RO-600Reverse Osmosis — Array, Flux and Energy

How it works

1. Against osmosis — Left alone, water moves from dilute to concentrated. RO reverses that by brute force: apply more than the osmotic pressure and water is pushed the other way, leaving the salt behind. Roughly 0.7 bar per 1000 mg/L is the price of entry before any water moves at all.
2. Along the vessel — Water leaves as permeate, so the feed concentrates as it travels. By 75 % recovery the concentrate is around four times the feed. Osmotic pressure rises with it, so the last element works hardest and produces least — the reason arrays are staged 2:1.
3. Flux and area — Flux is permeate per square metre per hour. Push it above roughly 20 LMH on brackish water and the concentration polarisation layer at the wall thickens, rejection falls and scaling starts. Low flux is a design choice, not a compromise.
4. Concentrate recycle — Returning part of the concentrate to the pump suction lifts system recovery when you cannot afford the reject. It also raises the feed concentration at the membrane, because the salt is still in the loop — so recovery on paper improves while the lead element walks toward scaling.
5. What governs it — Feed pressure must beat osmotic pressure plus what the flux demands, and that sets the energy bill. Recovery sets the concentrate strength and therefore the scaling limit. Drag recovery up and watch concentrate TDS and feed pressure climb together — they always do.
6. The 8-inch spiral element — The unit of currency in reverse osmosis: 37 m², six or seven per vessel, interchangeable between suppliers. Everything about array design — 2:1 staging, flux distribution, the shape of the curves above — is built around this element and its 1.6 bar of feed-channel loss.

Design parameters

The panel opposite runs the same correlations as the RO-600 design sheet, so the animation and the calculator cannot disagree. Every parameter below is live — drag one and the picture responds.

Open the full RO-600 design sheet for the other nine inputs, all forty results with their envelopes, the seven equations printed beside the numbers they produce, and a calculation record you can export and put in a design file.