Characterization of Dry-Spun Acrylic Fiber Wastewater by Particle Size Distribution, Biodegradability, and Chemical Composition

Dry-spun acrylic fiber wastewater of large volume, high organic concentration, and low biodegradability is difficult to be treated by traditional treatment process. Detailed characterization of the wastewater is necessary to provide valuable information on designing effective treatment processes. The objective of this paper was to investigate particle size distribution and the associated biodegradability and chemical composition of dry-spun acrylic fiber wastewater. For this purpose, gradient membrane separation was carried out, the evaluation of biochemical oxygen demand over a 5-day period/chemical oxygen demand (COD) and tetrazolium chloride-dehydrogenase activity was investigated and analysis of Fourier transform infrared spectroscopy, gas chromatography-mass spectrometry and electrospray ionization-Fourier transform ion cyclotron resonance mass spectrometer was characterized. It is appeared that the particles are consecutive distributed in the wastewater. The main pollutants are soluble organics accounting for 61.4% of COD, followed by colloidal compounds (25.7% COD) and settleable/supracolloidal compounds (12.9% COD). The organics distributed in the range of 2-10nm are easily to be biodegraded, but soluble and settleable/supracolloidal fractions are biorefractory. The reason could be high molecular polymers containing N-H, O-H, C=O groups were exited in the settleable/supracolloidal fractions, and some toxic components including C6H6N2, C7H8O2, and some NSO heterocycles were dissolved in the soluble fractions. The results indicated that removing the settleable or supracolloidal substances and improving biodegradability of the soluble organics by pretreatment are necessary for the treatment of dry-spun acrylic fiber wastewater.