Investigation of activated sludge characteristics and their influence on simultaneous sludge minimization and nitrogen removal from an advanced biological treatment for tannery wastewater

Abstract The role of extracellular polymeric substances (EPS) in the minimization of the excess sludge yield underlying hybrid activated sludge treatment (as MANODOX system) for tannery wastewater was experimentally elucidated. The operational strategies designed for the MANODOX system configuration and a parallel-run conventional aerobic activated sludge (p-CAS) treatment were tested throughout the study period of 320 days. In comparison with the p-CAS system, MANODOX experimentation received prominently lowered sludge yield (averaged around 0.36 gVSS/gCOD). The experimental observation further affirmed that the sludge generation found influenced by the variation in the sludge characteristics like protein to polysaccharides ratio (ranged around 0.62–0.73), food to microorganism ratio (0.41 ± 0.04), dissolved oxygen (2.23 ± 0.30 mg/L) and bioflocculation ability (71.8–73.8%). Here, MANODOX implementation exhibited three times lowered EPS accumulation and around 70% less sludge generation compared with the p-CAS system. However, the ascertained was positively attributed to the purposeful nourishment of cell-lysis in the MANODOX system. Importantly, the strict maintenance of desired sludge retention time of 23–26 days imposed a profound effect on the aforementioned floc characteristics and EPS degradation. Furthermore, the Fourier transform infrared spectroscopy and specific ultra-violet absorbance analysis reveals, the facultative microbiota had a prominent influence on organic functional groups that presumed to be originated from the disintegration of EPS in the sludge. The corroborated has further been supported by thermogravimetric analysis and batch anaerobic and aerobic digestion test of the volatile sludge pool performed at end of the mainstream operation.