Applicability of ion exchange for NOM removal from a sulfate-rich surface water incorporating full reuse of the brine

Abstract

The raw water of water treatment works ‘the Blankaart’ (Belgium) is characterized by high levels of NOM (Natural Organic Matter), alkalinity and sulfate. From 2006 until present, the possibility of applying fluidized ion exchange for NOM removal has been investigated at the plant. Pilot testing using Miex® (Magnetic Ion Exchange) resin demonstrated that under standard operating conditions, a TOC (Total Organic Carbon) removal efficiency of 40 to 50% can be achieved. Moreover, jar tests demonstrated that the application of ion exchange as a pretreatment for enhanced coagulation would allow the coagulant dose to be reduced by 60% without compromising effluent quality. Finally, column experiments were conducted to evaluate (i) the effect of full brine reuse and (ii) the possibility of using less expensive conventional ion exchange resins instead of the patented Miex® resin. Recuperation of the waste brine after flocculation with a ferric salt and dewatering was found to have no significant impact on the NOM removal efficiency. Column experiments with Miex® and conventional type 1 anion exchange resins revealed that the fluidization characteristics of both types of resin allow use in fluidized bed systems and that with both types of resin, similar NOM removal efficiencies can be attained. However, higher contact times are required when conventional resins are applied.

NOM-removal by the SIX®-process

“…This may explain why the process has been called high-rate. The hydraulic residence time and contact time of the water may be short (although not confirmed in the literature) compared to the dual-stage process, but the resin inventory and residence time until regeneration are much larger (Verdickt et al 2011).…”

“…Only a very small amount (∼0.1%) of the resin is pumped to regeneration vessel while, at the same time, regenerated resin is pumped into the contactors. From the available literature on the high-rate MIEX ® process (Verdickt et al 2011) it is not exactly clear how much resin is pumped to the regeneration system over the course of time, as the 0.1% of the total resin is being regenerated without a direct correlation to time or capacity. Based on the information reported by end users and customers, one concludes that the effective resin concentration in the process is between 1 to 2.5 mL/L.…”

“…The biofilm formed on the resin 'blinds' the active sites of the resin, resulting in serious operational and performance challenges. In addition, the loss of adsorption capacity (Wachiniski 2006) requires a higher resin concentration or longer contact time (Cornelissen et al 2009;Verdickt et al 2011); factors which increase the operational costs and/or lower the plant capacity. Another real problem is that eventually the biofilm releases organic matter or adenosine triphosphate, both known to be detrimental to downstream water treatment processes, particularly to membranes (Cornelissen et al 2010).…”

Removal of disinfection by-product precursors by ion exchange resins

“…Due to the combination of high DOC concentration and relatively high alkalinity, the water requires large amounts of coagulant and sulfuric acid during coagulation. 24 The four resins tested were Purolite PPA860S, Dowex TAN-1, Amberlite IRA-958 and Amberlite IRA-410. The three first mentioned resins are strong base anion type I resins with a quaternary ammonium group, and the last one is a strong base type II resin where a methyl group is replaced with an alcohol group.…”

Towards Water, Sodium Chloride and Natural Organic Matter Recovery from Ion Exchange Spent Brine

“…To date, only a few studies addressed the management of the spent brine generated by an IX process intended for NOM removal. A number of researchers suggested reducing the annual generation of the IX spent brine by recycling and reusing it several times prior to its disposal [ 5 , 6 , 7 ]. Even though this seems, in theory, to be an inexpensive strategy that can decrease the volume of the IX spent brine and NaCl consumption [ 5 , 6 , 8 ], the ability of the spent brine to regenerate the exhausted resins would diminish after a few cycles [ 7 ].…”