Bioremediation of metal contamination in the Plankenburg River, Western Cape, South Africa V.A. Jackson a , A.N. Paulse a , A.A. Bester c , J.H. Neethling a , S. Khan a , W. Khan b, * a Department of Biomedical Sciences, Faculty of Health and Wellness Sciences, Cape Peninsula University of Technology, Bellville 7535, South Africa b Department of Agricultural and Food Sciences, Faculty of Applied Science, Cape Peninsula University of Technology, Cape Town 8000, South Africa c Department of Chemical Engineering, Faculty of Engineering, Cape Peninsula University of Technology, Cape Town 8000, South Africa article info Article history: Received 8 December 2008 Received in revised form 10 March 2009 Accepted 11 March 2009 Available online 6 May 2009 Keywords: Bioreactor Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES) Metals Phylogeny River water abstract Three bioreactors (two laboratory-scale and one on-site) were evaluated for their efficiency to reduce metal concentrations in water collected from the Plankenburg River, South Africa. Water (bioreactors one, two and on-site) and bioballs (bioreactors two and on-site) collected throughout the study periods were digested and analysed using Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES). Aluminium (Al), nickel (Ni), and zinc (Zn) concentrations decreased from 0.41 mg l 1 to 0.06 mg l 1 (85%), 0.2 mg l 1 to 0.07 mg l 1 (65%) and 75 mg l 1 to 0.02 mg l 1 (97%), respectively (bioreactor one). Aluminium [(1.55–0.38 mg l 1 (75%)], copper (Cu) [57% (from 0.33 mg l 1 to 0.14 mg l 1 )], iron (Fe) [71.99–40.4 mg l 1 (44%)] and manganese (Mn) [57% (0.07–0.03 mg l 1 )] concentrations also decreased in the water samples from bioreactor two. In the on-site, six-tank bioreactor system, concentrations for Fe, Cu, Mn and Ni decreased, while Zn and Al concentrations increased. The concentrations recorded in biofilm samples were higher than the corresponding water samples. The bioballs employed in the bioreactor were thus shown to be efficient attachment surfaces for biofilm development and subsequent metal accumulation. Potentially metal-tolerant organisms (Pseudomonas sp., Sphingomonas sp., and Bacillus sp.) were also identified using phylogeny. Ó 2009 Elsevier Ltd. All rights reserved. 1. Introduction The quality and quantity of the essential element water is important for the continued sustenance of not only the world’s human population, but also for its application in industrial and agricultural sectors, amongst others. In South Africa, water resources are generally collected in dams or water abstraction schemes. These water sources are then primarily used for agricultural activities, industry, mining and power generation, domestic and municipal uses, with 15% of the available water resources required to maintain estuaries and rivers (Langwaldt and Puhakka, 2000). Pollution, by metals and microbes (Pegram et al., 1999), amongst others, greatly influences the quality of the water sources, and leads to the continued search for new and improved methods to not only clean up contaminated systems, but also to achieve this aim in an environmentally friendly and cost-effective manner. The ubiquitous nature of biofilms allows these viable and metabolically active micro-organisms (Ehrlich, 1998) to survive and proliferate in a variety of different environments, due to their protective polysaccharide coating. Biofilms have a high metal- binding capacity as toxicants are absorbed by cell surface polymers, or extracellular polymeric substances (EPS), which have been shown to be responsible for the interaction of toxicants with the biofilm community (Henriques and Love, 2007). Biofilms are thus applied in the effective remediation or removal of pollutants such as metals, from contaminated areas (Roane and Pepper, 2000). Bioremediation is a process by which microbial degradation processes are used in technical and controlled treatment systems (Langwaldt and Puhakka, 2000). Bioremediation can also be applied as green technologies, due to its negligible effects on the environment, and its proven cost-efficiency (Adriaens et al., 2006). Bioreactors, which can be applied in bioremediation strategies, are basically tanks in which living organisms carry out biological reactions. Their efficiency is based on the ability of bacteria to attach to inert packing, such as granular activated carbon, at interfaces to generate high biomass (Bouwer and McCarty, 1982; Teitzel and Parsek, 2003). The reactor should also be easy to maintain and operate (Evangelho et al., 2001; Teitzel and Parsek, 2003), and should be able to function under aerobic and anaerobic conditions (Langwaldt and Puhakka, 2000). * Corresponding author. Tel.: þ27 21 460 3175; fax: þ27 21 460 3193. E-mail address: khanw@cput.ac.za (W. Khan). Contents lists available at ScienceDirect International Biodeterioration & Biodegradation journal homepage: www.elsevier.com/locate/ibiod 0964-8305/$ – see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.ibiod.2009.03.007 International Biodeterioration & Biodegradation 63 (2009) 559–568