The 'migrating thermal bar' phenomenon, known to occur in certain large, dimictic, freshwater lakes, has been studied in laboratory and mathematical models. The temperature fields observed in the laboratory agreed with those observed in Lake Ontario and a linear physical model for the speed of the 'thermal bar', based on negligible horizontal advection and diffusion of heat, gave reasonable values for both the laboratory model and Lake Ontario. Observations were also made of the associated velocity field. On the basis of this laboratory model, which suggests that horizontal advection and diffusion of heat were not of primary importance, mathematical models were developed. First the temperature field was calculated from the one-dimensional heat diffusion equation. Then the velocity field was calculated assuming that the flow was driven by buoyancy forces and balanced by viscous forces. On the basis of the similitude between the temperature fields found in my models and those observed in the lakes, it seems possible that the velocity field of the models also provides a good approximation to the circulation associated with the bar in lakes. There are no direct measurements of the velocities associated with the bar in lakes and they will be difficult to obtain as such velocities are expected, in Lake Ontario, to be only of the order of 1 cm sec⁻¹. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

This study consisted in part of general observations of the biology of four species of waterstrider (Gerris buenoi, incurvatus, notabilis, and remiges), in Marion Lake, B.C, and in part of an experimental manipulation of density and food supply in replicated populations of penned G. notabilis. Gerrids have a generation time of one year; adults overwinter, lay their eggs in the spring, and then die; nymphs become adults in about two months. In the natural population storms and food shortage probably caused the greatest mortality. In the penned populations survival of nymphs was inversely proportional to spring density of adults, and directly proportional to food supply. In low density pens fewer nymphs hatched but relatively more survived; in high density pens more nymphs hatched but relatively fewer survived; thus fall numbers were much the same (within food treatments) regardless of initial density. Increased density also lowered survival of adults in both food treatments, and, in turn, low adult survival enhanced the expectation of survival of nymphs, in the unfed pens only. However these effects were unimportant compared with the direct effects of density and food on nymph survival. Most of the nymphs died during the first stadium, probably owing to cannibalism by older nymphs and parents in the fed pens, and to both starvation and cannibalism in the unfed pens. In view of the fluctuating food supply to which gerrids are subject, their opportunistic method of feeding and concomitant cannibalistic behaviour is probably of selective advantage to the individual, as well as being a potential population regulating mechanism. / Science, Faculty of / Zoology, Department of / Graduate

Drainable porosity as a function of water table was investigated to replace the common practice of treating it as a constant A continuous function in the form of a negative exponential equation relating drainable porosity to water table depth was developed by three methods: (1) laboratory core-sample analysis; (2) rainfall rate and water table depth analysis; (3) drainage rate and water table depth analysis. Furthermore, this function was derived for four different water table regimes: (1) subsurface drainage; (2) low subirrigation and subsurface drainage; (3) high subirrigation and subsurface drainage; (4) no drainage and no subirrigation. The drainable porosity function was incorporated into a water balance model which simulated the soil moisture profile and the water table depth on a daily basis. Major modification of the previous model was the elimination of separate falling and rising water table equations since discrete porosity values were no longer assigned to particular soil depth intervals. A subroutine program which computed the total maximum transient storage and the transient storages to each of the four successive soil zones was also incorporated. The 'maximum drainable porosity' and the 'rate constant' parameters in the negative exponential equation were found to be different among the three methods of analysis and among the four water table regimes. Good agreement between simulated and actual water table depths of each regime for 1984 and 1985 was found. The modified water balance model could be used to generate different water table depths by changing the input parameter of design drainage rate. From these outputs, a appropriate drainage rate which gives the desired water table depth could be selected for the purpose of horizontal subsurface drainage system design. / Applied Science, Faculty of / Graduate

This thesis describes a study of two approaches to the design of water distribution networks to meet specified demands at minimum cost. One method is based on an incremental increase technique which first examines all possible "one-size" pipe increases in the network, then based on a benefit/cost analysis a decision is made on which pipe to increase one diameter size. The second approach utilizes a computerized linear programming technique to rapidly converge on an optimal network design. Both techniques rely on the use of an effective computerized network analysis program. It was found after studying several networks that the incremental increase technique is operational for any size of network. However, computer costs quickly become a limiting factor in the usefulness of this approach. The linear programming based technique was considerably less costly but did not prove itself to be fully capable of optimizing large networks in its present developmental state. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

