Influences of Heavy Metals in Water Treatment Chemicals on Drinking Water Quality and Risk Management

Water treatment chemicals (WTCs) are important raw materials during the drinking water production process. Occasionally unqualified WTCs with heavy metals were provided to Water Treatment Plant（WTP） by supplier during emergency situation，such as earthquake, typhoon and city block for epidemic disease, just because it cannot obtain the qualified WTCs. The harmful heavy metals in WTCs may expose a certain health risk to the quality of drinking water. In this paper, the influence of heavy metals in WTCs on the quality of drinking water was explored and the feasible management measures are proposed, taking the ILha Verda Water Plant (IVP) in Macao as an example. The study was based on the testing results of heavy metals in WTCs and treated water from 2017 to 2022 in IVP. A series of mathematical models were established to evaluate the content of heavy metals in water brought by WTCs. The removal rates of the water treatment process to the heavy metals were calculated at same time. The maximum allowable concentrations of heavy metals in WTCs were calculated and accessed. The results show that the drinking water is safety if the heavy metals in unqualified WTCs are under the maximum allowable concentrations. Then it is proposed for the classification of WTCs and risk management. The study will provide theoretical and technical support for water quality safety supervision and water supply management.