Low pressure reverse osmosis (LPRO) is an effective wastewater treatment process providing high permeation of water and high rejection of solutes. The LPRO experiments were made with inorganic solutions of Na+, Ca2+, Mg2+ and Cl- and organic matters in different concentrations and pH levels. The experimental results showed that the solute permeability in LPRO membrane depends on the charge of membrane and ions in many cases. The divalent cations provided lower rejection of coexistent cations in mixed solutions system than that of the cation in single solution system. The LPRO was very effective in removing inorganic matters and organic matters in artificial incineration ash leachate. The membrane permeations of inorganic ions in the leachate were similar to those in mixed solutions system.