Water Scarcity: Engineering a Global Challenge

To download the report, visit WorldBank.org.

At last, a drop of water upon the desert…

Water scarcity — the so-called “forgotten child” of climate change — grabbed the spotlight among global media in May with the release of a highly anticipated new report from the World Bank Group, High and Dry: Climate Change, Water and the Economy.

“The combined effects of growing populations, rising incomes and expanding cities will see demand for water rising exponentially, while supply becomes more erratic and uncertain,” the report predicts. It further warns that reduced freshwater availability and competition from other uses — i.e. energy, agriculture, manufacturing, etc. — could reduce water availability in cities by as much as two-thirds by 2050, compared to 2015 levels.

Of course, some Third World regions are more vulnerable than others, especially Central Africa, East Asia, and the Middle East. In those regions and elsewhere, water scarcity could easily spike food prices, spawn refugee crises, and spur violent conflict. Meantime, expect GDPs to drop, in some cases significantly so, warns the report.

All alarming, made even more so because water appears so plentiful, particularly among vast expanses of the U.S. Yet, like politics, all shortages are local. According to The Water Project, a Concord NH-based nonprofit, the Colorado River today is drying up in some areas, and Arizona’s Lake Meade, currently supplying water to 22 million people, could itself run dry in just a matter of years. Meanwhile, drought and related water rationing woes continue to keep California in perpetual disaster mode.

Scarcity in abundance

Worldwide, the Paris Climate Agreement, signed by 170 nations in April, pledged to limit global warming to no more than 3.6 degrees above pre-industrial levels. Here, the charge is clear: lower CO2 emissions with cleaner sources of power. By and large, industry, academia and government have the technologies at their disposal to do so, or are in the process of developing them.

Water scarcity, however, is unevenly spread. So the strategy is less clear, given that water supplies, topography, climate, economic resources and technological acumen vary greatly from region to region. Solutions, therefore, involve multitudes of strategies and technologies, many involving water recycling.

This week, as the American Water Works Association gathers for its annual spring conference in Chicago, BuiltWorlds offers this coast-to-coast sampling of current U.S. projects, studies, initiatives and facilities intended to generate vaster amounts of potable water in a more cost-efficient manner.

• Calculating runoff. Watch the new EPA video on estimating stormwater totals across the U.S.

From Toilet to Tap

Add Tampa FL to the list of cities, joining Los Angeles and San Diego, among others, now evaluating the feasibility of converting toilet water to tap water. On June 1, the Tampa City Council voted to proceed with a two-year, $3-million study of the concept and what would be required to implement it.

“It’s a game changer that could resolve drinking water supply problems for Tampa and the region for many decades to come,” said Brad Baird, Tampa’s administrator for public works. The drivers behind it are current projections that foresee major economic growth in the area in coming years.

The city already is home to the Tampa Bay Seawater Desalination Plant, which cost $158 million to build and opened in 2007. Baird believes a toilet-to-tap option would be far more economical than building a second such facility, which are also costly to operate.

Taking all this into consideration, the feasibility study will look at several approaches. Rather than dump 60 million gallons of treated wastewater into Tampa Bay, one proposal calls for pumping the reclaimed water north to a county wilderness preserve, from which it would filter through wetlands or rapid-filtration basins to the Tampa Bypass Canal. From there, it could be drawn and further treated to drinking water standards before reaching customers, according to the Tampa Bay Times.

Assuming it is implemented, the technology would accommodate the reuse of at least 20 million gallons per day (mgd). Tampa has pegged total project costs at between $160 million to $250 million, depending on the concept chosen.

Toilet to tap is not yet authorized for use in Florida, though Baird has met with members of the state’s Dept. of Environmental Protection who have expressed interest. In California, although water reuse is common for agricultural and landscape irrigation, as well as industrial use, the state has yet to authorize toilet-to-tap, despite longstanding interest from parched municipalities like Los Angeles and San Diego. Of course, the “ick” factor remains, which poses a high hurdle for public acceptance.

So Baird expects pushback. “Toilet-to-tap is a catchy expression, but it actually means from toilet to water treatment to water treatment, to water treatment, to water treatment, with both natural and engineered systems incorporated into the process,” he explained.

