Performance of activated sludge and sequencing batch membrane bioreactor processes for the treatment of crab-processing saline wastewater

Alt text: Graphical abstract illustrating biological treatment of crab-processing wastewater in an SMBR system, from the generation of untreated wastewater to the production of treated effluent, and its final discharge into the marine environment. Crab-processing saline wastewaters have complex characteristics that make them difficult to process without using salt-adapted microorganisms. To the best of our knowledge, this is the first study to comparatively evaluate the performance of continuous stirred tank bioreactor (CSTR) and sequencing batch membrane bioreactor (SMBR) processes employing salt-adapted microorganisms for the biological treatment of crab-processing saline wastewaters. During the operations, increasing organic loading rates (OLRs) affected the activated sludge settleability in CSTR and SMBR fouling. Comparing the performances of activated sludge and SMBR processes, we demonstrated that the SMBR achieved the highest total organic carbon (TOC), total phosphorus, and total Kjeldahl nitrogen (TKN) removal efficiencies (96.77, 92, and 61%, respectively) at an OLR of 186.71 mg TOC L−1 d−1, and a hydraulic retention time of 3 days. However, the CSTR failed to be operated at OLR higher than 166.81 mg TOC L−1 d−1 due to settleability problems. An increase in biomass concentration was also observed in the SMBR system . These findings revealed the feasibility of treating crab-processing saline wastewater, resulting in high quality of treated effluent, which met the discharge requirement and suggesting the construction of an activated sludge coupled to the ultrafiltration system at industrial scale.