Chapter 10: Secondary Standards
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- 38929
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)After reading this section, you should be able to:
- Describe the secondary standards
- Outline the secondary contaminants
- Explain physical standards
- Outline levels of violations
Enforcement of Regulations
The National Secondary Drinking Water Regulations control contaminants in drinking water that primarily affect the aesthetic qualities relating to the public acceptance of drinking water. These regulations are called secondary standards. At considerably higher concentrations of these contaminants, health implications may also exist as well as aesthetic (or appearance) degradation. These regulations are not federally enforceable; however, some states have passed laws requiring the state health agency to enforce the regulations.
Secondary Maximum Contaminant Levels
Secondary Maximum Contaminant Levels (SMCLs) apply to public water systems and, in the judgment of the EPA Administrator, are necessary to protect the public welfare or for public acceptance of the drinking water. The SMCL means the maximum permissible level of a contaminant that is delivered to the free-flowing outlet of the ultimate user of a public water system.
Contaminants added to the water under circumstances controlled by the user, except those contaminants resulting from corrosion of piping and plumbing caused by water quality, are excluded by definition. The only exceptions are those resulting from corrosion of piping and plumbing caused by water quality. Currently, 15 secondary standards exist. States may establish higher or lower levels depending on local conditions, providing that public health and welfare are adequately protected.
Aesthetic qualities are important factors in public acceptance and confidence in a public water system. States are encouraged to implement SMCLs so that the public will not be driven to obtain drinking water from potentially lower-quality, higher risk sources. Many states have chosen to enforce Primary and SMCLs to ensure that the consumer is provided with the best quality water available.
Monitoring
In order to monitor, you must collect samples for secondary contaminants at a free-flowing outlet of water being delivered to the consumer. Monitor contaminants in these regulations at least as often as the monitoring performed for inorganic chemical contaminants listed in the Primary Drinking Water Regulations as applicable to community water systems. For surface water systems, the rule means yearly monitoring is required; for groundwater systems, monitor at least once every three years. Collect monthly distribution system physical water quality monitoring samples for color and odors. More frequent monitoring would be appropriate for specific contaminants such as pH, color, odor, or others, under certain circumstances as directed by the state.
Secondary Contaminants
Aluminum
Until relatively recently, most environmental aluminum was found in forms that did not greatly affect humans and other animals. Acid rain, however, has caused a significant increase in aluminum exposure. The average daily intake of aluminum in the general population is about 20 milligrams per day; the SMCL is 0.05 to 0.2 mg/L. Although aluminum is regulated as a secondary contaminant because precipitates of the metal can cause cloudy-looking water, aluminum compounds may also interfere with absorption of fluoride in the gastrointestinal tract and may decrease the absorption of calcium, iron, and cholesterol. Many over-the-counter antacids contain aluminum and use of these products frequently causes constipation, which is thought to be the result of the gastrointestinal effects.
Chloride
The SMCL for chloride is 250 mg/L.
Undesirable Effects
- Objectionable salty taste in water
- Corrosion of the pipes in hot water systems and other pipelines
Studies Concerning the Mineralization Effects of Water Indicate
- Major taste effects are produced by anions (where TDS was studied).
- Chloride produces a taste effect somewhere between the milder sulfate and the stronger carbonate.
- Laxative effects are caused by highly mineralized waters.
Mineralized waters often contain chloride as well as high levels of sodium and magnesium sulfate.
Corrosion Effects
- Studies indicate that corrosion depends on concentration of TDS (TDS may contain 50 percent chloride ions).
- Domestic plumbing, water heaters, and municipal waterworks equipment will deteriorate when high concentrations of chloride ions are present.
Example
Where the TDS = 200 mg/L (Chloride = 100 mg/L), water heater life will range from 10 to 13 years. Water heater life declines uniformly as a function of TDS-1 year shortened life per 200 mg/L additional TDS.
Color
The SMCL for color is 15 color units. The level of this water quality indicator is not known to be a measure of the safety of water. However, high color content may indicate the following:
- High organic chemical contamination
- Inadequate treatment
- High disinfectant demand and the potential for production of excess amounts of DBPs
Color may be caused by:
- Natural color-causing solids such as aromatic, polyhydroxy, methoxy, and carboxylic acids
- Fulvic and humic acid fractions
- Presence of metals such as copper, iron, and manganese
Rapid changes in color levels may provoke more citizen complaints than relatively high, constant color levels.
Copper
The SMCL for copper is 1.0 mg/L. Soft water containing a low level (0.5 mg/L) of copper may cause blue or blue-green staining of porcelain. Higher levels (4 mg/L) of copper will stain clothing and blond hair. When soap is used with water having a copper concentration greater than 1 mg/L, insoluble green curds will form.
Corrosivity
The corrosivity of water indicates the rate at which water causes the gradual decomposition or destruction of a material (such as a metal or cement lining). The severity and type of corrosivity are dependent on the chemical and physical characteristics of the water and the material.
