Laura W. Lackey

Pseudomonas putida B2: a tod-lux bioluminescent reporter for toluene and trichloroethylene co-metabolism.

A tod-lux transcriptional fusion bioluminescent reporter strain, Pseudomonas putida B2, was developed to permit on-line analysis of trichloroethylene (TCE) transformation by toluene dioxygenase (todC1C2BA) in Pseudomonas putida F1. Strain B2 was exposed to toluene in growing and resting cell bioluminescence assays. The growing cells showed a direct correlation between bioluminescence and toluene concentration, while resting cells showed reproducible bioluminescence with repeated toluene exposures. In addition, P. putida B2 was encapsulated in alginate beads and used in a packed bed flow-through differential volume reactor. The TCE feed into the differential volume reactor was constant at 20 mg L−1 and toluene was pulsed in square-wave perturbations at 10 mg L−1. The system showed a direct correlation between the expression of the tod operon (as monitored by light output) and the co-metabolism of TCE. Approximately 20% of the TCE and 50% of the toluene was removed at a flow rate of 0.4 ml min−1. This approach allowed the on-line monitoring of tod gene expression and its relation to TCE biotransformation.

Biodegradation of chlorinated aliphatic hydrocarbon mixtures in a single-pass packed-bed reactor

Aliphatic chlorinated compounds, such as trichloroethylene (TCE) and tetrachloroethylene (PCE), are major contaminants of ground water. A single-pass packed-bed bioreactor was utilized to study the biodegradation of organic waste mixtures consisting of PCE, TCE, and other short-chain chlorinated organics. The bioreactor consisted of two 1960-mL glass columns joined in a series. One column was packed with sand containing a microbial consortia enriched from a contaminated site. The other column provided a reservoir for oxygen and a carbon source of methane/propane that was recirculated through the reactor. Sampling was accomplished by both direct headspace and liquid effluent concentration analyses. The reactor was operated in a single-pass mode. Greater than 99% degradation of trichloroethylene, approaching drinking water standards, was observed when the bioreactor residence time ranged from 1.9 to 3.2 d. Typically, when the reactor was pulse-fed with methane, propane, and air, 1 mol of TCE was degraded/110 mol of substrate utilized. Perturbation studies were performed to characterize reactor behavior. The systems degradation behavior was affected by providing different carbon sources, a pulse feeding regime, supplementing microbial biomass, and by altering flow rates.

Feasibility testing of biofiltration technology for remediating air contaminated by a boat manufacturing facility

This research investigated and compared the use of both bench- and pilot-scale biofilters to determine the effectiveness of controlling styrene, methyl ethyl ketone (MEK), and acetone emissions from an industrial gas waste stream. Critical operating parameters, including contaminant loading rate, temperature, and empty bed contact time, were manipulated in both the laboratory and field. At steady-state conditions, the bench and pilot-scale biofilters showed a 99% removal efficiency for styrene when the contaminant loading rate was less than 50 g m-3hr-1 and 40 g m-3hr-1, respectively. Although few data points were collected in the pilot-scale reactor where the styrene load was greater than 40 g m-3hr-1, the total organic contaminant load including both MEK and acetone typically ranged between 50 g m-3hr-1 and 80 g m-3hr-1. Greater than 99% removal efficiencies were observed for acetone and MEK in the pilot-scale biofilter at all evaluated loading rates. Also studied were biofilter acclimation and re-acclimation periods. In inoculated bench and pilot biofilter systems, microbial acclimation to styrene was achieved in less than five days. In comparison, no MEK degrading microbial inoculum was added, so during the first months of pilot-scale biofilter operation, MEK removal efficiencies lagged behind those noted with styrene.

