RO Recovery, Concentrate Flow, and Concentration Factor

Recovery R = permeate / feed, concentrate (reject) flow = feed - permeate, and the concentration factor CF = 1 / (1 - R) is how much the rejected salts pile up in the reject. At 75% recovery (10 gpm feed, 7.5 gpm permeate) the reject is 2.5 gpm and CF = 4, so a 500 mg/L feed leaves about a 2,000 mg/L concentrate; 50% recovery is only CF = 2. Pushing recovery higher shrinks the reject but raises CF sharply, and past the scaling limit of the least-soluble salt the membrane fouls -- antiscalant and the LSI govern that ceiling. The membrane manufacturer's projection software and the state primacy agency (for a public system) govern the design.

recovery = permeate_gpm / feed_gpm; concentrate_gpm = feed_gpm - permeate_gpm; concentration_factor = 1 / (1 - recovery); concentrate_tds_mgl = concentration_factor x feed_tds_mgl (near-complete rejection).

AMTA (American Membrane Technology Association) and AWWA membrane-treatment practice, by name; the membrane manufacturer's projection software and the state primacy agency govern the design.

The recovery / concentration-factor relations are public first-principles mass balance; the feed and permeate flows and the feed TDS come from the operating data.

Estimate. Operator of record and primacy agency govern.

Field names used by the API: feed_gpm, permeate_gpm, feed_tds_mgl, recovery_pct, concentration_factor, concentrate_tds_mgl

• Mass balance recovery = permeate/feed; CF = 1/(1-recovery); reject TDS ~ CF x feed TDS at high rejectionAMTA / AWWA membrane practice
• Scaling ceiling high recovery raises CF past the least-soluble salt's saturation; antiscalant and the LSI governmembrane scaling control