Recycled membrane for drinking water treatment with high iron and manganese concentrations

Abstract

Membrane recycling by oxidative treatment is one alternative to minimize the impacts of the disposal of end-of-life (EoL) reverse osmosis (RO) membranes. In parallel, iron (Fe) and manganese (Mn) contamination in surface and groundwater is increasing. This study aims to develop recycled membranes that retain dissolved Fe and Mn from water for supply purposes. EoL RO membranes were recycled with sodium hypochlorite (NaClO, 10–12%) solution at exposure dose between 4000−80,000 ppm∙h to produce a recycled membrane with high flowrate and high Fe and Mn rejection. EoL RO treated by 40,000 ppm·h showed water permeability of 54.30 L∙h−1∙m−2∙bar−1 and Fe and Mn rejection of 99% and 65%, respectively. Potability for Mn (> 98%) was enhanced by integrating pre-oxidation stage with NaClO (5 mg∙L−1 of Cl- and pH 8) to the recycled membrane process. Recycled module performance was evaluated for water treatment from Paraopeba River on pilot scale, in continuous operation (51 h) and pressure of 1 bar. At pilot scale, recycled membrane obtained a water permeability of 40.33 L∙h−1∙m−2∙bar−1, like a moderately open ultrafiltration membrane. Fe and Mn removals were > 99% and > 90%, respectively, with high color and turbidity removal efficiency. Membrane recycling cost was predicted to be US$ 4.08/m², and the capital (CapEX) and operating (OpEX) expenditures for the single-household system was US$ 671.18 and US$ 22.52 to m3·day−1 of treated water. Therefore, the recycled membrane was shown to be efficient in removing dissolved Fe and Mn, and it is promising for decentralized water treatment.