Soil aquifer treatment of artificial wastewater under saturated conditions H.M.K. Essandoh a , C. Tizaoui b , M.H.A. Mohamed a, *, G. Amy c,d , D. Brdjanovic c a School of Engineering Design and Technology, University of Bradford, BD7 1DP, UK b College of Engineering, Swansea University, SA2 8PP, UK c UNESCO-IHE, Westvest 7, 2611 AX Delft, The Netherlands d Water Desalination and Reuse Center, King Abdullah University of Science and Technology, Thuwal 23955-6900, Saudi Arabia article info Article history: Received 23 November 2010 Received in revised form 18 May 2011 Accepted 23 May 2011 Available online 31 May 2011 Keywords: Chemical oxygen demand Hydraulic loading rate Mass loading rate Removal efficiency Soil aquifer treatment abstract A 2000 mm long saturated laboratory soil column was used to simulate soil aquifer treatment under saturated conditions to assess the removal of chemical and biochemical oxygen demand (COD and BOD), dissolved organic carbon (DOC), nitrogen and phos- phate, using high strength artificial wastewater. The removal rates were determined under a combination of constant hydraulic loading rates (HLR) and variable COD concentrations as well as variable HLR under a constant COD. Within the range of COD concentrations considered (42 mg L 1 e135 mg L 1 ) it was found that at fixed hydraulic loading rate, a decrease in the influent concentrations of dissolved organic carbon (DOC), biochemical oxygen demand (BOD), total nitrogen and phosphate improved their removal efficiencies. At the high COD concentrations applied residence times influenced the redox conditions in the soil column. Long residence times were detrimental to the removal process for COD, BOD and DOC as anoxic processes and sulphate reduction played an important role as electron acceptors. It was found that total COD mass loading within the range of 911 mg d 1 e1780 mg d 1 applied as low COD wastewater infiltrated coupled with short residence times would provide better effluent quality than the same mass applied as a COD with higher concentration at long residence times. The opposite was true for organic nitrogen where relatively high concentrations coupled with long residence time gave better removal efficiency. Crown Copyright ª 2011 Published by Elsevier Ltd. All rights reserved. 1. Introduction The importance of adequate sanitation as well as the availability of enough quantities of fresh water for human consumption and industrial and agricultural use cannot be underestimated as they play a vital role in maintaining a healthy livelihood and in the development of nations. As populations continue to increase with their associated problems of waste generation and increased contamination of surface and ground waters, pressure on available water resources is increasing. This, coupled with uneven distri- bution of water resources and periodic droughts around the world, has brought about the need for innovative sources of water supply and local conservation. Highly treated waste- water effluents from municipal wastewater treatment plants are therefore now increasingly being considered as a reliable source of water supply (Metcalf and Eddy et al., 2003). * Corresponding author. Tel.: þ44 (0)1274 233856; fax: þ44 (0)1274 234111. E-mail address: m.h.a.mohamed@bradford.ac.uk (M.H.A. Mohamed). Available at www.sciencedirect.com journal homepage: www.elsevier.com/locate/watres water research 45 (2011) 4211 e4226 0043-1354/$ e see front matter Crown Copyright ª 2011 Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.watres.2011.05.017