Preparing engineering students for working in teams through senior design projects

This paper explores teaming and its cultivation in senior capstone design projects to better prepare students for occupational interaction with other professionals, clients, and management to solve complex or open-ended problems. Teaming is deemed an important skill for engineers, by organizations employing engineers and other professionals. In the global marketplace organizations that value and capitalize on these skills can be more agile and competitive. The impact of current and future trends on teaming, including outsourcing and globalization, are discussed in terms of non-technical skills required for practicing engineers and the preparation of new engineers. Parallels between senior design projects and actual industry projects are drawn to highlight the key personal interaction skills and tools required for success. Examples of successful student teams and professional teams are presented for discussion. Measurements of project and teaming success by industry and professional organizations are presented. Topics include: traditional, global and virtual team structures emphasizing the nontechnical aspects necessary for modern teams including, team communication, diversity and cultural aspects, problem resolution, and other elements necessary for project success.

Bench-scale evaluation of a biofiltration system used to mitigate trichloroethylene contaminated air streams

Abstract Improper disposal practices of the once widely used short-chained chlorinated aliphatics have made them a major component of groundwater contamination. Historically, pump and treat technology has been implemented to remediate and contain such aquifer water. After being pumped to the surface, the water is frequently treated with stripper technology. As a result, there is a high volume, low concentration contaminated air stream to either be directly emitted or treated prior to release in an effort to meet regulatory compliance. This work studied the feasibility of using biofiltration technology to remediate trichloroethylene (TCE) contaminated air streams. Furthermore, work focused on operational schemes that influenced the TCE degradation potential within the system. The bench-scale biofilter system contained 42 l of organic packing material and was inoculated with a propane-oxidizing microbial consortium. Propane, the primary substrate, and TCE were introduced into the biofilter in two distinct modes. Initially, TCE and propane were both continuously added to the biofilter system. The maximum TCE degradation observed under this continuous feeding scheme was 25%. Secondly, the TCE and propane were alternately pulsed or cycled in a step-wise fashion into the biofilter system. Under this operating environment, greater than 98% removal of TCE from the air stream was achieved.

Terminal Gas Velocity during Laparoscopy

STUDY OBJECTIVE To assess the effect of port size in relation to laparoscopic gas flow and to determine the terminal velocity of gas flow during insufflation. DESIGN Analysis and mathematical modeling of gas flow characteristics. SETTING University biomedical engineering department. INTERVENTION Analytic calculations including Bernoullis equation to describe gas volumetric flow and velocity as it exits laparoscopic intraabdominal entrance sites. MEASUREMENTS AND MAIN RESULTS Mathematical modeling showed that terminal velocity of gas entering the abdomen through needles or trocars reaches a practical limit depending on size and configuration of the gas exit site, amount of turbulence, length of delivery port, and gas flow. Flow rate was evaluated for circles of 2, 5, and 10 mm and annular slots of 0.1- to 0.01-mm thickness. CONCLUSION Resistance to gas flow increases and gas exiting terminal velocity increases as the effective area of the gas exit site decreases. Depending on the configuration of variable parameters, gas flow can reach 30 m/second.

Performance assessment of major wastewater treatment plants (WWTPs) in the State of Georgia

A survey was conducted to report on the types and efficiencies of various treatment technologies being used at major wastewater treatment plants (WWTPs) in the state of Georgia. Twenty-four, full-scale wastewater treatment facilities with a design capacity of 37,850 m3 d−1 (10 Mg d−1) or greater were evaluated. One year of operating data for the 2003 calendar year was obtained from discharge monitoring reports (DMRs) provided by the Georgia Environmental Protection Division (EPD) in Atlanta. Additional information was gathered about facility operations and the types of chemicals used through review of EPD files and interviews with plant personnel. Data evaluated were: influent and effluent five-day Biochemical Oxygen Demand (BOD5), influent and effluent total suspended solids (TSS), effluent ammonia nitrogen (NH3-N), and effluent Total Phosphorus (TP). Effluent requirements for BOD5 or five-day carbonaceous biochemical oxygen demand (CBOD5), TSS, ammonia nitrogen (NH3-N), TP, and dissolved oxygen (DO) vary by facility. Time series plots showing average effluent parameter concentrations versus month indicate the effectiveness of wastewater treatment as a function of type of treatment technology and temperature. Probability plots highlight the relationship between various effluent parameters and associated treatment technology. Fourteen facilities met all permit requirements, whereas ten of the facilities reported violations with regard to flow and/or effluent parameters. Chemicals utilized, design capacity, and monthly effluent concentrations are presented in this study.

