An innovative approach to reduce excess sludge production in the activated sludge process

Abstract

A new process has been developed to reduce excess sludge production, in which both excess sludge digestion and wastewater treatment are conducted simultaneously in the same aeration tank. The ozonation enhances biological degradation of the activated sludge, which is decomposed in a subsequent biological treatment. A considerable amount of biomass is mineralized biologically in proportion to the amount of recirculated biomass from the ozonation stage to the biological stage. It was observed that the amount of excess sludge is reduced to nearly zero when 1.2 kg/m3-aeration tank volume of biomass is recirculated in a day from the biological stage to the ozonation stage at a BOD loading of 1.0 kg/m3/d. A biomass concentration of 4200 mg/L was maintained at 1.0 kg-BOD/m3/d without drawing excess sludge for 6 weeks of experimental period under ozone dose of 0.05 g-O3/g-SS and recirculation rate at 0.3 d−1. Only a limited difference in the effluent quality was observed between the new process and the conventional activated sludge process.

Minimization of excess sludge production for biological wastewater treatment

“…But the comparison and evaluation of these processes for sludge lysis is not considered in this paper. Sludge lysis and subsequently cryptic growth could be promoted by physical, chemical and combined ways in order to reduce sludge production, such as ozonation [31][32][33][34][35][36][37][38], chlorination [39,40], integration of thermal/ ultrasonic treatment and membrane [41,42], integration of alkaline and heat treatment [43][44][45], and increase of oxygen concentration [46]. Table 1 summarizes sludge reduction under lysis-cryptic growth condition.…”

“…Yasui and Shibata [31] developed a new process for reducing excess sludge production in the activated sludge process. The process consists of a sludge ozonation stage and a biodegradation stage, in which a fraction of recycled sludge passes through the ozonation unit and then the treated sludge is decomposed in the subsequent biological treatment.…”

“…The operation costs of this process were estimated to be lower than those of conventional sludge treatment process, including sludge dewatering and disposal [32,33]. Different from their continuous ozonation way [31][32][33], Kamiya and Hirotsuji [34] therefore developed a new system combining both biological treatment and intermittent ozonation to reduce the excess sludge production with fewer amounts of ozone and simultaneously control the sludge bulking. Results of their lab-scale experiment treating synthetic sewage indicated that the intermittent ozonation not only reduced sludge production by 50% with only 30% of the ozone dose required for continuous ozonation, and but also improved the sludge settling characteristics.…”

Biological Nitrogen Removal Using the Supernatant of Ozonized Sludge as Extra Carbon Source

“…The sludge reduction rate reported by Bohler and Siegrist (2004) was 46%. In general situation, the sludge is recycled to reactors for further treatment after ozonation (Yasui and Shibata, 1994). In recent years, there are also some experiments carried out to check whether the OS can be used as carbon source for BNR enhancement (Kampasa et al, 2007;Odegaard, 1996a, 1996b).…”

Reduction of Excess Activated Sludge by Ferrite Particles:Methods for Practical Use

“…Several reports regarding cell lysis in order to reduce excess sludge are published including ozonation, milling process with beads, revolving disks methods etc. [2][3][4][5][6][7][8][9][10]. However, the methods are still on the process and a new and effective technology method is still a demand in this new branch.…”