Introduction Of Reverse Osmosis System
Reverse Osmosis (RO) is a water purification technology that uses a semi-permeable membrane. This membrane technology is not exactly a filtration method. In reverse osmosis, an applied pressure is used to overcome osmotic pressure, a colligative property that is driven by the chemical potential which is a thermodynamic parameter.
Reverse osmosis through a semi-permeable membrane can remove many types of molecules and ions from solutions, and is used in both industrial processes and the production of potable water. Reverse osmosis is most commonly known for its use in drinking water purification from water and those areas where water contamination includes viruses and chemicals like metal ions, lead, arsenic, fluoride, radium, sulfate, magnesium, potassium, nitrate, fluoride, and phosphorus
Main Components of Reverse Osmosis System :
1 Dual Media Filter: This removes the total suspended solids, dirt, and iron and reduces silt. The raw water from the source is taken to a Dual Media Filter (DMF) where all the suspended solids are removed with the help of a filter bed. The filter requires a backwash when differential pressure goes above 0.5Kg/cm2 or when it stops giving desired output or after a pre-decided time interval.
2 Activated Carbon Filter: Filtered water from a dual media filter is fed to an activated carbon filter in order to remove free chlorine, organic compounds, color and smells. The filter requires a backwash when differential pressure goes above 0.5Kg/cm2 or when it stops giving desired output or after a pre-decided time interval.
3 Antiscalant Dosing System: The commonly used reverse osmosis (RO) membranes consist of a polyamide salt-rejecting film on a poly-sulphone base. The very thin surface layer of polyamide (up to 3 µ m) provides the semi-permeable and salt-rejecting properties to the membrane. RO systems create salt-concentrated water streams on rejection sides that could produce scale or fouling on the membrane. This may lead to the blocking of the flow channels in the membrane. The antiscalant chemical is added online to protect the membrane from scaling/ fouling formation.
4 Reverse Osmosis Membrane: Reverse Osmosis is the tightest possible membrane process in liquid/ liquid separation. In principle, water should be the only material passing through the membrane and essentially all dissolved and suspended material is rejected. The Reverse Osmosis Membrane is the heart of the system. The most commonly used is a spiral wound of which there are two options: the CTA (cellulose triacetate), which is chlorine tolerant but of lower service life, and the TFC (thin film composite/material), which is not chlorine tolerant but higher service life.
Advanced reverse osmosis technology uses "crossflow" that allows a partially permeable membrane to clean itself continuously. As some of the fluid passes through the membrane, the rest continues downstream, sweeping the rejected species away from it. The process requires a pump to push the fluid through the membrane. The higher the pressure, the larger the driving forces. As the concentration of the fluid being rejected increases, so does the driving force.
Reverse osmosis is used to reject bacteria, salts, sugars, proteins, particles, dyes, and other constituents. The separation of ions with reverse osmosis is aided by charged particles. This means that dissolved ions such as salts are more likely to be rejected by the membrane. The larger the charge and the particle; the more likely it will be rejected.
5 Ultraviolet System: Sunlight has long since been known to kill micro-organisms. The rays from the sun contain the UV spectrum which is being used in Ultraviolet Water Treatment Systems – although at much lower intensities. It is also referred to as the Germicidal Spectrum/frequency. The frequency used in killing micro-organisms is 254 nanometers (nm). The UV lamps used for this purpose are designed specifically to have the highest amount of UV energy at this frequency.
