Abstract
Utilization of excess activated sludge as a substrate for production of secondary metabolite is one of the possible measures to solve economical and safe disposal of wastewater sludge. Pretreatment of excess sludge is required to promote the microbial production of metabolite. There are few reports on the disintegration method suitable for activated sludge cake. In the present study, mechanical disintegration methods, such as ultrasonic irradiation, freeze/thaw, and micro-bubble expansion are applied to not only activated sludge slurry but also filtrated and dewatered cakes.
The TOC release efficiencies by ultrasonic were comparable to those by freeze/thaw treatments. The micro-bubble expansion gave less TOC release efficiencies but the energy efficiency was the highest. The effectiveness of micro-bubble expansion was preliminarily verified in the cultivation of Bacillus subtitles on sludge-agar plates with and without the treatment.The TOC releases from filtrated and dewatered cakes by the treatments were also evaluated. The TOC release efficiency decreased with decreasing water content of cake. The micro-bubble expansion and thermal treatments gave higher TOC release from dewatered cake. It can be concluded that micro-bubble expansion is high potentiality as pretreatment of activated sludge cake for production of secondary metabolite with using treated sludge as substrate.
