Philosophiae Doctor - PhD / The disposal of brine effluent from inland wastewater desalination plants is a growing global problem with adverse economic and environmental implications because of the substantial cost associated with its disposal and the potential for polluting groundwater resources. Currently, the best and most economical option for brine disposal from inland desalination plants is the use of evaporation ponds, which concentrate the liquid until getting a solid waste that can be valued or directly managed by an authorized company. The effectiveness of these ponds is therefore dependent on the evaporation rate, which has previously been improved by the addition of dyes such as methylene blue. However, the addition of chemical dyes to the evaporation ponds poses a threat to the environment, wildlife, and humans.

It is evident that the sea ice cycle, from its formation to its melt, is governed by a complex interaction of the ocean, atmosphere and surrounding continents. Once sea water begins to freeze, physical, biological and chemical processes have implications on the evolution of the sea ice morphology [38]. The distinguishing factor between fresh and sea water ice is brine inclusions that get trapped within the ice pores during freezing. Salt inclusions within frozen ice influence the salinity as well as the physical properties of the sea ice [23]. These brine inclusions form part of a dynamic process within the ice characterized by the movement of brine and phase transition which are the foundation of many of its physical properties [23]. Brine removal subsequently begins to occur due to vertical gravity drainage into the underlying ocean water. This study introduces the application of a biphasic model based on the Theory of Porous Media (TPM) which considers a solid phase for the pore structure of the ice matrix as well as a liquid phase for the brine inclusions, respectively. This work explores the use of the TPM framework towards advancing the description and study of the various desalination mechanisms that are significant in aiding the salt flux into the Southern Ocean. This will foster understanding of brine rejection and how it is linked to the porous microstructure of Antarctic sea ice

No description available.

Listeria monocytogenes is the major pathogen in ready-to-eat meat products such as deli meats and frankfurters. Contamination can occur via the salt brines that are used to cool thermally processed meats. Both L. monocytogenes and lactic acid bacteria can grow and thrive under these brine conditions, and may become competitive with each other for available nutrients. The objective of this study was to determine the effect of a three strain cocktail of lactic acid bacteria Enterococcus faecalis, Carnobacterium gallinarum, and Lactobacillus plantarum on the survival of Listeria monocytogenes and Listeria innocua in brines stored under low temperatures up to 10 days. Three brine concentrations (0%, 7.9%, and 13.2% NaCl) were inoculated with ~7.0 log₁₀ cfu/ml of one of five cocktails (L. monocytogenes, L. innocua, lactic acid bacteria (LAB), L. monocytogenes + LAB, or L. innocua + LAB) and stored for 10 days at either 4°C or 12°C. Three replications of each brine/cocktail/temperature combination were performed. No reductions of L. monocytogenes were seen in 7.9 or 13.2% NaCl with LAB; however, reductions of L. monocytogenes were seen in the 0% NaCl with LAB (1.43 log at 4°C and 3.02 log at 12°C). Listeria innocua was significantly less resilient to environmental stresses than L. monocytogenes, both with and without LAB present (p<0.05). This research indicates these strains of lactic acid bacteria are not effective at reducing L. monocytogenes in brines at low temperatures. Furthermore, the use of L. innocua as a model for L. monocytogenes is not appropriate under these environmental conditions. / Master of Science

Anomalously high groundwater salinities exist within the syn-impact sediment of the Chesapeake Bay impact crater, including an unexplained brine. This brine may be the result of phase-separation of seawater that occurred within the syn-impact sediments as underlying deformed and possibly melted basement rock cooled following impact. The 85 km wide crater has been described as a complex peak-ring crater; created 35.8 million years ago in the then submerged unconsolidated sediments of the Atlantic Coastal Plain and now completely buried by post-impact sediments. An annular trough with relatively undisturbed basement surrounds a ~38 km diameter inner basin with a peak ring and central uplift. The basement surface within the inner basin was modified by the impact and is projected to be approximately 1.6 km below sea level. Geothermometry and advective and conductive heat flow modeling was performed to characterize a possible post-impact hydrothermal system. Thermal maturity and radiogenic techniques were used to estimate the temperature history of the crater sediments. Core samples from one borehole just outside the crater, two within the annular trough, and one shallow borehole within the inner basin were examined. Numerical heat and fluid flow models were developed using a range of likely sediment parameters and basal heat flow values to determine if phase-separation temperatures were likely to have occurred, and to evaluate what affect, if any, lithostatic overpressures may have had on post-impact cooling. Geothermometry results indicate that no detectable thermal anomaly exists within the syn or post-impact sediments at these boreholes; however, no data are available within the deep inner basin where temperatures were likely to have been higher. Samples from existing boreholes suggest that sediment are organically immature and likely were never heated above ~40°C for a geologically significant period of time. These results support apatite He (U/Th) and previously published apatite fission track radiogenic ages indicating no Cenozoic resetting. Heat flow simulations indicate that a high temperature (>400°C) hydrothermal system could have existed within the inner basin and not caused any measurable effect on thermal maturity in the annular trough and shallow portion of the inner basin. Results also indicate that phase-separation could have occurred in the syn-impact sediments using reasonable estimates of basal heat flow, permeability, thermal conductivity, and porosity values, and that overpressures resulting from rapid deposition of syn-impact sediments dissipate within a few thousand years and are not an important heat transport mechanism. / Master of Science

