Reverse Osmosis
Key Technology in the Desalination Process
Reverse osmosis technology is divided into two steps:
- Pretreatment
- Membrane technology
Pretreatment
PRETREATMENT includes all necessary and fundamental treatments upstream of the reverse osmosis plant.
It is essential for:
- the life time of the plant
- minimize chemical cleaning
- To minimize the frequency of membrane replacement.
It therefore has a direct impact on plant performance.
Membrane technology
Membrane technology is an umbrella term for a number of different very characteristic separation processes. Membranes are increasingly being used to produce treated water from groundwater, surface water or wastewater. The membrane separation process is based on the presence of semi-permeable membranes.
The principle is quite simple:
the membrane acts as a very specific filter that allows water to pass through it, while retaining suspended solids and other substances.
Membranes act as a selective separation wall. Some substances can pass through the membrane, while other substances are captured. Process that occurs at low temperatures: allows treatment of heat-sensitive matter.
Low energy consumption:
most of the energy that needed is used to pump fluids through the membrane
Membrane filtration can be divided into:
MICROFILTRATION – ULTRAFILTRATION
– Removal of large particles – High efficiency
– Low pressure differences
NANOFILTRATION – INVERSE OSMOSIS
– Does not work on the pore principle – Removal of salts from water – High pressure differences
Reverse Osmosis, commonly referred to as RO, is a process in which water is demineralized by flowing under pressure through a semipermeable membrane.
Permeable
the membrane is permeable to some species (water molecules)
Not Permeable
the membrane is not permeable to some species (dissolved ions and other contaminants)
Reverse osmosis
A semipermeable membrane is placed between 2 compartments. To achieve equilibrium (same concentration of salts in both sides of the membrane, a fundamental rule of nature), water will flow from the pure water compartment to the salt-containing compartment to dilute the salt solution.
