WASTEWATER TREATMENT WITH CONSTRUCTED WETLAND
The EcoCenter is the first and one of only two buildings in City that treats its own wastewater. Going beyond conventional treatment, the processes at the EcoCenter involve irradiation of effluent and incorporation of a constructed wetland for further purification.
Primary Treatment: In the primary treatment stage, wastewater flows through a 1,000-gallon settling tank where solids sink to the bottom and oily substances float to the surface. The remaining liquid, referred to as effluent, flows by gravity into a second large tank. In addition to the settling and removal of most solid matter, naturally occurring microbes begin anaerobic (i.e., in the absence of oxygen) breakdown and consumption of inorganic and organic matter. Inorganic matter includes nutrients such as phosphorus and nitrogen compounds found in urine. Organic matter refers to human and food waste, soaps, and detergents.
Secondary Treatment: Effluent flows by gravity from the settling tank into a 1,500-gallon recirculation tank. During secondary treatment, organic matter is aerobically (i.e., in the presence of oxygen) digested by naturally occurring microbes. Every twenty minutes, effluent is recirculated through the tank past textiles loaded with the microbes. Removal of most of the organic matter takes place during this treatment phase.
Tertiary Treatment: Before leaving the recirculation tank, effluent passes through an ultraviolet (UV) light that kills most remaining viruses and bacteria.
Constructed Wetland: Constructed wetlands are man-made systems that mimic the cleansing functions of naturally occurring wetlands. At the EcoCenter, the constructed wetland consists of multiple pond-like enclosures that serve to further purify the effluent. Additional settling of solids takes place and inorganic and organic matter are consumed and sequestered by the microbes, algae, plants, invertebrates and vertebrates living in the system.
Subsurface Dispersal to Drainfield with Native Vegetation: Effluent ultimately leaves the EcoCenter via a subsurface irrigation system to a 2,000-square foot area surrounded by fencing in front of the building. This drainfield provides an absorption zone for the effluent that helps sustain the plants in the “Butterfly Meadow” (i.e., it contains plants that adult butterflies feed on or that their caterpillars like to eat).