A water test is a set of procedures to determine the quality of water. Several parameters assess water quality for drinking water, groundwater, wastewater, surface water, and others.
Water tests are necessary to guarantee that water is fit for its intended application. For example, drinking water should be free from contaminants that may pose a risk to health or affect the taste or odor. Groundwater and surface water are also tested for contaminants. The main benefit of frequent water testing is to identify unsafe water and ensure that the treatment system is adequate. EPA regulates microbial, organic, and inorganic contaminants in the water.
Health parameters affect human health and include total coliforms, lead, arsenic, and many other microbes, inorganic, and organic compounds. Primary indicators of health risk of contaminated water are coliforms, nitrate, and lead. In addition, pH, alkalinity, chloride, conductivity, corrosivity index, and hardness are commonly determined to assess water quality.
What is the purpose of water testing?
The purpose of water testing is to meet the regulatory requirements. Pollutant-free water is needed to guarantee the health, economic development, and general well-being of people. Groundwater and surface water are used to provide drinking water, so they are tested before and after treatment. Surface water is also tested when used for recreational purposes.
The first scientific water tests in the United States were done around the 1880s when bacteria testing started. In 1867, the albuminoid ammonia test was developed as a means of detecting contamination. A chloride test was applied to river waters in Massachusetts in the 1890s for the detection of contamination.
What are the features of a water test?
Water quality parameters may be classified as physical, chemical, and biological. The features of a water test are listed below:
Physical parameters of a water test:
- Turbidity: Turbidity in drinking water is esthetically unacceptable.
- Color: Organic and inorganic matter imparts color to water.
- Taste and odor: Caused by dissolved organic or inorganic material or dissolved gasses.
- Solids: Can be dissolved or in suspension.
- Electrical conductivity: The ability to conduct electricity. Increases with the concentration of ions.
Chemical parameters of a water test:
- pH: A measure of how acidic/basic a water sample is.
- Acidity: A measure of the amount of acid in the water.
- Alkalinity: A measure of the capacity of water to neutralize acids.
- Chloride: This ion (Cl–) occurs naturally in groundwaters and surface waters.
- Residual Chlorine: Chlorine (Cl2) is added to water for disinfection. Drinking water contains residual chlorine.
- Sulfate: Sulfate ion (SO4-2) occurs naturally in groundwaters and surface waters.
- Nitrogen: The element nitrogen appears in four forms in water: organic, ammonia, nitrite, and nitrate.
- Fluoride ion: A moderate amount in drinking water is considered suitable for dental health.
- Iron and Manganese ions: They impart a bitter taste to drinking water and may precipitate, producing turbidity.
- Copper and Zinc ions: Non-toxic in small concentrations.
- Hardness: Dissolved minerals in water cause problems such as scale deposits in hot water pipes and difficulty producing lather with soap. Calcium and magnesium ions produce the most hardness in-home water.
- Dissolved Oxygen: One of the most important parameters of water quality for surface waters.
- Biochemical Oxygen Demand (BOD): BOD is the demand for oxygen by microorganisms. It is a measure of sewage in the water.
- Chemical Oxygen Demand (COD): COD is a chemical test using a strong oxidizing agent.
- Toxic Inorganic Substances: A significant number of toxic inorganic substances may be found in water in very small or trace amounts. These include arsenic, chromium, and others. However, even in trace amounts, they can be a danger to public health.
- Toxic Organic Substances: There are more than 100 compounds in water that have been listed in the literature and by EPA as toxic organic compounds. These include detergents, solvents, disinfectants, pesticides, and insecticides.
- Radioactive Substances: For drinking water, there exist standards commonly used for alpha particles, beta particles, photons emitters, radium-226 and -228, and uranium.
The Corrosivity index is a measure of the tendency of lime (calcium carbonate) to precipitate. It is calculated from pH, alkalinity, calcium hardness, and conductivity.
Biological parameters of a water test:
- Bacteria: Many dangerous waterborne diseases are caused by bacteria, namely typhoid and paratyphoid fever, leptospirosis, tularemia, shigellosis, and cholera.
