Water Pollution: Human Impact And Our Future

Water pollution is the contamination of water bodies, including lakes, rivers, oceans, aquifers, reservoirs, and groundwater, which negatively impact their use. This is often a result of human activities, such as sewage discharges, industrial activities, agricultural activities, and urban runoff, including stormwater. Water pollution can lead to the degradation of aquatic ecosystems and the spread of water-borne diseases, as well as a reduction in ecosystem services such as drinking water. The contamination of water sources can cause harmful bacteria, viruses, parasites, fertilisers, pesticides, pharmaceutical products, nitrates, phosphates, plastics, faecal waste, and even radioactive substances to enter our drinking water.

Sewage and industrial waste

Sewage

Human activities that generate domestic sewage cause water pollution by contaminating water with disease-causing microorganisms and poisonous substances. Globally, about 4.5 billion people do not have access to safely managed sanitation. The practice of open defecation, for example, can lead to water pollution during rain events or floods when human feces are moved from the ground into surface waters. Even in wealthy nations, accidental or illegal releases from sewage treatment facilities contribute harmful pathogens to waterways.

Industrial Waste

Industrial wastewater contains many organic and inorganic contaminants that are difficult to remove using conventional secondary treatments. The main concern with industrial wastewater is the increasing amount and variety of synthetic compounds that are discharged into the environment. These include heavy metals, pesticides, and plastics, which can be toxic, reactive, carcinogenic, or ignitable. Industrial waste can also contain high concentrations of dissolved solids (salts), naturally occurring radionuclides, and metals, as well as other pollutants used in drilling and well completion.

The treatment of wastewater before it is released into water bodies is crucial to maximize the quality and quantity of potable water. Several treatment plants are being set up to use chemical, electrochemical, biological, and physical processes to release potable water.

Agricultural runoff

Agricultural activities, such as the use of pesticides, fertilizers, and animal manure, can contaminate groundwater and surface water sources. Groundwater pollution occurs when pollutants are released into the ground and seep into the underground water stores. This type of pollution is challenging and costly to remediate, rendering the affected water sources unusable for extended periods.

Fertilizers and manure contain elevated levels of nitrogen and phosphorus, which can stimulate algal blooms in water bodies. These blooms can lead to hypoxic conditions, depriving aquatic life of oxygen and causing harm. Additionally, excessive sedimentation from erosion can overwhelm aquatic ecosystems, smother breeding areas, and degrade coastal ecosystems, including coral reefs.

Pesticides, which are commonly used in agriculture to control weeds, insects, and rodents, are another significant source of water pollution. These toxic chemicals can contaminate water sources, posing risks to aquatic life, wildlife that consumes fish, and drinking water supplies. The health impacts of exposure to these pesticides can be severe, particularly for children, and have been linked to developmental issues and chronic diseases.

Livestock operations, such as Concentrated Animal Feeding Operations (CAFOs), produce large quantities of manure, which is often spread on land untreated. When applied in excess, this manure can lead to runoff, contaminating nearby water sources. This runoff contains bacteria and nutrients that can affect drinking water supplies and cause beach and shellfish bed closures.

Microplastics

The impacts of microplastics on marine ecosystems are significant. The salty nature of seawater may affect their physical and chemical properties, influencing their interactions with marine organisms. The ingestion of microplastics by aquatic organisms can lead to bioaccumulation and biomagnification in the food web, impacting biodiversity, ecosystem health, and human well-being. The study and mitigation of microplastic pollution are crucial to protecting both freshwater and marine environments.

To reduce microplastic pollution, individuals can favour products made with bio-based and biodegradable plastics and sustainable packaging. Recycling and reusing plastic products are also effective remedies. However, the situation will only change if food retailers and restaurants adopt more sustainable practices and big companies switch to sustainable food packaging alternatives.

Radioactivity and heat

Anthropogenic sources of radioactive pollution include nuclear weapon testing, nuclear disasters, nuclear power plants, and the dumping of radioactive waste into surface water bodies. Uranium, thorium, and actinium from the NORM (Naturally Occurring Radioactive Materials) series are common contaminants of water resources. Radium, a descendant of the NORM series, can penetrate groundwater through rock dissolution, the decay of uranium and thorium, and desorption processes. Mining activities, nuclear reactors, and nuclear warhead experiments further contribute to radioactive contamination of water.

Radioactive elements, such as radium and uranium, are naturally found in rock and soil and can dissolve in water. Radon, a radioactive gas, can occur naturally in groundwater as a result of radium decay. If not removed, radon can be released into the air during everyday activities like showering or washing dishes. Public drinking water systems employ filtration methods to remove radionuclides, but standard filters may not eliminate all radioactive contaminants, highlighting the need for improved monitoring and regulations.

In addition to radioactivity, heat is also a significant pollutant of water. Heat pollution, or thermal pollution, occurs when human activities raise the temperature of water bodies. Power plants are major contributors to thermal pollution, with about 75-80% of thermal pollution in the United States attributed to them. Other industrial sources include petroleum refineries, pulp and paper mills, chemical plants, steel mills, and smelters.

Thermal pollution has far-reaching ecological consequences. Elevated water temperatures decrease the level of dissolved oxygen, which is essential for aquatic life. This increase in temperature also boosts the metabolic rate of aquatic organisms, leading to increased food consumption and potential resource depletion. Abrupt changes in water temperature, known as "thermal shock," can be fatal to fish and other organisms adapted to specific temperature ranges.

Mitigation strategies for thermal pollution include converting facilities to closed-loop cooling systems and designing dams to release warmer surface waters instead of colder bottom waters. Stormwater management facilities, such as bioretention systems and infiltration basins, can also help reduce thermal pollution by allowing water to release excess heat before entering natural water bodies.

Natural causes

Sedimentation: Sediment pollution can occur naturally due to erosion or silt and sediment from construction sites. This clouds bodies of water, causing harm to ecosystems and drinking water. It inhibits sunlight from entering the water, killing plants and organisms and disrupting the food chain. It can also clog fish gills and make waterways unnavigable.

Natural Water Pollutants: Fluoride and arsenic are two common natural pollutants found in water. The overexploitation of aquifers can worsen the problems caused by these natural pollutants. According to the WHO, over 400 million people worldwide are affected by fluoride pollution in water, and more than 140 million suffer from arsenic presence in around 70 countries. Arsenic is a common metalloid found in the atmosphere, hydrosphere, and soil, while fluoride is found in all natural waters to varying degrees. Excess fluoride ingestion can be harmful and the WHO has established limits for human consumption.

Algal Blooms: Excess nutrients, such as nitrates and phosphates, in water can promote the growth of algae, leading to dense and rapid growth known as algal blooms. When the algae die, oxygen in the water declines as microorganisms use oxygen to decompose the algae. This process, called eutrophication, is naturally occurring and inevitable, but it can be accelerated by human activity.

Oil Seeps: While large oil spills are often the result of human activity, oil is also naturally released from under the ocean floor through fractures called seeps.

Pathogens: Domestic sewage is a primary source of pathogens (disease-causing microorganisms) and putrescible organic substances. Sewage from cities and towns can contain pathogens that pose a direct threat to public health.

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