Technical Studies


The system of water supply management in Matsu area (2/2)

In Matsu area, it has been proven that worsened source water, poor operational performance of unit in water treatment plant (WTP) and weak management in water supply system are the major problem for water supply management. On the other hand, the operation and management of small water treatment plants in Taiwan area still need to be improved. It is anticipated that the results of this project will give Water Resources Agent (WRA) a guiding principle to improve the quality of drinking water and stability of water supply in Matsu area. Meanwhile, this project will assist WRA in supervising the self-management of small water treatment plants in each local government and improving the drinking water quality and stability of water supply. In this project, the system of water supply in Matsu area will be investigated. The inspection and guidance to local governments for managing small water treatment systems will be conducted, and demonstration for the operation of small water treatment plants will also be performed. In addition, the membrane filtration module (IS Water) applied in small water treatment systems will be tested and mantained.   The results showed that the turbidity and algae removal by coagulation-sedimentation coupled with prechlorination with the addition of ClO2 and NaOCl is superior to that with NaOCl for waterworks in Nangan and Beigan area. At the same chlorine dosage, preoxidatio with ClO2 and NaOCl can effectively improve the reduction in trihalomethanes formation potential (THMFP) of supernatants after coagulation-sedimentation. Moreover, it is found that the moss grew in the surface of sand within DynaSand® filtration unit in Chuishuiwo and Banli waterworks. This could affect the quality of filtrate. For Dongyong waterworks, the loss of filter media is severe when air-water backwashing is conducted. The filter media in upstream filter unit is composed of fiber in Xiju waterworks, and it is not suitable for water treatment, resulting in the limited filtration performance. The results also indicated that the pH and residual chlorine of finished water in Chuishuiwo and Banli waterworks is not stable with discontinuous operation as well as the conductivity of finished water vary after the desalinated waters are pumped into the finished water tank. In Nangan area, the residual chlorine in a small distribution reservoir varies significantly, which results in the unstable NaOCl dosing at a major distribution reservoir. The residual chlorine in Banli distribution reservoir as well as the residual chlorine in Dongyoun and Xiju distribution reservoir is relatively stable. However, the quantity of desalinated water in Nangan and Beigan islands in Matsu already exceeds 60% of total water supply. The cost spent on drinking water supply by waterworks and desalinated water treatment plant is increased year by year because of the facilities improvement or replacement. So far, the unit cost on water supply is increased more than 98 NTD/m3. On the other hand, the material and water fee management systems for Lienchiang WTP has been build and officially used. A QGIS system has been established to achieve effective data editing. This project also has periodically assisted the Water Resources Agency (WRA) in the maintenance of the membrane filtration module (IS Water) located at Hengshan elementary school in New Taipei City and Heping junior high school in Taichung City. During continuous membrane filtration, the effluents from two IS Water systmes comply with the standard of drinking water quality without post-chlorination. The supervision plan of small water treatment systems has been implemented to assist the WRA in conducting inspection and guidance to 16 local governments. After that, it is concluded that most operators of small water treatment plant could not have enough knowledge on water treatment and the total bacteria counts in finished water does not comply with the standard of drinking water quality.