Characterization of the microplastic photoaging under the action of typical salt ions of biological nitrogen removal processes.

Microplastics (MPs) are one of the most prevalent and diverse contaminants, and wastewater treatment plants are significant MP aggregators. Controlling the pollution caused by microplastics requires an understanding of how they age. The properties of the MPs photoaging process under the influence of salt ions typical of biological nitrogen elimination processes were disclosed in this work. The aging process of polyvinyl chloride microplastics (PVC-MPs) was greatly slowed down by greater HCO3- and NO2- concentrations, according to a comparison of the carbonyl index changes that occurred during photoaging. The carbonyl index had a negative correlation with the thermal stability of the photo-aged PVC-MPs, and aging accelerated the elimination of chlorine from the water. The samples were aged by UV radiation after 36 h at 40 °C, and the amount of chlorine eliminated was 10.13 times greater than that of the original MPs samples. It was discovered that the leachate concentration of aged MPs dramatically increased with decreasing particle size and was positively connected with the level of aging by comparing the concentration of leachate for two particle sizes (1 mm and 100 m). Photoaging caused MPs to become rougher, which in turn improved the NO3--N, NH4+-N, and NO2--N adsorption by PVC-MPs.

[Removal Characteristics of Four Typical Antibiotics in Denitrification System].

Wastewater treatment plants are an important gathering place for antibiotics, where denitrification plays a vital role in biological nitrogen removal. In order to explore the removal characteristics of antibiotics in a denitrifying sludge system, norfloxacin (NOR), oxytetracycline (OTC), sulfamethoxazole (SMX), and trimethoprim (TMP) were selected to investigate their transformation under different carbon source conditions in a denitrification system. The contribution of adsorption and biodegradation for antibiotic removal was also evaluated in this study. The results showed that a certain proportion of NOR, OTC, and TMP could be removed by denitrification, whereas NOR and OTC could act as the sole carbon source for denitrification. The removal of NOR and OTC showed a rapid adsorption and then slow biodegradation trend in the denitrification system. The contributions of adsorption were recorded as 83.5% and 58.9% for NOR and OTC removal, respectively. More than 40% were adsorbed by extracellular polymer substances (EPS), whereas the P450 enzyme played an important role in the OTC biodegradation process, with a contribution of 20%.