Chlorine dioxide in seawater for fouling control and post-disinfection in potable waterworks

摘要

Bio-fouling refers to the undesirable accumulation of a biotic deposit on a surface.This consists of an organic film composed by micro-organisms embedded in a polymeric matrix of their own making.Complex fouling deposits,like those found in industrial environments,often consist of bio-films in intimate association with inorganic particles,corrosion products and macro-fouling organisms.The article focuses on the possibility to minimize the problems related to micro and macro-fouling in once-through cooling systems and desalination plant by shot or continuous injection of chlorine dioxide into the seawater at the intake.A special on line monitoring instrument,installed after chlorine dioxide injection point,permits to check the fouling growth due to marine micro-organism and,in the meantime,the residual of chlorine dioxide. Chlorine dioxide has proved to be an efficient antifouling agent used 1 h/da maintaining residual of C1O_2 in the range of 0.05 to 0.1 mg/L during the dosing shots or 10-12 h/da without any residual at several power station and petrochemical plant in Mediterranean sea,which use seawater both in condenser and evaporators to produce demineralised water.Beside a description of chlorine dioxide chemistry,the article reports 4 power station dosage programmes (one using also river water cooling tower during the summer) and 1 petrochemical plant application.Three different technologies for on site generation of chlorine dioxide have been reported.A full case history selected among the 4 power station is also reported.