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Laboratory experiments were carried out to investigate the effect of ultrasound waves on sludge reduction in MBBR bioreactor for industrial wastewater. The experiments were performed using two identical 20L MBBR bioreactor under same operational conditions. In MBBR with return sludge, sludge was collected from clarifier and after being sonicated, returned to the system by pump.
For determining optimum intensity and time duration of ultrasound, 0.3lit of MBBR sludge was sonicated with intensities of 20, 30, 60, 120, 150, 250 w/cm2 and time duration of 5, 10, 15, 20, 30 min. Afterward, these two parameters were optimized with Energy Efficiency Index. As the results shown, intensity of 120... 

Over 90 percent of the wastewater treatment systems use activated sludge which, yields to increase in organic loadings, these systems do not have appropriate performance. For upgrading of these systems a UASB reactor has been used prior to the activated sludge system, to improve the system performance and also reduce the excess sludge production. A membrane was also used instead of the sedimentation tank, to betterment the effluent quality. COD influent concentration was about 600 to 2400 mg/l, up to 98 percent of COD reduction obtain in this system. Also excess sludge reduction was over 90%. Such a system upgrading will increase treatment capacity by factor of 5. As it was shown, for UASBR,...