The water potential concept and generalized Darcy's law for unsaturated flow were proposed as a basis for the study of the energy state and flow of water in wood at high moisture contents. A series of experiments was conducted to investigate wood properties that are crucial to the application of these theories. Much attention was devoted to the measurement of the moisture content-matric potential (M-Ψm) relationship by the porous plate methods. Both the boundary drainage and imbibition curves and the drainage curve starting from the green condition were determined. In addition, independent Ψm measurements were made in some of the specimens equilibrated on the porous plates using Wescor PT51-10 thermocouple psychrometers (TCP). The osmotic potential was then assumed to be negligible. Transient flow experiments were also conducted for determining the water conductivity (K) as a function of both M and Ψm, and the water diffusivity (D) as a function of M using an instantaneous profile method and the one-step method. The boundary drainage and imbibition curves for the longitudinal direction of flow were thus obtained. The saturated conductivity had to be measured separately. Western hemlock sapwood was used for all determinations which were made at a temperature of 21°C. The results of the porous plate tests confirmed the presence of a considerable hysteresis in the M-Ψm relationship at high moisture contents, with M at a given Ψm greater in drainage than in imbibition. The ink-bottle effect appears to be the primary cause of this phenomenon. Both types of drainage curves obtained showed a tendency to exhibit a plateau at intermediate M's and were found highly dependent on the initial moisture content. A fairly good agreement was found between the Ψm values imposed on the specimens on the porous plates and those measured by the TCP's for the Ψm range from -1 to -7 bars in drainage. These two types of data differed markedly at lower Ψm 's in drainage and in imbibition. However, the differences observed in imbibition were readily explainable and the results of the TCP tests clearly demonstrated the strong hysteretic behavior of the M-Ψm relationship in the wet state. The reproducibility of the TCP method during the Ψm measurements in wood was rather poor. The K-M, K- Ψm, and D-M curves obtained by the two transient methods used were very similar in shape. The K(M) function exhibited a considerable hysteresis with K at a given M greater in imbibition than in drainage. A change in K of several orders of magnitude was recorded near full saturation. The K(Ψm) and D(M) functions displayed only a partial hysteresis. Disproportionality between flux and gradient was observed in imbibition above 75% M. The non-uniqueness of the M- Ψm relationship with respect to the state of flow was apparently the main cause of this anomaly. / Land and Food Systems, Faculty of / Graduate

Part I of this thesis develops a theory of nonlinear resonant interactions between continental shelf waves. From the inviscid, unforced long-wave equations for a rotating, homogeneous fluid, it is shown that resonant interactions between three continental shelf waves can occur. Evolution equations governing the amplitude and the energy of individual waves in a resonant triad are derived. The nonlinearity in the governing equations allows energy to be transferred between the waves, but with the total energy conserved. In particular, interactions on an exponential shelf are studied. Part II of this thesis compares the theory from Part I with observations and data from the Oregon shelf. Rotary spectral analysis and cross-shelf modal fitting are the two techniques used for shelf wave detection. Many features characteristic of shelf waves and of the resonant triad interaction theory are found in the current and sea level data. Also, for the first time, shelf waves have been unambiguously identified in both the alongshore and cross-shelf dimensions. The data indicate that the wind generates long continental shelf waves at low frequencies. Nonlinear resonant interactions then transfer energy from the low-frequency long waves to higher frequency shelf waves with much shorter wavelengths. The good agreement between theory and observation suggests that nonlinear energy transfer may play a significant role in shelf wave dynamics. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

