[Change in Granulation Potential and Microbial Enrichment Characteristics of Sludge Induced by Microplastics].

Microplastics (MPs), as a new type of pollutant, are widely detected in sewage treatment plants. Currently, research on MPs in traditional sewage treatment systems has mainly been focused on the pollution level and distribution characteristics, with a lack of studying the impact of MPs on the sludge granulation. In order to explore the effect of MPs on the granulation process, a microplastic exposure test was conducted by adding polyethylene terephthalate microplastics (PET-MPs), which are widespread in the environment. The operating performance of the system, extracellular polymeric substance (EPS) composition, and flora enrichment were analyzed on the sludge granulation. The results showed that the exposure of PET-MPs significantly accelerated the sludge granulation process, whereas the increase in EPS content dominated by PN enhanced the sludge surface hydrophobicity; the granulation rate and EPS secretion were proportional to the exposed particle size. Microplastics and EPS secretions synergistically promoted the formation of granular sludge. However, continuous microplastic exposure led to deterioration of the system decontamination performance and inhibited the degradation process of pollutants, with the most negative effect of nitrite nitrogen accumulation under 250 µm PET-MPs exposure, as high as (5.08±0.24) mg·L-1. The high-throughput sequencing revealed that the microbial community diversity fell in the experimental group. The dominant bacteria at the phylum level were Proteobacteria and Bacteroidota on the sludge granulation. Rhodocyclaceae, Sphingomonadaceae, Flavobacteriaceae, and Rhodanobacteraceae promoted flocculation by increasing EPS secretion. The decrease in Comamonadaceae and Chitinophagaceae weakened the ammonia and nitrite oxidation capacity of the system, whereas the decrease in Rhodobacteraceae, Hyphomonadaceae, and Xanthomonadaceae inhibited the removal of nitrate nitrogen.

[Degradation of styrene by coupling ultraviolet and biofiltration].

Purification of styrene by ultraviolet (UV)-biofiltration was studied in this paper. The light source and the biofilm carrier were ozone producing lamp at 185 nm and the peat, palm fiber, porous acticarbon, respectively. Styrene inlet concentration was controlled between 320-583 mg x m(-3), and the removal efficiency remained above 95% after stabilization. The UV converted styrene into more soluble and biodegradable intermediates, such as alcohol, aldehyde and acid, thus the performance of biofilter can be improved. In the stable operation stage, the variation of inlet concentration did not affect the removal efficiency when the total residence time (TRT) was long, however, the inlet concentration obviously affected the removal efficiency when the TRT decreased. The removal load of coupling system increased linearly with increasing inlet load, and the removal efficiency was higher than 95% under a TRT of 102 s. When TRT was 68 s and the inlet load was low, the variation of removal load complied with the law described above, but it gradually deviated from the straight line and tended to stabilized at a certain value when the inlet load became higher than 30 g x (m3 x h)(-). If considering the fluctuation of styrene concentration only, the contribution rate of ultraviolet photolysis to styrene removal was greater than that of the biofilter, and the removal effect could be restored on the fourth day, after closing the system for ten days and restarting.