Performance of an aerobic granular sequencing batch reactor fed with wastewaters contaminated with Zn 2þ Ana P.G.C. Marques, Anouk F. Duque, Vânia S. Bessa, Raquel B.R. Mesquita, António O.S.S. Rangel, Paula M.L. Castro * CBQF e Centro de Biotecnologia e Química Fina, Laboratório Associado, Escola Superior de Biotecnologia, Universidade Católica Portuguesa/Porto, Rua Dr. António Bernardino de Almeida, 4200-072 Porto, Portugal article info Article history: Received 28 March 2013 Received in revised form 17 June 2013 Accepted 24 June 2013 Available online 20 July 2013 Keywords: Zinc Wastewater Sequencing batch reactor (SBR) Aerobic granular sludge (AGS) abstract The main aim of this study was to investigate the performance of an aerobic granular sludge sequencing batch reactor (AGS-SBR) receiving water streams supplied with different loads of Zn 2þ (50 and 100 mg L 1 ) during an operation of 866 cycles (ca. 109 days). When the metal was not fed, chemical oxygen demand (COD), PO 3 4 and NH þ 4 were efficiently removed, with efficiencies of 56, 23 and 72% respectively. DGGE profiles showed that Zn 2þ supply negatively affected the bacterial diversity and community structure of the granules. Consequently, the shock loadings with Zn 2þ , particularly at the higher levels (100 mg L 1 ), affected the nutrient removal in the AGS-SBR, although the reactor still generally complied with admissible legal values concerning organic matter, nitrogen and Zn. Simultaneous removal of PO 3 4 and TSS in such conditions needs further refining but the application of aerobic granular SBR in the treatment of Zn 2þ contaminated wastewaters seems viable. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction The selection of a wastewater treatment process depends mainly on the type of contaminants present in the wastewater. Wastewaters, especially those from industrial sources, may contain not only organic matter but also inorganic pollutants. Mining (production of acid mine drainage) and industrial (electroplating, metal processing, paint, plastics, alloys, batteries, etc.) activities are amongst the main processes of heavy metals (HM) contamination of water (Xu et al., 2004). The treatment of HM contaminated wastewaters before its release to the environment is very impor- tant as these pollutants are toxic, bioaccumulating in plants and animals, and contaminating the food chain. Conventional treat- ment of metal containing wastewater, generally involves physic- chemical processes, such as coagulation, flocculation and sedi- mentation (Lim et al., 2002). However, bioremediation of such contaminated wastewaters is a potential alternative, as it has been reported that a number of microorganisms can adsorb HM from water (Sirianuntapiboon and Hongsrisuwan, 2007). Additionally, the application of a biological treatment offers the opportunity to remove not only metals but the simultaneous degradation of the present organic matter. Aerobic granules are used as a novel technique for the biological treatment of wastewaters, and have confirmed to be more profi- cient for water treatment than the use of suspended activated sludge (de Bruin et al., 2004). Their compact and strong microbial structure, excellent settleability, due to better control of filamen- tous growth (Yu and Gu, 1996), as well as their high biomass retention, and tolerance to high organic loadings and to toxicity, allows their development in sequencing batch reactors (SBR) and renders their use an important tool for organic and inorganic pol- lutants removal from wastewaters (Adav et al., 2008). Aerobic granular sludge (AGS) is able to perform simultaneously diverse biological processes such as COD, P and N removal (de Kreuk et al., 2005). Only few studies focused on metal decontamination of waste- waters using aerobic granular sludge (Liu et al., 2002; Xu et al., 2004). There are reports on the use of anaerobic granular sludge in upflow anaerobic sludge blanket (UASB) (Mu et al., 2012) or flocular SBR (Sirianuntapiboon and Hongsrisuwan, 2007; Sorour and Sayed-Ahmed, 2003). Zheng et al. (2011) studied the effect of Zn in the characteristics of the granules of an aerobic granular sludge sequencing batch reactor (AGS-SBR), however, up to date and to our knowledge, there are no reports concerning the * Corresponding author. Tel.: þ351 22 558 00 59; fax: þ351 22 509 03 51. E-mail addresses: amarques@porto.ucp.pt (A.P.G.C. Marques), anoukduque@ gmail.com (A.F. Duque), vbessa@porto.ucp.pt (V.S. Bessa), rmesquita@porto.ucp.pt (R.B.R. Mesquita), arangel@porto.ucp.pt (A.O.S.S. Rangel), plcastro@porto.ucp.pt (P.M.L. Castro). Contents lists available at SciVerse ScienceDirect Journal of Environmental Management journal homepage: www.elsevier.com/locate/jenvman 0301-4797/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jenvman.2013.06.052 Journal of Environmental Management 128 (2013) 877e882