In this case study, high sensitivity simple methods for the analysis of trihalomethanes (THM4), iodinated-trihalomethanes (I-THMs), haloacetic acids (HAAs), bromide, iodide and iodate have been developed. A one-step procedure for the analysis of haloacetic acids by head-space GC-MS provides good reproducibility and low limits of quantification (≤ 50 ng L-1). These methods were applied to characterize the formation of DBPs in a full scale drinking water treatment plant. In this treatment plant, the incorporation of bromine into THMs increases throughout the water treatment line, due to the formation of bromine reactive species favored by the decrease of competition between DOC and bromide towards chlorine. A linear correlation has been observed between the bromine incorporation factor and the Br-/DOC mass ratio. The conversion of iodine to iodate by chlorination occurs in this water due to the relatively high bromide concentration. Moreover, a higher formation of iodate compared to iodide levels in the raw water is observed indicating a degradation of organic iodinated compounds. The formation of I-THMs was constant in terms of quantity and speciation between campaigns despite fluctuating concentrations of DOC and total iodine in the raw water. A preferential 2 removal of DBPs formed by the intermediate chlorination in the order I-DBPs>Br-DBPs>Cl-DBPs occurs during the subsequent activated carbon filtration. The removal rates range from 25 to 36% for the regulated THM4, from 82 to 93% for the ∑I-THMs and 95% for haloacetic acids. The assessment of the relative toxicity shows that despite a much lower concentration of HAAs (less than 10% of the total mass of measured DBPs) compared to THMs, these compounds are responsible for 75% of the relative cytotoxicity of the treated water. Bromoacetic acid on its own accounts for more than 60% of the overall toxicity of the 17 compounds included in this study.

The removal of dissolved organic carbon (DOC) is a key factor in the control of disinfection by-product (DBP) formation in drinking water. Ion exchange process deals with the removal of naturally negatively charged organic matter. A fluidized bed column test has been chosen to test in parallel the efficiency of 4 different anionic exchange resins (Purolite PPA860S, Dowex TAN-1, Amberlite IRA-958 and IRA-410) in terms of DOC fraction removal and related DBP formation reduction. IRA-410 was shown to be the best performing resin in terms of DOC and DBP formation potential reduction followed by PPA860S. These resins removed respectively 41 and 37% of DOC, with humic substances as the main target of the two resins (68 and 72% reduction, respectively, based on size exclusion chromatography with an organic carbon detector). The UV absorbance was reduced in a higher proportion than the DOC demonstrating a preference of the resins for the relatively hydrophobic compounds. The reduction in trihalomethane and haloacetic acid formation was higher than the DOC removal for IRA-410 and PPA860S (53 and 59%, respectively); whereas IRA-958 on the other hand showed a lower reduction in DBP formation potential than its DOC removal. All the resins showed a much higher reduction of iodinated trihalomethanes formation potential (66 to 96% reduction compared to raw water) due to the removals of iodide in addition of organic precursors. However, in a context of increasing halide concentrations, the different resins showed a reduction of their efficiency to control the formation of DBPs.

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.

In the search for a reliable but simple model for the biodegradation processes of an activated sludge wastewater treatment plant, this paper presents a multi-model which is valid for the global operating region of a standard carbon and nitrogen removing facility. In a first step, locally valid linear models are derived. Two linearization procedures are compared. The first procedure is the classical Taylor series expansion, while the second is a newly developed linearization procedure based on weighted linear combinations. In a second step, the locally valid models are combined to obtain one globally valid multi-model. Previous work has focused on the most basic configuration of one anoxic and one aerated tank followed by a point settler [Smets, I.Y., Haegebaert, ]. Refinements to the methodology are however needed (and presented here) once the influent flow rate range is increased and the benchmark configuration, proposed by the COST 682 working group no. 2, is taken as the simulation protocol. The main advantage of the obtained linear model (structure) remains the alliance of high predictive power with low complexity, rendering the multi-model fit for on-line optimization and control schemes.

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