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Graywater Treatment Using Constructed Wetlands
Citation:
Jokerst, A., M. Hollowed, S. Sharvelle, L. Roesner (retired), AND A. Rowney. Graywater Treatment Using Constructed Wetlands. U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-12/684, 2013.
Impact/Purpose:
Purpose is to inform the scientific and engineering community regarding the efficacy of treatment of graywater by constructed wetlands.
Description:
Mounting pressure to conserve water resources has prompted the notion that the separation of graywater from sewerage through the use of dual-plumbed systems may enable graywater to be reused at the household level for such non-potable demands as landscape irrigation or toilet flushing. Although graywater reuse holds great promise as a means to reduce potable water demands, water quality and health concerns arising from the level of contamination typically found in graywater have impeded the practice from gaining wide-scale application in the United States. Simple treatment schemes, such as those using constructed wetlands, could reduce graywater pollution and allow for expanded reuse applications. This report documents the results of a study examining the treatment efficiency of a pilot-scale constructed wetland system for graywater over a one-year period, and explores the potential for onsite reuse of the treated effluent for outdoor irrigation. The wide range of measurements taken, including those of anionic surfactants and of indicator microorganisms, provides a comprehensive assessment of the treatment efficiency and outflow water quality characteristics of such systems. Results of water quality measurements indicated that the constructed wetland substantially reduced organics, solids, nutrients, pathogens, and surfactants throughout the one-year sampling period. In particular, removal rates of biochemical oxygen demand and total suspended solids averaged 91% and 77% respectively, while removal of anionic surfactants averaged 94% and never dropped below seasonal mean of 88% throughout the year. The wetland reduced pathogenic indicator microorganism concentrations by approximately two orders of magnitude on average, producing effluent concentrations below primary contact standards for all seasons except winter. A comparison of the wetland effluent quality with state reclaimed water quality regulations indicated that effluent would typically meet reclaimed water quality standards for restricted irrigation reuse. However, treatment efficiencies decreased precipitously during winter months, producing an effluent likely unsuitable for unrestricted reuse.