Reclamation and reuse of water in the Triangle School Wastewater Treatment System (photo of actual treatment site, left) begins with the creation of nutrient rich water within the showers, sinks, and toilets inside the building. This so-called wastewater is piped to and collected in a 2000 gallon septic tank.
After settling, the uppermost water flows through an in-line filter into a 1500 gallon tank where it is pumped into the constructed wetlands (cells 1 and 2) via a series of distribution lines. Cell 1 receives most of the initial wastewater dose. A small portion is distributed to Cell 2 to provide a balance of nutrients for the microbes which enhances the change of liquid nitrogen to a gas.
Cell 1 is a combination sand filter and subsurface wetland which mimics a set of sand dunes surrounding a marsh (i.e. hills and swales). Water flows vertically through the three sand filters and then horizontally below the surface of the wetland. The sand filter remains aerobic by controlled 6-8 hour wastewater dosing intervals . As water flows vertically through sand and plant roots, potential pollutants are filtered, transformed, or stored.
Cell 2 is designed to flood and drain in a similar manner as a tidal marsh. The flooding and draining cycles are controlled by a solar powered mechanical valve installed within the outlet drain of the cell. Both the depth and time of flooding can be controlled to influence the flow of nitrogen and phosphorus.
The water draining from Cell 2 is divided into adjustable proportions controlled with a splitter valve. For example, a portion may be recirculated back to the septic tank to enhance nitrogen transformations and the remainder disinfected by UV light prior to distribution into the greenhouse.
The partially cleansed water is further filtered within the soil and plant roots of the greenhouse planter boxes. The planter boxes are designed to store or transform the small concentrations of nutrients left within the water.
Chlorine is added to water leaving the greenhouse as a final disinfection stage. The reclaimed water is now ready for reuse to flush toilets, irrigate the landscape, or to fill an aesthetic pool.
Water exiting all components of the system will be analyzed monthly for microbiological and chemical content.
Schematic and text reference: House, C. H., B. A. Bergmann, A. M. Stomp, and D. J. Frederick. 1996.