Reverse osmosis (RO) systems typically contain one, two or more activated filters depending on the specific model. The Environmental Protection Agency (EPA) recommends filter carbon as the best treatment for most situations, according to its list of regulated contaminants. That said, RO systems surely filter out numerous impurities from water, but the question is which?
For those keen on numbers, RO systems have been proven to remove between 95-99% of 52 listed contaminants. Some of the more high-profile impurities include, but not limited to: E.coli bacteria, fecal bacteria, shigella disinteriae, vibrio choleriae and salmonella typhi (all at >99.9%2). Other potentially toxic compounds whose majority (if not entirety) doesn’t get past RO membranes include lead, arsenic and radioactive particles (95-99%2).
All these filtration rates are based on the Nominal Rejection Characteristics sheets, which show the typical rejection percentages of various water impurities. All in all, the effectiveness of RO membranes can be largely (if not entirely) attributed to the wonders of activated carbon, which is also touted to be a taste and odor improver on several occasions. Some membranes are so powerful, in fact, that they’re enough to almost completely rid 20,000 gallons of water of its chlorine content.
RO membrane technology has evolved to a point when it can remove almost every impurity imaginable from water, making otherwise undrinkable waste completely potable. The prevalence of numerous plants worldwide prove this, and the technology is only getting better.