|dc.description.abstract||Due to extreme high turbidity during typhoons or heavy rains, which resulted in difficulties in potable water treatment, the water intake well to draw water from upper levels of the reservoir was built in the Shihmen reservoir. After drawing water from the intake well, it was found that there were bubbles or foams on the surface in slow mixing tank and filter during backwash in Pingjan water treatment plant. Moreoever, the run time of filtration was significantly reduced and the filter was severely clogged.
In this research, two source waters were taken from Shihmen reservoir: one was the surface water at the water intake well, the other was from Pinghan water treatment plant while switched to intake water from the mid-point of the intake well, which locates at water level 228 m. Removal of turbidity, TOC, and DOC by pre-chlorination and coagulation were investigated. The effects of types of coagulants were also examined by using PACl, ferric chloride, and aluminum sulfate. Forwater taking from the reservoir, it was found that pre-chlorination promoted the removal of turbidity. Also, aluminum sulfate can effectively reduce the ratio of DOC, which suggests that Al-DOC complex were formed, and therefore, the residual turbidity was the highest. When the water was taking from the intake well (from Pingjan water treatment plant), it was found that only PACl was effective in the removal of turbidity. After pre-chlorination, the settling of ferric flocs became worse.