Production of soluble microbial products in aerobic granular sludge system under the stress of toxic 4-chlorophenol

Abstract

ABSTRACTThe purpose of this study was to evaluate the effect of toxic 4-chlorophenol (4-CP) on the production of soluble microbial products (SMP) in an aerobic granular sludge system. Compared with the control experiment, removal efficiency generally reduced by 37.90% after the exposure of 4-CP of 10 mg L−1, indicating that 4-CP had a toxic effect on the performance of biological nitrification. Meanwhile, the contents of polysaccharides and proteins (PN) of SMP increased from 31.0 ± 0.32 and 0.8 ± 0.12 mg L−1 to 39.0 ± 0.56 and 61.70 ± 0.78 mg L−1, respectively. Specific oxygen uptake rate (SOUR) showed that the values of (SOUR)H, and reduced by 27%, 48% and 41% in the presence of 4-CP. The characteristic and chemical components of SMP were assessed by using three-dimensional excitation-emission matrix (3D-EEM), synchronous fluorescence spectra, two-dimensional correlation spectroscopy (2D-COS), scanning electron microscope and Fourier transform infrared spectroscopy . 3D-EEM implied that SMP were mainly composed of tryptophan PN-like, aromatic PN-like and humic acid-like substances after 4-CP exposure. Synchronous fluorescence spectra coupled with 2D-COS suggested that SMP samples changed in the following sequences: PN-like substances > humic acid-like substances in the absence of 4-CP, and shorter wavelength > longer wavelength in PN-like substances in the presence of 4-CP.