Submitted to: Water Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 1, 1998
Publication Date: N/A
Interpretive Summary: Agricultural chemical applicators include farmers, custom applicators, and commercial dealerships. Each of these groups generates pesticide contaminated waste water, including leftover solutions in the spray tank and rinse waters. This project was conducted to examine the feasibility of developing a bioreactor to decontaminate these waters. In order to accommodate the variations in rinse water volume and pesticide concentration, the bioreactor was designed to utilize biofilms containing the atrazine-degrading bacterium, Agrobacterium radiobacter strain J14a. Stable biofilms were formed by bacterial growth on porous plastic supports within the bioreactor. The use of biofilms has the advantage of retaining bacteria within the bioreactor, thus reinoculation of bacteria is not required. High concentrations of atrazine, a widely used corn herbicide, were degraded within 12 hours when the waste water was augmented with an additional carbon source for the bacteria. This model system was capable of degrading atrazine at concentrations that would result from commercial herbicide applications. Additional research will be required to develop bioreactors with the mixed population biofilms necessary to degrade the diverse array of pesticidal compounds found in applicator waste waters.
A sequencing batch biofilm reactor (SBBR) was developed to treat dilute formulated rinsate of atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine] from an agricultural chemical formulation facility. The SBBR was inoculated with Agrobacterium radiobacter strain J14a. Hydraulic residence times (HRTs) and different carbon sources were varied to determine their effects on the rate of degradation of atrazine and chemical oxygen demand (COD) by the biomass. The degradation rate of atrazine by J14a was enhanced when a supplemental carbon source was added. An initial concentration of 30 mg/L of atrazine with citrate and sucrose as carbon sources was degraded to less than 1 mg/L within 12 hours for a 2-day hydraulic residence time at room temperature of 22 deg C. The first order rate constant for atrazine was approximately 0.44 +/- 0.03 hr**-1. For an HRT of 7 days, more than 90% of fatrazine was found to degrade within 45 hours.