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Setting recovery and brine flow in an SWRO specification
Translate product water demand into an explicit feed and concentrate balance for preliminary desalination design.
HOSON WATER editorial ·
Put product, feed and concentrate in one balance
RO recovery is product flow divided by feed flow. At a nominal 320 tons per day of product and 35% recovery, the simple balance is approximately 914 tons per day of feed and 594 tons per day of concentrate. This calculation describes the RO process under a steady, idealized condition. Pretreatment washwater, cleaning drains and downtime need separate treatment in a site-wide balance.
Define the constraints that set recovery
Ask the designer to consider feed chemistry, concentration of scale-forming constituents, membrane limits, antiscalant compatibility and the permitted concentrate route. Higher recovery reduces concentrate volume per unit of product and can increase the concentration of dissolved constituents. The proposed recovery should be supported by projections using the site’s actual ion profile across the expected seasons.
Locate responsibilities outside the skid
Identify who provides intake, discharge permits, equalization, secondary treatment, final outfall and sampling access. Record expected concentrate flow and quality in the project data sheet. Ask for a list of alternate setpoints the plant can use during different source conditions so the owner can budget for the corresponding water intake and discharge.