Résumé
The excess sludge treatment and sludge disposal are major factors to the over-all economy of wastewater treatment plants [WWTP]. The ideal solution to the problem of sludge disposal is to combine sludge minimization with contamination removal at the source. In this study, the effect of ozonation, chlorination and 3,3,4,5-tetrachlorosalicylanilide [TCS] to treat part of the return activated sludge flow with the intention of reducing the overall plant yield in a conventional activated sludge pilot, were investigated in a side-stream pilot reactor. It was found that in the case of ozonation 8% g O[3]/g MLSS, and in the case of chlorination 2% g Cl[2]/g MLSS produce the best results. In the utilization of TCS method, the excess sludge production was reduced by 80% per day at a TCS dose of 1% g TCS/g MLSS. In all the above experiments a reduction in the volume of the excess sludge was achieved, while the efficiency of removal chemical oxygen demand [COD] from the reactor without the use of those methods was not significantly different