World Water Day (WWD) is about taking action on water issues. It focuses attention on the importance of freshwater and advocating for the sustainable management of its resources. Held on 22 March, World Water Day tackles a specific aspect of freshwater each year, raising awareness of what society can do to help make clean water more accessible. The theme of 2017 is "Why waste water?" which focuses on reducing and reusing wastewater.
Wastewater is any water that has been adversely affected in quality due to human activity. The vast majority of all wastewater from our homes, cities, industry and agriculture returns back to nature without being treated or reused. This causes mass pollution to the environment, while losing valuable nutrients and other recoverable materials – so instead of wasting water, we need to be reusing it.
The Sustainable Development Goal 6 target aims to halve the proportion of untreated wastewater and to increase water recycling and safe reuse by 2030 – and by then the global demand for water is expected to grow by 50%.
The UN target aims to help improve water quality by reducing pollution, eliminating dumping, minimising release of hazardous chemicals and materials and to substantially increase recycling and safe reuse globally. In doing this, it will help us to achieve safe water and sanitation, affordable and clean energy, sustainable cities and communities, while improving life on land and in the sea.
According to the WWD organisation, more than 80% of the wastewater generated by society flows back into the ecosystem without being treated or reused. There are roughly 663 million people who still lack improved drinking water sources. Some 1.8 billion people use a source of drinking water contaminated with faeces, putting them at risk of contracting cholera, dysentery, typhoid and polio. Unsafe water, poor sanitation and hygiene cause around 842,000 deaths each year.
It is mainly in low-income areas of cities and towns within developing countries, that a large proportion of wastewater is discharged directly into the closest surface water drain or informal drainage channel, sometime without or with very little treatment.
In our homes, grey water (relatively clean water that has been used in baths, showers, washing machines and sinks) can be used on our gardens, plants and plots. About a third of household water is used for flushing the toilet; greywater can be collected in a household-scale reuse system and treated to a standard that is suitable for toilet usage. Untreated greywater can be used for garden watering if used immediately after it is produced – soil is effective at filtering out many contaminants in grey water. However, wastewater from kitchen sinks and dishwashers should not usually be collected as it is too heavily contaminated.
In our cities, we can treat and reuse wastewater for green spaces and in our industries and agriculture, we can treat and recycle discharge for things like cooling systems and irrigation. By using this valuable resource, we will make the water cycle work better for every living thing. It is thought that by 2050 nearly 70% of the world's population will live in cities, compared to 50% today, the WWD organisation has stated. At the moment most cities in developing countries do not have adequate infrastructure and resources to address wastewater management in an efficient and sustainable way. Cities will require new approaches to wastewater collection and management.
Improved wastewater management can improve the health of workers, especially in agriculture, by reducing the risk of pathogen exposure. It can also create direct and indirect jobs in water-dependent sectors and beyond.
It has been estimated that more than 40,000-60,000 km of land is irrigated with wastewater or polluted water posing health risks to farmers and to eventual consumers of the agricultural products. Available technologies allow removal of almost all contaminants from wastewater, making them suitable for every use. The WHO Guidelines on Safe Use of Wastewater in Agriculture and Aquaculture and the Sanitation Safety Planning (SSP) approach provides a comprehensive framework to ensure that health risks are managed to protect public health. Israel paves the way, where treated wastewater accounts for 50% of irrigation water.