Grantee Research Project Results
Final Report: Evaluating Reactive Barrier Technology to Enhance Microbially -Mediated Denitrification during Managed Aquifer Recharge
EPA Grant Number: SU835995Title: Evaluating Reactive Barrier Technology to Enhance Microbially -Mediated Denitrification during Managed Aquifer Recharge
Investigators: Fisher, Andrew T
Institution: University of California - Santa Cruz
EPA Project Officer: Page, Angela
Phase: I
Project Period: September 1, 2015 through August 31, 2016
Project Amount: $14,972
RFA: P3 Awards: A National Student Design Competition for Sustainability Focusing on People, Prosperity and the Planet (2015) RFA Text | Recipients Lists
Research Category: P3 Awards , Pollution Prevention/Sustainable Development , Sustainable and Healthy Communities , P3 Challenge Area - Safe and Sustainable Water Resources
Objective:
Our research seeks to improve water quality and supply through rapid contaminant removal during managed aquifer recharge ("MAR," increased flows of freshwater into an aquifer). This project focuses on a field site in the Central Coastal region of California, where we and our partners have introduced a novel incentive program to encourage innovative groundwater management. In this region, groundwater supplies 85% of freshwater demand, and years of
excess pumping, compounded by changes in land use and climate, have resulted in significant depletion and harm to aquatic systems. As groundwater quantities decrease, groundwater quality faces challenges as well, particularly from the widespread use of nitrogen fertilizers for agricultural production. Nitrogen, in the form of nitrate (NO3-), is one of the most common and persistent groundwater pollutants, and elevated nitrate can be harmful to human and aquatic systems.
We conducted a series of field experiments to investigate the links between MAR and water quality improvements. Previous studies have suggested that, under some conditions, nitrate can be removed from infiltrating water as it passes through shallow soils. It is not well understood what factors control the rate and extent of water quality improvements. If processes controlling the improvement can be understood, we should be able to design and run groundwater recharge systems to do a better job at removing nitrate and other contaminants.
Summary/Accomplishments (Outputs/Outcomes):
We conducted a series of field infiltration experiments (with associated laboratory analyses of sediment, water, and microbial materials) to determine the relationships between water infiltration, nutrient concentrations, the nature of soils, and microbial ecology. Our results focus on the comparison of two kinds of infiltration systems: one using native soil, and the other using native soil and a permeable reactive barrier (PRB) made of wood chips. Our hypothesis is that the PRB may provide habitat or materials needed by microbes living in the soil that will stimulate them to grow and consume more contaminants in infiltrating water, as it flows from the ground into an underlying aquifer. We ran four field tests, each lasting 2 weeks. Each test was conducted using many kinds of instrumentation to allow measurement of infiltration and sampling of fluids during the tests. Instruments allowed us to measure the total infiltration rate with time, and how much of the infiltration moved vertically (rather than horizontally) through the soil. We also sampled water at multiple depths, so that we could track how its chemistry changed over time. We sampled soils and microbes living in the soil below the plots, both before and after each test. The infiltration rates measured during the four tests varied somewhat site to site, due to differences in sediment properties, but were generally on the order of 10 to 60 ft/day (very fast). As a result, we were not sure if we would see much change in water chemistry because earlier studies suggested that removal of nitrate tends to slow or stop at infiltration rates above about 2-3 ft/day. However, we found measurable removal of nitrate in soil below the PRB, and also found that the population of microbes living in the soil changed considerably when comparing conditions before and after the tests. This supports our hypothesis of the links between the infiltration rate, soil composition, microbiology and nitrate removal. The outputs of this work are the technical results described above, along with the presentations made to public and technical groups, and the professional skills and experience gained by student participants. The most important outcome of this work is linking improvements to water supply to improvements in water quality, so that the latter can be put
front and center as the basis for developing regional projects to sustain water supplies and aquatic systems. As described below for proposed Phase 2 work, we have had success in linking water quality to regional efforts to improve water supply, and now this study site can serve as a template for other parts of the state where significant changes to groundwater management are occurring.
Conclusions:
Phase 1 studies by our team have: (a) demonstrated development and use of a unique, flexible, and robust field testing system for infiltration; (b) confirmed and expanded the relationship between soil composition, rates of infiltration, and rates of nutrient removal; (c) developed sound sampling procedures to recover high quality fluid and sediment for linked geochemical and microbiological analyses during infiltration; and (d) shown a substantial shift in microbial ecology in association with infiltration and nitrate removal. Given the high infiltration rates that we observed during Phase 1, the fact that we see any measurable removal of nitrate during infiltration is encouraging. The removal of nitrate at depth, along with the appearance of other compounds consistent with microbial improvement to water quality, suggests that these test systems are poised for much greater improvement, if we can slow the water somewhat to allow more complete nutrient cycling. These are positive and exciting results, and will form the basis for additional presentations, papers, and thesis chapters. More importantly, these results move us towards wide-scale implementation of techniques to improve groundwater quality during infiltration of stormwater water as part of managed recharge activities. We will take the next steps in Phase 2 of this project, with development of a field-scale project that integrates Phase 1 results.
Journal Articles on this Report : 1 Displayed | Download in RIS Format
Other project views: | All 1 publications | 1 publications in selected types | All 1 journal articles |
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Type | Citation | ||
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Beganskas S, Gorski G, Weathers T, Fisher A, ShmiDust C, Saltikov C, Redford K, Stoneburner B, Harmon R, Weir W. CM-200819-4097863 A horizontal permeable reactive barrier stimulates nitrate removal and shifts microbial ecology during rapid infiltration for managed recharge. WATER RESEARCH 2018;144:274-284. |
SU835995 (Final) |
Exit Exit |
Supplemental Keywords:
Groundwater, hydrology, geochemistry, microbiology, measurement methods, interdisciplinary, soil, genomics, nitrate, denitrification, nutrient management, load reduction, reduction and elimination of water pollution, research to ensure provision of a dependable safe supply of drinking water, protection of underground water sourcesRelevant Websites:
Newspaper stories:
San Jose Mercury News:
Groundwater law, winter rain trigger flood of aquifer-recharge experiments around California Exit
Santa Cruz Sentinel:
Drought: Aquifer woes here to stay Exit
Contra Costa Times:
California groundwater law, winter rain trigger flood of aquifer-recharge experiments around the state Exit
The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.