Hugh R. Whiteley

TRANSPORT OF MICROORGANISMS THROUGH SOIL

Microorganisms migrating into and through soil from sources on the land surface may cause a serious threat to both ground and surface waters. It has been estimated that microorganisms can migrate significant distances in the field. Results from various studies suggested that preferential flow through macropores, worm holes, cracks, and fractures is the main reason for such observations. However, a quantitative representation of this phenomenon has not been provided. Microorganisms migrate through soil by advection and dispersion, while being subjected to effects of filtration, adsorption, desorption, growth, decay, sedimentation and chemotaxis. Both laboratory and field investigations have contributed important information on bacterial movement in soils. Qualitative comparisons are generally transferable from laboratory to field situations. Quantitative agreement is much more difficult to establish. Available mathematical modelling of microbial transport is limited in practical application because of the simplifying assumptions used in its development.

Review: Denitrification in temperate climate riparian zones

Excess nitrate (NO3-) in lakes and streams has deleterious effects for environmental and human health. Nitrate concentrations have become problematic in agricultural watersheds due to increased use of fertilizers and improper management of livestock wastes. Research has indicated that the planting and/or preservation of riparian buffer zones can be an effective means of reducing pollution from agricultural fields (Osborne and Kovacic, 1993; Jordan et al., 1992; Simmons et al., 1992). Biological denitrification is the most desirable means of nitrate attenuation as the microbial conversion of NO3- removes nitrate from the watershed in the form of N gases. Despite the inherent value of biological denitrification, a comprehensive review discussing the role of this process in removing nitrate from riparian zones is lacking. In this paper we examine the results and conclusions of past research on the topic of denitrification in riparian zones and make recommendations for future research in this area. The need for subsurface denitrification assays in riparian zones is emphasized.

Sediment-Removal Efficiency of Vegetative Filter Strips

Field experiments on vegetative filter strips (VFS) showed average sediment-removal efficiency varied from 50 to 98% as flowpath length increased from 2.44 to 19.52 m. Almost all of the easily removable aggregates (i.e. aggregates larger that 40 mm in diameter) can be captured within the first five meters of the filter strip. However, the remaining small-size aggregates are very difficult to remove by filtering flow through grass media, as even relatively low levels of turbulent energy in the water is sufficient to keep the finer sediments in suspension. The only effective mechanism for removal of small-size sediments is infiltration. Experiments with appreciable infiltration (low to moderate flow rates on the longer plot lengths), showed removal efficiencies of 90% or higher. The sediment-removal efficiency of the filter strip does not increase much by increasing the width of the filter strip beyond ten meters. Improved efficiency of VFS can be achieved through the installation of a drainage system to increase infiltration.

Evaluation and use of a biotracer to study ground water contamination by leaching bed systems

There is an increasing concern about dangerous levels of bacterial contamination of rural ground water resources in Ontario and throughout the world. Recent studies in rural parts of Canada have identified leaching bed systems as one of the major sources of this contamination. Field studies were undertaken to evaluate bacterial contamination from three different types of leaching bed designs, using nalidixic acid-resistant Escherichia coli (E. coli NAR) as a biotracer. This biotracer was used rather than passive ground water sampling to clearly identify the source of the contamination and also to allow the determination of travel times and distances more clearly. While this biotracer has been used for other studies its use in actual working septic systems has not yet been reported. This work has also shown that E. coli NAR is an excellent biotracer and can be used to give an accurate assessment of a leaching beds performance provided it is introduced into the system over a reasonable period of time. Results also show that bacteria are not necessarily removed before the effluent reaches the ground water. The speed, distance of travel and attenuation of biotracer concentrations was found to be highly related to precipitation events, age of system and depth of unsaturated zone below the bed.

Development of a Management Tool for Vegetative Filter Strips

Vegetative filter strips (VFS) are widely advocated as a BMP to safeguard and /or remediate water quality in streams. This study provides management tools for …

Evaluation of the Qualitative Habitat Evaluation Index as a Planning and Design Tool for Restoration of Rural Ontario Waterways

The applicability of the Qualitative Habitat Evaluation Index (QHEI) as a planning and design tool for stream assessments in southern Ontario was evaluated. QHEI assessments were made at 50 Ontario sites where benthic data were available or collected. QHEI was correlated to % Ephemeroptera-Plecoptera-Trichoptera (%EPT), Hilsenhoff Biotic Index (HBI) and Taxa Richness. QHEI reference ranges of >67.5, 52.5 to 67.5, and <52.5 were determined for Exceptional, Good, and Marginal/Poor habitats, respectively. Predictive regression equations were developed for stream assessment and rehabilitation design. However, only about 50% of the variance in biologic indices is explained by geomorphic stressors within the stream. Further improvement of QHEI and refinement of reference ranges specific to Ontario regions will require further data collection and modelling.

Ecological Flow Assessment for Hanlon Creek, Ontario: Use of Synthesized Flows with Range of Variability Approach

Maintaining the natural hydrologic variability of streamflows is critical for conserving stream ecosystems. The consequences for streamflow of gradual urbanization were investigated for a small Ontario watershed. A hydrologic model (GAWSER), calibrated for current conditions, was used to generate a 41-year daily streamflow time series at eight points of interest. Model parameters were altered to represent different land use scenarios and streamflow time series were generated for each scenario. A flow assessment tool, Indicators of Hydrologic Alteration (IHA), was used to characterize the flow regimes for each scenario in terms of 34 ecologically-related, hydrologic parameters. The Range of Variability Approach (RVA) was applied to assess the degree of flow alteration and to set initial streamflow management targets to restore a more natural flow regime. The study demonstrates the suitability of the tools for simulating daily flows, characterizing the flow regime, quantifying the alteration of the flow regime due to urbanization, and setting preliminary flow targets for an urbanized watershed.

Ranking of waterways susceptible to adverse stormwater effects.

A new method is developed to integrate empirical data and watershed properties with geographic information systems (GIS) tools to prioritize the sensitivities of streams to deterioration arising from adverse stormwater effects. A risk-based decision-making process based on fuzzy logic methodology is employed, using a broad spectrum of parameters to evaluate stream systems, to rank susceptibility to adverse stormwater effects, and to establish management priorities. The methodology is applied to Grindstone Creek and Highland Creek, two systems with varying susceptibility to the effects of erosion. A comparison of results shows that Highland Creek has a greater risk than Grindstone Creek. Overall, the fuzzy logic methodology was found to be an effective tool for evaluating and prioritizing streams that are susceptible to adverse stormwater effects to establish management priorities.

On the Optimization of Uncertainty, Complexity and Cost for Modeling Combined Sewer Systems

This chapter introduces a tentative procedure for estimating the minimum level of complexity of a computational model for designing a cost-effective combined s…

Quality of Stormwater From Residential Areas.

Stormwater from urban residential areas has been found in several studies to contain a variety of pollutants. These include solids, nutrients, chlorides, bact…