Article pubs.acs.org/est
Removal of Organics and Degradation Products from Industrial Wastewater by a Membrane Bioreactor Integrated with Ozone or UV/ H2O2 Treatment G. Laera,† D. Cassano,† A. Lopez,† A. Pinto,† A. Pollice,†,* G. Ricco,‡ and G. Mascolo†,* †
Istituto di Ricerca Sulle Acque, Consiglio Nazionale delle Ricerche, Viale F. De Blasio 5, 70132 bari, Italy ARPA Puglia, Laboratorio di Biologia delle Acque, Via Oberdan 16, 70121 bari, Italy
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S Supporting Information *
ABSTRACT: The treatment of a pharmaceutical wastewater resulting from the production of an antibacterial drug (nalidixic acid) was investigated employing a membrane bioreactor (MBR) integrated with either ozonation or UV/H2O2 process. This was achieved by placing chemical oxidation in the recirculation stream of the MBR. A conventional configuration with chemical oxidation as polishing for the MBR effluent was also tested as a reference. The synergistic effect of MBR when integrated with chemical oxidation was assessed by monitoring (i) the main wastewater characteristics, (ii) the concentration of nalidixic acid, (iii) the 48 organics identified in the raw wastewater and (iv) the 55 degradation products identified during wastewater treatment. Results showed that MBR integration with ozonation or UV/H2O2 did not cause relevant drawbacks to both biological and filtration processes, with COD removal rates in the range 85−95%. Nalidixic acid passed undegraded through the MBR and was completely removed in the chemical oxidation step. Although the polishing configuration appeared to give better performances than the integrated system in removing 15 out of 48 secondary organics while similar removals were obtained for 19 other compounds. The benefit of the integrated system was however evident for the removal of the degradation products. Indeed, the integrated system allowed higher removals for 34 out of 55 degradation products while for only 4 compounds the polishing configuration gave better performance. Overall, results showed the effectiveness of the integrated treatment with both ozone and UV/H2O2.
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costs due to intensive use of energy and chemical reagents.12 A sequential treatment of biological and solar-based AOP has been proposed for minimizing the operating costs.13,14 Indeed, ozone and AOPs can be used as a pre- or postbiological treatment. Post-treatments have been proved useful in the case of wastewaters containing large amounts of biodegradable organics and small concentrations of recalcitrant compounds. On the contrary, pretreatments result advisible when the amount of bioresistant contaminants is greater than that of biodegradable matter.8,15,16 All approaches involving chemical oxidation as a final polishing step would not avoid the presence of degradation products in the effluent, unless reaching the complete mineralization, with unsustainable treatment costs and time. An alternative method is proposed here, based on the integration of biological treatment and chemical oxidation by placing the latter in the effluent recirculation stream. The objective is to limit the concentration of organic compounds
INTRODUCTION Pharmaceutical production processes normally involve different steps of purification and separation where large volumes of wastewater are produced. This stream can have significant environmental impacts on the receiving water bodies including aquatic toxicity, the development of resistance in pathogenic bacteria and genotoxicity,1,2 also depending on the nature of the manufactured compounds (e.g., antibiotics vs probiotics). In any case these process waters require separate treatment before being discharged into the sewer or disposed of in the natural environment. Indeed, the limitations of conventional wastewater treatment systems toward the removal of pharmaceutical compounds were extensively investigated and several papers reports the inhibitory effects of pharmaceuticals on the bacterial communities in activated sludge plants.3−5 It follows that specific treatment methodologies are required for pharmaceutical wastewater. The combination of ozone or advanced oxidation processes (AOPs) and biological treatments is a possible approach for the treatment of such a wastewater that is often recalcitrant to biological treatment.6−8 Ozone and AOPs are well-known for their capacity of mineralizing pharmaceuticals and organic contaminants.9−11 However, their practical applications are limited by their high © 2011 American Chemical Society
Received: Revised: Accepted: Published: 1010
August 4, 2011 November 23, 2011 December 3, 2011 December 3, 2011 dx.doi.org/10.1021/es202707w | Environ. Sci. Technol. 2012, 46, 1010−1018
Environmental Science & Technology
Article
Table 1. Chemical Composition of Raw Wastewater, Average Chemical Parameters in the MBR Effluent (Sampling Point 3 in Figure 1) and Average Biomass Parameters in the MBR before and after the Introduction of the Oxidation Step (By Ozonation or UV/H2O2) in the Integrated Systema effluent parameter
unit
raw wastewater
MBR
4 7 2000b 620
