Water in an increasingly polluted world

How much do you know about water? It’s all around us and used in pretty much all human activities. This might be as simple as washing our face or as complex as being used in the development of semiconductors for our electronic devices. But how many of us really know the impact of our behaviours on water? What sort of water pollution do we generate? What challenges are we facing in trying to provide all enough clean water for human activity? IMSE’s latest guest blogger, Bioengineering student Naveesha Karunanayaka, explores the topic.

Water covers 70% of the Earth’s surface and the oceans make up 97% of all water on Earth. Despite the ocean being divided up into segments by scientists, it’s just one big body. So, if a few drops of waste enter one area of it, the whole body will be affected, eventually, due to diffusion. Something we want to avoid, as less than 1% of the Earth’s freshwater is accessible. So, we want to ensure we maximise its usability as well as minimise any negative impacts on the ecosystems.

The first step to avoid polluting our precious water supply is to understand what harmful substances may be going into it. Because water is a “universal solvent”, dissolving more substances than any other liquid in the world, means it’s susceptible to contamination by a very wide variety of molecules. Some key sources of pollution include agricultural, sewage and wastewater and oil pollution. Pollution comes from urban and rural areas alike.

Water pollution from agriculture

The main contributors to water pollution from agriculture are phosphorous and nitrogen. These can cause an imbalance of nutrients in water and lead to eutrophication, which is rapid biological ageing of bodies of water. For example, an agal bloom can suffocate the water of oxygen, resulting in waters devoid of life. Sometimes these blooms can release neurotoxins that also negatively affect marine animals.

Water Cycle with Earth's environment (sun, clouds, mountains, ground)
Hydrologic cycle showing water through the Earth and atmosphere. Image credit: NASA https://climate.nasa.gov/explore/ask-nasa-climate/3143/steamy-relationships-how-atmospheric-water-vapor-amplifies-earths-greenhouse-effect/

The main source of phosphorous and nitrogen is fertilisers, necessary for crop growth. Nitrogen is also deposited into the environment out of the air. This comes from ammonia evaporated from animal manure and from NOx from the combustion of fossil fuels. Agriculture contributes 50-80% of all nitrogen pollution.

Phosphorus isn’t found in the air and mostly circulates in the water system. Phosphorous is mainly found in the form of phosphate, PO43-. Agriculture contributes between 25-75% of phosphorous pollution, usually around half of it.

Dirty water is a global crisis

In 2021, the UN reported that of more than 75,000 bodies of water surveyed across 89 countries, more than 40% were severely polluted. So it’s unsurprising that around the world, 1 in 3 people don’t have access to safe drinking water. Predominantly this affects less developed countries such as those in Africa, Latin America or some parts of Asia. Papua New Guinea and Eritrea are amongst countries with the lowest access to clean water close to home. This is correlated with them also being amongst the poorest countries in the world.

Polluted Water with rubbish. bags, plastics and discoloured water.
Water pollution near Dakshinkali temple in Nepal. Photo by Anil Raut via flikr

Contaminated water has serious consequences for humans, not just for ecosystems. But collection, storage and distribution of freshwater is expensive and requires major investment over the long term. The same is true for building and running sanitation systems which collect, store and treat contaminated water.

Water pollution is a multidisciplinary challenge

Molecular science and engineering is essential to delivering clean water for everyone. Molecular science is needed to understand the nature of water pollutants and to design technologies for freshwater collection and water treatment systems. This needs to be combined with engineering thinking to ensure that potential new technologies are genuinely scalable. This means they need to be affordable and sustainable at the scale and in the locations where they are needed.

Read more about multidisciplinary approaches to clean water on the IMSE blog:

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