Abstract:
This research aims at the investigation of dewaterability of municipal sewage sludge by comparing the efficiency of Fentons reagent (Fe²⁺:H₂O₂) with photo-oxidation using ultraviolet radiation combined with hydrogen peroxide (UV/H2O2). The dewaterability of sludge was investigated in terms of its specific resistance to filtration, water content, COD, BOD, and BOD/COD. The potential factors affecting the dewaterability of sludge were, for Fenton process, Fe²⁺/H₂O₂concentration, pH, and reaction time. The concentration of H2O2 was 50% COD by weight and Fe²⁺/H₂O₂ratios were 0.5:1, 1:1 and 2:1. The pH values were 3, 4, 5, and 7, and reaction times were 2, 10, 30, 60, and 120 minutes. For photo-oxidation process, all the factors for Fenton process were applied except hydrogen peroxide concentrations being 25% COD, 50% COD, and 100% COD by weight. The experiment was carried out to explore the effects of relevant factors to the dewatering potential. The results indicated that the optimum condition for sludge dewaterability with Fenton process was at Fe²⁺/H₂O₂concentration of 2:1, pH of 3-5, and reaction time of 10 minutes. The results of photo-oxidation process showed that the optimum condition was achieved at H₂O₂ concentration of 100% COD by weight, pH of 3-5, and reaction time of 30 min. However, at reaction time of 30 minutes, it was found that the dewaterability of sludge was very close to those at 60 and 120 minutes. Compared with Fenton process at the same hydrogen peroxide concentration, it was found that the optimum pH for improving sludge dewaterability was 3-5 for both oxidation processes, whereas the Fenton process was few superior. However, the photo-oxidation tended to be more effective at higher pH values.