Testing Water Pollution: Methods And Techniques

Water pollution is a serious issue that can have detrimental effects on human health and the environment. It is caused by a variety of factors, including human activities such as industrial waste, agricultural practices, and sewage, as well as natural factors like weather and climate change. With the deteriorating quality of water worldwide, it is crucial to test for water pollution to ensure safe and sustainable access to this precious resource. Testing for water pollution can be done through various methods, ranging from simple visual inspections to advanced chemical analyses. Some common testing methods include assessing physical characteristics such as colour, odour, taste, and cloudiness, as well as measuring temperature and turbidity. More comprehensive testing can be done through certified labs, which offer accurate assessments of specific contaminants like lead, PFAS, and other harmful substances.

Testing for E. coli bacteria

Water quality monitoring is essential to ensure access to safe drinking water. When it comes to testing for E. coli bacteria in water, there are various methods available, ranging from simple, low-cost techniques to more advanced molecular testing devices. Here is an overview of some common approaches:

Visual and Sensory Inspection

A basic and low-tech method is to assess the water's appearance, odor, taste, and cloudiness. While this approach is imperfect and unreliable, it can provide a preliminary indication of potential issues. Cloudy or turbid water, for instance, may suggest the presence of suspended particles or contaminants. A simple tool like a turbidity tube can be used to measure cloudiness by observing the water's clarity as it fills the tube.

Temperature Measurement

Water temperature plays a crucial role in microbial activity, dissolved oxygen levels, and ecosystem function. A standard thermometer can be used to measure water temperature, and modern probes for water quality monitoring often include temperature sensors.

Conventional Laboratory Assays

Traditional methods for detecting E. coli and other pathogens in water involve culture-based techniques and separation/filtration processes in laboratories. While these assays are known for their accuracy and sensitivity, they require expensive equipment, skilled personnel, and a significant amount of time for results. The IDEXX Colilert system, for example, can quantify the number of total coliform and E. coli in a single test but needs bulky equipment like an incubator and has a long turnaround time of 24 hours.

Molecular Testing Devices

There is a growing trend towards developing small, easy-to-use, and cost-effective molecular testing devices for on-site detection of E. coli. These devices offer rapid results, enabling immediate actions to prevent the spread of waterborne diseases. One innovative platform integrates paper-based sample preparation with nucleic acid isothermal amplification, followed by loop-mediated isothermal amplification (LAMP) and colorimetric detection. This method can detect multiple E. coli strains in environmental water samples within about an hour, providing a more efficient and accessible solution for water quality monitoring.

Nitrate and phosphate levels

Nitrogen test strips are a convenient, inexpensive, and relatively accurate way to test nitrate levels in water. These strips can measure nitrate levels from 1 to 50 parts per million (ppm) and nitrite levels from 0.15 to 3.0 ppm. If nitrate levels are above 10 ppm, the water is unsafe for drinking. While there are no standards regarding nitrate levels and aquatic life, high nitrate levels can be serious. Although nitrate is not toxic to plants or animals, it can become toxic during digestion if it is converted to nitrite, which prevents blood from carrying oxygen.

Nitrogen test kits can also be used to detect inorganic forms of nitrogen readily available to plants, such as nitrate (NO3-), nitrite (NO2-), and ammonium (NH3). These kits are portable, versatile, and cheaper than laboratory spectrophotometers.

Nitrate levels can also be measured using a nitrate electrode and meter, which is more expensive than the field kits. The electrode measures nitrate activity in the water, which affects the electric potential of a solution in the probe. The meter then converts the electric signal to a scale that is read in millivolts. The millivolts are then converted to mg/L of nitrate.

Phosphate levels can be controlled by adding a refugium with macro-algae to an aquarium. The plants use phosphate to grow, removing it from the water. Phosphate can also be removed using a media reactor and Granular Ferric Oxide (GFO).

Industrial and household contaminants

Industrial activities and household contaminants are major sources of water pollution. Industrial units release large amounts of gases and heavy elements, such as sodium bicarbonate, iron, zinc, carbon dioxide, sulfate, chloride, and fluoride, which can be fatal to human health. Additionally, agricultural activities contribute to water contamination as chemicals such as fertilizers and pesticides can leach into groundwater.

Household contaminants can also affect water quality. For instance, waste disposal and the use of pesticides, fertilizers, and other chemicals near wells can lead to water contamination. It is important for well owners to be aware of potential sources of contamination in their community and to regularly test their well water for any signs of pollution.

