A collaborative effect of solid-phase denitrification and algae on secondary effluent purification

This study explored the collaborative effect on nutrients removal performance and microbial community in solidphase denitrification based bacteria-algae symbiosis system. Three biodegradable carriers (apple wood, poplar wood and corncob) and two algae species (Chlorella vulgaris and Chlorella pyrenoidosa) were selected in these bacteria-algae symbiosis systems. Results demonstrated that corncob as the carrier exhibited the highest average removal efficiencies of total nitrogen (83.7%-85.1%) and phosphorus removal (38.1%-49.1%) in comparison with apple wood (65.8%-71.5%, 25.5%-32.7%) and poplar wood (42.5%-49.1%, 14.2%-20.7%), which was mainly attributed to the highest organics availability of corncob. The addition of Chlorella acquired approximately 3%-5% of promotion rates for nitrated removal among three biodegradable carriers, but only corncob reactor acquired significant promotions by 3%-11% for phosphorous removal. Metagenomics sequencing analysis further indicated that Proteobacteria was the largest phylum in all wood reactors (77.1%-93.3%) and corncob reactor without Chlorella (85.8%), while Chlorobi became the most dominant phylum instead of Proteobacteria (20.5%-41.3%) in the corncob with addition of Chlorella vulgaris (54.5%) and Chlorella pyrenoidosa (76.3%). Thus, the higher organics availability stimulated the growth of algae, and promoted the performance of bacteria-algae symbiosis system based biodegradable carriers.

Automated summary

This study investigated the collaborative effect of bacteria-algae symbiosis on nutrients removal and microbial community in a solid-phase denitrification system. The results showed that corncob as a carrier had the highest removal efficiencies for total nitrogen and phosphorus, attributed to its higher organics availability. The addition of Chlorella algae promoted nitrate removal in all carriers, but only significant promotion in phosphorus removal was observed in the corncob reactor. Metagenomics sequencing analysis revealed the shift in microbial community structure with the addition of Chlorella algae.