Assessing source water reservoirs as pre-treatment units for simultaneous control of autochthonous and runoff...

As reservoirs become the primary drinking water sources, autochthonous contamination and runoff pollution have become major causes of periodic water quality deterioration at downstream treatment plants. Therefore, implementing in-situ water quality enhancement has become essential. This 3-year study assessed the feasibility of reservoirs using Water-lifting aerators (WLA) as pre-treatment units under autochthonous and runoff pollution, analyzed its effect on downstream oxidant demand and provides practical guidance. This will contribute to achieving more efficient treatment and reducing energy waste and other costs during reservoir management and drinking water treatment processes. Results showed that thermal stratification created anoxic conditions in bottom water of SBY Reservoir, triggering a sequential cascade of dissolved pollutant mobilization and deterioration of water supply quality. Runoff pollution deteriorates the water quality of reservoirs and downstream water treatment plants by introducing substantial loads of particulate and dissolved pollutants. The WLA system, via bottom aeration and full-layer mixing, raises the dissolved oxygen (DO) levels and temperature of bottom water in summer. This approach can reduce the amount of reductive pollutants from autochthonous pollution and, when dealing with runoff pollution, induce high-turbidity runoff to flow to the reservoir bottom, thereby promoting particle settlement. WLA operation has led to a considerable reduction in oxidant dosage at the downstream plant. These findings provide operational frameworks for optimizing reservoir management through artificial mixing and aeration technology, thereby enhancing the role of reservoirs in integrated drinking water treatment systems.