Richard G. Zytner

Sorption of benzene, toluene, ethylbenzene and xylenes to various media

Abstract The sorption and desorption characteristics of the major components of gasoline were determined for five media; sandy loam soil, organic top soil, clay soil, peat moss and granular activated carbon (GAC). Emphasis was placed on the sorption of benzene, toluene, ethylbenzene and xylenes (BTEX), the aromatic hydrocarbons contained in gasoline. The results showed that the Freundlich isotherm satisfactorily described the sorption and desorption of dissolved BTEX on the media tested. The organic carbon content of the media was an important factor in both sorption and desorption, with the order of sorption preference being GAC, peat moss, organic top soil, clay soil and sandy loam soil. The soil—water partition coefficient (Koc) for the BTEX compounds and Total BTEX suggests that the BTEX compounds will migrate quickly through soil, with benzene being the fastest followed by toluene, m-, p- and o-xylenes and ethylbenzene.

Biodegradation of Diesel Fuel in Soil Under Various Nitrogen Addition Regimes

Bioremediation is a growing technology for treating fuel-contaminated soils. Many biological, physical, and chemical parameters control the rate and efficiency of this process, including type and concentration of contaminants, temperature, oxygen content, and nutrient status. This study investigated the effect that nitrogen sources and concentrations had on the degradation rate of diesel fuel in nutrient limited soil at two carbon-to-nitrogen ratios. The different sources of nitrogen studied were ammonium nitrate, ammonium sulfate, potassium nitrate, urea, and urea oligomers (control release fertilizer). Laboratory experiments were conducted on field-contaminated soil using sealed bioreactors at a controlled temperature of 25°C. For both carbon-to-nitrogen ratios tested, hydrocarbon degradation rates were the highest for the ammonium sulfate (20:1 at 0.032 d−1; 40:1 at 0.019d−1) and urea treatments (20:1 at 0.025 d−1; 40:1 at0.011 d−1). A degradation rate correlation as a function of nitrate and ammonia concentrations was developed. The correlation suggests the occurrence of nitrate inhibition at elevated nitrate concentrations.

Adsorption-desorption of trichloroethylene in granular media

Sorption studies were conducted to determine the adsorption and desorption characteristics of a common synthetic chemical, trichloroethylene (TCE) in four granular media; sandy loam soil, organic top soil, peat moss and granular activated carbon (GAC). The results showed that the Freundlich Isotherm satisfactorily represents adsorption and desorption of dissolved TCE in these media and that the organic carbon content is an important factor in both processes. The soil-water partition coefficient (Koc) for TCE suggests that it will migrate quickly through soil.

Removal of ibuprofen from wastewater: comparing biodegradation in conventional, membrane bioreactor, and biological nutrient removal treatment systems

Pharmaceuticals are continually being introduced into the influent of municipal wastewater treatment plants (WWTPs). Developing a better understanding of pharmaceutical removal mechanisms within the different treatment processes is vital in preventing downstream contamination of our water resources. In this study, ibuprofen, a popular over-the-counter pain reliever, was monitored by taking wastewater samples throughout the City of Guelph municipal WWTP. Greater than 95% of ibuprofen was found to be removed in the aeration tank, with aerobic biodegradation being the dominant mechanism. For comparison, first-order kinetics were used to quantify ibuprofen biodegradation in a conventional WWTP aeration tank and in a membrane bioreactor (MBR) pilot plant. The rate constants, k biol, for the conventional tank and the MBR were determined to be (-6.8+/-3.3) L/g SS*d and (-8.4+/-4.0) L/g SS*d, respectively. These two rate constants were found to be statistically similar. Preliminary study of a biological nutrient removal pilot system also suggests that ibuprofen can be anaerobically degraded.

Influence of water on the supercritical fluid extraction of naphthalene from soil

Supercritical fluid extraction (SFE) is an innovative soil remediation technology. To aid system evaluation and design, thermodynamic and kinetic parameters have been measured using a naphthalene contaminated, loamy sand at various water contents. The experimental results show that supercritical carbon dioxide can easily extract naphthalene from soil when the water content is below 10%. At low water contents, mass transfer is rapid and the equilibrium partition coefficient is independent of the soils water content. However, the overall mass transfer coefficient, (kova), decreases by at least a factor of 200 as the water content increases from 10 to 20%.