>Magister Scientiae - MSc / Chemical speciation and the evaluation of species distribution is the key to understanding the potential of brines to form scale or corrode the water circuit as well as the potential of mobility and release trends of the pollutants into the environment. It is important to identify highly soluble free ions in water chemistry because toxicity of ions is related to mobility and consequently bioavailability. The chemical composition, character and chemical speciation modelling of saline effluents (brines) at Tutuka Power Station and Sasol Synthetic Fuels Complex in Secunda were studied. The form in which chemical species exist (chemical speciation) and the physical and chemical interactions of species in saline effluents at these two study sites is not fully understood. This study investigated how pH, temperature, alkalinity and chemical composition influenced chemical speciation, species distribution, scale forming and corrosion potentials of the different saline effluent streams at the two sites using computer programs PHREEQC and Aq.QA. Characterizations of the results were presented in Stiff and Piper diagrams generated by the Aq.QA computer software. Chemical speciation modelling of the brines showed that scale-forming minerals aragonite, calcite, hematite, anhydrite and gypsum have positive saturation indices between 0 and 20 in mine water, RO brine at Tutuka and Sasol Secunda, EDR brine at Sasol Secunda and VC brine at Tutuka Power Station. The water types at Tutuka Power Station were found to be mainly Na-S04 water types and those at Sasol Secunda were a mixture of Na-Cl and Na-S04 water types. Water treatment chemicals playa major role in increase were absent in the intake water. It was found that Sasol Secunda water streams are much more heavily contaminated than Tutuka water streams. The study also found that the mine water utilised at Sasol Secunda is two-fold more polluted than the mine water utilised at Tutuka although these sites are a mere 40 km apart. The sodium adsorption ratios showed that all the saline effluent streams at Tutuka and Sasol Secunda were unsuitable for irrigation, except for desalination product waters. Chemical speciation showed that the predominant species in the most concentrated saline effluent (VC brine) at Tutuka were the free cr ion at approximately 100 % with very minute quantities of FeCI+ and ZnCI+ and the predominant sodium species were the free Na+ ion which existed at 85 %. Magnesium species had the predominant form as the ionic compound MgS04 at 73 % and the carbonates were mainly in the form of NaC03- (53 %), HC03- (28 %) and CO{(7 %). The most concentrated brine analysed at Sasol Secunda was the TRO brine. PHREEQC did not predict the precipitation of CaC03 from the TRO brine at Sasol Secunda. The most abundant calcium species were Ca2+(59 %) ions and CaS04 (40 %). The brine was at a pH of 5.76 with dissolved CO2 at 73 % of the carbonate species. Trace elements were evaluated and the toxic trace elements varied from 0.07 mg/L (As) to 26.75 mg/L (Sr) at Sasol Secunda. At Tutuka Power Station the toxic trace elements in brines varied from 0.02 mg/L (As/Se) to 16.85 mg/L (Sr). Sr and B were found to be the most highly concentrated toxic elements. The major and trace ion chemistry, alkalinity, pH, sodium adsorption ratios, change in concentration of the water streams and the brine chemical composition after contact with ash was also evaluated. When saline effluents at Tutuka Power Station and Sasol Secunda are combined with ash, pH, Ca content and alkalinity of the resulting solution increased. The chemical composition of saline effluents can be influenced by the ingress of CO2 from the atmosphere. The study shows conclusively that brine composition and concentration is highly variable at these South African power utilities and processes such as RO, contact with ash and C02 ingress can have an impact upon the overall brine quality. Aq.QA was found to be a more accurate tool for classifying waters according to dominant ions than Stiff diagrams but Stiff diagrams still have the superior advantage of being a mapping tool to easily identify samples of similar composition as well as quickly identify what has been added or what has been removed from a water stream. Chemical speciation could identify effluent streams where C02 dissolution had taken place.

