Water gets local
Plumbing and sewage treatment aren’t the sexiest of pursuits, but innovative approaches are changing cities from their innards out. Just as some people now generate their own electricity, others are starting to clean and reuse their own water on site rather than piping it all back to a central treatment plant. Read More
Plumbing and sewage treatment aren’t the sexiest of pursuits, but innovative approaches are changing cities from their innards out. Just as some people now generate their own electricity, others are starting to clean and reuse their own water on site rather than piping it all back to a central treatment plant.
It’s called distributed water, a term that stems from distributed generation: the practice of generating energy on site. Reusing water on site saves energy and money -- because you don’t have to move the water back and forth from centralized treatment. In fact, we use vast quantities of energy to move water and treat it to drinking water standards – about 13 percent of total energy consumption in the United States.
Consider cooling towers, found in many skyscrapers and industrial systems. To cool the building they use drinking water, and 80 percent of it evaporates. Plus, the process uses toxic chemicals, so the remaining 20 percent is then sent back to a centralized wastewater treatment facility, where much money and energy in invested to clean it prior to discharge into a river.
“It makes absolutely no sense,” said David Henderson, co-founder of XPV Capital Corporation, a Toronto-based firm that has invested exclusively in water companies. “We could be recycling all the water in the basement and putting recycled water back up to the tower,” he said.
Drinking level quality is simply not necessary for many uses, such as watering gardens, washing cars, flushing toilets, and industrial activities. By keeping water from various waste streams segregated and using just the amount of treatment needed for the next use, we can maximize efficiency in water treatment.
“Some day in the not too distant future, our practice of flushing toilets with drinking water will be viewed as being as archaic as using pigeons to carry text messages, as wasteful as sending every bottle and can to the landfill, and as disgusting as dumping raw sewage into rivers and lakes,” wrote Don Elder, former president of River Network.(1)
Low-impact development means reintroducing permeable surfaces in cities, including porous pavement, green roofs, rain gardens on sidewalks, vegetated swales, dry wells, urban agriculture, parks along rivers, and wetlands and stream restoration. The goal is to absorb rain into the ground right where it falls, allowing the earth to filter the water naturally.
Severe droughts and population growth have been straining water supplies around the world in recent years, from Texas to California to Australia. But reused water is often the cheapest source of “new” water. That’s because using water more than once postpones the need to develop new water sources, such as expensive, energy-intensive pipelines transporting water from afar or a desalination plant.
Reuse can also supply water to another important customer: the local ecosystem. In many places in the world, including the western United States, most surface water is used for human consumption. To replace that deficit, treated water can be released into an aquifer to recharge overdrafted groundwater resources, and it can be discharged into a river to help maintain aquatic ecosystems. Constructed wetlands can accept and clean partially treated water, while serving important ecological functions as well.
Even the U.S. Environmental Protection Agency is on board with distributed water systems, recognizing them as a fundamental part of future water infrastructure. It provided funding for new projects under the 2009 American Recovery and Reinvestment Act (ARRA).
Distributed water encompasses a range of approaches, from low tech, harnessing nature’s processes, to the technologically advanced. But even as homes and businesses become more water independent, most will likely remain networked with their cities’ centralized water systems, just as someone with solar panels on their roof is still likely connected to the city’s electricity grid.
One of the lowest tech ways to treat water in a distributed fashion is through low-impact development, or LID. Many cities have centralized stormwater management systems. When it rains, water is funneled into gutters and dumped into a giant centralized treatment facility, where it is cleaned and released.
In the Great Lakes region and in Northeastern United States, stormwater runoff was combined with sewers in many cities. The idea was to clean petroleum residues, pesticides, and nutrients from stormwater runoff before releasing it into rivers and estuaries. But storms swamp these systems, forcing the immediate release of untreated sewage into lakes and rivers -- up to 75,000 times a year, according to the U.S. EPA.
Greener infrastructure also increases a city’s quality of life, giving residents a chance to reconnect with nature and increasing property values. It reduces the heat island effect, cooling buildings and neighborhoods, and creates habitat for wildlife.
In the United States, Philadelphia, Chicago, San Francisco, Portland, and Seattle are leading the way with LID strategies.
LID also reduces floods by reduces the amount of water headed for the storm system. In Houston, prairie pothole wetlands used to absorb rainfall. But as the city has grown, paving over 600 square miles, floods have become a regular occurrence. The engineered storm water systems built to contain these floods are not as effective as the wetlands, said John Jacob, director of the Texas Coastal Watershed Program at Texas A&M.
“These stormwater detention ponds are just big holes in the ground. They don’t have the water quality function that our local wetlands do,” said Jacob. “Certainly we can engineer the stormwater function. We can engineer the water quality thing, but to think we can engineer everything and don’t need these natural functions belies a lack of understanding. These wetlands are extremely complex.”
The Army Corps of Engineers spends more than $1 billion each year on levees and other infrastructure designed to control floods and repair flood destruction. Yet many of these projects actually increase repeated flooding, causing significant property damage.
Some cities are using disaster money from floods to buy out homeowners and businesses from floodplains, replacing them with parks that can easily weather the expected floods.
