In case of Reverse Osmosis (RO) Plants, being used to purify fresh water for domestic applications, these RO units recover only a portion as potable water out of the water entering the system. The remainder is discharged as waste water, which carries with it the rejected contaminants. So the discharge of such Wastewater may also eventually prove to be a concern, if it somehow finds it’s way to the source itself.
Due to its fine membrane construction, such ROs not only remove harmful contaminants present in the water, but it also may strip many of the good, healthy minerals from the water. Thus, the very same mineral quantity that freshwater sources provided previously is missing in case of RO water. A number of peer-reviewed studies have looked at the long-term health effects of drinking demineralised water.
The desalinated water needs to be stabilized against it’s aggressiveness to protect downstream pipelines and storages, usually by adding lime or caustic material to adjust pH between 6.8 and 8.1 to meet the potable water specifications, primarily for effective disinfection and for corrosion control.
Moreover, depending on the type of membranes used in RO, the Chlorine might need to be trapped from the water prior to entering into the RP Plant. Because, the thin film composite (TFC) membrane is prone to breaking down under the influence of chlorine, while the cellulose triacetate membrane is prone to rotting, unless protected by chlorinated water.
In practice, a fraction of the living bacteria can and do pass through RO membranes through minor imperfections, or bypass the membrane entirely through tiny leaks in surrounding seals. Thus, RO treated water may need additional water treatment stages so as to prevent microbiological contamination.
Keeping in view of above, is the use of RO justified for domestic application, unless the raw water is contaminated with Arsenic / Fluoride etc., which can not be removed suitably through conventional water treatment processes?
Your question is very interesting. And is an issue in the suppliying of water to human consume. The evaluation of the process you will decide to use depends of the necesities. If the contaminants are ionic like the arsenic and fluorine and there are no other treats, then you can choose another type of process like a ionic exchange column (than is cheaper than osmosis). But if you have a variety of contaminants, organic and inorganic may be like you said the RO will be not enough, and you will need previous and post treatment process. In summary you need a chemical profile, and even better an organic contaminants chemical profile to determine if is useful or not use the RO, and of course the money to use and maintain the process because in order to avoid the micro and chemical problems you will need a programm to mantein it. Like you say another problem is the output of a very low salts water, because you will need to balance the salinity, when you have no contaminants is easy, but when they are you will need the external supply and will be more expensive. Then is not at all justified the use of a RO in home because is a multi variable complex system (at least in home, not in industrial uses).
Greetings
- Badges
- Science topic