of greywater improves food security and the sustainability of agriculture in arid to semi‐arid regions. © 2017 American Institute of Chemical Engineers Environ Prog, 37: 465–470, 2018

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