Advancing biological phosphorus removal from carbon-limited potato processing wastewater: enhancing EBPR through organic load optimization

Abstract

Enhanced Biological Phosphorus Removal (EBPR) offers a sustainable alternative to chemical methods for industrial wastewater treatment, addressing a demand in the Belgian potato processing industry. This study develops a fully biological Sequencing Batch Reactor cycle for simultaneous nitrogen and phosphorus removal from the carbon-limited anaerobic digestate (“effluent”), utilizing pre-anaerobic digestate (“influent”) as an internal carbon source. The research was conducted in three testing packages: (I) preliminary batch testing to assess the influent feedwater's suitability as a carbon source, (II) cycle configuration and feeding strategy testing, and (III) carbon dose limiting testing to determine organic loading thresholds. After determining that a split effluent and influent feedwater feeding is necessary to give EBPR the carbon advantage, COD, TN, and TP removal efficiencies of 98.1 %, 98.9 %, and 93 % respectively were achieved. While evaluating organic load dosing through effluent-to-influent feedwater ratios ranging from 2:1 to 4:1, a marked decline in phosphate release and uptake activity was observed after a ratio of 3:1, despite all phases remaining within the TN and TP discharge limits of 15 and 5 mg/L, respectively. Given the inherent fluctuations in wastewater composition throughout the production day, effluent-to-influent feedwater ratios offer a more reliable and adaptive control strategy than COD:N and COD:P ratios. Molecular analysis revealed key microbial communities driving EBPR, including Ca_Accumulibacter, Dechloromonas, and Tetrasphaera. With a focus on practical application and scalability, this study highlights the importance of maintaining suitable carbon-to-nutrient ratios for stable biological nutrient removal performance in complex industrial wastewater treatment.