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Recycling – The future urban sink for wastewater and organic waste
Summary
Researchers analyzed how recycling urban wastewater and organic waste as agricultural fertilizer could become a sustainable solution for feeding a growing global population, finding that keeping nutrient-rich sewage separate from chemically contaminated greywater is essential to making this work. The analysis suggests that cities could replace environmentally damaging phosphorus and potassium mining with urban waste recycling if infrastructure is redesigned accordingly.
Illustration of urban water exchange with the atmosphere (evapotranspiration, transpiration, precipitation), surface water (lakes, rivers and runoff), ground/soil (runoff, infiltration. withdrawal), and reuse/recycling of used water. Nutrient exchange ( green italics ) comprises mainly food and nonfoodnutrients, excreta and biowaste, and the reuse/recycling of nutrients. • Recycling has the potential as the future sink for wastewater and organic waste. • A separate sewer for blackwater ensures better-quality sludge and fertilizer. • Urban-derived fertilizers can replace the polluting activity to mine P and K. • Urbanization facilitates resource-smart cities in the 21st Century. The world’s population is estimated to reach 11 billion in this century, with some 8.5 billion living in urban areas. Cities become unprecedented hot spots of demand for virgin water and food, as well as producers of large volumes of valuable waste. The recycling of urban nutrient-rich liquid and solid waste as fertilizer in agriculture will thus be of benefit to both sectors. The analysis suggests that recycling has the potential to become the ultimate sink for organic waste and wastewater, while simultaneously securing the supply of food and fertilizers, and reducing both local and global environmental impacts. Presently, harmful chemical substances from various consumer products in our chemical society are disposed of in urban waste flows and hamper recovery and reuse. A combination of counter measures such as not mixing nutrient-rich blackwater with grey water polluted with chemical compounds, are crucial. The sludge from the small volume of blackwater can contribute enough fertilizers to secure global food supplies by the year 2100. The voluminous grey water will contain few pathogenic microorganisms and can be treated for non-potable reuse. Three urban arrangements are analysed: Singapore (entire city), Helsingborg in Sweden (city district), and Bangalore in India (eco-house).
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