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Home , Reclaimed water, Salinity, Wastewater treatment

Using Reclaimed Erin Ling, Sr. Extension Associate, Biological Systems Engineering Brian Benham, Professor and Extension Specialist, Biological Systems Engineering

Reclaimed water, sometimes referred to as landscape , is one way of reducing our use of “water ” or “recycled water,” is water existing potable water supplies. recovered from domestic, municipal, or industrial treatment that has been Reusing water helps to conserve treated to standards that allow it to be safely supplies by replacing the use of potable water with used for designated purposes. reclaimed water for uses such as irrigation and vehicle should not be confused with “wastewater,” washing . Reusing water also helps reduce untreated industrial or domestic environmental degradation by reducing the amount . However, “gray water,” untreated of reclaimed water (and the nutrients it contains) water from bathing or washing, is considered one directly discharged to , , streams, and form of wastewater (Water Reuse, VCE coastal —the traditional method of treated Publication 452-014). wastewater disposal. Reclaimed water contains - available nutrients at higher levels than are typically The level of treatment and disinfection reclaimed found in natural waters. High levels of nutrients can water receives is dictated by its intended (and cause when discharged to fresh and permitted) use. Many states encourage and coastal waters, which results in reduction of water promote the use of reclaimed water to conserve quality, and ultimately availability of to freshwater supplies and preserve rivers, streams, aquatic . When applied to the landscape, these lakes, and . same nutrients can be beneficial, and reduce the need for additional (U.S. EPA, 2004). Why use reclaimed water? However, landscape irrigation with reclaimed water While many states in the southeast receive large can still cause eutrophication of water bodies, when amounts of annual rainfall, periodic still nutrients are applied in excess of plant needs, or by occur. This was starkly demonstrated by a severe over-irrigation. in 2007 when Lanier, the main for the city of Atlanta, dropped to Traditionally viewed as a waste to be disposed of, record low levels. Combined with the increased reclaimed water is now being viewed as a valuable demand for fresh, clean surface and by conserving surface and groundwater as for public water supply, more widespread and well as for the supply of nutrients it contains. prolonged water shortages are expected if the current use of potable (drinking quality) water for What is reclaimed water and how is it produced? non-potable needs continues. Conservation There are three stages of : measures, such as using reclaimed water for primary, secondary, and advanced, sometimes called tertiary (Figure 1, next page). During primary

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treatment screening and remove Environmental Protection Agency has established suspended . Next is , guidelines to encourage states in establishing reuse where biological decomposition is used to programs. Many states have their own regulations decompose complex organic material into that specify how reclaimed water may be used and simpler forms. The water is then separated from the treatment and disinfection requirements for each the decomposed organic material and is either type of use. Reclaimed water that may come into disinfected—often by chlorination—and direct human contact is typically required to have the discharged, reused, or subjected to advanced most stringent treatment and disinfection, in order to treatment. Advanced treatment may be used to eliminate potential exposure to human . further remove solids, organic material, nutrients, or other chemicals using physical, Opportunities for using reclaimed water include chemical, or biological processes. After advanced irrigation, industrial cooling, and in some locations treatment the water is disinfected before being . The most common use is reused or discharged (typically to rivers, lakes, or irrigating public access areas, including residential coastal waters). areas, golf courses, athletic fields, parks, etc. Reclaimed water for public access area irrigation is Reclaimed water is treated wastewater that has supplied by a distribution system that is separate received, at a minimum, secondary-level from drinking water systems, so there is no danger of treatment and basic disinfection at a wastewater cross . This is sometimes referred to as treatment facility. The level of treatment it a dual-pipe system where both reclaimed and potable receives affects its nutrient levels (secondary- water are supplied by separate pipes. Some reclaimed treated water typically has significantly higher water is used for agricultural irrigation to grow feed, nutrient content than advanced-treated water). fiber, or other that are not for human However, the exact content will vary from utility consumption. In some locations reclaimed water is to utility. permitted for irrigation of crops for human consumption but must meet stringent treatment and disinfection requirements and is usually not allowed to come in direct contact with the edible portion of the . While these are examples of how reclaimed water is used in some locations, each state has its own permitted uses and treatment and disinfection requirements. Figure 1. The wastewater treatment process. Some or all of the (reclaimed water) can be reused. Advanced Considerations for using reclaimed water for treatment is an optional step in the treatment process. Disinfection occurs after advanced treatment in facilities landscape irrigation that use this step, otherwise disinfection occurs after Reclaimed water used for landscape irrigation must secondary treatment. meet stringent treatment and disinfection requirements, since it has the potential to come into How can reclaimed water be used? direct human contact. However, these requirements There are no federal regulations governing the are focused on human health, not the health of the use of reclaimed water. However, the U.S. environment. Reclaimed water can contain other

