Assessment of full-scale 4th treatment step for micro pollutant removal in Sweden: Sand and GAC filter combo

Abstract

This study focuses on the 4th treatment step in Degeberga WWTP treatment plant, the first full scale GAC filter in Sweden installed in April 2020 for removal of micropollutants. The two GAC filters, containing two different carbon types, has operated flawlessly for three years (30,000 bed volumes) without requiring backwashing. The results indicate that the sand filter provides effective protection to the carbon filters, preventing solids from reaching the carbon and reducing the growth of organic matter. Additionally substantial biodegradation was observed for several substances.During the first year of operation, the two filters (at 8500 and 5700 bed volumes respectively) achieved >98 % removal of 24 substances. By the end of the second year (at 19,000 and 12,600 bed volumes respectively), fluconazole and sulfamethoxazole broke through completely, and the number of compounds below 80 % removal increased. The average removal of micro pollutants decreased over time. Compounds with positive charges generally exhibited higher adsorption capacities, while negatively charged compounds had lower removals. On average the investigated 24 compounds was removed by 89 % in the 4th treatment step over three years. The study suggests that biodegradation may contribute to the removal of some micropollutants in GAC filters, similar to observations made in the sand filter.Both Swiss and suggested EU regulations aim for at least an 80 % removal in micropollutant concentration. The study evaluated the performance of the filters based on this guideline and the presented technique is after a total of eight years of investigation and evaluation a proven performer.Overall, the 4th treatment combination of sand and GAC filters in WWTPs has shown promising results in removing organic micropollutants, addressing the need for efficient treatment strategies targeting these emerging pollutants. Degeberga WWTP serves as an example of successful implementation of advanced treatment for improving water quality and protecting human and aquatic health.