Speaker: Musa Manga
This study, investigated the performance of sanitation technologies encountered in Tamil Nadu, India in reducing pathogen hazards. Sanitation technologies were compared by their mean daily pathogen release to the environment. The study revealed that there is a meaningful difference in the total daily pathogen release from different sanitation technologies. Household (HH) lined tanks and lined pits exhibited excellent performance with approximately 5.1 Log10 reduction, followed by HH fully-lined tanks, Community toilets fully-lined tanks, and sewerage systems. The results suggest that safe containment of human excreta for an extended time has greater potential to reduce pathogen release into the environment.
Sanitation is an important intervention for reducing the spread and burden of diseases transmitted by pathogens found in human excreta. Since sanitation technologies (such as latrines, septic tanks, sewerage systems, etc.) are designed to interrupt the transmission of sanitation-related pathogens into the environment, then the number of pathogens that such technologies can inactivate before emptying or discharge to the environment, would seem a logical and useful indicator for assessing the performance of these technologies1,2,3. However, to-date, the relative public health hazards posed by the different sanitation technologies and their performance in reducing pathogen hazards before discharge to the environment is still not well understood. This study, therefore, investigated the performance of sanitation technologies encountered in our study communities (i.e. Trichy and Coimbatore, in Tamil Nadu, India) in reducing pathogen hazards. Using a faecal sludge deep sampler, faecal sludge samples were collected from the bottom, middle, and top or effluent of the containment systems. Samples were also collected from points of the sewerage system that are associated with frequent blockages and overflows. Flexible plastic bags were used for collecting direct discharge from the black-water pipes. Volume of human waste overflowing/ leaking to the environment from the different sanitation technologies was also estimated. All collected samples were analysed for Escherichia coli (E. coli), and Total solids. Technologies were compared by their mean daily pathogen release to the environment. Total daily pathogen release was computed as a sum of the effluent/ overflows and period desludging contribution to average daily pathogen release.
The results revealed that there is a meaningful difference in the daily pathogen release due to effluent/ overflows from sanitation technologies. Interestingly, community toilets (CT), sewer points and black pipes exhibited the highest daily pathogen release per capita due to overflows/ effluent, in the range of 10.5 -12.5 E. coli Log10. Household fully-lined tanks, lined pits, and lined tanks recorded the lowest daily pathogen release per person – exhibiting about 1-2 E. coli Log10 reduction. This study finding confirms that black pipes, sewers, and CT overflowing to the environment may act as “hypodermic needles” of pathogens. The study revealed that the daily pathogen release associated with the liquid fraction (overflows/ effluent from sanitation technologies) is approximately 50 and 2.5 times higher than that associated with the solids fraction for fully-lined tanks and CT, respectively. This is a significant finding to the sanitation planners/ engineers as it aids the prioritizing of sanitation interventions that will maximize public health benefits. Furthermore, the results revealed that there is a statistically significant difference in the total daily pathogen release from different sanitation technologies, with p = 0.00001. Household (HH) lined tanks and lined pits exhibited excellent performance with approximately 5.1 Log10 reduction, followed by HH fully-lined tanks, CT fully-lined tanks, and sewerage systems with 2.3, 0.9, and 0.3 Log10 reduction, respectively. This study results suggest that safe containment of human excreta for an extended time has greater potential to reduce the release of pathogen hazards into the environment since extensive pathogen inactivation usually occurs during containment.
The study revealed that the Community Toilets (CT), sewer points and black pipes are associated with the highest daily pathogen release due to overflows/ effluent. This finding confirms that black pipes, sewers, and CT overflowing to the environment may act as “hypodermic needles” of pathogens. Therefore, sanitation planners should not just prioritize the extension of CT and sewerage services to communities, but they should also pay much attention to the operation and routine maintenance of the CT and sewerage systems to minimize leakages /overflows, and associated pathogen release to the environment. The study revealed that the daily pathogen release associated with the liquid fraction (overflows/ effluent from sanitation technologies) is approximately 50 and 2.5 times higher than that associated with solids fraction for fully-lined tanks and CT, respectively. This finding suggests that although faecal sludge management is important, more efforts should be directed to the proper management of the liquid fraction from the on-site sanitation systems. Further, this study results suggest that safe containment of human excreta for an extended time has greater potential to reduce the release of pathogen hazards into the environment as well as the spread of excreta-related diseases since extensive pathogen inactivation usually occurs during containment.
1. Mills
F.Willetts
J.Petterson
S.Mitchell
C. and Norman
G. 2018. Faecal Pathogen Flows and Their Public Health Risks in Urban Environments: A Proposed Approach to Inform Sanitation Planning. International Journal of Environmental Research and Public Health. 15(2)
p181.
2. Williams
A. and Overbo
A. 2015. Unsafe return of human excreta to the environment: A literature review. The Water Institute at UNC
Chapel Hill
NC
USA.
3. Kolsky
Pete
Lisa Fleming
and Jamie Bartram. “Proof of Concept of Estimates for the Unsafe Return of Human Excreta: Models of Unsafe Return of Excreta in Four Countries.” 2019. The Water Institute at the UNC
Chapel Hill
NC
USA.