Water & Wastewater Asia Jul/Aug 2018

WATER & WASTEWATER ASIA July / August 2018 INSIGHT / 43 The Interreg 2 Seas DOC2C’s Programme The Interreg 2 Seas DOC2C’s project is an extensive research programme to investigate the possibility of improved dissolved organic carbon (DOC) removal from source waters in the European 2 Seas Area. Therefore, the DOC2C’s Consortium, consisting of PWNT (NL), South West Water (UK), De Watergroep (BE), Lille University (FR) and Delft University of Technology (NL) received a grant from the Interreg 2 Seas Programme to significantly improve and accelerate innovation in drinking water treatment by collaboration within the 2 Seas area. This project is co-financed by the Dutch Government, the Province of North Holland (NL) and the Province of West Flandres (BE). The DOC2C’s project will cover a period of four years. SIX ® is one of the water treatment technologies that can be considered to reduce DOC effectively. The SIX ® -process: Basic principle In the SIX ® process, resin is dosed from a dosing tank into the raw water at a low concentration of four to 20ml resin/L, depending on the raw water quality, desired treated water quality, and resin type. This mixture then flows through the plug flow contactors where the resin has the same residence time as the treated water; because the resin travels together with the water through these contactors. Unlike packed bed systems in which the resin is retained in the contactors, all resin particles are exposed to equal conditions, leading to homogeneous distribution of the adsorbed matter over these particles. This gives rise to a more stable and superior process performance as well as more efficient use of the counter anion (Cl-) during regeneration. The number, shape, and design of the contactors play an important role in the adsorption kinetics of this process. The aim of design is to approach the ideal contactor system of a plug-flow reactor [Ramaswamy, 1995], leading to shorter residence time of the resin, and therefore, shorter contact times. After the contact time in the contactors, the resin is separated from the treated water using a customised lamella settler. The resin collects in the hopper and is immediately regenerated and returned to the dosing tank (see Figure 2). Knowing the exact residence time of the resin makes it possible to regenerate all of the resin equally — leading to an equally low number of regenerations. The relatively short contact time (e.g., 10 minutes < t < 30 minutes) of the treated water with the resin before the regeneration procedure makes it difficult and almost impossible for bacteria to grow on the resin particles surface. This overcomes the problem of resin blinding and ensures that the resin continues to operate at stable adsorption kinetics. This is shown with the help of a pseudo first-order reaction according to Lagergren, for which reaction constants can be determined using jar tests (Koreman 2013). Since 2014, several studies have been conducted with this new process on several sites or utilities in Europe. For instance, the studies were conducted with South West Water (UK), Scottish Water (UK), Stockholm Water and Waste VA (S), Norrvatten (S), Welsh Water (WW, UK), Anglian Water (AW, UK) and PWN (the Netherlands) to investigate the initial feasibility of the SIX ® process. It was concluded that suspended ion exchange SIX ® resulted in substantial removal of NOM (55 – 85 per cent) and colour (60 – 80 per cent) for moderate resin concentrations (10 – 20 mL/L) and contact times (20 – 40 minutes). The scenario of SIX ® , in combination with coagulation can be considered a serious DOC reduction option for utilities facing challenges. The process already led to full-scale design at PWN and South West Water and to serious full-scale consideration for Stockholm Vatten, Norrvatten and Scottish Water. WWA SIX ® is a registered trademark licensed to PWNT B.V. References: • Slunjski M, M. Bourke, H. Nguyen, M. Ballard, J. Morran, D. Bursill, (1999) MIEX ® DOC Process – A New Ion Exchange Process Presented at the 18th Federal AU Water Association Convention 1999, Adelaide, Australia • Verdickt, L., Closset, W., D’Haeseleer, V., Cromphout, J. (2011). Applicability of ion exchange for NOM removal from a sulphate rich surface water incorporating full reuse of the brine, proceedings IWA NOM conference 2011, Los Angeles, CA, USA • Galjaard G., Kamp P.C., Koreman E. (2009), SIX ® : A new resin treatment technology for drinking water, proceedings Singapore International Water Week 2009, Singapore • Ramaswamy H.S., Abdelrahim K.A., Simpson B.K., Smith J.P. (1995). “Residence time distribution (RTD) in aseptic processing of particulate foods: a review”. Food Research International, 28 (3), 291-310.