Based on standard settling column tests, Jar tests and continuous activated sludge laboratory experiments as well as combination of these processes implemented for a treatment of municipal wastewater with a composition 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 (BOD) was evaluated.

The laboratory experiments confirmed the high efficiency of the chemically enhanced mechanical treatment (CEMT) towards TSS and BOD/COD removal. The data obtained show that low dose chemical treatment in a large range of surface flow rate of precipitation provides a reduction of TSS and BOD/COD larger than 60% and 50%, respectively.

Regarding Ravda WWTP as a typical case for the Black Sea coast it was proved that CEMT is an attractive alternative for retrofitting the existing plants based on the activated sludge process as a secondary treatment process. CEMT upgrading can be done at much lower cost (practically only O&M treatment expenditure is required) compared with an eventual biological step extension.

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