Water reuse can be defined as the use of reclaimed water for a direct beneficial purpose. The use of reclaimed water for irrigation and other purposes has been employed as a water conservation practice in Florida, California, Texas, Arizona, and other states for many years.
Reclaimed water, also known as recycled water, is water recovered from domestic, municipal, and industrial wastewater treatment plants that has been treated to standards that allow safe reuse. Properly reclaimed water is typically safe for most uses except human consumption.
Wastewater is not reclaimed water. Wastewater is untreated liquid industrial waste and/or domestic sewage from residential dwellings, commercial buildings, and industrial facilities. Gray water, or untreated wastewater from bathing or washing, is one form of wastewater. Wastewater may be land applied, but this is considered to be land treatment rather than water reuse.
The demand for fresh water in Virginia is growing as the state’s population increases. This demand can potentially exceed supply during times of even moderate drought. In recent years, the normal seasonal droughts that have occurred in Virginia have caused local and state government to enact water conservation ordinances. These ordinances limit the use of potable water (water suitable for human consumption) for such things as car washing and landscape irrigation. The potential for developing new sources of potable water is limited. Conservation measures, such as irrigating with reclaimed water, are one way to help ensure existing water supplies are utilized as efficiently as possible.
The environmental benefits of using reclaimed water include:
Reclaimed water typically comes from municipal wastewater treatment plants, although some industries (e.g., food processors) also generate water that may be suitable for nonpotable uses. (Figure 1).
During primary treatment at a wastewater treatment plant, inorganic and organic suspended solids are removed from plant influent by screening, and settling. The decanted effluent from the primary treatment process is then subjected to secondary treatment, which involves biological decomposition of organic material and settling to further separate water from solids. If a wastewater treatment plant is not equipped to perform advanced treatment, water is disinfected and discharged to natural water bodies following secondary treatment.
Advanced or tertiary treatment consists of further removal of suspended and dissolved solids, including nutrients, and disinfection. Advanced treatment can include:
Water that has undergone advanced treatment is disinfected prior to being released or reused. Reclaimed water often requires greater treatment than effluent that is discharged to local streams or rivers because users will typically have more direct contact with undiluted reclaimed water than undiluted effluent.
For an interactive diagram of a wastewater treatment system with more information on treatment processes, please see www.wef.org/apps/gowithflow/theflow.htm.
Although the primary focus of this publication is on the use of reclaimed water for agricultural, municipal, and residential irrigation, reclaimed water can be used for many other purposes. Non-irrigation uses for reclaimed water include:
Intentional indirect potable reuse means that reclaimed water is discharged to a water body where it is then purposefully used as a raw water supply for another water treatment plant. This occurs unintentionally in most rivers, since downstream water treatment plants use treated water discharged by upstream wastewater treatment plants.
Direct potable reuse refers to the use of reclaimed water for drinking directly after treatment, and, to date, has only been implemented in Africa (U.S. EPA, 2004).
Examples of non-irrigation permitted water reuse projects in Virginia are:
The turfgrass and ornamental horticulture industries have grown as Virginia becomes more urbanized. The acreage devoted to high-value specialty crops that benefit from irrigation, such as fruits and vegetables, is also increasing. As demand for potable water increases, maintaining turf, landscape plants, and crops will require the utilization of previously underutilized water sources.
The regulation of reclaimed water production and use encourages both the supply of and the demand for reclaimed water. The benefits to suppliers of reclaimed water include greater public awareness and demand for reclaimed water and clear guidelines for reclaimed water production. Benefits to end users include increased public acceptance of the use of reclaimed water and a subsequent decrease in the demand for fresh water.
There are no federal regulations governing reclaimed water use, but the U.S. EPA (2004) has established guidelines to encourage states to develop their own regulations. The primary purpose of federal guidelines and state regulations is to protect human health and water quality. To reduce disease risks to acceptable levels, reclaimed water must meet certain disinfection standards by either reducing the concentrations of constituents that may affect public health and/or limiting human contact with reclaimed water.
