Advanced treatment of Membrane Bioreactor (MBR) effluents for effective wastewater reclamation

Abstract

One of the two main objectives of this work is to oxidize MBR effluents with ozone/peroxide in high pH conditions in order to improve oxidation of pharmaceuticals, which could efficiently be rejected by the nanofiltration (NF) stage. The other main objective is to effectively oxidize of dissolved organic carbon (DOC) in MBR effluents in order to decrease fouling in the filtration stage. In this work, ozone/peroxide oxidation was applied to the MBR effluents in high pH conditions in order to improve the formation of OH radicals, and oxidized effluents were filtered by the NF membrane (NE90) in order to investigate fouling potentials and the removal of pharmaceuticals. Natural and synthetic wastewater samples were used as feed solutions for the MBR system, which was equipped with a U-shaped hollow fiber membrane module. The flux decline was decreased from 29% to 15% when 9 mg/L of ozone was used, the same decline was also observed when 6 mg/L ozone and hydrogen peroxide (1/1 ozone/peroxide mol ratio) were used. A further decrease in flux decline was observed when pH was adjusted to 9.00 (29% to 9%) prior to the ozone/peroxide oxidation. In most cases, the increase in the ozone dose, the addition of hydrogen peroxide and the adjustment of the pH level led to an increase in the removal of pharmaceuticals. Iopromide, TCEP and Naproxen were found to be more resistant to the oxidation when pH was increased.