Water Reclamation: Solutions for Today and Tomorrow

by Paul Greenwalt, EIT

This article is part of Wood Harbinger’s newsletter series.

I have a problem with knowledge. Once I know about something, I am unable to ignore it, look the other way, or even pretend to be uninterested. You might say it’s my own version of the Baader‑Meinhoff phenomenon. Fresh water is a finite and depleting resource on planet earth; fresh water demands are projected to increase over the next 30+ years and recent data shows we’re using up fresh water sources faster than they can be replenished.Water reclamation systems may be a solution to this crisis, if we act. There are many collection and distribution options, from small-scale rainwater harvesting applications at the residential and individual building level, to campus-wide greywater reuse systems, to imagining what it might take to introduce a city-wide distribution infrastructure change. As a mechanical designer, I work with plumbing designs on a regular basis, including distribution infrastructure and end-user fixtures. It is extremely difficult to ignore the fact that we use potable water for applications that could easily be served by reclaimed water. Why do we rush our perfectly clean water to the storm drain and then draw purified, fluoridated, potable drinking water just to flush it down the drain again?

What is water reclamation?

Water reclamation, or water recycling, is the process of capturing water that would have otherwise been waste and using it in another process, such as irrigation, flushing toilets, cooling or other industrial processes, and vehicle washing.

Popular water reclamation systems currently in residential and commercial use include rainwater harvesting and greywater harvesting systems. Rainwater harvesting systems collect, store, and distribute rainwater. Greywater systems collect, store, and distribute “gently used” wastewater from washing machines, dishwashers, bathtubs and showers, and bathroom and kitchen sinks.

Rainwater harvesting systems are practical option in areas that, you guessed it, get a lot of consistent rain. You’ll not be surprised to learn that we design them fairly often here in the Pacific Northwest. A few notable Wood Harbinger projects that have included rainwater harvesting are the Federal Way Public Schools’ Support Service Center, which uses rainwater for its bus wash system, reducing the facility’s potable water consumption by around 60%; the North Seattle College Health Science and Student Resource Building, which has 15,000 gallons of rainwater storage capacity to supply water for flushing toilets; and the Kirkland Justice Center, which uses harvested rainwater for site irrigation.

There are other water reclamation systems that aren’t widely used, whether because they’re cost prohibitive for a lot of applications, or there’s still public health and PR concerns to address. Take the closed-loop water collection and filtration system like the one used aboard the International Space Station or in the movie “The Martian”. This system collects “astronaut wastewater.” Yes, it’s exactly what you’re thinking. It sounds gross, but filtration and chemical treatment can yield perfectly safe potable water. Mechanically and chemically speaking, it is a viable solution. But it may take time (or absolute necessity) for a system like this to catch on in a more widespread way.

Implementing Water Reclamation Systems

While it rains in Seattle often, it doesn’t rain all that much. However, it is surprising that an environmentally conscious city like Seattle doesn’t have more water reclamation projects. One point of view is that it is almost more important for cities with lower annual rainfall to try to collect every ounce that they can. Reasons why new buildings in any city might not implement rainwater collection are most often cost based. It is either too expensive to dig for an underground cistern or the owner doesn’t want to sacrifice rentable square footage. There may not be incentives or code requirements that push owners to even think about adding it to their projects.

Implementing water reclamation can be very easy in a new construction project but offers great challenges when attempted in a renovation retrofit application. Several of our rain water harvesting projects over the years have taken up valuable square footage in the basement, parking garage, or outside of the building. These locations have a cost associated with them; either in usable building area or in added construction costs.

The trick is calculating collection and usage. If you collect it, you need to be able to use it, and if you need to use it, you need to be able to collect enough, or have the distribution infrastructure in place to support both greywater and potable water use. Of the relatively few cities that offer irrigation water as a utility, most of them are in highly agricultural areas where irrigation water is a necessary means to their economic ends. This provides some incentive for the ecologically-conscious owners to pursue their own water reclamation systems. Aside from being able to reach into nearby water sources, non-potable water treatment and distribution is not high on the utility company’s list of to-dos. It will probably take a change in code to incentivize utilities to add this service.

Storing and Treating Reclaimed Water

Storing the water is one challenge, but how to treat it and use it for other processes can be challenging as well. Some may require more water treatment than others. Some may not “require” treatment, but treatment may overcome the “ick” factor and help recycled water use catch on. For example, a client might want to filter the rain water before it goes into a toilet bowl. We had this happen on a project: in a meeting with a building owner, we discovered that there was a stigma against putting “dirty” water in toilets. The owner’s impression was that rain water is dirty and that their clientele would be offended by seeing brown water in the toilets. In past experiences, the owner had seen rain water used in toilets, but it was untreated water and looked very unsanitary.

Beyond perception, owners and design teams are faced with dividing the plumbing system into flush and flow systems. That is, fixtures that flow water (sinks, drinking fountains, and showers) must be potable water, but flush fixtures (toilets and urinals; no bidets!!!) can be graywater based. Instead of two pipes running out to each restroom, this system would require three: one for hot water, one for potable cold water, and the third for non-potable cold water. If this is an existing facility, it is a bit more challenging due to adding a third pipe into an already crowded wall cavity.

Retroactively adding storage is the most challenging piece of the puzzle. Getting creative: we can add interesting sculptures, raise the floor in certain areas, bury a cistern under the parking area or landscaping or sports field, create false columns, etc., to add storage where there previously was none. Once the water is collected, we will need to treat it and then pump it out to the point of use.

Benefits of Water Reclamation

Water reclamation is a great idea, especially when you pay for water and sewer services based on a single meter. This means that regardless of where your water goes you pay for both services. I will use the irrigation water example again. If you pay for 100 gallons of potable water and use 50 gallons on the lawn, then you have overpaid for sewer services by 50 gallons. If you use reclaimed water for irrigation instead, now you’re only paying for sewer services for water actually using the sewer. This is a big deal for our clients, especially K-12 school. Any project seeking LEED would seriously consider water reclamation.

Water Reclamation Systems of the Future

Using reclaimed water for irrigation on a large scale could be a real game changer, as agricultural uses account for nearly 70% of fresh water withdrawal. Cities like Pasco, Kennewick, and Richland, Washington have irrigation water as a utility offering to businesses and residential alike, but cities like Seattle, Tacoma, and Everett do not because they do not have a seemingly unlimited resource of freshwater like the Tri-Cities with the Columbia River. Massive collection with storage in reservoirs is the most likely solution, but finding the public land to be able to install or construct a lake is not very feasible. Small scale collection is much more reasonable, so we are tasked with incentivizing building and home owners to install these systems to cut back on our treated water consumption. Let’s get to work!

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