Corrosivity causes materials to deteriorate and go into solution (be carried by the water). Corrosion of toxic metal pipe materials such as lead can create a serious health hazard. Corrosion of iron may produce a flood of unpleasant telephone calls from consumers complaining about rusty water, stained laundry, and bad tastes.
Corrosivity can cause the reduction of the carrying capacity of a water main. This reduced carrying capacity can cause an increase in pump energy costs and may reduce distribution system pressures. Leaks in water mains due to corrosivity may eventually require replacement of a water main.
Fluoride
Fluoride produces two effects, depending on its concentration. At levels of 6 to 8 mg/L, fluoride may cause skeletal fluorosis (the bones become brittle) and stiffening of the joints. For this reason, fluoride has been added to the list of primary standards (having health effects).
At levels of 2 mg/L and greater, fluoride may cause dental fluorosis, which is discoloration and mottling of the teeth, especially in children. EPA has recently reclassified dental fluorosis as a cosmetic effect, raised the primary drinking water standard from 1.4 to 2 mg/L to 4 mg/L, and established a secondary standard of 2 mg/L for fluoride.
Foaming Agents
The SMCL for foaming agents is 0.5 mg/L.
Undesirable Effects
- Causes frothing and foaming, which are associated with contamination (greater than mg/L).
- Imparts an unpleasant taste (oily, fishy, perfume-like) (less than 1.0 mg/L).
Information
- Because no convenient foamability test exists and because surfactants are one major class of substances that cause foaming, this property is determined indirectly by measuring the anionic surfactant (MBAS) concentration in the water.
- Surfactants are synthetic organic chemicals and are the principal ingredient of household detergents.
- The requirement for biodegradability led to the widespread use of linear alkylbenzene sulfonate (LAS), an anionic surfactant.
- Concentrations of anionic surfactants found in drinking waters range from 0 to 2.6 mg/L in well supplies and 0 to 5 mg/L in surface water supplies.
- LAS is essentially odorless. The odor and taste characteristics are likely to arise from the degradation of waste products rather than the detergents.
- If water contains an average concentration of 10 mg/L surfactants, the water is likely to be entirely of wastewater origin.
- From a toxicological standpoint, an MCL of 0.5 mg/L, assuming a daily adult human water intake of 2 liters, would give a safety factor of 15,000.
Iron and Manganese
- Iron and manganese are frequently found together in natural waters and produce similar adverse environmental effects and color problems. Excessive amounts of iron and manganese are usually found in groundwater and in surface water contaminated by industrial waste discharges.
- Before 1962, these elements were covered by a single recommended limit.
- In 1962, the US Public Health Service recommended separate limits for iron and manganese to reflect more accurately the levels at which adverse effects occur for each.
- Each are highly objectionable in large amounts in water supplies for domestic and industrial use.
- Each element imparts color to laundered goods and plumbing fixtures.
- Taste thresholds in drinking water are considerably higher than the levels that produce staining effects.
- Each element is part of the daily nutritional requirements; however, these requirements are not met by the consumption of drinking water.
Iron
The SMCL for iron is 0.3 mg/L.
Undesirable Effects
- At levels greater than 0.05 mg/L some color may develop, staining of fixtures may occur, and precipitates may form.
- The magnitude of the staining effect is directly proportional to the concentration.
- Depending on the sensitivity of taste perception, a bitter, astringent taste can be detected from 0.1 mg/L to 1.0 mg/L.
- Precipitates that are formed create not only color problems but also lead to bacterial growth of slimes and of the iron loving bacteria, Crenothrix, in wells and distribution piping.
Nutritional Requirements
- Daily requirement is 1 to 2 mg; however, intake of larger quantities is required as a result of poor absorption.
- The limited amount of iron permitted in water (because of objectionable taste or staining effects) constitutes only a small fraction of the amount normally consumed and does not have toxicologic (poisonous) significance.
Manganese
The SMCL for manganese is 0.05 mg/L.
Undesirable Effects
- A concentration of more than 0.02 mg/L may cause buildup of coatings in distribution piping.
- If these coatings slough off, they can cause brown blotches in laundry items and black precipitates.
- Manganese imparts a taste to water above 0.15 mg/L.
- The application of chlorine, even at low levels, increases the likelihood of precipitation of manganese at low levels.
- Unless the precipitate is removed, precipitates reaching pipelines will promote bacterial growth.
Toxic Effects
- Toxic effects are reported as a result of inhalation of manganese dust or fumes. Liver cirrhosis has arisen in controlled feeding of rats.
- Neurological effects have been suggested; however, these effects have not been scientifically confirmed.
Nutritional Requirements
- Daily intake of manganese from a normal diet is about 10 mg.
- Manganese is essential for proper nutrition.
- Diets deficient in manganese will interfere with growth, blood and bone formation, and reproduction.
Odor
The SMCL for odor is a Threshold Odor Number (TON) of 3.
Important facts to remember when dealing with odors include:
- Taste and odor go hand-in-hand.
- Absence of taste and odor helps to maintain the consumers’ confidence in the quality of their water, even though it does not guarantee that the water is safe.
