Testing Water Pollution: What's In Your Supply?

Water quality testing is essential to ensure that the water we consume is safe and to monitor progress toward global initiatives such as Sustainable Development Goal 6 (SDG6), which calls for universal and equitable access to safe and affordable drinking water by 2030. The quality of water can be assessed through various methods, including physical characteristics such as colour, odour, taste, and cloudiness, as well as more advanced testing kits and laboratory analyses. Testing for water pollution is crucial as it can adversely affect not only our health but also the economy and society, with contamination often being difficult and costly to clean up.

Testing for bacteria

Testing Methods:

• Presence-Absence (P-A) Tests: These tests use a powdered nutrient mixture added to a water sample, followed by an incubation period of 24 hours to allow any microorganisms to grow. The test then changes colour to indicate the presence or absence of microbial contamination. While these tests are inexpensive, they do not provide quantitative information about bacterial levels.
• Most Probable Number (MPN) Tests: MPN tests are semi-quantitative, meaning they provide an estimate of bacterial concentration. They involve testing multiple samples of water in tubes, bags, or plates, adding a nutrient solution, and counting the number of positive samples after an incubation period. This method is more accurate than P-A tests but requires more time and equipment.
• Membrane Filtration Tests: These are the most quantitatively accurate tests. They involve filtering a water sample through a small, round filter paper, catching all the bacteria present. The filter is then incubated, and the number of bacterial colonies is counted, indicating the concentration of bacteria in the original sample. This method can be more challenging when water samples contain a lot of suspended material.
• Test Strips: Single-use test strips change colour to indicate the concentration of a specific chemical or bacteria in the water. They are simple to use but less accurate, especially if instructions are not followed precisely.
• Colour Disk Kits: These kits are available for a wide range of chemical and bacterial tests. They typically involve adding a reagent to a water sample and then comparing the colour of the sample to a colour gradient on a disk to determine the concentration. Colour disk kits are more accurate than test strips but are also more complicated and costly.
• Hand-held Digital Instruments: Portable digital meters, colorimeters, and photometers provide the most accurate results but are more expensive and delicate. They are useful for field technicians but may not be suitable for citizen science projects.

Indicators of Bacterial Contamination:

• Total Coliform Bacteria: Coliform bacteria are typically found in the digestive systems of people and animals, as well as in soil, plants, and surface water. While they usually do not cause illness, their presence indicates that disease-causing germs may also be present, as they enter the water supply through similar routes (e.g., sewage leaks).
• Fecal Coliform Bacteria: Fecal coliforms, including E. coli, are a specific type of total coliform found in human and animal waste. While most E. coli bacteria are harmless, some strains can cause serious illnesses. Testing for E. coli specifically can indicate fecal contamination of the water supply.
• Nitrates and Phosphates: High levels of these nutrients in water can lead to a process called eutrophication, where excessive plant and algal growth creates ideal conditions for bacterial growth. This reduces oxygen levels in the water, leading to the death of plants and animals. Therefore, testing for nitrates and phosphates is a useful indicator of potential bacterial contamination.

Additional Considerations:

• Water Quality Indicators: Indicators such as pH and total dissolved solids can provide information about the safety of your water. For example, a low or high pH can damage pipes, causing heavy metals like lead to leach into the water.
• Local Guidelines: Contact your local health or environmental department to learn about specific bacteria, chemicals, or contaminants that you should test for based on your geographic location and water source.
• Testing Frequency: It is recommended to test your water supply at least once a year for total coliform bacteria, nitrates, total dissolved solids, and pH levels. However, if you notice any changes in taste, colour, or smell, or if there are known issues with water quality in your area, test your water more frequently.

Testing for nitrates

Nitrates are a common contaminant in water supplies, and they can have harmful effects on human health. Nitrates are especially dangerous for infants, young children, pregnant and nursing mothers, and the elderly. Consuming too much nitrate can affect how blood carries oxygen, causing a condition known as "blue baby syndrome" or methemoglobinemia, which can be fatal. Other potential health impacts of long-term exposure to nitrates include associations with thyroid problems, adverse pregnancy outcomes, and cancers, particularly colorectal cancer. Therefore, testing for nitrates in water supplies is crucial to ensure the safety of drinking water.

There are several methods available for testing nitrates in water. One commonly used method is the water test kit, which can be used by citizens to test the water quality of their local water bodies. These kits typically use test strips or color disk kits that change colour to indicate the concentration of nitrates in the water sample. While these kits are simple and portable, they may be less accurate than laboratory tests, especially if users do not follow the instructions correctly.

Another option for nitrate testing is to use hand-held digital instruments such as digital meters, colorimeters, or photometers. These instruments provide more accurate results than test strips or color disk kits but are more expensive and delicate. They require batteries and calibration and are often used by field technicians or as part of a continuous or remote monitoring network.

For those with private wells, it is essential to regularly test their drinking water for nitrates, as private wells are not regulated by the U.S. Environmental Protection Agency (EPA). The EPA has set a Maximum Contaminant Level (MCL) for nitrate in drinking water at 10 milligrams per liter (parts per million). If nitrate concentrations exceed this level, it is recommended to obtain an alternate water supply or treat the existing well water. Home water treatment options include distillation, reverse osmosis, or ion exchange.

