Wastewater Recycling (English)
All water is recycled water. Chances are, most, if not all of the molecules of water that you drink have passed through the bodies of other humans or animals. In addition, all water on the earth has been recycled countless times through the natural “hydrologic cycle.” Precipitation in the form of snow or rain falls to the ground and then eventually flows to rivers, lakes and the ocean. The water then evaporates, rises into the sky, condenses into clouds, and falls back to the earth as rain or snow, completing the cycle. Some rain percolates into underground aquifers where it remains until feeding a surface water body at a lower elevation or being pumped out for use.
Although our sources of fresh water are finite, they are part of a naturally-replenishing system. The problem – we tend to use up the water faster than it can be replenished. The solution – use water more efficiently. Part of that is using less water through a variety of means, including more efficient irrigation systems, ocean friendly gardens that don’t require much water and water-conserving appliances and shower heads. But an equally important part of the solution is reusing (and reusing, and reusing…) the water we have.
Much of the water (“greywater”) that goes down the drains from showers and sinks in our houses is suitable to be used locally for irrigation purposes. The rest (“black” water) can be used for irrigation after going through a conventional primary/secondary sewage treatment process, typically followed by filtration and disinfection. This treated wastewater is often referred to as reclaimed water and can be used to irrigate parks, golf courses, cemeteries and other landscaping. And 100% recycling is possible. Cape Coral, Florida recycles all of its wastewater during some years. A few years ago the city launched a half-billion dollars worth of water and sewer treatment plant expansions to treat wastewater and pump it back through the city’s irrigation system. This protects their waterways and assures the city has a reliable water source all year. More details.
Understanding and implementing water recycling requires a paradigm shift from thinking of “used” water as wastewater (something to get rid of as cheaply as possible) to thinking of it as a valuable resource. Existing, proven technology can be used to convert water that has previously been flushed down your toilet into drinking water that meets all applicable water quality standards and is probably purer than most expensive bottled water.
An example of just such a facility is the Groundwater Replenishment System in Orange County, California. There, about 100 million gallons per day of wastewater that has gone through primary and secondary treatment at Orange County Sanitation District’s “Plant 1” is piped to a facility next door operated by Orange County Water District. The water is then processed through three additional purifying steps, using microfiltration, reverse osmosis, and advanced oxidation. At that point the water is pumped about 15 miles to spreading basins where the water is allowed to percolate through natural sand into underground aquifers. Wells then draw water out of the aquifer to be used as a fresh water supply. That system can be thought of as a continuous loop or a “man made” water cycle.
Following Orange County’s lead, both Los Angeles and San Diego are in the process of expanding their reclaimed water systems and are evaluating the implementation of further treatment to allow potable use. In San Diego this is being termed “reservoir augmentation” or “indirect potable reuse” and has been branded Pure Water San Diego. And this isn’t just a California thing. Since 1978, the Upper Occoquan Service Authority has been discharging recycled water into a stream above Occoquan Reservoir, a potable water supply source for Fairfax County, Virginia. Many cities pump their water supplies from rivers that receive treated wastewater from upstream cities. Although additional treatment processes such as filtration and chlorination are used to ensure that such water sources are safe, the beauty of the new “advanced” treatment processes such as the ones used by Orange County Water District is that they utilize several technologies to truly “re-purify” the water.
In Florida, the Fiesta Village Wastewater Treatment Plant in Lee County processes wastewater for the South Ft. Myers and Cypress Lakes areas to be either used for reclaimed water or put back into nature to become part of the water cycle. This facility received the Florida Water Environment Association’s 2011 Earle B. Phelps Award in the advanced wastewater treatment plant category. The award honors outstanding wastewater treatment plants in Florida that have maintained the highest levels of pollutants removal. The 5-mgd Fiesta Village AWTP, owned and operated by Lee County Utilities, has won the Phelps Award ten previous times. See the graphic below for a depiction of their treatment processes.
One of the impediments to implementation of wastewater recycling systems, especially those that involve direct or indirect potable reuse of the treated wastewater, has been concern that these projects might represent a risk to public health. In fact, a 1998 National Research Council recommendation was that reclaimed water be used in drinking supplies only as "an option of last resort." Well, times have changed and the scientific understanding of the reliability of treatment processes has advanced. In early 2012 the National Research Council released a new report which says that reclaimed water can contribute a growing portion of the nation's drinking water supplies and be as safe as conventional sources. "We can really say that there is no difference from the risk standpoint," said Jorg Drewes, a water reuse expert who was on the panel. "You can have a supply that is as safe as the current drinking water supplies." As Ben Grumbles says in a NY Times article about the report “In essence, there is no wastewater, just wasted water.” Read more.
Water recycling simultaneously addresses both a water supply problem and a waste disposal/ocean pollution problem. That 100 million gallons per day of wastewater in Orange County that is now being converted into high purity drinking water is 100 million gallons per day of water that doesn’t need to be imported from northern California or the Colorado River. And it’s 100 million gallons of wastewater that no longer flows into the ocean off Huntington Beach.
Water recycling is also feasible at the community or neighborhood level. In fact, small local systems may have advantages over large centralized systems by avoiding the use of long and costly conveyance systems (pipes and pumps). The main concept is that water is a natural resource that is too valuable to use just once and then throw away. Stop the Cycle of Insanity and Know Your H2O. Nature has recycled water since time began. We can too!
Here's a video from WateReuse Association that explains the concepts and advantages of water recycling.