When gray equals green: Recycling water makes growing sense.
Reeves Journal recently covered the regulation side of gray water recycling (See Cracking the Code, “Alternatives are good: Saving the world safely with gray water,” September 2016). Now we’d like to provide an update on some of the latest trends in this arena.
Let’s be realistic. The average consumer still isn’t all that interested in finding ways to use their domestic water supply more than once. Say “gray water” and most folks are blissfully ignorant of what it is and why there’s talk about how it can be diverted away from the drain headed to the main sewer line, treated and then tasked to flush toilets or soak the landscaping.
But, if your home and its landscaping happen to be in California, and you’re currently allowed to water your lawn, trees and ornamental shrubs on two specified days a week, you’re probably looking at brown grass. Or, you’ve rolled up the turf and replaced it with a bed of colored gravel or vegetation that requires little or no water. Recycling potable water begins to sound pretty good. And, if you’re a builder or a large company anywhere in the West with acres of campus, water use is no small concern.
Where recycling can pay off
Experts suggest that major growth in the gray water recycling sector may come in new construction. Home builders are beginning to specify gray water recycling systems into housing developments. There’s also a push for corporations to install gray water systems in new facilities and during renovations in existing ones.
“San Francisco has passed very restrictive covenants regarding water conservation and that may be the model for the rest of the state sometime in the future,” says John Bauer, president of Water Harvesting Solutions, Hinsdale, Ill. “They are requiring NSF 350 water for commercial purposes, whether it’s rainwater, gray water or storm release. All commercial buildings must have some form of water reuse. That’s good for us because these systems tend to be expensive and they take several years to pay out so we really need that carrot and stick of the municipality to really get these going, to get enough of these systems out there to get costs down and to increase the experience level with them.”
A real obstacle to consumer acceptance of gray water recycling, the experts say, is that the cost of water hasn’t reached high enough levels to sound the cost alarms, much as it took escalating energy bills to wake consumers up to the need to look for energy-saving appliances and habits.
“You have to think about what motivates people; two things that really motivate them are fear and the pocketbook,” says Jeff Pringle, account manager at Orenco Systems in Sutherlin, Ore.
“I talk about environmental stewardship, and a lot of people have been pushing this for a long time, because of sustainability, and the warm and fuzzy feeling that you get from doing the right thing, but you’re not going to see a big push until there are other things that are driving it, from water costs to regulatory action,” Pringle says. “Several urban areas, especially in California, where water is more of an issue than other parts of the country, you have these pockets where regulatory agencies are very progressive and they are helping to drive it. You also have a lot of environmental groups that are trying to convince the legislators that they need to hurry up and drive it also.”
“I think you’ll see this happening fairly rapidly in California,” Bauer says. “They’ll see that ‘Hey, it’s too expensive today, but years from now it’s going to be required, and these buildings that are being constructed now will be active for 20 years or longer. That kind of regulatory legislation will be necessary to facilitate growth in this industry.
“In most cases, for homeowners who want to reuse gray water, the subsurface methodology makes the most sense. I don’t think there’s any issue with using substrate gray water for trees of any sort, but certainly with root crops, you would not want to use that water.”
Simple systems, “defined as gravity discharge from a single residential clothes washer with no storage”, are considered low tech, “but very effective, in limited irrigation applications”, says Doug Kirk, technical services supervisor for IAPMO. A simple system also is exempt from the formal permitting process.
“In general, while gray water systems may be promoted by state authorities, the local enforcement agencies, including the health departments, are not too eager to see them installed,” Kirk says. “There are many good reasons, but mostly because once the initial euphoria wears off, property owners may become less enthusiastic about maintenance. And maintaining these systems is crucial not only to be effective but safe in operation.”
In single residential houses, it sometimes can be cost prohibitive to do anything beyond simple gray water recycling, Pringle notes. “Anybody can use gray water in California, for example, as long as it’s subsurface. You can hook a pipe up to your washing machine and run it out to pipes buried a couple of inches deep. But, when you are talking about taking gray water and using it for toilet flushing or any above-surface irrigation, the water has to be treated. What you’re seeing, a lot of times, is that a system that will treat gray water to those types of standards is not cost-effective for a single residence.”
Encouraging to water re-use proponents is the trend for builders to specify plumbing for a gray water re-use system into the original construction plans, alongside the potable water and black water waste disposal systems, even if the system itself won’t be installed until later. If you’re selling a home for more than $500,000, adding a few thousand dollars to the price isn’t going to be as daunting as shelling out that much for a retrofit.
It’s been pointed out that there’s also an economy of scale, reducing the cost per unit if you’re talking about 30 to 100 homes rather than a single dwelling. Buyers also might like the idea of being able to maintain plantings and landscaping even during drought scenario water restrictions. It also could be a lot less expensive than re-landscaping if and when restrictions ease.
