Finding water fit to drink: technology delivers the best solution
By Madelynn O’Leary
On a blistering day in late summer 2004, seven women trudged single-file down a dusty hill to fill up plastic containers from a reservoir. They'd set out from Paredones, Mexico, a hamlet of 70 people who barely had enough water to drink, much less flush toilets regularly, bathe, wash clothing and clean their homes — it wasn’t uncommon in many small communities in Mexico’s Tehuacán Valley, southeast of Mexico City. The women collected the water, hoisted some of it on two mules, the rest over their shoulders, then made the return climb. Coming into the village they found people gathered around a man who’d come from Mexico’s Ministry of Hydraulic Services to tell the villagers that a government engineer would be bringing men to install a galeria filtrante – a horizontal well – in the hills above the village. It was a technology that predated the modern era, but it would make life better in Paredones.
The well was in fact a tunnel, tilted slightly down from the horizontal. It tapped ground water in the hills, and gravity flow did the rest. The women would no longer have to make their daily trip, but the people of Paredones still had to rely on another old technology, biofiltration, which the Ministry had brought to the hills years before.
The biofilters were nothing more than a layer of gravel on sand in a box made from native materials. A delicate film (schmutzdecke) would form on the surface of the sand after several uses, improving the filtration process as water seeped through the sand. The devices removed most but not all of the harmful microbes – the water wasn’t perfect, but it was good enough.
By the time the men of Paredones returned from their seasonal work on farms in the U.S., the Ministry’s engineers had prepared 500 sites for galerias in the Tehuacán Valley. But that wasn’t the big news.
An American named John Hayes showed up in the valley not long after Paredones got its galeria filtrante. He was a balding, serious-looking man, an inventor who had created a handheld purification unit that could provide drinking water for individual residences or groups of homes. He’d developed devices of different sizes – the largest could supply drinking water to a community of 5,000. The stop in Chandiablo was the first of 34 that Hayes made in Mexico’s Colima region, where he delivered the device, free of charge, wherever good drinking water was scarce.
People like Hayes were helping technology catch up to the problems that water shortages caused in remote areas like Paredones. It was the kind of progress that Walt Weber would applaud. Weber is the Gordon M. Fair and Earnest Boyce Distinguished University Professor of Environmental Science and Engineering and the author of books such as Physical Chemical Processes for Water Quality Control. He said that providing safe drinking water to all people, everywhere, “is clearly the most imperative and challenging of water-related issues. Incautious practices of engineering and misuses of certain technologies have certainly contributed to creating many water issues, but engineering and technology at the same time hold the answers to resolving those issues.”
Water technologies have had a lot of obstacles to overcome, despite the fact that 70 percent of the planet is water. The big problem is that humans can use less than one percent of it – the rest is salt water or permanently frozen – and of that one percent, only 10 percent is available to drink. As a result, one billion people today lack clean drinking water. To make matters worse, the world’s population will grow by two billion in the next 20 years, intensifying competition that has always been fierce. Sometimes deadly.
In 2004, the same year that Galerias Filtrantes came to the Tehuacán Valley, two cousins in the farming region of Jalisco, Mexico, stood back-to-back, pistols in their hands. Cursing each other one last time, they took four paces, turned, fired and shot each other dead just a few yards from the small spring that lay on the border between their properties – the ongoing argument about who owned the source of their drinking water was over. Five years later, half a world away in Madhya Pradesh, India, a mob beat a family of 12 to death for illegally drawing a bucket of water from a city pipe.
Alamar Hipolito has seen similar tensions firsthand in Mexico City, where he worked in a car wash that had become unpopular because it used freshwater. During a long stretch of intense hot weather, a gang rushed the car wash, wrecked the machinery and chased away the employees, including Alamar. He never went back.
He was, in fact, one of the men in Paredones who came and went as jobs appeared and vanished. When he told the car-wash story to his townspeople, most of them were startled that fresh water could be such a problem in a place as large as Mexico City.
They weren’t aware that similar problems plagued the world’s richest country. Every day in the U.S., leaking pipes released an estimated seven billion gallons of freshwater. Water shortages shut down power plants in the Southeastern U.S. Companies pulled the plug on machinery that relies on water, and layoffs followed. Sewage and ground water threatened to seep into freshwater lines. And repairing the system, more than 100 years old in places, was going to be monumentally expensive – estimates reached $300 billion.
To address these problems, engineers are moving away from traditional, costly methods that eventually create the same problems. Instead they’re developing new solutions that make systems more durable and are less labor-intensive than Band-Aid fixes. With methods such as “pipe bursting,” engineers repair damaged or inadequate lines without digging construction trenches and then laying new pipe. The process involves inserting a pneumatic or hydraulic “expander head” into old pipeline, forcing it forward, smashing the pipe from the inside and pushing the pieces into the surrounding soil. New pipe, attached to the expander head, replaces the old pipe immediately. The pipe-bursting method not only repairs the system but also protects property by eliminating the need for extensive destruction and reconstruction.
