Wastewater is any form of used water. This includes water used for domestic purposes (e.g. water from sinks, showers, bathtubs, toilets, washing machines and dishwashers), used water from agriculture and industries, as well as stormwater runoff (rainwater that washes down streets and picks up harmful bacteria before ending up in lakes and rivers).
The majority of economically advanced industrialised countries have wastewater treatment systems in place which treat and purify used water before releasing it back into the environment. But in many nations, these systems aren’t in place and untreated water flows back into the environment and pollutes natural water sources. Even in developed countries, not all water is treated and some used water ends up infiltrating supplies.
According to the UN World Water Development report on wastewater in 2017, around 80% of water used globally goes back into the environment untreated. There are big differences between industrialised and developing nations. Countries classed as high income (e.g. the US, Australia, Belgium) treat 70% of used water on average. This falls to 28-38% in middle income countries (e.g. Brazil, Bulgaria, Nigeria, Pakistan) and only 8% in low income countries (e.g. Nepal, Rwanda, Afghanistan).
There are differences between high income countries. The Netherlands treats 99% of its wastewater, Germany 97% and Belgium 84% (up from 41% in 2000). This suggests that it’s not just developing nations where more could be done. You can compare figures between countries on the OECD database and look at country and regional profiles for middle and low income nations here.
Allowing wastewater to return into the environment untreated has negative effects on the environment, human populations and the global water supply.
Untreated water released back into the system can have devastating effects on the environment. Wastewater includes contaminants such as chemical compounds and pathogens than can cause harm to fisheries and wildlife habitats as well as aquatic ecosystems.
The pathogens in wastewater can also contaminate crops and drinking water. Waterborne illnesses from contaminated freshwater supplies are a common problem in developing countries without adequate sanitation. This is detrimental to health and well-being as well as having knock-on effects on productivity, education and inequality.
Freshwater is a finite resource and if we don’t do all we can to preserve it, we increase the risk of a global water scarcity crisis in decades to come. Treating and purifying wastewater means that it can be returned to the water cycle or reused as a primary water source.
The 2017 UN report identified treated wastewater as a valuable untapped alternative water source that can play an important role in averting a crisis if systems are improved worldwide. This includes improving water treatment and recycling in high income nations as well as addressing issues in poorer regions. Improving wastewater recycling is cost-efficient as reused wastewater is cheaper than using freshwater. Having more on-site treatment and recycling technologies could also eliminate a lot of water transportation costs.
Improving water treatment processes across the world can have a positive effect on the environment, human health and global water supplies. This means dealing with the problem of large-scale untreated wastewater in lower income countries as well as utilising new technology to improve treatment and recycling methods in higher income countries.
The current UN sustainability goals aims to halve the proportion of untreated wastewater and substantially increase global recycling and safe water reuse by 2030. As we push towards a circular economy, where economic progress is balanced with sustainability and environmental protection, wastewater could have a crucial role to play in years to come.
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