The influence of surfactants on a perchloroethene dechlorinating mixed culture was investigated in laboratory experiments. Seven surfactants, representing each of the surfactant classes, were screened for their effects on the rate and extent of perchloroethene dechlorination. Based on screening results, a nonionic surfactant, Tween 80, and an anionic surfactant, Steol CS-330, were selected for use in further studies. Dechlorination of perchloroethene to dichloroethene, vinyl chloride, and ethene occurred in all Tween 80 amended microcosms with a depressed rate of ethene production as the only adverse effect. Steol CS-330, however, inhibited dechlorination beyond dichloroethene at all surfactant concentrations exceeding 25 mg/L. Attempts to acclimate a culture to the surfactant were unsuccessful. Inhibition of vinyl chloride and ethene production was reversible upon dilution of the surfactant to 10 mg/L or below indicating that surfactant interactions with the enzyme system responsible for reductive dechlorination of dichloroethene was the most likely cause of inhibition.

The design and performance of soil vapor extraction (SVE) systems can be evaluated using mathematical models. A lack of knowledge in how to select the appropriate model and use it properly for field settings are major obstacles limiting the usage of existing codes. The predictive capabilities of many of the commercially available models have never been tested against observed performance of full-scale SVE systems. In this study, we demonstrate the applicability of a coupled, subsurface flow and vapor transport code for simulating the performance of a field-scale soil vapor extraction system. The effects of various modeling simplifications on the accuracy of model predictions, and on the computational time and effort are assessed. VENT3D, a three-dimensional multi-component, multi-phase chemical partitioning model that simulates isothermal flow and transport of organic compounds in the subsurface was selected for testing against data to demonstrate how similar codes can be used to predict the performance of a full-scale SVE system. Simulations were compared to data from pilot- and full-scale operation of an SVE system that was used to remediate a JP-4 jet-fuel contaminated site at Hill Air Force Base, Utah. The standard JP-4 composition was approximated by an equivalent mixture of 11 constituents and as a single constituent using equivalent, mole-fraction-weighted chemical properties, to determine the value of representing mixtures in a multi-component fashion. Air permeability tests data were analyzed independently to estimate vertical and horizontal permeabilities with an analytical model that simulates idealized, axisymmetric gas flow. The initial contaminant mass was the major parameter that had to be adjusted to simulate the contaminant removal using data from pilot and full-scale tests. The value of modeling field studies in a 3-dimensional mode versus 2-dimensional was evaluated. The trade-off between added accuracy in model predictions due to higher problem dimensionality, averaging flow fluctuations, and detailed representation of mixture components, and the extra computational effort and complexity was studied. The model was also used to evaluate the extent of contamination under natural conditions, to predict the effect of long-term operation on cleanup, and to demonstrate how modeling can be used to improve system design and performance.

A mathematical simulation model is developed that calculates the evolution of particle removal and headloss in a packed bed filter, as functions of the morphology of the colloidal particle deposits in the filter. The expressions derived are based on the postulate that particles form deposits that grow as mass fractals. The model is calibrated and validated with a set of laboratory data previously obtained. The calibrated value of fractal dimension was found to coincide with measurements obtained in an earlier study using light scattering. The effect of the filtration velocity and particle size on the fractal dimension of the deposits is evaluated. The hypothesis that higher filtration velocities create denser deposits is supported. However, a trend of increasing fractal dimension with decreasing particle size runs counter to theoretical expectations. The model is extended to include the effect of variable conditions in the influent.

The influence of dechlorinating microorganisms on PCE and its reduction products in a residual non-aqueous phase liquid (NAPL) source zone was investigated. Experiments were conducted in upflow anaerobic columns containing glass beads contaminated with a residual NAPL consisting of tridecane and PCE. Columns were inoculated with a mixed PCE-dechlorinating culture, and fed a nutrient medium that included electron donor (pyruvate and/or lactate) at a wide range of concentrations. The systems that were monitored for effluent organic acids (pyruvate-fed) demonstrated evidence of active fermentation. Comparisons between biotic and abiotic columns demonstrated that dechlorination resulted in an increase in total PCE removal, up to a factor of 16 over dissolution. PCE was sequentially reduced as far as vinyl chloride. Total chlorinated ethenes removal was enhanced up to 6.5 times over dissolution removal. The system fed the highest electron donor level, interestingly, lost dechlorinating activity early in the experiment.

