Understanding Key Sources Of Water Pollution From Biological Factors

Water pollution is a pressing issue that has attracted the attention of governments and environmental agencies worldwide. Point source pollution is a significant contributor to this problem, and it occurs when pollutants are discharged from a single, identifiable point, such as a pipe, ditch, or industrial wastewater outfall. These sources can include biological wastes, sewage, and chemicals, which are released into surface water, affecting rivers, lakes, and oceans. The impact of point source pollution on water quality has been recognised since the early 20th century, with laws and regulations being implemented to address this issue. However, the challenge of managing point source pollution remains, and it continues to be a threat to the health of water ecosystems and human health.

Sewage and wastewater treatment

Point source pollution is characterised by the discharge of sewage or chemicals from a facility with an identified point of release. The main point source of pollution in water is sewage and wastewater treatment.

Sewage treatment is a type of wastewater treatment that aims to remove contaminants from sewage to produce an effluent that is suitable to be discharged into the surrounding environment. Sewage contains wastewater from households, businesses, and possibly pre-treated industrial wastewater. Sewage treatment processes can range from decentralised systems, such as on-site treatment systems, to large centralised systems that use a network of pipes and pump stations to convey sewage to a treatment plant.

The treatment of sewage is part of the field of sanitation, which includes the management of human waste, solid waste, and stormwater drainage. Sewage treatment plants (STPs) are often referred to as wastewater treatment plants (WTPs), with the latter being a broader term that can also refer to industrial wastewater treatment. The overall goal of treating sewage is to produce an effluent that can be discharged into the environment while minimising water pollution or creating an effluent that can be reused.

There are two main stages of sewage treatment, primary and secondary treatment, with advanced treatment incorporating a tertiary treatment stage. Primary treatment involves aerating the wastewater, which puts oxygen back into it, and removes about 60% of suspended solids. Secondary treatment removes more than 90% of suspended solids.

Industrial wastewater and sewage outfalls

Point-source pollution is characterised by the discharge of sewage or chemicals in gas, liquid, or solid form from a facility with an identified point of release. Industrial wastewater and sewage outfalls are a major source of biological water pollution. The increased population has led to a greater demand for goods, causing rapid industrialisation and, consequently, an increase in industrial waste. This waste is polluting our water, air, and soil.

The quality and quantity of wastewater produced depend on the type of industry. It can contain non-biodegradable waste such as heavy metals, pesticides, and plastics, as well as biodegradable compounds like paper, leather, and wool. Industrial wastewater is often toxic, reactive, carcinogenic, or ignitable. Therefore, without proper treatment, discharging this wastewater into water bodies can have detrimental environmental and health effects.

The composition of industrial effluents can include elevated levels of fats, cleaning agents, volatile compounds, and oils, which pose risks to human health and the environment. For example, contaminants found in wastewater from the iron, steel, and petrochemical industries can cause kidney and liver damage, skin manifestations, dermatitis, chronic asthma, rheumatoid arthritis, visceral cancers, and nervous system-related diseases.

To address this issue, several treatment plants have been set up to use chemical, electrochemical, biological, and physical processes to release potable water. Additionally, industrial developers and manufacturers are adopting technologies to ensure cleaner production, reduced water consumption, and less pollution.

In conclusion, industrial wastewater and sewage outfalls are a significant source of biological water pollution. The increasing amount and variety of synthetic compounds contained in industrial discharges pose a challenge for treatment and have detrimental effects on the environment and human health. To mitigate these impacts, it is essential to properly treat wastewater before discharging it into water bodies.

Pesticides, fertilisers, and manure

Point source pollution is characterised by the discharge of sewage or chemicals from a facility with an identified point of release. This includes industrial wastewater and sewage outfalls, as well as atmospheric emissions from stacks, flares, conveyors, and towers.

When pesticides are sprayed near water sources, they can directly cause water pollution. Additionally, agricultural runoff due to rain, irrigation, or melted snow/ice can carry pesticides into water bodies. Traces of pesticides can even find their way into drinking water sources if not properly managed. The chemicals in pesticides can have toxic effects on aquatic life, including fish, plants, and insects.

