Survival of Fecal Coliforms in Dry-Composting Toilets

Abstract

The dry-composting toilet, which uses neither water nor sewage infrastructure, is a practical solution in areas with inadequate sewage disposal and where water is limited. These systems are becoming increasingly popular and are promoted to sanitize human excreta and to recycle them into fertilizer for nonedible plants, yet there are few data on the safety of this technology. This study analyzed fecal coliform reduction in approximately 90 prefabricated, dry-composting toilets (Sistema Integral de Reciclamiento de Desechos Orgánicos [SIRDOs]) that were installed on the U.S.-Mexico border in Ciudad Juárez, Chihuahua, Mexico. The purpose of this study was to determine fecal coliform reduction over time and the most probable method of this reduction. Biosolid waste samples were collected and analyzed at approximately 3 and 6 months and were classified based on U.S. Environmental Protection Agency standards. Results showed that class A compost (high grade) was present in only 35.8% of SIRDOs after 6 months. The primary mechanism for fecal coliform reduction was found to be desiccation rather than biodegradation. There was a significant correlation (P ‫؍‬ 0.008) between classification rating and percent moisture categories of the biosolid samples: drier samples had a greater proportion of class A samples. Solar exposure was critical for maximal class A biosolid end products (P ‫؍‬ 0.001). This study only addressed fecal coliforms as an indicator organism, and further research is necessary to determine the safety of composting toilets with respect to other pathogenic microorganisms, some of which are more resistant to desiccation.

Hyperendemic Cryptosporidium and Giardia in households lacking municipal sewer and water on the United States-Mexico border.

“…13 These findings indicated that due to the hot, dry climate of the Chihuahuan desert, composting by biodegradation was not effective due to a rapid desiccation. As a result, after six months treatment of biowaste, only 36% of composting toilets produced United States Environmental Protection Agency (USEPA) Class A compost based on fecal coliform counts (< 1,000 most probable number fecal coliforms/gram).…”

“…A previous study analyzed these ecologic systems for their ability to re-duce fecal coliforms and found a significant reduction over time. 13 A simple random sample of 90 households using SIRDOs in these three communities was selected. Complete data were available for 77 of this sample.…”

“…Biosolid samples (total 100−200 grams fresh weight) were placed in a plastic bag and mixed to homogeneity by massaging the bag as previously described. 13 Samples were transported to the laboratory in an ice chest within two hours of collection, stored at 4°C, and analyzed for Giardia and Cryptosporidium within 24 hours. After analysis, samples were disinfected or autoclaved.…”

Use of the co-composting time extract agar to evaluate the microbial community changes during the co-composting of activated sludge and date palm waste

“…Several authors (Gaspard and Schwartzbrod 2003;Cofie et al 2006;Koné et al 2007;El Fels et al 2014b) showed that the rise of temperature during the thermopilic stage leads to hygeinization. Furthermore, Redlinger et al (2001); Pietronave et al (2004) and Bhatia et al (2013) noted that a significant decrease of faecal coliforms and faecal Streptococci during composting. Paniel et al (2010) demonstrated that faecal Enterococcus was not observed during the stabilization phase.…”

“…Most published work has used enterococci and thermotolerant coliforms as faecal contamination indicator organisms (Redlinger et al 2001). Their presence indicates poor hygiene.…”