Dennis D. Truax

Bench-scale studies of reactor-based treatment of fuel-contaminated soils

Abstract Biological treatment of hazardous wastes in groundwater and soils has recently assumed great importance. In particular, biotreatment of wastes from accidental spills or underground storage tank leaks has generated interest in bioremediation as a natural, economical mechanism for site decontamination. Because of drawbacks related to batch systems, and the successful use of continuous flow treatment of wastewater for several decades, it was felt that continuous treatment of such soils would be a feasible alternative treatment technique. To this end, bench-scale bioreactor treatability studies were conducted. This study used contaminated soil made in the laboratory using No. 2 diesel fuel and sand. Contamination levels studied were from 1335 to 6675 mg (TPH) as derived from No. 2 fuel oil per kg sand. Variation in mean cell age was obtained between reactors, with sufficient nutrients and oxygen made available to ensure the fuel oil organics were the only limit to microbial growth. A theoretical biokinetic model was formulated based on Monods theory of limiting substrate and continuous cultures. Biokinetic constants and removal efficiencies were evaluated. The off-gases CO 2 and volatile hydrocarbons were monitored to allow mass balance analysis of the process. The solids retention times for evaluating final TPH concentration of 100 mg/kg were also calculated. The results of this investigation showed that continuous bioreactor treatment is a viable option in the treatment of diesel-contaminated sandy soils. Removal efficiencies of up to 91% were attained at a loading of 1335 mg TPH/kg wet sand, operated at a biological solid retention time (BSRT) of 60 days. Experiments also showed that TPH desorption and volatilization were not rate-limiting in the overall removal process. Sand-to-moisture ratios in excess of 3:1 were also shown to retard TPH removal rates very little. However, biokinetic constants were found to vary over a range of values. This was particularly true at varying diesel loading levels. Nevertheless, significant removal efficiency (up to 86%) was noted at the highest loading level tested, 6675 mg TPH/kg wet sand.

Combined Ozone and Ultraviolet Inactivation of Escherichia coli

The kinetics of Escherichia coli inactivation using ozone and ultraviolet (UV) radiation, separately and simultaneously, was evaluated at 25 degrees C in buffered (pH 6.0, 7.0 and 8.0), demand-free media. While ozone was found to be a stronger disinfectant than UV radiation, using both simultaneously was more effective than using them individually. Inactivation kinetics was pseudo first-order for the three treatment processes, while the disinfection rate was a linear function of the disinfectant dose. The synergism observed in microbial inactivation when the disinfectant processes were combined was illustrated by estimates of kinetic model parameters. This synergy was attributed to the generation of hydroxyl radicals via ozone photolysis. Subsequently, dosage calculations, as based on disinfectant level and exposure time, indicated that the simultaneous use of UV and ozone could substantially reduce their individual doses.

Sustainable Construction Education Using Problem-Based Learning and Service Learning Pedagogies

AbstractIncorporating the concepts of sustainable development in engineering education is becoming a necessity in order to prepare future professionals with the dynamic mindset and broad knowledge needed to effectively and efficiently solve the interdisciplinary challenges of the 21st century. To this end, utilizing the principles of active learning towards sustainable construction education leads to stronger learning outcomes and development for students. The objective is to enhance the undergraduate student skill-set that is required to make them more enabled, aligned, and supported to design, construct, and operate our infrastructure systems. In this paper, the authors provide the associated course development principles grounded in problem-based-learning (PBL) and service-learning (SL) pedagogies, course management strategy, as well as the educational and learning philosophies. To this end, the course PBL activities utilized interrelated and mutually supportive assignments and projects where the assig...

Wetlands for Wastewater Treatment.

This paper provides a review of the treatment technologies, which utilize natural processes or passive components in wastewater treatment. In particular, this paper primarily focuses on wetland systems and their applications in wastewater treatment (as an advanced treatment unit or decentralized system), nutrient and pollutant removal (single and multiple pollutants, and metals), and emerging pollutant removal (pharmaceuticals). A summary of studies involving the plant (vegetation) effects, wetland design and modeling, hybrid and innovative systems, storm water treatment and pathogen removal is also included.

A Critical Evaluation of Advanced Oxidation Processes for Emerging Contaminants Removal

Removing emerging contaminants from waste streams has become a topic of growing interest. The adverse effects of endocrine disrupting chemicals (EDCs) and pharmaceutical and personal care products (PPCPs) have been well documented, but much remains to be known about these contaminants and their removal. Their removal with traditional methods has not been entirely successful. However, adequate degradation can be achieved through the use of advanced oxidation processes (AOPs). Multiple factors must be considered when completing an in-depth comparison; therefore, process engineering, environmental, and economic and social parameters were included in a deeper analysis. This study presents a ranking system to numerically score the performance of various AOPs (e.g., Ozonation, UV irradiation, Photocatalysis, Fenton reaction, and integrated processes) in several categories of parameters under engineering, environmental, and socioeconomic components. From this preliminary assessment, it was noted that H2O2/O3 (Perozonation) presented the highest average ranking (3.45), with other processes showing comparable performance. TiO2 photocatalysis received the lowest ranking (2.11).

