Minimization of excess bio-sludge and pollution load in oxic-settling-anaerobic modified activated sludge treatment for tannery wastewater

The operational capability of anoxic and anaerobic upgradations to the conventional activated sludge process was tested. A mainstream oxic-settling-anaerobic configuration coupled to the conventional aerobic activated sludge was demonstrated the first time to elucidate the mechanism of excess sludge disruption and pollution removal from real tannery wastewater feed. The given oxic-settling-anaerobic coupled conventional activated sludge configuration, on the lab scale, was operated in parallel with an anoxic modified conventional activated sludge, and an identical conventional activated sludge reactor. The operational performance with emphasis to sludge yield minimization achieved that corresponds to operational strategies followed for the tested process configurations was compared. The oxic-settling-anaerobic coupled conventional activated sludge configuration confirmed around 51% of bio-sludge reduction, and prominent treated effluent quality compared with parallel run conventional activated sludge, and 21% less volatile accumulation than anoxic modified conventional activated sludge system. Furthermore, oxic-settling-anaerobic coupled conventional activated sludge implementation yields a lucrative reduction of feed pollutants including more than 90% removal of soluble and total chemical oxygen demand, total organic carbon, and ammonia nitrogen. Moreover, oxic-settling-anaerobic coupled conventional activated sludge configuration evidenced outstanding operational sustainability toward feed shock loading of tannery influent. The anoxic modified conventional system, on the contrary, witnessed a comparable removal of total chemical oxygen demand (89.8%), and ammonia nitrogen (91.7%). The present study evidenced the key influence of sludge interchange borne hydrolysis-acidification, energy uncoupling, and maintenance metabolism that further supported by batch anaerobic and aerobic digestion of nitrate, phosphate, sulfate, alkalinity, volatile fatty acids, and sludge pool present in the mixed liquid. Importantly, the experimental sludge yield recorded were processed to perform the simulation, and also modification of the sludge retention time correlation reported in the literature.