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How Wastewater Can Slake Growing Thirst In Cities

Population and economic growth is piling pressure on freshwater resources, with demand rising faster than supply and yet 80 percent of global wastewater still goes to waste. Whether it’s at commercial or household level, not much thought is given to used water – dirty dishwater, flushed toilet water or industrial discharge.

But this shouldn’t be the case; used water should be reused and recycled as an alternative water source amid glaring future shortages. This is according to a new World Bank report dubbed Wastewater: From Waste to Resource.

Presently, 36 percent of the world’s population lives in water-scarce regions. Future forecasts paint an even grimmer picture in the age of climate change with more than half of the global population projected to be at risk of water stress by 2050.

Repurposing wastewater, the World Bank says, could offer countries an escape window out of the scarcity trap. Used water should not be considered a ‘waste’ anymore, but a resource. This is at the core of a circular economy – an economic system aimed at minimising waste and making the most of resources through innovative technologies.

Wastewater treatment offers a double value proposition, the report says. In addition to environmental and health benefits, water treatment can generate economic value through reuse in different sectors. Its by-products, such as nutrients and biogas, can be used for agriculture and energy generation, for instance. More importantly, safely managed water, sanitation and hygiene (WASH) services are essential in preventing disease and protecting human health during infectious disease outbreaks, including the current Covid-19 pandemic.

“Rapid urbanisation, especially in low- and middle-income countries, has created a host of water-related challenges. These include degraded water quality and inadequate water and sanitation infrastructure, particularly in expanding peri-urban and informal settlements. As cities continue to grow rapidly, and climate change alters the availability and distribution of water resources, it will become increasingly difficult and energy intensive to meet the water demands of populations and economies,” the World Bank says in the report aimed at equipping decision-makers with knowledge and tools to develop sustainable water policies.

“In this context, wastewater becomes a valuable resource from which water, energy, and nutrients can be extracted to help meet the population demands for water, energy, and food,” it adds.

The World Bank calls for a paradigm shift from traditional linear approach of water use where freshwater is harvested from surface or groundwater source, treated, used, collected and finally disposed. Such a linear model is no longer sustainable in light of modern challenges, the bank says.

Instead, the global lender says that to be climate-resilient, future cities would have to switch to models that minimise resource consumption and focus on resource recovery under circular economy.

The traditional approach is based on a linear economy with a “make, use, and dispose” model of production. On the other hand, a circular economy approach replaces the end-of-life concept with restoration, shifts toward the use of renewable energy, eliminates the use of toxic chemicals that impair reuse and return to the biosphere, and aims for the elimination of waste through the superior design of materials, products, systems, and business models. It’s based on three main principles – design out waste and pollution, keep products and materials in use, and regenerate natural systems.

The report sheds a light on wastewater management success stories, particularly in the Latin America and Caribbean (LAC) region, which are already reaping benefits.

Here are the examples:

  • By using treated wastewater instead of groundwater, the San Luis Potosi power plant in Mexico cut costs by 33 percent, leading to $18 million in savings over six years for the power utility. For the water utility, the additional revenue from selling treated wastewater helped cover operations and maintenance costs.
  • A wastewater treatment plant in Cusco, Peru, saves $230,000 a year in transporting biosolids (nutrient-rich organic materials resulting from the treatment of domestic sewage in a wastewater treatment facility) and landfill fees due to an agreement with the local compost producer. The compost produced with the plant’s biosolids is then used as part of the water management project to preserve the Piuray Lake.
  • Brazil-based CAESB water and wastewater utility’s use of biosolids for corn production led to higher-than-average grain yields and was 21 percent more efficient than mineral fertilizers.
  • The operator of the La Farfana wastewater treatment plant in Santiago, Chile, after investing $2.7 million to retrofit the plant, was able to sell biogas, accounting for an annual net profit of $1 million for the business.

“Wastewater can be treated to various qualities to satisfy demand from different sectors, including industry and agriculture. It can be used to maintain the environmental flow, or even reused as drinking water. Wastewater treatment is one solution to the water scarcity issue, and also to the problem of water security, freeing water resources for other uses or for preservation,” World Bank says in the report.

“The diversification of water supply sources is critical for enhanced security and resilience, and wastewater should be considered as an additional source when estimating water balances. Meanwhile, the by-products of wastewater treatment can become valuable for agriculture and energy generation, making wastewater treatment plants more environmentally and financially sustainable. Treating wastewater as a valuable resource can thus contribute to a region’s sanitation sector, as well as its major economic sectors,” the global lender adds.

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