Influence of fertilizer draw solution properties on the process performance and microbial community structure in a side-stream anaerobic fertilizer-drawn forward osmosis - ultrafiltration bioreactor

- Flux decline in FDFO was very severe regardless of fertilizer DS.
- Properties of fertilizer DS significantly affected water flux recovery.
- Fertilizer properties considerably affected nutrient accumulation in a bioreactor.
- Nutrient accumulation had a significant impact on biogas production.
- Bacterial and archaeal community structure was varied by nutrient accumulation.

In this study, a side-stream anaerobic fertilizer-drawn forward osmosis (FDFO) and ultrafiltration (UF) membrane bioreactor (MBR) hybrid system was proposed and operated for 55 days. The FDFO performance was first investigated in terms of flux decline with various fertilizers draw solution. Flux decline was very severe with all fertilizers due to the absence of aeration and the sticky property of sludge. Flux recovery by physical cleaning varied significantly amongst tested fertilizers which seriously affected biofouling in FDFO via reverse salt flux (RSF). Besides, RSF had a significant impact on nutrient accumulation in the bioreactor. These results indicated that nutrient accumulation negatively influenced the anaerobic activity. To elucidate these phenomena, bacterial and archaeal community structures were analyzed by pyrosequencing. Results showed that bacterial community structure was affected by fertilizer properties with less impact on archaeal community structure, which resulted in a reduction in biogas production and an increase in nitrogen content.

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