THE TREATMENT OF GROUNDWATER CONTAINING HYDROGEN-SULFIDE USING MICROFILTRATION

Conventional treatment of groundwater that contains gaseous hydrogen sulfide (H2S) has normally utilized air stripping as a means to remove this undesirable contaminant. The use of this treatment technique has several disadvantages which include noxious off-gas discharge, high finished water turbidity levels, increased copper corrosion, and deposition of elemental sulfur in the distribution system. Conventional filtration processes have not been historically applied to treatment of this type of water because of the difficulty in coagulating elemental sulfur. Microfiltration can be used as part of a treatment approach to satisfy the filtration and turbidity removal requirements for this type of groundwater. Microporus membranes range from 0.1 to 1.0 micron in pore size and have a level of retention significantly higher than conventional filtration systems (10 to 100 times) [1]. The mechanism of particle retention using microfiltration is physical instead of a physio-chemical separation as with media filters and therefore, coagulation of the particles is not required. In addition to H2S removal typical air stripping processes do not remove disinfection by-product (DBP) precursors that may be in the groundwater. The use of a coagulant prior to the filter can be used to reduce DBP precursor material and further improve the finished water quality. Microfiltration has been evaluated for reducing H2S from groundwater for the City of Oviedo, Florida. Chlorine oxidation followed by microfiltration successfully removed the H2S by first oxidizing it to elemental sulfur and then removing by filtration. The advantages of this process include lower finished water turbidity levels to improve disinfection efficiencies, elimination of noxious off-gasses, and reduction of sulfur from entering and settling in the distribution system. In addition, a coagulant was added to evaluate to removal of DBP processors to maximize the benefits from providing particle removal with the microfiltration process.