Author: Nick Andrews, Small Farms Program, Oregon State University
Publish Date: Winter 2012
Reuse of graywater reduces demand on other sources including potable water, surface water and ground water. The Department of Environmental Quality recently adopted new rules for a new statewide program for permitting graywater use and disposal systems. These rules allow for some use of graywater in irrigation systems.
Graywater includes bath, bathroom sink, kitchen sink and laundry wastewater, but not garbage waste or wastewater contaminated by soiled diapers. Graywater can contain organic matter, suspended solids and potentially pathogenic organisms, so approved uses are restricted. When appropriately collected and handled graywater can be reused for flushing toilets and urinals as well as irrigating certain trees and plants.
Oregon’s rules recognize three different types of graywater. Type 1 is graywater that is untreated or has passed through a physical process to remove solids, fats, oils and grease. Type 1 graywater is the lowest quality and may be used only for subsurface irrigation.
Type 2 graywater is treated by a chemical or biological process to reduce total suspended solids and organic matter concentrations. Because this type of graywater is stabilized through treatment, it may be used for drip irrigation and in landscape ponds. Type 3 graywater is treated to type 2 standards and disinfected to reduce bacteria and other potential pathogens. Because of its high level of treatment, type 3 graywater is suitable for additional uses, such as sprinkler irrigation and dust control.
Anyone planning to reuse graywater must first get a DEQ permit. Three tiers of permits are available depending on the type and amount of graywater generated. Tiers 1 and 2 are general permits. Tier 1 is for single family residences and duplexes that generate less than 300 gallons per day of type 1 graywater for use as subsurface irrigation of landscape plants or compost. Tier 2 is available for any structure that generates less than 1200 gallons or type 1 or type 2 graywater per day. Tier 3 is an individual permit for any system not eligible under a tier 1 or 2 general permit. It is more expensive and requires additional information.
DEQ will begin accepting applications for graywater reuse and disposal systems in the spring of 2012. Additional information is available through their website: http://www.deq.state.or.us/wq/reuse/graywater.htm. (adapted from DEQ website)