Organics and nitrogen removal from textile auxiliaries wastewater with A²O-MBR in a pilot-scale

Highlights: • A pilot-scale A²O-MBR system treating textile auxiliaries wastewater was assessed. • Organic matter and recycle ratio strongly affected the performance of the system. • GC/MS analysis found some refractory organics in the MBR permeate. • Combination of organic foulants and inorganic compounds caused membrane fouling. - Abstract: The removal of organic compounds and nitrogen in an anaerobic–anoxic–aerobic membrane bioreactor process (A²O-MBR) for treatment of textile auxiliaries (TA) wastewater was investigated. The results show that the average effluent concentrations of chemical oxygen demand (COD), ammonium nitrogen (NH₄⁺–N) and total nitrogen (TN) were about 119, 3 and 48 mg/L under an internal recycle ratio of 1.5. The average removal efficiency of COD, NH₄⁺–N and TN were 87%, 96% and 55%, respectively. Gas chromatograph–mass spectrometer analysis indicated that, although as much as 121 different types of organic compounds were present in the TA wastewater, only 20 kinds of refractory organic compounds were found in the MBR effluent, which could be used as indicators of effluents from this kind of industrial wastewater. Scanning electron microscopy analysis revealed that bacterial foulants were significant contributors to membrane fouling. An examination of foulants components by wavelength dispersive X-ray fluorescence showed that the combination of organic foulants and inorganic compounds enhanced the formation of gel layer and thus caused membrane fouling. The results will provide valuable information for optimizing the design and operation of wastewater treatment system in the textile industry