Parameters influencing oxygen uptake at clarifier weirs

Oxygen uptake at clarifier weirs was investigated for both clean water and primary wastewater. A pilot-scale model with cross-sectional geometry similar to clarifier weirs was constructed to carry out the study. The drop height, type of flow regime over the weir, hydraulic loading, and weir shape were identified as important parameters influencing mass transfer. Empirical correlations predicting oxygen uptake were developed for different weir configurations. A correlation using the α-factor was developed to predict the oxygen transfer in primary wastewater using clean water. These correlations are a first step in estimating volatile organic compound emissions for wastewater flows over clarifiers at wastewater treatment plants.

Measurement of solubilities in supercritical fluids using a piezoelectric quartz crystal

Abstract Solubility data is essential for any application of supercritical fluids. A new technique has been developed using a piezoelectric quartz crystal to measure solubilities. A small mass of solute is deposited on the crystal and solubility is measured by observing the crystal’s frequency change as this solute dissolves in the supercritical fluid. The technique is ideally suited to solutes which exhibit low solubilities. Solubility measurements of bis(acetylacetonato)copper(II) (Cu(acac) 2 ) in supercritical carbon dioxide were in good agreement with existing literature values. New solubility data were also measured for bis(thenoyltrifluoroacetonato)copper(II) (Cu(tta) 2 ).

Passive volatilization behaviour of gasoline in unsaturated soils

Abstract Gasoline behaviour in the unsaturated zone is difficult to predict as a number of soil factors, gasoline properties and environmental conditions will determine the eventual fate of a spill. These factors include the diffusive and convective processes that contribute to passive volatilization. To gain a better insight into passive volatilization and how it can impact the clean-up of a contaminated site, batch column experiments were completed. Three soils were tested at varying initial gasoline contents, water contents, and at room and sub-zero temperatures. The results indicate that immiscible phase movement to the surface is a significant contributor to passive volatilization. However, the immiscible phase movement ceases once the gasoline content has dropped below a threshold level. The driving force necessary for immiscible phase movement is maintained by gasoline precipitation at the soil surface. Higher soil water contents inhibited the volatilization of gasoline as water impacted both the diffusive and wicking movement of the gasoline. Sub-zero temperatures reduced volatilization and extended the time to cessation of wicking behaviour.

Three-dimensional numerical model for soil vapor extraction

Mass transfer limitations impact the effectiveness of soil vapor extraction (SVE) and cause tailing. In order to identify the governing mass transfer processes, a three-dimensional SVE numerical model was developed. The developed model was based on Comsol Multiphysics a finite element method that incorporates multi-phase flow, multi-component transport and non-equilibrium transient mass transfer. Model calibration was done against experimental data from previously completed lab-scale reactor experiments. The developed model, 3D-SVE, nicely simulates laboratory findings and allows for changes in the important governing mass transfer relationships. The modeling results showed that a single averaged mass transfer value is a poor representation of the entire SVE operation, and that a transient mass transfer coefficient is required to fully represent SVE tailing. Calibration of the lab scale model showed that the most important mass transfer occurs between the NAPL and vapor phase.

BREAKING WAVES: REVIEW OF CHARACTERISTIC RELATIONSHIPS

The analysis of the water wave breaking phenomenon has been on-going for almost 150 years, and many research papers have been published approximating both the local geographic and geometric characteristics of breaking waves. This review of original empirical work, the relationships theorized by each author, and their regions of applicability are detailed to give a historical perspective of wave breaking research but also to illustrate advances in recent years. Subsequently published validity investigations by other authors show the variability and limitations of each approximation and illustrate that the level of understanding in wave breaking parameters has progressed considerably. The understanding of the defining variables in wave breaking progresses annually, however predicting the location, depth and shape of the wave at breaking is still not universally defined. This is in part due to the inherent variability in nature of breaking waves; however, it is compounded by a lack of a collective measurement and definition system for wave breaking parameters.