Depending on the objectives of the QSD study (e.g., the number of technologies to be evaluated), the scale of the system can vary from a single unit process to a network of multiple subsystems across different disciplines and industries. Similarly, resolution of the design, simulation, and analyses can be tailored to the different unit processes within the system. For example, a study optimizing the detailed design of RO technology focused on the selection and design of equipment that is directly related to the process (e.g., membrane units, pumps), while research that investigated management strategies for shale gas water and wastewater required researchers to account for multiple processes from water source to final disposal, including water acquisition, transport, storage, and wastewater treatment. Additional examples of QSD objectives and corresponding system boundaries can be found in Table (ESI).