More compact wastewater treatment is attractive for handling increased loads and stricter effluent requirements. The moving bed biofilm reactor (MBBR) can achieve high carbon and nitrogen removal capacity at a small footprint but is challenged to also reach efficient enhanced biological phosphorus removal (EBPR). This pilot study evaluated a new approach to promote EBPR and high nitrogen removal in continuous flow MBBRs by operating with alternating flow direction and intermittent aeration, thus enabling the cyclic anaerobic and aerobic/anoxic conditions required for polyphosphate accumulating organisms (PAOs). The MBBRs utilised a novel bio-based support material with external biofilm growth for improved mass transfer and were fed pre-filtered municipal wastewater. To increase the availability of readily biodegradable carbon for nutrient removal, the influent was supplied with volatile fatty acids (VFA), mimicking fermentation of sludge from primary filtration. The 460-day long study demonstrated stable nitrogen removal and EBPR. The presence of PAOs in the biofilm was demonstrated in batch tests as well as by microbial analysis, with Ca. Phosphoribacter, Tetrasphaera and Ca. Accumulibacter being detected in high relative abundances. Both aerobic and anoxic phosphate uptake were observed, indicating denitrifying PAO activity. The VFA addition had a strong impact on the EBPR, which increased when directing the VFA to the anaerobic phases, compared to dosing VFA continuously. With VFA dosing in the anaerobic phases, nitrogen and phosphorus removal were 84 ± 5% and 68 ± 18%, respectively, demonstrating the possibilities with this novel process for future full-scale installations. • A novel continuous biofilm process with biobased support material for EBPR • Carbon management by primary filtration and VFA addition • Redox-based control of the VFA dosage governed EBPR • High nitrogen removal (84 ± 5%) and enhanced biological phosphorous removal (68 ± 18%) • Ca. Phosphoribacter and Tetrasphaera were the main PAOs in the biofilm.
Ossiansson et al. (Thu,) studied this question.