Kinetics of pseudo-continuous flow bioreactor treatment of diesel contaminated soils

A bioremediation treatability study was evaluated on a laboratory scale for its effectiveness in treating a sandy soil contaminated at 1500 mg kg−1 wet weight by No. 2 diesel fuel. A continuous type reactor system was used and by continuously loading different reactors at different levels, a variation in mean cell age was obtained. Adequate nutrients, moisture, and oxygen were available at all times so that the fuel was the only limiting nutrient and was measured in terms of TPH. The off-gases C02 and volatile hydrocarbons were also monitored.At steady state, biokinetic equations which conform with microbial physiology and growth kinetics were evaluated and included the following coefficients: specific growth rate, specific substrate utilization rate, substrate affinity (half-saturation constant), microbial decay rate and growth yield. The solids retention time for evaluating final TPH concentration of 100 mg kg−1 were also calculated.The reactors reached steady state conditions at 70 days based on biomass and TPH levels. This preliminary study shows that a continuous bioreactor system is effective in reducing diesel fuel concentration over a given period of time, and that the kinetics of the process can be evaluated. Removal efficiencies up to 80% were attainable.

Evaluation of On-site Wastewater Disposal Systems in Mississippi Coastal Areas

Groundwater and surface water contamination have been linked to inadequate or failing on-site residential wastewater treatment and disposal systems. The potential for groundwater contamination in coastal areas with shallow water tables is higher; subsequently the ability of soil, microorganisms, and vegetation to mitigate pollutants may be reduced. This study evaluated the performance of the four types of on-site wastewater treatment and disposal systems predominantly used on the Mississippi Gulf Coast. One type of system was deemed inappropriate for this region as none of the dozens of installations examined were functioning acceptably. Of the remaining three types, subsurface water samples were collected from representative sites using lysimeters and monitoring wells. Apart from general performance evaluation of these systems, seasonal changes translating into possible variation in disposal efficiencies and groundwater contamination were investigated. Statistical analysis of variations in organics (COD and BOD5), nitrogen (TKN and NH4+–N), and fecal coliform concentrations was used to identify probable deficiencies in systems tested and to recommend changes to governing standards.

Problem-Based-Learning and Learning-Through-Service for Sustainability Education

This paper shows how problem-based-learning (PBL) and learning-through-service (LTS) can provide a strong framework for fostering students’ adaptive expertise, flexibility, creativity, innovation, and passion in the classroom. Mississippi State University (MSU) represented by its Civil and Environmental Engineering Department (CEE) is currently in the design-development stage for the construction of a new Civil and Environmental Engineering Complex (CEEC). CEE is garnering a new focus on sustainability with special emphasis on environmentally responsible design, construction, and operation of constructed facilities. To this end, the authors have mentored a group of 22 undergraduate junior students under the High Performance Sustainable Construction class to provide a comprehensive Leadership in Energy and Environmental Design (LEED) analysis for the new CEEC using the 2009 Reference Guide for Green Building Design and Construction, the student work shows that CEEC can possibly earn up to 74 points to acquire a Gold LEED Certification. This study shows that PBL and LTS can enhance students’ abilities of understanding and solving real world civil infrastructure problems and challenges. Also, this student-driven teaching approach instills a creative learning environment, understanding of the surrounding world, and a sense of social responsibility.

TITLE: Optimization Technique for Design of Gravity Sewers and Related Aspects

Hydraulic design of piped gravity sewer systems needs to be optimized for stipulated design guidelines. Though separate systems for transporting storm run-off and sanitary flows are preferred, many cities are forced to use combined sewer systems to jointly transport both flows. Faulty and ad hoc design concepts can undermine sewer hydraulics and lead to flooding. At times, maximum depth of excavation for new sewers is stipulated at the project outset based on site conditions like congestion, soil characteristics, adjoining existing infrastructure, constructability, space constraints, socio-economic and environmental aspects. This paper summarizes a set of evaluation parameters used to assess the efficiency of a system’s hydraulic design, including: equivalent diameter (De), pipe utilization factor (fPU), equivalent slope (Se), equivalent invert depth (Ie), and equivalent velocity (Ve). The approach delineated can be a tool to ensure consistency in design, eliminate surcharge, and reconcile competing system operational constraints.