In the US Virgin Islands, >90% of households have rain catchment systems that utilize large cisterns; however, these systems are at high risk of microbial contamination. Available water treatment technologies provide varying levels of protection from microbial contamination and can be expensive. Therefore, we evaluated a low-cost water treatment train that included a passive chlorinator, carbon filter, and membrane filter to provide whole-house treatment for microbial contamination in a mock, pressurized, intermittent-use water system. Two types of locally available passive pool chlorinators were modified and tested for free chlorine residual (FCR) levels across a set of different water use scenarios. Additionally, tracer dye tests were conducted to evaluate chlorine contact time in the system, a carbon filter was evaluated for chlorine removal efficiencies, and a 1-micron nominal filter was evaluated for its effect on system pressure and microbial removal efficiencies. Results suggested the modified passive chlorinators provided relatively consistent chlorine dosing (offline: standard deviation range 0.54 to 0.79 ppm FCR, 3 trials, n=43; inline: standard deviation 0.53 ppm FCR, 1 trial, n=16) and tracer dye tests identified a minimum contact time for high flow rates (18.9 LPM, 5 GPM) of >45 s. The carbon filter reduced FCR levels from as high as 18.5 ppm to <0.13 ppm (n=9), while the 1-micron nominal filter had negligible effects on system pressure and provided 0.7 log 10 MPN/100 mL removal of total coliforms (n=9). The data suggest that passive chlorination can potentially be a low-cost option for whole-house water treatment for microbial contamination, but further research is needed to demonstrate system stability in a wider range of use cases over a longer period of time along with simplified practitioner protocols for field use. 

Design and Evaluation of a Household Chlorination System for Treating Cistern Water in the US Virgin Islands

Evaluating a Large-Scale Batch Chlorination Method for Household Cistern Water Treatment in the US Virgin Islands

Chlorine disinfection has become the most widely applied and indispensable technology in wastewater treatment and reuse to mitigate microbial risk and guarantee water safety. However, owing to complexities and high concentrations of contaminants in reclaimed water, rapid evaluation of chlorine disinfection efficacy is a crucial but challenging issue. Based on intensive experimental and statistical analyses, this study has established kinetic models and potential surrogates for rapid indication of the inactivation of microbial indicators and opportunistic pathogens during chlorine disinfection in different reclaimed waters. Overall, the constructed Selleck models performed very well to simulate log removal values (LRVs) of fecal coliforms, Pseudomonas aeruginosa and heterotrophic plate counts in all reclaimed water samples (R2 = 0.877-0.990). Moreover, total and Peak A fluorescence intensity as well as fluorescence integral intensities in Regions II and IV were found to have high response sensitivities during the chlorination process. Nevertheless, their effectiveness to act as potential surrogates of LRVs of microbial indicators needs to be further validated. The results from this study can provide valuable information on microbial safety surveillance of disinfection toward sustainable and long-term water reuse.

Quantitative models and potential surrogates for rapid evaluation and surveillance of chlorine disinfection efficacy in reclaimed water.

Quantitative models and potential surrogates for rapid evaluation and surveillance of chlorine disinfection efficacy in reclaimed water

Peracetic acid disinfection induces antibiotic-resistant E. coli into VBNC state but ineffectively eliminates the transmission potential of ARGs.

The world is not on track to meet Sustainable Development Goal 6.1 to provide universal access to safely managed drinking water by 2030. Removal of priority microbial contaminants by disinfection is one aspect of ensuring water is safely managed. Passive chlorination (also called in-line chlorination) represents one approach to disinfecting drinking water before or at the point of collection (POC), without requiring daily user input or electricity. In contrast to manual household chlorination methods typically implemented at the point of use (POU), passive chlorinators can reduce the user burden for chlorine dosing and enable treatment at scales ranging from communities to small municipalities. In this review, we synthesized evidence from 27 evaluations of passive chlorinators (in 19 articles, 3 NGO reports, and 5 theses) conducted across 16 countries in communities, schools, health care facilities, and refugee camps. Of the 27 passive chlorinators we identified, the majority (22/27) were solid tablet or granular chlorine dosers, and the remaining devices were liquid chlorine dosers. We identified the following research priorities to address existing barriers to scaled deployment of passive chlorinators: (i) strengthening local chlorine supply chains through decentralized liquid chlorine production, (ii) validating context-specific business models and financial sustainability, (iii) leveraging remote monitoring and sensing tools to monitor real-time chlorine levels and potential system failures, and (iv) designing handpump-compatible passive chlorinators to serve the many communities reliant on handpumps as a primary drinking water source. We also propose a set of reporting indicators for future studies to facilitate standardized evaluations of the technical performance and financial sustainability of passive chlorinators. In addition, we discuss the limitations of chlorine-based disinfection and recognize the importance of addressing chemical contamination in drinking water supplies. Passive chlorinators deployed and managed at-scale have the potential to elevate the quality of existing accessible and available water services to meet “safely managed” requirements.

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Megan Lindmark

Papers

Passive In-Line Chlorination for Drinking Water Disinfection: A Critical Review