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

Abstract

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.

Evaluation of System-Level, Passive Chlorination in Gravity-Fed Piped Water Systems in Rural Nepal

“…This technology has previously been evaluated at household water points in urban Bangladesh, 11 , 19 healthcare facilities in Tanzania, 20 and kiosks in Uganda. 14 , 21 …”

“…No prior published evaluations of this technology were identified, but it is a similar design to T-shaped erosion chlorinators evaluated elsewhere. 12 − 14 …”

“…However, while several passive chlorination technologies are compatible with rural piped water system infrastructure, few studies to date have evaluated the technical performance of these technologies in small rural piped systems, 12 , 13 and there exist almost no data on long-term costs of operation and maintenance. 14 …”

“…However, while several passive chlorination technologies are compatible with rural piped water system infrastructure, few studies to date have evaluated the technical performance of these technologies in small rural piped systems, 12,13 and there exist almost no data on long-term costs of operation and maintenance. 14 Our objective was to evaluate the impact of centralized, system-level implementation of these technologies on system and household water quality and user acceptability as well as the associated costs for operation and maintenance over 1 year. Our study was nested within a larger rural water safety intervention (REACH-Nepal), which implemented and evaluated a combination of water safety planning (WSP) interventions.…”

Evaluating the costs and components of a territory-wide household water storage and treatment program in the US Virgin Islands

“…For locally available water treatment options, previous work has been conducted to evaluate or predict the effectiveness of specific water treatment technologies including chlorination (Voth-Gaeddert & Schranck, 2021;Lindmark et al, 2022;Voth-Gaeddert et al, 2022a, 2022b, filtration (Voth-Gaeddert et al, 2022a), and UV (Voth-Gaeddert et al, 2022c) at the levels of whole-house (point-of-entry) and point-of-use. In addition, mechanisms to protect household cistern water from becoming contaminated have also been identified (Rao et al, 2022).…”