Ultrafiltration-nanofiltration for removal of hydrogen sulfide, elemental sulfur, and sulfate from a municipal groundwater

The City of Delphos, Ohio implemented a study to determine the most effective method of reducing total dissolved solids (TDS), sulfate, and hardness. A desktop and pilot study determined that dissolved oxygen was oxidizing hydrogen sulfide gas in the wellfield and forming element sulfur manifesting itself via high turbidity levels (>20 NTU). While chemical resolubilization via sodium metabisulfite was able to reduce turbidity by +90%, filtration was still required prior to nanofiltration (NF) to mitigate NF plugging. Zenon ultrafiltration effectively reduced feed water turbidity from over 20 NTU to less than 0.15 NTU. The resulting feed water to the NF system eliminated NF fouling from particle plugging. NF was effective for reducing inorganic ions including hardness and TDS.