SWC has three wells that deliver raw water through a transmission main to the Water Treatment Plant (WTP). A modulating control valve at the WTP controls the amount of raw water that bypasses the WTP. Adsorption units at the WTP treat the remaining raw water flow. The WTP is equipped with two parallel adsorption trains. Each train consists of two adsorption units or vessels, operating in series. The second adsorption unit in each train provides finishing treatment or break-through protection.
The treated water blends with the raw water, which bypassed the WTP. The blended water then flows to the reservoirs. A tablet feed chlorinator provides chlorine solution at the inlet and outlet of the WTP. Chlorine solution oxidizes As3 to As5 in the raw water before entering the adsorption trains. The chlorinator also maintains the chlorine residual in the treated water as it leaves the WTP. The modulating control valve controls the raw water bypass flow to achieve a target arsenic content in the blended water and to optimize the usage of adsorption media. The system is intended to reduce the calculated arsenic content of the blended water to a target setpoint of [7 PPB] and maintain it below the mandatory compliance limit (MCL) of [10 PPB] in cases where the target setpoint cannot otherwise be met.