Effect of nutrient imbalance on performance efficiency of an anaerobic baffled reactor and the production of membrane fouling compounds

ABSTRACT Anaerobic processes effectively treat high-strength wastewater, while membrane-based technologies are attractive post-treatment options for improving effluent quality. A balanced nutrient level (i.e., chemical oxygen demand (COD):N:P = 300:5:1) is required for optimal anaerobic reactor performance. This research investigated the performance efficiency of an anaerobic baffled reactor (ABR) treating low COD:N:P wastewater and its effluent membrane fouling potential. An unbaffled reactor was used as a control. Initially, both reactors showed ≥80% soluble COD (SCOD) removal even at a low COD:N:P of 27:5:3.5. However, after 134 days, the SCOD removal in the unbaffled reactor decreased from 80.7 ± 3 to 48.7 ± 4.6%. In comparison, it took an extra 46 days for the SCOD removal in the ABR to decrease from 87.7 ± 1.7 to 57.8 ± 2.4%. Once an optimal COD:N:P of 300:5:1 was established, the SCOD removal recovered to 88 ± 2.9% in the control and 93 ± 1.2% in the ABR. Concurrently, both reactors’ effluent membrane fouling potential increased with time at a low COD:N:P ratio and decreased at the optimal nutrient ratio. The ABR's volume compartmentation effectively improved the anaerobic biomass's ability to deal with unbalanced nutrient levels during wastewater treatment.