Removal of micropollutants using a membrane bioreactor coupled with powdered activated carbon - A statistical analysis approach

Evaluation of micropollutant removal from artificially recharged water using activated carbon

Pilot scale micropollutant removal onto three types of granular activated carbon was tested over a period of 25 months. The columns were operated in a mode as similar as possible to the functioning of the main waterworks with the emphasis on minimizing the washing of the activated carbon layers. Sampling was performed monthly and a total of 222 micropollutants were evaluated. The columns were located at a waterworks in central Bohemia (Czech Republic). Real influent water from the river Jizera after artificial recharge and sand filtration was used. The aim of this study was to verify whether the process of micropollutant removal was suitable under the operating conditions at the waterworks. Clear seasonal patterns of micropollutant concentrations in the influent were detected. All three columns were able to effectively remove or substantially decrease the concentration of most micropollutants. The best performance was shown for the activated carbon Aquasorb 5005, which had the highest surface area and a well developed porous structure with the highest proportion of mesopores. The data were evaluated in order to identify micropollutant parameters important for their removal, and the pH-dependent octanol/water partition coefficient was identified as the key parameter. Other important parameters were charge and polar surface area of the micropollutant molecules.

Study of the Influence of the Wastewater Matrix in the Adsorption of Three Pharmaceuticals by Powdered Activated Carbon

The use of powdered activated carbon (PAC) as an absorbent has become a promising option to upgrade wastewater treatment plants (WWTPs) that were not designed to remove pharmaceuticals. However, PAC adsorption mechanisms are not yet fully understood, especially with regard to the nature of the wastewater. In this study, we tested the adsorption of three pharmaceuticals, namely diclofenac, sulfamethoxazole and trimethoprim, onto PAC under four different water matrices: ultra-pure water, humic acid solution, effluent and mixed liquor from a real WWTP. The adsorption affinity was defined primarily by the pharmaceutical physicochemical properties (charge and hydrophobicity), with better results obtained for trimethoprim, followed by diclofenac and sulfamethoxazole. In ultra-pure water, the results show that all pharmaceuticals followed pseudo-second order kinetics, and they were limited by a boundary layer effect on the surface of the adsorbent. Depending on the water matrix and compound, the PAC capacity and the adsorption process varied accordingly. The higher adsorption capacity was observed for diclofenac and sulfamethoxazole in humic acid solution (Langmuir isotherm, R² > 0.98), whereas better results were obtained for trimethoprim in the WWTP effluent. Adsorption in mixed liquor (Freundlich isotherm, R² > 0.94) was limited, presumably due to its complex nature and the presence of suspended solids.