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.

Proper disposal of industrial brine has been a critical environmental challenge. Driven by the even-tightening environment protection regulations, the Zero-Liquid-Discharge (ZLD) has gradually become mandatory option for brine disposal, but its application is limited by the intensive energy consumption. The recent development of solar crystallizer provides a new strategy to achieve ZLD brine disposal. However, the research on solar crystallizer, employing photothermal material to convert solar energy to heat for interfacial brine evaporation and crystallization, is still at the early stage. This dissertation thoroughly investigated the solar crystallizer-based ZLD technology in a broad scientific and application context. The scaling formation while treating real brine, which has been the major barrier to the application of solar crystallizer, was confirmed first with a solar crystallizer device. With a rational designed anti-scaling mechanism, the scaling-free crystallization behavior and stable high water evaporation rate of 2.42 kg m-2 h-1 was achieved when treating real seawater brine. After verifying the feasibility of solar crystallizer towards real brine treatment, its performance was further improved by integrating convective airflow, which provided considerable environmental energy for water evaporation. Both experiment results and COMSOL simulation results confirmed that the maximum environmental energy harvesting can be achieved with the proper size of solar crystallizer. At last, this dissertation pioneered a novel concept of integrating adsorption process into solar crystallizer for simultaneously ZLD brine treatment and potassium extraction. Owing to the special ion concentration behavior of solar crystallizer, the adsorption capacity and selectivity coefficient of absorbent was enhanced by 19.5% and 48.8%, respectively, comparing with traditional bulk adsorption. This dissertation potentially unlocks a new generation of ZLD technology with low carbon footprint and source recovery. More research efforts will be inspired on its applications in real scenarios.

Dense wastewater discharges into marine environments can severely impact water bodies. This study addresses the disposal of hypersaline brines from desalination plants through multiport diffusers into seas and oceans. Accurate prediction of the mixing of discharges with the receiving water bodies is crucial for the optimal design of outfall systems. Designers can enhance mixing and increase dilution by modifying outfall properties. However, the interaction of discharges from multiport diffusers poses a significant challenge, impairing the mixing process. The main aim of this study is to improve multiport diffuser designs by limiting the negative effects of jet interaction on mixing. This research applies a three-dimensional numerical model, the Launder, Reece, and Rodi (LRR) turbulence model, to evaluate the predictive capabilities of the Reynolds Stress Models (RSM) for multiple dense jets and to explore the mixing characteristics and merging process of multiple jets. To validate the model, its predictions are compared with available experimental data. The LRR model showed good agreement with the experimental measurements, and the model outperformed the standard and re-normalization group (RNG) 𝑘−𝜀 turbulence models, making it a promising tool for studying the mixing behavior of multiport diffusers. This study proposes multiport diffusers with non-uniform port orientation as a means for mitigating the negative effect of jet mering on the mixing process and increasing dilution. Using the validated numerical model and the laser-induced fluorescence (LIF) technique, the effect of non-uniform port orientation on the mixing process is explored. The numerical results indicated that the orientation of adjacent jets significantly affected the behavior of individual jets. An individual jet exhibited a longer trajectory and higher dilution when its neighboring jets were disposed of with a different angle, compared to that of uniform discharges. Laboratory experiments on uniform and non-uniform diffusers, with varying port angles in the range of highest reported dilution rates for single discharges (40o-70o), are reported, and the major flow properties and merging processes are compared. Investigations revealed that non-uniform diffusers achieved overall higher mean dilutions due to different mixing behavior in the interaction zones. Non-uniform port orientation provided more space between the jets to expand before interacting with their neighbors, resulting in higher dilutions. This study challenges the application of formulae obtained from single discharge experiments for multiport diffuser designs and emphasizes the importance of considering source characteristics specific to multiport diffusers, such as angle difference, for efficient desalination outfall. The new data and analysis provided in this study can benefit the design of desalination discharge systems with considerable potential cost savings, especially for tunneled outfalls, due to shorter diffusers with non-uniform port orientations and environmental risk reductions.

CO2 sequestration is one of the proposed methods for reducing anthropogenic CO2 emissions to the atmosphere and therefore mitigating global climate change. Few studies on storing CO2 in an aquifer have been conducted on a regional scale. This study offers a conceptual approach to increasing the storage efficiency of CO2 injection in saline formations and investigates what an actual CO2 storage project might entail using field data for the Woodbine aquifer in East Texas. The study considers three aquifer management strategies for injecting CO2 emissions from nearby coal-fired power plants into the Woodbine aquifer. The aquifer management strategies studied are bulk CO2 injection, and two CO2-brine displacement strategies. A conceptual model performed with homogeneous and average reservoir properties reveals that bulk injection of CO2 pressurizes the aquifer, has a storage efficiency of 0.46% and can only last for 20 years without risk of fracturing the CO2 injection wells. The CO2-brine displacement strategy can continue injecting CO2 for as many as 240 years until CO2 begins to break through in the production wells. This offers 12 times greater CO2 storage efficiency than the bulk injection strategy. A full field simulation with a geological model based on existing aquifer data validates the storage capacity claims made by the conceptual model. A key feature in the geological model is the Mexia-Talco fault system that serves as a likely boundary between the saline aquifer region suitable for CO2 storage and an updip fresh water region. Simulation results show that CO2 does not leak into the fresh water region of the iv aquifer after 1000 years of monitoring if the faults have zero transmissibility, but a negligible volume of brine eventually gets through the mostly sealing fault system as pressure across the faults slowly equilibrates during the monitoring period. However, for fault transmissibilities of 0.1 and 1, both brine and CO2 leak into the fresh water aquifer in increasing amounts for both bulk injection and CO2-brine displacement strategies. In addition, brine production wells draw some fresh water into the saline aquifer if the Mexia-Talco fault system is not sealing. A CO2 storage project in the Woodbine aquifer would impact as many as 15 counties with high-pressure CO2 pipelines stretching as long as 875 km from the CO2 source to the injection site. The required percentage of power plant energy capacity was 7.43% for bulk injection, 7.9% for the external brine disposal case, and 10.2% for the internal saturated brine injection case. The estimated total cost was $0.00132–$0.00146/kWh for the bulk injection, $0.00191–$0.00211/kWh for the external brine disposal case, and $0.0019–$0.00209/kWh for the internal saturated brine injection case.