Most SWRO quotations fail not because the equipment is wrong, but because the design basis was guessed. Before we size a train we ask for six things.
1. Feed water TDS and ionic composition
35,000 mg/L and 42,000 mg/L behave very differently, especially for boron and sulphate scaling.
2. Feed water temperature range
Membrane flux falls roughly 3% per °C below 25 °C. A winter minimum of 12 °C can add a whole membrane vessel.
3. Turbidity and Silt Density Index
SDI above 5 means you need better pre-treatment before the membranes, not bigger membranes.
4. Required permeate quality
Drinking water, irrigation and boiler feed have completely different targets. Boron below 0.5 mg/L needs a second pass.
5. Daily and seasonal demand profile
A resort with peak occupancy in August needs a different design than a town with flat demand.
6. Available power and footprint
Energy recovery makes sense above roughly 100 m³/day. Below that, the extra pump complexity may not pay back.
Send these six numbers and you will get a design that holds up at commissioning.
