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Management Technologies for Prevention and Mitigation / Water Treatment Technologies: Pros and Cons: Chlorine/Chloramine/Chlorine Dioxide
Citation:
Lytle, D. Management Technologies for Prevention and Mitigation / Water Treatment Technologies: Pros and Cons: Chlorine/Chloramine/Chlorine Dioxide. Presented at Legionella 2018, Baltimore, MD, May 09 - 11, 2018.
Impact/Purpose:
Preventative and Remediation StrategiesFree Chlorine Added as chlorine gas or sodium (or calcium) hypochlorite (can begenerated on-site)-stored on-siteResults of laboratory and pilot scale studies showed effectivenessat a fairly wide range of dose and water quality conditionsMaintaining a residual of 0.5-1.0 mg/L is important in controllinglegionellaEffectiveness decreases with increasing pHEfficacy increases with increased temperatureBiofilms and inclusion of Legionellain amoeba shield organismsfrom chlorine.Preventative and Remediation. Strategies Monochloramine. Formed from mixing ammonia and chlorine. Normally dosed between 1 and 1.4 mg/L. Monochloramine forms at pH 7.5-9Typically used as a secondary disinfectant to chlorine. Laboratory studies showed wide range of inactivation under varying water quality conditions. Efficacy increases with increased temperature. Several studies concluded chloramine is more effective at penetration of biofilms than chlorine. Potential water quality issues include disinfection byproduct formation (nitrosamines), nitrification, and corrosion. Preventative and Remediation StrategiesChlorine Dioxide Usually generated on-site as needed. Sodium chlorite + hydrochloric acid. Effective over a wide range of pH’s. More effective at penetrating biofilms than chlorine. Dosed at 0.4-0.7 mg/L. Residual of 0.1-0.5 mg/L is important for legionella control. Also effective in controlling taste and odor at the right concentration. Does not form high levels of disinfection byproducts. Potential water quality issues include byproducts of chlorite and chlorate, taste and odor, and damage to polyethylene pipes.
Description:
Presentation to be given at the Legionella 2018 conference in Baltimore.