Chemical Equilibrium Modeling of Fouling Matrix in UV Disinfection

Visual MINTEQ (v. 2.53) was adopted to study the equlibria of potential fouling minerals in UV disinfection applications. Data from fouling experiments included description of water chemistry, including the concentrations of common metal ions and ligands in solution, water temperature, pH, redox potential, hardness, etc. The modeling results were used as a template to identify likely precipitating minerals in the fouling process. Redox effect was examined for the precipitation of iron and manganese.The modeling results suggested that the hydrolytic form of Fe(III) is the dominant mineral that has potential to precipitate due to its oversaturated status. For experiments manganese precipitation appeared likely, the highly-oxidized Mn-containing minerals, such as MnO2, MnPO4, and MnOOH, appeared to have the greatest potential to precipitate. Among these forms, the saturation index of MnO2 was usually the largest.