Effects of wind and choice of cover material on the yield of a passive solar still

AbstractThe development of an accurate thermodynamic model for the basic solar still has been the goal of many researchers. Glass covers are the most common choice of cover material, but are not always available under all situations and pose a large risk of physical injury if not handled with precaution. The effects of using three different cover materials (glass, Plexiglas, and plastic wrap) were investigated under a series of environmental conditions. The heat transfer model has been improved upon by the incorporation of a term for the effective emissivity of the cover, τeff. The effective τ expands upon the definition of the basic τ by incorporating the reflecting effects of the condensed, but not yet collected, water droplets adhered to the interior surface of the cover. The cumulative yield and water temperature profile predictions of the improved model were verified by a comparison with experimental results.

Biofiltration of trichloroethylene-contaminated air: A pilot study

Abstract This project demonstrated the biofiltration of a trichloroethylene (TCE)-contaminated airstream generated by air stripping groundwater obtained from several wells located at the Anniston Army Depot, Anniston, AL. The effects of several critical process variables were investigated to evaluate technical and economic feasibility, define operating limits and preferred operating conditions, and develop design information for a full-scale biofilter system. Long-term operation of the demonstration biofilter system was conducted to evaluate the performance and reliability of the system under variable weather conditions. Propane was used as the primary substrate necessary to induce the production of a nonspecific oxygenase. Results indicated that the process scheme used to introduce propane into the biofiltration system had a significant impact on the observed TCE removal efficiency. TCE degradation rates were dependent on the inlet contaminant concentration as well as on the loading rate. No microbial inhibition was observed at inlet TCE concentrations as high as 87 parts per million on a volume basis.

Feasibility testing for the on-site bioremediation of organic wastes by native microbial consortia

Abstract Microbial consortia capable of degrading chlorinated hydrocarbons and organic solvents may exist in many contaminated sediments. These native microbial communities with the capability to bioremediate toxicants on-site may prove to be a resource during remediation efforts. For this study, microbial consortia capable of degrading trichloroethylene (TCE) and mixtures of chlorinated and aromatic toxicants were enriched from contaminated sediments and the feasibility of their participation in on-site bioremediation was examined. Batch studies were used to monitor changes in the microbial community structure by monitoring signature fatty acid biomarker trends during TCE degradation. Experimental bioreactors, which utilized sand as a support matrix for the microbial community, were constructed to study TCE and organic mixed waste degradation. In continuously recycled expanded-bed bioreactors and a single-pass packed-bed reactor, mixtures of organic wastes were degraded including: benzene, xylene, toluene, tetrachloroethylene, trichloroethylene, dichloroethylenes and vinyl chloride. Degradation proceeded to >99% depletion for many contaminants. Bioreactors were stable over an 18-month period of operation while using propane or methane plus propane as energy sources and oxygen as the electron acceptor. Biodegradation was most efficient when the bioreactors were pulsed-fed, maintaing the consortia in suboptimal conditions. For the single-pass packed-bed reactor, metabolic efficiencies of 20–70 μmol substrate per μmol TCE degraded were observed for pulse-feeding regimes while continuous substrate availability experiments required >180 μmol substrate per μmol TCE. Continuous feeding experiments utilizing mixtures of organic wastes showed metabolic efficiencies of 83–240 μmol substrate utilization per μmol total organic wastes degraded. These results demonstrated efficient and simultaneous degradation of organic solvents and chlorinated hydrocarbons by environmentally derived microorganisms in laboratory reactors.