Control Of Corrosive Water In Advanced Water Treatment Plant By Manipulating Calcium Carbonate Precipitation Potential

摘要

The corrosion of metal pipes in water distribution networks is a complex electrochemical and physico-chemical phenomenon between a metal surface and corrosive water. The level of corrosion in water distribution systems was controlled by manipulating the calcium carbonate precipitation potential (CCPP) concentration, and the corrosive water quality was controlled in two steps within the advanced water treatment plant (AWTP) constructed at the Institute of Water Quality Research (IWQR), Busan Metropolitan City, Korea. The 1st control step was located before a coagulation process included on a rapid mixer, and the 2nd control step was located after a biological activated carbon (BAC) process. The capacity of the AWTP in IWQR was 80 m~3/day. The CCPP concentration was controlled from the calcium hardness, alkalinity, and pH by adding calcium hydroxide (Ca(OH)_2), sodium carbonate (Na_2CO_3), and carbon dioxide (CO_2) in the above two steps. A CCPP control system was installed and operated according to the developed algorithm to maintain a CCPP range of 0-4 mg/L. The CCPP range was reasonably controlled to induce the formation of a CaCO_3 film on the surface of the simulated water distribution system (SWDS). From the result of the corrosive water control, the CCPP formed greater than 0.0 mg/L. The crystalloid structure of the scale produced by CCPP control in the inner surface of pipe was zinc carbonate hydroxide hydrate (Zn_4CO_3(OH)_6·H_2O).