Effect of ozonation on activated sludge from pulp and paper industry

摘要

Aerobic biological treatment with activated sludge is the predominant process all over the worldnfor treatment of pulp and paper industry wastewater. 50–70% of the biodegradable organicnmaterial is oxidized to CO2 and the rest is converted to bacterial biomass, typically termed asnexcess sludge or waste activated sludge (WAS). Handling and disposal of WAS in general and innparticular from the pulp and paper industry face different processing difficulties, regulatorynstringency due to organochlorine contamination and reluctance of people for reuse. With annobjective of reducing the net disposable biomass, ozonation of WAS from a pulp and paper millnand from a laboratory scale batch activated sludge process operated with the wastewater andnbacterial seed of the same pulp and paper mill have been carried out. With the mill sludge havingnpredominant filamentous organisms 18% MLSS was reduced at an ozone dosage of 55mg O3/gndry MLSS solid (DS) resulting in 2.5 times COD increase. With the laboratory sludge which is wellnstructured and flocculating, only 6% MLSS was reduced at an ozone dosage of 55mg O3/g DS.nOzonation mineralizes 26% and 20% AOX compounds embedded in the secondary sludge in thenmill and laboratory sludge respectively at an ozone dosage of 55mg O3/g DS. During ozonation,nabsorbed/adsorbed lignin on biomass was released which resulted in increased colournconcentration. Ozonation can be a potential oxidative pretreatment process for reducing the WASnand paving the way for cost effective overall treatment of WAS.