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The impact of septic tank effluent disposal on groundwater quality was investigated at Oxford. The Oxford township can be regarded as typical of many small communities on the Canterbury Plains which have a high density of septic systems serviced by soakage pit drainage. The primary concern with grouped septic systems is the potential for both chemical and microbial groundwater contamination. The alluvial gravel aquifers of the Canterbury Plains are especially susceptible to microbial contamination due to the high rates of groundwater flow which may transport both bacteria and viral contaminants over large distances. Geological investigations established the presence of an areally extensive, tuff derived, clay unit which forms an aquitard beneath the unconfined aquifer in the north of the Oxford area. Recharge of the unconfined aquifer above the clay unit is exclusively from rainfall infiltration while to the south, groundwater levels respond to rainfall infiltration and influent seepage from the Eyre River. The presence of two hydrogeologically distinct gravel units within the unconfined aquifer was determined by application of the column dilution technique. Point dilution tests showed the average groundwater velocity of 130 m/day in the upper gravel unit to be significantly higher than the 40 m/day measured in the underlying gravels. The presence of discrete channels of preferred flow within the unconfined aquifer system was also established by point dilution tests, intrachannel velocities ranging from 210 to 400 m/day. A resistivity salt tracing test indicated groundwater flow in an easterly direction with a velocity of 250 m/day through an observed channel feature. Groundwater quality monitoring showed a significant degree of groundwater contamination close to the Oxford township. Concentrations of faecal coliform bacteria in excess of drinking water standards were detected up to 900 m downgradient of the nearest septic tank. Elevated levels of chemical indicators (N03-N, CL-) were also detected in all monitoring wells. The pattern of groundwater contamination was complex, reflecting both the heterogeneity of groundwater flow through the unconfined aquifer system and the influence of monitoring well location. Predictive modelling indicated the potential for the transport of faecal coliform bacteria up to 2.6 km downgradient of Oxford. Modelling also suggested increased urban development within Oxford to have a relatively minor effect on the overall extent of groundwater contamination. Additional hydrogeological and water quality data, aided by the application of numerical solute transport modelling techniques, may provide a more accurate estimate of the impact of septic tank effluent disposal on groundwater quality. Future sewage disposal options for Oxford have to balance the low potential for microbial contamination of drinking water supplies outside the groundwater zone delineated by this study, against the environmental acceptability continuing contamination of this zone. This study has identified the need for further research into the effects of septic tank effluent discharge on groundwater quality in the Canterbury region, to provide a sound base for future resource management decisions.

It is a widespread belief in western society today that every adolescent is capable of attaining a high school diploma (Pharris-Ciureja, Hirschman, & Willhoft, 2012). In reality, a Statistics Canada (2012) “Labour Force Survey” concluded that only 73.9% of all 18 and 19 year olds have received high school diplomas. Richards (2009) stated that Manitoba’s high school dropout rate is the highest in Canada, and is twice as high as that of British Columbia. Unfortunately, many adolescents have started on the path to dropping out long before they enter high school (Downing & Peckham-Hardin, 2007) due to a combination of sociological, socioeconomic, cultural, developmental, behavioural, and academic factors (Englund, Edgeland, & Collins, 2008; Pharris-Ciureja, Hirschman, & Willhoft, 2012; Richards 2009). To better understand this phenomenon, I used the critical analytical tool of the immanent critique (Skrtic, 1995); and several different critical thinking tools (Levy, 2010). I also reviewed literature concerning sociology and education, Manitoba’s interpretation of inclusion, and the unique nature of high schools and their teachers. The purpose of this study was to invite Manitoba high school classroom teachers into a think tank and ask them what they believe they do to help adolescents stay in school and graduate. I found that the high school classroom teachers who participated in the study creatively strived to connect with students, worked individually and collaboratively with colleagues, and acknowledged the need for legislation, policies, and administration. They also took the time to examine current educational practices and continuously searched for innovative ways to improve their classrooms, schools, and the system-at-large. I concluded that school systems would greatly benefit from seeking out the voices of high school teachers and asking them what they think.

Sloshing phenomena could seriously damage tank structures and reduce its lifetime. On the one hand, studies directly recommend the use of baffles to solve these problems, nevertheless on the other hand the existence of small tanks or plastic tanks without baffles confuse and complicate the case. The first aim in this thesis is to clarify the necessity of baffles for a particular diesel tank L120 H-Generation in Volvo front loaders. Then, the second aim is to improve the existing design. Four configurations are proposed and checked independently. Experiments in the lab, FEM static stresses analyses and vibrational simulations are done in order to fulfill the requirements. The conclusion of this thesis is that the dissipation of energy is highly recommended, so having an oblique baffle with holes could be a good way to reduce the sloshing and extend the lifetime of the tank.

