Sea Water Reverse Osmosis
The typical single-pass SWRO system consists of the following components:
- Pre treatment
- High pressure pump
- RO Membrane Banks
- PH adjustment
Last two components are required if the product water is used for drinking purpose.Pre-treatment normally consists of battery of filters to remove suspended matter & colloids. Sometimes DAF is also used to remove the floating oil if any. Few plants also have UF as pre-treatment to ensure consistent feed water quality.High Pressure Pumps are required to overcome the Osmotic pressure of Saline water & have pressure ranging from 50 Bar to 75 Bar depending upon feed water TDS.the membrane is designed to allow only water to pass through this dense layer while preventing the passage of solutes (such as salt ions). This process requires that a high pressure be exerted on the high concentration side of the membrane 40–70 bar (600–1000 psi) for seawaterThe spent energy from the reject is stream is recovered in large plant by Energy Recovery Devices (ERD). The plant size normally dictates the type of ERD. The Energy Recovery Turbine (ERT) and Pressure Exchangers (PX) are very popular.RO Membrane Banks form the heart of the system & have piping manifolds, Membrane Housings and Semi-permeable membranes.The permeate is often further treated by disinfecting it & remineralising it to make it stable (non corrosive), improve the taste and safe to drink.The system is fitted with adequate instrumentation & control for safe & steady operations.
A very important aspect of SWRO is material selection. The wetted material needs to selected carefully for long life of the plant. High grade stainless steels like SS 904L, Duplex, Super Duplex, Bronze are some of the preferred materials for valves & piping.