The U.S. EPA (2004) recommends that water intended for reuse should:
Biochemical oxygen demand (BOD) is an indicator of the presence of reactive organic matter in water. Total suspended solids (TSS) or turbidity (measured in nephelometric turbidity units, or NTUs) are measures of the amount of organic and inorganic particulate matter in water. Some other parameters often measured as indicators of disinfection efficiency include:
The recommended values for each of these indicators depend on the intended use of the reclaimed water (Table 1).
Table 1. Summary of U.S. EPA guidelines for water reuse for irrigation
(Adapted from U.S. EPA, 2004).
Monitoring for specific pathogens and microconstituents may become a part of the standard testing protocol as the use of reclaimed water for indirect potable reuse applications increases. Pathogens of particular concern include enteric viruses and the protozoan parasites Giardia and Cryptosporidium, whose monitoring is required by the state of Florida for water reuse projects.
Microconstituents include organic chemicals, such as pharmaceutically active substances, personal care products, endocrine disrupting compounds, and previously unregulated inorganic elements whose toxicity may be re-assessed or newly evaluated. Fish, amphibians, and birds have been found to develop reproductive system abnormalities upon direct or indirect exposure to a variety of endocrine disrupting compounds. Such microconstituents may have the potential to cause reproduction system abnormalities and immune system malfunctioning in other wildlife and humans at higher concentrations. The impacts of the extremely low concentrations of these compounds found in wastewater effluent or reclaimed water are unknown. To date, there is no evidence that microconstituents cause human health effects at environmentally relevant concentrations.
Some possible options for the removal of microconstituents from wastewater are treatment with ozone, hydrogen peroxide, and UV light. These methods can destroy some microconstituents via advanced oxidation, but the endocrine disruption activity of the by-products created during oxidation may also be of concern.
No illnesses have been directly associated with the use of properly treated reclaimed water in the U.S. (U.S. EPA, 2004). The U.S. EPA recommends, however, that ongoing research and additional monitoring for Giardia, Cryptosporidium, and microconstituents be conducted to understand changes in reclaimed water quality.
State regulations need not agree with U.S. EPA guidelines and are often more stringent. In Virginia, water reuse means direct beneficial reuse, indirect potable reuse, or a controlled use in accordance with the Water Reclamation and Reuse Regulation (9 VAC 25-740-10 et seq.; available at the Virginia Department of Environmental Quality website www.deq.virginia.gov/programs/homepage.html under Water Reuse and Reclamation.)
The Virginia Water Regulation and Reuse Regulation establishes legal requirements for the reclamation and treatment of water that is to be reused. These require ments are designed to protect both water quality and public health, while encouraging the use of reclaimed water. The Virginia Department of Environmental Quality, Water Quality Division has oversight over the Virginia Water Reclamation and Reuse Regulation.
The primary determinants of how reclaimed water of varying quality can be used are based on treatment processes to which the water has been subjected and on quantitative chemical, physical, and biological standards. Reclaimed water suitable for reuse in Virginia is categorized as either Level 1 or Level 2 (Table 2). The minimum standard requirements for reclaimed water for specific uses are summarized in Table 3.
Table 2. Minimum standards for treatment of Level 1 and Level 2 reclaimed water.
(Summarized from Virginia Water Reclamation and Reuse Regulations: 9 VAC 25-740-10 et seq.)
Table 3. Minimum treatment requirements for irrigation and landscape-related reuse of reclaimed water in Virginia.
(Summarized from Virginia Water Reclamation and Reuse Regulations: 9 VAC 25-740-10 et seq.)
Water quality must be considered when using reclaimed water for irrigation. The following properties are critical to plant and soil health and environmental quality.
Salinity, or salt concentration, is probably the most important consideration in determining whether water is suitable for reuse (U.S. EPA, 2004). Water salinity is the sum of all elemental ions (e.g., sodium, calcium, chloride, boron, sulfate, nitrate) and is usually measured by determining the electrical conductivity (EC, units = dS/m) or total dissolved solids (TDS, units = mg/L) concentration of the water. Water with a TDS concentration of 640 mg/L will typically have an EC of approximately 1 dS/m.
