Study On Biodegradation Characteristics Of The Polyester Fiber Alkali-decrement Wastewater

The biodegradability of polyester fiber alkali-decrement wastewater was studied by activated sludge under aerobic,anaerobic/aerobic alternating and anaerobic conditions.The biodegradation characteristics and microbial community structure in biological treatment systems were studied.The component analysis of refractory pollution in the wastewater was conducted by gel permeation chromatography(GPC),filtration membrane method and three-dimensional fluorescence technique(3D-EEM),respectively.Scanning electron microscopy(SEM)and high-throughput sequencing techniques were used to analyze microbial morphology and microbial community structure in sludge.In addition,the technical feasibility of combined process(biological treatment + Fenton oxidation + biological treatment)for the treatment of alkali-decrement wastewater was also evaluated,and the degradation of oligomers was discussed in detail.The results of this study are as follows:(1)the degradation efficiency of alkali-decrement wastewater was the highest under fully aerobic conditions,followed by the anaerobic/aerobic alternating conditions,and fully anaerobic condition was the lowest.Gel permeation chromatography and filtration membrane method showed that aerobic,anaerobic/aerobic alternating and anaerobic conditions had different removal rules for different molecular weight organic substances in alkali-decrement wastewater.Under aerobic,anaerobic/aerobic alternating and anaerobic conditions,organic matter near relative molecular weights of 1500-1600 Da and 530 Da could not be completely degraded(polyester oligomer),and under anaerobic conditions,organic matter near the relative molecular weight of 370 Da could not be degraded and removed.The 3D-EEM analysis showed that in addition to polyester oligomers,soluble microbial metabolites and humic acids were difficult to completely degrade.The changes of the fluorescence spectrum were similar to the degradation of COD and UV254.(2)The organic matter and intermediates in the alkali-decrement wastewater have a great influence on the microbial activity,and the composition of extracellular polymer(EPS)has a certain relationship with the microbial activity.The EPS content of the sludge in three reactors showed an increasing trend with the extension of the hydraulic retention time(HRT).(3)High-throughput sequencing results show that the microbial richness and diversity index in the aerobic reactor is much lower than that of the anaerobic and anaerobic/aerobic alternating reactors.Proteobacteria,Firmicutes,and Bacteroidetes are dominant bacteria,while the dominant bacteria of anaerobic reactor also include Chloroflexi and Spirochaeta.The distribution of microorganisms in the system at the genus level is different from that of inoculated sludge.(4)Compared with a single biological treatment,the combination process of "aerobic biological treatment + Fenton oxidation + aerobic biological treatment" shows high pollutant removal efficiency on the treatment of alkali-decrement wastewater.This could be attributed to the degradation of polyester oligomerization that can shorten HRT.Therefore,the combined process is a more suitable process for the treatment of alkali-decrement wastewater.