- Sketch a line diagram of a single pass reverse osmosis plant.(10)
Description of Single Pass RO Plant
A single pass RO plant treats seawater once through one bank of membrane modules, producing potable water and discharging the concentrated brine.
Main Components to Show in Line Diagram:
- Seawater inlet & coarse strainer – removes large solids.
- Feed pump – supplies seawater at low pressure.
- Pre-treatment filters – sand/multimedia filter → cartridge filter (≈ 5 μm).
- Chemical dosing system –
- Sodium hypochlorite (pre-chlorination) for sterilisation.
- Sodium bisulphite (de-chlorination) to protect membranes.
- Antiscalant dosing.
- High-pressure pump – raises pressure to ~55–70 bar for seawater.
- RO membrane pressure vessel – semi-permeable membranes separate:
- Permeate (fresh water) → flows to storage tank.
- Brine reject → discharged overboard.
- Post-treatment system – chlorination, mineral dosing, UV or silver ion sterilisation.
- Product tank – storage of treated fresh water.
Monitoring Instruments to Label:
- Pressure gauges (before and after high-pressure pump, across membranes).
- Flow meters (feed, permeate, and brine).
- Conductivity/TDS meter (on permeate line).
- pH meter (on chemical dosing line).
Sketch (Exam-style Line Diagram)
Draw a left-to-right block diagram with arrows:
Seawater Inlet → Strainer → Feed Pump → Sand Filter → Cartridge Filter → Chemical Dosing → High-Pressure Pump → RO Membrane Vessel →
- Permeate Line → Conductivity Meter → Post-treatment → Product Tank
- Brine Line → Overboard
Label all monitoring instruments and dosing points clearly.