Journal of Environmental Analytical Chemistry

This study explores the influence of temperature on the tolerance of polyphosphate accumulating organisms (PAOs) to Zn(II) in enhanced biological phosphorus removal. The results show anaerobic and aerobic metabolisms of PAOs decreased with increasing Zn(II) concentration varying between 0-2 mg L-1 and temperature indeed affected inhibitive degrees. Furthermore, Zn(II) is more toxic to anaerobic poly-P hydrolysis and glycogen degradation at 10°C than at 20 and 30°C. For anaerobic polyhydroxyalkanoate (PHA) synthesis, Zn(II) had a highly inhibitive effect at 10°C too. The inhibitions of PAOs aerobically taking up phosphorus, degrading PHA and replenishing glycogen in the presence of Zn(II) were amplified at 10°C. The metabolism of aerobic PHA degradation at 10°C was completely terminated and the aerobic replenishment of glycogen at 10° C was also completely terminated at 0.1 mg L-1 of Zn(II) due to the complete inhibition of aerobic PHA metabolism, which provides the required reducing power for synthesizing glycogen.

With the drastic increase in plastic production, the input of plastic particles into the environment has become a recognised problem. Xenobiotics are able to sorb to polymer materials, and this process is further enhanced where they encounter microplastics (plastic fragments <5 mm). In this work we studied the sorption of metformin, a type-2 diabetes drug, and difenoconazole, a fungicide, onto the virgin polymer materials polyamide (PA), polypropylene (PP), and polystyrene (PS). Additionally, PP was cryo-milled and PA was treated with acid to investigate the influence of an increase in surface area and chemical modification. The material properties were also studied by dynamic scanning calorimetry (DSC), gel permeation chromatography (GPC) and Fourier transform infrared spectroscopy (FTIR). Sorption experiments were performed on the basis of a full factorial design examining the effect of agitation, pH value, and salinity. Experimental results showed that difenoconazole sorbs readily to all microplastics, whereas the more polar analyte metformin did not show any affinity to the materials used. For difenoconazole the governing factor in all cases is agitation, while both pH and salinity exhibited only a slight influence. The modification of polymers leads to enhanced sorption, indicating that an increase in surface area (cryo-milled PP) or inner volume (acid-treated PA) strongly favours adsorption. Moreover, long-term experiments demonstrated that the time until equilibrium is reached depends strongly on the particle size.