Pharmaceuticals removal and microbial community assessment in a continuous fungal treatment of non-sterile real hospital wastewater after a coagulation-flocculation pretreatment
Graphical abstract
Introduction
Pharmaceutical active compounds (PhACs) have been found in water bodies at significant concentrations (Gros et al., 2012). The primary source of these contaminants in the environment is known to be through wastewater treatment plant (WWTP) effluents, not designed to remove these emerging pollutants (Deblonde and Hartemann, 2013). PhACs are found at especially high concentrations (up to μg·L−1 and mg·L−1) in hospital wastewater (HWW), which is typically discharged untreated into the sewer network. In consequence, the on-site treatment of these hospital effluents prior to discharge has arisen as a promising possibility (Verlicchi et al., 2012). These recalcitrant compounds would be total or partially degraded and transformed into more degradable compounds for further downstream treatment.
White-rot fungi (WRF) have demonstrated the capability to degrade several PhACs and consequently, a fungal approach to treat on-site hospital effluents emerges as an attractive perspective. First studies on fungal treatment performance concerning pharmaceutical removal were carried out in sterile conditions and with single-spiked pollutants (Marco-Urrea et al., 2009, Marco-Urrea et al., 2010, Jelic et al., 2012). Studies in non-sterile more complex matrices are scarcer but have demonstrated the ability of fungi to transform and/or remove PhACs from non-sterile HWW (Cruz-Morató et al., 2013). One of the drawbacks of the technology in non-sterile conditions is the difficulty in maintaining the fungal activity for a long period of time since bacteria exert competitive pressure in fungal survival. The implementation of a coagulation-flocculation step before the fungal treatment of spiked HWW reduced the microbial load of the influent thus allowing the maintenance of fungal activity for 28 days (Mir-Tutusaus et al., 2016). Furthermore, a partial biomass renovation, previously described by Blánquez et al. (2006), could extend the treatment by overcoming the biomass aging process. This approach has been implemented and is discussed in the present manuscript. To approach a real application, a non-spiked matrix is preferred.
Additionally, despite some studies have investigated the bacterial and fungal communities in fungal bioreactors treating wastewater (Badia-Fabregat et al., 2015), it still remains unclear which microorganisms are responsible for the PhACs elimination. The assessment of microbial assemblage would enhance the knowledge about this type of systems and help in the design of future treatments.
This study provides the validation of previous work in spiked HWW (Mir-Tutusaus et al., 2016), while approaching real application. The main focus of the manuscript has been the discussion of PhACs removal and its relation to microbial community evolution. Moreover, a long operation of this kind of reactors in non-sterile HWW has never been achieved before and it would signify a promising step in the maturation of fungal technology in wastewater treatment. The objectives of the study are thus to test the ability of WRF Trametes versicolor to treat real non-sterile HWW after a coagulation-flocculation pretreatment for a long period of time, to evaluate the bacterial and fungal communities arisen during the treatment and to assess the removal efficiency for PhACs.
Section snippets
Reagents, fungus and hospital wastewater
All the pharmaceutical and the corresponding isotopically labelled standards used in the analysis were of high purity grade (>90%) and they were purchased from Sigma–Aldrich (Steinheim, Germany), US Pharmacopeia USP (MD, USA), Europea Pharmacopoeia EP (Strasbourg, France), Toronto Research Chemicals TRC (Ontario, Canada) and CDN isotopes (Quebec, Canada). Individual as well as isotopically labelled standard solutions were prepared according to Gros et al. (2012). Thiamine hydrochloride was
Results
The results of HWWs characterization (Table 1) show that the measured physicochemical parameters were in the same range as other HWW. Pharmaceuticals concentrations, presented in Table 2 ranged from ng·L−1 to few μg·L−1, results also in agreement with previous studies (Badia-Fabregat et al., 2015, Cruz-Morató et al., 2013). The pretreatment diminished the absorbance at 650 nm from 0.215 and 0.265 to values very close to zero and the COD from 633 and 1012 mg O2·L−1 to 215 and 300 mg O2·L−1,
Discussion
The consortia established in the reactors were well adapted to lower pH, as both reactors were controlled at pH 4.5, and to aerobic conditions, as the reactors were aerated. Differences in bacterial populations between RA and RB were due to the presence of pelleted fungal biomass (i.e. in RA, contrarily to RB, Firmicutes were present until Day 9 and Proteobacteria α were predominant from Day 42 onwards). Differences in removal percentages cannot be directly linked to laccase production, as RA
Conclusions
T. versicolor in pelleted morphology was maintained in a fungal reactor treating flocculated non-sterile real hospital wastewater for two months with an HRT of 3 d. A partial biomass renovation strategy was used to maintain T. versicolor activity throughout the treatment, with a CRT of 21 d. A DGGE and sequencing approach confirmed that T. versicolor survived during the whole treatment. Regardless, longer operations might be needed to achieve a steady community structure.
81 pharmaceutical
Acknowledgements
This work has been funded by the Spanish Ministry of Economy and Competitiveness (project CTM2013-48545-C2) and partly supported by the European Union through the European Regional Development Fund (ERDF) and the Generalitat de Catalunya (Consolidated Research Groups 2014-SGR-599, 2014-SGR-476 and 2014-SGR-291). The Department of Chemical, Biological and Environmental Engineering of UAB is member of the Xarxa de Referència en Biotecnologia de la Generalitat de Catalunya. J. A. Mir-Tutusaus and
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