Improving microalgal growth and nitrogen, and phosphorus removal by electric field in municipal wastewater

Abstract

The promoting effect of electric fields on the growth and lipid production of microalga provides a new research direction for biorefining. However, researchers have rarely applied this technology to the treatment of actual wastewater. In this study, the dry weight and lipid content of microalgae increased by 47.45 % and 28.28 %, respectively, when optimized for light, growth phase and energization time. By optimizing the initial microalgal concentration and the ratio of nitrogen and phosphorus, the removal of total nitrogen (TN) and ammonia nitrogen (NH4+) increased by 18.5 % and 10.9 %, respectively. Compared to peroxidase (POD), significant changes in the relative activities of catalase (CAT) and total superoxide dismutase (T-SOD) were observed after the application of an electric field to the microalgae. Along with the cultivation, the relative activities of T-SOD and CAT showed a tendency of an increase and then a decrease compared with the control. This was mainly due to the increased internal secretion of T-SOD and CAT by the microalgae in response to the oxidative stress of the electric field on the microalgae, while the lack of nutrients at the later stages of cultivation also led to the increase of the content of the two enzymes in the control.