H2O Innovations: A Steady Flow of Solutions to Tackle the Global Water Crisis

Global water scenarios in the current and coming decades certainly sound dire, but then so do food and energy forecasts. More than 750 million people in the world today lack access to clean drinking water. That figure could triple as our population grows to more than 9 billion people by 2050, which is estimated to translate into a 55 percent increase in water demand. To feed everyone, food production must double and crop irrigation demands will rise. Energy production will also have to expand, but freshwater access is key to energy production. At the same time, water treatment and delivery require energy. Clearly, water sits at the intersection of all the critical issues facing humanity, which themselves are interdependent and currently out of sync.

Increasing groundwater extraction from the deep aquifers in the US is leading to a significant decline of groundwater stocks that are used to buffer droughts. Upmanu Lall and his group are working on solutions for overall water management that can reverse this trend. (Image courtesy of Columbia Water Center)

Upmanu Lall is calling for a coordinated plan to ensure a reliable supply of water, energy, and food of appropriate quality for all life around the world by 2050. Policy makers have yet to launch a successful plan of action to this end. Despite the preceding figures, Lall, the Alan and Carol Silberstein Professor of Engineering and director of the Columbia Water Center, and his colleagues are still optimistic about the world’s future water prospects—a future that simultaneously can address growing food and energy shortages.

To be sure, the deeper one digs, the more daunting these contemporary water challenges can seem, especially when viewed as part of the so-called water-food-energy-climate nexus. Under a business-as-usual scenario, global water demand will outstrip available supply by 40 percent by 2030, according to a 2015 report by the United Nations. Water infrastructure in much of the Western world has reached the end of its intended design-life, the replacement of which in the United States alone could cost $1.7 trillion by 2050 if it is to keep up with population growth. In the developing world, much infrastructure is in a state of disrepair, if it exists at all.

Innovation in Water Sustainability
Clearly, it’s time for a paradigm shift, and several Columbia Engineering researchers are at the forefront of efforts to design for sustainable water. “Suppose we were going to start at zero,” Lall said, “and we’re going to spend all this money [to address inadequate water systems]. What would you rather do? What would your infrastructure be? We seem ready to spend over a trillion dollars to replace our water infrastructure without a serious effort to design systems to address 21st century needs using innovative technologies.” Patricia Culligan, professor of civil engineering and engineering mechanics, has headed up several projects that ask similar fundamental questions. For instance, would it make sense to combine distributed infrastructure elements with new and extant centralized infrastructure elements?

In most urban areas in the developed world, utilities rely on massive and centralized collection, delivery, treatment, and sewage systems. Rather than replacing today’s cracked and corroded pipes and other elements of these systems at high expense, water collection and treatment could be performed more locally, in a more distributed fashion. Utilities could also integrate rainwater harvesting, local groundwater usage, point-of-use treatment, and water reclamation and reuse.

An engineered green roof in New York City (Photo by Daniel Marasco)

Wastewater treatment, in particular, begs for rethinking and redesign. For instance, during extreme weather events, sewage pipes overflow with added storm water runoff, resulting in wastewater dumping into local bodies of water or the ocean. In cities in developing countries, and in other areas lacking such infrastructure, dumping of wastewater occurs daily, polluting local surface water and groundwater. Some communities have built so-called green infrastructure (GI) to mitigate this pollution, rather than simply expanding treatment plants and laying more pipe. Green roofs, green streets, rainwater gardens, and bioswales can absorb storm water runoff, while also cooling city blocks suffering from the urban heat-island effect during hot summers.

Culligan, who also codirects Columbia’s Urban Design Lab and is associate director of Columbia’s Data Science Institute, is very interested in the role that distributed infrastructure might play in mankind’s future. She is leading a Columbia University team that is part of a $12 million project funded by the National Science Foundation (NSF) aimed at assessing how innovations in infrastructure design, technology, and policy can increase the sustainability, health, and livability of the world’s cities. Culligan herself is focusing on the role of GI in preventing urban wastewater overflows, which are responsible for almost half of the pollution that goes into our rivers, lakes, and coastal water bodies. Increased decentralization of wastewater treatment through the widespread adoption of GI solutions could take the pressure off old municipal systems or enable new waterworks on a smaller scale in densely populated regions where a vast system is unattainable.

“A hybrid approach of centralized and decentralized infrastructure is necessary both in cities with aging infrastructure, like New York, and in rapidly growing urban settlements where significant numbers of people live without any infrastructure at all,” said Culligan. Hybrid approaches, including solutions involving district energy systems, community solar energy, light rail, and localized urban food systems, offer opportunities for greater resource efficiency, including the better use and protection of our water resources.

