An activated sludge process without excess sludge production

Abstract

An activated sludge process which produces no excess sludge was developed. The process is very simple as a small amount of return sludge is ozonated and then returned to the aeration tank. The ozonation enhances biodegradability of activated sludge, which is biologically oxidized in the aeration tank. A full-scale plant for treating 450m3/d of municipal wastewater was constructed and has been operated successfully for 9 months. The amount of excess sludge eliminated is directly proportional to the amount of ozone dosed to the sludge. At the ozone dosing rate of 0.034 kg/kg-SS, complete elimination of excess sludge has been achieved when 4 times more amount of sludge is ozonated than that of the excess sludge expected in the treatment without ozonation. After 5 months of operation without any withdrawal of excess sludge, small amount of inorganic substances like sand and silt accumulated in the sludge. On the other hand, inert organic substances does not seem to accumulate. As for effluent quality, BOD and nitrogen were kept good. Although effluent SS was 2–15 mg/l higher compared to a control without ozonation, it has been well below the discharge limit.

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.…”

“…Throughout the operation periods of full-scale plants with sludge ozonation process for treating municipal wastewater and industrial wastewater, respectively, no excess sludge was withdrawn and no significant accumulation of inorganic solids occurred in the aeration tank at optimal ozone dose rates. 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.…”

“…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.…”

Modelling of sludge discharge based on PSO-RVM

“…model by removing irrelevant points from the structure of prior parameters under the framework of Bayesian. Compared with support vector machine (SVM), relevance vector machine(RVM) has the following advantages: (1) subjective setting error parameters is avoided; (2) the relevant vector is less than the SVM; (3) kernel function need not meet the Mercer condition, resulting in a greater range of options 7 . For a given data set { }…”

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

“…The utilization of ozone to reduce excess sludge has drawn wide attention (Liu and Tay, 2001). Sakai et al (1997) carried out a full-scale experiment on ozonation of the sludge and found that excess sludge was reduced by 66%. The sludge reduction rate reported by Bohler and Siegrist (2004) was 46%.…”