The Wastewater Challenge
Engineers are also finding new ways to handle wastewater, a soup of human waste, food scraps and oils; soaps and chemicals from sinks, showers, bathtubs, toilets, washing machines and dishwashers; runoff from roads, parking lots and rooftops – nature can clean the water that’s tainted in its journey through the natural water cycle, but it takes complex technology to treat wastewater.
The primary treatment removes about 60 percent of suspended solids and aerates the water to replenish oxygen that was eliminated by the decay of solid material. Secondary treatment extracts more than 90 percent of the suspended solids. The overall treatment process leaves behind vast quantities of inorganic and organic solids that head in different directions – some to landfills, some to digesters that recover methane gas for energy production, yet other quantities into fertilizer and deep wells. A good portion ends up in incinerators.
From beginning to end, wastewater treatment is a model of what high tech can accomplish, but the facilities cost billions of dollars. And as the need for more of them grows, engineers are responding with technologies that remove waste efficiently, and are small enough to use on-site. The membrane bioreactor fits this profile. But, although it removes waste efficiently, it doesn’t produce drinking water. Its purpose is to treat water to the point at which it’s clean enough to flush toilets, irrigate landscaping and supply air-conditioning systems. An apartment building in New York City invested in the system and, today, the building draws 75 percent less freshwater from the city.
A number of communities are experimenting with small decentralized distillation units, each about the size of a dishwasher – one unit can deliver clean water for 100 people a day. They’re trying closed-loop systems with carbon-nanotube filters that capture impurities and eliminate the need for chemical treatments, high pressure and heavy water tanks, all of which makes the system especially appealing for small, lightweight purification devices. Working with NASA, Seldon Laboratories of Windsor, Vermont, created several such devices that operate as simply as a drinking straw and are almost as small, ideal for astronauts to use in space. A commercial version, the WaterStick, cleans about five gallons of water per minute simply using water pressure and gravity. No electricity or heat. No chemical additives. And no environmental impact. Seldon engineers are building a similar but larger unit that fits under a sink for residential use. Yet larger units might eventually find their way into industrial purification, decontamination and desalination.
The Issue of Water Wasted
Mason Inman is a science journalist who’s written about water issues for publications such as National Geographic and Climate Blue, a blog devoted to energy- and climate-related problems. “Wastewater treatment gets a lot of discussion,” he said. “But water wasted – on farms, where seventy percent of the world’s water goes, and water wasted in cities – that needs some management. We’ve developed a system that consumes the very thing it needs to produce.”
He had an urgent tone as he explained his point. “The current infrastructure collects water from a variety of sources, purifies it for drinking, then pumps it to homes where it’s used not just for drinking but to dilute and flush wastes. Manufacturing consumes billions of gallons. Farms use it for irrigation. Pumps use scads of energy as they push that new wastewater through miles of piping to yet other treatment plants that consume even more energy to remove the wastes from the water again – and that energy-water connection is extremely important because the generation of the former requires a staggering volume of the latter.”
He wasn’t exaggerating. In 2000, thermoelectric power generation in the United States used 195,000 million gallons of fresh- water per day – that’s enough to supply Ann Arbor, Michigan, with drinking water for more than 30 years.
Peter Adriaens, a professor in the Department of Civil and Environmental Engineering and the Zell-Lurie Institute for Entrepreneurial Studies, belongs to a University of Michigan team that he says is “looking at a scenario in which we’ll need innovative water technologies, new environmental restrictions, new public policy and legal approaches, and an energy model that provides incentives for the power industry to continue evolving, improving its output and efficiency.”
One of the team’s primary tasks will be to investigate opportunities to conserve fresh water in current energy operations, and to find uses for saltwater and wastewater. “We’ll study the costs and benefits of using treatment technologies for impaired water,” Adriaens said. “We’ll weigh options for water recovery, conservation potential and environmental impact.”
By program’s end, the team expects to identify technologies and plant designs that will make it possible to reduce the use of freshwater up to 10 percent in the generation of thermoelectric power.
Inman was enthusiastic about the program. “It’s absolutely crazy to purify all this water, then use most of it for things that don’t need water of that quality,” he said. He’s hoping a similar program develops to address the threat that agriculture poses for the world’s aquifers — the system of groundwater that lies beneath vast tracts of land.
The Ogallala Aquifer, for one, is an underground lake that stretches from southern South Dakota through northern Texas. And it furnishes drinking water to 82 percent of those who live in the area and about 30 percent of the groundwater that farmers there use to irrigate what has come to be known as America’s Bread Basket. Studies estimate that withdrawals from the Ogallala Aquifer will deplete its supply in 25 years. No one has offered a long-term solution.
