Water Pollution | 1 of 2

Also, if you are interested in listening to this episode instead, here is the link to it: Water Pollution | 1 of 2

What is water pollution?

Water pollution (or aquatic pollution) is the contamination of water bodies, usually as a result of human activities, in such a manner that negatively affects its legitimate uses. Water bodies include for example lakes, rivers, oceans, aquifers, reservoirs, and groundwater. Water pollution results when contaminants are introduced into these water bodies. For example, releasing inadequately treated wastewater into natural waters can lead to the degradation of these aquatic ecosystems. All plants and organisms living in or being exposed to polluted water bodies can be impacted. The effects can damage individual species and impact the natural biological communities they are part of. Water pollution can also lead to water-borne diseases for people using polluted water for drinking, bathing, washing, or irrigation.

Water pollution can be classified as surface water pollution (for example marine pollution) or groundwater pollution. Sources of water pollution are either point sources or nonpoint sources. Point sources have one identifiable cause, such as a storm drain or a wastewater treatment plant. Nonpoint sources are more diffuse, such as agricultural runoff. Pollution is the result of the cumulative effect over time.

The causes of water pollution

The causes of water pollution include a wide range of chemicals and pathogens as well as physical parameters. Contaminants may include organic and inorganic substances. Heat can also be a pollutant, and this is called thermal pollution. A common cause of thermal pollution is the use of water as a coolant by power plants and industrial manufacturers.

Types of water pollution

Surface water pollution

Surface water pollution is an everyday thing around us.

It includes the pollution of rivers, lakes, and oceans. A subset of surface water pollution is marine pollution which affects the oceans. Nutrient pollution refers to contamination by excessive inputs of nutrients.

Globally, about 4.5 billion people do not have safely managed sanitation as of 2017, according to an estimate by the Joint Monitoring Programme for Water Supply and Sanitation. Lack of access to sanitation often leads to water pollution, e.g. via the practice of open defecation: during rain events or floods, the human feces are moved from the ground where they were deposited into surface waters. Simple pit latrines may also get flooded during rain events.

When sewers overflow during storm events this can lead to water pollution from untreated sewage. Such events are called sanitary sewer overflows or combined sewer overflows.

Marine pollution

Marine pollution occurs when substances used or spread by humans, such as industrial, agricultural, and residential waste, particles, noise, excess carbon dioxide or invasive organisms enter the ocean and cause harmful effects there. Since most inputs come from land, either via the rivers, sewage, or the atmosphere, it means that continental shelves are more vulnerable to pollution. Air pollution is also a contributing factor by carrying off iron, carbonic acid, nitrogen, silicon, sulfur, pesticides, or dust particles into the ocean. The pollution often comes from nonpoint sources such as agricultural runoff, wind-blown debris, and dust. Land and air pollution have proven to be harmful to marine life and its habitats.

A particular concern is a runoff of nutrients (nitrogen and phosphorus) from intensive agriculture, and the disposal of untreated or partially treated sewage to rivers and subsequently oceans. These nitrogen and phosphorus nutrients (which are also contained in fertilizers) stimulate phytoplankton and macroalgal growth, which can provide more food for other marine life, but in excess can lead to harmful algal blooms (eutrophication) which can be harmful to humans as well as marine creatures. Such blooms are naturally occurring but may be increasing as a result of anthropogenic inputs or maybe something that is now more closely monitored and so more frequently reported. Excessive algal growth can also smother sensitive coral reefs and lead to loss of biodiversity and coral health. A second major concern is that the degradation of algal blooms can lead to the depletion of oxygen in coastal waters, a situation that may be exacerbated by climate change as warming reduces vertical mixing of the water column.

Groundwater pollution

Groundwater pollution (also called groundwater contamination) occurs when pollutants are released to the ground and make their way down into groundwater.

The pollutant often creates a contaminant plume within an aquifer. The movement of water and dispersion within the aquifer spreads the pollutant over a wider area. Its advancing boundary, often called a plume edge, can intersect with groundwater wells and surface water, such as seeps and springs, making the water supplies unsafe for humans and wildlife. The movement of the plume, called a plume front, may be analyzed through a hydrological transport model or groundwater model. Analysis of groundwater pollution may focus on soil characteristics and site geology, hydrogeology, hydrology, and the nature of the contaminants. Different mechanisms influence the transport of pollutants, e.g. diffusion, adsorption, precipitation, decay, in the groundwater.

The interaction of groundwater contamination with surface waters is analyzed by the use of hydrology transport models. Interactions between groundwater and surface water are complex. For example, many rivers and lakes are fed by groundwater. This means that damage to groundwater aquifers e.g. by fracking or over-abstraction could therefore affect the rivers and lakes that rely on it. Saltwater intrusion into coastal aquifers is an example of such interactions. Prevention methods include: applying the precautionary principle, groundwater quality monitoring, land zoning for groundwater protection, locating on-site sanitation systems correctly, and applying legislation. When pollution has occurred, management approaches include point-of-use water treatment, groundwater remediation, or as a last resort, abandonment.

The Impacts of water pollution

To ecosystems

Water pollution is a major global environmental problem because it can result in the degradation of aquatic ecosystems. The specific contaminants leading to pollution in water include a wide spectrum of chemicals, pathogens, and physical changes such as elevated temperature.

Public health and waterborne diseases

In 2015 the World Health Organization (WHO) estimated that “1 in 3 people, or 2.4 billion, are still without sanitation facilities” while 663 million people still lack access to safe and clean drinking water. In 2017, this estimate changed to 2.3 billion people without sanitation facilities and 844 million people without access to safe and clean drinking water.

Lack of sanitation contributes to about 700,000 child deaths every year due to diarrhea, mainly in developing countries.

Now, these are serious problems and people are thinking of ways to solve them. And I will be introducing some of the efforts people have made towards cleaner water in the next episode.