Water Pollution (AQA A-Level Geography): Revision Notes

Water Pollution

What is water pollution?

Water pollution occurs when harmful substances enter and contaminate water bodies such as rivers, lakes, oceans, aquifers and groundwater. This happens when pollutants are released into water without proper treatment to remove these dangerous compounds.

In urban environments, water pollution is particularly problematic. Cities have extensive areas of hard surfaces like roads, pavements and buildings that water cannot penetrate. These impermeable surfaces increase the volume of rainwater flowing over streets and into drainage systems. As this water flows, it collects and carries numerous pollutants including oils, heavy metals, rubber particles and other contaminants from motor vehicles into waterways and streams.

When these systems exceed their capacity during heavy rainfall, untreated sewage may be released directly into rivers and streams. Research indicates that urban stormwater can be just as contaminated as untreated domestic wastewater.

Causes of water pollution in urban areas

Urban areas generate water pollution through several key pathways:

• Surface run-off from streets: Rainwater flowing over roads and pavements carries oil, heavy metals and other contaminants from motor vehicles into water systems

• Industrial waste: Factories and industrial sites may discharge waste products that have not been properly treated before release

• Untreated or poorly treated sewage: Sewage with low dissolved oxygen content and high levels of pollutants such as nitrates, phosphorus and bacteria. Even treated sewage still contains some pollutants when discharged into rivers

• Rubbish dumps, toxic waste and chemical storage: These facilities can leak pollutants into surrounding water sources through the soil or directly into water bodies

• Intentional dumping: Deliberate disposal of hazardous substances into water systems

• Air pollution impacts: Pollutants from the atmosphere can be deposited through rain, leading to nitrogen and ammonium contamination. This atmospheric deposition alters water chemistry in the affected area

Consequences of water pollution

Water pollution creates serious problems for both human populations and natural ecosystems. The scale of the issue is enormous: over 1.2 billion people worldwide lack access to clean water. Waterborne infections account for 80 per cent of all infectious diseases globally.

Health impacts

Water pollution affects human health in several ways:

• Heavy metals from industrial processes can slow child development, cause birth defects and may be carcinogenic (cancer-causing)

• Industrial waste often contains toxic compounds that damage the health of aquatic animals and people who consume contaminated fish. These toxins can cause immune system suppression, reproductive failure or poisoning

• Microbial pollutants from sewage lead to infectious diseases affecting both aquatic life and terrestrial life through contaminated drinking water. Microbial water pollution causes diseases such as cholera and typhoid fever, which are a major cause of infant mortality in low-income countries

Environmental impacts

The environmental consequences of water pollution are equally severe:

• Nutrients and organic matter cause an increase in aerobic algae, which deplete oxygen from the water. This process, called eutrophication, can lead to the suffocation of fish and other aquatic organisms

• Suspended particles in freshwater reduce drinking water quality for humans and degrade the aquatic environment for marine life. These particles also reduce sunlight penetration, disrupting the growth of photosynthetic plants and micro-organisms

• Ecosystem damage: Water pollution creates breeding grounds for malaria-carrying mosquitoes and damages ecosystems, potentially leading to species extinction

Water problems in India

Managing water pollution

Improving water quality requires strategies to prevent, treat and remediate water pollution. Ideally, pollutants are prevented from entering watercourses in the first place. However, the reality is that potential pollutants are treated before they are discharged. The final and often most expensive strategy is when polluted watercourses are restored through remediation.

Approaches in high-income countries

In most high-income countries, water quality improvement focuses on two main approaches:

1. Construction of water-treatment facilities and wastewater plants: These facilities process water before it is released back into the environment

2. Regulations aimed at point source polluters: Industries which release water pollution into receiving waters or sewer systems that flow into treatment plants must comply with strict standards

Lack of money and inadequate technology in low-income countries have resulted in much lower water quality standards. Effective legislation is often absent and enforcement of pollution controls is limited.

Key water pollution strategies

Low-impact development (LID)

This approach uses several techniques:

• Permeable streets and pavements allow water to soak into the soil rather than flow directly into sewers
• 'Green' roofs, rain gardens and more urban parks enable water to infiltrate into soils
• Filtering stormwater through vegetation and soil has been shown to reduce organic pollutants, oils and heavy metals by more than 90 per cent

Legislation, regulation and enforcement

Many different anti-pollution laws and agreements exist worldwide. However, these laws need to be enforced effectively. Some cities have adopted incentive-based approaches:

Education and awareness

The more people know about the causes and effects of pollution, the more likely they will avoid adding to the problem. In 2014, Wessex Water used mobile billboards in hotspot areas urging its customers to get behind a campaign encouraging people to bin wet wipes rather than flush them down the toilet. Wet wipes are a common cause of sewer blockages since they do not decompose like toilet paper.

Improvements in sewage and wastewater processing

Upgrading sewage infrastructure prevents untreated waste from entering water bodies. This includes expanding treatment capacity and updating ageing systems.

Appropriate technology

The Thames Tideway Tunnel

Dereliction

In the UK, de-industrialisation led to many people leaving the inner city and industrial buildings being abandoned. Alongside this, services such as public houses and shops may also have become vacant as areas became subject to urban decline.

Impacts of dereliction

Dereliction has negative impacts on the surrounding area:

• Crime and vandalism rates tend to be higher
• House prices fall and out-migration of residents takes place
• The high costs involved in urban renewal often discourage authorities and individuals from renovation or rebuilding
• The presence of listed buildings, which are subject to considerable planning regulation, can significantly increase the investment needed

Health risks

Derelict land can pose significant risks to human health. Contamination from industrial processes lives on in an environment long after the industry that produced or used those chemicals has gone.