Technology is taking bites out of this problem – Alamar Hippolito saw this firsthand while working on a farm in Santa Ana Teloxtoc, Mexico, where engineers installed a drip irrigation system on a small parcel of land to demonstrate the process to owners. The system channeled water to the roots of plants, drop by drop. Over a one-month period, farmers tested corn, beans, peas, cantaloupe, wheat and squash. The consensus was that drip irrigation would produce abundant crops while limiting the use of groundwater.
Drip irrigation caught on in Mexico and other areas of the world where water is scarce. Farmers in sub-Saharan Africa are using the technology with great success – in some areas it doubled crop yields and saved 40 to 80 percent of the water that normally would’ve been used. This, in turn, meant more water was available for drinking and cooking. That technology has evolved into photovoltaic drip irrigation, which couples the efficiency of drip irrigation with the economy of a solar-powered water pump.
Dowsing, Desalination and Other Water Technologies
People have devised all manner of devices and methods to find drinking water. The oldest might be dowsing or “water witching.” The two common methods are pendulum dowsing, which simply requires someone to dangle a rock from a thin rope, and “Y dowsing,” in which the dowser uses a y-shaped stick. Dowsing doesn’t get more than a snicker from the scientific community, but a 1995 study in the Journal of Scientific Exploration, a peer-reviewed journal with editorial offices at Stanford University, carried the results of a program to test and apply dowsing methods to locate water sources in arid regions. This 10-year project involved more than 2,000 drillings in Sri Lanka, Zaire, Kenya, Namibia, Yemen and other countries and is the most ambitious experiment with water dowsing that scientists ever conducted. The outcome turned heads. Dowsers achieved a success rate of 96 percent in 691 drillings in Sri Lanka. Conventional techniques used in that area had a success rate of 30-50 percent.
That peer-reviewed article notwithstanding, it’s hard to find an engineer who will walk across hard-baked earth looking for drinking water with a rock on a rope. A more acceptable method is desalination, which has had two major drawbacks: Large-scale desalination typically consumes extremely large amounts of energy – which, in turn, devours freshwater – and it requires an expensive infrastructure. Nevertheless, more than 13,000 desalination plants are in operation worldwide, producing more than 12 billion gallons of water a day – a large number but not as much as engineers hope get out of the technology. However, they’re making progress. Nano-osmosis, one particularly hopeful approach, uses carbon nanotubes to filter salt from water – it’s effective, uses less energy than typical desalination to produce equal amounts of potable water, and it costs much less.
Engineers are also having success in the development of biomimetic membranes for water purification and desalination. Researchers took a close look at how kidneys transport water so efficiently through a membrane with aquaporins (proteins that are embedded in the membrane cells and are critical in regulating the flow of water). Investigators found a way to duplicate that structure in a synthetic system. The advantages were clear. Unlike most biological membranes, polymer membranes are stable and can withstand considerable pressure – essential characteristics for water-purification and desalination processes. The ability to embed aquaporins in materials that can be used outside the body is a breakthrough that promises to open doors to water purification and desalination in industrial and municipal applications.
Applications of nanotechnology to membrane development have affected the way that engineers extract freshwater from snow and ice, which hold about three-quarters of the Earth’s freshwater. Water from the Gand Springs, near the Findel Glacier in Switzerland, is a good example. Perfectly hygienic. Abundant. Accessible. However, it contains sulphate at levels that give it an unpleasant taste, and enough calcium to clog boilers and appliances. But nanotechnology turned Gand Springs around in 2006 when the Wichje filtration plant was able to provide clean drinking water simply by directing water through a membrane with pores less than one nanometer in diameter — small enough to filter out calcium and sulphate ions, as well as all chemical compounds, viruses and bacteria.
While the extraction and refinement of freshwater from Gand Springs required the smallest of technologies, technology on a grand scale played a key role in a 2008 venture in Sitka, Alaska. City officials put together a plan to distribute water from nearby Blue Lake, which is fed by snowpack and glaciers, and holds trillions of gallons of water so pure that it needs no treatment to be potable. The city joined forces with two companies, True Alaska Bottling and S2C Global, in what was the world’s first large-volume export of water by tanker – each year, they plan to transfer 2.9 billion gallons of drinking water to a bulk bottling facility near Mumbai for distribution among several drought-plagued cities in the Middle East. The agreement called for engineers to build a berth for a Suezmax vessel (the largest ship that can pass through the Suez Canal) that can hold up to 40 million gallons, an offloading system connected to a storage tank farm, and a distribution complex for the packaged water.
Finding water fit to drink isn’t just a pursuit, it’s a necessity – humans can live a month without food, but just a week without water. And shortages aren’t local – they plague people in the driest parts of the world like the Middle East, in seaside towns where undrinkable saltwater stretches to the horizon, and in cities with aging infrastructures that can’t get the water where it’s supposed to go. But technology as old as galerias filtrantes and as new as closed-loop nanofiltration is putting water where the mouths are. Technology is the solution.