Fertilisers and manure can also impact water quality when they enter surface water. The nutrients released by these substances stimulate the growth and reproduction of microorganisms, which reduces the dissolved oxygen content in the water. This depletion of oxygen can lead to the suffocation of fish and other aquatic species, resulting in unpleasant odours and degraded water quality.

Furthermore, high levels of nitrates, which are commonly found in fertilisers and manure, can be toxic to both humans and livestock. Nitrates can leach into groundwater and, at elevated levels, can cause nitrate poisoning. In human infants and warm-blooded animals, high nitrate concentrations in drinking water can lead to methemoglobinemia (blue-baby syndrome).

To mitigate the impact of pesticides, fertilisers, and manure on water pollution, sustainable farming practices such as crop rotation, effective manure management, and the adoption of alternative methods that reduce the need for chemicals can be implemented.

Soil erosion and sediment runoff

One of the primary concerns with soil erosion is the increased levels of nitrogen (N) and phosphorus (P) in surface waters. When sediments are transported through surface water runoff and soil erosion, these nutrients can easily move from fields into lakes and streams. This enrichment of nutrients in water bodies often leads to eutrophication, characterised by excessive growth of algae and other aquatic plants. As these organisms die and decompose, they deplete oxygen levels, leading to fish kills, increased turbidity, and shifts in aquatic flora and fauna populations.

Agricultural practices, such as the use of pesticides and fertilisers, play a significant role in soil erosion and water pollution. When these chemicals are applied to fields, they can be washed into nearby water bodies during rainfall or irrigation, leading to biological water pollution. Additionally, construction sites, automotive facilities, and forestry operations also contribute to soil erosion and sediment runoff, as pollutants from these activities can find their way into water sources.

To mitigate the impact of soil erosion and sediment runoff on water quality, various conservation practices have been proposed. These include conservation tillage, no-till farming, buffer strips, terracing, and residue management. By adopting these practices, producers can minimise water erosion and reduce the amount of sediment and nutrients entering water bodies.

It is also important to implement erosion and sediment control (ESC) plans, especially in road, highway, and bridge construction projects. These plans may include the use of best management practices (BMPs) such as seeding, mulching, erosion control blankets, and the creation of grassed swales or filter strips. By stabilising disturbed areas and slowing down the flow of runoff water, these practices allow sediment to settle out, improving water quality.

Oil and chemical spills

Each year, there are thousands of oil and chemical spills in coastal waters, ranging from small ship collisions to fuel transfer mishaps to massive incidents like the BP Deepwater Horizon oil spill. These spills can have devastating consequences for the environment, wildlife, and local communities. Oil penetrates the plumage of birds and the fur of mammals, reducing their insulating abilities and making them more vulnerable to temperature changes and less buoyant in water. Spills can also kill wildlife, destroy habitats, and contaminate critical resources in the food chain, such as fisheries.

The effects of oil spills in estuaries can be particularly damaging. They can wreak havoc on the economies of coastal communities, leading to the closure of fisheries, a decline in tourism, and the temporary shutdown of navigation routes. These environmental and economic damages can persist for decades. Oil spills on roads, flushed into oceans during rainstorms, are another example of land-based point source pollution.

The cleanup and recovery process following an oil spill is challenging and expensive, depending on factors like the type of oil, water temperature, and shoreline characteristics. It can take weeks, months, or even years to remediate. Chemical remediation is the current norm, using compounds to herd and thicken oil for physical recovery, disperse it in water, or facilitate burning it off. However, burning surface oil can create additional air pollution, such as soot particles and toxic gases.

To manage oil and chemical spills, organisations like the Office for Coastal Management (OCM) and the U.S. Integrated Ocean Observing System (IOOS) play crucial roles. OCM assists affected regions in preparing for and managing spills, while IOOS utilises glider and high-frequency radar technologies to monitor and predict the trajectory of spills, helping authorities make informed decisions during response and restoration efforts.

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