While standard methods for chlorine taste and odor (T&O) detection and rejection thresholds exist, little rigorous research has been conducted on T&O thresholds in humanitarian settings. To fill this gap, we estimated chlorine T&O detection and rejection thresholds using the Forced-Choice Triangle Test (FCT) and Flavor Rating Assessment (FRA) standard methods in a Ugandan refugee settlement. We conducted these tests with 410 male and female participants, aged 5–72 years, using piped and trucked surface water and bottled water. We also conducted 30 focus group discussions and 37 surveys with data collectors. Median chlorine detection thresholds were 0.56, 1.40, and 1.67 mg/L, for piped, trucked, and bottled water, respectively. Rejection was calculated using ratings (as per the method) and five different previously-used thresholds, and was 1.6, 2.0, and 1.6 mg/L (ratings) and 2.19, 1.85, and 1.67 mg/L (using the FCT threshold method with FRA data) for piped, trucked, and bottled water, respectively. Detection and rejection thresholds were significantly associated with water quality (including turbidity, pH, electrical conductivity, and temperature), participant age and education. We observed high intra- and inter-individual variability, which decreased with participant experience. We found the method used to calculate rejection thresholds influenced results, highlighting the need for a standard method to analyze FRA data. Data collectors and participants recommended shortening protocols and evaluating fewer concentrations, and highlighted difficulties in creating accurate FRC concentrations for testing. This study provides insights on using standard methods to assess T&O thresholds in untrained populations, and results are being used to develop rapid field T&O protocols for humanitarian settings.

In refugee and internally displaced person settlements, hygienic water handling and free residual chlorine (FRC) are crucial for protecting water against recontamination after distribution up to the household point-of-consumption. We conducted a secondary analysis of water quality and water handling data collected in refugee camps in South Sudan, Jordan, and Rwanda using statistical and process-based modeling to explore how water handling practices affect FRC decay and household FRC outcomes. The two practices that consistently produced a significant effect on FRC decay and household FRC were storing water in direct sunlight and transferring water between containers during household storage. Samples stored in direct sunlight had 0.22–0.31 mg/L lower household FRC and had FRC decay rates between 2 and 3.7 times higher than samples stored in the shade, and samples that were transferred between containers had 0.031–0.51 mg/L lower household FRC and decay rates 1.65–3 times higher than non-transferred samples in sites in which the effect was significant, suggesting that humanitarian responders should aim to provide additional water storage containers to prevent water transferring in households and encourage water-users not to store water in direct sunlight. By contrast, the effect of the three recommended hygienic water handling behaviors (clean, covered containers and drawing by tap or pouring) was mixed or inconclusive. These inconclusive results were likely due to imbalanced or unreliable approaches to gathering the data, and we recommend that hygienic water handling practices that mechanistically provide a physical barrier against recontamination should always be promoted in humanitarian settings.

The Safe Water Optimization Tool (SWOT) generates evidence-based point-of-distribution free residual chlorine (FRC) targets to adjust chlorine dosing by operators and ensure water quality at point-of-consumption. To investigate SWOT effectiveness in surface waters, we conducted two before-and-after mixed-method evaluations in a Uganda refugee settlement served by piped and trucked surface water systems. We surveyed 888 users on water knowledge, attitudes, and practices; collected 2768 water samples to evaluate FRC,Escherichia coli, and disinfection by-products (DBPs) concentrations; and conducted nine key-informant interviews with system operators about SWOT implementation. After baseline data collection, SWOT chlorination targets were generated, increasing point-of-distribution FRC targets from 0.2 to 0.7-0.8 mg/L and from 0.3 to 0.9 mg/L for piped and trucked systems, respectively. At endline, household point-of-consumption FRC ≥ 0.2 mg/L increased from 23 to 35% and from 8 to 42% in the two systems. With these increases, we did not observe increased chlorinated water rejection or DBPs concentrations exceeding international guidelines. Informants reported that SWOT implementation increased knowledge and capacity and improved operations. Overall, SWOT-generated chlorination targets increased chlorine dosage, which improved household water quality in surface waters although less than previously documented with groundwater sources. Additional operator support on prechlorination water treatment processes is needed to ensure maximally effective SWOT implementation for surface water sources.