1. (a) A system that uses a surface water source must provide the disinfection treatment specified in subsection (b) of this section beginning July 1, 1993. A system that uses a groundwater source under the influence of surface water and provides filtration treatment must provide disinfection treatment as specified in subsection (b) of this section by July 1, 1993, or beginning when filtration is installed, whichever is later. Failure to meet any requirement of this section after the applicable date specified in this subsection is a treatment technique violation. Violation of any treatment technique of this section must be reported to the commission by the end of the next business day after the measurement was taken.

2. (b) Each public water system that utilizes surface water or groundwater under the influence of surface water must provide disinfection treatment as follows.

   1. (1) The disinfection treatment must be sufficient to ensure that the total treatment processes of that system achieve at least 99.9% (3-log) inactivation and/or removal of Giardia lamblia cysts and at least 99.99% (4-log) inactivation and/or removal of viruses, as determined by the commission.

      1. (A) The disinfectant concentrations(s) within the treatment process shall not be allowed to fall below acceptable levels for more than four hours.
      2. (B) Disinfection contact time will be based on tracer study data submitted by the system and approved by the commission. Acceptable tracer study data must be submitted to the commission no later than January 1, 1993.
   2. (2) The residual disinfectant concentration in the water entering the distribution system measured as specified in §290.119 of this title (relating to Turbidity and Disinfection) shall not be less than 0.2 mg/liter free chlorine or 0.5 mg/liter chloramine for more than four hours.
   3. (3) The residual disinfectant concentration in the distribution system, as specified in §290.119 of this title (relating to Monitoring Requirements for Systems Using Surface Water Treatment) shall not be less than 0.2 mg/liter free chlorine or less than 0.5 mg/liter chloramine in more than 5.0% of the samples each month, for any two consecutive months that the system serves water to the public.

Source Note:The provisions of this §290.117 adopted to be effective April 15, 1994, 19 TexReg 2282.