Filamentous bulking in nutrient (N & P) removal activated sludge systems is a problem of considerable magnitude - three quarters of 45 plants surveyed were found to have bulking sludges to the extent that sludge settleability (DSVI) was adversely affected. If filamentous organism proliferation could be controlled and thereby sludge settleability improved to below DSVI of 100 ml/g, then with provision for factors such as additional aeration capacity, between 50% and 7 5% more wastewater could be treated in existing nutrient removing activated sludge plants. Anoxic-aerobic (AA) or low F/M filaments appear to proliferate in activated sludge plants that incorporate biological nitrogen removal. From earlier research, Casey et al. (1992a) showed that the cause for AA filament proliferation lay in the denitrification behaviour of the N removal systems. They hypothesized that filamentous and floe-forming organisms have different denitrification behaviour - the former reducing nitrate only as far as nitrite whereas the latter reducing nitrate all the way to nitrogen gas via the denitrification intermediates nitrite, nitric oxide (NO) and nitrous oxide (N₂O). If nitrate and nitrite removal to nitrogen gas is not complete in the anoxic reactor, then, when conditions become aerobic, the accumulated denitrification intermediates, in particular NO, inhibit oxygen uptake in the floc-formers. The filaments do not experience this inhibition because by reducing nitrate only to nitrite, no denitrification intermediates accumulate in their cytoplasmic membrane and consequently they can successfully compete against the floe-formers and proliferate in the N removal systems. If denitrification is complete, no residual intracellular denitrification intermediates remain in the floc-formers. Therefore, when conditions become aerobic, the floc-formers are not inhibited in their oxygen uptake and can successfully compete against the filamentous organisms which cause the bulking.

Bertha N. Langley / Typescript / M.S. Florida State College for Women 1914 / Includes bibliographical references

Since 1989 a wide ranging program of research has been under way to identify the factors that effect low F/M filament proliferation. Completed work has established an important factor conducive to low F /M filament proliferation - the presence of anoxic and aerobic zones, or, alternating anoxic-aerobic conditions in a system. It was also established that the presence or absence of readily biodegradable COD (RBCOD) or slowly biodegradable COD (SBCOD) were not deciding factors in their proliferation. The research presented in this thesis focuses on the effects of; • sludge age, • magnitude of the aerobic mass fraction, • magnitude of the nitrate concentration during the anoxic period, on the low F /M filaments. The experimental set-up consisted of two intermittently. aerated anoxic-aerobic (20 minute cycles, peak DO 2 to 2,5 mgO/l), single reactor completely mixed continuously fed systems. The experimental investigation was chronologically divided into 3 phases and examined the effect of the following conditions on the low F/M filaments.

In South Africa, it is a legislative requirement that all water supply points be metered (van Zyl, 2011). Conventional meters are mostly used as the main means of monitoring water consumption by South African municipalities. In the last two decades, the water metering industry has seen substantial developments with new capabilities added to the conventional water meter, known as advanced meters. These advanced water meters have capability of processing, storing and communicating data without the need of human intervention. As such they come with desirable capabilities for both consumers and municipalities. These include prepaid meters which are special type of advanced water metering technology that is mostly applicable in the low income areas of South Africa. However, advanced water meters have significant drawbacks, such as higher failure rates (due to electronics, batteries and more components), higher purchase and maintenance costs and susceptibility to tampering. It is therefore necessary to make a conscious and informed consideration when deciding on which metering technology to implement for different users. This could be achieved through having a technology evaluation framework. The goal of this research was to develop an evaluation framework to help municipalities in the selection of appropriate advanced water metering technologies for application in low income communities. This goal was achieved through: determining the range of functionality of technologies both available and under development for advanced water metering; documenting case studies of both successful and failed implementation of advanced water meters, including social perception and impacts; developing an evaluation framework that can evaluate advanced water metering; and evaluating on technical, social, economic and environmental grounds. The results from literature and case studies indicate that in low income communities, advanced water metering is mainly implemented for cost recovery purposes. However, some municipalities implement advanced metering schemes for water management and debt recovery. The most advanced water metering technology being installed in low income communities is prepaid meters. Prepaid meters have a potential to fulfill all the range of objectives that municipalities install advanced metering technology for. This technology is found to have high maintenance requirements due to high failure rate. For successful implementation, it is important that municipalities have adequate budget for repairs and maintenance or seek technical support from manufacturers.