- Research indicates that there are only four true taste sensations: sour, sweet, salty, and bitter.
- All other sensations ascribed to the sense of taste are actually odors, even though the sensation is not noticed until the material is taken into the mouth.
- Odor tests are less fatiguing to people than taste tests when testing for tastes and odors.
- Taste and odor tests are useful:
- As a check on the quality of raw10 and treated water
- To help control odor throughout the plant
- Odor is a useful test:
- For determining the effectiveness of different kinds of treatment
- As a means for tracing the source of contaminants
- Hydrogen sulfide is included under the odor SMCL.
pH
The SMCL for pH is defined as pH values beyond the acceptable range from 6.5 to 8.5. A wide range of pH values in drinking water can be tolerated by consumers.
Undesirable Effects
- When the pH increases, the disinfection activity of chlorine falls significantly.
- High pH may cause increased halogen reactions, which produce chloroform and other THMs during chlorination.
- Both excessively high and low pHs may cause increased corrosivity, which can, in turn, create taste problems, staining problems, and significant health hazards.
- Metallic piping in contact with low-pH water will impart a metallic taste.
- If the piping is iron or copper, high pH will cause oxide and carbonate compounds to be deposited, leaving red or green stains on fixtures and laundry.
- At a high pH, drinking water acquires a bitter taste.
- The high degree of mineralization often associated with basic waters results in encrustation of water pipes and water-using appliances.
Silver
Silver is a nonessential element, providing no beneficial effects from its ingestion in trace amounts. Chronic toxicity causes an unsightly blue-gray discoloration of the skin, mucous membranes, and eyes. Apparently, beside cosmetic changes, no physiologic effects are known. Ingestion of trace amounts of silver or silver salts results in its accumulation in the body, particularly the skin and eyes. Some evidence exists that changes to the kidneys, liver, and spleen can occur.
The SMCL for silver is 0.10 mg/L.
Sulfate
The SMCL for sulfate is 250 mg/L.
Undesirable Effects
- Tends to form hard scales in boilers and heat exchangers.
- Causes taste effects.
- Causes a laxative effect. This effect is commonly noted by newcomers or casual or intermittent users of water high in sulfate. Water containing more than 750 mg/L of sulfate usually produces the laxative effect while water with less than 600 mg/L sulfate usually does not. An individual can adjust to sulfate in drinking water.
- Sodium sulfate and magnesium sulfate are more active as laxatives, whereas calcium sulfate is less active.
- When the magnesium sulfate content is 200 mg/L, the most sensitive person will feel the laxative effect; however, magnesium sulfate levels between 500 mg/L and 1,000 mg/L will induce diarrhea in most individuals.
- Tastes may sometimes be detected at 200 mg/L of sulfate, but generally are detected in the range of 300 to 400 mg/L.
Total Dissolved Solids (TDS)
The SMCL for total dissolved solids is 500 mg/L.
Undesirable Effects
- TDS imparts adverse taste effects at greater than 500 mg/L.
- Highly mineralized water influences the deterioration of distribution systems as well as domestic plumbing and appliances (the life of a water heater will decrease one year with each additional 200 mg/L of TDS above a typical 200 mg/L value).
- Mineralization can also cause precipitates to form in boilers and other heating units, sludge in freezing processes, rings on utensils, and precipitates in food being cooked.
- There may be a great difference between a detectable concentration and an objectionable concentration of the neutral salts. Many people can become accustomed to high levels.
- Studies show that the temperature of mineralized waters influences their acceptability to the public.
Zinc
The SMCL for zinc is 5 mg/L.
Undesirable Effects
- High concentrations of zinc produce adverse physiological effects.
- Zinc imparts a bitter, astringent taste that is distinguishable at 4 mg/L. Also, at 4 mg/L a metallic taste will exist.
- Zinc will cause a milky appearance in water at 30 mg/L.
- Zinc may increase lead and cadmium concentrations.
- The activity of several enzymes is dependent on zinc. Enzymes are proteins that catalyze chemical reactions. Zinc is an essential enzyme growth element in terms of nutrition at low doses (zinc must be present) and is toxic to enzymes at high doses.
- Cadmium and lead are common contaminants of zinc used in galvanizing steel pipe.
Physiological Effects
- A concentration of 30 mg/L can cause nausea and fainting.
- Zinc salts act as gastrointestinal irritants. This symptom of illness is acute and transitory.
- The vomiting concentration range is 675 to 2,280 mg/L.
- A wide margin of safety exists between normal food intake and concentrations in water high enough to cause oral toxicity.
Dietary Requirements
- The daily requirement for preschool children is 0.3 mg Zn/ kg of weight.
- Total zinc in an adult human body averages two grams.
- Zinc most likely concentrates in the retina of the eye and in the prostate.
- Zinc deficiency in animals leads to growth retardation.
Key Terms
- Secondary standards – federal and state standards for contaminants that affect the aesthetic qualities relating to the public acceptance of drinking water
- Secondary Maximum Contaminant Level – levels that apply to public water systems and are necessary to protect public welfare or for public acceptance of the drinking water