The ordinary water available through lakes, wells, hand pumps, municipal taps, ponds or other sources is not so pure because of certain harmful elements like nitrates, arsenic, lead and other such pollutants. Water gets polluted due to these contaminants. Its quality is decreased. Different concerns associated with supply of water make suitable arrangements for its purification. Varied types of methods including the Reverse Osmosis and Thermal Desalination have been introduced for providing neat and clean water to the needy persons. These technological developments have enabled the society to enjoy pure water that is a must to maintain our health in fittest manners.
Importance of Water purification systems
Different types of water-purifying systems including the Reverse Osmosis System and Thermal Desalination are available in the market. All of them are significant in their own terms. Those installing such systems are able to enjoy pure water that is free from contaminants. Sufficient quantity of drinkable water is made available through such systems. No side effects are reported with the pure water through these sources of water-purification.
Major differences between RO System and Thermal desalination
Persons intending to install any of the above systems must be aware of the following basic differences associated with them:
Steam v/s temperature membrane
The thermal desalination process involves use of extraction steam at apt temperature and the pressure drawn from the power plant. Water obtained through such systems is quite pure in all respects. Multistage-flash (MSF) and thermo compression alternatives are made use of under this system, i.e. the thermal desalination process. However the RO system involves use of an ambient temperature membrane process. No steam or such things as in the case of the former method; i.e., the thermal desalination method is used in RO Systems.
Mixed bed downstream v/s DM plants
The thermal desalination process generally requires use of mixed bed downstream polishing units to reach the boiler feed quantity. However the Reverse Osmosis units need full-fledged DM plants, i.e. Demineraliser Plant.
Deep thought should be given to this aspect too. It may be noted that considerable amount of energy is needed for the RO systems to pressurize the water to the membrane filters. However the thermal desalination process needs the heat energy to heat the brine before vaporization. Latest technological developments have improved the situation. Now lesser power is needed to run the system. The multi-staged flash systems under the thermal desalination need about 17 kwh /M3 of water (heating and pumping power) whereas the RO process may need only 5 kwh /M3 for RO process. As such the MSF systems can work well only if the steam energy is available in abundance that too at reasonable costs.
Output of dissolved solids
It may be noted that water with less than 100 mg / L total dissolved solids is produced through the MSF systems under the thermal desalination process as compared to that of 400 mg /L in the RO system. As such need for second set of membrane units may be needed for getting higher standards of water qualities and it may prove a costly affair.
Reverse Osmosis systems need feasible arrangements for removing the suspended solids, biological organisms and other debris. RO systems also need necessary check on the pH and other chemical regimes. However in the case of the Thermal Desalination Process nothing of these arrangements is needed. MSF systems under this process involve vaporization. This feature should also be considered well as it results in heavy costs with regard to the RO systems.
It is worth mentioning that the maintenance costs of MSF plants involving Thermal Desalination Process are quite costly. It is because of the fact that they require increased land, construction and other costs. However, the RO systems can be maintained well at much less costs. The unit cost of water purification is also less in respect of RO systems as compared to the thermal desalination process.
Nearly sixty percent of the requirements of pure water are generally fulfilled through the RO systems, yet a large section of the society depends upon thermal process too. These points may be borne in mind by the persons or companies that wish to go ahead with the Reverse Osmosis System or the Thermal Desalination Process for water purification purposes.