Salts in reclaimed water come from:
Most reclaimed water from urban areas is slightly saline (TDS ≤ 1280 mg/L or EC ≤ 2 dS/m). High salt concentrations reduce water uptake in plants by lowering the osmotic potential of the soil. For instance, residential use of water adds approx 200-400 mg/L dissolved salts (Lazarova et al., 2004a). Plants differ in their sensitivity to salt levels so the salinity of the particular reclaimed water source should be measured so that appropriate crops and/or application rates can be selected. Most turfgrasses can tolerate water with 200-800 mg/L soluble salts, but salt levels above 2,000 mg/L may be toxic (Harivandi, 2004). For further information on managing turfgrasses when irrigating with saline water, see Carrow and Duncan (1998).
Many other crop and landscape plants are more sensitive to high soluble-salt levels than turfgrasses, and should be managed accordingly. See Wu and Dodge (2005) for a list of landscape plants with their relative salt tolerance and Maas (1987) for information on salt-tolerant crops.
Specific dissolved ions may also affect irrigation water quality. For example, irrigation water with a high concentration of sodium (Na) ions may cause dispersion of soil aggregates and sealing of soil pores. This is a particular problem in golf course irrigation (Sheikh, 2004) since soil compaction is already a concern due to persistent foot and vehicular traffic. The Sodium Adsorption Ratio (SAR), which measures the ratio of sodium to other ions, is used to evaluate the potential effect of irrigation water on soil structure. For more information on how to assess and interpret SAR levels, please see Harivandi (1999).
High levels of sodium can also be directly toxic to plants both through root uptake and by accumulation in plant leaves following sprinkler irrigation. The specific concentration of sodium that is considered to be toxic will vary with plant species and the type of irrigation system. Turfgrasses are generally more tolerant to sodium than most ornamental plant species.
Although boron (B) and chlorine (Cl) are necessary at low levels for plant growth, dissolved boron and chloride ions can cause toxicity problems at high concentrations. Specific toxic concentrations will vary depending on plant species and type of irrigation method used. Levels of boron as low as 1 to 2 mg/L in irrigation water can cause leaf burn on ornamental plants, but turfgrasses can often tolerate levels as high as 10 mg/L (Harivandi, 1999). Very salt-sensitive landscape plants such as crape myrtle (Lagerstroemia sp.), azalea (Rhododendron sp.), and Chinese privet (Ligustrum sinense) may be damaged by overhead irrigation with reclaimed water containing chloride levels over 100 mg/L, but most turfgrasses are relatively tolerant to chloride if they are mowed frequently (Harivandi, 1999; Crook, 2005).
Reclaimed water typically contains more nitrogen (N) and phosphorus (P) than drinking water. The amounts of N and P provided by the reclaimed water can be calculated as the product of the estimated irrigation volume and the N and P concentration in the water. To prevent N and P leaching into groundwater, the Virginia Water Reclamation and Reuse Regulation requires that a nutrient management plan be written for bulk use of reclaimed water not treated to achieve biological nutrient removal (BNR), which the regulation defines as treatment that achieves an annual average of 8.0 mg/L total N and 1.0 mg/L total P. Water that has been subjected to BNR treatment processes contains such low concentrations of N and P that the reclaimed water can be applied at rates sufficient to supply a crop’s water needs without risk of surface or ground water contamination.
The Virginia Water Reclamation and Reuse Regulations require that irrigation with reclaimed water shall be limited to supplemental irrigation. Supplemental irrigation is defined as that amount of water which, in combination with rainfall, meets the water demands of the irrigated vegetation to maximize production or optimize growth.
Irrigation rates for reclaimed water are site- and crop-specific, and will depend on the following factors (U.S. EPA, 2004; Lazarova et al., 2004b).
