Desalination Theory – How Desalination Works
The Rainman watermaker operates through a process called reverse osmosis (RO).
In its most simple terms, the system draws seawater up, filters out sediment and particulates, then puts the clean seawater under high pressure to pass through an RO membrane. The RO membrane is a semi-permeable polyamide thin-film composite.
A traditional filter, like our prefilter, works by passing all the water through it. The fine construct prevents larger particles from getting through and they are captured on the filter material. When a lot of particles have been captured on the filter and it’s dirty, you change it.
In contrast to a traditional filter, the reverse osmosis process has filtered seawater passed across the membrane surface at high pressure. Keeping the description simple, the system is essentially extracting a small percentage of the freshwater from the seawater stream. The majority of the water and all of the salt continues in the flow and out the brine waste water hose. The salt does not accumulate on the membrane, which is why RO membranes do not need to be cleaned or replaced regularly.
Since bacterias and viruses are much larger than salt molecules, they stay in the main seawater stream and are passed out with the brine wastewater.