Case Study on Accidents Pollution of Secondary Water Supplies

Objectives To understand the reasons and features of accidents for the pollution of secondary water supplies.

Methods Twenty eight pollution cases for secondary water supply were collected, and their reasons, management and prevention measures were analyzed retrospectively.

Results The main form of pollution for secondary water supply was biological pollution, accounted for 85.7%, such as the countercurrent flow of sewage to the reservoir located in lower position, the breakage and leakage of reservoir and pipelines, and the water polluted directly by contaminants; the incidences were 35.7%, 17.9%, 10.7% and 14.3% respectively.The investigation and management should be started from these items firstly.The main manifestation of health hazard was in digestive system, accounted for 60.7% of all symptoms.

Conclusions Appropriate indexes should be selected to increase the efficiency of investigation.The management should be considered comprehensively, including eliminating risks from the source and to protect the exposed population.Preventive examination and daily supervision should be strengthened to avoid the occurrence of secondary water supply accidents.When condition was permitted, using a kind of non-negative pressure water supply system to replace the secondary water supply system was suggested to shorten the water supply chain.