Removal of environmental estrogens from wastewater by microalgae under the influence of bacteria
Xiao-Long Sun, Yuan Wang, Hao-Qin Xiong, Shao‐Ting Wang, Yi-Chuan Fang, Hong Xiang
Abstract
Environmental estrogens (EEs) have received a lot of attention in recent years due to their harmful effects and long latency period. Microalgae have been used for the removal of EEs because of their high removal efficiency, recyclability for energy, and low ecological side effects. In laboratory studies, the removal efficiency of EEs by microalgae was mostly above 80%, and the degradation period was about one week, which was a very good performance. This paper summarizes the degradation mechanism and pathway of EEs removal by microalgae and accordingly proposes a model for EEs removal: load - separation - transfer - degradation - reload. However, to apply microalgae in environments such as wastewater treatment plants, it is necessary to select microalgae species with high levels of antioxidant enzymes to withstand the toxic effects of high concentrations of EEs and also to consider the effect of bacteria on the removal process. Under normal conditions, microalgae and bacteria can compete for scarce resources in the water body, in addition to giving each other the nutrients they need. However, in the presence of EEs, the intermediate products produced by bacteria to degrade EEs can be toxic to microalgae, and the final small molecule organic acids will inhibit bacteria but will be taken up by microalgae, thus accelerating the process of accumulation of EEs by microalgae and enhancing the degradation rate. The synergistic and antagonistic effects of microalgae and bacteria together maintain the stability of EEs removal by the microalgae-bacterial system. The study of the equilibrium state of the microalgae-bacterial system will be of great value in establishing the treatment process in practical applications.