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Greywater Gone Wild

by Doug Pushard

I am fortunate to live in New Mexico, a state that allows and encourages greywater recycling on a small scale. Reusing greywater is a great way to conserve water. It also has some nice advantages —one can accurately predict the quantity a system will produce, plus it is rich in nutrients, which is great for landscaping. As a reminder, greywater is all water leaving the house that is not from the toilets or the kitchen.

Typically, greywater systems are simple and built on site with no controls and little filtration. In new homes, a greywater system is an easy, inexpensive add-on. In existing homes, however, it can range from simple to impossible.

Despite the fact that reusing greywater is an old technology that has been tried and true for decades, many states impose tight controls. In New Mexico and Arizona, you may recycle greywater on a landscape without a permit if you produce less than 250 gallons per day and install the system using published best practices.

This gallon limit is perfect for most residents — a two-person home, for example, might generate 100 gallons a day of total waste water (i.e., greywater and blackwater). For businesses, however, 250 gallons a day is way too little and a permit from the New Mexico Office of the State Engineer is required.

Most businesses do not want to consider these systems due to the requirements. Commercial greywater systems must have the ability to store greywater for longer periods of time, they must have the ability to move the greywater to the waste water stream if the greywater tank is overflowing, and they must control the bacteria growth in the holding tank to make sure it does not become anaerobic. These requirements and the historic lack of solutions have made installing large greywater systems undesirable if not impossible.

With water supplies diminishing around the world, however, views about greywater are changing. Solutions like the CT Graywater Recycling System from Conservation Technology utilize advanced technology to remove virtually all contaminants from greywater with a simple low maintenance, energy-efficient process. The filtration membranes have a pore size of 0.04 micron which is small enough to block 100% of bacteria and more than 99.99% of viruses, eliminating the need for disinfection. Water coming out of these filters can be stored for much longer periods of time and can be used in a much wider range of applications (e.g., toilets, urinals) than traditional greywater systems (landscaping only).

It is now technically feasible for a commercial establishment to install and maintain a large greywater system and reap the benefits for decades to come (i.e., no price increases, predictable water supply, and lower monthly operating costs). What’s more, since the water quality is so good, greywater and rainwater could be stored together to reduce costs.

Lee Jaslow, President of Conservation Technology and producer of the CT Graywater Recycling System, states, “The major cost of most rainwater systems, particularly in the western states, is storage. Rainwater systems in regions with seasonal rainfall that provide a substantial percentage of the annual water requirements of a building need a storage volume that is a substantial percentage of the annual rainfall. Since greywater is generated on a daily basis year-round, storage requirements are minimal, typically just a few hundred gallons for a residential system to a few thousand gallons for a commercial system. It just makes sense to combine these two storage systems.”

This filtration technology now makes high-volume greywater systems possible. In addition, these new, advanced systems can treat thousands of gallons of greywater a year, replacing the clean, filtered, potable drinking water that would have otherwise been used.

Installing an advanced system like this today requires passing through many regulatory hurdles, as our regulations have not caught up with this emerging technology. Not only is a State permit required for these large systems, but combining the storage of rainwater and greywater is not permitted, nor is the use of treated greywater allowed inside a building. However, as these regulatory issues are addressed, we can expect more of these systems to be installed, savings us millions of gallons of clean drinking water every year.

New technologies such as this advanced greywater recycling system will enable us to reduce our current water and energy footprint and become more sustainable in an environment of diminishing resources. The faster we adopt these new technologies, the better it will be for the current generation, future generations and our long-term quality of life.





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