Use of chlorine dioxide and ozone for control of disinfection by-products in water supplies
AssigneeContra Costa Water District
InventorsDale Darrow Newkirk, Xuejun Zhou, Jeffrey John Neemann
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Abstract
A method of oxidation or pathogen inactivation in water supplies using the combination of treatments of chlorine dioxide and ozone in the sequential steps prior to filtration and distribution. Results indicate that the addition of chlorine dioxide before prezonation reduces the bromate formation and chlorine dioxide can be substituted for preoxidation with ozone, while maintaining the enhanced filtration effects observed from the presence of a preoxidant. A majority of the chlorite formed from reactions of chlorine dioxide with constituents in raw water are converted to chlorate by the following ozonation step.
Claims7
Method of oxidation or pathogen inactivation in a water supply system using chlorine dioxide and ozone to reduce bromate formation comprising the steps of
- 1) pretreatment of the water supply with chlorine dioxide;
- 2) ozone treatment in the pre-ozone contactor;
- 3) passing the treated water through a flocculation basin followed by a filter bed;
- 4) disinfecting the filtered water by passing through a post-ozone contactor prior to distribution.
Process for the control of the formation of bromate during ozonation of bromide containing water wherein:
- 1) chlorine dioxide is introduced into said bromide containing water
- 2) ozone is introduced into the water for a period of time and
- 3) sufficient ozone to produce oxidation, sterilization and pathogen inactivation.
Process for the control of the formation of bromate during ozonation of bromide containing water to produce oxidation, sterilization and pathogen inactivation wherein:
- 1) chlorine dioxide is introduced into said bromide containing water prior to ozone introduction;
- 2) ozone is introduced into the water following the chlorine dioxide introduction in a pre-ozone contactor;
- followed by passage through alum and granular activated carbon filters and
- 3) introduction of additional ozone in a post-ozone contactor prior to distribution.
Dependencies are inferred from the claim text.