Water Pollution: Understanding The Chemical Contaminants

Water pollution is a pressing issue that affects the quality and safety of water sources worldwide. It refers to the presence of harmful substances, known as contaminants, in water bodies such as lakes, rivers, and oceans. These contaminants can be physical, chemical, biological, or radiological in nature, and they pose a significant threat to both human health and the environment. While some contaminants are naturally occurring, human activities, such as industrial processes, agricultural practices, and improper waste disposal, are major contributors to water pollution. Chemicals that pollute water include pesticides, fertilizers, heavy metals, toxins, and various emerging contaminants like pharmaceuticals and personal care products. The impact of these chemicals on human health and the environment is a growing concern, and efforts to address water pollution and ensure access to clean water are ongoing.

Industrial chemicals

One of the most significant sources of industrial chemical pollution is wastewater discharge. Industrial facilities often release untreated or partially treated wastewater containing various chemicals, heavy metals, and toxins. This wastewater can contaminate rivers, lakes, and oceans, impacting aquatic ecosystems and drinking water sources. In the United States, wastewater treatment facilities process approximately 34 billion gallons of wastewater daily, reducing pollutants such as heavy metals and toxic chemicals in industrial waste. However, ageing and overburdened sewage systems also release billions of gallons of untreated wastewater annually, contributing to water pollution.

Another source of industrial chemical pollution is runoff from industrial sites. During rainfall, stormwater can carry chemicals, oils, grease, and other contaminants from industrial areas into nearby waterways. This type of pollution, known as non-point source pollution, is challenging to regulate as it originates from diffuse sources. Industrial facilities located near waterways are particularly susceptible to this form of pollution, as contaminants can easily wash into rivers, lakes, or oceans.

Specific industrial chemicals commonly found in water include PFAS (per- and polyfluoroalkyl substances), which have been used in manufacturing since the 1940s. PFAS are highly persistent in the environment and have been linked to various health issues. Dioxins, byproducts of industrial processes such as incineration and bleaching in the paper industry, are another significant pollutant. These compounds are fat-soluble, accumulating in the fatty tissues of living organisms and disrupting hormonal and reproductive systems. Cadmium, a toxic metal, is also introduced into water systems through industrial processes such as metal ore smelting and processing. Exposure to cadmium can cause acute health issues and has been linked to a signature painful bone disease.

The Clean Water Act in the United States mandates that industries disclose the pollutants they release into water sources. However, enforcement of this regulation is often lacking, and many industrial chemicals remain undisclosed. This lack of transparency poses a significant threat to communities, particularly those downstream from industrial facilities, who bear the brunt of the health consequences.

Pesticides and fertilisers

Pesticides are substances used to control, prevent, kill, or repel pests such as insects, weeds, and other organisms that attack food crops. They can be made from natural ingredients or synthetic chemicals, with each type varying in toxicity to humans and other animals. The use of pesticides has contributed to the United States becoming the largest producer of food products globally. However, their benefit to agriculture comes at a cost. Pesticides contain toxic materials that can severely threaten humans, animals, aquatic life, and plants. Once released into the environment, pesticides can move through the hydrologic system via air, water, or particles, eventually reaching water sources such as streams or groundwater.

Fertilisers, on the other hand, are responsible for nutrient pollution, which is the leading type of contamination in freshwater sources. Excess nitrogen and phosphorus in water or air from fertilisers can cause algal blooms, a toxic phenomenon that harms people and wildlife. Fertilisers applied to agricultural lands, residential areas, and commercial landscapes can easily wash into nearby creeks, rivers, and oceans during rainfall, degrading water quality.

The overuse and misuse of pesticides and fertilisers have detrimental effects on the environment and human health. When pesticides and fertilisers enter waterways, they can be deadly to aquatic life, particularly tiny creatures known as aquatic invertebrates. This disruption in the aquatic food chain can have far-reaching consequences for larger organisms that depend on these smaller creatures for survival. Additionally, pesticides and fertilisers can increase the risk of cancer and cause reproductive problems, as well as impair eye, liver, and kidney functions in humans.

To prevent water pollution from pesticides and fertilisers, proper application and disposal methods are crucial. Applying these substances under calm weather conditions, with low wind speeds, and no rain or snow forecast can help minimise their movement into water sources. Additionally, limiting the use of highly toxic pesticides such as pyrethroids, organophosphates, and fipronil can reduce their presence in waterways.

