The seawater desalination process is employed to convert seawater into fresh water. Notably, seawater desalination is definitely not carried out in a single step. It is a time-consuming process involving multiple steps. Today, we will take a look at the various steps involved in seawater desalination.
Sea Water is delivered to the desalination system after pre-treatment
The very first step involves the delivery of the seawater or the raw water to the desalination plant through the intake pump. The raw water is duly pre-treated before it is delivered to the seawater desalination system. The pre-treatment is necessary to ensure that the water is rendered free of impurities.
There are innumerable suspended solids, clays, bacteria and dissolved organic matters that are susceptible to the RO or reverse osmosis membranes. Pre-treatment remains an important method with the help of which the fouling of the RO membrane is prevented. Activated filter, multi-media filter, and security filters are the three main types of pre-filters generally used.
The Reverse Osmosis or the RO system makes use of the semi-permeable membrane to eliminate the following materials from the feed water in order to produce completely desalinated fresh water. The semi-permeable membrane is responsible for separating the salt solution and water. It is the osmotic pressure which separates the water from the salt solution. Reverse osmosis takes place if the water permeates in the opposite direction owing to the application of pressure higher than osmotic pressure on the salt solution. The RO permeate is purified – thereby ensuring that around 98% of TDS is removed from feed water.
Energy Recovery and Reduction of Energy Costs
Then comes the stage when the energy recovery system is deployed to reduce energy consumption. Lower energy consumption leads to lower energy costs as well. the energy consumption can be reduced by reusing and recycling the pressure energy obtained from the RO system . ERD or Energy Recovery Device is a popular device employed while operating any seawater reverse osmosis desalination products. What exactly are the next steps involved in seawater desalination? We will find that out right here!
Chemical Cleaning required eliminating pollutants
After the work of the Energy Recovery System is done – comes the turn of the Chemical Dosing System. It remains an integral part of the seawater desalination system. Pretreatment of the water involves the coagulant and bactericide dosing, pH adjustment dosing (administered before the 2nd RO system) and antiscalant dosing administered before the 1st level RO. It is very important for companies offering desalination services to select well-designed dosing devices meant for easy operation.
Irrespective of how good the pre-treatment device is, the surface of the membrane will always be susceptible to some types of pollutants. In the long run, these pollutants end up hindering performance and raising the difference in pressure between the inlet and outlet. So chemical cleaning is necessary to eliminate dirt from the surface of the RO membrane. The comprehensive cleaning device consists of a cleaning pump, cleaning tank, and the filter.