Water Pollution: Sources Of Contaminated Drinking Water

Drinking water can become contaminated in a variety of ways, posing a significant threat to public health. Contaminated drinking water can transmit diseases such as cholera, dysentery, typhoid, and polio, and is estimated to cause approximately 505,000 diarrhoeal deaths each year. In 2022, at least 1.7 billion people used a drinking water source contaminated with faeces, which poses the greatest risk to drinking water safety. Contamination can occur at the water source, such as a lake or groundwater, or during its journey through pipes to homes. Natural sources, such as rocks and soil containing chemicals like arsenic or radon, can pollute water. Human activities, including industrial processes, agriculture, and improper waste disposal, also play a significant role in water pollution.

Natural deposits in the earth, such as arsenic and radon

Drinking water can become polluted with arsenic and radon, which are natural deposits in the earth. Arsenic is a toxic element that can be released from the earth's crust into natural waters when the chemistry of the aquatic environment changes. Arsenic is a minor but ubiquitous element of the earth's crust, and some of its chemical species are volatile and highly soluble in water. Arsenic is easily released from the earth's crust into natural waters in conjunction with changes to the chemistry of the aquatic environment.

There are three major natural sources of arsenic contamination: hydrothermal activity, ore deposits, and Cenozoic sediments. Arsenic is a volatile component of magma and is highly soluble in water. Arsenic from hot springs can be transported in surface waters and enter riverbed sediments. Ore deposits are the second main source of arsenic. Arsenic-bearing marcasite found in hydrothermal ore deposits can cause groundwater contamination. The third main source of arsenic contamination is aquifers in Cenozoic sediments, which occur widely around the world.

Radon is a chemically inert radioactive gas that is formed by the natural radioactive decay of uranium in rock, soil, and water. It can be found in all 50 states in the US. Radon can dissolve and accumulate in water from underground sources, such as wells. When water that contains radon is used for showering, washing dishes, or cooking, radon gas escapes from the water and goes into the air. Some radon also stays in the water. According to the EPA, radon in drinking water causes about 168 cancer deaths per year.

Industrial or farming pollution, including fertilisers and pesticides

Fertilisers

Fertilisers are a significant contributor to water pollution. When excess fertiliser is applied to farm fields, the excess nutrients leech into surface and groundwater, causing algal blooms and nitrate contamination. This impacts drinking water sources and can result in eutrophication, hypoxia, and the creation of "dead zones" where aquatic life cannot survive.

For example, in the US, agricultural pollution is the top source of contamination in rivers and streams and the second-biggest source in wetlands. The excessive use of fertilisers can also lead to an increase in phosphorus levels in water bodies, which can disrupt the natural balance and contribute to eutrophication.

Pesticides

Pesticides are another major source of water pollution. They are applied to farmlands, gardens, and lawns and can make their way into groundwater or surface water systems that feed drinking water supplies. The use of pesticides in agriculture and urban areas has led to their presence in rivers, lakes, and other water sources.

Pesticides can have detrimental effects on human health, especially with chronic exposure. They can cause immunosuppression, hormone disruption, reduced intelligence, reproductive issues, and cancer. Even low concentrations of pesticides in water can pose health risks, as they can bioaccumulate in the human body and disrupt normal functioning.

Other Types of Industrial or Farming Pollution

In addition to fertilisers and pesticides, there are other types of industrial or farming pollution that can impact drinking water sources:

• Animal waste from concentrated animal feeding operations (CAFOs) or factory farms can contaminate water through runoff or leaks from waste-containment areas.
• Heavy metals, such as copper and zinc, used in farming practices, can accumulate in soil and contaminate water supplies.
• Industrial wastewater can contain chemicals, metals, solvents, and toxic sludge that can pollute water sources if not properly treated.

Human and animal waste, including harmful microbes

Human and animal waste is a significant source of water pollution, with harmful microbes being one of the most common contaminants. Human waste from sewage and septic systems can carry disease-causing bacteria and viruses into drinking water sources, with similar risks posed by animal waste from feedlots and wildlife.

Human waste can introduce a range of harmful microbes into water sources, including pathogens responsible for diseases such as cholera, giardia, typhoid, and hepatitis. These microbes can cause a range of health issues, from gastrointestinal illnesses to nervous system disorders, reproductive issues, and chronic diseases like cancer.