While wastewater treatment facilities work to reduce pollutants, they may not remove all pesticide and fertiliser nutrients. Therefore, it is essential to be vigilant about the quality of drinking water. Understanding the source and treatment processes of drinking water can help individuals take the necessary steps to protect themselves from potential contamination.

Pharmaceuticals and personal care products

PPCPs can enter water sources through various pathways. One significant source is household wastewater, as humans excrete excess and unused medications through urine and faeces. Additionally, topically applied drugs and personal care products can be washed off during bathing and cleaning, ending up in the household wastewater stream. The improper disposal of expired or unused medications and personal care products, such as flushing them down the drain, also contributes to water pollution.

PPCPs are not limited to household sources; they also originate from industrial settings, hospitals, long-term care facilities, and landfill leachate. Conventional wastewater treatment methods often fail to fully break down and remove PPCPs from wastewater. As a result, treated wastewater released into surface water or used for irrigation may still contain traces of these contaminants.

The presence of PPCPs in water sources is a growing concern due to their potential impact on aquatic ecosystems and human health. These substances can accumulate in the environment due to their weak degradation and persistence. Aquatic sediments can hold a significant amount of PPCPs, and they can partition between water, sediment, and other components of the aquatic ecosystem. The soluble and bioactive nature of pharmaceuticals and some personal care products increases the risk of biotransformation and potential harm to non-target organisms.

To address the issue of PPCP water pollution, more efficient treatment methods are being explored, such as the use of photocatalysts immobilized on functionalized carbon in advanced oxidation processes (AOPs). These processes aim to improve the degradation of PPCPs in water matrices, reducing their potential impact on the environment and human health.

Nitrogen and phosphorus

Agricultural practices are a major source of nitrogen and phosphorus pollution. Animal manure and chemical fertilizers used for crop growth contain these nutrients. When plants do not fully utilize them, they can leave farm fields, impacting air and water quality. Nitrogen and phosphorus can be washed into waterways by stormwater runoff, a process known as eutrophication. This excess of nutrients can lead to severe algal growth, blocking light necessary for the growth of other plants like seagrasses. When the algae and seagrass die and decay, they deplete the oxygen levels in the water, creating an unsuitable environment for aquatic life.

Wastewater is another significant contributor to nitrogen and phosphorus pollution. Sewer and septic systems are responsible for treating large volumes of waste. However, they may not always operate optimally or effectively remove these nutrients before discharging the treated water back into natural water bodies. As a result, wastewater treatment facilities inadvertently release pollutants such as nitrogen and phosphorus, in addition to heavy metals and toxic chemicals from industrial waste.

The burning of fossil fuels for electric power generation, industry, transportation, and agriculture has also increased the amount of nitrogen in the atmosphere. This elevated atmospheric nitrogen eventually finds its way into aquatic systems, leading to pollution. Additionally, certain soaps, detergents, yard fertilizers, and pet waste contain nitrogen and phosphorus, contributing to the issue.

To address this issue, regulatory bodies like the EPA have established limits on the amount of nitrogen and phosphorus that can be discharged into waterways. These regulations, known as Total Maximum Daily Loads (TMDLs), aim to reduce nutrient pollution and protect water quality. Implementing nutrient management strategies in agriculture can help achieve these goals while also improving the efficiency and profitability of agricultural producers.

Oil and gasoline

Oil pollution is a particular problem in rivers due to currents carrying the oil great distances from its origin. It can also cause significant damage in oceans, as tides can carry the oil to beaches and intertidal zones, which are especially sensitive to oil pollution.

Gasoline is a light fuel that will almost entirely evaporate within one or two days. However, it is still harmful to the environment. Nearly half of the estimated 1 million tons of oil that enters marine environments each year comes from land-based sources such as factories, farms, and cities.

The use of oilfield wastewater to irrigate crops in drought-stricken regions, such as California, is a growing concern. There is a lack of scientific evidence to confirm that this practice does not pose risks to public health or the environment. Further assessment of the potential risks of using oilfield wastewater for irrigation is necessary before it is more widely adopted.

In addition to oil spills, the oil and gas industry also contributes to water pollution through toxic waste leaks and surface spills from poorly constructed and maintained wells. The Environmental Protection Agency states that the majority of land and water contamination from oil and gas development is caused by these factors.

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