The ROI of Water: Capturing triple-bottom line benefits with circular water management

Many cities continue to see water management in terms of linear supply and demand. But it can instead be a circular process, one where emphasis is placed on the reduction, reuse, recycling, and recovery of water.

Yet with global demand for water projected to exceed supply by 40% in 2030, there is considerable importance for cities to implement solutions that use a circular approach to managing water. Those that are doing so are on the path to creating a water optimized future for their citizens.

The Economist Impact’s City Water Optimization Index, sponsored by DuPont, offers insight into how well cities around the world are ensuring the reliability, accessibility, and sustainability of water resources for their inhabitants. The results – evaluated across 47 indices – were remarkably positive, with many of the 51 cities able to deliver quality drinking water and robust water connectivity systems. However, many cities still struggle with achieving high marks in the sustainability category and using circular water management best practices.

Not only does going beyond reliability and accessibility ensure water optimization for future generations, but it can also reap triple-bottom line benefits for forward-looking cities.

According to a United Nations brief from 2020, the amount of globally produced wastewater is five times the volume that runs over Niagara Falls each year. That’s an enormous and valuable source of water simply wasted. According to the United Nations, over 80% of this wastewater flows back into the ecosystem without being treated or reused.

This water could instead be reclaimed and reused, for drinking and other applications that can contribute to environmental sustainability, produce renewable energy, and over time, pay for themselves. One way is to recover the nutrients in wastewater for use in agriculture; the same UN report states that the full nutrient recovery would offset 13.4% of the global agricultural demand for nutrients used in fertilizer. Another is to extract biogas from fermentation of organic waste in sewer sludge and convert it to electricity through cogeneration.

How It Works: Nutrient Recovery for Fertilizer

Phosphorus and nitrate are two beneficial nutrients that can be recovered in wastewater. Two of the main ingredients in commercial fertilizer, phosphorus and nitrate are essential for growth and food production in large-scale agriculture. However, used in excessive quantities they can contribute to toxic “dead zones,” giant algae blooms caused by fertilizer run off and discharge into rivers, lakes and oceans.

Treating wastewater to recover these nutrients creates a much more environmentally friendly “slow-release” fertilizer that does not create as much runoff when not absorbed immediately by plants. Recovering nutrients from wastewater creates a triple-bottom line opportunity for cities: first, less water is used in fertilizer production and can be diverted to consumption; second, area watersheds are less polluted due to diminished fertilizer run-off; and third, cities can sell their recovered wastewater fertilizer to local agricultural operators.

How it Works: Biogas Recovery for Electricity

In wastewater treatment facilities, biogas can be created by breaking down organic matter found in sewage sludge using anaerobic digestion. Biogas, a mix of carbon dioxide and methane, can then be combusted in a combined heat and power (CHP) plant to generate electricity to power the wastewater facility itself while excess electricity can be sold back to the grid. Not only does this provide a renewable and reliable source of energy to produce electricity, but also captures the methane and CO2 released into the atmosphere by treating wastewater – both potent greenhouse gases – and recycles it into clean energy.

In the U.S. alone, if every wastewater treatment plant used the biogas they produced instead of flaring it as more than half of those using an anaerobic digester do, the country could reduce annual CO2 emissions equivalent to 430,000 cars each year.

City Spotlight: Santiago

The country of Chile has faced a megadrought for more than a decade, causing aquifers around the capital city, Santiago, to dry up at an alarming rate. Glacial retreat due to higher temperatures is decreasing the amount of water serving the region while nearby Aculeo Lake is completely dry.

Even in these dire circumstances, Santiago is providing nearly 100% connectivity for drinking water and sewer system coverage, the Economist team found. Most impressively, the city was ranked in the top 10 in the Index’s Sustainability category – and ranked well ahead of the average sustainability score, even higher than much wealthier cities such as Dallas and Lisbon, Portugal. How is Santiago doing it?

As recently as fifteen years ago, only a fraction of the city’s wastewater was treated; the rest was discharged – untreated – into the nearby Mapocho River, a key source of potable water for the area. Fast forward to today where, after the construction of the largest wastewater treatment plant at the time in Latin America, 100% of all wastewater is treated, providing multiple benefits to the city’s nearly seven million residents – electricity generated by biogas, revitalized rivers and urban areas, and fertilizers produced from biosolids. The city’s water and sanitation company, Aguas Andinas, has a goal to be zero waste and carbon neutral by 2022 across all three of the wastewater treatment plants it operates. A World Bank study found that in 2017, the company netted $1 million in profits from the sale of biogas, helping offset the $6 million capital investment in the project shared between Agua Andinas and the local gas provider.

Circular water management offers an important opportunity for city and business stakeholders to collaborate across sectors, reap multiple benefits and bring about a water optimized future.

Kimberly Kupiecki is the Director and Global Leader, Sustainability, Advocacy & Communications for DuPont Water Solutions. She is also a writer and a blogger at www.kimmiebean.com