Towards advanced nutrient removal by microalgae-bacteria symbiosis system for wastewater treatment

In this study, the microalgae-bacteria symbiosis (ABS) system by co-culturing Chlorella sorokiniana with activated sludge was constructed for pollutants removal, and the according interaction mechanism was investigated. The results showed that the ABS system could almost completely remove ammonia nitrogen, and the removal effi-ciency of total nitrogen and total phosphorus could accordingly reach up to 65.3 % and 42.6 %. Brevundimonas greatly promoted microalgal biomass growth (maximum chlorophyll-a concentration of 9.4 mg/L), and micro -algae contributed to the increase in the abundance of Dokdonella and Thermomonas in ABS system, thus facili-tating nitrogen removal. The extended Derjaguin-Landau-Verwey-Overbeek theory indicated a repulsive potential barrier of 561.7 KT, while tryptophan-like proteins and tyrosine-like proteins were key extracellular polymeric substances for the formation of flocs by microalgae and activated sludge. These findings provide an in-depth understanding of interaction mechanism between microalgae and activated sludge for the removal of contaminants from wastewater.

Automated summary

In this study, a microalgae-bacteria symbiosis (ABS) system was developed for pollutants removal by co-culturing Chlorella sorokiniana with activated sludge, and the interaction mechanism was investigated. The ABS system achieved almost complete removal of ammonia nitrogen, with removal efficiencies of 65.3% for total nitrogen and 42.6% for total phosphorus. Brevundimonas greatly promoted microalgal biomass growth and microalgae contributed to the increase in the abundance of Dokdonella and Thermomonas, facilitating nitrogen removal. The study also identified key extracellular polymeric substances for the formation of flocs by microalgae and activated sludge.