A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science

Thesis (M.Sc.) - Asian Institute of Technology, 1983

Sludge bulking often occurs in the completely-mixed activated sludge processes treating carbohydrate waste. Hydrogen peroxide was selected as the chemical for sludge bulking control in this study. The effect of hy- drogen peroxide was studied first in the batch study. It was evident that the optimum effective doses of hydrogen peroxide were 40 and 60 g H202/kg MLSS·d at the SVI of 150-300 mt/g and 300-450 mt/g respectively. And it was also observed that after shock loading from 0.3 to 0.5 kg BODS/kg MLSS·d in the batch system SVI increases from 180-200 to 300-450 mt/g. The second doses of hydrogen peroxide of 60 and 70 g H202/kg MLSS·d could reduce the SVI to 150 mt/g in such unit within 3 and 2 days, respectively. While the second doses of hydrogen peroxide of 40 and 50 g H202/kg MLSS·d were needed to overcome sludge bulking within 4 days. For the continuous completely-mixed system study, the organic loading of 0.4-0.5 kg BODS/kg MLSS·d was found to be optimum with no sludge bulking occurred. In this system the effective dose was found to be 60 g H202/kg MLSS·d in both units operated under different SVI values (800-1,100 mi/g and 300-50 mg/i). The frequency of hydrogen peroxide feeding and contact time exhibit the similar effect in both units. The most effective of hydro- gen peroxide feeding and appropriate contact time were found to be single dose and more than 5 hours, respectively.