Chlorate Residuals

Chlorate is a natural break-down product of sodium hypochlorite and concentrations are higher in older batches of chemical especially if they are exposed to heat or contain metals. RDMW has provided the following information on chlorate monitoring:

Whilst there is no specified guideline value for chlorate in the Australian Drinking Water Quality Guidelines, Queensland Health has set an interim health guideline value of 0.8 mg/L, where a person has been exposed to this or a greater concentration of chlorate, for a period of 12 weeks or more. At present, any drinking water service provider that detects chlorate concentrations meeting these criteria, must report them as an event to RDMW (the Regulator). This reporting is mandatory under condition 2 of a service provider’s information notice for the decision approving their DWQMP, because the service provider should be concerned that chlorate detected in their treated drinking water at ≥0.8 mg/L for 12 weeks or more may adversely impact public health, where they have no preventive measures to reduce this risk.

Processes to manage chlorate concentrations are covered in the Chlorate Fact Sheet and alternatives are discussed in the overview of disinfection methods. Members requiring further information can contact us here.

Relevant Documents

Chlorate Fact Sheet - Release Date 05-Jun-2013: - Chlorate Fact Sheet 2013


Gas or Hypo or Something Else: Disinfection Options for water service providers - Release Date 16-Jul-2018: - Information for water service providers to support management decisions on disinfection options. This discussion paper provides local government decision makers with information to help them make informed choices about disinfection options for their water and sewerage schemes. It addresses the pros and cons of disinfection using chlorine gas, bulk liquid sodium hypochlorite, on-site generated sodium hypochlorite, and solid calcium hypochlorite.