- Algae: Create taste and odor problems in the water supply system.
- Viruses: Waterborne viral pathogens are known to cause infectious hepatitis and poliomyelitis.
- Protozoa: Protozoa are single-celled microscopic animals. They form cysts that are difficult to inactivate by disinfection.
Which technologies are used for water testing?
The technologies used for water testing are several. Portable technologies water tests for chemicals include test strips that change color to show the concentration of contaminants, color disks, and hand-held digital meters. Test strips use reagents that change color to show the concentration of individual contaminants. This kind of test kit for home use will check a limited number of contaminants like arsenic, coliform bacteria, E. coli itself, lead, nitrate, and nitrite. Color disk kits use color reagents (like the test strips) and can test a more comprehensive range of chemicals. Hand-held digital meters are portable and are used to test different chemicals. They use various technologies, including optical and electrochemistry.
Laboratory equipment is capable of giving more precise results than portable equipment. Sophisticated techniques are used for water testing in the labs like spectrophotometry for determination of color, atomic absorption spectrometry, flame atomic absorption spectrometry (AAS), inductively coupled plasma (ICP), and others for inorganics, gas chromatography (GC), high-performance liquid chromatography (HPLC), and mass spectrophotometry (MS) for organics.
What are the stages of water testing?
The stages of water testing are listed below:
- Sampling: The collection of samples of water is done in bottles. For analysis of biological contaminants in the water, sterile plastic bottles are used. For chemicals and other determinations, glass or plastic bottles may be used. Some water samples need a preservative. The holding time for water samples varies. Detailed procedures should be followed in every case.
- Bacteriological Analysis: In the bacteriological analysis of water, the number of bacteria colonies is estimated in a culture.
- Physical Analysis: In this stage, the values of the physical parameters of water are determined. These include esthetic parameters like taste, odor, color, and turbidity. These are not generally related to health problems, however, are easily detected and may determine acceptance or rejection of drinking water. Also included are solids (suspended and dissolved) and electrical conductivity.
- Chemical Analysis: The concentrations of inorganics and organics (and other related parameters) are determined by several methods, as indicated above.
How long does a water test take?
Based on the type of the test, a water test may take minutes to days. For example, a coliform test may take 24-48 hr. The kits for do-it-yourself drinking water tests use color tests and portable digital meters. They detect properties like alkalinity, hardness, pH, total chlorine, free chlorine, nitrate, nitrite, sulfate, copper, iron, lead, and zinc. Color tests and portable digital meters used for water testing take a few minutes to give results. Water testing laboratories use more precise technologies for determining water quality and concentrations of other inorganics and organics in water but may take a few days to return the results.
How to Interpret a Water Test Result?
The results of a water test should be checked against acceptable values. The steps of interpretation of a water test results are as follows:
- Check the number of coliform colonies per 100 ml. If the number is 1 or higher, the result is unacceptable, and other bacteria should be checked.
- Check the concentration of nitrate-nitrogen. If the concentration is higher than 10 ppm (mg/L), the result is not acceptable because this is toxic to infants under six months.
- Check the concentration of chloride ions. It has no health standard, but less than 10 ppm is desirable. More than 250 ppm may produce a salty taste.
- Check the pH value. Water with pH 7 is neutral. Below 7 is acidic, and above 7 is alkaline. An ideal range is 6.5-8.5. Below 5.5 and above 9, the water may corrode pipes.
- Check for Total Dissolved Solids. Values above 500 mg/L indicate high amounts of minerals like salts of iron, manganese. It may also mean hardness (that may cause scaly deposits).
What are the common mistakes while interpreting a water test?
The following is a list of common errors committed concerning water tests:
- Not considering underlying issues. For example, bad taste or odor may come from the water source (for example, a well) or the plumbing in your home.
- Not considering the relations between the different parameters. For example, turbidity may suggest the presence of bacteria.
- Not following the instructions when taking the sample.
