DECREASED SLUDGE PRODUCTION STRATEGY FOR DOMESTIC WASTE-WATER TREATMENT

With new EEC regulations, alternative treatment and disposal technique s of the excess sludge produced by Activated Sludge (AS) wastewater tr eatment plants have to be performed. In order to reduce the excess slu dge produced, experiments have been carried out with a Membrane BioRea ctor (MBR) to study the maintenance and cryptic growth phenomena of Ps eudomonas fluorescens culture taken as a model when grown on a limitin g substrate complex medium similar to a synthetic urban wastewater. Ex periments with various imposed wasting rates showed that viability and sludge production yield decreased when sludge age increased. Same var iations were observed on the cell content ratio protein/polysaccharide by analysis of the cell lysis products released after discontinuous t hermal treatment. Biomass growth on these cell lysis products was achi eved to characterize cryptic growth and its impact on sludge productio n yield. Finally, a continuous sludge thermal treatment system was ope rating with MBR to amplify sludge breakage and consequently biomass gr owth on the lysis products. With the promising results obtained, this work gives a new outlook on the AS process and leads to the developmen t of processes with control and reduction of sludge production.