Impact of Carbon Sources Application in Enhanced Biological Phosphorous Removal (EBPR) Improvement: A Review

Modern water resource recovery facilities (WRRFs) play a critical role in reducing anthropogenic inputs of phosphorus (P) and nitrogen (N) to aquatic ecosystems, thereby helping to mitigate eutrophication. The enhanced biological phosphorous removal (EBPR) in activated sludge aims to establish a microbial community enriched with active polyphosphate accumulating organisms (PAOs), making it an environmental-friendly and sustainable method for P removal. However, successful application of EBPR relies on both a sufficient supply and appropriate types of organic carbon (C). This review aims to assess the contribution of microorganisms in activated sludge to remove P and discusses efficient C sources that have been used in EBPR. The knowledge gaps within the biological P removal process are evaluated and discussed. Among various organic compounds, acetate and propionate emerge as the most favorable options for achieving stable and efficient P removal by PAOs. However, if these organic compounds are manufactured using fossil fuel-derived materials, their addition will reduce the economic and environmental benefits of EBPR. In comparison, in-line fermentation and side-stream EBPR (S2EBPR) are more advantageous in generating C sources for PAOs by using on-site activated sludge and/or other organic wastes, such as crude glycerol (CG) and food waste (FW). Additionally, future research needs concerning EBPR are discussed to address potential issues related to insufficient C availability in wastewater influent and how microbial competition can be overcome in a sustainable and economical manner.