Treatment Effect of Graywater through a Tandem Wetland

The conventional wastewater management practice is to collect all indoor used water into a single pipe leading to the sewer and treat it at the wastewater treatment plant. Mounting pressure to conserve water supplies, however, has lead to the suggestion that the separation of graywater and blackwater through the use of a dual plumbed system may enable graywater to be reused as a source of water for non-potable uses in urban areas. An added benefit of graywater reuse is wastewater volumes will be reduced by nearly 50%, resulting in substantial savings for wastewater treatment. Reuse of household graywater for residential landscape irritation is already a common practice in several western states, but there is potential in many situations for graywater reuse, especially from commercial entities for augmentation of urban water resources and irrigation. At Colorado State University the Atmospheric Sciences Laboratory Building was dual plumed during construction to provide separate wastewater collector systems for graywater and blackwater. A principle of graywater management is that it will be treated to acceptable levels for discharge into the surface water drainage system where it will eventually be used to supplement irrigation demands. Treatment using a graywater wetland is hypothesized to be a cost-effective and aesthetic way to condition the water for reuse. This paper provides an example of a useful way to condition graywater for non-potable reuse using wetland system. The discharge water of the Atmospheric Science Building is conditioned in a tandem wetland system compose of Free Water Surface (FWS) wetland followed by a Vegetated Submerged Bed (VSB) wetland. To find the treatment efficiency of this system, three points have been measured: the inflow of the FWS wetland, the center between the FWS wetland and VSB wetland, and the outflow of the VSB. The parameters considered of this wetland project are water flow rate (Q), Biological Oxygen Demand (BOD), Chemical Oxygen Demand (COD), Suspended Solids (SS), Total Nitrogen and Total Phosphorous (T-N, T-P). From the resulting wetland treatment of this study, we will be able to determine the treatment efficiency of the two types of wetlands (the FWS and the VSB), and show feasible ways to treat graywater for non-portable usage.