Sulfides in natural waters may occur in various species in dependence of pH-value, such as H2S, HS- or S2-. Therefore, treatment strategies for sulfide removal in water-works are different and depend on the water quality. For instance, at pH < 7 domi-nates H2S, which can be removed by stripping. A current German regulation con-cerning air pollution prevention may restrict the application of stripping technologies and require an oxidative sulfide elimination. In this regulation H2S-gas in the exhaust air of the stripper is limited with concentration of 3 mg/m3 or a mass flow of 15 g/h.

A study was conducted to examine the efficiency of ozone, hydrogen peroxide as well as their combination to oxidize sulfide from a deep ground water. In a water-works a 1 m3/h pilot plant was installed. The sulfide concentration of the raw water was 8 mg/l. The pilot plant results showed, that a oxidation of sulfide to concentra-tions < 0.1 mg/l was achieved with 17 mg/l ozone. Under these conditions bromate levels > 5 µg/l were found in the outlet of the pilot plant. The oxidation with 15 mg/l hydrogen peroxide reduced the sulfide concentration to < 0.5 mg/l. The outlet showed hydrogen peroxide concentrations of about 2 mg/l, which exceeds the limit of the German drinking water guideline of 0.1 mg/l.

A stoichiometric dosage of ozone and hydrogen peroxide (7 mg/l ozone and 3 mg/l hydrogen peroxide) yielded to a reduction of sulfide concentration < 0.5 mg/l. Neither bromate nor hydrogen peroxide was detected in the pilot plants effluent. A mass bal-ance showed that right after the oxidation approximately 80 % of the sulfide-sulfur was transferred into sulfate.