Ozone for the Long Term Surface Water Treatment Rule (LT2ESWTR)

Public drinking water systems will need to start complying with LT2ESWTR if sampling results indicate source waters are at risk for cryptosporidium contamination. The protozoan is capable of causing serious gastrointestinal illness. Compliance generally means additional protective measures including watershed control, source relocation, pretreatment methods, filtration, and pathogen inactivation methods. Chlorination does not control the protozoan at practical application rates.

Systems serving less than 10,000 people will need to comply with the rules by September 2014 and systems serving 10-000 to 50,000 people need to comply by the end of this year. These systems had to already complete two years of monitoring to assess risk.

While there are numerous options for gaining credits to reduce the risk of cryptosporidium entering the distribution system, ozone is one of the pathogen inactivation options. The use of ozone has to be considered in the context of both economics, water quality issues and other source water treatment objectives.

Ozone is often most economical when it is also being used to solve other water treatment objectives and part of a multi barrier approach to water treatment. for example, if ozone is being used for taste and odor control, increasing ozone dose may be an economic option for additional LT2ESWTR credits. It should be noted that in cold water, the amount of ozone required may be high, so the best applications would be in areas where water temperature does not drop significantly.

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