| Given the increasing water shortage and growing energy demand, novel approaches to water reuse are critical to ensuring sufficient water supply for cooling in thermoelectric power plants. Major challenges arise from complicated chemistries of the waters under consideration and changing operating conditions in open recirculating cooling systems, both of which lead to accelerated mineral precipitation/deposition (mineral scaling). This study evaluated three impaired waters, namely, secondary-treated municipal wastewater, passively-treated abandoned mine drainage, and coal-ash transport water for their use in cooling water systems. The focus of the study was on understanding the mechanisms, kinetics, and inhibition of scaling from both fundamental and applied perspective.;Scaling inhibition with a variety of antiscalants was investigated and polymaleic acid (PMA) was the most effective antiscalant in all three waters. Scale control with PMA is achieved through retardation of mineral precipitation via PMA's competitive interactions with crystallizing ions, and stabilization of suspended mineral particles via surface adsorption of negatively-charged PMA molecules. Nevertheless, biofouling and corrosion, two other main technical challenges in water reuse for cooling, compromised the effectiveness of PMA for scaling control.;Equilibrium-based chemical modeling for scaling prediction exhibited limited success for cooling systems using impaired waters. The model that considered CO2 degassing, NH3 stripping, and kinetically-limited solids formation captured the underlying mechanisms dictating the pH changes observed in pilot-scale cooling towers.;Electrochemical Impedance Spectroscopy (EIS) was developed as an in situ, sensitive approach for monitoring scaling rates by measuring the electrical impedance at the solid-liquid interface. The EIS capacitance correlated very well with the mass of mineral deposits and was independent of the chemical composition of the deposits. The applicability of the method was successfully expanded to systems with multiple minerals and broader water chemistries, including secondary treated municipal wastewater.;The key findings of this study indicate that it is possible to control scaling of several impaired waters used as makeup water in cooling systems. The chemical treatment approach demonstrated in this study offers an alternative to costly pre-treatment that is often suggested when impaired waters are used in cooling systems. |
