TEXAS POTABLE WATER SUPPLY: WETLAND WATER REUSE PROJECT

In order to meet future water supply requirements, Tarrant Regional Water District is pursuing several options including diverting Trinity River water into two of the District's reservoirs located downstream of the Dallas-Fort Worth Metroplex. The District's approach to augment the water supply with reclaimed water involves a multiple-barrier approach including advanced wastewater treatment, retention in the Trinity River, treatment through a constructed wetland system, dilution (maximum of 30 percent of reservoir capacity during drought conditions), retention in the reservoir, and potable water treatment. Data regarding treatment efficiencies from a pilot-scale constructed wetland facility operated from 1992 through 2000 and continuing research at a recently completed field-scale constructed wetland facility will be utilized to determine potential changes in treatment requirements and/or the required dilution rate. The field-scale constructed wetland project has involved a working partnership between the District and the Texas Parks and Wildlife Department (TPWD). The 243-acre field-scale project is constructed on TPWD property under a Memorandum of Understanding between the District and TPWD. Several operation and management issues are being evaluated at the field-scale level in order to adequately quantify impacts. Also, the effectiveness of flow distribution designs (including deep water channels for distribution of inflows and collections of outflows, vegetative baffles, shallow shoals, and deep water zones) and shallow filtering zones immediately above the outflow of the final wetland cell will be determined in the field-scale unit prior to final design of the full-scale system. Applying constructed wetlands for providing additional treatment prior to discharging the reclaimed water into existing water supply reservoirs has proven to be effective in meeting treatment objectives based on more than eight years of performance testing data at a pilot-scale facility and during the initial operation of the field-scale system. The District is continuing its research effort to further examine various performance, operation, and maintenance issues that would be associated with the use of constructed wetlands on a full-scale basis. The District's efforts to incorporate a multiple barrier approach will ensure that water provided to its customers is not only a dependable but also a safe supply.