Natural convection with high cooling effects is of increasing interest in cold region geotechnical engineering. To study natural air convection in a highly-permeable porous medium, convective and conductive heat transfer experiments were carried out using an insulated cylindrical tank filled with styrofoam chips. Convection and conduction were caused by controlling the temperatures at the top and bottom of the tank, and a series of cross-sectional conductive and convective isotherms were generated from collected temperature data. Additional convective patterns were obtained from tests by centrally localized heating below or cooling above. Flow velocities were measured at the center of the tank. Results showed that convective heat transfer rate was higher than thermal conduction. Convective isothermal patterns varied with various boundary conditions and could be influenced by small temperature perturbation. Given appropriate environmental conditions, efficient convective cooling effects can be used to enhance ground freezing or to protect permafrost from degradation. / Geotechnical Engineering

Abstract This research is concerned with exploring, describing and interpreting the potential of community participation in improving food security in rural households in the Kolonna area. It explores the importance and value of the ancient village tank system as a vehicle for enhancing both community participation and food security. In Sri Lanka there still exists a network of large and small irrigation tanks and associated distribution and drainage channels that was originally established 1000-2000 years ago. This system apparently formed the basis of an effective cooperative social system that endured for centuries. More recently, several centuries of colonial rule caused the abolition of this participatory system by the British and the social structure and tank system of the village collapsed. Since independence in 1948, several government departments and international institutions have been trying to rebuild this social structure around the village tank, but with only limited success. This thesis describes efforts to document the potential for incorporating historical knowledge and farmers’ perceptions into sustainable community participatory programs in agricultural activities based on village tanks, with the aim of improving food security in a rural area of Sri Lanka. A mixed methods approach was employed to address the research questions identified for the study. It involved predominantly qualitative methodology including focus groups and individual interviews with a range of stakeholders including government and spiritual authorities allowed the exploration of the realities of village life and issues affecting food security. Significant findings not evident in typical governmental statistical reports include the following: (1) Household food security in rural areas is still a major problem. Agricultural production rather than purchased food is the main source for caloric intake of rural households and many farmers experience food insecurity due to unexpected seasonal crop failures. Furthermore, almost 10% of the residents of Kolonna area experience acute food insecurity, which occurs due to poverty. These people typically do not have secure access to land for growing their own crops but rely on casual wages work. (2) The major constraint to food security identified by respondents was lack of consistently available and equitably distributed irrigation water, although in contrast occasional flood damages to land and crops s due to flood was also a significant problem. Some farmers also believed that marketing and distribution channel constraints limited their commercial returns and income, and capacity to enjoy year-round food security. v (3) Despite the existence of several community participatory programs in the Kolonna area, they are not perceived to be successful. Only one third of the villagers are involved in these programs and more than 40% were unaware of their existence. Major criticisms included the perception of political interference and favoritism in the process governing their operations, which favored relatively few recipients. . (4) There appears to be strong support amongst villagers for revision of cooperative approaches such that management is by representatively elected independent committee that allow involvement of the most suitable farmers. This perception was linked to beliefs that a renewed focus on the village tank would be ultimately more beneficial than focusing solely on improving food security, because of the capacity to incorporate traditional community participatory approaches. Valuable features of the traditional system include sharing rather than hiring labor, dividing communal tasks among community members, and rules and regulations imposed by a recognized and accepted governing body. The implications of these findings for further research, policy and practice are discussed.

On-site sewage systems, such as septic tank-absorption trenches, are used by approximately 20 000 people who live within the catchments that supply Sydney??s drinking water. These systems discharge sewage, treated to varying degrees depending on the system type and level of maintenance, to the environment. This can result in contamination of drinking water supplies if systems are not designed or managed appropriately. The aim of the project was to develop a methodology to define appropriate buffer distances between on-site sewage systems and waterways in Sydney??s drinking water catchments, to ensure the protection of drinking water quality. Specific objectives included: identifying the current status of on-site sewage management; assessing the effluent quality and treatment performance of septic tanks, aerated wastewater treatment systems (AWTS) with disinfection and an amended material sand mound; and development of an appropriate methodology for delineating buffer distances and assessing development applications. Viruses were used as a focus for delineating the buffer distances due to their mobility and robustness in the environment, and the potential health consequences of their presence in drinking water. A Quantitative Microbial Risk Assessment (QMRA) model was developed to calculate the cumulative impact of the on-site sewage systems in the Warragamba catchment based on data from literature and experiments, with consideration of virus loads from sewage treatment plants within the catchments. The model enabled consideration of what was a tolerable impact in terms of the resulting infections within the community. The QMRA the tolerable loads of viruses from the Warragamba catchment were 108 viruses per year in raw water and 104 viruses per year in treated water. A log reduction method was developed to facilitate individual site development assessments. This method was compared to other management approaches to development assessment: fixed minimum buffer distances of 100m, reducing failure rates to zero, and the use of a preferred system. Each of these methods had a limit for how much they could reduce virus loads to the catchment due to either failure or short buffer distances at some sites. While the log reduction method is limited by the failure rates, the method provides a quantitative measure of risk by which maintenance inspections can be prioritised.

