Sludge Reduction and Biological Nutrient Removal by Ultrasound

Sludge produced in wastewater treatment plants (WWTPs) reaches around 1% of the wastewater volume treated whilst the processes for sludge handling and disposal represent from 20 to 60% of operating costs. It is widely recognised that sludge for disposal is one of the most critical issues today for WWTPs operators. The tendency of many countries seems to be aimed towards a biowaste prevention which leads to consideration of different strategies to achieve a reduction of the sludge production. One solution to accomplish such an objective is through the implementation of the Ultrawaves ultrasound (US) technology within the Activated Sludge Process (ASP) to disintegrate the optimum amount of excess sludge and recycling into the aeration tank as new solubilised biomass which is easily biodegraded by the microorganisms. In addition, modern and upgraded WWTPs have to be managed to make Biological Nutrient Removal (BNR) more effective, which commonly overcomes the conventional limitation and increases the need for supplemental electron (e) donors to drive denitrification bio-chemical reactions. Ultrawaves technology also provides with an extremely efficient solution to maximise this process which whenever transforms excess sludge into an autochthonous readily biodegradable carbon source to support the denitrification step. This paper tries to summarise all efforts carried out to investigate excess sludge reduction and nitrogen removal applications from a systemic approach. Some case studies will be obviously mentioned whereas certain microbiological and mathematical descriptions will be unavoidably included.