Mojtaba Ehsanifar - Student Research Committee, School of Health, Iran University of Medical Sciences, Tehran, Iran
Ahmad Jonidi Jafari - Department of Environmental Health Engineering, School of Public Health, Iran University of Medical Sciences, Tehran, Iran
Mehdi Shirzad Siboni - Student Research Committee, School of Health, Iran University of Medical Sciences, Tehran, Iran- Department of Environmental Health Engineering, School of Health, Guilan University of Medical Sciences, Rasht, Iran
Zahra Asadgo - Student Research Committee, School of Health, Iran University of Medical Sciences, Tehran, Iran

Background: Ozonation decays solids and accelerates their consolidation due to strong oxidationcapability; hence, decreasing the problems and expenses of equipment and operating the sludgedigestion and disposal. In this study, we aimed to investigate the effect of separate and combinedeffects of ozone and hydrogen peroxide in reducing contamination volume.Methods: Sludge ozonation was conducted with concentrations of 0.0557 to 0.5573mgO3/mgTSS5573 from 5 to 50 min. Total suspended solids (TSS), volatile solids (VS), chemicaloxygen demand (COD) parameters, soluble COD, and the sludge settleability were investigatedbefore and after the process.Results: The results demonstrated that after 50 min of ozonation and injection of mgO3/mg TSS0.3901 ozone, sludge volume reduction reached 42%. Furthermore, after 50 minutes of ozonation,TSS and VS with a 43% and 48% reduction, reached to 4261mg/l and 3193mg/l, respectively. TotalCOD after 35 min of ozonation decreased 39% from 12524mg/l to 7639mg/l. Also injection of 6mlof hydrogen peroxide (30%) leading to a reduction in TSS and VS by 64 and 65%, respectively,and injection of 4ml of it, resulting in a 58% reduction in COD and 75% in the volume ofsedimented sludge. The effect of the combination of ozone and hydrogen peroxide resulted in thereduction of only 10% of sedimented sludge volume and also reduced removal of COD by 42%.Conclusion: According to the results, ozone and hydrogen peroxide injection to sludge, decreasesludge volume, improve in sedimentation and reduce the pollution load at the level of standards.

Hydrogen Peroxide, Sewage, Waste Water