Margaret J. Kupferle

Transport and biodegradation of toxic organics in biofilms

Abstract This paper summarizes our studies on transport and biodegradation of azo dyes in aerobic biofilms. Three lab-scale rotating drum biofilm reactors (RDBRs) were used to culture the biofilms. synthetic, municipal-type wastewater, spiked with several azo dyes, was continuously fed into the RDBRs. The study has revealed that Acid Orange 7 (AO7) and Acid Orange 8 (AO8) can be degraded aerobically in an efficient and effective manner under properly controlled operating conditions. The other dyes tested, however, are essentially non-degradable in an aerobic reactor. Microelectrodes and a microslicing technique have been used to elucidate changes in the structure of biofilms with depth and to determine the influence of these changes on mass transport and transformation processes. The results show that biofilms are non-homogeneous and highly stratified. Accordingly, biofilm is usually characterized by aerobic and anaerobic zones, with the anaerobic part used to break the azo bond and the aerobic surface layer to achieve the mineralization of anaerobically recalcitrant intermediates. Results concerning the inhibition effect of azo dyes on biofilm COD removal and respiration rate are also presented in this paper.

Anaerobic DDT biotransformation: Enhancement by application of surfactants and low oxidation reduction potential

Enhancement of anaerobic DDT (1,1,1-trichloro-2,2-bis(p-chlorophenyl) ethane) biotransformation by mixed cultures was studied with application of surfactants and oxidation reduction potential reducing agents. Without amendments, DDT transformation resulted mainly in the production of DDD (1,1-dichloro-2,2-bis(p-chlorophenyl) ethane) upon removal of one aliphatic chlorine. The DDT transformation rate increased with the addition of the nonionic surfactants Triton X-114 or Brij 35. The addition of either surfactant or reducing agents did not significantly extend the DDT transformation. Addition of both surfactant and reducing agents extended DDT transformation by reducing the accumulation of DDD and increasing the accumulation of less chlorinated products. It is important to minimize the accumulation of DDD because it is a regulated pesticide and is recalcitrant to aerobic transformation. Controlled experiments revealed that the transformation of DDT requires microbial culture, but the culture need not be biologically active. Transformation results are presented for aqueous and soil phase contamination.

Treatment Technology Evaluation for Aqueous Metal and Cyanide Bearing Hazardous Wastes (F007)

As a result of recent developments In the area of hazardous waste management, the U.S. Environmental Protection Agency Is evaluating the performance of various technologies for the treatment and/or the destruction of certain wastes that are presently being disposed of In landfills and surface Impoundments. As a part of this program, the University of Cincinnati Is testing currently available treatment technologies that are applicable to metal- and cyanidebearing hazardous wastes at the U.S. EPA Test and Evaluation Facility In Cincinnati, Ohio. The following unit processes have been evaluated: alkaline chlorlnatlon, lime precipitation/ flocculation/settllng, multi-media filtration, anlon exchange, and cation exchange. Examination of several process configurations, utilizing the above-mentioned unit processes, did not produce any treatment train that could prevent codepositlon of cyanides and metals In the sludges when the feed stream contained mixed metals and complexed cyanides. It was also determined tha...

Identification of chlorinated oligomers formed during anodic oxidation of phenol in the presence of chloride.

Chlorinated oligomer intermediates formed during the anodic electrochemical oxidation of phenol with a boron-doped diamond electrode were studied at two different concentrations of chloride (5mM and 50mM). Under the same ionic strength, with sodium sulfate being the make-up ion, a 10-fold increase in Cl(-) led to removal rates 10.8, 1.5, and 1.4 times higher for phenol, TOC, and COD, respectively. Mono-, di- and trichlorophenols resulting from electrophilic substitution were the identified by-products. Nevertheless, discrepancies between theoretical and measured TOC values along with gaps in the mass balance of chlorine-containing species indicated the formation of unaccounted-for chlorinated by-products. Accurate mass measurements by liquid chromatography quadrupole time-of-flight mass spectrometry and MS-MS fragmentation spectra showed that additional compounds formed were dimers and trimers of phenol with structures similar to triclosan and polychlorinated dibenzo-p-dioxins.

Elucidating the role of phenolic compounds in the effectiveness of DOM adsorption on novel tailored activated carbon.

Two novel tailored activated carbons (BC-41-OG and BC-41-MnN) with favorable physicochemical characteristics were successfully prepared for adsorption of dissolved natural organic matter (DOM) by applying systematically chemical and thermal treatment. This research was conducted to investigate the impact of the presence of phenolics on the adsorption capacity of DOM. Isotherm tests were performed for both humic acid (HA) and phenolics on both novel tailored activated carbons and commercial activated carbon F400. The presence of phenolics display a significant effect on hindering the adsorption of HA, however; the physicochemical characteristics of novel activated carbons (surface metal oxides and mesoporosity) can play an important role in alleviating this effect. In contrast, F400, with a relatively lower mesoporosity and surface basicity as compared to the developed adsorbents, was severely impacted by the oligomerization of phenolic compounds. The adsorption capacity of DOM in presence of phenolics was further studied in a continuous flow microcolumn system. The column results showed that both BC-41-OG and BC-41-MnN have not only higher HA adsorption capacity but also better selective adsorption ability than F400.

