Conversion of organic micropollutants with limited bromate formation during the Peroxone process in drinking water treatment

Abstract

Abstract. Advanced oxidation with O3/H2O2 (peroxone) is conducted on pilot plant scale on pre-treated Meuse river water to investigate the conversion of organic micropollutants (OMPs) and the formation of bromate. Fourteen selected model compounds are dosed to the pre-treated river water on a regular basis to assess the efficiency of the peroxone process and to establish the influence of the water matrix. The height of the ozone dose is the main factor in the conversion of the model compounds. The conversion of OMPs can be increased by further increasing the ozone dose, however, the ozone dose is limited concerning the bromate formation. The hydrogen peroxide dosage has only a~minor effect on the conversion, but it limits the bromate formation effectively. In terms of limited chemical consumption, maximal conversion and adherence to the strict Dutch guideline for bromate in drinking water, a practical full-scale setting is 6 mg L−1 hydrogen peroxide and 1.5 mg L−1 ozone. During the investigation period, the average conversion of the model compounds was 78.9%. The conversion of OMPs is higher at higher water temperatures and lower concentrations of DOC and bicarbonate. The bromate formation also is higher at higher water temperature and lower bicarbonate concentration and proportional with the bromide concentration, above a threshold of about 32 μg L−1 bromide, below which no bromate is formed. The peroxone process can be controlled on basis of the (derived) parameters water temperature, bicarbonate and DOC.