Work out ro membrane area instantly with clear inputs, formula shown and shareable results.
Membrane area is permeate flow divided by design flux. Flux is limited by fouling potential: 12-18 L/m2/h for surface water, 18-27 for brackish groundwater and up to 35 for high-quality feed. Elements are grouped into pressure vessels holding six or seven, and vessels into stages.
Membrane area
Area (m2) = permeate flow (m3/h) x 1000 / flux (L/m2/h)
Element count
Elements = ceil(area / area per element); vessels = ceil(elements / elements per vessel)
High flux accelerates concentration polarisation and fouling, raising cleaning frequency and shortening membrane life. Design flux must reflect the feed's silt density index and organic content.
Concentrate from the first stage feeds a smaller second stage, typically in a 2:1 ratio, which raises overall recovery while keeping flux and crossflow velocity within limits in each stage.