Aerobic biodegradation of lignosulfonate bearing synthetic wastewater using activated sludge

Lignin comprises a major part of wastewater emanating from paper and pulping industries. Not only that, appreciable amount of lignin has also been noticed in agricultural waste. Strategies involving treatment of lignin "waste" have been mostly carried out under anaerobic environment. The present study concerns the aerobic biodegradation of lignosulfonate using biomass from municipal wastewater sludge. The acclimation of the biomass was best served using synthetic feed comprising sodium lignosulfonate and dextrose-D, which served as a co-substrate. During acclimation of the biomass, inhibition was noticed in the batch where the synthetic feed had lignosulfonate to dextrose ratio of 1.22. However, the bioreactor system managed to overcome this inhibition and stability was restored during the later batches, which were run at higher lignosulfonate to dextrose ratios. Maximum COD (Chemical Oxygen Demand) removal percentage was recorded as 90.6%, whereas the maximum specific COD reduction rate was observed to be 0.0016 h(-1).