Reverse osmosis
Filtration methods include reverse osmosis, ion exchange, and activated carbon. Reverse osmosis works differently from chemical or ultraviolet protection, using a membrane that has fine pores, passing H2O while preventing larger molecules such as salts, carbonates, and other micro-organisms from passing through it. If there is insufficient energy to naturally force the water through the membrane, a powerful pump is required, resulting in potential high energy costs. In addition, RO units are capable of softening water. Some living micro-organisms, including viruses, are capable of passing through an RO unit filter.