such as trace amounts of heavy (Crook, 2005), while several turfgrasses grown in the metals, pharmaceuticals, and personal care southeastern US have moderate to high products that were not removed in the treatment tolerance. Over irrigation of salt-sensitive plants process. From the perspective of landscape should be avoided, and periodic intentional health and environmental protection, the two should be used to prevent salt buildup. main issues that should be considered are the potential for salt buildup in the and for over- Nutrients application of nutrients, which could migrate to An often-overlooked aspect of reclaimed water is the bodies in runoff or leach to nutrients it contains, particularly and groundwater. . These nutrients can be detrimental when used for industrial purposes such as cooling water, since nutrients can encourage biological growth, Salinity, the amount of salt contained within the which can cause fouling. In these situations an water, may be the single most important additional treatment process is often used to remove parameter in determining the suitability of nutrients and avoid any problems. On the other hand, reclaimed water for irrigation (U.S. EPA, 2004). such nutrients can be beneficial when reclaimed Applying large amounts of high-salinity reclaimed water is used for irrigation and can supply a water can affect the salt content of the soil, significant portion of plant needs (U.S. EPA, 2004). which could then affect landscape plants. This can reduce the amount of applied . Note However locations which receive large amounts that supplemental fertilization may still be required of rainfall (which is very low in salinity) are less depending on the desired results. affected for two reasons: large and frequent rainfall events 1) reduce the need for irrigation The nutrient content of reclaimed water varies and 2) periodically leach from the soil, depending on the treatment processes used. In preventing accumulation. Evapotranspiration, the general, treatment plants using advanced treatment rate that water is removed from the soil by plant typically produce reclaimed water with lower nutrient transpiration and soil evaporation, can affect soil levels than those using secondary treatment. salinity by allowing salts to concentrate as water However, reclaimed water from plants using is removed. The effect of evapotranspiration is advanced treatment often contains higher nutrient more important in arid or semi-arid regions, levels than potable water. The nutrient content of where natural leaching are infrequent. reclaimed water varies from utility to utility and even Another important factor is soil texture. Sandy day to day. Check with your local treatment plant typically leach readily, while silty or clayey before using reclaimed water for irrigation. soils do not. Several turf grass experts have recommended Plants differ in their sensitivity to salinity, so the incorporating nutrients supplied from reclaimed salt content of reclaimed water should be water into fertility plans. These nutrients evaluated for appropriate use. For example, are believed to be efficiently used by turf grasses crape myrtle (Lagerstroemia sp.), azaleas since they are applied by irrigation on a regular basis, (Rhododendron sp.), and Chinese privet even if they are only present in low concentrations. (Ligustrum sinense) have fairly low salt tolerance Depending on the concentrations, using reclaimed

water has the potential to provide a significant fertilizer sources are used. Care should be taken in portion of the nitrogen, and potentially all of the eliminating over spray from irrigation systems using phosphorus, required by turf grass. Incorporating reclaimed water. nutrients from reclaimed water into the nutrient budget would also allow for the reduction of Summary and Conclusion high-dose applications in nitrogen, which in turn Using reclaimed water for uses that do not require can increase nutrient uptake efficiency and drinking quality water is an effective method of decrease potential environmental impacts. The conserving freshwater supplies. While reclaimed value of such nutrients can be an important water can be used for a variety of uses, the most economic consideration. When planning common is for landscape irrigation. When used for fertilization schemes it is important to account landscape irrigation special management may be for the timing of application, since the relatively required to prevent over application of nutrients in constant low dosage provided by irrigation with excess of plant needs and to prevent salt buildup in reclaimed water may not be optimal for a given the soil. plant. References Landscape fertilizer application rates should • Effluent water: Nightmare or dream come true? account for the nutrients supplied in reclaimed http://turf.lib.msu.edu/2000s/2000/000315.pdf water. This is of special importance in locations • Evaluating recycled waters for golf course irrigation. where nitrogen and phosphorus of http://turf.lib.msu.edu/2000s/2004/041125.pdf • Crook, J. , Reuse and . water is a concern. Special caution should be Florida, dual water system: A case study. taken when using reclaimed water in soils that do http://books.nap.edu/openbook.php?record_id=11241 not need phosphorus. As with other sources of &page=175 . pp. 175. plant nutrients, it is important to apply reclaimed • Understanding and guidelines to water appropriately. Over irrigating with management. http://turf.lib.msu.edu/2000s/2000/000914.pdf reclaimed water can contribute to salt • Water Reuse: Using Reclaimed Water for Irrigation. accumulation and application of nutrients in VCE Publication 452-014 excess of plant needs, particularly if other http://pubs.ext.vt.edu/452/452-014/452-014.html

DISCLAIMER – This document is intended to give the reader only general factual information current at the time of publication. It is not a substitute for professional advice and should not be used for guidance or decisions related to a specific design or construction project. This document is not intended to reflect the opinion of any of the entities, agencies or organizations identified in the materials and, if any opinions appear, are those of the individual author and should not be relied upon in any event. Updated May 2014.