Reduction of water chromaticity by materials with capillary properties

Abstract

The presence of a significant amount of plant and animal organic residues in the environment leads to intensive pollution of natural waters and significant deterioration of water chromaticity. Ukrainian regulatory documents on the quality of drinking water establish a level of 20 degrees for water chromaticity. Hence, in most cases, natural water must be additionally treated before consumption. The coagulation, flocculation, filtration and flotation are today the most widespread methods for normalizing the water chromaticity level. All these processes are quite complex and expensive, require the use  of additional reagents and lead to secondary water pollution. The use of materials with capillary properties is a promising method since it simultaneously ensures the liquid phase transport without excess pressure and water cleaning from various pollutants. This method, used to reduce water chromaticity, found that sufficient efficiency could be provided only for the initial water chromaticity level within 20 - 80° CCS and at pH level within 2.0 - 4.0. Under other conditions, all studied tissue samples as a material for capillary filter, such as cotton, linen, polyester and gabardine, did not provide the value of water chromaticity required for drinking water. Even worse results were obtained for water with initial chromaticity more than 80 degrees. Considering that the described method can provide the maximum efficiency only in a highly acidic medium, it is assumed that the surface charge of the capillary filter fibers and humic acid particles could be the critical factor in the reduction of water chromaticity. In a wide pH range, the surface of the humic particles is charged mainly negatively. The surface of cellulose fibers is also negatively charged in the pH range of 2.0 - 11.0. Therefore, the results of experiments can be explained from this point of view. There are no research data in these fields at all. One of the possible ways to improve the efficiency of water chromaticity reduction by the proposed method is to select fabrics with appropriate physicochemical surface properties. Also, capillary filtration process can be treated with special reagents for giving the fiber surface the required charge. Water treatment by series of several connected capillary filters can be a promising way. In general, given the simplicity of the filter design, low total cost of the water treatment process, and zero energy losses, the studied method is quite promising for industrial implementation and needs more detailed research.