The treatment of high strength wastewater containing high concentrations of ammonium in a staged anaerobic and aerobic membrane bioreactor

Abstract

In this paper, a staged anaerobic and aerobic membrane bioreactor was constructed and used to study the treatment of high strength wastewater containing high concentrations of ammonium. The membrane module was submerged in the aerobic zone (upper part) of the bioreactor and was operated under an alternating suction mode and air backwash mode. Air backwash and aeration around the membrane module served as the cleaning mechanism for the membrane; this resulted in the steady operation of the reactor at the flux of 5–14 L m–2 h–1 for 120–200 h without any additional cleaning. The efficiencies of the chemical oxygen demand (COD) removal were >99% for up to 10.08 g COD L–1 d–1 of the volumetric loading rate. Between 60 and 80% of COD was anaerobically biodegraded in the anaerobic zone (lower part) of the reactor and converted to methane that could serve as a carbon source for the denitrification in the upper part of the reactor. The intermittent aeration resulted in simultaneous nitrification and denitrification in the aerobic zone of the reactor. The capacity of the ammonium removal reached 0.5 g NH4+-N L–1 d–1. Between 84 and 94% of the total oxidized nitrogen converted from the oxidization of ammonium was denitrified. Key words: air backwash membrane bioreactor (MBR), high strength wastewater, anaerobic and aerobic treatment, ammonium removal, methanotrophic denitrification.