Synergistic cotreatment of cooling tower blowdown and produced waters: Modeling strategies for a comprehensive wastewater treatment simulation

Abstract

Cooling tower blowdown from thermoelectric power plants and produced water from hydraulic fracturing may soften when mixed due to the complimentary chemistry of the two wastewaters. The potential benefit of low effort softening warrants the investigation of a cotreatment process concerning these industrial wastewaters. The synergy is expected to lessen chemical demand for softening and further enable sustainable practices such as designing for a zero-liquid discharge (ZLD) process. The treatment process may then provide a treated effluent suitable for use as blowdown makeup. In this study, the feasibility and effectiveness of a cotreatment train is explored through simulation of chemical softening, filtration, reverse osmosis (RO), multi-effect distillation (MED), and electrolysis unit operations within a comprehensive process model. Innovative modeling strategies are necessary to result in a meaningful process model when considering the significant complexity of the water chemistry for this treatment train. Through the methodology described in this work, a feasible process design is presented as a base case for treatment of experimentally characterized blowdown and produced water samples obtained in the northern Appalachian region. Thereafter, the base case also establishes a platform for more detailed process analyses of different scenarios in future work. Detailed descriptions of modeling methodologies, process design decisions, and simulation results are provided as a perspective on comprehensive modeling of multi-technology treatment trains for complex feedwaters. With the results of the cotreatment simulation, it is determined that the total water recovery of the process may serve to completely makeup the blowdown rate and partially make up the evaporative losses of a theoretical thermoelectric plant's water demand. This complete recovery is evaluated to require 18,343.531 kW of a chemical energy equivalent, 1184.971 kW of electricity, and 68,126.291MJh−1 of power plant steam to result in 408.532m3h−1 of treated water effluent at a quality of approximately 0.135gL−1 total dissolved solids for the base case design.