May 24, 2006 | General

The Future Of Water Reuse

BioCycle May 2006, Vol. 47, No. 5, p. 25
Stakeholders will need to improve monitoring systems, as well as public education, to ensure greater acceptance of indirect potable reuse practices.
Robert Bastian

THE CONTINUED GROWTH in demands being placed on limited available fresh water supplies in many areas of the country, along with ever tightening discharge standards will likely lead to an increased dependency upon water reuse, at least where concerns are appropriately addressed to gain strong public acceptance. Areas with limited water resources, such as the arid U.S. Southwest, already have well-established water reclamation and reuse programs.
For example, over 525,000 ac. ft./yr. (nearly 470 mgd) of water were recycled in California in 2003, with nearly 46 percent of that used for agricultural irrigation (see Figure 1) and the current goal set by State legislation is for this to be increased to1 million ac.ft. (nearly 893 mgd) by the year 2010. The popularity of reuse has also grown in other areas such as Florida, which now has over1.2 bgd of total reuse capacity and over 630 mgd of reclaimed water actually being reused, with 50 percent of that used for landscape irrigation in public access areas such as residences, golf courses, parks, and school grounds (see Figure 2).
The WateReuse Association has estimated the amount of water reused in the U.S. in 2004 to be ~2.6 bgd and projected this amount would increase to about 12 bgd by 2015 (see Figure 3). In the Middle East, North and South Africa, Central and South America, Asia, Australia, and even in parts of Europe a great deal of water is currently reused to irrigate agricultural crops or for other purposes.
As demands on existing water supplies increase and discharge standards become stricter, more people probably will become interested in reusing reclaimed water. In the United States, for example, total maximum daily load (TMDL) negotiations associated with protecting high-quality receiving waters or effluent-dominated reaches probably will lead to more restrictive discharge standards. Once nutrient or metal limits for discharged effluent become more restrictive than those for drinking water, reuse options will be considered more seriously. More people will begin asking: “Why discharge reusable-quality effluent when it is a cost-effective alternative water supply?”
Currently, public, political, and scientific acceptance of water reuse practices varies considerably and probably will continue to do so into the foreseeable future. Most people accept the use of reclaimed water to irrigate forage crops, create wildlife habitat, and in industrial processing or cooling systems, but reuse options involving more intimate human contact, such as irrigating golf courses and playgrounds, producing food crops, and augmenting potable water supplies, face more restrictions and public acceptance resistance.
Some people (even including some water-reuse advocates) take the moral high ground, arguing that planned, indirect potable reuse is unnecessary or involves unknown safety risks. Others simply prefer to avoid exposure to what they consider to be former human wastewater. Meanwhile, “unplanned potable reuse” occurs in many areas because of effluents discharged to waterbodies that also serve as downstream potable water supplies. Given the strong, often organized opposition that has been focused on some indirect potable reuse projects (e.g., Tampa, Florida; San Diego, San Gabriel, and Los Angeles, California), perhaps it is time to seriously consider encouraging an independent study that addresses the available information on the risks associated with unplanned potable reuse vs planned indirect potable reuse.
Scientists have conducted extensive studies to address many of the technical concerns that have been raised about using reclaimed water to produce food crops and augment public water supplies. For example, they have comprehensively evaluated crops grown with reclaimed water, made chemical and microbial comparisons of reclaimed water and existing local raw water supplies, undertaken epidemiological studies of populations consuming reclaimed water, and performed multiyear testing of animals fed or raised in reclaimed water for potential carcinogenic, terratogenic, and mutagenic effects.
Such studies generally have shown that irrigation with reclaimed water can produce high quality food crops and the quality of reclaimed water used to augment potable supplies is generally as good as that of existing local raw water supplies. Nevertheless, concerns about indirect potable reuse continue, and more issues have been raised as relevant monitoring and analysis methods have improved. Such concerns include the makeup of the residual total organic carbon (TOC) in reclaimed water, the implications of results from Polymerace Chain Reaction (PCR)-based microbial monitoring techniques, the possible effect of emerging pathogens, the need for a continuous bioassay protocol or other procedures to detect performance problems in water reclamation processes, and the implications of various chlorination by-products and trace amounts of hormone-mimicking compounds, pharmaceuticals, and Nitrosodimethylamines (NDMAs) that have been detected recently in many reclaimed effluents. Clearly, considerable effort will be required to address such concerns comprehensively.
The water reuse field has changed considerably since the U.S. Environmental Protection Agency (EPA) issued its Guidelines for Water Reuse (EPA625/R-92/004) in September 1992. Many new projects have been established, revisions issued to state requirements, improvements made to available treatment systems, and numerous technology evaluations completed. Several organizations have evaluated the viability of indirect potable reuse; their findings were published in such documents as the 1998 National Research Council/National Academy of Sciences (NRC-NAS) study, Issues in Potable Reuse: Augmenting Drinking Water Supplies with Reclaimed Water, conducted by the Water Science & Technology Board, and the 1998 special joint publication, Using Reclaimed Water to Augment Potable Water Resources, by the Water Environment Federation and the American Water Works Association.
Research and demonstration efforts have led to more acceptance and use of ultraviolet (UV), ultrafiltration, and membrane treatment systems, as well as a far better understanding of soil aquifer treatment, wetlands treatment and reuse systems. Reclaimed water now is used more often as an alternative water supply for nonpotable uses, such as creating and maintaining wildlife habitat, irrigating urban landscapes, and helping prevent saltwater intrusion into shallow aquifers. Such developments lead EPA to update and supplement the EPA Guidelines for Water Reuse document in a revised version (EPA625/R-04/108) issued in August 2004.