The prediction of the expected long-term performance of concrete exposed to sewage and similar materials can be difficult as it is affected by a large number of parameters. In addition, the deterioration process in concrete is generally slow. The focus of the study was to ascertain the life expectancy of concrete septic tanks located in rural Victoria. In developing the accelerated test method, ASTM C 192, ASTM C 452, ASTM C 1293 and ASTM C 109 standard procedures were adopted wherever possible. From the analysis of mass change data after 350 days, it was found that the mass change rate for concrete in sulphate solutions increases with the increase of concentration of Na2SO4 solution. The weights of the samples in Na2SO4 solution increased with time, whereas the control specimens lost weight as a result of heating cycles. The probable reason for weight increase in Na2SO4 solution was hypothesized as the formation of gypsum (CaSO4.2H2O) and ettringite (3CaO.Al2O.3CaSO4.32H2O), which is confirmed from microstructural analysis. The rate of weight gain was higher at the beginning and reduced with time. The stronger the concentration of Na2SO4 the stronger was the weight gain or expansion of mass. All the samples in sulphate solutions attained their maximum weight at around 250 days. For the specimens in sulphuric acid solutions weight loss was observed to be higher for higher concentrations. The lower the pH of the acidic solutions, the larger was the weight loss. The weight loss of specimens in acidic solutions exceeded the control specimen after 250 days. The reason for the loss of weight of the samples in sulphuric acid may be the decalcification of C-S-H gel within the concrete, and as a consequence the loss of cementitious structure. Comparison of the corrosion of concrete and also microstructural examination of field samples confirmed that the deterioration mechanism is similar to that observed in the laboratory. The accelerated testing adopted here offers a realistic method of predicting the deterioration of septic tanks under biogenic sulphuric acid corrosion. Two equations have been proposed to predict deterioration due to sulphate attack and sulphuric acid attack as mass loss (or gain) with time.

Research Doctorate - Doctor of Philosophy (PhD) / This thesis describes a study in which the aim was to develop an improved method for computational fluid dynamics (CFD) modelling of gas-liquid flow in mechanically-stirred tanks. Stirred tanks are commonly used in the process industries for carrying out a wide range of mixing operations and chemical reactions, yet considerable uncertainties remain in design and scale-up procedures. Computational modelling is of interest since it may assist in investigating the detailed flow characteristics of stirred tanks. However, as shown by a review of the literature, a range of limitations have been evident in previously published modelling methods. In the development of the modelling method, single-phase liquid flow was firstly considered, as a basis for extension to multiphase flow. A finite volume method was used to solve the equations for conservation of mass and momentum, in conjunction with the k-epsilon turbulence model. Simulation results were compared with experimental measurements for tanks stirred by a Rushton turbine and by a Lightnin A315 impeller. Comparison was made between different methods which account for impeller motion. Accuracy was assessed in terms of the prediction of velocities, power and flow numbers, the presence of trailing vortices, pressures around the impeller, and the turbulent kinetic energy and dissipation rate. The effect of grid density was investigated. For gas dispersion in a liquid, the modelling method employed the Eulerian-Eulerian two-fluid equations, again in conjunction with the k-espilon turbulence model. The correct specification of the equations was firstly reviewed. Different forms of the turbulent dispersion force were compared. For the drag force, it was found that existing correlations did not properly account for the effect of turbulence in increasing the bubble drag coefficient. By analysing literature data, a new equation was proposed to account for this increase in drag. For the prediction of bubble size, a bubble number density equation was introduced, which takes into account the effects of break-up and coalescence. The modelling method also allows for gas cavity formation behind impeller blades. Simulations of gas-liquid flow were again carried out for tanks stirred by a Rushton turbine and by a Lightnin A315 impeller. Again, the impeller geometry was included explicitly. A series of simulations were carried out to test the individual effects of various alternative modelling options. With the final method, based on developments in this study, simulation results show reasonable overall agreement in comparison with experimental data for bubble size, gas volume fraction, overall gas holdup and gassed power draw. In comparison to results based on previously published modelling methods, a significant improvement has been demonstrated. However, a number of limitations have been identified in the modelling method, which can be attributed either to the practical limitations on computer resources, or to a lack of understanding of the underlying physics. Recommendations have been made regarding investigations which could assist with further improvement of the CFD modelling method.

Zugl.: Rostock, Univ., Diss., 2007