The interaction of arsenite (As(III)) and arsenate (As(V)) with magnetite nanoparticles has been studied to evaluate the environmental impact of magnetite nanoparticles and possible beneficial use of these nanoparticles in water treatment. The effects of particle size (20--300 nm) and pH on the sorption/desorption of AS(III) and As(V) on magnetite nanoparticles were examined. On a surface area basis, it was found that large and nanometer scale magnetite particles had similar maximum As(III)/As(V) sorption capacities. However, the sorption of As(III) to magnetite showed the same Langmuir sorption slope for the nanometer scale particles as for the large particles, while the sorption of As(V) to magnetite showed a larger Langmuir sorption slope for the nanometer scale particles than for the large crystals. The particle size effect on sorption is constant over a pH range of 4.8 to 8. Sorption of As(V) was found to be greater at lower pH, while sorption of As(III) was not pH sensitive. The sorption data of both As(III) and As(V) have been modeled with the Diffuse Double Layer model. Stronger desorption hysteresis was observed for both As(III) and As(V) sorption to nanometer scale magnetite particles than that to large magnetite particles, which indicates that the decrease of particle size may increase the affinity of sorption. The experimental results showed that magnetite nanoparticles are potentially a very effective sorbent for arsenic removal in water treatment.

The settling velocity of aggregates found in engineered water and wastewater treatment facilities are usually assumed to follow Stokes' law. These particles, however, are typically porous and may be fractal in nature. As a result, they have very different sedimentation characteristics. This study focuses on the comparison of several techniques used to characterize the settling properties of fractal aggregates. Aggregates made of latex particles destabilized using calcium nitrate were formed in the laboratory. Settling velocity and size were then determined for each floc using latex particles ranging 0.03 mum, 0.05 mum, and 2.65 mum in diameter. Light scattering techniques were used to calculate the fractal dimension of the aggregates. Fractal dimension ranged from 1.6 to 2.3 in the experiments. A settling column was constructed to analyze actual settling velocities of flocs. Observed settling velocities of these flocs were consistently higher than those predicted using Stokes' law (which assumes an impermeable sphere).

In a previous study, pilot-scale bioslurry reactors were used to treat soils highly contaminated with 2,4-dinitrotoluene (2,4-DNT) and 2,6-dinitrotoluene (2,6-DNT). The treatment scheme involved a soil washing process followed by two sequential aerobic slurry reactors augmented with DNT mineralizing bacteria. This previous work found that constant monitoring was necessary to avoid long lag periods upon refeeding. In this study, it was determined that the heterogeneous distribution of soil in the reactor deleteriously impacted direct monitoring of DNT concentrations. Instead, the use of nitrite production or NaOH consumption as surrogate monitoring parameters proved to be more accurate predictors of reactor performance. A model was developed to predict the distribution and biodegradation of DNT in the reactors. Analysis of model results showed that the maximum substrate utilization rate controlled DNT degradation rates in the reactor, a population shift occurred after approximately 26 days, and phosphorous was limiting at high solids loading rates.

In Abbotsford’s Clayburn Watershed, urban rainwater runoff and agricultural land drainage generally enter surface watercourses untreated. Existing literature suggests that both inputs can potentially contribute to non-point source pollution. This study evaluates the effects of non-point source pollution on surface water quality and assesses the role of wastewater management in mitigating these effects. Based on a water quality sampling program carried out between September 2007 and August 2008 both urban rainwater runoff and agricultural land drainage were shown to significantly and negatively affect surface water quality. Subsequently, it is recommended that non-point source pollution should be included in Abbotsford’s wastewater management strategy. Mitigation measures proposed include retention treatment of rainwater in urban areas and manure recycling (waste to energy) projects for agricultural lands.

Street tree health in the City of Victoria, British Columbia has declined in the last decade. Using the health condition of six tree genera representing 72 % of the total 17,601 COV street trees inventory in 2005 this trend is likely in large part due to lack of moisture from June to October. Declining health is evident in branch die back and early leaf drop especially on species with a medium to high water requirement. The Prunus genus (cherries and plums) in particular, which comprises 29% of all COV street trees, was rated at 54% fair to dead condition which is 20% higher than all COV street trees. Current summer precipitation from June to early October totals 105 mm and evapotranspiration for the same period totals -382 mm leaving a moisture deficit of 277 mm. This deficit is projected to increase (based on extreme models) to 362 mm by 2050 and 420 mm by 2080 which will have a devastating impact on street trees which will not able to withstand the intense moisture deficit interval. Recommendations on species selection and maintenance alternatives include: regular monitoring with site specific information, changing the list of trees used for selection and planting, increase watering, and increased maintenance. The results and recommendations of this study may be of value to other jurisdictions that will be affected by the impacts of moisture deficit related to climate change.

This research investigates the nature of the influences children have on their parents' environmental behaviour following involvement in a week long environmental education experience. Using the grounded theory method, children and their mothers were interviewed about their ideas about the ways they felt the children influenced their parents. Four of the five children interviewed reported that they influenced their parents, citing examples of environmental action in the home as an area of influence. Similarly, the majority of parents felt their environmental knowledge and behavior was influenced by their children. What appear to be barriers to effective child-to-parent influence communication are explored, including aspects of program enjoyment and relationships between family members. The theme of child confidence and its relationship to child-to-adult influence is also considered. Areas for future research are identified, including a recommendation for research into the child-to-father influence relationship.