Tulsa, Okla., on the Arkansas River, saw nine federally declared flood disasters during the 1970s and 1980s. Two of these floods killed 17 people and caused $214 million in property damage. Tulsa used local and federal funds, including flood insurance checks, to buy and remove approximately 500 flood-damaged homes and 375 vulnerable buildings. The reclaimed floodplain is now used for recreation, open space, and nature preserves.(2) Tulsa’s flood insurance rates dropped 25 percent and are now among the lowest in the United States.
Also on the low-tech side are graywater systems, in which water from laundry, showers, and bathroom sinks is routed out into the garden to water plants. Not using fresh water to water the yard can save a lot. In the United States, outdoor water use accounts for 30 percent of residential demand nationwide, and 80 percent in the arid West, according to Mary Ann Dickinson, president of the Alliance for Water Efficiency.
Graywater can contain bacteria, and due to health concerns, projects were illegal in much of the United States for many years. More recently, some states have recognized that graywater can be managed safely and have been relaxing the rules. For example, California updated its graywater regulations in 2009, allowing for basic graywater systems to be installed legally. Pipes deliver water to the garden underground, allowing the graywater to percolate through the topsoil.
San Francisco has embraced the change, offering a rebate to cover most of the cost for homeowners to install a “laundry-to-landscape graywater kit.”
Water can even be reused inside the house. The source can be graywater, rainwater, or utility-delivered treated wastewater. To use this water safely, homes need a dual plumbing system. The pipes that deliver reused water to, say, toilets are colored purple so no one will mistake them for containing potable water.
Dual plumbing systems could be phased in over time. Utilities could greatly speed installation of such infrastructure and reuse programs by redirecting some of the money they spend securing new supplies. San Francisco; Irvine, Calif.; and other cities are beginning to require purple pipes in new construction.
A lot of reuse happens on the municipal level. Cities in Arizona and California, Florida, Nevada, and Texas have been reusing water safely for years by discharging treated wastewater into an aquifer, rather than into a river or ocean.
To meet increased demand from rapid population growth, water managers in Gilbert, Ariz., designed a system to discharge wastewater into recharge ponds, where it percolates down into the aquifer for future use. Pond water is also used directly for irrigation and other nonpotable uses, reducing demand on groundwater. Residents enjoy recreation around the ponds, which also provide critical riparian-style habitat for wildlife.(3) During summer’s peak demand, Gilbert saves more than 131 million gallons of drinking water a day.
In many cities, including Irvine, Calif., and Singapore, water processed in this way is then used for drinking. But sometimes it simply receives “advanced treatment” and is returned directly to the water supply.
Sewage, or black water, is the ultimate wastewater challenge. But some communities are taking it on in both low-tech and high-tech fashions. In the 1970s, Arcata, a small town in Northern California, was required to upgrade its sewer treatment to meet new water quality standards. The community could have bought in to a proposed $25 million regional sewage plant. But residents believed this investment would lead to sprawl and change the tenor of the community.
Instead, Arcata built a marsh on an old brownfield to treat its municipal sewage. Wastewater piped from homes and buildings moves through the 154 acres of fresh and saltwater marshes, tidal mudflats, and grasslands, as natural processes purify the water. Chlorination brings it up to state standards before its release into Humboldt Bay. It opened in 1986, and today people in the town use the Arcata Marsh and Wildlife Sanctuary for recreation and consider it a point of community pride.
Going a bit higher tech is a mixed-use development in my new hometown of Victoria, British Columbia, Canada, called Dockside Green. Built on a former brownfield site, it treats wastewater onsite, then reuses it for toilet flushing, irrigation for landscaping and a green roof, and to supply a restored stream. The stream has become a focal point of the development, and housing along it goes for premium prices.
Projects like Dockside Green are now possible because innovation has made water technology smaller and more portable. It’s a similar phenomenon as the technical integration that shrunk cell phones and made telecom an integral part of our daily lives, said David Henderson of Toronto’s XPV Capital. “Ultimately, the technology becomes mobile. Now we can manufacture wastewater plants in a factory and ship them,” he said.
That’s precisely what a company in which XPV invested is doing. Newterra, based in Brockville, Ontario, builds modular wastewater systems that can be used where infrastructure is nonexistent, such as mining operations in remote locales and new, off-the-grid housing developments.
It can also come in handy where water infrastructure is aging and springing leaks, a growing problem. U.S. cities lose about one-fifth of their water to leaks, according to the U.S. General Accounting Office. Newterra can serve towns that are failing discharge requirements.
“We can add systems to act as a kidney to take a load off,” said Bob Kennedy, the company’s president. “Nobody wants to put pipes in the ground. It’s just too expensive.”
Distributed generation “is going to change the way we build infrastructure in the 21st century,” said Henderson.
1 Don Elder, Water Reuse, River Network web site, www.rivernetwork.org/water-reuse, viewed 2/24/10.
2 City of Tulsa, Oklahoma, From Harm’s Way: Flood-Hazard Mitigation in Tulsa, Oklahoma, 1993, www.smartcommunities.ncat. org/pubs/harmsway/index.shtml.
3 U.S. EPA, “Cases in Water Conservation: How Efficiency Programs Help Water Utilities Save Water and AvoidCosts,” EPA832-B-02-003, July 2002, p. 17-18.