1. First, seasonal irrigation demands must be determined. These can be predicted with:• an evapotranspiration estimate for the particular crop being grown
• determination of the period of plant growth
• average annual precipitation data
• data for soil permeability and water holding capacity
Methods for calculating such irrigation requirements can be found in the U.S. Department of Agriculture’s National Engineering Handbook at www.info.usda.gov/CED/ftp/CED/neh-15.htm (USDA-NRCS, 2003) and in Reed et al. (1995). These calculations are more complicated for landscape plantings than for agricultural crops or turf because landscape plantings consist of many different species with different requirements.
2. The properties of the specific reclaimed water to be used, as detailed in the section above, must be taken into account since these may limit the total amount of water that can be applied per season.
3. The availability of the reclaimed water should also be quantified, including:• the total amount available
• the time of year when available
• availability of water storage facilities for the nongrowing season
• delivery rate and type
Water reuse is actively promoted by the Florida Department of Environmental Protection since Florida law requires that the use of potable water for irrigation be limited. In 2005, 462 Florida golf courses, covering over 56,000 acres of land, were irrigated with reclaimed water. Reclaimed water was also used to irrigate 201,465 residences, 572 parks, and 251 schools. St. Petersburg is home to one of the largest dual distribution systems in the world. (A dual distribution system is one where pipes carrying reclaimed water are separate from those carrying potable water.) In existence since the 1970s, this network provides reclaimed water to residences, golf courses, parks, schools, and commercial areas for landscape irrigation, and to commercial and industrial customers for cooling and other applications.
For more information, see Crook (2005) and Florida Department of Environmental Protection (2006).
The town of Cary is the first city in the state of North Carolina to institute a dual distribution system. The system has been in operation since 2001 and can provide up to 1 million gallons of reclaimed water daily for irrigating and cooling. The reclaimed water has undergone advanced treatment and meets North Carolina water quality rules. To date, there are over 400 residential and industrial users.
For more information, see www.townofcary.org/depts/pwdept/reclaimhome.htm.
The Bayberry Hills Golf Course expansion is one of numerous water reuse projects in Massachusetts. It was initiated in 2001 as an addition to an existing golf course of seven holes irrigated with reclaimed water. These seven holes use approximately 18 million gallons of water per year, and water reuse was necessary since Yarmouth’s water supply was already operating at capacity during summer months. The reused water undergoes secondary treatment followed by ozone treatment, filtration, and UV disinfection. There are provisions for water storage during the nongrowing season. The water reuse project has reduced the nitrogen needed for golf course fertilization.
For more information on this and other reuse projects in the state of Massachusetts, see www.mapc.org/regional_planning/MAPC_Water_Reuse_Report_2005.pdf. For further information on irrigation of golf courses with reclaimed water, see United States Golf Association (1994).
The Southeast Farm in Tallahassee, Florida, has been irrigating with reclaimed water since 1966. The farm is a cooperative between the city of Tallahassee, which supplies water, and farmers who contract acreage. Until 1980, the farm was limited to 20 acres of land for hay production, but has expanded since then to 2,163 acres. The irrigation water receives secondary treatment. The crops grown are corn (Zea mays L. subsp. Mays), soybeans [Glycine max (L.) Merr], bermudagrass [Cynodon dactylon (L.) Pers], and rye (Secale cereale L.).
In recent years, however, elevated nitrate levels have been found in the waters of Wakulla Springs State Park south of Tallahassee, which is one of the largest and deepest freshwater springs in the world. This has apparently resulted in excessive growth of algae and exotic aquatic plant species, causing reduced clarity and changes in the spring’s ecosystem. Dye studies have confirmed that at least a portion of the nitrate comes from the Southeast Farm’s irrigated fields, although studies are on-going. As a result, in June 2006, the city of Tallahassee removed all cattle from Southeast Farm, eliminated regular use of nitrogen fertilizer on the farm, and implemented a comprehensive nutrient management plan for the farm.
For more information, see www.talgov.com/you/water/pdf/sefarm.pdf or U.S. EPA (2004).
