As a follow up to OLR memo 2000-R-0666, you asked what sorts of pretreatment technologies are required or allowed in those states that allow graywater to be used for agricultural purposes. Graywater is generally defined as wastewater from residential and other sources, other than from toilets and certain other fixtures.

SUMMARY

Of the states discussed in OLR memo 2000-R-0666, Arizona, California, Florida, Texas, and Washington allow treated graywater to be used for agricultural purposes, most commonly irrigation. Arizona does not specify the type of technology required, but instead has water quality standards for treated graywater. In California, the type of treatment systems required is determined on a case-by-case basis. This is also true for smaller systems in Florida; larger systems must include secondary treatment, e.g., a septic system and sand filter. In Washington, the graywater must undergo treatment in a septic system or comparable system. Texas requires secondary treatment through a sand filter for most applications. Texas and Washington have less restrictive requirements for the treatment of graywater from washing machines.

Oregon discourages the reuse of graywater from residences. It allows reclaimed water from sewage treatment facilities to be used for various purposes, with the level of treatment tied to the specific use.

In Virginia, the existing graywater reuse guidelines do not specifically address agricultural uses. Instead, they allow graywater to be used for subsurface applications such as drip irrigation after it flows through a filter membrane. The guidelines discourage surface application of graywater. The Department of Health anticipates that the issue of agricultural uses will be addressed in the guidelines that it is developing in response to 1999 legislation.

Of the other states discussed in the earlier memo, Missouri has no design recommendations or regulations governing graywater systems. Hawaii's law does not cover agricultural uses of graywater. Regulations and other provisions applying to the use of graywater generally are discussed at http://www.weblife.org/humanure/appendix3.html.

ARIZONA

Under Arizona law, the Department of Environmental Quality must approve the design and construction of graywater systems, including their pre-treatment components. Septic systems can be used for systems that have a capacity of 2,000 gallons or less per day (Ariz. Admin. Code § 18-9-701 et seq., http://www.sosaz.com/public_services/Title_18/18-09.htm).

Graywater may be used for various agricultural purposes. The regulations provide limits for fecal coliform and pH (acidity/alkalinity) for specific uses such as irrigation of food crops and livestock watering, as well as for water that comes into direct contact with people. Graywater reclaimed from residential buildings must also meet limits for chlorine. Irrigation sites must be designed to contain the maximum amount of rain experienced over any 24-hour period in the past ten years.

CALIFORNIA

California distinguishes between graywater, produced by residential buildings, and reclaimed water, produced by sewage treatment plants. Under Cal. Admin. Code, Title 24, Part 5, the type of graywater system allowed in a particular case is determined on the basis of location, soil type, and ground water level (http://wwwdpla.water.ca.gov/urban/land/revisedgwstand.html).

Graywater's agricultural use is limited to subsurface irrigation through drip or mini-leachfield systems. A drip irrigation system must have a surge tank of 50 to 100 gallons to collect the graywater.

When the water reaches a certain level, it is pumped from the tank through the drip irrigation system. Surge tanks installed above ground must have an overflow connected to a septic tank or sewer line. With a mini-leachfield irrigation system, a surge tank is not required and the graywater flows directly into the leachfield. Both approaches require use of a filtration system.

Graywater cannot be applied above the land surface or allowed to surface. It cannot be discharged directly into or reach any storm sewer system or any surface water of the United States. Graywater cannot be used for vegetable gardens. Graywater systems are not allowed where the lot is not large enough or has inappropriate soil conditions to absorb the graywater, as determined by the city or county.

The systems must be designed to accept all graywater connected to the system from the building. Permits for graywater systems cannot be issued until a plot plan with appropriate data satisfactory to the city or county has been submitted and approved. Cities and counties can accept the state's standards or establish their own, using the state's minimal standards as a base. They can decide to ban graywater use altogether.

Reclaimed water must undergo tertiary treatment. In addition to extensive filtration, the water must be disinfected by chlorination or ozonation. The water can be used for agricultural irrigation, including use on crops.

FLORIDA

The Department of Health has jurisdiction over residential graywater systems with a capacity of up to 10,000 gallons per day and commercial systems with a capacity of up to 5,000 gallons per day. The department allows graywater to be used in drip irrigation systems. It does not specify the pre-treatment technologies to be used in such a system, but instead requires that a professional engineer design the system.

The Department of Environmental Protection has jurisdiction over larger wastewater facilities. In most circumstances, such facilities must provide secondary treatment of wastewater. New facilities and modifications of existing facilities must be designed to achieve an effluent which (1) contains not more than the maximum concentrations allowed by regulation for suspended solids and contaminants contributing to biological oxygen demand or (2) has had 90% of each of these pollutants removed from the wastewater, whichever is more stringent.

In the case of subsurface irrigation systems, the reclaimed water cannot contain more than 10 milligrams per liter (mg/l) of total suspended solids (TSS) at all times, unless the system has been designed to provide specific flexibility and reliability in operation and maintenance. In addition, the reclaimed water must be disinfected and have its pH controlled.

