Texas Drinking Water Standards

Texas has strict standards regarding the quality of drinking water.

The quality of water in the state of Texas is regulated by the 30th section of the Texas Administrative Code. Title 30 (as is its formal name) refers to all matters of environmental quality and safety, with Chapter 290 setting the standards for public drinking water. The code's rules cover all issues concerning drinking water's maximum contaminant levels, maximum residual disinfectant levels, as well as water treatment techniques.

Maximum Contaminant Levels

According to Subchapter F of Chapter 290, water contaminants are divided into inorganic compounds (such as arsenic and asbestos), organic compounds (including simazine and

toxaphene), volatile organic contaminants (such as benzene and styrene), radionuclide contaminants and microbial contaminants. For the first three categories, the code lists every single element along with its maximum concentration allowed per liter of water. For radionuclide contaminants, the limit is 5 picoCuries per liter (pCi/L) for combined radium-226 and radium-228, 15 pCi/L for gross alpha particle activity (including radium-226 but excluding radon and uranium) and 30 micrograms per liter (µg/L) for uranium. As for microbial contaminants, Chapter 290.109 states that "maximum contaminant level requirements are based on detection of those contaminants or fecal indicator organisms."

MRDC and MRDL

The minimum residual disinfectant concentration (MRDC) in the water when entering -- and within -- the distribution system is 0.2 milligrams per liter (mg/L) free chlorine or 0.5 mg/L chloramine. The maximum residual disinfectant levels (MRDL) of chlorine dioxide in the water entering the distribution system is 0.8 mg/L. Furthermore, the MRDL of free chlorine or chloramine in the water within the distribution system is 4.0 mg/L based -- as the code suggests -- on a "running annual average."

Water Treatment

A public water system that treats surface water or groundwater under the direct influence of surface water and serves more than 10,000 people must monitor turbidity, E. coli, and Cryptosporidium levels in the raw water at least once each month for a period of not less than 24 consecutive months. Before the water reaches the entry point to the distribution system, the pathogen removal and disinfection processes must achieve at least a 4.0-log (99.99 percent) removal/inactivation of viruses and at least a 3.0-log (99.9 percent) removal/inactivation of Giardia lamblia.

Secondary Standards

The Texas Administrative Code also has a number of secondary standards for public drinking water. These include the concentration of aluminium (0.05 to 0.2 mg/L), chloride (300 mg/L), copper (1.0 mg/L), fluoride (2.0 mg/L), foaming agents (0.5 mg/L), hydrogen sulfide (0.05 mg/L), iron (0.3 mg/L), manganese (0.05 mg/L), silver (0.1 mg/L), sulfate (300 mg/L), total Dissolved Solids (1,000 mg/L) and zinc (5.0 mg/L). Furthermore, the standards include water's pH (more than 7.0), color (15 color units), corrosivity (non-corrosive) and odor (3 Threshold Odor Number).

References

• Texas Administrative Code: Rule §290.104 -- Summary of Maximum Contaminant Levels, Maximum Residual Disinfectant Levels, Treatment Techniques and Action Levels
• Texas Administrative Code: Rule §290.108 -- Radionuclides Other than Radon
• Texas Administrative Code: Rule §290.109 -- Microbial Contaminants
• Texas Administrative Code: Rule §290.111 -- Surface Water Treatment
• Texas Administrative Code: Secondary Standards Figures

Resources

• U.S. Environmental Protection Agency: Texas Drinking Water
• FreeDrinkingWater.com: Log-Reduction Terminology
• Water Opcert School: Threshold Odor Number (TON) Calculations