To collect a sample for nitrate analysis, run your cold tap for five to ten minutes, then collect about one cup of water in a clean container. Keep the water cool until you arrive at the testing location. You can submit your sample to a certified water testing lab or your county's Environmental Services or Soil and Water Conservation District (SWCD) for analysis. The cost for nitrate analysis is typically around $20.00.

It is important to test your water supply regularly for nitrates and take appropriate action if elevated levels are detected to protect your health and the health of your community.

Testing for lead

Lead is a toxic metal that can cause irreversible and life-long health effects, especially in children. It is dangerous even at low exposure levels and can accumulate in the body over time. Since you cannot see, taste, or smell lead dissolved in water, testing is the only sure way of telling whether there are harmful quantities of lead in your drinking water.

The first step is to identify the potential sources of lead in your service line and household plumbing. Lead pipes, faucets, and plumbing fixtures are the most common sources of lead in drinking water. Certain pipes that carry drinking water from the source to the home may contain lead. Household plumbing fixtures, welding solder, and pipe fittings made before 1986 may also contain lead. Even homes without lead service lines may still have brass or chrome-plated brass faucets, galvanized iron pipes, or plumbing soldered with lead.

If you suspect that your home may have lead plumbing, you can contact your local water authority or water provider to ask about testing and identifying lead contamination in your tap water. Many public water systems will test drinking water for residents upon request. There are also laboratories certified to test for lead in water. The U.S. EPA recommends sending samples to a certified laboratory for analysis, with testing costs ranging from $15 to $100.

To reduce or eliminate exposure to lead in tap water, individuals can use a "point-of-use" filter certified by an independent testing organization for lead removal. It is also recommended to only drink or cook with water that comes out of the tap cold, as warm or hot water can have higher lead levels. Boiling the water will not reduce lead levels.

Testing for chlorine

Chlorine and Water Treatment

Water treatment facilities commonly use chlorine to disinfect water and eliminate bacteria and harmful organisms. While chlorine is effective in maintaining water quality, excessive chlorine can be harmful if not properly reduced before it reaches consumers. Responsible water treatment dealers are aware of this and take several precautions.

Types of Chlorine

It is important to understand the different forms of chlorine in water. Analytical chemist Ivars Jaunakais explains that there are two main types: free chlorine and chloramines. Free chlorine consists of dissolved chlorine gas, hypochlorous acid, and hypochlorite ions, while chloramines are a combination of chlorine and ammonia. Municipal treatment plants often use chloramination, where chlorine is first added to the water, and then ammonia is added to neutralize the chlorine and form chloramines. This process helps comply with EPA regulations for trihalomethanes (THMs), which are byproducts of chlorination that can be harmful to human health.

Testing Methods

There are two common methods for testing chlorine levels in water: test strips and test kits. Test strips are small, single-use strips that change colour to indicate the concentration of chlorine. Users dip the strip into the water sample and then compare the colour to a chart to determine the chlorine level. Test kits, on the other hand, typically involve adding a reagent to a water sample and then using a colour disk or a digital meter to measure the chlorine concentration. These kits are more accurate but also more complicated and costly.

DPD System

According to Jaunakais, a simple way to distinguish between free chlorine and chloramine compounds and quantify their levels is by using the DPD system. DPD (N,N-diethyl-p-phenylenediamine) reacts instantly with free chlorine compounds to form a red colour. By adding potassium iodide to the DPD solution, it will then react with both chloramine and chlorine. By comparing the free chlorine reaction to the total chlorine reaction, you can determine the level of chloramine in the water.

Breakpoint Chlorination

Breakpoint chlorination is a process used by treatment plants to eliminate chlorine demand compounds. Chlorine is added to the water until all the chlorine-reactive compounds are consumed, resulting in free chlorine residual. This process helps ensure that all contaminants in the water are neutralised.

Health Effects of Chlorine

While chlorine is essential for disinfecting water, prolonged exposure to chlorinated water can have negative health effects. According to Jaunakais, drinking chlorinated water for 20 or more years can increase the risk of bladder cancer. Additionally, consuming high levels of chlorine may lead to the development of asthmatic conditions. Inhaling chloramines can also be harmful, as they can pass through the lungs and elevate chloramine levels in the bloodstream. Therefore, it is crucial to test for chlorine and ensure that it is properly filtered or neutralised before it reaches consumers.

Testing for dissolved solids

Total dissolved solids (TDS) are the amount of organic and inorganic materials, such as metals, minerals, salts, and ions, dissolved in a particular volume of water. TDS are essentially a measure of anything dissolved in water that is not an H2O molecule.

TDS is measured on a quantity scale, either in mg/L or, more commonly, in parts per million (ppm). For instance, if the TDS level is 335 ppm, this means that out of one million parts of H2O, 335 of those parts are something else.

The only truly accurate method of measuring TDS is to evaporate a water sample and weigh the remains with a precision analytical balance. While this is the most reliable method, it is also costly. As a result, TDS meters have been developed as an inexpensive alternative. These are digital or analog meters that measure the electrical conductivity of water. Based on that conductivity, the meter estimates the TDS level.

TDS meters are widely available, easy to use, and provide reasonably accurate results. However, they do not indicate what types of TDS are present, which is the most important information for understanding water quality. Therefore, for a more comprehensive understanding of water quality, a home water test kit or a lab water analysis is recommended.

Frequently asked questions