Using co-occurrence network to explore the effects of bio-augmentation on the microalgae-based wastewater treatment process

Abstract

Microalgae-bacteria consortia is considered to be an efficient way to improve wastewater treatment. However, the interactions between microalgae and bacteria were not clear. In this study, commercially available bacterial inoculum were used as bio-augmentation to improve the performance of microalgae-based wastewater treatment. Co-occurrence network analysis was used to investigate the interactions between microalgae and bacteria. Results showed that bio-augmentation could increase both microalgal growth and wastewater treatment efficiency. Microalgal biomass increased by 1.2 times. Removal efficiencies of total organic carbon, ammonium nitrogen and total phosphorus increased by 5.27%, 3.41%% and 5.74%, respectively. Decreasing trends for Cyanobacteria and Salinarimonas but increasing trends for Cyclobacteriaceae were observed in the microalgal culture system with bio-augmentation. Greater variations of microbial community were found in the treatment without bio-augmentation. Co-occurrence network analysis showed that the main functions of microbial community in the treatment with bio-augmentation were both nutrient removal and organic pollutant degrading. For the treatment without bio-augmentation, main function of microbial community was nutrient removal. It indicated that bio-augmentation increased the number of organic degrading bacteria, such as Bacillus and Paenibacillaceae. The interactions between these bacteria and microalgae promoted the degradation of organic pollutants in the wastewater, providing sufficient inorganic carbon sources for the photosynthesis of microalgae and thus promoting the growth of microalgae and the removal of nitrogen and phosphorus from wastewater.