P7.1.2.7 Many of the causes FAC. FAC Take steps and preventative concentration is noted in Chlorine measures in more than 50% overdose at a P7.1.2.1–P7.1.2.6 for of its MAV. as chlorine chlorination at the appropriate. booster treatment plant are station. Adjust dose also applicable to setting. chlorine boosting in the distribution system. Refer to these. Put in place either manual monitoring or in-line monitoring of the FAC residual to provide reliable control of the booster dose rate. Event: EXCESSIVE FORMATION OF CHLORINATION BY-PRODUCTS Possible hazards: Trihalomethanes, haloacetic acids, chloral hydrate and chlorate (hypochlorite chlorination). Level of risk: Low–moderate3 P7.1.3.1 Provision of treatment TOC/colour. Elevated TOC or Optimise processes upstream colour. treatment Natural to reduce levels of parameters organic matter Elevated organic matter in the in upstream present in the disinfection processes to water being maximise chlorinated. formation. organic matter removal. 3 The concentrations of disinfection by-products formed, and therefore the risk they present, will depend on the amount of natural organic matter in the water. Contingency Plans If an event happens despite preventive and corrective actions you have taken, you may need to consult with the Medical Officer of Health to assess how serious a problem is. FAC concentration is lower than minimum acceptable level – A detectable chlorine residual cannot be obtained in the Indicators: leaving the treatment plant. In 100 ml samples of water leaving the treatment plant, or E. coli coliforms are continually detectable, or is present at elevated levels (more than 10 per 100 mL). Widespread illness in the community.
P7.1.2.7 Chlorine overdose at a chlorine booster station. Many of the causes and preventative measures in P7.1.2.1–P7.1.2.6 for chlorination at the treatment plant are also applicable to chlorine boosting in the distribution system. Refer to these. Put in place either manual monitoring or in-line monitoring of the FAC residual to provide reliable control of the booster dose rate. FAC. FAC concentration is more than 50% of its MAV. Take steps noted in as appropriate. Adjust dose setting. Event: EXCESSIVE FORMATION OF CHLORINATION BY-PRODUCTS Possible hazards: Trihalomethanes, haloacetic acids, chloral hydrate and chlorate (hypochlorite chlorination). Level of risk: Low–moderate3 P7.1.3.1 Natural organic matter present in the water being chlorinated. Provision of treatment processes upstream to reduce levels of organic matter in the TOC/colour. Elevated TOC or colour. Elevated disinfection formation. Optimise treatment parameters in upstream processes to maximise organic matter removal. 3 The concentrations of disinfection by-products formed, and therefore the risk they present, will depend on the amount of natural organic matter in the water. Contingency Plans If an event happens despite preventive and corrective actions you have taken, you may need to consult with the Medical Officer of Health to assess how serious a problem is. – FAC concentration is lower than minimum acceptable level Indicators: A detectable chlorine residual cannot be obtained in the leaving the treatment plant. In 100 ml samples of water leaving the treatment plant, E. coli or coliforms are continually detectable, or is present at elevated levels (more than 10 per 100 mL). Widespread illness in the community.
treatment-chlorination-feb14-v2.docx