Kyoung S. Ro

Fate and enhancement of atrazine biotransformation in anaerobic wetland sediment

Abstract We examined fate and anaerobic microbial transformation/degradation characteristics of atrazine in wetland sediment receiving wastewater from a local sugar mill. Well-known metabolites/intermediates of atrazine were not detected except hydroxyatrazine. Atrazine adsorbed on the sediment linearly with a distribution coefficient of 9.979 ml/g. Although we did not obtain a direct proof of atrazine mineralization, the values of observed yield of total NH3-N were comparable to the theoretical values suggesting the biodegradation of atrazine to its end products of NH3 and CO2. Only about 20% of atrazine was biotransformed to non-triazine species, possibly to the mineral end products, after 38 weeks of incubation in the sample reactors without organic amendments, with methanol and sodium acetate. Acetic acid appeared to enhance the biotransformation of atrazine (both in aqueous and sediment phases) if one only measured the parent atrazine compound alone. However, a comprehensive analysis of atrazine and its metabolites/intermediates showed that most of the disappeared atrazine existed as hydroxyatrazine. Glucose improved the wetland sediments removal rate of the triazine species.

Atrazine biotransformation in wetland sediment under different nutrient conditions‐i: Anaerobic

Abstract Anaerobic biotransformation of atrazine under three different nutrient conditions, i.e., D.I water, wetland water, and basal salt media (BSM), was investigated with the sediment from a wetland receiving sugar mill wastewa‐ter in Louisiana. None of the well‐known metabolites and their hydroxy analogs, except hydroxyatrazine were detected in all sample reactors. About 50% of 10 mg/L of atrazine disappeared after 38 weeks of incubation from liquid and sediment phases of the sample reactors with D.I. water and wetland water. However, more than 25% of the disappeared atrazine still existed as hydroxyatrazine in those sample reactors. BSM substantially increased the removal rate of atrazine. Atrazine concentrations dropped to less than detectable level after 38 weeks of incubation in the sample reactors with BSM. However, the hydroxyatrazine level in liquid and sediment phases of the BSM reactors was still about 2.5 mg/L. BSM without (NH4)2SO4 decreased the atrazine transformation rate.

Diffusive transport of 2,4,6-trinitrotoluene (TNT) from contaminated soil to overlying water

Understanding the transport mechanism of 2,4,6-trinitrotoluene (TNT) and other compounds is necessary in order to implement an effective phyto- or bioremediation scheme for explosives-contaminated soil. The transport of TNT from two contaminated soils into overlying water was investigated using a laboratory sheet-flow leaching bed reactor (SLBR). Soil I had a low contamination of TNT (11±1 mg kg−1), whereas Soil II had very high contamination of TNT (22 874±518 mg kg−1). The results showed a decrease in aqueous effluent TNT concentration and flux with time in both cases indicating the diffusive nature of the process (t−1/2 dependance). The flux from the sediment to the water column was used to obtain the effective diffusivity of TNT by fitting the data on Soil I to a mathematical model. The average effective diffusivity value obtained was 1.18×10−6±8.32×10−7 cm2 s−1. This suggests slow diffusive transport of TNT through the soil. The initial flux from Soil II was approximately 50 times higher than from Soil I. The final steady state flux was larger than that from Soil I since the initial porewater TNT concentration was much higher for Soil II. From our experiments, we calculated that the characteristic time for transport is estimated to be ca. 7 years whereas the first order degradation rate by plant enzymes is ca. 70 min. The slow transport of TNT from the soil bed will be a limiting factor in the phyto- or bioremediation of explosives-contaminated soils.

Demonstration of bioaugmentation in a fluidized-bed process treating 1-naphthylamine

Abstract The feasibility of using a fluidized-bed reactor with bioaugmentation to treat low-strength wastewater or slightly contaminated groundwater was evaluated. Tap water spiked with 1.6 to 12.6 mg/L of 1-naphthylamine was treated in a fluidized-bed reactor with a hydraulic retention time of 6.2 to 13.3 h. With conventional operation, the reactor was unable to maintain consistent removal because of cell washout. Continuous removal efficiency was greater than 90% using bioaugmentation through periodic addition of acclimated cells from an off-line enricher-reactor. The concept demonstrated by this research presents an alternative for biological treatment of wastes (dilute wastewaters and contaminated groundwater) which are not normally considered good candidates for biological treatment.

