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However, when adequately designed and installed, a decentralized wastewater system can process large amounts of wastewater through the underlying soils, making it one of the most passive, sustainable forms of aquifer recharge. Rather than partially to fully treating wastewater effluent, then discharg- ing it to a surface pond or injection well before recharging the aquifer, decentralized systems provide both wastewater treatment and ground- water recharge in one step. Figures 1 and 2 show the groundwater deficits in the United States and the decentralized utilization rates for each state, respectively. In general, areas in dark red on the groundwater storage map correlate with areas of light decentralized utilization, as well as the opposite; a general correlation can therefore be made between low septic utilization rates and groundwater depletion. While other factors greatly impact groundwater depletion (e.g., precipitation, urbanization, and agricul- tural practices), the figures can be interpreted to show that decentralized wastewater treatment has an impact on groundwater storage. Applicability Of Decentralized Wastewater Treatment As technology continues to advance, an increasing number of sites have become viable candidates for decentralized systems. For example, designing a small-scale, advanced treatment train prior to dispersal of the effluent into the native soil can decrease both the absorption area and depth to limiting layers that are required for adequate treatment. This has allowed decentralized systems to be placed in areas previously inaccessible, in turn increasing the volume of groundwater recharge associated with decentralized systems. While traditionally thought of as a low-flow wastewater treatment solution, decentralized systems can be designed to treat any volume of wastewater. Community decentralized systems are being designed and used increasingly where lot sizes or site conditions limit the use of individual on-site wastewater treatment systems. Large systems can also be developed for large flow commercial and industrial sites, decreasing the hydraulic and nutrient stress placed on centralized wastewater treat- ment plants. Decentralized systems are conventionally managed by individual homeowners, who can be undereducated or unable to adequately main- tain their systems; this is a main reason why the decentralized model is often immediately dismissed. This is also changing. Centrally man- aged decentralized wastewater treatment systems, such as publicly and privately owned community systems, are being staffed with trained and educated personnel in the same manner as centralized systems. Case Study: Loudoun County, Virginia Loudoun County, VA has adopted a combined approach to wastewater treatment, utilizing both centralized and community decentralized treatment facilities. Community decentralized treatment facilities are publicly owned and maintained by Loudoun Water in the same man- ner as the county's centralized treatment plant. As the county continues to grow, developers integrate new community decentralized facilities then transfer ownership and operation to Loudoun Water. All homes connected to the community systems pay taxes and fees matching those paid by homes connected to the centralized system, which allows sus- tainable operation and maintenance. One of the subdivisions serviced by decentralized wastewater treatment is Elysian Heights. This waste- water treatment system was designed to serve a 324-home subdivision and 5 acres of commercial land. For more information on the Loudoun Water decentralized systems, visit www.loudounwater.org. Conclusion Decentralized wastewater treatment can provide equal or better protection of public health while outshining cen- tralized wastewater treatment in environmental protection. Where individual lots are not suitable for decentralized treatment on site, community decentralized systems can pro- vide sustainable and respon- sible wastewater treatment. Decentralized systems pro- vide a low-cost, environmen- tally friendly, passive form of both wastewater treatment and aquifer recharge, combat- ting the declining groundwa- ter table and protecting public health. n 42 wateronline.com n Water Innovations DECENTRALIZEDSYSTEMS Jessica L. Kautz, EIT ( jkautz@infiltratorwater.com) recently joined Infiltrator Water Technologies as a project engineer after graduating with her M.S. in Civil and Environmental Engineering from the Colorado School of Mines and her B.S. in Civil Engineering with an Environmental Concentration from the University of Hartford. Kautz has spent her time at Infiltrator working closely with both the Research & Development and Science & Government Affairs departments to research, develop, and gain approval for new products. About The Author Figure 2. Decentralized wastewater treatment utilization in the continental U.S.