Ozone-Biologically Active Filtration

Some 3,000 miles to the West, crises continue to breed creativity. In drought-stricken California, some now believe that ozone-biologically active filtration (ozone-BAF) could serve as a more cost-effective method for achieving reuse of potable water, according to Kati Bell, water reuse global practice lead with MWH Global, the Broomfield, CO-based engineering giant recently acquired by Stantec. Making a strong pitch for ozone-BAF, Bell recently co-authored a paper with colleague Melanie Holmer, who leads MWH Global’s California regional practice. Since California currently permits indirect potable reuse, the treatment process must include reverse osmosis as part of a multi-barrier sequence that allows injection of finished water into groundwater supplies for drinking water. But potential problems arise in inland communities, says Bell. At issue, reverse osmosis produces a toxic concentrate waste stream that can’t easily be disposed of in current coastal communities.

“ozone-BAF allows not just for the rejection, but the transformation and destruction of trace organic compounds… It could serve as a cost-effective means for inland communities in California to expand and diversify their water supplies”

“Contending with this waste stream can create barriers to implementation of potable reuse, because it adds to project costs,” Bell said. “ California’s regulatory framework requires use of reverse-osmosis for groundwater recharging of drinking supplies through direct injection.”

Assuming California’s reverses its requirement for reverse osmosis, as some believe it will, ozone-BAF could dramatically reduce the costs for potable reuse for inland utilities, since it doesn’t generate concentrate streams, Bell added. In a nutshell, the the ozone component of the process breaks down trace organic compounds and other substances of concern into smaller-weight components with more biodegradable compounds that can be removed in a biologically active filter. As a result, “ozone-BAF allows not just for the rejection, but the transformation and destruction of trace organic compounds,” according to Holmer and Bell. “BAF could serve as a cost-effective means for inland communities in California to expand and diversify their water supplies.”

Energy-Neutral Wastewater?

Power multinational GE, which touts itself as innovation champion and “the world’s premier digital industrial company”, for years has been focusing on water reuse technologies. Its water treatment and reuse equipment division is equipped with 1,000 installations that collectively treat more than one billion gallons of water per day around the world.

According to Jon Freedman, director of GE Global Partnerships, the firm traditionally has focused on three layers of treatment, ranging from chemistry and filter pretreatment to physical separation of materials — dissolved salt included — to ultra filtration membranes, known as Membrane BioReactors, which remove bacteria and other microscopic matter. Freedman says the membrane serves as a building block for most water reuse projects that GE installs.

https://youtu.be/h4DmRben2os

Because municipal wastewater treatment requires large quantities of energy, GE is seeking to economize those operations. A current R&D effort focuses on “Energy Neutral Wastewater Treatment,” a technology that not only eliminates energy use from wastewater treatment but potentially generates new energy sufficient to add to the electric grid.

For a pilot project, wastewater treatment converts organic material in methane to energy after the gas is burned in highly-efficient engines. “We believe there is enough energy in that process to not only run a wastewater plant but send some back to the grid,” Freedman recently told reporters. “This is one of the keys to unlocking the energy-water nexus.”

De-sal Nation? Not yet

Though they currently number 300, desalination plants — which extract salt from seawater — have been slower to catch on in the U.S. This is due to reasons ranging from regulatory restrictions in coastal states, to the prohibitively large amount of water needed to power such plants, to debate over how to dispose of the salty waste at the end of the process. However, declining costs and improved tech has prompted more and more counties and municipalities to consider and even implement the option.

But the results don’t come cheaply.

Desalination plants on average require about 15,000 kwh of power for every million gallons of fresh water they produce, about double that needed for the same amount of water derived from conventional wastewater reuse, according to the Pacific Institute. And despite recent advances, the majority of desalination facilities still employ reverse osmosis that pumps water at high pressure through semi-permeable membranes which remove salt and other minerals.

To reduce costs, researchers are attempting to to improve those fine membranes. Typically consisting of films rolled into hollow tubes through which water wicks, the membranes currently have an average diameter of eight inches. By doubling that size, researchers hope to save energy. “You can produce more water while reducing the footprint for the equipment,” explained Harold Fravel Jr., executive director of the American Membrane Technology Association, recently speaking with reporters.

Other researchers are investigating a process known as “forward osmosis”, in which seawater is drawn into the system by a solution containing salts and gases, resulting in a high-osmotic pressure difference between the solutions that leave salts behind as they together pass through a membrane.

As studies continue, demand for desalination is rising, with 16 projects planned for California, alone.

Case in point: This year, California’s San Diego County will begin receiving water from a new $1-billion desalination plant in Carlsbad CA equipped for a capacity of 50 million gallons per day. It will supplant the desalination plant in Tampa as the largest facility of its kind in the U.S.

As Bob Yamada, water resources manager for San Diego County Water Authority, once put it, “You can’t conserve your way out of a water shortage completely.”

Yes, crises and creativity continue go hand in hand, now and for the foreseeable future.