Water Conserv II has been in existence since 1986, and is the first project permitted by the Florida Department of Environmental Protection for crops for human consumption. Over 3,000 acres of citrus groves are irrigated with reclaimed water, in addition to nurseries, residential landscaping, a sand mine, and the Orange County National Golf Center. No problems have resulted from the irrigation. The reclaimed water provides adequate boron and phosphorus and maintains soil at correct pH for citrus growth. The adequate supply of water permits citrus growers to maintain optimum moisture levels for high yields and ample water for freeze protection, which requires more than eight times as much water as normal irrigation.
Although Water Conserv II had historically provided reclaimed water to citrus growers for no charge, the project recently began charging for water. It’s unclear if citrus growers will continue to irrigate with reclaimed water, or whether Water Conserv II’s emphasis will change to providing reclaimed water for residential, industrial, and landscape customers.
For more information, see www.waterconservii.com/ or U.S. EPA (2004).
This publication was reviewed by Adria Bordas, Bobby Clark, Erik Ervin, and Gary Felton. A draft version was reviewed by Bob Angelotti, Marcia Degen, Karen Harr, George Kennedy, Valerie Rourke, and Terry Wagner. Any opinions, conclusions, or recommendations expressed in this publication are those of the authors.
www.watereuse.org/: WateReuse Association. “The WateReuse Association is a non-profit organization whose mission is to advance the beneficial and efficient use of water resources through education, sound science, and technology using reclamation, recycling, reuse, and desalination for the benefit of our members, the public, and the environment.” Page contains links to water reuse projects (mostly in the western U.S.), and other useful links.
www.cvco.org/science/vwea/navbuttons/Glossary-11-01.pdf: Virginia Water Environment Association’s Virginia Water Reuse Glossary.
www.hrsd.com/waterreuse.htm: Hampton Roads (Virginia) Sanitation District water reuse page. Description of industrial water reuse project, research reports, FAQ’s, and glossary of water reuse jargon.
www.floridadep.org/water/reuse/index.htm: Florida Department of Environmental Protection water re-use page. Links to many water reuse-related resources on site, including general education/information materials, and Florida-specific links on water reuse policy, regulations, and projects.
www.gaepd.org/Files_PDF/techguide/wpb/reuse.pdf: Georgia Department of Natural Resources Environmental Protection Division’s “Guidelines for Water Reclamation and Urban Water Re-Use (2002).
www.mass.gov/dep/water/wastewater/wrfaqs.htm: Massachusetts Department of Environmental Protection FAQ on water reuse.
www.bcua.org/WPC_VT_WasteWaterReUse.htm: Bergen County (New Jersey) Utilities Authority. Describes reuse of wastewater effluent re-use in cooling towers and for sewer cleaning.
www.owasa.org/pages/WaterReuse/questionsandanswers.html: FAQ about Orange Water and SewerAuthority’s (Carrboro, NC) water reuse project for the University of North Carolina at Chapel Hill.
Carrow, R.N. and R.R. Duncan. 1998. Salt-affected turfgrass sites: Assessment and management. John Wiley & Sons, Inc., New York, N.Y.
Crook, James. 2005. St. Petersburg, Florida, dual water system: A case study. Water conservation, reuse, and recycling: Proceedings of an Iranian-American workshop. The National Academies Press, Washington, D.C.
Florida Department of Environmental Protection. 2006. 2005 reuse inventory. FDEP, Tallahassee, FL. Available on-line at www.floridadep.org/water/reuse/inventory.htm.
Harivandi, M. Ali. 1999. Interpreting turfgrass irrigation water test results. Publication 8009. University of California Division of Agriculture and Natural Resources, Oakland, Calif. Available on-line at anrcatalog.ucdavis.edu/pdf/8009.pdf.
Harivandi, M. Ali. 2004. Evaluating recycled waters for golf course irrigation. U.S. Golf Association Green Section Record 42(6): 25-29. Available on-line at turf.lib.msu.edu/2000s/2004/041125.pdf.
Landschoot, Peter. 2007. Irrigation water quality guidelines for turfgrass sites. Department of Crop and Soil Sciences, Cooperative Extension. Penn State University, State College, Pa. Available on-line at turfgrassmanagement.psu.edu/irrigation_water_quality_for_turfgrass_sites.cfm.
