Screening of the dominant strains in the algae-bacteria symbiotic system and effects of biogas slurry treatment

Bacteria were separated from biogas slurry treated by Chlorella vulgaris, and then the interaction between Chlorella vulgaris and bacteria was explored and the effect of algae-bacteria symbiotic system on biogas slurry treatment was discussed. 5 bacteria were separated by flat-plate separation method and were identified by 16S rDNA sequencing technology. They were highly similar to the following bacteria:Pseudomonas alcaliphila, Exiguobacterium, Bacillus amyloliquefaciens, Bacillus subtilis and Bacillus tequilensis. By measuring changes in chlorophyll a of Chlorella vulgaris, it was found that 5 bacteria could promote the growth of chlorella and the effect of Exiguobacterium was most obvious. These single strain were co-cultured with Chlorella vulgaris separately and the purification effect of algae-bacteria symbiotic system on biogas slurry were investigated. The results showed that the consortium of Pseudomonas alcaliphila and Chlorella vulgaris could reduce TP to 0.391 mg·L-1, and its removal rate was the highest(85%). The consortium of Exiguobacterium and Chlorella vulgaris had the best treatment effect on TN and COD, and the removal rate was 64.4% and 72.3% respectively. The removal rates of COD, TN and TP by pure microalgae or pure axenic bacterium were much lower than that of the above two microalgae and bacteria co-culture systems. To summarize, algae-bacteria symbolic system has better effect on sewage treatment than pure culture system and has a good application prospect in sewage treatment.