Characterization of the extracellular polymeric substances and microbial community of aerobic granulation sludge exposed to cefalexin
Introduction
Pharmaceuticals are used extensively to treat diseases in humans and animals. The growing occurrence of residues of human and veterinary pharmaceuticals, such as antibiotics, in the environment is causing increasing concern (Sarmah et al., 2006). The major sources of antibiotic residues in the environment include wastewater from hospitals, households, livestock farming, and pharmaceutical factories. Wastewater can contain extremely complex mixtures of various antibiotics and other drugs, such as cefalexin (CLX), chloramphenicol (CHL), carbamazepine (CAR), ibuprofen (IBU), and naproxen (NAP) (Sui et al., 2010, Krkošek et al., 2014). These kinds of pharmaceuticals can reach wastewater treatment plants (WWTPs) from different routes and are usually detected at levels ranging from ng L−1 up to mg L−1 not only in domestic and hospital effluents but also in effluents of pharmaceutical manufacturing facilities, which can present higher levels, reaching concentrations up to the mg L−1 range (Lin et al., 2009, Yang et al., 2014).
Cefalexin is one of the most prescribed antibiotics and is produced in great quantities, as indicated by its frequent occurrence and high concentrations in municipal sewage treatment plant influents (Evgenidou et al., 2015). Common wastewater treatments such as conventional activated sludge systems are unable to remove pharmaceuticals and personal care products efficiently (Zhou et al., 2009). Although relatively higher removal efficiencies of CLX were observed after treatment in an activated sludge system, the presence of CLX in effluents is a clear indication that CLX cannot be removed completely in current sewage treatment plant processes (Liu et al., 2011, Liu et al., 2012). Previous studies have already shown that aerobic granular sludge is extremely promising for the treatment of effluents containing toxic compounds (Miao et al., 2014). Compared with conventional activated sludge, the aerobic granulation sludge is less sensitive to fluctuation than activated sludge, due to a higher tolerance to toxicity as well as a higher biomass concentration. To date, treatment of wastewater containing CLX has been reported using physical–chemical processes such as the electro-Fenton oxidation process and sorption processes (Ledezma Estrada et al., 2012). However, there is limited information available on the interaction of CLX and aerobic granulation sludge.
The limited literature available seems to indicate that when aerobic granulation sludge is used for removal of antibiotics, sorption is an important mechanism due to the porosity and high amount of surface area; initial adsorption onto the surface is followed by intra-particle diffusion (Shi et al., 2011). The production of EPS is a response to the stress situation. Extracellular polymeric substances (EPS) secreted by cells could contribute to the adhesion, promoting microbial aggregation and the formation of matrix structure, and enhancing the communication between cells and the stability of granules (Kong et al., 2014). Characterization of EPS contents and components of aerobic granules exposed to CLX has not been carried out previously. In addition, microbes responsible for degradation and the toxicity of CLX on those microbes should be investigated, as should the qualitative and quantitative changes to the microbial community structure when using aerobic granulation technology to remove CLX and their effect on the granules.
The aim of this study was to evaluate the removal of CLX using aerobic granulation technology. The effect of CLX on COD and nitrogen removal was investigated. Additionally, changes in EPS and the characterization of microbes in aerobic granular sludge exposed to CLX were also evaluated with three-dimensional excitation–emission matrix (3D-EEM) and high-throughput sequencing techniques, respectively.
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Experimental setup and operation
Two double-walled cylindrical column sequencing batch airlift reactors (SBARs) in parallel with a height of 100 cm and internal diameter of 8 cm were used in this study. The SBARs contained an internal riser with a height of 80 cm, internal diameter of 5 cm, and bottom clearance of 1.5 cm. A detailed description of the SBARs was given in Kong et al. (2013). The SBARs were operated in 6 h successive cycles with 10 min of influent filling, 310 min of aeration, and 5 min of settling, plus 5 min of
Aerobic granule size distribution
The environmental concentration of CLX was very low in seawater, coastal water, municipal wastewater, and sewage effluents (from 6.1 ng L−1 to 5070 ng L−1) (Gulkowska et al., 2007, Li et al., 2009, Minh et al., 2009), but non-negligible concentrations were also found in the effluent concentration from a cephalosporin factory in India after treatment; this value was approximately 29 mg L−1 (Saravanane and Sundararaman, 2009). According to the pretest data, the concentration of 20 mg L−1 was
Conclusions
The presence of cefalexin (CLX) potentially decreased granular stabilities, resulting in a decreased granule diameter. Chemical oxygen demand and –N removal efficiencies were slightly decreased and the denitrification process was inhibited with the addition of CLX. The CLX removal efficiency was 76.7 ± 4.9% in the SBAR exposed to CLX. The EPS contents were significantly increased and EPS components were changed in aerobic granules exposed to CLX. High-throughput sequencing analysis showed
Acknowledgments
This work was supported by the Project funded by China Postdoctoral Science Foundation (No. 2014M551950), the Promotive research fund for excellent young and middle-aged scientists of Shandong Province (No. BS2014HZ019) and the Major Science and Technology Program for Water Pollution Control and Treatment (2012ZX07203004 and 2015ZX07203005).
References (32)
- et al.
Understanding the removal mechanisms of PPCPs and the influence of main technological parameters in anaerobic UASB and aerobic CAS reactors
J. Hazard. Mater.
(2014) - et al.
Performance of aerobic granular sludge in a sequencing batch bioreactor exposed to ofloxacin, norfloxacin and ciprofloxacin
Water Res.
(2014) - et al.
Occurrence and removal of transformation products of PPCPs and illicit drugs in wastewaters: a review
Sci. Total Environ.
(2015) - et al.
Extraction of extracellular polymers from activated sludge using a cation exchange resin
Water Res.
(1996) - et al.
The occurrence of selected antibiotics in Hong Kong coastal waters
Mar. Pollut. Bull.
(2007) - et al.
Enhancement of aerobic granulation by zero-valent iron in sequencing batch airlift reactor
J. Hazard. Mater.
(2014) - et al.
Nitrous oxide emission in an aerobic granulation sequencing batch airlift reactor at ambient temperatures
Int. Biodeterior. Biodegr.
(2013) - et al.
Removal of acidic pharmaceuticals within a nitrifying recirculating biofilter
J. Hazard. Mater.
(2014) - et al.
A simple and low cost technique for determining the granulometry of upflow anaerobic sludge blanket reactor sludge
Water Sci. Technol.
(1999) - et al.
Biodegradability enhancement of wastewater containing cefalexin by means of the electro-Fenton oxidation process
J. Hazard. Mater.
(2012)
Rapid analysis of 21 antibiotics of multiple classes in municipal wastewater using ultra performance liquid chromatography-tandem mass spectrometry
Anal. Chim. Acta
Surface properties of sludge and their role in bioflocculation and settleability
Water Res.
Removal of pharmaceuticals in secondary wastewater treatment processes in Taiwan
J. Hazard. Mater.
Removal of cephalexin from aqueous solutions by original and Cu(II)/Fe(III) impregnated activated carbons developed from lotus stalks kinetics and equilibrium studies
J. Hazard. Mater.
Development and characterization of the 2,4,6-trichlorophenol (2,4,6-TCP) aerobic degrading granules in sequencing batch airlift reactor
Int. Biodeterior. Biodegr.
Antibiotics in the Hong Kong metropolitan area: ubiquitous distribution and fate in Victoria Harbour
Mar. Pollut. Bull.
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