DISINFECTION OF EFFLUENT BY COMBINATIONS OF EQUAL DOSES OF CHLORINE DIOXIDE AND CHLORINE ADDED SIMULTANEOUSLY OVER VARYING CONTACT TIMES

The aim of this research was to investigate the possibility of using a combination of chlorine dioxide and chlorine, instead of using each o f them as a single disinfectant for the disinfection of effluents from municipal sewage treatment plants, in order to obtain an environmenta lly safe source of water which can be reused for a variety of purposes . The main task was to investigate whether the combination of the two disinfectants maintains their advantages and decrease their disadvanta ges. Residual chlorine dioxide, chlorine, chlorite ion and Most Probab le Number (MPN) per 100 ml of survived total coliforms, fecal coliform s, fecal streptococci and E-coliphages were determined as a function o f these disinfectants doses and contact times. The combination produce d a relatively stable high residual of both disinfectants, reduced the concentration of the undesirable chlorite ion, while increasing the c oncentration of chlorine dioxide. In all doses of the combined disinfe ctants there was an improvement in the destruction of the indicator pa thogenic microorganisms.