Water Pollutants: Understanding Common Contaminants In Our Waterways

Water pollution is a pressing issue that endangers the health of millions of people and ecosystems worldwide. Water is easily contaminated by pollutants, and common sources of water pollution include toxic green algae, agricultural practices, and industrial and municipal wastewater. Some of the pollutants found in water include bacteria, viruses, parasites, fertilisers, pesticides, pharmaceuticals, nitrates, plastics, faecal matter, and even radioactive substances. These contaminants can cause waterborne diseases such as cholera, hepatitis A, and dysentery, and they can also harm aquatic life, reducing their lifespan and ability to reproduce. The presence of these pollutants in water underscores the importance of addressing water pollution to protect human health and the environment.

Industrial and municipal wastewater

Industrial wastewater is a major source of water pollution, with serious environmental and health impacts. The escalating global population is causing a rapid expansion of the agricultural and industrial sectors, increasing the demand for water and leading to higher volumes of wastewater. Industries such as chemical, electric power, food processing, iron and steel, mining, nuclear, automotive, and paper and pulp are significant contributors to wastewater pollutants. These include high levels of biochemical oxygen-demanding (BOD) substances, total suspended solids (TSS), and total dissolved solids (TDS), as well as nitrate and phosphate from human and animal waste.

The toxicity of industrial wastewater stems from the presence of heavy metals, pesticides, plastics, paper, leather, wool, and other compounds. If untreated or inadequately treated, these pollutants can contaminate waterways, causing waterborne diseases such as diarrhoea, giardiasis, typhoid, cholera, hepatitis, jaundice, and even cancer. They also reduce the lifespan and reproductive abilities of aquatic organisms, accumulating in larger fish such as tuna.

Mining operations, for instance, generate waste rock and tailings, creating wastewater discharges that affect surface and groundwater quality. They can also cause extensive losses of aquatic and terrestrial habitats, impacting thousands of miles of streams and rivers.

Municipal wastewater also contributes to water pollution, with sewage, sludge, and other waste requiring proper treatment before discharge. Municipal wastewater contains similar BOD substances to industrial waste, which deplete oxygen levels in the water as bacteria break them down.

The challenges of managing industrial and municipal wastewater are significant, and there is no one-size-fits-all solution. Treatment methods must consider the water source, pollutant types, geography, budget, and available technology. However, efficient treatment can turn wastewater into a valuable source of energy and nutrients, such as using sludge for energy extraction and bio-solids, and phosphorus for fertilizer manufacturing.

Agricultural pollution

Agricultural activities introduce various pollutants to water bodies, including pesticides, fertilizers, and livestock manure. Pesticides are important for agriculture in the United States, and atrazine, for instance, is one of the most widely used and detected pesticides in surface water. About half a million tons of pesticides are applied annually to crops in the continental United States. Pesticide drift can be inhaled or come into contact with farmworkers spraying fields, and it can also contaminate their clothing and expose their families. Pesticides are toxic to insects, and their populations, such as the monarch butterfly and native bees, have declined due to these toxins.

Fertilizers and manure from livestock contain high levels of nutrients, such as nitrogen and phosphorus. When these substances are not absorbed by the crops, they can be washed away by rainfall and snowmelt, leading to nutrient runoff. This runoff can cause excessive algal blooms, which can be harmful to aquatic life and disrupt the ecosystem by blocking sunlight. Increased levels of nitrogen and phosphorus from fertilizer and manure can also lead to the development of hypoxic (low oxygen) conditions that are harmful to aquatic life.

Livestock manure is another significant source of agricultural pollution. Manure emits ammonia, which combines with other air pollutants to form harmful solid particles that can cause heart and lung diseases. Storing manure in exposed areas can also lead to phosphorus runoff, which can harm waterways. Additionally, manure contains bacteria that can contaminate water bodies and affect drinking water supplies.

Agricultural conservation practices can help mitigate these issues. For example, drip irrigation can reduce water loss and allow better control of pesticide and nutrient levels in irrigation water. Storing livestock manure in protected areas, such as lagoons or covered stockpiles, can minimize runoff risks. Implementing conservation practices tailored to specific critical source areas can effectively control multiple pollutants.

Marine debris

The sources of marine debris are diverse, with items being blown in by the wind, washed in via storm drains and sewers, or directly dumped into waterways by industries and individuals. Plastic pollution is a significant component of marine debris, with items such as bottle caps, balloons, lighters, plastic bags, and food wrappers commonly found in the ocean. These plastics can be mistaken for food by marine wildlife, leading to internal injuries, intestinal blockages, and death. Seabirds are particularly vulnerable, with plastic found in 90% of seabirds in a recent study.

Other types of marine debris include packing bands, balloon strings, rubber bands, six-pack rings, and mesh bags, which can lead to the entanglement and suffocation of marine animals. Derelict fishing gear and abandoned vessels are also significant contributors to marine debris, harming over 200 different species of marine life. The impact of marine debris extends beyond wildlife, as it can damage habitats, interfere with navigation, cause economic losses to fishing and maritime industries, and threaten human health and safety.

Addressing the issue of marine debris requires a combination of prevention, education, and cleanup efforts. The NOAA Marine Debris Program, for example, supports projects that raise awareness, change behaviours, and remove marine debris from shorelines and oceans. While individual behaviour change is important, it is also crucial to address the unsustainable consumption and production of disposable packaging and single-use plastic goods. By working together and taking collective responsibility, we can make a difference in reducing marine debris and protecting our oceans and marine life.

Oil spills

The response to an oil spill typically involves containing the spill and removing the oil to allow for the resumption of economic activities and the natural recovery of the marine environment. Techniques such as floating booms, skimming, and the use of sorbents are employed to separate and collect the oil. Chemical surfactants and solvents may also be used to accelerate the dispersion of the oil into the sea.

Microbiological contamination

Sources of microbial contamination can vary, with failing sewage disposal systems being a major contributor. This includes large municipal waste treatment systems, pump stations, and malfunctioning on-site sewage treatment systems. Additionally, runoff from animal waste in agricultural settings, such as barnyards, manure storage, and pastures, can introduce microbial contaminants into water supplies.

To protect against microbial contamination, it is crucial to develop watershed or wellhead protection programs. This involves controlling or eliminating microbial sources before they contaminate water supplies, making treatment more straightforward and cost-effective. Proper planning for sewage systems and regular inspections of septic systems are essential.

Water treatment plants employ methods like coagulation, filtration, and disinfection to remove microbial contaminants. While disinfection is effective against bacteria and viruses, certain protozoa like Cryptosporidium are highly resistant to chlorination alone and require additional treatment methods such as ozonation, UV disinfection, or advanced filtration techniques.

The presence of microbial contamination in water can be assessed through turbidimetry, which measures turbidity or the cloudiness of the water. However, this method has limitations, especially in karstic resources, where the variability of hydroclimatic conditions and the presence of particles can affect the accuracy of turbidity measurements.

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