Simple Soilbox Graywater Filter System

Figure 9.11

sand outlet gravel stone perforated graywater injection pipes gravel stone perforated graywater injection pipes of the microscopic plants are algae, which can be either single cell (such as Chlorella or Euglena) or filamentous (such as Spirulina or Spyrogyra).

Macroscopic (larger) plants can grow under water (submergent) or above water (emergent). Some grow partially submerged and some partially emerged. Some examples of macroscopic aquatic plants are reeds, bulrushes, water hyacinths and duckweeds (see Figure 9.7). Submerged plants can remove nutrients from wastewater, but are best suited in water where there is plenty of oxygen. Water with a high level of organic material tends to be low in oxygen due to extensive microbial activity.

Examples of floating plants are duckweeds and water hyacinths. Duckweeds can absorb large quantities of nutrients. Small ponds that are overloaded with nutrients such as farm fertilizer runoff can often be seen choked with duckweed, appearing as a green carpet on the pond's surface. In a two and a half acre pond, duckweed can absorb the nitrogen, phosphorous and potassium from the excretions of 207 dairy cows. The duckweed can eventually be harvested, dried, and fed back to the livestock as a protein-rich feed. Livestock can even eat the plants directly from a water trough.22

Algae work in partnership with bacteria in aquatic systems. Bacteria break down complex nitrogen compounds and make the nitrogen available to algae. Bacteria also produce carbon dioxide which is utilized by the algae.23

Soilboxes or Soilbeds

A soilbox is a box designed to allow graywater to filter through it while plants grow on top of it (Figure 9.11). Such boxes have been in use since the 1970s. Since the box must be well-drained, it is first layered with rocks, pea gravel, or other drainage material. This is covered with screening, then a layer of coarse sand is added, followed by finer sand; two feet of top soil is added to finish it off. Soilboxes can be located indoors or outdoors, either in a greenhouse, or as part of a raised-bed garden system.24

Soilboxes located in indoor greenhouses are illustrated in Figures 9.8 and 9.10. An outdoor soilbed is illustrated in Figure 9.9.


An acid spring choked with long, slimy, green algae flows past my house from an abandoned surface coal mine. I introduced baby ducks to the algae-choked water, and quite by accident, I found that the algae disappeared as long as I had ducks swimming in the water. Whether the ducks were eating the algae or just breaking it up paddling their feet, I don't know. In any case, the water changed from ugly to beautiful, almost overnight, by the simple addition of another lifeform to the wetland system. This indicated to me that profound changes could occur in ecological systems with proper — even accidental — management. Unfortunately, constructed wetland systems are still new and there isn't a whole lot of concrete information about them that is applicable to single family dwellings. Therefore, I was forced, as usual, to engage in experimentation.

I built a clay-lined pond near my house about the size of a large swimming pool, then diverted some of the acid mine water to fill the pond. I directed my graywater into this "modified lagoon" wastewater system via a six inch diameter drain pipe with an outlet discharging the graywater below the surface of the pond water. I installed a large drainpipe assuming it would act as a pre-digestion chamber where organic material could collect and break down by anaerobic bacteria en route to the lagoon, like a mini septic tank. I add septic tank bacteria to the system annually by dumping it down the household drains.

Bear in mind that we use a compost toilet and we compost all other organic material. What goes down the household drains is bath water, sink water and laundry water. We do use biodegradable soaps, but do not use an in-sink garbage disposal. Scientific research shows that such source-separated, graywater has the same or better quality than municipal wastewater effluent after purification. In other words, source separated graywater is arguably environmentally cleaner than what's discharged from wastewater treatment plants.25

I assumed that the small amount of organic matter that entered the pond from the graywater drain would be consumed by the organisms in the water, thereby helping to biologically remediate the extensively damaged acid mine water. The organic material settles into the bottom of the pond, which is about five feet at the deepest point, thereby being retained in the constructed system indefinitely. I also lined the bottom of the pond with limestone to help neutralize the incoming acid mine water.

The ducks, of course, loved the new pond. They still spend countless hours poking their heads under the water, searching the pond bottom for things to eat. Our house is located between our garden and the pond, and the water is clearly visible from the kitchen sink, as well as from the dining room on the east side of the house, while the nearby garden is visible from the west windows. Shortly after we built the pond, my family was working in our garden. Soon we heard the loud honking of Canada geese in the sky overhead, and watched as a mating pair swooped down through the trees and landed on our new, tiny pond. This was quite exciting, as we realized that we now had a place for wild waterfowl, a bonus we hadn't really anticipated. We continued working in the garden, and were quite surprised to see the geese leave the pond and walk past our house toward the garden where we were busy digging. We continued to work, and they continued to walk toward us, eventually walking right past us through the yard and on to the far end of the garden. When they reached the orchard, they turned around and marched right past us again, making their way back to the pond. To us, this was an initiation for our new pond, a way that nature was telling us we had contributed something positive to the environment.

Of course, it didn't end with the two Canada geese. Soon, a Great Blue Heron landed in the pond, wading around its shallow edges on stilt-like legs. It was spotted by one of the children during breakfast, a mere fifty feet from the dining room window. Then, a pair of colorful wood ducks spent an afternoon playing in the water. This was when I noticed that wood ducks can perch on a tree branch like a songbird. Later, I counted 40 Canada geese on the little pond. They covered its surface like a feathery carpet, only to suddenly fly off in a great rush of wings.

We still raise a few ducks for algae control, for eggs and occasionally for meat. At one point we raised some Mallard ducks, only to find that this wild strain will fly away when they reach maturity. One of the female Mallards became injured somehow, and developed a limp. She was certainly a "lame duck," but the children liked her and took care of her. Then one day she completely disappeared. We thought a predator had killed the defenseless bird and we never expected to see her again. To the children's delight, the following spring a pair of wild Mallard ducks landed on our little pond. We watched them swim around for quite some time, until the female came out of the water and walked toward us. Or, I should say, "limped" toward us. Our lame Mallard duck had flown away for the winter only to come back in the spring with a handsome boyfriend! Our graywater pond was the point of reference for her migration.

My youngest daughter was given a Canada goose to raise. The tiny gosling couldn't have been more than a day or two old when it was discovered by one of the neighbors wandering lost along a roadside. Phoebe named the goose "Peepers," and everywhere Phoebe went, Peepers followed. The two of them spent many a day at the graywater pond — Peepers splashed around in the water while Phoebe sat on the shore watching. Soon Peepers was a full grown goose and everywhere Peepers went, large piles of goose droppings followed. The goose doo situation became so intolerable to Dad that he renamed the goose "Poopers." One day, when no one else was home, Poopers and Dad took a little trip to a distant lake. Only Dad returned. Phoebe was heartbroken.

The following spring, a pair of honking Canada geese once again flew overhead. But this time, only the female landed in our little pond. Phoebe went running to the pond when she heard that familiar honking, yelling "Peepers! Peepers!" Peepers had come back to say hello to Phoebe! How did I know it was Peepers? I didn't. But somehow, Phoebe did. She stood on the pond bank for quite some time talking to the majestic goose; and the goose, standing on the bank beside her, talked back to her. They carried on a conversation that is rarely witnessed. Finally, Peepers flew off, and this time, Phoebe was happy.

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