MICROBIOLOGICAL TREATMENT PROGRAMS FOR COOLING WATER PRESENTER H.M.ASIF MANAGEMENT ASSOCIATE OPERATIONS UTILITIES

OBJECTIVE To compare various microbiological treatment programs and select the best for our cooling water system.

CONTENTS Cooling water system Cooling water problems Treatment for Microbiological growth Microbiological growth Cooling water problems Cooling water system

COOLING WATER SYSTEM Once Through System Open Recirculating System Closed Recirculating System

COOLING WATER PROBLEMS Scaling Fouling Corrosion Microbial Growth

MICROBIOLOGICAL GROWTH Types of Microorganisms In Cooling Water Bacteria Aerobic Anaerobic Algae Green Algae Blue Green Algae Fungi Molds Yeasts

MICROBIOLOGICAL GROWTH MECHANISMS Binary Fission Budding Tip Extension

MICROBIOLOGICAL GROWTH CONDITIONS Nutrients Sun Light Temperature Conditions pH Conditions

PROBLEMS BY MICROBIOLOGICAL GROWTH Formation of Biofilms Microbiological Induced Corrosion (MIC) Biofilms on heat exchange surfaces act as insulating barriers. Heat exchanger performance begins to deteriorate as soon as biofilm thickness exceeds that of the laminar flow region.

MICROBIOLOGICAL TREATMENT Oxidizing Biocides Ozone Chlorine Dioxide Chlorine Bromine Monochloramines Non oxidizing biocides Isothiazoline Carbamates Quaternary amines

CHLORINATION Adding chlorine gas to water Cl2 + H2O HOCl + HCl Chlorine Hypochlorous Acid Hydrochloric Acid Adding sodium hypochlorite to water NaOCl + H2O HOCl + NaOH Sodium Hypochlorite Hypochlorous Acid Sodium Hydroxide Limitations of Chlorination - It has high demand - Increase in chlorides concentration - Reduced efficiency at high pH values

BROMINATION Sodium bromide reacts with hypochlorous acid NaBr + HOCl HOBr + NaCl Sodium Bromide Hypochlorous Acid Hypobromous Acid Benefits of Bromination over Chlorination. - Better effectiveness at high pH than chlorine Limitations of Bromination - Use with parallel of chlorine - Increase in chlorides concentration

MONOCHLORAMINES Formation of Monochloramine: HOCl + NH3 NH2Cl + H2O Characteristics of monochloramines - It has Low demand - Not affected by suspended solids and organic compounds - Excellent biofilm penetration and removal - Effective at wide range of pH - Effective up to and above temperature of 60 ºC

ADVANTAGES OF MONOCHLORAMINES Elimination of Chlorine Reduction of Sodium Hypochlorite consumption Chlorides reduction Blow down reduction Reduction in Bulab chemical consumption

DISADVANTAGES OF MONOCHLORAMINES The only disadvantage of Monochloramines is the formation of Dichloramines and Trichloramines. NH2Cl + HOCl NHCl2 + H2O NHCl2 + HOCl NCl3 + H2O

CHLORINE VS BROMINE VS MONOCHLORMINES

CHLORINE VERSUS MONOCHLORAMINE DEMAND Residual free chlorine Residual MCA Biological matter Bacteria, Living matter Reaction with MONOCHLORAMINE Reaction with HALO-OXIDANTS Chlorine, Brimine Example on cooling water: Chlorine demand: 6.0 ppm MCA demand: 0.3 ppm Organic matter Carbon Compounds Inorganic matter S,N compounds S N

COST COMPARISON FOR Cl2, NaBr & MONOCHLORAMINES

CONCLUSION From the comparison we can say that Monochloramines system is a better choice for the microbiological treatment as: “It is a more efficient and more economical system”

Questions are Welcome ???