Global population will reach 10 billion by 2050, threatening food security and fresh water resources due to discharges of organic micropollutants (OMPs). Circular solutions enable efficient resource use, but pose risks due to OMP recirculation. This study presents a membrane-aerated bioreactor (MABR) that enables simultaneous nutrient recovery as microbial protein and OMPs oxidation using aerobic methanotrophs. The MABR treated synthetic secondary effluent spiked with 2 µg/L of several OMPs and influent nitrate and phosphate levels were 51 mgN/L and 11 mgP/L, respectively. Methane was supplied at three C/N ratios (mgCH4/mgN), including 11, 22 and 5.5. Methane and oxygen were supplied through different membranes at an optimal ratio of 40:60 v/v. Solid retention time was 3 days. After reaching steady state, the reactor was operated in batch for 24h to assess OMP degradation kinetics. Microbial protein was analyzed after reaching steady state. Table1 summarizes the results. The MABR removed more than 6.2 mgN/d/L and 1.1 mg-P/d/L, showing good performance as a polishing step for nutrient removal. Higher methane supply rates yielded better biodegradation for all OMPs. Thus, treatment with aerobic methanotrophs can sustain safer water reuse for irrigation. Biomass productivity and methane yields reached levels comparable to conventional fermenters growing the same methanotrophic enrichment using bubbling and explosive atmospheres. Off-gas monitoring found methane levels never were above low explosive limits. Protein content was similar to other studies, with little sensitivity towards methane supply, suggesting that OMP biodegradation can be enhanced without compromising protein accumulation. Furthermore, the protein to N ratio was lowest during the starvation period. Thus, the methanotrophs grown at feast conditions are suited both as good microbial feeds and OMP biodegraders. Given current restrictions, methanotrophs cannot substitute traditional proteins, but instead used as biostimulants. They contain amino acids, e.g. proline, that are plant growth promoters.
