In situ disruption approach on aerobic sludge biomass for excess sludge reduction in tannery effluent treatment plant

• Effect of mechanical disruption on aerobic sludge biomass in effluent treatment.
• In situ excess sludge reduction of 47% was achieved.
• Optimal treatment frequency was 0.5 d−1.
• Mathematical expressions deduced for various parameters.

Excess sludge biomass generation is one of the major problems in effluent treatment plants and it is an unavoidable byproduct generated due to the growth of microorganisms. Moreover, the treatment and disposal of excess sludge costs about 60% of the plant total operating cost. In this work it has been attempted to limit the excess biomass generation during effluent treatment itself, by applying mechanical stress on aerobic sludge biomass. The concept of maintenance metabolism has been implemented in this study to enhance the microbial maintenance requirements along with cell lysis for excess sludge reduction. The experiments have been carried out using identically sequenced continuous reactors with two different hydraulic retention times (HRT), two sludge treatment volumes and three treatment frequencies (TF). Mathematical expressions were deduced to estimate various parameters. Maximum excess sludge reduction of 47% was achieved with treatment frequency of 0.5 and sludge treatment volume of 40%. Further increase in TF resulted in the release of more suspended solids leading to deterioration of the treated effluent. Better COD removal efficiency was achieved with the HRT of 36 h.