Decreased sludge production strategy for domestic wastewater treatment

Abstract

With new EEC regulations, alternative treatment and disposal techniques of the excess sludge produced by Activated Sludge (AS) wastewater treatment plants have to be performed. In order to reduce the excess sludge produced, experiments have been carried out with a Membrane BioReactor (MBR) to study the maintenance and cryptic growth phenomena of Pseudomonas fluorescens culture taken as a model when grown on a limiting substrate complex medium similar to a synthetic urban wastewater. Experiments with various imposed wasting rates showed that viability and sludge production yield decreased when sludge age increased. Same variations were observed on the cell content ratio protein/polysaccharide by analysis of the cell lysis products released after discontinuous thermal treatment. Biomass growth on these cell lysis products was achieved to characterize cryptic growth and its impact on sludge production yield. Finally, a continuous sludge thermal treatment system was operating with MBR to amplify sludge breakage and consequently biomass growth on the lysis products. With the promising results obtained, this work gives a new outlook on the AS process and leads to the development of processes with control and reduction of sludge production.

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.…”

“…The possible explanation of higher sludge production at low temperature is a net accumulation of cell protoplasm within flocs in the form of COD because the hydrolysis of the organisms is the reaction rate-controlling step of the endogenous respiration [49,50]. A side-stream membrane bioreactor (MBR) treating synthetic wastewater by Pseudomonas fluorescens, coupled with a continuous sludge thermal treatment system, was operated for reducing excess sludge production [41]. About 60% of sludge reduction was achieved when the returned sludge passed through a thermal treatment loop (90 C for 3 h).…”

Improving dewaterability of waste activated sludge through advanced oxidization process

“…Sludge treatment and disposal may account for up to 60% of the total operational costs in a wastewater treatment plant (WWTP) (Canales et al, 1994).…”

“…One well-known problem for the process is the high cost associated with the treatment and disposal of waste activated sludge (WAS) produced during the treatment process. Sludge treatment and disposal may account for up to 60% of the total operational costs in a wastewater treatment plant (WWTP) (Canales et al, 1994).…”

“…According to Canales et al (1994), the treatment and disposal of WAS could occupy 60% of the total operating costs for a WWTP.…”