Reclaimed wastewater can be used for both agricultural irrigation (including food crops) and landscape irrigation (including golf courses, cemeteries, highway medians, parks, and residential properties). Both surface and subsurface application technologies are permitted. For surface applications, more stringent filtration and disinfection requirement apply. Filtration achieving a maximum TSS level of 5 mg/l must occur before disinfection.

OREGON

Oregon defines graywater as a type of sewage (ORS § 454.605). It allows the discharge, but not reuse, of graywater from residences so long as the soil and site conditions comply with Department of Environmental Quality rules regarding subsurface sewage disposal systems. The system must include a pretreatment facility such as a septic tank. Such systems may use a drainfield two-thirds the normal size (ORS § 454.610).

Oregon also has extensive regulations regarding the use of reclaimed water from sewage treatment plants. The type of treatment required depends on the end use of the reclaimed water. For example, wastewater that has undergone biological treatment but no further treatment can only used to irrigate commercial timber, fodder, and fiber crops. Water used to irrigate pastures, sod farms, and food crops that will undergo further processing must also be disinfected. Food crops that will be eaten without further processing must undergo the highest level of treatment, including filtration and clarification (Ore. Admin Rules. § 340-55-015).

TEXAS

In Texas, treatment and disposal of graywater is the same as blackwater, except in the case of laundry graywater (30 Tex. Admin. Code § 285). The law applies to flows of 5,000 gallons per day or less. Larger flows undergo a separate permitting process by the Texas Natural Resource Conservation Commission (TNRCC).

The standard treatment is a septic tank followed by a sand filter. The sand filter consists of a layer of coarse porous material above a bed of sand. The treated wastewater is collected at the bottom of the sand filter and discharged, via gravity or pressure, via an appropriate disposal method. In addition, grease interceptors must be used on kitchen waste-lines from institutions, hotels, restaurants, and other places that may discharge large amounts of greases and oils to the sewage facility. Grease interceptors must be structurally equivalent to septic tanks

So long as blackwater or graywater is treated to secondary effluent standards, it may be used for surface irrigation. Treated effluent must be disinfected before it is applied to the surface. Approved disinfection methods include chlorination, ozonation, or ultraviolet radiation. To use graywater for landscape irrigation, homeowners must properly size the area based on water requirements for the landscape and time of year. The Texas A&M Website has an article on the use of graywater for agricultural irrigation, including design considerations. The article is at http://twri.tamu.edu/twripubs/Insights/v9n2/article-2.html

The TNRCC has written regulatory guidance that allows residential laundry washing machines to discharge directly onto the ground if the following conditions are met:

1. the discharge may not create a public health nuisance,

2. the area where the water is discharged must be supported with plant growth and have limited access,

3. water in which soiled diapers have been laundered may not be discharged,

4. water must not pool or run off, and

5. a lint trap must be installed at the end of the discharge pipe.

WASHINGTON

Graywater systems are treated virtually the same as combined-wastewater on-site sewage systems. The state has specific provisions for seasonal graywater systems and systems that only handle graywater from washing machines.

Graywater systems generally must use a septic tank for pre-treatment, although the local health authority can approve other pre-treatment methods.

Because a graywater system produces less wastewater than a combined system, its septic tank and subsurface drainfield can be smaller than those in a combined system.

On-site graywater systems must provide permanent, year-round treatment and disposal of graywater unless this is already provided by another approved on-site system or a connection to a public sewer. Graywater on-site systems must be installed with a means of sewage treatment for blackwater approved by the local health officer. Systems that reuse graywater off-site must at least meet these requirements. Graywater exceeding residential contamination levels must receive pre-treatment to at least residential levels.

The drainfield can be designed and located to reuse graywater for subsurface irrigation. The graywater may be used to irrigate trees (including fruit trees), shrubs, flowers, lawns and other ground covers. If potable water is used to augment graywater for irrigation using the same distribution network, it must have a method of backflow prevention approved by the local health officer. Graywater cannot be used for watering food crops or vegetable gardens, surface or spray irrigation, and certain other purposes.

In some areas, graywater drip irrigation or conventional drainfield trench systems would have to be buried too deep in order to protect against frost to be useful for irrigation. In these areas, local health officers may permit seasonal systems. In such systems, a shallow drainfield provides seasonal subsurface irrigation with graywater while a deeper drainfield or other approved sewage system provides year-round treatment and disposal. Where seasonal systems are allowed, both drainfields must meet state and local rule requirements to assure treatment and disposal at least equal to that provided by conventional on-site sewage systems. Seasonal systems must include a three-way valve to divert graywater to the year-round disposal field or sewer when needed, i.e., when freezing is a problem.

Local health officers may also permit "laundry wastewater only" graywater disposal or reuse systems for single-family homes. Such systems may have a single compartment retention/pump tank, with a minimum liquid capacity of 40 gallons, in lieu of the regulation's tank provisions. The tank must be warranted by the manufacturer for use with wastewater and meet requirements listed in the Uniform Plumbing Code. The minimum design flow for such systems, for the purpose of sizing the drainfield, must be based on the number of bedrooms in the residence and must be at least 30% of the minimum graywater system design flows.

A wastewater filter or screen (with a maximum size opening of 1/16 inch) must be provided in an accessible location conducive to routine maintenance. Specific requirements vary according to the county where the system is located and the specific type of system.

KM:ts