Comparing the solid phase and saline extract Microtox® assays for two polycyclic aromatic hydrocarbon‐contaminated soils

The performance of remedial treatments is typically evaluated by measuring the concentration of specific chemicals. By adding toxicity bioassays to treatment evaluations, a fuller understanding of treatment performance is obtained. The solid phase Microtox assay is a useful tool in characterizing the toxicity of contaminated soils and sediments. This study compares the performance of the solid phase and saline extract Microtox assays in two experiments using two soils contaminated with polycyclic aromatic hydrocarbons (PAHs). The first experiment, conducted to refine the solid phase assay procedures, evaluated sample holding times, sample replication, and reference toxicant controls. The effective concentration reducing light emission by 50% (EC50) of four samples was measured with eight replicates of each sample. Samples were stored for as long as two weeks without showing substantial changes in toxicity. For future studies, three replicates of each sample are recommended because that degree of replication yielded a statistical power of more than 95% in most samples. Phenol was a reliable reference toxicant with a mean EC50 of 21.76 and a 95% confidence interval of 15.6 to 27.9 mg/L. In a second experiment, the solid phase Microtox assay was compared to saline extract Microtox assays with mixing times ranging from 5 min to 16 h. The solid phase assay was more sensitive yielding EC50s 7 to 50 times lower than the extract EC50s. In addition, the saline extract assays displayed results that varied for mixing times of less than 2 h. Based on these two experiments, the solid phase Microtox test has proved to be a useful assay for measuring the toxicity of PAH-contaminated soils.

Using toxicity testing to evaluate electrochemical reactor operations

In the present study, the Microtox® test was used to track the toxicity of electrochemical effluents to the marine bacteria Vibrio fischeri as a function of reaction time. When electrochemistry was used to degrade aqueous phenol using different reactor configurations, two reaction pathways were identified, chlorine substitution and oxidation, depending on whether the electrolyte contained chloride. For a boron-doped diamond (BDD) anode, electrochemistry using Na₂SO₄ electrolyte produced a significantly more toxic effluent than when using NaCl electrolyte with all other conditions remaining the same. This effect is attributed to the reaction pathway, specifically the production of benzoquinone. Benzoquinone was produced only during electrochemistry using Na₂SO₄ and is the most toxic potential intermediate, having nearly 800 times more toxicity than phenol. Although the use of NaCl produced a lower toxicity effluent than Na₂SO₄, caution should be observed because of the production of chlorinated phenols, which can be of special environmental concern. When comparing graphite rod and BDD plate anodes in terms of toxicity evolution when using Na₂SO₄, BDD was found to produce a lower toxicity effluent; this is a result of the increased oxidizing power of BDD, reducing the formation of benzoquinone. In this comparison, the type of anode material/electrode configuration did not seem to affect which intermediates were detected but did affect the quantity of and rate of production of intermediates.

Anaerobic pretreatment of hazardous waste leachates in publicly owned treatment works

Feasibility studies have been completed for an anaerobic pretreatment system designed to treat hazardous waste leachates in publicly owned treatment works. The system was designed to mitigate many of the problems associated with conventional aerobic treatment of these wastes and other types of dilute waterborne hazardous wastes. In this new approach, a contact/sorption stage consisting of an expanded bed of granular activated carbon (GAC) with an attached anaerobic biomass was used as a pretreatment device after primary clarification before the aerobic treatment portion of the plant. This sorption stage was intended to reduce pass-through of toxics, retaining them for subsequent treatment in a separate anaerobic stabilization reactor. The organic-rich GAC/biomass bed from the sorption stage was exchanged with stabilized GAC/biomass from the anaerobic stabilization stage, conserving the GAC in the system. Two 87-L/d bench-scale systems were operated for 332 days, one treating unspiked primary effluent and one treating primary effluent spiked with 5% landfill leachate and 14 hazardous organic compounds. In the spiked system, removals in the sorption stage were the highest for the aromatic compounds. Five ofthe six aromatics added were removed at over 95% and the sixth, phenol, had an 85% removal. Removals of chlorinated aliphatic compounds ranged from 52% for methylene chloride to 95% for trichloroethylene. Removals of phthalate compounds were approximately 60%. Removals of ketones ranged from 24% for acetone to 93% for methyl isobutyl ketone. Chemical oxygen demand removals remained at 40% to 50% throughout the year-long study in both systems.

Development, validation and application of an HPLC method for phenol electrooxidation products in the presence of chloride

A high-performance liquid chromatography (HPLC) method was developed and validated to determine phenol and potential intermediates from hydroxylation (hydroquinone, benzoquinone, catechol) and hypochlorination (2-chlorophenol, 3-chlorophenol, 4-chlorophenol, 2,4-dichlorophenol, 2,6-dichlorophenol, 2,3,6-trichlorophenol, 2,4,5-trichlorophenol, 2,4,6-trichlorophenol and pentachlorophenol) pathways during electrooxidation in the presence of chloride. A Hypersil ODS column (150 mm L × 4.6 mm I.D.) was used for the separation. The best separation was achieved when using a time variant gradient between a water mobile phase (with 0.1% formic acid adjusted to pH 3.0 with 0.1 mM sulfuric acid) and an organic phase (90:5:5 by volume mixture of acetonitrile:methanol:acetic acid). The flow rate was 0.8 mL min−1 and UV absorbance was monitored at 270, 280, 290 and 300 nm, choosing the wavelength of strongest response for each compound. The intra- and inter-day accuracy and precision were tested using five replicates each day on three consecutive days.

A MARKOV MODEL TO ESTIMATE SALMONELLA MORBIDITY, MORTALITY, ILLNESS DURATION, AND COST

Approximately 690000-1790000 Salmonella cases, 20000 hospitalizations, and 400 deaths occur in the USA annually, costing approximately