VIENNA, 22 March - Today is World Water Day, coordinated by UN-Water in collaboration with governments and partners. The theme this year is wastewater. To mark the day, the United Nation's flagship report, The United Nations World Water Development Report 2017: Wastewater: The Untapped Resource, is published.

The chapter contributed by UNIDO describes the extent and nature of industrial wastewater production. It also highlights the opportunities from the use and recycling of wastewater and the recovery of energy and useful by-products when addressing natural resource challenges in the context of sustainable industrial development.

The extent of industrial wastewater generation largely unknown. Globally, data and information concerning the volume of wastewater produced by industry are very deficient. However, some consolidated information is available. In the European Union, for example, limited data show that wastewater generation has generally decreased.

The data also show that manufacturing is the greatest generator of wastewater among the main industrial sectors (the others are mining and quarrying, the production and distribution of electricity and construction). Furthermore, data from a few countries indicate that industry is a major polluter, as only a proportion of wastewater is treated before being discharged.

Widely varying industrial activities produce wastewater, which is characterized by a broad spectrum of pollutants. Technology is available to remove (or ‘mine’) these pollutants and is only limited by its cost-effectiveness in given industrial situations. This creates two products: the treated water and the materials recovered.

The water may be recycled within a plant or by another linked industry, or it may be simply discharged, returning it to the hydrological cycle for others to use. In the USA, it has been estimated that for some major rivers the water has been used and reused over 20 times before it reaches the sea. Useful materials may be recovered, such as minerals (phosphates) and metals. Cooling water may provide heat. Residual sludge might yield biogas or may have no other fate than disposal.

As with many environmental issues, the first step is to prevent or minimize pollution. The goal is to keep the volumes and toxicity of pollution to a minimum at the point of origin. This goes to the core of new green industrial engineering, where the elimination of pollution and wastewater is part of the equation from concept to design for operations and maintenance. However, with established plants, while some re-engineering is possible, pollution reduction might be the only option. This includes substitution with more environmentally friendly raw materials and biodegradable process chemicals, as well as staff education and training to identify pollution issues and remedy them.

Overall, industry is in a good position to use or recycle its wastewater internally. This might involve the direct use of untreated wastewater, provided its quality is good enough for the intended purpose. Cooling and heating water, as well as rainwater, may be suitable for washing, pH adjustment and fire protection. However, process water which is sufficiently treated to match resulting quality with intended purpose has more potential for recycling, for example in conveying materials, rinse water, water-cooling towers, boiler feed, production line needs, dust suppression, and washing.

Click here for more about using wastewater or recycling treated wastewater in the context of industrial symbiosis and eco-industrial parks, and about UNIDO’s cleaner production initiatives that focus on reducing overall water use, closing the water cycle, and eliminating wastewater discharge.

by Charles Arthur