Water Pollution: What's Lurking In Our Waterways?

Water pollution is a pressing issue that affects the health of millions of people and the environment worldwide. It refers to the contamination of water bodies such as rivers, lakes, oceans, and groundwater, with harmful substances that degrade aquatic ecosystems, spread water-borne diseases, and reduce the availability of drinking water. These contaminants can be broadly categorized into four sources: sewage discharges, industrial activities, agricultural activities, and urban runoff. Sewage treatment plants are identified as a point source of pollution, while agricultural runoff is considered non-point source or dispersed source pollution, which is more challenging to control. The main pollutants include bacteria, viruses, parasites, fertilisers, pesticides, plastics, and even radioactive substances, many of which are invisible and do not change the colour of the water.

Sewage and wastewater treatment

There are two main types of sewage treatment systems: decentralized and centralized. Decentralized systems treat sewage close to where it is created, such as on-site sewage facilities or septic tanks. Centralized systems, on the other hand, collect and transport sewage through a network of pipes and pump stations to a municipal treatment plant. Centralized systems are further classified into high-tech (high-cost) and low-tech (low-cost) options, as well as intensive or mechanized systems and extensive or nature-based systems.

The sewage treatment process typically involves primary and secondary treatment stages, with advanced treatment incorporating a tertiary treatment stage. Primary treatment removes about 60% of suspended solids from wastewater and involves aerating the wastewater to restore oxygen. Secondary treatment removes more than 90% of suspended solids. Advanced treatment includes additional polishing processes and nutrient removal.

Wastewater treatment is necessary because nature can only handle small amounts of water wastes and pollution. Without proper treatment, the billions of gallons of wastewater produced daily would overwhelm natural systems and contaminate water sources. Wastewater treatment plants aim to reduce pollutants in wastewater to levels that nature can manage, minimizing the impact on rivers, lakes, and other water bodies.

While sewage and wastewater treatment are crucial, they are not always sufficient to prevent water pollution. Combined sewer systems, which collect rainwater runoff, domestic sewage, and industrial wastewater in the same pipe, can overflow during high precipitation periods. These combined sewer overflows (CSOs) release untreated sewage, human waste, industrial waste, toxic materials, and debris directly into receiving waters, posing a significant threat to public health and the environment. Therefore, proper maintenance, infrastructure upgrades, and separation of storm and waste systems, as seen in Atlanta, are essential to mitigate this issue.

Industrial activities

The composition of industrial wastewater depends on its origin and the type of production. For example, wastewater from the pharmaceutical and chemical industries may contain active pharmaceutical ingredients, especially from cleaning production facilities. This can include antibiotics such as sulphamide, penicillin, and amoxicillin, as well as hormones such as cyproterone acetate and letrozole.

Other common types of industrial water pollution include petroleum products, heavy metals, hazardous wastes, and sediments. Petroleum products are used as fuel or lubricating oil and are produced during the manufacture of plastics. Heavy metals, such as copper, lead, cadmium, and selenium, come from various industries, including car manufacturing, mining, and exhaust air systems. Hazardous wastes are highly flammable and corrosive and often come from construction, demolition, manufacturing, and waste treatment processes. Sediments are non-degradable toxins that accumulate in aquatic environments and slowly enter groundwater or are stirred up into the water column.

Inorganic chemical plants are some of the biggest industrial dischargers of toxic pollution. These plants make products like PVC and vinyl chloride, which can be harmful to the environment if spilled or leaked. Oil refineries are also major contributors to water pollution, releasing wastewater containing heavy metals, oils, greases, and industrial salts. Additionally, the coal and gas industries have been associated with water pollution, providing the impetus for the development of alternative, clean energy sources.

While wastewater treatment facilities aim to reduce pollutants, they can become overwhelmed, releasing untreated wastewater into waterways. Industrial activities can also contribute to transboundary pollution when contaminated water from one country spills into the waters of another.

Agricultural activities

The excessive use of pesticides and fertilizers in agriculture is a significant concern. When it rains, these

Urban runoff

Urban stormwater and snowmelt pollution, also known as urban runoff, significantly contribute to the deterioration of surface water quality in many locations. Urban runoff is a nonpoint source of water pollution, meaning that it is challenging to control. As runoff moves, it collects and carries pollutants from various sources, including residential, commercial, and agricultural areas, into local waterways such as lakes, rivers, wetlands, and coastal waters.

One of the major sources of urban runoff pollution is the vehicular transportation sector. When rain falls on roads and parking lots, it can pick up oil and other petroleum products and carry them into water bodies. Additionally, atmospheric deposition and metallic building envelopes are also significant contributors to urban runoff pollution.

Another source of urban runoff pollution is the improper disposal of wastewater from industrial plants and chemical process facilities. This can include toxic chemicals such as lead, mercury, and chromium, which can have harmful effects on aquatic life and human health. Agricultural runoff containing pesticides and fertilisers can also contaminate water bodies, impacting both the environment and the health of those who rely on these water sources.

The impact of urban runoff pollution is not limited to the environment; it also has economic implications. Deteriorating water quality can stall economic growth and exacerbate poverty in affected regions. Additionally, the cost of managing urban runoff and treating contaminated water can be significant for communities.

To mitigate urban runoff pollution, it is essential to implement source controls and other effective pollution mitigation tools. Additionally, individuals can play a role in reducing urban runoff by properly disposing of chemicals, oils, and non-biodegradable items, maintaining their vehicles to prevent leaks, and adopting landscaping practices that reduce runoff and minimise the use of pesticides and herbicides.

Oil spills

The transportation and storage of oil and its derivatives are subject to leakage, contributing to water pollution. Oil can reach the oceans from land-based sources, such as runoff oil from roads and rivers, which is estimated to contribute 11% of oil pollution in the oceans. Oil spills on land may not spread as quickly as in water, but they still have local effects and can be challenging to clean up.

Cleanup and recovery from an oil spill are complex and time-consuming processes, depending on factors such as the type of oil spilled, water temperature, and the types of shorelines and beaches involved. Oil spills can have immediate negative effects on human health, including respiratory and reproductive problems, liver damage, and immune system damage. They also harm aquatic life, making seafood unsafe to eat, and damage recreational areas and natural habitats such as beaches, mangroves, and wetlands.

Notable examples of significant oil spills include the Deepwater Horizon spill in the Gulf of Mexico in 2010, the Exxon Valdez spill in Alaska's Prince William Sound in 1989, and the Ixtoc I spill. These incidents have brought intense media attention and political uproar, highlighting the need for better prevention measures and government responses to oil spills.

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