Biofilm growth of complex microbial community capable of energy-efficient nutrient removal from nitrogen enriched “waste” streams (Photo by Jeffrey Schifman)

Recycle, Reuse
Water reuse systems with broad social impact are the research focus of Kartik Chandran, professor of earth and environmental engineering. He conceives of wastewater, or sewage, as exploitable enriched water rather than a repulsive by-product that requires disposal. At the same time, he questions whether it makes sense to clean wastewater to drinking water quality and then to use it for irrigation and dilution of waste streams. These insights have inspired Chandran and his colleagues to build bioreactors teeming with complex microbial communities that thrive on the waste we flush. The nitrogen cycling within these systems can remove pathogens and harmful chemicals as well as convert sewage into fertilizers, commodity chemicals, and energy sources.

Chandran’s systems potentially can serve both the water and sanitation needs of billions of people on Earth who live in sprawling slums and lack access to piped water systems. “Some of our technologies are meant to take that [scarcity] out of the equation but still provide them with clean water, still provide them with sanitation,” Chandran said.

Several years ago, Chandran helped New York City officials expand the capacity of five of its existing 14 wastewater treatment plants, in anticipation of the area’s burgeoning population. He designed systems including bioreactors that removed from sewage not only carbon but also nitrogen pollution, a highly potent greenhouse gas. He has gone on to devise and optimize systems in locations such as the Chesapeake Bay and Los Angeles, and also in a remote region in Ghana where the only available resource was a continuous supply of truckloads of fecal sludge. Again applying his knowledge of microbial communities’ consumption patterns, his system there derived some of the chemicals and energy required for treatment from the sludge itself, thereby offsetting a percentage of the required chemical and energy inputs.

From Water to Food to Energy and More
That link between water management and improved energy efficiency is no accident. More communities and policy makers in recent years have seen the connections between water treatment, energy use, food production, climate change, and business. Trade-offs that improve one sector at the expense of another no longer make sense.

Cross-sectional scanning electron microscope image of a polymeric membrane. Membranes are at the heart of reverse osmosis technology, allowing only water to pass through while selectively filtering salts and other impurities. (Image courtesy of Ngai Yin Yip)

For instance, one innovation being embraced particularly in arid, highly water-scarce parts of the world is desalination—using reverse osmosis techniques to draw seawater through specialized polymeric membranes to filter out salt, yielding clean freshwater. Half of the world’s population lives about 60 kilometers from a coastline, affording access to abundant seawater. However, desalination is energy intensive compared with other water collection and treatment methods.

Ngai Yin Yip, assistant professor in the department of earth and environmental engineering, studies the fundamental mechanism behind the transport of seawater through the membrane material. The goal is to use those insights to develop another material that desalinates more efficiently, likely in the range of a 5 percent to 30 percent improvement in performance. “Because the global desalination market is over tens of billions of dollars, even 5 percent will translate into a huge increase in productivity and cost reduction,” Yip said.

All these water collection and treatment innovations certainly are essential, but a sobering fact remains. Consumptive water use, or use of water that is removed from the system and never replaced at the source, is dominated by agricultural and irrigation needs, followed by energy production needs. Yet, the water efficiency opportunities for irrigation and agriculture are seemingly obvious: reduce leaks in irrigation pipes, bank water, install drip irrigation and soil-moisture sensors, develop more water-efficient and drought-tolerant crops through breeding and genetic modification, optimize application of fertilizers, implement plant-growth regulation techniques. Policy makers have adopted some of these “more crop per drop” solutions, but have not come close to exploiting their full potential.

Why haven’t these approaches been put in place? Governance, said Lall, who has worked on myriad water systems all over the world. Whether it’s in India or the United States, intelligent incentives, regulations, and enforcement tailored to local conditions typically are not in place. “So, we don’t have a water crisis. We have a situation that is solvable,” he said.

Like his colleagues, Lall advocates closed loop systems for energy, food, and water infrastructure and more reliance on renewable energy sources, which require dramatically less water to produce and deliver than fossil fuel–sourced energy. Increased free trade, he said, can also give nations and communities in emerging markets the cash necessary to invest in long-term, integrative, and sustainable water solutions, not to mention a higher standard of living.

For Chandran’s part, his optimism feeds on many sources, including the success of his team’s colorful bioreactors happily feasting on human and food waste in his labs on the ninth and tenth floors of the Mudd Building. It also helps that his graduate students share his drive to address social and environmental challenges. Every member of his introductory wastewater treatment design course last fall came up with novel systems for improving water quality that also used less energy than conventional approaches and recovered nutrients that industrialists and farmers alike desperately need.

—by Robin Lloyd


WATER


H2O Innovations: A Steady Flow of Solutions to Tackle the Global Water Crisis