Long-term operation performance and fouling behavior of a high-solid anaerobic membrane bioreactor in treating food waste

•A high methane yield of 0.57 L-CH4/g-VSin was achieved by the AnMBR in treating FW.•Organic pore blocking played the dominant role in membrane fouling at low F/R ratios.•The cake layer governed the fouling when F/R ratio increased. A high-solid anaerobic membrane bioreactor (AnMBR) treating food waste was continuously operated to investigate AnMBR performance and membrane fouling behavior. The optimal methane yield of 0.57 ± 0.08 L-CH4/g-VSin and organic loading rate (OLR) of 6.00 ± 0.59 g-VS/L/d indicated that a high-rate methane fermentation of food waste was achieved by the AnMBR. The resistance-in-series (RIS) model was applied to delineate the resistances of different fouling fractions and elucidate fouling behavior under different filtration modes. The results showed that organic pore blocking was the dominant fouling at the low filtration to relaxation (F/R) ratio, accounting for 60% of the total resistance. By contrast, the cake layer governed the fouling when the F/R ratio became larger, accounting for 54% of the total resistance. To better understand membrane fouling behavior, the characteristics of cake sludge were investigated and compared with those of bulk sludge. Dissolved organic matter (DOM) analysis revealed that soluble microbial by-products played a comparably significant role as aromatic protein in membrane fouling in the high-solid AnMBR. This work provided a deep understanding of the membrane fouling behavior of a high-solid AnMBR in treating food waste and proposed the most appropriate membrane cleaning methods under different filtration modes, which is expected to contribute to the design, operation and further application of the high-solid AnMBR.