Due to population growth, accelerated urbanisation and economic development, the quantity of wastewater generated and its overall pollution load are increasing globally. However, wastewater management is being seriously neglected, and wastewater is grossly undervalued as a potentially affordable and sustainable source of water, energy, nutrients and other recoverable materials. It therefore needs to be seen as a resource, rather than a burden to be disposed of.
There are many treatment processes and operational systems that will allow us to use wastewater to meet the growing water demand in growing cities, support sustainable agriculture, and enhance energy production and industrial development.
WASTEWATER AND CITIES
By 2030, global demand for water is expected to grow by 50 % 6. Most of this demand will be in cities and will require new approaches to wastewater collection and management. Indeed, reused wastewater may help address other challenges including food production and industrial development.
Mainly in low-income areas of cities and towns within developing countries, 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 addition to household effluent and human waste, urban-based hospitals and industries such as small-scale mining and motor garages, often dump highly toxic chemicals and medical waste into the wastewater system. Even in cities where wastewater is collected and treated, the efficiency of treatment may vary according to the system used. Traditional wastewater treatment plants may not remove certain pollutants, such as endocrine disruptors, which can negatively affect people and the ecosystem.
Examples:
• Dual distribution systems delivering reclaimed water. Since 1977 in St Petersburg, Florida, USA, a parallel network of pipes, separate from potable water mains, has served a mix of residential properties, and commercial and industrial parks, enabling them to use recycled water for irrigation, laundry, vehicle and building washing, and ornamental water features.
• Biologically purifying wastewater before discharging. The effluent volume from Schiphol Airport, Am-
6 UNHABITAT( 2016), World Cities Report 2016: Urbanization and development: http:// wcr. unhabitat. org / wp-content / uploads / sites / 16 / 2016 / 05 / WCR- % 20Full-Report-2016. pdf
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