Water-lifting aerator reduces algal growth in stratified drinking water reservoir: novel insights into algal metabolic profiling and engineering applications

Abstract Water-lifting aerator (WLA) developed by Dr. Tinglin Huang in Xi’an University of Architecture and Technology is a multi-function water quality improvement technique that significantly inhibits the occurrence of HABs in deep drinking water reservoirs. However, the biological mechanism of WLA to suppress algal growth has not been comprehensively understood. Here, the cellular mechanism that allows WLA to control HABs was explored based on laboratory simulation and field investigation. Under simulated hydrodynamic conditions, the results showed that cell density, chlorophyll a content, chlorophyll fluorescence parameters, and dehydrogenase activity in Microcystis aeruginosa all peaked under light conditions at 25°C. The metabolic activity of M. aeruginosa varied significantly under low temperature and light conditions when cultured for 48 h. The extracellular organic matter (EOM) and intracellular organic matter (IOM) contents of M. aeruginosa were both resolved into three components. Moreover, the total fluorescence intensities from EOM and IOM both peaked under light conditions at 25°C. The field investigation showed that the growth of algae was decreased significantly in Lijiahe reservoir with water-lifting aerator application. The chlorophyll fluorescence parameters decreased significantly after vertical mixing, thereby indicating that the WLA weakened the photosynthetic ability and destroyed the biological activity of algae. In addition, the WLA significantly affected the vertical distribution of the phytoplankton community composition. Altogether, these results shed new lights on understanding the control of algal blooms by WLA in stratified drinking water reservoirs.