Application of SAC254 measurement for the assessment of micropollutant removal in the adsorptive treatment stage of a municipal wastewater treatment plant

In 2010, the Mannheim wastewater treatment plant was expanded with an adsorptive treatment stage to remove organic micropollutants (OMPs). Differences in the removal efficiencies of the OMPs investigated were determined over four years of operation by applying different powdered activated carbon (PAC) products and a constant volume-proportional dosing of 10 mg PAC/L. Possible influences on the removal efficiency are discussed here on the basis of the data obtained, exemplified for the analgesic diclofenac. The analyses show that the removal efficiency is influenced significantly by the spectral absorption coefficient (SAC) of the biologically treated wastewater at a wavelength of 254 nm (SAC254). Therefore, in order to ensure the constant treatment performance desired, the dosage of PAC should be adjusted to the measured SAC254 values. Moreover, as the SAC254 reduction correlates with the removal efficiency of OMPs, the additional determination of its reduction allows indirect control of the actual removal performance achieved. The SAC254 reduction can also be used for targeted control of the PAC dosage.