What is the sample report for water testing?
|Analytical Laboratory Report|
|Client:||Collected by: CEA|
|Task: Analytical Services||Number: AS0000001|
|Date Collected: 08/08/2020||Time: 8:15 a.m.|
|Sample Identification: Kitchen tap||Lab. Number: 000025|
|Total Coliform||12||#/100 ml|
|Hardness (as CaCO3)||320||mg/L|
|Total Dissolved Solids (TDS)||250||mg/L|
|Based on these results, the above sample DOES NOT MEET the EPA standards for drinking water.|
The Total Coliform Bacteria exceeded the max. level of 1 colony/100mL
Which health parameters are used in water testing reports?
The health parameters used in water testing reports include Biological (coliforms, E. coli, and others); Toxic Inorganic Substances (lead, copper, nitrates, cyanides, and many others), and Toxic Organic Substances (includes herbicides, pesticides, and many others).
What are the General Water Quality Indicators?
General water quality indicators (GDWQ) are parameters used to indicate the possible presence of other harmful contaminants. The GDWQ are Coliform bacteria, pH value, and Total Dissolved Solids (TDS).
|General Water Quality Indicators|
|0 colonies/100 mL||Possible bacterial or viral contamination from human sewage or|
|pH value||6.5 to 8.5||pH influences the solubility of contaminants and corrosivity.|
Low pH will cause corrosion of pipes. High pH will give a soda taste.
|Total dissolved solids (TDS)||500 mg/l||High TDS indicates dissolved minerals. It may be related to hardness (scaly deposits) and cause staining or a salty, bitter taste.|
Which contaminants affect the water test results more?
The contaminants that affect the water test results the most are listed below:
- Microorganisms: Bacteria, viruses, and protozoa (such as Giardia lamblia and Cryptosporidium) that are sometimes found in groundwater, surface, and drinking water, can cause serious infections.
- Nitrate: Nitrates are found in fertilizers, manure, and discharge from septic tanks. Rain may carry nitrate into groundwater and surface waters. It is especially dangerous to young children and pregnant women.
- Arsenic: Most arsenic in drinking water comes from rock formations. Groundwater dissolves inorganic arsenic compounds and these may contaminate wells and aquifers. Long-term exposure to low levels of arsenic is linked to cancer, high blood pressure, and nervous system problems.
There is also the Drinking Water Contaminant Candidate List (CCL).CCL is a list of contaminants that are found or anticipated to appear in public water systems while not subject to EPA regulations. The CCL is the first step in evaluating contaminants that may be included in the list of regulated pollutants later.
What is the relation between Home Water Testing Fact Sheet and Water Analysis?
The EPA’s Home Water Testing Facts Sheet gives a detailed explanation of how frequently to test and which Water Analysis you need. Also, the Home Water Testing Fact Sheet provides recommendations about how to collect a water sample for testing.
County Health Departments are authorized to collect and evaluate water samples. Also, laboratories are certified by each State to do water testing. For example, in New Jersey, the Department of Environmental Protection certifies the analytical capabilities of approximately 700 laboratories.
Are water filters produced based on water test results?
Yes, water filters are produced based on water test results since water test results indicate an adequate water filter type. Some examples of such water filters include activated carbon filters that remove organic-based contaminants and some inorganic contaminants like free chlorine and monochloramine from the water. However, activated carbon filters will not remove microbial pollutants such as bacteria and viruses, nor ions like calcium, magnesium, fluoride, or nitrate. Ceramic filters remove bacteria, protozoa, and microbial cysts, but not chemicals or viruses. Reverse osmosis water filters effectively remove ions, but not most organic compounds, bacteria, or dissolved gasses. RO removes beneficial ions together with non-beneficial ions.
Is reverse osmosis better than water softeners for water quality?
Reverse osmosis eliminates a higher range of contaminants than water softeners. However, if the problem is just hardness, water softeners are preferable when compared to reverse osmosis. Water softeners use ion exchange polymers that replace magnesium and calcium (the ions that cause hardness) with sodium. Once exhausted, the sodium ions need to be replaced in the polymer (regeneration). Reverse osmosis is a process that filters water through a membrane under pressure. As a result, contaminants (including those that cause hardness) do not pass through the membrane. Reverse Osmosis vs. Water Softener