Meanwhile, continued population increases in many parts of the country (and for that matter around the world) will force the choice between increasing central treatment capacity (and associated trunk sewers) and using more localized small systems. In parts of Japan, new developments over a certain size are required to provide on-site wastewater treatment with reuse for toilet flushing, landscape irrigation, and other uses. Therefore, improved technologies for small-scale on-site water reclamation and reuse, ranging from gray water recycling systems to membrane reactors, probably will become important.
However, treatment technology improvements alone will not be enough to guarantee the success of future reuse efforts. Stakeholders will also need to improve information and monitoring systems, as well as public education, to ensure more acceptance of indirect potable reuse practices. They also will need to address water rights issues and the potential ecological effects of disinfection by-products, estrogen-disrupting and biodegradation-resistant compounds.
To learn more about today’s reuse-related challenges, see the WERF’s 2001 Management Practices for Nonpotable Water Reuse report, the December 2002 update of their review of planned reuse in their 1994 report Assessment Report on Water Reuse, and their 2003 Water Reuse: Understanding Public Perception and Participation report; the NRC/NAS’s 1998 Issues in Potable Reuse: Augmenting Drinking Water Supplies with Reclaimed Water; the National Water Research Institute’s 1999 Non-Potable Water Recycling report; and of course EPA’s updated 2004 Guidelines for Water Reuse.
Robert K. Bastian is a Senior Environmental Scientist in the U.S. Environmental Protection Agency’s Office of Water based in Washington, D.C.
THE EARLIEST land application systems go back to 1531 in Bunzlau, Germany, where a sewerage irrigation project was in operation for over 300 years. Since those early projects, a wide variety of land treatment systems for municipal and industrial wastewater have been utilized. Land treatment systems can have multiple functions, such as pollution control and prevention, water supply augmentation, crop production and groundwater discharge.
In the early 1970s, the Muskegon County, Michigan slow rate system became the symbol of modern land treatment technology. In the 1980s, an even larger slow rate system, the forested sprinkler irrigation system in Dalton, Georgia, became symbolic of this technology. The total site is 9,000 acres with about 4,605 acres of forest being irrigated. As of 2002, the site will be managed to maximize protection of the soil, and all effluent applied infiltrates into the soil and no overland flow occurs.
Recently there has been renewed interest in land application of food processing wastewater because of its cost-effectiveness and its ability to treat wastewater constituents effectively. In California’s Central Valley, land application is practiced by over 70 percent of the food processing industries.
The practice of land treatment continues to evolve and expand. For municipal wastewaters, groundwater recharge, water reuse, and forest irrigation systems have increased in size and numbers. For industrial wastewaters, the land application of food process/rinse water has been shown to represent best practicable treatment and control.
This piece was excerpted from an April 2001 BioCycle article, “Applying Treated Wastewater To Land,” written by Ron Crites with Brown & Caldwell; Sherwood Reed of Environmental Engineering Consultants and Robert Bastian with EPA.
REUSE has become an integral part of wastewater management, water resource management and ecosystem management in Florida. During the past 19 years, Florida has risen to be recognized as a national leader (along with California) in water reuse. Approximately 637 million gallons per day (mgd) of reclaimed water were xreused for beneficial purposes in 2004. The total reuse capacity of Florida’s domestic wastewater treatment facilities has gone from 362 mgd in 1986 to 1,273 mgd in 2004 which amounts to an increase of 252 percent. The current reuse capacity represents about 56 percent of the total permitted domestic wastewater treatment in Florida.
Reclaimed water from these systems was used to irrigate 175,262 residences, 443 golf courses, 508 parks, and 225 schools. Irrigation of these areas accessible to the public represented about 50 percent of the 637 mgd of reclaimed water reused.
AS REPORTED by Clifford Fedler of Texas Tech University in the February 2005 issue of BioCycle, fresh water that is consumed is almost universally used once and then discharged into a receiving stream. Once in that stream, water is essentially sent to our coastal waters. “With our population continuously growing, causing ever-increasing demands upon our natural resources, the future of our water resources will be reduced even further. It is time for a shift in our thinking,” Fedler observes. “All water should be reused to produce a multitude of valuable products while reducing the demands of our fresh-water resources.” He continues in his 2005 analysis:
If only half of the water from our municipal wastewater treatment systems in the U.S. were utilized to irrigate crops, over 4 million acres of crops could be produced. In addition, sufficient freshwater would be saved to permit our population to grow by 40 percent without adding any strain on our currently available resources. Similarly, on a global perspective, if only half of the municipal wastewater was treated and used to produce a crop, over 180 million acres of land could be irrigated. This is equivalent to supplying over two billion people with the levels of water currently used per person in the U.S.
The outlook for the future of our available natural resources, especially water, does not have to be bleak. In parts of the world, water is limited and in many cases the quality of that water is compromised, which leads to major health issues. Much of that compromised water is the result of a lack of adequate sanitation, yet adequate technology is available to solve the problem in even the most underdeveloped regions of the world. Sufficient low-technology waste treatment systems exist that can be used to significantly reduce the environmental impact caused by not treating wastewater before discharge into our natural streams. If recycling of the waste is considered, the cost of providing treatment is significantly reduced and can provide tremendous economic benefit to the community.
LAST OCTOBER, water managers in South Florida agreed to develop other water sources for the region – largely by recycling treated sewage and underutilized brackish groundwater. The bulk of the $43.1 million comes from the state legislature and will be used for 80 projects from Orlando to the Florida Keys. The metro area from Palm Beach through Monroe County recycles 11 percent of its treated wastewater, with Beach County the most aggressive with a 29 percent rate. Broward County received $2.5 million for four projects, with almost 60 percent going to Fort Lauderdale to help pay for Florida Aquifer withdrawals for the city. Pompano Beach received $148,000 to expand reclaimed water lines to homes.

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