Animal waste, particularly from industrial animal farms, also contributes to water pollution. Factory farms, with their high density of animals, produce large amounts of waste that is rich in nutrients, including nitrates. This waste can contaminate both groundwater and surface water, leading to increased nitrate levels in drinking water sources. Additionally, the heavy use of veterinary medicines in animal agriculture has led to the presence of antibiotics and other drugs in our drinking water.

The impact of animal waste on water pollution is further exacerbated by the use of manure as fertiliser in agriculture. When manure is applied to fields, it can be washed into nearby waterways during rainfall or irrigation, leading to microbial and chemical contamination. This runoff can also contribute to the formation of algal blooms, which have negative environmental and economic impacts.

To address the issue of water pollution from human and animal waste, proper waste management and treatment systems are crucial. Treating drinking water can significantly reduce the prevalence of waterborne diseases. Additionally, implementing best management practices in agriculture and reducing the use of antibiotics and other veterinary medicines in animal agriculture can help minimise the release of contaminants into water sources.

Treatment and distribution byproducts, such as trihalomethanes

THMs include chloroform, bromodichloromethane, bromoform, and dibromochloromethane. These compounds have been shown to cause DNA damage and are considered potential human carcinogens by organizations like the US EPA. Exposure to THMs has been linked to an increased risk of bladder cancer and reproductive issues. The formation of THMs during water chlorination is influenced by various factors, such as the presence of other ions like bromide and iodide, pH, temperature, and the characteristics of natural organic matter (NOM) in the water.

To address the presence of THMs in drinking water, several control and removal technologies have been developed. One approach is to optimize the chlorine dose used in disinfection. However, this must be done carefully to ensure adequate disinfection without promoting excessive THM formation. Alternative disinfectants, such as chloramines, ozone, and chlorine dioxide, can also be used, although they may have their own limitations and can generate other byproducts.

Another strategy is to focus on reducing the precursors of THMs, specifically natural organic matter (NOM), in the water before disinfection. This can be achieved through processes like coagulation/flocculation, adsorption, ion exchange resin, or membrane filtration. Advanced oxidation processes (AOPs) have also been explored for the elimination of recalcitrant NOM. Additionally, technologies such as air stripping, adsorption by granular activated carbon (GAC), membrane processes, and UV-based processes have been employed to remove THMs after their formation.

The selection of the appropriate technology depends on various factors, including cost-effectiveness and energy efficiency. While nanofiltration membranes and the Fenton process have shown promising results in terms of NOM removal, UV/O3 has been identified as the most energy-efficient process for NOM degradation. The air stripping and GAC-based biodegradation system have also demonstrated effectiveness in removing THMs.

Overall, the presence of THMs in drinking water is a significant concern, and ongoing research aims to optimize treatment processes and technologies to minimize their formation and maximize their removal, ensuring the provision of safe drinking water to communities.

Lead pipes and other leaded parts in older submersible pumps

Lead is a serious threat to drinking water safety. It is a colourless, odourless, and tasteless metal that can go undetected in water. Even low levels of lead in drinking water can cause adverse effects on the central nervous system, kidneys, and blood cell-producing systems. Lead exposure is particularly harmful to the developing brains and nervous systems of fetuses and young children.

The amount of lead that dissolves from metal plumbing generally increases as water corrosivity increases. Water corrosivity is primarily controlled by the water's acidity and calcium carbonate content. Acidic water with low calcium carbonate is more corrosive than water with higher pH and calcium carbonate levels. Soft water (low in dissolved solids) tends to be more corrosive than hard water, and warm water is more corrosive than cold water.

Corrosive water acts to dissolve lead from pipes and solder while the water is in contact with the plumbing. Lead concentrations in drinking water are usually highest in the first water drawn from the tap and may decrease as the water runs. If lead pipes, leaded solder, or brass fixtures are present, even relatively non-corrosive water can dissolve dangerous amounts of lead when the water sits in contact with these materials.

The only way to know if your water contains lead is to have it tested. The EPA suggests taking a sample after running the water for two minutes, following a period of non-use of at least six hours. Take the sample to a certified lab for testing.

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