Post-treatment of municipal wastewater effluent: effect on organic matter and micropollutant removal

Abstract

Dissolved organic matter and organic micropollutants are still found in municipal wastewater treatment plant effluent up to μg/L levels. Although their concentrations are very low in absolute numbers, they should not be considered negligible as they affect aquatic life in receiving water bodies. This study aimed at assessing the removal of dissolved organic matter and micropollutants in the municipal wastewater treatment plant of Aquafin in Harelbeke by post-treatment methods. The treatment consisted of the ozone oxidation process followed by biological and physical-chemical post-treatment. Three different techniques were used in post-treatment. They included trickling filtration, slow sand filtration and biological granular activated carbon filtration. It was aimed to find out the potential of ozone oxidation influence on post-treatment techniques to eliminate organic pollutants in municipal wastewater effluent. On the other hand, physical-chemical parameters were monitored as well in the purpose to assess the quality of the raw effluent. Among all the post-treatment techniques used, the biological granular activated carbon either alone or in combination with ozonation was found the most effective in removal of organic pollutants with a removal efficiency of higher than 95% in average, but this method is mostly limited in use due to the less cost-effectiveness in view of its capital cost. Therefore slow sand filtration in combination with ozone oxidation was revealed as the optimal technology in terms of removal efficiency (higher than 70% in average) of all targeted compounds and considering the cost-effectiveness. The trickling filtration method combined with ozonation also provided a slight improvement in removal of the majority of the compounds studied. Therefore, a combination of ozonation and biological/physical-chemical filtration process was suggested effective to reduce the majority of targeted pollutants at significant level.