Ammonium nitrogen and phosphorus removal by bacterial-algal symbiotic dynamic sponge bioremediation system in micropolluted water: Operational mechanism and transformation pathways.

Construct a bacteria-algae symbiotic dynamic sponge bioremediation system to simultaneously remove multiple pollutants under micro-pollution conditions. The average removal efficiencies of NH-N, PO-P, total nitrogen (TN), and Ca were 98.35, 78.74, 95.64, and 84.92 %, respectively. Comparative studies with Auxenochlorella sp. sponge and bacterial sponge bioremediation system confirmed that NH-N and TN were mainly removed by bacterial heterotrophic nitrification - aerobic denitrification (HN-AD). PO-P was removed by algal assimilation and the generation of Ca(PO) and Ca(PO)OH, and Ca was removed by algal electron transfer formation of precipitates and microbially induced calcium precipitation (MICP) by bacteria. Algae provided an aerobic environment for the bacterial HN-AD process through photosynthesis, while respiration produced CO and adsorbed Ca to promote the formation of calcium precipitates. Immobilization of Ca with microalgae via bacterial MICP helped to lift microalgal photoinhibition. The bioremediation system provides theoretical support for research on micropolluted water treatment while increasing phosphorus recovery pathways.