For example, San Diego-based Nexus eWater has designed gray water treatment systems to be included in the blueprints for the River Islands master-planned community in Northern California, as well as projects with other homebuilders in central California and San Diego.
More people, more water
“Our target customer would be commercial, typically multi-unit housing, where you have 500 to 1,000 gallons a day that you want to treat,” Bauer says. “First of all, you have to have a way of separating the waste stream from that building, the toilets going to black water, and the faucets, showers and clothes washers going to gray water. This is pretty much standard practice that’s been adopted by most states. It makes it very challenging to harvest gray water in an existing residence or an existing building, because in most cases that plumbing is very deep in the walls and it is prohibitively expensive to try and retrofit that.”
Orenco also sees increased activity on the commercial side.
“Multi-family is where we’re really seeing the growth,” Pringle says. “In an apartment building with multiple units, your price of treatment per gallon goes way down and you can more easily justify the return on investment.”
One example is the Cedar Springs affordable housing project in LaVerne, Calif., where an AdvanTex AX-Max system treats gray water from residents’ bathroom sinks, tubs and showers. The resulting high-quality effluent is then reused for toilet flushing and drip landscape irrigation.
There are two approaches for more complex gray water processing, Bauer explains, a bioactive methodology and a mechanical filtration process. Water Harvesting Solutions’ proprietary systems use a series of filtration and sanitation steps to process raw gray water from showers and sinks into clean, clear NSF‐350‐compliant, onsite-treated, non-potable water suitable for toilet flushing, surface irrigation and cooling tower make‐up. Raw gray water is treated as it is produced throughout the day so that no raw gray water sits for more than a few hours. Treated water is recirculated and kept pathogen-free before being pressurized to the non‐potable application.
Typically, only about a third of the shower and sink water from bathrooms is needed to flush all toilets 100% of the time, Bauer says. “That leaves additional processed gray water for irrigation or cooling tower make‐up. A typical multi-unit housing building — a dormitory or barracks or a hotel — can usually save 800,000 to two million gallons of municipal water per year by harvesting gray water for toilet flushing and irrigation.”
Orenco’s AdvanTex treatment systems use packed bed filter or attached growth biological treatment, Pringle explains. AdvanTex uses a processing tank and a control panel with a programmable dosing timer. In the treatment process, gray water is pumped to a distribution manifold in the treatment unit. The effluent percolates down through the media — textile sheets hung vertically in a fiberglass enclosure — where aerobic treatment occurs. The textile media’s complex fiber structure provides tremendous water-holding capacity and offers an extremely large surface area for biomass attachment. A percentage of the treated effluent is recirculated for dilution and additional treatment, and the remaining treated effluent is discharged for reuse.
Gray water is treated to reuse standards and can be stored in the AdvanTex unit or in a separate dose tank. “Ultraviolet disinfection is typically used to remove pathogens unless it is going to be used for subsurface irrigation,” Pringle says. “Since the grey water is treated, storage is not usually an issue. It is used before any storage issues occur, which is usually several weeks. Single units can treat from 800 to 11,000 gallons a day.”
Saniflo produces a wide range of gray water, or drain, pumps that allow individuals to collect gray water from faucets, washing machines and other plumbing-related fixtures, but not toilets or kitchen sinks, says Christopher Peterson, regional sales director, west coast, SFA Saniflo.
“Our pumps will discharge the gray water into a holding system without the need for gravity to be present,” he says. “Once the gray water is pumped to a holding station, it must be treated and filtered before reuse. Otherwise, the gray water can be pumped out into gardens, lawns, etc., with a proper system, such as a bio filter — always taking into account local building and health codes.”
Nexus eWater’s NEXtreater system takes grey water and cleans it up to the NSF/ANSI 350 standard, without the use of added chemicals or the use of a biological, says Bob Hitchner, chief sales and marketing officer, Nexus Water. Gray water leaves fixtures and moves into a collection tank, the NexCollector, which stages the water for batch processing. Water is pulled out 10 gallons at a time and then goes through a four-stage process.
First air and turbulence is introduced into the water so that soap and large contaminants float to the surface and are whisked away; next come two stages of filtration, to clean up and reduce the turbidity; the final step is a UV bulb for disinfection. The treated water is stored in the NEXservoir, a clean water tank to supply the water to the irrigation system.
The optional NEXheater unit uses a heat exchanger to extract and transfer the heat energy in the water, concentrates it and transfers it to fresh water inside the cylinder. That energy heats fresh new drinking water that comes in through the water heater.
"This article was originally posted on ww.reevesjournal.com."