Lazarova, Valentina and Takashi Asano. 2004. Challenges of sustainable irrigation with recycled water. p. 1-30. In Valentina Lazarova and Bahri (ed.). Water reuse for irrigation: agriculture, landscapes, and turf grass. CRC Press, Boca Raton, Fla.
Lazarova, Valentina, Herman Bouwer, and Akica Bahri. 2004a. Water quality considerations. p. 31-60. In Valentina Lazarova and Akica Bahri (ed.). Water reuse for irrigation: agriculture, landscapes, and turf grass. CRC Press, Boca Raton, Fla.
Lazarova, Valentina, Ioannis Papadopoulous, and Akica Bahri. 2004b. Code of successful agronomic practices. p. 103-150. In Valentina Lazarova and Akica Bahri (ed.). Water reuse for irrigation: agriculture, landscapes, and turf grass. CRC Press, Boca Raton, Fla.
Maas, E.V. 1987. Salt tolerance of plants. p. 57–75. In B.R. Christie (ed.) CRC handbook of plant science in agriculture, Vol. II. CRC Press, Boca Raton, Fla.
Metropolitan Area Planning Council. 2005. Once is not enough: A guide to water reuse in Massachusetts. MAPC, Boston, Mass. Available on-line at www.mapc.org/regional_planning/MAPC_Water_Reuse_Report_2005.pdf.
Reed, Sherwood C., Ronald W. Crites, and E. Joe Middlebrooks. 1995. Natural systems for waste management and treatment. 2nd edition. McGraw-Hill, Inc. New York, N.Y.
Sheikh, Bahman. 2004. Code of practices for landscape and golf course irrigation. In Valentina Lazarova and Akica Bahri (ed.). Water reuse for irrigation: agriculture, landscapes, and turf grass. CRC Press, Boca Raton, Fla.
USDA-NRCS. 2003. Irrigation water requirements. Section 15, Chapter 2. p. 2-i-2-284. In Part 623 National Engineering Handbook. U.S. Dept. of Agriculture Natural Resources Conservation Service, Washington, D.C. Available on-line at www.info.usda.gov/CED/ftp/CED/neh-15.htm.
U.S. EPA. 2003. National primary drinking water standards. EPA 816-F-03-016. U.S. Environmental Protection Agency, Washington, D.C.
U.S. EPA. 2004. Guidelines for water reuse. EPA 645-R-04-108. U.S. Environmental Protection Agency, Washington, D.C. Available on-line at www.epa.gov/ORD/NRMRL/pubs/625r04108/625r04108.pdf.
United States Golf Association. 1994. Wastewater reuse for golf course irrigation. Lewis Publishers, Chelsea, Mich. 294 p.
VAAWW-VWEA. 2000. A Virginia water reuse glossary. Virginia Section, American Water Works Association and Virginia Water Environment Federation. Available on-line at www.cvco.org/science/vwea/navbuttons/Glossary-11-01.pdf.
Wu, Lin, and Linda Dodge. 2005. Landscape plant salt tolerance guide for recycled water irrigation. Slosson Research Endowment for Ornamental Horticulture, Department of Plant Sciences, University of California, Davis, Calif. Available on-line at ucce.ucdavis.edu/files/filelibrary/5505/20091.pdf.
Reviewed by Greg Evanylo, Extension Specialist, Crop and Soil Environmental Sciences
Virginia Cooperative Extension materials are available for public use, re-print, or citation without further permission, provided the use includes credit to the author and to Virginia Cooperative Extension, Virginia Tech, and Virginia State University.
Issued in furtherance of Cooperative Extension work, Virginia Polytechnic Institute and State University, Virginia State University, and the U.S. Department of Agriculture cooperating. Edwin J. Jones, Director, Virginia Cooperative Extension, Virginia Tech, Blacksburg; Jewel E. Hairston, Administrator, 1890 Extension Program, Virginia State, Petersburg.
May 1, 2009