Performance of anaerobic dynamic membrane bioreactor treatment of wastewater from food waste pretreatment: Dissolved organic matter changes and overloading effects

Food waste requires pretreatment before composting due to its high moisture, oil, and salt content. Wastewater from pretreatment (FWPW) has high organic content (COD > 80 g/L) and requires further treatment. The performance and variations in dissolved organic matter (DOM) in an anaerobic dynamic membrane bioreactor (AnDMBR) treating FWPW were investigated along with the impact of the organic loading rate (OLR) of the system. The results showed that, at the stable stage, when the OLR reaches 6.07 kg COD m(- 3) d( -1) , the average COD removal efficiency was 95.3 %, with a methane production of 0.21 L g(- 1) COD removed . The effluent volatile fatty acid concentration was below 560 mg L (-1) and primarily comprised from acetate and propionate. The proportion of DOM with a large (100 -500 kDa) and medium (10 -100 kDa) molecular weight (MW) in the mixed liquor decreased by 7.0 and 5.5 %, respectively, whereas the MW ( > 500 kDa) in the effluent decreased by 14.8 %. The fluorescence spectra revealed only one humic-like peak in the samples, exhibiting a higher fluorescence intensity and humification index in the effluent and mixed liquor than in the influent. At the shock loads stage, the system could withstand a maximum OLR of 11.71 kg COD m( - 3 )d( -1) , and further increases in OLR caused reactor acidification and methane production failure. This study offers new strategies for optimal FWPW treatment and holds promise for guiding the industrial application of AnDMBRs.