TSS BOD REMOVAL EFFICIENCY AND COST COMPARISON OF CHEMICAL AND BIOLOGICAL WASTE-WATER TREATMENT/

Based on standard settling column tests, Jar tests and continuous acti vated sludge laboratory experiments as well as combination of these pr ocesses implemented for a treatment of municipal wastewater with a com position typical for the influent water of Ravda Municipal Wastewater Treatment (MWWT) plant, the removal efficiency obtained in respect of the total suspended solids (TSS) and the biochemical oxygen demand (BO D) was evaluated. The laboratory experiments confirmed the high effici ency of the chemically enhanced mechanical treatment (CEMT) towards TS S and BOD/COD removal. The data obtained show that low dose chemical t reatment in a large range of surface flow rate of precipitation provid es a reduction of TSS and BOD/COD larger than 60% and 50%, respectivel y. Regarding Ravda WWTP as a typical case for the Black Sea coast it w as proved that CEMT is an attractive alternative for retrofitting the existing plants based on the activated sludge process as a secondary t reatment process. CEMT upgrading can be done at much lower cost (pract ically only O&M treatment expenditure is required) compared with an ev entual biological step extension.