Inclined negatively buoyant jets are commonly used to dispose brine effluent produced by desalination plants. Desalination and associated research has expanded in recent years due to the continued depletion and degradation of natural potable water sources. Desalination plants are the preferred option for meeting water demand deficits in many countries around the world. Inclined negatively buoyant jets are produced when the brine is discharged at an upward inclined angle via an offshore pipeline and diffuser system. Previous experimental studies have focused on the rapid mixing and dilution achieved by these discharges, as well as geometric parameters. Dilution measurements between these experimental studies vary significantly, which is possibly due to variations in the location of a lower boundary on observed flow behaviour. In the present study, velocity field information is experimentally measured for inclined negatively buoyant jets and compared to integral model predictions. Experiments are conducted with and without a lower boundary influencing observed flow behaviour, thus allowing the effects of a lower boundary to be determined. The particle tracking velocimetry experimental technique is employed to measure near field velocities of these discharges. Firstly, discharges with source angles between 15\degree and 75\degree are investigated without boundary influence in stationary ambient conditions. The source was a minimum of 655 mm above the bottom of the experimental tank to ensure there was no lower boundary influence on observed behaviour. Time-averaged and fluctuating data are extracted along the trajectory of discharges. All non-dimensionalised geometric and centreline velocity parameters are found to collapse. Empirical coefficients are compared to previous experimental studies and integral model predictions. A new detrainment model is developed to predict the behaviour of inclined negatively buoyant jets without boundary influence. The model further develops recent attempts to allow for buoyancy flux reduction along the flow path. The reduction in buoyancy flux is dependent on the local parameters of the flow and simulates experimentally observed detrainment. Dilution, geometric, and velocity predictions are found to be improved over previous models when compared to experimental data. Finally, a raised platform was placed inside the experimental tank to determine the influence of a lower boundary on inclined negatively buoyant jets. Source angles of 30\degree, 45\degree, and 60\degree are investigated at three different non-dimensional source heights. The lower boundary is horizontal and ambient conditions are again stationary. Discharges impinge the lower boundary before forming a radially spreading layer along the boundary. Geometric and velocity data are compared to the first set of experiments in this study to determine the influence of the lower boundary on observed flow behaviour. Empirical coefficients at maximum height are similar with and without the influence of the boundary, whereas coefficients are substantially influenced at the return point when the boundary is present.

Throughout the arid and semi-arid regions, researchers have been looking at different ways to deal with the salinity problem of the soil and water as well as feed for the livestock. Study 1 focused on a pilot project conducted in an irrigation district in Marana, AZ, USA, looking at using Reverse Osmosis (RO) concentrate on Atriplex lentiformis (quailbush) and then harvesting the plant to be tested for its possible use as a supplement in feed for livestock. Three irrigation treatments were tested based on the potential evapotranspiration rate (ET(o)): (1) plots irrigated at ET(o) adjusted daily via an on-site micrometeorology station; (2) plots irrigated at 1.5 ET(o) adjusted daily; (3) plots irrigated at a constant rate throughout the year based on the mean of annual ET(o). The plants produced 15-24 tons ha⁻¹ year⁻¹ of biomass and could be irrigated at the rate of ET(o), ca. 2 m yr⁻¹ at this location. It was concluded that irrigation of halophyte forage crops provide a viable strategy for extending water supplies and disposing of saline water in arid-zone irrigation districts. Study 2 focused on a field data from Study 1 and two greenhouse experiments. The greenhouse experiments were conducted in 2007 and 2010. The 2010 greenhouse trials, under well-watered conditions, showed that the apparent zero-point-salinity for yield was 47.3 g L⁻¹ TDS. An additional greenhouse experiment was conducted in which plants in sealed pots were grown to the wilting point on a single application of water. The experiment was conducted at different salinities to see if salinity and water stress were additive factors in reducing yield and Water Use Efficiency (WUE). To the contrary, yield and WUE actually increased as a function of salinity, perhaps due to conversion from C3 to C4 photosynthesis over the salinity range (noted in other studies with A. lentiformis). We conclude that xerohalophytes such as A. lentiformis could greatly extend the useful range of salinities under which forage crops can be grown in arid-zone irrigation districts.

