Contents lists available at ScienceDirect International Biodeterioration & Biodegradation journal homepage: www.elsevier.com/locate/ibiod Pilot-scale operation experience of anaerobic Co-digestion for possible full scale implementation Richard Wickham a , Sihuang Xie a , Brendan Galway b , Heriberto Bustamante b , Long D. Nghiem c,d,* a Strategic Water Infrastructure Laboratory, School of Civil Mining and Environmental Engineering, University of Wollongong, Wollongong, NSW, 2522, Australia b Sydney Water, Parramatta, NSW, 2124, Australia c Centre for Technology in Water and Wastewater, University of Technology Sydney, Ultimo, NSW, 2007, Australia d NTT Institute of Hi-Technology, Nguyen Tat Thanh University, Ho Chi Minh City, Viet Nam ARTICLE INFO Keywords: Anaerobic co-digestion Sewage sludge Beverage waste Biogas Organic loading rate Digestate quality ABSTRACT Anaerobic co-digestion of sewage sludge with four beverage wastes (namely beer, soft drink, fruit juice, and wine) was evaluated using a dedicated pilot research plant. Temporal variation in the sludge's organic content highlighted the importance of using a mono-digestion control reactor for a systematic comparison with co- digestion. Results indicate that chemical oxygen demand (COD) is a better parameter compared to volatile solids (VS) for determining the organic loading rate during co-digestion with beverage waste that contain solubilised organic carbon. In this study, all beverage wastes investigated here (with the exception of wine) were suitable for co-digestion. H 2 S content in biogas decreased during co-digestion, possibly due to the dilution effect by the additional biogas generated from sulphur-lean organic rich waste. Results from this study show that the organic content in most beverage waste can be readily and completely converted to biogas. At 10% substrate addition (v/ v) beer, soft drink and juice addition did not observably affect total COD and VS in the digestate, whilst in- creasing biomethane production relative to the control by 39, 41 and 64% respectively. Furthermore, the in- terchanging of co-substrates did not result in any observable impact on digestion performance. Further in- vestigation is recommended to ascertain the low performance of wine waste co-digestion with sewage sludge. 1. Introduction Anaerobic digestion involves several biological transformation steps in which microorganisms break down biodegradable materials in the absence of oxygen to produce biogas and stable solid residues. Biogas (specifically the biomethane) can be utilised to generate electricity and heat, while solid residues can be beneficially reused for land applica- tions. As a mature technology, anaerobic digestion has been deployed for a range of applications including the treatment of sewage sludge, landfill leachate, food waste, livestock manure, and agriculture residues (Begum et al., 2018; Jeong et al., 2019; Nghiem et al., 2017b; Tuyet et al., 2016; Xie et al., 2017). In recent years, a new approach known as co-digestion has been explored and applied to cater for a wider range of organic wastes (Xie et al., 2018). Co-digestion refers to the utilisation of two or more compatible organic substrates in the anaerobic digestion process (Jabeen et al., 2015; Liu et al., 2016; Ratanatamskul and Manpetch, 2016; Xie et al., 2017). Improvements in anaerobic digestion performance in terms of the specific methane yield can occur by balancing the key stoichiometric parameters (e.g. C/N ratio), the provision of sufficient micronutrients and the dilution of inhibitors as a result of co-substrate addition (Mata-Alvarez et al., 2014). Co-digestion has been successfully at wastewater treatment plants (WWTPs) to increase biomethane pro- duction for subsequent energy generation and divert organic waste away from landfill (Xie et al., 2017), however, the rate of uptake is still slow due to uncertainty over potential impact on plant operation and biosolids processing. Co-digestion within municipal WWTPs is an attractive option as existing anaerobic digestion infrastructure can be utilised without sig- nificant capital investment (Nghiem et al., 2017a). Sewage sludge usually has low organic carbon content but can produce a high alkaline buffering capacity to maintain stable anaerobic digestion operation. Thus, co-substrates adopted for co-digestion with sewage sludge are typically carbonaceous and higher in organic content (Koch et al., 2016). Adopting co-digestion allows WWTPs to increase biomethane pro- duction for electricity generation via gas combustion to offset their energy consumption and reduce the carbon foot print of wastewater https://doi.org/10.1016/j.ibiod.2019.05.020 Received 9 March 2019; Received in revised form 15 May 2019; Accepted 15 May 2019 * Corresponding author. Centre for Technology in Water and Wastewater, University of Technology Sydney, Ultimo, NSW 2007, Australia. E-mail address: duclong.nghiem@uts.edu.au (L.D. Nghiem). International Biodeterioration & Biodegradation 142 (2019) 137–142 0964-8305/ Crown Copyright © 2019 Published by Elsevier Ltd. All rights reserved. T