Özet:
Though conventional biological treatment plants can remove the basic pollutants,
they are found to be ineffective in removing recalcitrant pollutants. Membrane
bioreactors are considered a promising technology by having advantages such as
higher effluent quality and producing low sludge in comparison to conventional
biological treatment processes. In this study, the elimination of pharmaceutical
compounds was investigated by membrane bioreactors under different solid
retention time (SRT). The effect of SRT on the elimination of emerging
pharmaceuticals was observed for 20, 30, and 40-day SRT and monitored for 96
days for each and, it was found that the 40-day SRT had the optimum performance
in terms of the pharmaceuticals’ elimination. Chemical oxygen demand (COD)
removal efficiencies for each selected SRT were higher than 96% at steady-state
conditions. The highest degradation efficiencies were observed for paracetamol,
and when it is sorted from the most removed compound towards the lowest, it can
be listed as Paracetamol, Ranitidine, Atenolol, Bezafibrate, Diclofenac, Carbamazepine. The
microbial community at the phylum level was also analyzed
to understand the biodegradability of pharmaceuticals. It was noticed that the
proteobacteria phylum increased from 46.8% to 60.0% after 96 days after adding
the pharmaceuticals. Actinobacteria class which can metabolize paracetamol,
carbamazepine, and atenolol was also increased from 9.1% to 17.9% after adding
pharmaceuticals. The by-products of diclofenac, bezafibrate, and carbamazepine
were observed in the effluent samples. The transmembrane pressure TMP was
monitored during the whole work period and it was observed that during the 20
day SRT phase, the fouling occurred much more often and faster for both 0.2 µm
and 0.45 µm membranes than the fouling occurred during the 30 and 40 day SRT
phases. This might be due to the increase in the values of SMP and EPS when
decreasing the SRT. The combination of MBR treatment to the NF270, NF90 and
RO membranes resulted in the removal of four pharmaceuticals (paracetamol,
ranitidine, atenolol, and bezafibrate) to below detection limits. In addition, it's
worth noting that when the BW30 was used in conjunction with the MBR
treatment, the removal efficiency for diclofenac and carbamazepine was higher
than other membrane combinations recording about 86% and 82% respectively.