Carbon dioxide (CO2) sequestration is defined as the removal of gas that would be emitted into the atmosphere and its subsequent storage in a safe, sound place. CO2 sequestration in underground formations is currently being considered to reduce the amount of CO2 emitted into the atmosphere. However, a better understanding of the chemical and physical interactions between CO2, water, and formation rock is necessary before sequestration. These interactions can be evaluated by the change in mineral content in the water before and after injection, or from the change in well injectivity during CO2 injection. It may affect the permeability positively due to rock dissolution, or negatively due to precipitation. Several physical and chemical processes cover the CO2 injection operations; multiphase flow in porous media is represented by the flow of the brine and CO2, solute transportation is represented by CO2 dissolution in the brine forming weak carbonic acid, dissolution-deposition kinetics can be seen in the rock dissolution by the carbonic acid and the deposition of the reaction products, hydrodynamic instabilities due to displacement of less viscous brine with more viscous CO2 (viscous fingering), capillary effects and upward movement of CO2 due to gravity effect. The objective of the proposed work is to correlate the formation damage to the other variables, i.e. pressure, temperature, formation rock type, rock porosity, water composition, sulfates concentration in the water, CO2 volume injected, water volume injected, CO2 to water volumetric ratio, CO2 injection rate, and water injection rate. In order to achieve the proposed objective, lab experiments will be conducted on different rock types (carbonates, limestone and dolomite, and sandstone) under pressure and temperature that simulate the field conditions. CO2 will be used at the supercritical phase and different CO2-water-rock chemical interactions will be addressed. Quantitative analysis of the experimental results using a geochemical simulator (CMG-GEM) will also be performed. The results showed that for carbonate cores, maintaining the CO2/brine volumetric ratio above 1.0 reduced bicarbonate formation in the formation brine and helped in minimizing precipitation of calcium carbonate. Additionally, increasing cycle volume in WAG injection reduced the damage introduced to the core. Sulfate precipitation during CO2 sequestration was primarily controlled by temperature. For formation brine with high total dissolved solids (TDS), calcium sulfate precipitation occurs, even at a low sulfate concentration. For dolomite rock, temperature, injection flow rate, and injection scheme don't have a clear impact on the core permeability, the main factor that affects the change in core permeability is the initial core permeability. Sandstone cores showed significant damage; between 35% and 55% loss in core permeability was observed after CO2 injection. For shorter WAG injection the damage was higher; decreasing the brine volume injected per cycle, decreased the damage. At higher temperatures, 200 and 250 degrees F, more damage was noted than at 70 degrees F.

According to the Department of Water Affairs (DWAF, 2004 p.15), South Africa’s water resources are scarce and extremely limited and much of this precious resource is utilised and consumed in our industries. Treatment and re-use of effluent generated is, in some cases, preferred over use of alternate water resources (Du Plessis, 2008 p.3). The volume of effluent generated in treatment processes like ultra-filtration (UF) and reverse osmosis (RO) units is determined by the feed water quality, with high water loss through effluent generation at poor feed water quality. Current UF and RO applications require an increased UF production capacity due to the use of UF filtrate for periodic backwashing of the UF membrane units. This results in loss of water and decreases overall recovery. The need therefore exists to increase the overall recovery of product water from the raw water stream by reducing the amount of effluent generated. This would be possible to achieve by using RO brine to backwash the UF unit. The study was conducted to provide a modelling tool, assisting management to optimise the use of RO brine as backwash water on the UF system at the Medupi power station. The secondary objective of this study was the development of a modelling tool that can be used for other projects, new or existing, as a measure and indication of the usability of RO brine as backwash water on UF systems. By successfully applying this newly developed model, the viability of utilising the RO brine as backwash water for the UF was investigated. This modification would lead to utilizing smaller UF units than previously envisioned, which in turn leads to reducing capital cost with 11.07% and operating expenditure with 9.98% at the Medupi power station. This also has a positive environmental impact by reducing the amount of raw water used monthly by 10.34% (108 000 m3/month). / MIng (Development and Management Engineering), North-West University, Potchefstroom Campus, 2014