Journal of Hazardous Materials 203–204 (2012) 46–52 Contents lists available at SciVerse ScienceDirect Journal of Hazardous Materials j our na l ho me p age: www.elsevier.com/locate/jhazmat Removal of nalidixic acid and its degradation products by an integrated MBR-ozonation system A. Pollice ∗ , G. Laera, D. Cassano, S. Diomede, A. Pinto, A. Lopez, G. Mascolo ∗∗ Istituto di Ricerca Sulle Acque, Consiglio Nazionale delle Ricerche, Viale F. De Blasio 5, 70132 Bari, Italy a r t i c l e i n f o Article history: Received 26 April 2011 Received in revised form 18 November 2011 Accepted 21 November 2011 Available online 7 December 2011 Keywords: Membrane bioreactor Ozonation Integrated process Pharmaceutical wastewater Salinity a b s t r a c t Chemical–biological degradation of a widely spread antibacterial (nalidixic acid) was successfully obtained by an integrated membrane bioreactor (MBR)-ozonation process. The composition of the treated solution simulated the wastewater from the production of the target pharmaceutical, featuring high salinity and a relevant concentration of sodium acetate. Aim of treatment integration was to exploit the synergistic effects of chemical oxidation and bioprocesses, by adopting the latter to remove most of the COD and the ozonation biodegradable products. Integration was achieved by placing ozonation in the recirculation stream of the bioreactor effluent. The recirculation flow rate was three-fold the MBR feed, and the performance of the integrated system was compared to the standard polishing configuration (single ozonation step after the MBR). Results showed that the introduction of the ozonation step did not cause relevant drawbacks to both biological and filtration processes. nalidixic acid passed undegraded through the MBR and was completely removed in the ozonation step. Complete degradation of most of the detected ozonation products was better achieved with the integrated MBR-ozonation process than using the sequential treatment configuration, i.e. ozone polishing after MBR, given the same ozone dosage. © 2011 Elsevier B.V. All rights reserved. 1. Introduction Wastewater from the pharmaceutical industry may contain chemicals that are unbiodegradable and/or potentially harmful for microbial consortia and environmental systems. Although these streams are usually treated separately (in-house), the produced effluents may still contain relatively large amounts of refrac- tory compounds that would affect the composition of municipal wastewater if discharged into the sewer or contaminate directly the aquatic environment if discharged without further treatments. To limit these effects, specific treatment approaches are needed for the removal of pharmaceuticals from industrial wastewater. Conventional biological processes often do not provide satisfactory results for the treatment of wastewater from the pharmaceuti- cal industry, due to the above mentioned scarce biodegradability or toxicity. An alternative treatment approach is the combination of advanced oxidation processes (AOPs) and biological treatments [1]. AOPs are well known for their capacity of partially or com- pletely mineralising organic contaminants, although their practical large scale applications are limited by their high costs, mainly due ∗ Corresponding author. Tel.: +39 080 5820531; fax: +39 080 5313365. ∗∗ Corresponding author. Tel.: +39 080 5820519; fax: +39 080 5313365. E-mail addresses: alfieri.pollice@ba.irsa.cnr.it (A. Pollice), giuseppe.mascolo@ba.irsa.cnr.it (G. Mascolo). to energy consumption (radiation, ozone, etc.) and the need of chemical reagents (catalysts and oxidizers) [2]. The combination of chemical and biological oxidation processes can be beneficial if the synergistic effects of these two types of treatment are exploited. Conventional applications of chemical oxidation processes as pre- treatments or final polishing are usually non-optimal from the point of view of process costs. Indeed the achievement of good treatment performances with these treatment trains often requires the adoption of highly intensive chemical oxidation steps [3–8]. A full integration of biological treatment and chemical oxida- tion may allow for both the limitation of the concentration of organic compounds undergoing chemical oxidation, and the bio- logical removal of the biodegradable oxidation products. Biological and chemical treatment integration can also be considered a safer “multiple barrier approach”, where the biological process limits the load of incoming compounds reaching the chemical oxidation pro- cess by removing the biodegradable fraction, and eliminates the biodegradable products resulting from this step. This approach had limited applications so far, and its potential is probably not com- pletely exploited yet [9]. In the present study, the integrated approach described above was adopted, and ozonation was placed in the effluent recirculation flow of a lab-scale membrane bioreactor (MBR) treating a solu- tion containing a commercial antibacterial compound (nalidixic acid) and simulating the wastewater produced in the drug’s pro- duction process. The same target compound was recently adopted 0304-3894/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.jhazmat.2011.11.072