Managing City Water Disposal And Pollution

Water pollution is a pressing issue that affects the health, environment, and economy of a city and its surrounding areas. With urban areas characterised by high population densities, environmental impacts are concentrated in smaller areas, including waterways. This pollution comes from a variety of sources, such as industrial waste, oil spills, agricultural runoff, and residential waste. To combat this, cities typically build sewage treatment plants to treat wastewater before disposing of it in rivers or drains. However, improper disposal methods, like dumping solid waste into bodies of water, can have detrimental effects on aquatic ecosystems and human health.

Sewage treatment plants

The primary stage involves separating solids from liquids. The sewage is pumped into sedimentation tanks, where gravity forces solids to the bottom of the tank. The water is then released, leaving behind a sludge/slurry. This sludge is sometimes repurposed as a fertilizer but requires treatment to stabilize it. The two most frequently used processes for this are activated sludge (aerated ponds) and filter beds (sewage tricked over aggregate). 'Good' bacteria in the sludge/aggregate break down the pathogens in the wastewater.

After secondary treatment, wastewater can sometimes be released, providing there is a low risk to human and animal life and the environment. Water is considered clean after secondary treatment, but tertiary treatment is required for discharge into protected waters. The type of tertiary treatment depends on the wastewater. For example, wastewater released into bathing or shellfish waters must undergo disinfection, and nutrients like phosphorous must be removed.

Today's sewage treatment plants are highly automated, reducing the risk of human error. Sensor technology, networks, and automatic controls keep plants running smoothly without human intervention.

Radioactive waste disposal

Radioactive waste is a type of hazardous waste that contains radioactive material. It is generated by a variety of activities, including nuclear medicine, nuclear power plants, nuclear research, nuclear decommissioning, uranium mining, nuclear weapons reprocessing, and the production and testing of military weapons. Radioactive waste can persist in the environment for thousands of years and poses a significant threat to human health and the environment, making its disposal a critical challenge.

Radioactive waste is typically classified into three main categories: low-level waste (LLW), intermediate-level waste (ILW), and high-level waste (HLW). LLW includes items such as paper, rags, tools, and clothing, which contain small amounts of mostly short-lived radioactivity. ILW contains higher amounts of radioactivity and requires some shielding. HLW is highly radioactive and generates decay heat, necessitating cooling and shielding.

The disposal methods for radioactive waste depend on its classification and the specific regulations of the country in question. In general, LLW can be disposed of in near-surface disposal facilities or land-based disposal sites. ILW is typically stored in geological repositories, and some countries dispose of it in near-surface facilities. HLW requires long-term isolation and is often disposed of through deep geological disposal, where it is buried in stable geological formations.

In the United States, the Department of Energy (DOE) oversees the treatment and disposal of radioactive waste from nuclear weapons programs. The DOE stores most of this waste in tanks at three sites. High-level mixed waste must be vitrified, or immobilized in glass, before disposal in deep geological repositories. The United States has only one such repository for defense-related transuranic waste, the Waste Isolation Pilot Plant (WIPP) in New Mexico.

Oil spills and leaks

To address oil spills and leaks, several methods and technologies are employed:

• Containment and absorption: Booms, barriers, and skimmers are used to contain and collect the spilled oil. Absorbent materials such as sawdust, kitty litter, and commercial products like Pig Blankets are then used to soak up the oil.
• Dispersants: These are chemical agents applied to break down the oil into smaller droplets, making it easier to disperse and biodegrade.
• Bioremediation: This involves using microorganisms or biological agents to break down the oil into less harmful substances.
• In-situ burning: In some cases, the spilled oil is ignited and burned to reduce the amount of oil in the water.
• Mechanical cleanup: This includes methods such as using pumps, vacuums, and oil-water separators to remove oil from the water surface.

In terms of prevention, cities play a crucial role in properly managing and treating sewage and wastewater. Most cities build sewage treatment plants to treat wastewater before disposing of it. However, oil spills and leaks can still occur during transportation or as a result of illegal discharges. To prevent and mitigate these incidents, various government agencies, such as the Environmental Protection Agency (EPA) in the United States, are responsible for responding to onshore oil spills. Additionally, individuals can take preventive measures, such as properly maintaining their vehicles to avoid oil leaks and properly disposing of oils and chemicals.

Solid waste management

One successful approach to solid waste management is the implementation of decentralized waste management systems. This involves separating biodegradable waste at the ward level, treating it in small composting plants, and utilizing the resulting biogas for cooking. Alappuzha in Kerala, India, has effectively addressed waste management issues through decentralization, earning the Clean City Award in 2016.

Another key aspect of solid waste management is citizen engagement and behavior change. In Colombia, the national government launched an integrated solid waste management policy, emphasizing household waste separation. Through awareness campaigns, including public meetings and door-to-door visits, residents were encouraged to separate organic waste for composting. This initiative reduced contamination levels and provided a rich compost that residents used as organic fertilizer.

Additionally, recycling and waste reduction play vital roles in solid waste management. Cities like Osaka, Japan, have significantly reduced the volume of waste sent for disposal by increasing recycling rates. Instead of dumping waste in landfills, Osaka utilizes high-tech plants to burn waste and generate electricity and municipal hot water. Similarly, Ljubljana, the capital of Slovenia, has committed to maximizing recycling and waste reduction, aiming to become the first European zero-waste capital.

To support cities in solid waste management, organizations like the World Bank provide financing and technical expertise. The World Bank's waste management projects address the entire lifecycle of waste, from generation to collection, treatment, and disposal. They provide capital investments for infrastructure upgrades, advise on legal structures and policies, promote environmentally sound disposal technologies, and emphasize citizen engagement for functional waste systems. Since 2000, the World Bank has committed over $4.7 billion to solid waste management programs worldwide.

Stormwater runoff

The impacts of stormwater runoff pollution are extensive. It has led to the closure of shellfish and swimming beaches, contaminated drinking water supplies, and harmed or killed fish and other wildlife. The Washington Department of Ecology estimates that stormwater runoff accounts for one-third of all polluted waters in the state. Across the United States, unmanaged stormwater runoff has caused significant damage to streams, lakes, and estuaries, particularly in areas transitioning from rural to urban land use.

To reduce stormwater runoff pollution, several measures can be implemented. One approach is to reduce the amount of waste and pollutants that can be carried away by stormwater. This includes properly disposing of waste, such as throwing masks, wipes, and gloves in the trash rather than on the street or in recycling bins. Reducing plastic consumption and reusing or recycling plastic products are also essential. Additionally, addressing oil leaks in vehicles and properly disposing of automotive fluids can help minimize the amount of oil that enters stormwater runoff.

Another strategy is to decrease the amount of stormwater runoff itself. This can be achieved by reducing impervious surfaces, such as concrete or asphalt, and increasing vegetated land cover. Homeowners can replace part of their lawns with native, drought-resistant plants, add compost and mulch to planting soil, and maintain their septic systems to prevent leaks. These actions help retain rainwater and reduce the volume of stormwater flowing into water bodies, thereby minimizing the impact of pollutants.

It is important to note that individual actions alone may not be sufficient to address stormwater runoff pollution entirely. While these measures can help reduce each person's contribution to the problem, effective management of stormwater runoff often requires a combination of individual efforts and proper waste management infrastructure. This includes the implementation of modern sewage treatment plants and the development of strategies to address both point sources and dispersed sources of pollution.

Frequently asked questions