Stormwater runoff quality of a louisiana log storage and handling facility

Abstract Very little attention has been paid to the stormwater runoff quality from log storage and handling facilities. This project determined the concentrations of conventional parameters such as BOD5, COD and TSS, and 123 priority pollutants of stormwater runoff samples from a log storage and handling facility in Louisiana. No significant levels of priority pollutants were found and only about 1 to 13 % of COD was biodegradable. COD followed closely with TSS, suggesting that effective control of TSS will control COD as well. The pollutant strength resulting from summer to fall storms did not vary much.

Chemical transformation of atrazine with sodium azide

Abstract We investigated the chemical transformation of atrazine with sodium azide. Sodium azide reduced the atrazine level in the control reactors at a rate much faster than the natural anaerobic biotransformation rate in wetland sediment. The chemical transformation of sodium azide with atrazine was observed in the D.I. water sample reactors. It was evident from the study that higher the sodium azide concentration, the faster the dissipation of atrazine. Atrazine disappeared faster in anaerobic conditions than aerobic conditions. Based on limited mass spectral analysis, 3‐ethylamino, 5‐isopropylamino‐s‐triazyl azide and 3‐ethylamino, 5‐isopropylamino‐s‐triazinone appeared to be the final transformation products from the chemical interactions between atrazine and sodium azide. This study clearly demonstrated that sodium azide must not be used to prepare control reactors in atrazine degradation studies.

Transport process of TNT from flooded highly contaminated surface soil bed

Abstract Remediation of TNT contaminated soil by phytoremediation and bioremediation in aqueous medium is often limited by TNT desorption from the soil. Understanding the desorption of TNT from the contaminated soil is needed in order to employ effective soil remediation strategies. TNT (2,4,6‐Trinitrotoluene) desorption was investigated using a flat sheet flow leaching bed reactor in the laboratory. Deionized water advective flow was pumped over the contaminated soil matrix in the form of a sheet flow. Concentrations of TNT in the collected water samples was determined by HPLC. The result is presented as the flux of TNT from the soil matrix to the water phase. The results showed a decrease in TNT concentration and flux with time. The rates of leaching were compared to the prediction of a simple mathematical model that was developed for this type of the reactors. The model accurately fits the rate of removal of TNT from soil under various experimental conditions. The effective diffusivity was calculated b...

Solid wastes research

Abstract This paper reviewed and analyzed results of recent research activities pertaining to characterization, treatment, and disposal methods of solid wastes. Although landfill gas emissions, liner materials minimizing pollutants emissions, leachate characterization, and treatment are actively studied, only few have studied the quantity, compositions, physicochemical and biological characteristics of landfilled solid wastes. Science and engineering of composting for solid wastes are under intense investigation by many researchers with generally two objectives: a) to convert biodegradable solid wastes into valuable, nutrient‐rich composts for various end‐use applications or b) to remediate soils or wastes contaminated with hazardous organic contaminants by composting (remediation composting). While the first has been already used in many areas at field scales to minimize solid waste problems, the latter is still in research stage. Once the remediation composting is proven for its efficacy, it will provid...

A proposal for a field‐scale pilot demonstration unit for bioremediation of tnt contaminated soil

Abstract A reasonable field‐scale operational scenario was developed as the hypothetical TNT bioremediation unit. II is described in Appendix A and termed the Riffle‐Pool Reactor. The two‐stage system consists of TNT leach‐bed followed by a plant‐pool bioreactor. Water is recirculated either continuously or intermittently over the riffle‐bed TNT extractor and into the plant‐pool reactor. A previously published manuscript entitled “Aquatic Plant Augmented TNT Degradation ‐ Analysis of Reactors Kinetics”; contains the kinetic parameter estimates needed to estimate equipment design and operating parameters. This include the Monod rate constant, dissolution constants and other kinetic parameters. This manuscript demonstrates how that basic information is incorporated into the design of the pilot, field‐scale demonstration unit.

Soil ‐ water partitioning and mass transfer kinetics of 2, 4, 6 trinitrotoluene in highly contaminated soil

Abstract The soil distribution coefficient for highly concentrated TNT soil is determined. Different amounts of TNT soil are shaked with 250 ml of distilled water, and the concentration of TNT in water is monitored throughout the experiment. At the conclusion of the experiment, the remainder of TNT in the soil is determined. The soil distribution coefficient is calculated by dividing the concentration of TNT in the soil by the concentration of TNT in the water phase. The average soil distribution coefficient is found to be 4.86 L/kg The mass transfer coefficient was determined under static conditions. This experiment involves a comprehensive study of distribution profiles for TNT in the soil and solvent phases. The experiment was conducted under a controlled temperature environment, for extensive periods of time. Samples were collected on a regular basis and were analyzed promptly. The average value of the mass transfer coefficient was determined to be 3.4×10‐3 hr‐1.