Assessment of Fenton Process as a Minimization Technique for Biological Sludge: Effects on Anaerobic Sludge Bioprocessing

Sludge minimization is becoming a more important issue in sludge treatment for many reasons regarding the improved processing of sludge, transportation, and landfilling. Many techniques on sludge minimization have been developed recently. Among these techniques, advanced oxidation processes have taken place as efficient methods in the area of sludge minimization. To determine the effects of the oxidative treatment on anaerobic sludge digestion for sludge minimization purpose, the Fenton process was used in this study. This process was applied to biological sludge samples preceding anaerobic sludge digestion. The samples were taken from a municipal wastewater treatment plant located in Izmir, Turkey. Sludge digestion studies were carried out using six 8.5 L lab-scale anaerobic reactors. Three of them were operated as control reactors without Fenton's application, while the others were fed with Fenton processed sludge. The reactors were operated in mesophilic conditions for 30 days of operation period. Two reactors were operated as batch, while the others were operated as semi batch system. Two different sludge retention times as 5 and 10 days were applied during the operation. A ratio of 0.067 gram Fe(II) per gram H2O2, and 60 g H2O2/kg Dried Soil were chosen as a result of an optimization study on Fenton processing of sludge. Experimental results showed higher volatile solids reductions and higher biogas productions for the digesters fed with Fenton processed sludge as positive effect of Fenton's application on anaerobic sludge biodegradability. Significant reductions in protein concentrations indicating the effective floc disintegration were also obtained in Fenton processed digesters compared to the control reactors. These results were also consistent with the particle size distribution results. On the other hand, the Fenton process led to decrease in the biosolids' resistance to dewatering in terms of capillary suction time (CST), but did not have a positive effect on sludge dewatering performance on a belt press simulation