pH is a measure of hydrogen ion activity in a solution. pH 7 is neutral, while pH's below 7 are acidic, and those above 7 are basic. TCEQ's standard for pH in Texas water is pH 7 or greater. EPA's pH guideline is 6.5 - 8.5. pH's below 6.5 are corrosive.
Alkalinity is a measure of the capacity of water to neutralize acids. Alkalinity is primarily due to the presence of bicarbonate, carbonate and hydroxide ions. Salts of weak acids may also contribute, such as silicates. Alkalinity acts as a pH buffer and must be considered in selecting the appropriate water treatment process. Alkalinity may also affect water taste.
Total Solids are a measure of matter dissolved in water. It is a general test of water quality, usually reflecting mineral content. Water with a high total solid content may be unpalatable and aesthetically unsuitable for bathing. The effectiveness of soaps and detergents may also be compromised. A limit of 500 mg/L of dissolved solids is desirable for drinking water.
Conductivity measures the ability of an aqueous solution to carry an electrical current. This measurement is a gauge of the concentrations of ions present. It is a general, non-specific measure of mineral content and general water quality. Most safe drinking water in the USA has a conductivity of 50 to 1500 µohms/cm.
Iron may be present in our domestic water due to leaching of natural deposits or iron-bearing industrial waste. Iron is generally more of a nuisance than a health hazard. Iron levels greater than .1 mg/L may result in a bitter taste. High levels also cause the staining of laundry and porcelain.
Silica is the second most abundant element in nature. Silica is added to water as a water conditioner and corrosion inhibitor. Silica can cause problems in industry, forming glassy deposits on tubes of boilers and heat exchangers. Measuring silica in water is useful when efficiency of demineralizers is being monitored, as silica is one of the first impurities detected when the exchange capacity of a demineralizer is exhausted.
Chloride is an element considered essential to the human diet. Chlorides are present in all water supplies, usually as chloride ions. Concentrations of chloride over 250 mg/L may give water a salty taste, but high chloride levels are not known to have any toxic effects on humans. However, high chloride levels may harm metallic pipes and plants.
Chlorine is a chemical disinfectant used in water treatment. It is also used for its bleaching ability and odor control. Fort Worth city water typically reaches its customers with a residual chlorine level of about .5 mg/L. Residual chlorine dissipates over a matter of a few hours.
Chlorine gas is irritating to the respiratory tract and mucous membranes. Its odor is detectable at 3.5 parts per million (ppm). Used in high concentrations during World War I in chemical warfare, chlorine gas is fatal at 1,000 ppm. Carefully used as an additive to our drinking water, chlorine protects us from harmful microorganisms.
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