Sanitizing on-site pit sludge during emergency situations using vermicompost, terra preta (anaerobic dry toilet) and anaerobic digester toilets

Abstract

Reaponse to emergency sanitation faces faecal sludge containment and treatment challenges. As a result in emergency camps frequently experience faecal-oral related disease outbreaks. In search of possible solutions the Anaerobic Digester, Terra Preta and Vermicompost toilets were placed under observations as they either lacked on-site scientific evidence, or there was contradicting literature regarding their performance during emergency situations. Using randomly selected grab samples, the sanitation systems were assessed for faecal sludge stabilization (Temperature, pH, and Chemical Oxygen Demand), pathogen reduction (Escherichia coli and Total Coliforms) and useful agricultural by-product generation (Total Ammonia Nitrogen).The results indicated that Anaerobic Digester sanitised faecal sludge in summer (E. coli/100ml <103/100ml) but not in winter (7.96 x 105 E. coli/100ml). In both seasons, faecal sludge never got stabilised (110.08mg/l in winter and 278.20mg/l in summer for COD) although it produced fertiliser rich by-product (15.17mg/l in winter and 25.58mg/l in summer for TAN). The Anaerobic Digester also harvested 5m3/day biogas against the designed 10m3/day biogas volume due to its observed limited capacity of converting Chemical Oxygen Demand from faecal sludge to methane (CH4) as evidenced by the 17% COD removal difference in the collected data. The LAB led TPS system harvested rich in Total Ammonia (16.58mg/l) and pathogen free (E. coli/100ml <103/100ml) urine but got challenged in reducing Lacto-Fermented Sludge pathogens (1.05 x107 E. coli/100ml and 2.18 x 107 TCFU/100ml) to below Malawi Standard (<103CFU/100ml) and stabilising faecal sludge to 60mg/l. The worms showed the capacity of increasing Total Ammonia Nitrogen concentration of faecal sludge by 14.38% in winter and 27.37% in summer. However they got challenged in producing pathogen free vermicompost (7.72 x 105 E. coli/100ml in winter and 1.53 x 107 E. coli/100ml in summer and 9.42 x 105 TCFU/100ml in winter and 5.33 x 107 TCFU/100ml in summer) and stabilized vermicompost (348.31mg/l winter and 534.85mg/l summer). In conclusion, the results observed under this study suggest that the three proposed sanition systems should not be recommended for use during an immediate phase of an emergency situations as they have demonstrated inconsistences in as far as pathogen reduction and faecal sludge stabilization is concerned. However, further studies in actual emergency situations and improvements of the sanitation systems could help in coming up with an informed decision on their functionality.