This study investigated the use of low temperature geothermal resources to convert salty produced water into a freshwater resource. The research retrofits soon-to-be-shut-down oil and gas wells as geothermal wells, simultaneously overcoming drilling costs and scale formation by using a freshwater closed loop system for thermal energy delivery. Heat transfer modeling was combined with water treatment thermodynamics to develop a predictive tool that can be used to estimate daily deliverable treated water. Results indicated that the developed model was most sensitive to well depth, geothermal gradient, and total dissolved solids in the produced water.Results also indicated that a 4,000 m deep well with a geothermal gradient of 0.05 º C/m can successfully treat produced water with as high as 170,000 mg/L total dissolved solids and still deliver almost 600,000 L of clean water per day. An illustrative demonstration indicated that in the Eagle Ford Shale in Texas, more than 60% of the drilled basin area can deliver at least half a million liters of treated water daily under ideal conditions. This is particularly meaningful as Texas experiences extended periods of drought and the treated produced water would represent a new and resilient source of water.

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Coastal water quality is strongly influenced by tidal fluctuations and water chemistry, with an increased likelihood of bacterial water quality impairment due to urbanization. To address these challenges, there is a need for computationally and financially practical models with sufficient rigor to simulate the hydrodynamics and bacteria sources in relatively small, shallow waterways with upstream freshwater dominance and tidal influence. This study presents a coupled Tidal Prism Model (TPM) and watershed runoff model (HSPF) for a tidally influenced and impaired stream near Houston, Texas, USA. The TPM accounts for loading from tidal exchange, runoff, point sources, and bacterial decay using an hourly time step. The linked models were calibrated to flow and E. Coli (for HSPF), and salinity and enterococci data (for the TPM). When further refined, the model captures the "order of magnitude" of natural variability using a dynamic net decay rate. To assess the effectiveness of management strategies to improve water quality, the coupled model is applied for various scenarios for wastewater treatment plant bacterial effluent controls and runoff reduction via low impact development. Strategies focusing on both point and nonpoint source reduction are necessary to improve water quality through the length of the waterway. The simulation tool employed here is extremely useful and can be readily adapted for other inland tidally influenced water bodies, thereby, enabling cost-effective watershed planning at multiple resolutions.