The literature on reduction of excess sludge production by ozonation is summarized. Two sequencing batch reactor experiments where sludge is ozonated for this purpose are performed. The purpose of these is to evaluate the prospects of using ozonation to reduce excess sludge production in two different kinds of sludge. Urban sewage sludge is used in the first, and paper mill sludge in the second...

The kinetics of sulfate reduction and cell densities of sulfate-reducing bacteria (SRB) were determined in activated sludge at Aalborg East wastewater treatment plant, a modern 100 000 person equivalent plant, where SRB are subjected to alternating cycles of oxic and anoxic conditions. The number of SRB was relatively constant over the year, ranging from 2.1x10(5) to 1.1x10(6) cells ml(-1) as d...

In order to study the performance and mechanisms of excess sludge reduction in the activated sludge that incorporates the Cannibal Process, laboratory activated sludge systems incorporating an anaerobic bioreactor into the sludge recycle stream were operated. In this study, the solids production in the Cannibal system was about 35-40% of the conventional system under steady state conditions. Th...

This work deals with the effect of combined microwave-ultrasonic pretreatment on the anaerobic biodegradability of primary, excess activated and mixed sludge. The characteristics, biodegradability and anaerobic digester performance for untreated primary, excess activated and mixed sludge were compared to combined microwave-ultrasonic pretreated primary, excess activated and mixed sludge. All sl...

in biological wastewater treatment large quantities of sludge are produced. this sludge is highly putrescible.for disposal and safe usage should be stabilized. the anaerobic digestion is a standard technique for stabilization. due to the rate imiting step of sludge hydrolysis, anaerobic degradation is a slow process with high digestion time. due to high retention time and sludge dewatering prob...

The slow degradation rate of sewage sludge in anaerobic digestors is due to the rate limiting step of sludge hydrolysis. The effect of ultrasound pretreatment on sludge degradability was investigated using ultrasound at a frequency of 31 kHz and high acoustic intensities. Ultrasound treatment resulted in raw sludge disintegration as was demonstrated by increase of Chemical Oxygen Demand in the ...

Utilization of sewage sludge on land is an appealing sludge disposal method. The reasons are not just because of the environmental and economic constraints associated with other disposal methods such as incineration and landfilling, but also because the sludge is beneficial both as a soil conditioner and as a fertilizer [1,2]. However, the major limitation with land application of sewage sludge...

A laboratory-scale microwave (MW) unit was applied to treat fresh blackwater sludge that represented fecal sludge (FS) produced at heavily used toilet facilities. The sludge was exposed to MW irradiation at different power levels and for various durations. Variables such as sludge volume and pathogen reduction were observed. The results demonstrated that the MW is a rapid and efficient technolo...

Alternate cycling of sludge in aerobic, anoxic, and anaerobic regimes is a promising strategy that can reduce the sludge yield of conventional activated sludge (CAS) by up to 50% with potentially lower capital and operating cost than physical- and/or chemical-based sludge minimisation techniques. The mechanisms responsible for reducing sludge yield include alterations to cellular metabolism and...