A novel intermittently aerated membrane bioreactor polished by non-ionic polyacrylamide for dairy farm wastewater treatment: Irrigation water recovery at pilot-scale

To reuse of irrigation water from dairy farm wastewater, a novel pilot-scale membrane bioreactor polished by non-ionic polyacrylamide (NPAM-MBR) was proposed under intermittent aeration (IA). Performances of pollutants removal and anti-fouling were also investigated under different aeration strategies. A nearby 99 % total removal rate of chemical oxygen demand (COD) was obtained. The group at on/off intervals of 15 min/10 min (IA2) could achieve 80 % up to local irrigation standards in COD concentration. An average total nitrogen removal rate of 87 % was obtained, and IA groups performed better than continuous aeration group. Due to the key role in nitrate reduction and denitrification, the enrichment of Burkholderiaceae in IA group led to this result. Total nitrogen removal pathways would be enriched by the formation of anoxic/anaerobic inner layers for larger size particles, and the promotion of simultaneous nitrification and denitrification with the coexistence of aerobic and anoxic zones. The slowest fouling rate occurred at the IA2 group, which was 17.39 %-80 % lower than other groups. Due to the intermittent shear force and disturbance, the particle size of IA2 group was 19.78 %-179.13 % larger than other groups, which led to the decreased filtration resistance. As for extracellular polymeric substances, IA groups were 10.45 %-37.34 % lower over continuous aeration group. The preferential group of IA2 had the lowest cost of 6.35 RMB/m3. This study could provide a novel method for reclaimed irrigation water from dairy farm wastewater at pilot-scale.