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Removal of typical pharmaceutically active compounds in sewage sludge using mesophilic and thermophilic anaerobic digestion processes
Zhou, Haidong; Zhou, Jiaoyan; Wang, Meng; Wang, Xuelian; Zhang, Qianqian; Zhang, Qingjun & Zhan, Yong
Abstract
The removal of four pharmaceutically active
compounds, i.e., anti-inflammatory painkiller diclofenac
(DCF), lipid-regulating agent clofibric acid (CFA), epilepsy
drugs carbamazepine (CBM), and broad-spectrum
anti-bacterial agent triclosan (TCS), present in sewage
sludge was investigated using anaerobic digestion processes
in the mesophilic and thermophilic modes. Sludge
retention times (SRTs) were set at 10, 15, and 20 days,
respectively, for the mesophilic mode and 7, 15, and
20 days, respectively, for the thermophilic mode. The
effective isolation and purification pre-treatment to extract
the target compounds from the sewage sludge samples
were firstly established, followed by gas chromatography–
mass spectrometer analysis to identify and quantify them.
The removal efficiencies of the target compounds could be
raised to a certain extent with the increase on SRTs,
especially under the mesophilic condition. The removal of
CFA and TCS under thermophilic condition hardly varied
when the SRTs were above 15 days. All the compounds
could be partly removed from the sewage sludge under the
two temperature conditions, particularly TCS that was
reduced by about 74 %. Besides, CFA, firstly reported in
this study, could be reduced by maximal 65 %. On the
whole, the thermophilic mode was more conducive to the
removal of CBM and TCS, but did not have a noticeable
effect on the removal of CFA. Furthermore, DCF could be
better removed in the mesophilic mode. In addition,
NH3–N accumulation in this measured range might positively
affect the removal of the selected compounds, particularly
in the mesophilic mode.
Keywords
Removal efficiency; Sludge retention time; Mesophilic anaerobic digestion; Ammonia nitrogen
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