Influence of illumination strategy in anaerobic stage on the performance of bacterial-algal symbiosis system in A/O mode
In order to investigate the effects of different illumination strategies in the anaerobic stage on the bacterial-algal symbiotic system,four groups of sequence batch reactors(SBR)were set up to operate in an anaerobic/aerobic(A/O)mode,in which the anaerobic stage of R1 was illuminated with 80001x;R2,R3 and R4 divided the anaerobic stage into A1 and A2.There is no illumination in the Aistage,and the illumination intensity in the A2stage respectively are 0,3000,50001x.The results of this research revealed that R3 and R4 with weak illumination added at the late anaerobic stage could rapidly enriched the microalgae,which led to the formative bacterial-algal symbiotic granular with dense structure,good settling performance,better carbon,nitrogen and phosphorus removal,and the secretion of more extracellular polymers(EPS).Among them,R3 had the best effect of phosphorus removal,and the removal rate of total phosphorus(TP)reached 95.87％.According to the analysis of typical cycle,the phosphorus release at the end of anaerobic stage was proportional to the chlorophyll a(Chl-a)content under weak illumination condition;the ability of R3 to release phosphorus is the strongest,and its phosphorus concentration at the end of anaerobic stage reaching 43.73mg/L;the high-phosphorus environment formed in the A2 stage was able to stimulate the growth of microalgae,and its Chl-a content reached 6.13mg/gVSS at the late stage of the operation.High-throughput sequencing showed that the prokaryotic of R3 were successfully enriched phosphorus accumulating bacteria(PAOs)centered on Candidatus Accumulibacter with an abundance of 11.18％;the total abundance of microalgae in the eukaryotes reached 84.29％,of which the abundance of Halochlorella was as high as 42.85％,suggesting that the addition of weak illumination(30001x)to the high-phosphorus environment in the late anaerobic stage could stimulate the growth of microalgae without affecting the growth of the PAOs,thus form a symbiotic granular with microalgae and PAOs as the core,which provides technical support for the deep treatment of wastewater.
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