Source water for water treatment plants (WTP) in certain areas of Taiwan has been seriously contaminated, while the traditional operation of the WTP has been proven ineffectively in lowering the concentration of the contaminants. Therefore, water quality contingency occurs frequently. For example, when the raw water contains high level of organic matter, chlorination may produce trihalomethane exceeding the drinking water standard; or the sudden increase of the concentration of arsenic, iron and manganese in the groundwater may result in unacceptable drinking water quality and jeopardize the water safety of the residents. This project will first investigate the case of water quality contingency and identify the main cause for poor water quality to establish the countermeasure for emergency response. In addition, a task force will be formed by water treatment professionals to provide technical assistance for the operation in the Lienchiang WTP and to evaluate the operation performance of five waterworks. Then, a training program will be conducted for water treatment operators. A symposium will be held to conclude the major operational problems of the Lienchiang WTP as well as to present the strategy for improving the drinking water quality of the Lienchiang WTP. In addition, this project will assist the Water Resources Agency (WRA) in the maintenance of the membrane filtration module of a local small water treatment system in New Taipei City and the inspection and guidance to five small water treatment systems. Finally, an annual supervision plan will be proposed to give WRA a guideline for inspection and guidance to small water treatment plants.