AWWA REUSE52132

A long-range water supply plan was prepared for the Tarrant Regional Water District of Tarrant County, Texas, in 1990. The Plan concluded that the primary approach to obtaining required additional water was to divert water from the Trinity River, which is largely treated wastewater return flows, into two of the District's four water supply reservoirs to provide a supplemental yield of 115,500 acre-feet/year. The District's plan to supplement its water supply with reclaimed water involves a multiple barrier approach that includes: advanced wastewater treatment; retention in the Trinity River; treatment in a constructed wetland system; dilution (maximum of 30 percent of reservoir capacity during drought conditions); and, water treatment. Data regarding treatment efficiencies for human pathogens from the pilot-scale constructed wetland facility and the proposed field-scale constructed wetland facility will be utilized to determine potential changes in treatment requirements and/or the required dilution rate. A constructed wetland was one of three potential alternatives selected for further investigation to remove nutrients and potential toxins from the diverted water. The other alternatives were chemical precipitation and a fish-periphyton study. Treatment is needed since the Trinity River at the point of diversion is dominated by highly treated wastewater flows from the Fort Worth-Dallas metroplex area, with variable flows contributed by surface reservoir releases, groundwater, rainfall, and storm runoff from both urban and rural areas. The point of diversion is approximately 60 miles downstream of the Fort Worth-Dallas metroplex. Treatment to control nutrient and potential toxicant inputs to the reservoirs is necessary to protect the water quality of the drinking water supply reservoirs. The District formulated a staged program to perform research to examine the financial aspects, operation and maintenance issues, and treatment performance of the constructed wetlands. The staged program involved initially constructing, operating, and testing of a pilot-scale constructed wetlands. Subsequent to gaining required information from the pilot-scale wetlands, a field-scale wetlands will be constructed to perform further research regarding the treatment expectations of the wetlands. This paper discusses the results of the pilot-scale constructed wetlands program. Includes tables, figure.