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AN INNOVATIVE SYSTEM FOR BIOREMEDIATION OF AGRICULTURAL CHEMICALS FOR ENVIRONMENTAL SUSTAINABILITY
Impact/Purpose:
The overall objective of this Phase II research project is to design, implement, and evaluate a renewable, naturally available biofilter to minimize the transport of chemicals from agricultural fields into surface water sources. The specific objectives of this project are to (1) implement a field-scale biofilter based on results from Phase I and evaluate its effectiveness, (2) continue evaluating the efficiency of materials for bioremediation of aqueous contaminants, (3) investigate how retention time affects bioremediation of aqueous contaminants, and (4) based on results from objective (3), provide recommendations to implement biofilter technology to reduce contaminant discharge from agricultural areas as well as septic systems and wastewater treatment facilities.
Description:
Agricultural chemicals (both inorganic and organic) in drainage discharge from watersheds have raised concerns about the quality of surface water resources. For example, hypoxia in the Gulf of Mexico has been related to the nutrients discharging from agricultural watersheds in the Mississippi River Valley. Finding an efficient and cost effective solution to the nutrient problem is of utmost importance. Experiments were conducted during September 2006 – April 2007 at the University of Illinois to determine the efficiency of various biomaterials for removing agricultural chemicals from drainage discharge. Soil columns were used to investigate the chemical reduction in water when it passes through biological filters; beaker experiments were conducted to investigate if biological activities would enhance chemical reduction. The results from both the soil column and beaker experiments support the hypothesis that a properly designed, naturally available biofilter can significantly reduce the amount of chemicals leaving agricultural fields. It has been determined that hardwoods (in general), cocoa bean shells, and granular activated carbon materials perform exceptionally well for the reduction of nitrate, atrazine, and alachlor. Granular activated carbon was expected to perform well, being a component of many conventional drinking water filtration systems. What was unexpected was the discovery that biomaterials such as hardwood chips and cocoa bean shells can perform as well, or better than, granular activated carbon, which could revolutionize water treatment technologies. From the soil column experiments, it also was determined that retention time does have a positive effect on the amount of nitrate that can be reduced by various filter media. Therefore, a material with a porosity that optimizes filtration rate and nitrate reduction ultimately will be the most useful material for this sort of application. Furthermore, the benefit of extended retention time could promote the implementation of conservation practices such as controlled drainage in tile-drained watersheds.
The beaker experiments proved that biological activity is at least partially responsible for nitrate reduction. The possibility of other factors (soil organic matter, moisture content, etc.) contributing to nitrate reduction cannot be ruled out at this point, but it is clear that there is some biological degradation occurring. This was discovered when the materials that were re-inoculated with indigenous soil bacteria showed a much greater reduction in nitrate than the materials that had been sterilized of all microorganisms.
Additionally, the beaker experiments confirmed the findings of Davidson (2005), showing that nitrate is significantly reduced in the presence of atrazine and alachlor. This finding could have serious implications for agricultural producers, considering that atrazine and alachlor could potentially render fertilizers useless if applied in close time proximity of these pesticides.