Thesis (Ph.D.)--Murdoch University, 2004. / Thesis submitted to the Division of Science and Engineering. Bibliography: p. 277-301.

Thesis (M.Sc.)--Aberdeen University, 2009. / Title from web page (viewed on Dec. 1, 2009). Includes bibliographical references.

Thesis (Ph.D.)--Aberdeen University, 2008. / Title from web page (viewed on July 20. 2009). Includes bibliographical references.

This research investigated the ecological significance of GW-SW interactions in the hyporheic zone of two Scottish mountain rivers (the Girnock Burn and the River Feshie).  The research comprised three components: (i) an assessment of the influence of GW-SW interactions on the spatio-temporal variability of hyporheic hydrochemistry and macroinvertebrate community structure, (ii) an evaluation of the influence of GW-SW dynamics on small-scale spatio-temporal variability in hyporheic thermal regimes, and (iii) an investigation of the spatial relationship between Atlantic salmon <i>Salmo salar </i>(L.) spawning distributions and patterns of GW-SW exchange in a braided river reach. In the Girnock, marked inter- and intra-reach differences in hyporheic water quality were found and linked to spatio-temporal variability in GW-SW exchange.  Up to 25% of the spatial variability in invertebrate community structure could be accounted for by differences in hyporheic water quality.  Community composition varied markedly between winter, spring and summer seasons, with the relative importance of individual water quality variables differing between seasons. There was much heterogeneity in streambed temperature regimes across the study reaches, with data suggesting that long-residence groundwater contributed significantly to hyporheic exchange.  However, at small (cm to m) scales thermal variability was most likely explained by the interaction of reach-scale GW-SW exchanges with smaller-scale, current-bed form induced hyporheic exchange. In a braided section of the River Feshie, spatially complex and temporally dynamic GW-SW exchange patterns occurred.  Salmon spawning was concentrated in locations characterised by upwelling groundwater at depth, with up to 66% of spawning sites recorded in groundwater dominated channels.

Thesis (M. S.)--Civil and Environmental Engineering, Georgia Institute of Technology, 2010. / Committee Member: Pavlostathis, Spyros; Committee Member: Spain, Jim; Committee Member: Tezel, Ulas. Part of the SMARTech Electronic Thesis and Dissertation Collection.

Thesis (M. Phil.)--University of Hong Kong, 2007. / Title proper from title frame. Also available in printed format.

This thesis investigates nutrient contribution to six hyper-eutrophic lakes located within close proximity of each other on the Swan Coastal Plain and 20 kilometres south of the Perth Central Business District, Western Australia. The lakes are located within a mixed land use setting and are under the management of a number of state and local government departments and organisations. These are a number of other lakes on the Swan Coastal Plain for which the majority are less than 3 metres in depth and considered as an expression of the groundwater as their base is below the regional groundwater table throughout most of the year. The limited amount of water quality data available for these six lakes and the surface water and groundwater flowing into them has restricted a thorough understanding of the processes influencing the water quality of the lakes. Various private and public companies and organisations have undertaken studies on some of the individual wetlands and there is a wide difference in scientific opinion as to the major source of the nutrients to those wetlands. These previous studies failed to consider regional surface water and groundwater effects on the nutrient fluxes and they predominantly only investigated single wetland systems. This study attempts for the first time to investigate the regional contribution of nutrients to this system of wetlands existing on the Swan Coastal plain. As such, it also includes new research on the nutrient contribution to some of the remaining wetlands. The research findings indicate that the lake sediments represent a considerable store of nutrients (nitrogen and phosphorus). These sediments in turn control the nutrient status of the lake's water column. Surface water is found to contribute on an event-basis load of nutrients to the lakes whilst the groundwater surprisingly appears to contribute a comparatively low input of nutrients but governs the water depth. Analysis of the regional groundwater shows efficient denitrifying abilities as a result of denitrifying bacteria and the transport is localised. Management recommendations for the remediation of the social and environmental value of the lakes include treatment of the lake’s sediments via chemical bonding or atmospheric oxidation; utilising the regional groundwater’s denitrifying abilities to ‘treat’ the surface water via infiltration basins; and investigating the merits of managed or artificial aquifer recharge (MAR).

Thesis (Ph.D.)--University of Western Australia, 2007.

published_or_final_version / abstract / Earth Sciences / Master / Master of Philosophy

Wetland-based treatment systems are often implemented as a method to remove unwanted substances from contaminated groundwater. Wetlands are effective due to the high biological activity that naturally takes place in the rhizosphere and soil. In support of a demonstration surface wetland system at a site in Columbus, Georgia, laboratory-scale wetland systems were designed to study the effect of different carbon sources and their biodegradability, COD:N ratio and temperature on the rate and extent of nitrate reduction of nitrate-bearing groundwater. Nitrate reducing bacteria are ubiquitous in surface and subsurface wetlands but a major limiting factor for these systems is carbon availability. Two major carbon sources were investigated in both continuous-flow and batch systems: a natural source, hay and a commercial source, MicroC GTM, a concentrated carbohydrate mix. Between these two carbon sources, the nitrate removal rate was not significantly different as long as sufficient biodegradable carbon was provided. The effect of both hydraulic retention time (HRT) and COD:N ratio on nitrate removal were investigated in continuous-flow systems. The specific nitrate removal rate in open to the atmosphere batch reactors was estimated at 0.55 mg N/mg biomass VSS-day. The effluent nitrate concentration in a continuous-flow system maintained with an HRT of 5 days at room temperature (22 to 23°C) was less than 3 mg nitrate-N/L. The COD:N ratio was kept at 6:1 for the majority of the experiments (approximately twice the theoretical requirement) to ensure sufficient carbon loading. Lower COD:N ratios of 5, 4, 3, 2, 1, and 0.5 were also investigated in the continuous-flow system and the minimum required carbon loading to achieve an effluent nitrate concentration below 10 mg N/L for an influent groundwater nitrate concentration between 65 and 70 mg N/L was determined to be 5:1 COD:N. The effect of temperature on the nitrate removal rate was also investigated at 22, 15, 10 and 5°C. As expected, the rate of nitrate reduction decreased with the decrease in temperature, especially below 10°C. Overall, the surface wetland is a feasible solution to treating nitrate-bearing groundwater even at relatively low ambient temperature values, provided that sufficient, biodegradable carbon is present.