THE TREATMENT OF GROUNDWATER CONTAINING HYDROGEN-SULFIDE USING MICROFILTRATION

Conventional treatment of groundwater that contains gaseous hydrogen s ulfide (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 fi nished water turbidity levels, increased copper corrosion, and deposit ion of elemental sulfur in the distribution system. Conventional filtr ation processes have not been historically applied to treatment of thi s type of water because of the difficulty in coagulating elemental sul fur. Microfiltration can be used as part of a treatment approach to sa tisfy the filtration and turbidity removal requirements for this type of groundwater. Microporus membranes range from 0.1 to 1.0 micron in p ore size and have a level of retention significantly higher than conve ntional filtration systems (10 to 100 times) [1]. The mechanism of par ticle retention using microfiltration is physical instead of a physio- chemical separation as with media filters and therefore, coagulation o f the particles is not required. In addition to H2S removal typical ai r stripping processes do not remove disinfection by-product (DBP) prec ursors 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 i mprove the finished water quality. Microfiltration has been evaluated for reducing H2S from groundwater for the City of Oviedo, Florida. Chl orine oxidation followed by microfiltration successfully removed the H 2S by first oxidizing it to elemental sulfur and then removing by filt ration. The advantages of this process include lower finished water tu rbidity levels to improve disinfection efficiencies, elimination of no xious off-gasses, and reduction of sulfur from entering and settling i n the distribution system. In addition, a coagulant was added to evalu ate to removal of DBP processors to maximize the benefits from providi ng particle removal with the microfiltration process.