Impact of aeration on/off duration on the performance of an intermittently aerated MBR treating real textile wastewater

Abstract

Uncontrolled discharge of textile industry wastewater, defined by its highly toxic content, causes serious prob-lems in receiving environment. Especially nitrogen-derived pollutants in wastewater threaten the ecosystem and aquatic life. Separate or simultaneous nitrification/denitrification is the preferred biological processes for removing nitrogen-based pollutants from wastewater. This study aimed to evaluate the impact of aeration on/off cycle durations on organic matter, color, and nitrogen removal performances in an intermittently aerated membrane bioreactor (MBR) receiving real textile wastewater. For this purpose, the MBR was operated under different dissolved oxygen concentrations (6 and 3 mg/L) and the aeration on/off cycle durations (from 2 min/2 min to 90 min/360 min) at a constant flux of 10 L/(m2.h). While the chemical oxygen demand (COD) removal performance ranged from 84 to 91 %, the color removal efficiencies were highly variable. Nitrification perfor-mance of & GE;89 % was achieved with a minimum of 30 min aeration cycles. The highest denitrification efficiency was obtained in the cycle with 360 min aeration-off duration. Intermittent aeration provided higher TN removal, less sludge generation, and lower energy requirements for aeration. The impacts of aeration cycle duration on membrane filtration performance and foulant characterization were also investigated by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), gel-permeation chromatography (GPC), SEM coupled with energy dispersive spectroscopy (SEM-EDS), particle size distribution (PSD) analyses.