We investigated the quality of treated drinking water in Aida Camp and Alazzah Camp, two Palestinian refugee camps in the West Bank. Water supply in the two camps is intermittent: Water deliveries are first stored in a centrally located community tank before being pumped through distribution networks to users, who then store the water in rooftop tanks. Between March 2016 and June 2017, we examined water quality within the distribution system in the camps, testing 520 samples in Aida Camp and 198 samples in Alazzah Camp for total coliforms, Escherichia coli (E. coli) bacteria, and residual chlorine. We observed deterioration in water quality in both camps, but the deterioration was more pronounced in Aida Camp where 2.5% of community-tank samples, 5.0% of network samples, and 10% of rooftop-tank samples contained one or more colonies (per 100 mL) of total coliform bacteria. In Alazzah Camp, 3.7% of community-tank samples, 2.5% of network samples, and 5% rooftop-tank samples contained one or more colonies (per 100 mL) of total coliform bacteria. E. coli was detected in two samples from Aida Camp and one sample from Alazzah Camp. In both camps, average residual chlorine concentrations were higher in the community tanks than in rooftop tanks. The main factor influencing water quality deterioration in rooftop tanks in Aida Camp appears to be air temperature. We recommend more systematic water testing in the camps and greater transparency in reporting test results to camp residents. © 2019 by the authors.

Refugee camps E. coli Drinking water quality Residual chlorine Intermittent water supply Total coliforms

chlorine distribution system Water distribution systems Escherichia coli coliform bacterium Palestine potable water E. coli Residual chlorines Intermittent water supply Total coliforms Water tanks Refugee Camps Occupied Territories West Bank water treatment deterioration Drinking Water water supply Water quality