Selection and Testing of Tracers for Measuring Travel Times in Groundwater Aquifers Augmented with Reclaimed Water
Project: 05-07
Product: Report
Year: 2009
Program: Principal
Funding Partner: Bureau of Reclamation, Town of Gilbert, Fountain Hills Sanitation District
Total Investment: $120,000 (Cash)
Principal Investigator: Wontae Lee, Ph.D., P.E., HDR Engineering, Inc.
Background
Augmentation of the groundwater aquifer with reclaimed water has the potential to cause public health and environmental concerns. Tracking the migration of contaminants, pathogens, and disinfection by-products in groundwater aquifers is crucial in assessing potential health/environmental impacts, preventing pollution problems, and designing/constructing cost-effective remediation systems. Information and method of testing and analysis to determine the travel time of biophysicochemical constituents of reclaimed water in aquifers is useful for the design and permitting of reclaimed water aquifer recharge projects.
Goals and Objectives
The project identifies, selects, and tests environmentally acceptable tracers for measuring travel times of reclaimed water and its constituents in recharge systems. The secondary objective was to develop a protocol for conducting tracer tests on recharge systems that are augmented with reclaimed water.
Research Approach
The project included the following major activities: 1) compare and select tracers for recharge systems augmented with reclaimed water, 2) evaluate the performance of tracers in three common recharge systems (recharge basin, vadose zone recharge well, and direct recharge well), and 3) develop a protocol for conducting tracer tests in recharge systems. The tracers used included two non-reactive tracers (bromide and sulfur hexafluoride), two microbial tracers (PRD1 and MS2), and one reactive organic compound (caffeine). Each tracer was injected via a recharge basin, a direct recharge well, and a vadose zone recharge well.
Findings and Conclusions
This research report provides a summary of the literature related to conservative and surrogate tracers for reclaimed water constituent transport in the subsurface, the materials and methods used for evaluation of tracers, the results from tracer experiments on three common recharge systems augmented with reclaimed water, and information on the process for regulatory approval of the use of tracers for reclaimed water recharge systems and of field methods for conducting tracer tests.
The research results can be used to select tracers for recharge systems augmented with reclaimed water. The tracers tested during this project include typical conservative tracers (bromide and sulfur hexafluoride) as well as environmentally acceptable microbial tracers (PRD1 and MS2), and one organic compound (caffeine). This project developed protocols/methodologies for conducting tracer tests at recharge systems (recharge basin, vadose zone recharge well, and direct recharge well) augmented with reclaimed water and provide information on the regulatory approvals needed.
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