Enhanced Slow Sand Filtration for the Removal of Micropollutants from Groundwater

Remote areas, where centralized water supply cannot reach, rely heavily on decentralized supply systems such as slow sand filters (SSFs). Groundwater used to be a reliable water source; yet, the advent of micropollutants (MPs) has raised concerns over its quality. In this study, an enhanced slow sand filtration utilizing graphene oxide (GO)-coated sand prepared via a simple thermal method was employed to remove two representative MPs, atrazine (ATZ) and atenolol (ATL), from real groundwater for drinking water treatment. The removal of ATZ and ATL was studied in a bench-scale enhanced SSF using GO-coated sand in comparison with the conventional plain sand. The results showed that the GO-coated sand performed better in the removal of ATZ, ATL, and total organic carbon (TOC), as well as turbidity reduction. Moreover, in order to study the role of the schmutzdecke in MPs' removal small lab-scale columns with and without schmutzdecke growth were set up. The results indicated the enhanced removal capacity of the coated sand toward ATZ, ATL, and TOC could mainly be attributed to the GO coating layer, not the schmutzdecke. Hence, if the coated sand is to be used in field SSFs for the removal of organic contaminants, the schmutzdecke growing phase might not be needed. A preliminary techno-economic analysis was performed to evaluate the practicability of enhanced SSF and GO was found to dominate the overall cost. For a community-level or a household-level SSF, the extra cost using GO-coated sand may be $0.34 and $3.25 per m3 of water if the GO price is $10 and $100 per kg, respectively.