Color removal from water by coagulation/caustic soda and lime

ABSTRACT

Due to aesthetic aspects, use of colored water even approved hygienically, is not acceptable worldwide. Consumers prefer to use colorless water. Color in water is usually associated with aromatic compounds produced from decay of natural herbal substances. Undesirable taste and odor and disinfection by products are of the reasons of color existence in water. The present study was performed using jar apparatus, lime and NaOH as softener agent and for increasing the pH of the process. Alum and ferric chloride coagulants were used to increase the size of flocs in various pH and color removal from water. It was tried to simulate the conditions of water treatment plants. Coagulant and lime doses, initial color and pH were studied. After the process, the residual color, as well as pH and electrical conductivity of water were measured. The results showed a significant increase in color removal with increasing pH. The highest percentage of color removal was 75% using 40mg/L of alum and ferric. The best efficiency of color removal was 86.68% and 94% by 12[g/L] lime for methylene blue and eriochrome black T, respectively. However, during the procedure, the electrical conductivity of water increased