If you have these use cases and are ready to take the next step, ask yourself these questions:
How should we use the water?
Some of the cases above may seem applicable to your facility, or a combination of several uses.
What are the water flows at my facility?
Facilities should start with a water audit that considers daily and seasonal use variations, assesses current and future water use (both quality and quantity) and determines potential combined uses of recoverable water. Reuse for cooling and irrigation, for example, will vary considerably depending on the season and weather conditions.
What are future water demands?
Reuse considerations should include a water study to predict future demands, understand conservation opportunities and determine water reuse opportunities on a site-wide basis. This will help predict total treatment needs and capacities for design purposes and help determine your return on investment.
What is the public perception and acceptance of the type of reuse?
The reuse of treated water will rely on acceptance of the end-user of the quality and reliability of the treatment technology, plant operations and continuity of “guaranteed quality,” including removal of unknown constituents that may be harmful. This is a critically important consideration and needs a business-based approach as well as employee and stakeholder education and programmatic methods to confirm acceptance—before implementation or construction of reuse technologies.
What is in the wastewater?
Sampling and analytical testing are needed to determine minimum, maximum and average loadings on the treatment system. These may include nontraditional analytical parameters such as PFAS compounds, salinity, hardness, alkalinity, silica, cations and anions, especially if membrane treatment systems are considered. These process streams can vary considerably in biochemical oxygen demand; chemical oxygen demand; fats, oils and grease; total suspended solids; pH; temperature; and salt concentrations.
What waste disposal options are available?
Water reuse must be compared to traditional discharge options. In reuse scenarios that use reverse osmosis and other membrane-based processes, the concentrated reject brine stream must be carefully managed and disposed. If this stream cannot be discharged into the publicly owned treatment works or surface water, then onsite evaporation or further concentration of the reject may be necessary, significantly increasing costs and the space required.
What are the potential costs and savings?
Reuse scenarios should be considered from a life-cycle cost perspective. Costs may include those for capital and operating and maintenance (with labor, electric/energy, chemicals and residuals disposal being the primary ongoing operational costs). Water reuse treatment costs depend on the water quality required. As the quality increases, the costs increase, and the level of technical sophistication required of facility operators increases likewise.