Color Removal from Groundwater by Coagulation and Oxidation Processes

The paper concerns the experimental research related to the removal of color and permanganate index (COD_Mn) in the presence of iron and manganese from the 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 the proper removal of iron and manganese, by 94% and 83%, respectively. However, ozonation conducted under these conditions, did not provide sufficient removal of organic compounds expressed as COD_Mn 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. Under the technical conditions of water purification at a dose of 16 mg/L coagulant, the efficiency of color removal was 65.2% and COD_Mn – 50.8%, which ensured that the values of the tested indicators in the purified water were maintained below the permissible level.