The effect of electrodialytic treatment and Na 2 H 2 EDTA addition on methanogenic activity of copper-amended anaerobic granular sludge: Treatment costs and energy consumption Jurate Virkutyte a,⇑ , Ekaterina Rokhina a , Piet Lens b , Veeriah Jegatheesan c a Department of Environmental Sciences, University of Eastern Finland, Yliopistonranta 1E, 70211 Kuopio, Finland b UNESCO-IHE, Department of Environmental Resources, PO Box 3015, 2601 DA Delft, The Netherlands c School of Engineering and Physical Sciences, James Cook University, Townsville, QLD 4811, Australia article info Article history: Received 25 July 2010 Received in revised form 12 October 2010 Accepted 15 October 2010 Available online 20 October 2010 Keywords: Electrodialysis Methanogenic activity Anaerobic granular sludge Energy consumption abstract The effect of electrodialytic treatment in terms of a current density, pH and Na 2 H 2 EDTA addition on the methanogenic activity of copper-amended anaerobic granular sludge taken from the UASB reactor from paper mill was evaluated. Moreover, the specific energy consumption and simplified operational and treatment costs were calculated. Addition of Na 2 H 2 EDTA (at pH 7.7) to copper-amended sludge resulted in the highest microbial activity (62 mg CH 4 -COD g VSS 1 day 1 ) suggesting that Na 2 H 2 EDTA decreased the toxic effects of copper on the methanogenic activity of the anaerobic granular sludge. The highest methane production (159 %) was also observed upon Na 2 H 2 EDTA addition and simultaneous electricity application (pH 7.7). The energy consumption during the treatment was 560, 840, 1400 and 1680 kW h m 3 at current densities of 0.23, 0.34, 0.57 and 0.69 mA cm 2 , respectively. This corresponded to a treatment costs in terms of electricity expenditure from 39.2 to 117.6 € per cubic meter of sludge. Ó 2010 Elsevier Ltd. All rights reserved. 1. Introduction Sludge management is a serious problem that requires the use of appropriate remediation technologies, especially if the sludge contains significant amount of xenobiotic components, noxious substances and heavy metals (Virkutyte et al., 2005). Sludge has a reuse potential in different fields such as fertilizers, organic matter and biogas production (Ferri et al., 2009). Methanogenic anaerobic digestion is one of the most economically viable tech- niques for biogas production (Zinatizadeh et al., 2009). Therefore the maintenance of a sufficient methanogenic population in anaer- obic digesters is vital for its performance. Methanogenic species types and their relative population levels in sludge depend on the wastewater and sludge characteristics as well as the opera- tional/environmental conditions maintained. Any imposed stress such as change in pH, accumulation of heavy metals, etc. may lead to a change in species types and their relative population levels, which is ultimately reflected in the reactor performance. Electrokinetic/electrodialytic processes are widely used for soil (Virkutyte et al., 2004), sediments (Virkutyte and Sillanpaa, 2007), water and wastewater (Ferri et al., 2009; Virkutyte et al., 2010) remediation. This method uses direct low-level electric current as the ‘‘cleaning agent’’, combining the electrokinetic movement of ions towards appropriately charged electrodes in the matrix where they form enriched solutions or are reduced to form a deposit on the electrode (Xiu and Zhang, 2009). Also, electric current in combination with microorganisms may be utilized for hydrogen production at the biocathode (Rozendal et al., 2008). Thus, electro- dialytic methods have a potential to be used to generate electricity while simultaneously treating contaminated sludge. Sludge applied to soils as fertilizer often contains a range of var- ious metals and plant nutrients. Some metals, such as Cu, Ni and Zn are essential micro-nutrients for plants and microorganisms, how- ever, these micro-nutrients may be toxic at higher concentrations (Virkutyte et al., 2005). To extract metals from sludge, Na 2 H 2 EDTA is often used as the chelating agent, since it forms strong complexes with most heavy metals and is relatively inexpensive (about 1.3 € kg 1 ) compared to other chelating agents (Pociecha and Lestan, 2009). Herein we evaluate the effect of electrodialytic treatment of anaerobic sludge with a potential to produce biogas. This was done by evaluating current density, pH, addition of Cu 2+ and Na 2- H 2 EDTA on the specific methanogenic activity of anaerobic granular sludge. The specific energy consumption during the elec- trodialytic process and simplified treatment costs were also addressed in the technology assessment. 0960-8524/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.biortech.2010.10.067 ⇑ Corresponding author. Present address: US Environmental Protection Agency, National Risk Management Research Laboratory, Sustainable Technology Division, 26 West Martin Luther King Drive, MS 419, Cincinnati, OH 45268, USA. Tel.: +1 513 569 7964; fax: +1 513 569 7677. E-mail address: Virkutyte.Jurate@epa.gov (J. Virkutyte). Bioresource Technology 102 (2011) 5541–5544 Contents lists available at ScienceDirect Bioresource Technology journal homepage: www.elsevier.com/locate/biortech