There are several ways to test for water pollution caused by industrial and household contaminants. The boiling method, for example, can be used to detect dissolved solids in water. After boiling the water and letting the pot cool down, one can run their fingers along the bottom of the pot. If there is a gritty, sticky, or chalky residue, it indicates the presence of dissolved solids in the water supply.

Comparing the odor, color, and taste of tap water to those of distilled water samples is another simple method to evaluate water quality at home. If the household drinking water has an unusual odor, color, or taste compared to the distilled water, it may be contaminated.

More advanced testing methods include bacterial testing, which is essential for determining water safety. E. coli bacteria, for instance, can cause serious health issues when consumed, and its presence indicates fecal matter exposure. Testing for total coliform bacteria is also important, as a high count can indicate the presence of harmful germs, such as viruses, bacteria, and parasites.

PH level testing is another critical aspect of water quality assessment. While coliform bacteria and pH levels are usually not harmful, they indicate the potential presence of other contaminants. If the pH level of the water is too low or too high, it can damage pipes, causing heavy metals like lead to leach into the water, posing a health risk.

It is important to note that while at-home water testing can provide a baseline for general water quality, consulting professionals in water purification is necessary for more nuanced results and to develop a mitigation plan.

Colour, taste and smell

Water pollution can sometimes be detected by our senses of colour, taste, and smell. While these senses are not always accurate indicators of health risks, they can signal potential problems with the water.

Colour

Water should ideally be colourless. Coloured water could signal the presence of iron, rust, or other contaminants in the mains or household plumbing. Red, orange, yellow, or brown water could be caused by iron or rust. Yellow or brown hues could also be caused by tannins from decaying vegetation and leaves.

Taste and Smell

Water that tastes or smells strange may indicate the presence of algae, bacteria, or other contaminants. A rotten-egg or sulfur smell or taste, for example, suggests the presence of hydrogen sulfide, often caused by bacteria in the water. Musty or earthy tastes and odours may be caused by dissolved solids, or by iron bacteria, mould, fungi, algal blooms, or a high bacterial count. A metallic taste or smell could indicate mercury, lead, copper, arsenic, manganese, zinc, or iron in the water. A fishy smell could be caused by surfactants, barium, cadmium, high organic matter, algal blooms, or a reaction with chloramine/ammonia in the water.

Chlorine is commonly used to disinfect water, and it can usually be detected by taste or smell at concentrations of 5 mg/l or below. A chlorine smell or taste does not necessarily indicate water pollution, but consumers may want to remove it for taste reasons.

Limitations

While our senses can be useful diagnostic tools, they have limitations. Smoking, disease, colour blindness, or failing eyesight can all impact our ability to sense water pollution. Furthermore, some contaminants may not be detectable by our senses, even if they pose a significant health risk.

Further Testing

If you suspect water pollution, you can use a Self-Test Web App or a Drinking Water Self-Diagnostic Tool to narrow down the potential causes of your water issues.

Bacterial and chemical sources

Bacterial Sources

Bacteria are a significant cause of water pollution and can lead to serious illnesses and even deaths. Escherichia coli (E. coli) is a common indicator organism used to detect the presence of disease-causing bacteria in water. While most E. coli strains are harmless, some can indicate high levels of sewage and animal waste. Other indicator organisms include Pseudomonas aeruginosa and coliforms, which are also found in human and animal digestive tracts. Testing for bacteria typically involves taking water samples and using methods like plate count, membrane filtration, or Most Probable Number (MPN) tests to estimate bacterial concentration and identify specific species. Regular testing is crucial, especially for public drinking water, to prevent potential health risks.

Chemical Sources

Chemical pollution in water can come from various sources, including industrial discharges, agricultural activities, and human activities such as chemical spills. Common chemicals tested in water include nitrate, phosphate, chlorine, chloride, lead, copper, iron, and zinc. These chemicals can have adverse effects on both the environment and human health. For example, high levels of nitrate and phosphate can lead to eutrophication, causing excessive plant and algal growth and reducing oxygen levels in the water, which is harmful to aquatic life. Additionally, chemicals like sodium bicarbonate, iron, zinc, carbon dioxide, sulfate, and chloride released by industrial units can be dangerous for human consumption.

Testing for chemical pollution typically involves using test strips, color disk test kits, or digital meters to measure specific chemical concentrations. These tests are designed to be low-tech and affordable, making them accessible to a wide range of users. More advanced methods, such as liquid chromatography-tandem mass spectrometry, can also be employed to identify a broader range of chemical contaminants.

Frequently asked questions