Graywater Reuse May Make Sense In Drought-Stricken Regions

Graywater reuse projects in drought-stricken Georgia could help conserve a precious resource and identify a new installation service for septic system contractors.

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A few years ago, Georgia residents were suffering through one of the worst droughts in the state’s history. The reaction from Mercer University students, Habitat for Humanity and the state may change Georgia’s water rules and create a new service for companies that build and maintain decentralized wastewater systems.

The response from Mercer, in Macon, Ga., was to look for effective systems to recycle graywater, the slightly dirtied water that has been used to wash dishes, clothes or faces in a home. Students were interested in the topic, says Philip McCreanor, an associate professor of engineering and director of the Mercer engineering honors program. At the same time, the local Habitat for Humanity chapter was open to the idea, and it had homes ready for construction during the academic year so students could design the systems and help with the installation.

In the Habitat houses, a collection of tanks, pumps and distribution pipes bring much-needed irrigation to lawns and landscapes. For McCreanor and the State of Georgia, this is an experiment to see what types of graywater recycling concepts work.


It helped that Habitat was doing new construction. McCreanor’s students could design a graywater system without the complications of fitting it into an existing house. The complication they did face was creating a system both permanent and impermanent. “We had to build something that was permanent enough to last forever, but on the flip side it had to be removable so if we decided the experiment was not going the way we want, we could take it out without serious changes to the structure,” McCreanor says.

One of the experimental systems was installed about four years ago. The second went in during the spring of 2013. All graywater coming out of the homes is routed into above-ground tanks. These are easy to change for trying out other options, and if there was to be some failure of the system, water would flow by gravity into the city sewer.

There are two tanks, each 225 gallons. One serves as a settling tank and overflows into the second, which is a dosing tank. The first system, which went in about four years ago, incorporates a bristle filter. The second uses a Tuf-Tite EF-4 filter. Using different filters is part of the experiment. McCreanor suspects the characteristics of solids in graywater are different, and lint in particular will settle less readily than solids in blackwater.

One concern is to keep the graywater moving because if it sits too long it turns septic. It needs to sit more than a day but less than a week to promote settling but avoid the onset of anaerobic decomposition. The dosing tank is a demand system. A timed-dose system could be filled beyond capacity if residents did several loads of laundry before the dosing pump came on, McCreanor says.

From the dosing tank, water goes into standard drip tubing, 800 to 1,000 feet of Geoflow. The amount of tubing was calculated with standard numbers that assume usage of so much water per person per day from a house of a certain size. At this point it looks like the systems are oversized by 50 to 75 percent, McCreanor says. A five-bedroom, seven-occupant property has a low-flow washing machine that puts out only about 10 gallons of water per load instead of the approximately 50 that is typical.

The dripline is set up for a constant forward flush to scour solids from the tubing. This required only a slightly larger pump and saved money by eliminating the solenoid valves and controller required for a timed back-flush, McCreanor says.

At the outset, the design team did consider reusing the graywater inside the homes, he says, but they abandoned the idea because of the cost of putting graywater and potable water supply lines next to each other. If graywater was to be used for flushing toilets, a potable supply line would be required in case the graywater reserve was depleted. That means a level-control system and a back-flow preventer for starters. Recycling graywater for laundry would create an issue of clothes picking up scent from lint. Utilizing the graywater for landscape irrigation eliminated such concerns.


When the State of Georgia granted McCreanor permission to run experiments, it was looking for results to inform its rule making, says Chris Kumnick, program director for land use in the state Department of Public Health. Alterations suggested by McCreanor’s work may be quickly incorporated into Georgia’s Manual for On-site Sewage Management Systems. The Legislature left that responsibility with the department and its 15-member technical review committee composed of three state regulators and various outside professionals, such as a developer, an installer, an engineer, an environmental health specialist and a soil scientist.

There are already rules for graywater reuse, but the severe drought and concerns about the effects of climate variability are causing people to rethink those, Kumnick says. The manual currently allows a single-compartment, 500-gallon tank minimum for graywater, and while subsurface drip irrigation is allowed, water used for that purpose must be aerobically treated.

“So Phil was looking at the rules and questioning them,” Kumnick says. “He wanted to put a system in the ground and play with it. What happens when you modify the minimum tank size? What happens when you modify the treatment? So he’s trying different things to maybe reduce the cost and get the same performance.”

Some manufacturers have wanted experimental approval for products but have objected to the amount of information they must accumulate and the amount of time needed to do that, Kumnick says. But Georgia has geology that varies from mountainous to ocean beach, and an experimental system running in one region for a few months will not provide enough information to predict its effectiveness when used across the state and justify a change in the rules, he says. Another benefit of McCreanor’s project is its survey of the actual user activity, he says; for example, how often they clean a washing machine filter.

McCreanor challenged the assumptions in the current rules, and Kumnick says that’s good because the state does not have the manpower or time to review everything. “We encourage people to bring up this or that sentence. If someone really isn’t challenging or pushing, we’re not looking into it.”


For customers, the benefits of McCreanor’s work may come in the form of a more economical and intelligent way to manage water.

Under current rules, graywater systems are not cost-effective for single-family homes, says Matt Vinson, who owns Vinson Septic Solutions, and who installed the Aquaworx Intelligent Pump Controller panel that runs one of McCreanor’s graywater systems. For larger structures – multifamily homes, commercial buildings – reuse is economical and seems to be gaining in popularity, Vinson says.

Dart Kendall, who owns Advanced Septic in Acworth, Ga., and donated the Geoflow tubing for McCreanor’s project, sees great potential in graywater reuse systems. This is a technology installers should get behind, he says, because drip irrigation provides much better water use. Installers should also become involved with regulators now to make sure rules are well-written and to avoid the greater trouble of trying to revise them later.

Kendall envisions great possibilities for onsite installers to promote graywater systems to complement decentralized wastewater treatment systems and public sewers, essentially finding far broader markets for their services and helping conserve reuse of a precious resource.

As McCreanor’s work in a sewered area demonstrates, Kendall says, “There’s a potential for septic tank guys to turn right around and go back into the areas we lost to sewers.”


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