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Optimization of mixing and coagulation is paramount in the effort to optimize removal of dissolved contaminants and particles in a full-scale treatment plant. This study used a numeric modeling technique—computational fluid dynamics (CFD)-to evaluate the existing flocculation facilities at the J.D. Kline Water Supply Plant in Halifax, Nova Scotia. Several plants across Canada have similar infrastructure. These designs are based on a relatively older design approach and there is a need for evaluating the design in terms of local hydrodynamic parameters, which can be predicted effectively by CFD applications. It was demonstrated through this study that the flocculation tanks were not adequately mixed for effective floc formation. Practical outcomes of operating under ineffective mixing conditions in a treatment plant may lead to potential negative consequences such as poor floc formation, reliance on excess flocculant aid, decreased incorporation of dissolved organics in floc, and increased particle load to the filters. [ABSTRACT FROM AUTHOR]

The article focuses on a study which examines the seasonal and interannual patterns in the cover of the invasive bryozoan, Membranipora membranacea, in Nova Scotian kelp beds. The study shows that the outbreak dynamics of Membranipora membranacea on a decadal time scale relates to thermal history and the extent of kelp defoliation is dependent on the severity of infestation. It discovers that the recurrent seasonal outbreaks of the bryozoan can have an impact on native kelp populations. However, it does not detect a relationship between wave height and kelp declines in late fall.

Hyperspectral remote sensing is a proven technology for measurement of coastal ocean colour, including sea-bed mapping in optically shallow waters. Using hyperspectral imagery of shallow (<15 m deep) sea bed acquired with the Compact Airborne Spectrographic Imager (CASI-550), we examined how changes in the spatial resolution of bathymetric grids, created from sonar data (echosounding) and input to conventional image classifiers, affected the accuracy of distributional maps of invasive (Codium fragile ssp. tomentosoides) and native (kelp) seaweeds off the coast of Nova Scotia, Canada. The addition of a low-resolution bathymetric grid, interpolated from soundings by the Canadian Hydrographic Service, improved the overall classification accuracies by up to ∼10%. However, increasing the bathymetric resolution did not increase the accuracy of classification maps produced with the supervised (Maximum Likelihood) classifier as shown by a slightly lower accuracy (2%) when using an intermediate-resolution bathymetric grid interpolated from soundings with a recreational fish finder. Supervised classifications using the first three eigenvectors from a principal-components analysis were consistently more accurate (by at least 27%) than unsupervised (K-means classifier) schemes with similar data compression. With an overall accuracy of 76%, the most reliable scheme was a supervised classification with low-resolution bathymetry. However, the supervised approach was particularly sensitive, and variations in accuracy of 2% resulted in overestimations of up to 53% in the extent of C. fragile and kelp. The use of a passive optical bathymetric algorithm to derive a high-resolution bathymetric grid from the CASI data showed promise, although fundamental differences between this grid and those created with the sonar data limited the conclusions. The bathymetry (at any spatial resolution) appeared to improve the accuracy of the classifications both by reducing the confusion among the spectral classes and by removing noise in the image data. Variations in the accuracy of depth estimates and inescapable positional inaccuracies in the imagery and ground data largely accounted for the observed differences in the classification accuracies. This study provides the first detailed demonstration of the advantages and limitations of integrating digital bathymetry with hyperspectral data for the mapping of benthic assemblages in optically shallow waters. [ABSTRACT FROM AUTHOR]