We began research and development of graywater reuse combined with aquaponics in 2012. Graywater is defined as wastewater stemming from household sinks, baths, showers, dishwashers, and clothes washers. Aquaponics refers to a food growing system which utilizes an inhabited fish aquarium for irrigation and fertilization of edible plants. Our pilot location was a 1920's apartment with twelve foot ceilings. The concept was to capture wastewater exiting the kitchen sink in a bucket, then hoist the bucket to a high spot where we could slowly drain the bucket into a wetland system and ultimately into the fish tank. Water from the fish tank, meanwhile, would be pumped up and into a series of grow beds above the tank, slowly draining excess water back into the tank.
|The kitchen before system construction|
|Weight bearing ledgers installed|
Our first order of business was to fully inspect the proposed area's structural integrity. After poking around in the ceiling and walls, we were able to confirm that the building was 'over built' - structural timber was plentiful and cheap in 1920s Missoula.
By placing weight-bearing ledgers perpendicular to wall joists, we would be able to space the weight of the structure across the wall. Once the ledgers were up, it was time to create and install the wetland graywater system.
The wetland graywater system consisted of a series of specialized PVC pipes filled with medium, which would serve as a surface for bacteria and stability for the wetland plants. Again, unfortunately, I did not think to take photographs as I was building the pipes or, as I like to call them, biofilters. (The creation of this blog is helping me realize the necessary steps to have more valuable content.) We utilized three types of biofilters, each having a slight difference in construction, but all having a very similar interior filter design. By placing a stainless steel insert into the center of a tube, we were able to force the water down one side of the pipe and up the other. We were able to modify this approach by simply adding a smaller diameter pipe inside the tube, forcing the water to travel down the inside pipe and then back up in the area between the two pipes. In my opinion, this was the best filter model, as it requires little effort to build and lessens the chance for leakage. Another model featured a smaller diameter pipe with a U shape; however, this filter proved to be the most troublesome of the bunch - I'm not sure if it was the diameter difference or just an inappropriate attempt, but several times the pipe leaked. If I were to set this system up again, I would certainly not include it. Into each filter we fitted two outlets - a bib, or valve, near the bottom for draining and water sampling; and a barb adapter near the top for overflow.
|Biofilters attached to the ledgers|
|Drain bucket, plants, and lights installed|
With the filters in place, we added a three-way valve under the sink that allowed us to divert water to a bucket or the sewer. Once the bucket was filled or, once a day, it was moved to the top of the system and allowed to drain into the first filter. As the wastewater left the bucket, the incoming water displaced biofiltered water up and out of the first tube and into the next by way of the overflow adapter. This water then displaces water in the next tube and so on until the bucket drains and additional overflow from the final filter enters the fish tank.
Unfortunately, or fortunately, depending on how you look at it, I was beckoned to a new location and the project halted after about 2 months. We never installed the planter shelves that would support edible plants watered from the fish tank, as I made the decision to move into another house that was attached to a wonderful yard (and thus the food forest was born ... but more on that later). However, I wanted to share this experience with anyone interested as it was a successful means to treat household wastewater and we certainly would have been able to grow food, while decreasing the volume of wastewater leaving the house. We'll pick this project back up again at some point, whether it be another in-home system or a larger greenhouse demonstration project. Stay tuned!