Minimization of Bio-sludge from Tannery Effluent Using Anoxic Modified Conventional Activated Sludge Process

Excess bio-sludge generation from conventional activated sludge (CAS) for tannery wastewater poses a dominant economical burden of around 60% of the overall operational budget. Previous studies reveal an insignificant bio-sludge reduction from CAS while maintaining desired operating parameters including sludge retention time (SRT) and return activated sludge (RAS). The reason is being referred to higher organic portion present in tannery influent. To overcome the issue of excess sludge production, a lab-scale anoxic MBBR modification to the CAS, as AnM-CAS, has been demonstrated through the present study. As a key control of the implemented AnM-CAS system, the influence of change in SRT and oxidation reduction potencial (ORP) on activated sludge profile were also recorded. The findings of the current study on AnM-CAS signify an overall sludge reduction up to 14% as compared to CAS operated in parallel experiments under identical conditions. The maintenance of effective ORP (-160 +/- 11 mV) and portion of RAS (35-42%) to the AnM-CAS system seems crucial to achieve the given sludge reduction. Furthermore, the trends observed also witnessed a prominent reduction of complex influent pollutants including COD and TSS.