To properly design and size a reverse osmosis system, it is necessary to evaluate hydraulic, chemical-physical, and operational parameters such as required flow rate, inlet water quality, pressure, membrane type, and treatment objectives.

Here is a detailed overview:

Key parameters for sizing

1. Required flow rate

• Measured in liters/hour or m³/day.
• Determines the number of membranes and pump power.

2. Inlet water quality

• Evaluation of:
• TDS (Total Dissolved Solids) in ppm.
• Electrical conductivity.
• pH, hardness, free chlorine, turbidity, presence of metals.
• Influences the choice of pretreatment and membrane type.

3. Operating pressure

• Must exceed the osmotic pressure of the solution being treated.
• Typically between 6 and 70 bar, depending on salinity.

4. Recovery and Rejection

• Recovery rate: % of treated water that becomes permeate (e.g., 50–75%).
• Rejection rate: % of salts removed (e.g., 95–99%).

5. Water Temperature

• Affects membrane viscosity and permeability.
• Design data often refers to 25°C.

Components to Select

• Osmotic Membranes
• Type: TFC (Thin Film Composite), polyamide.
• Size: 4″ or 8″ diameter.
• Number: calculated based on flow rate and recovery.
• High-pressure pump
• Power calculated based on flow rate and required pressure.
• Corrosion-resistant materials (e.g., AISI 316).
• Pre-filtration
• Sand filters, activated carbon, microfiltration.
• Antiscalant and dechlorination dosing.
• Control system
• PLC or digital controller.
• Pressure, conductivity, flow, and level sensors.