Color Removal from Groundwater by Coagulation and Oxidation Processes

The paper concerns experimental research related to the removal of color and permanganate index (CODMn) in the presence of iron and manganese from underground water by means of coagulation and ozonation. The tests were carried out on a laboratory and technical scale in the real underground water treatment system. Ozone, as a strong oxidizing agent, was used to reduce the color intensity and to convert the iron Fe2+ and manganese ions Mn2+ to Fe(OH)3 and MnO2, respectively. In order to optimally remove the color to a value below 15 mg/L, the ozone dose of 3 mg/L was sufficient, which also ensured proper removal of iron and manganese, respectively by 94% and 83%. Ozonation under these conditions, however, did not provide sufficient removal of organic compounds expressed as CODMn below the assumed value of 3 mg/L. The effect of aluminum sulfate and polyaluminum chloride (PAC) was also studied, as a result of which it was found that polyaluminum chloride proved to be more effective reagent. In the technical conditions of water purification at a dose of 16 mg/L coagulant, the efficiency of color removal was 65.2% and CODMn – 50.8%, which ensured adequate values of the tested indicators in purified water below the permissible level.