This investigation aimed to compare the disinfection by-product formation potentials (DBPFPs) of three UK surface waters (1 upland reservoir and 2 lowland rivers) with differing characteristics treated by (a) a full scale conventional process and (b) pilot scale processes using a novel suspended ion exchange (SIX) process and inline coagulation (ILCA) followed by ceramic membrane filtration (CMF). Liquid chromatography-organic carbon detection analysis highlighted clear differences between the organic fractions removed by coagulation and suspended ion exchange. Pretreatments which combined SIX and coagulation resulted in significant reductions in dissolved organic carbon (DOC), UV absorbance (UVA), trihalomethane and haloacetic acid formation potential (THMFP, HAAFP), in comparison with the SIX or coagulation process alone. Further experiments showed that in addition to greater overall DOC removal, the processes also reduced the concentration of brominated DBPs and selectively removed organic compounds with high DBPFP. The SIX/ILCA/CMF process resulted in additional removals of DOC, UVA, THMFP, HAAFP and brominated DBPs of 50, 62, 62, 62% and 47% respectively compared with conventional treatment.

The influence of pre-treatment on the suppression of irreversible (IR) fouling of ceramic membranes challenged with three UK surface waters has been studied at pilot scale. An initial scoping study compared the efficacy of suspended ion exchange (SIX) and clarification (coagulation followed by sludge blanket clarification) individually and in combination. Direct membrane filtration following in-line coagulation (ILCA) was also investigated with and without SIX. The impact on the various organic fractions, specifically high molecular weight (HMW) biopolymers (BPs) and humic substances (HSs), and lower molecular weight (LMW) building blocks (BBs) and neutrals, was studied using liquid chromatographyorganic carbon detection (LC-OCD). Results revealed SIX and coagulation to preferentially remove the LMW and HMW organic fractions respectively. Residual HMW organic matter (primarily BPs) following SIX pretreatment were retained by the membrane which led to rapid irreversible fouling. Coagulation pre-treatment provided stable membrane operation and the residual LMW organics were not significantly retained by the membrane. Combining clarification and SIX resulted in

Some waters can have elevated concentrations of dissolved organic carbon (DOC), especially sources like surface waters that are under the influence of secondary effluent, recreation, heavy population, farming and industry. In a number of locations in north-west Europe, for example the United Kingdom and Scandinavia, DOC levels are increasing over time, most likely due to climate change effects and changes in land use. For these types of water, ion exchange (IX) is of interest as a pre-treatment option because the removal of colour and DOC by IX will increase the efficiency of all downstream processes, including: coagulation, membrane filtration, advanced oxidation processes (AOP) and granular activated carbon filtration (GAC). It will also lead to improved water quality (i.e., less by-product formation) and most likely improvements in biostability within the distribution network. Surface waters also contain suspended and colloidal matter, making it nearly impossible to use standard state-of-the-art, fixed bed IX columns. This is because these beds will foul quickly (i.e., head loss build-up) with suspended matter. When this happens, the IX bed starts to function as a filtration bed rather than as an adsorption media. The newly developed suspended ion exchange process SIX® (suspended ion exchange, PWN Technologies, Netherlands) presents an advanced solution for a world-wide challenge: how to remove natural organic matter (NOM/DOC) as a first step in surface water treatment to improve the efficiency of downstream processes and water quality. In addition to the possibility to treat water that contains suspended matter, another advantage is that the process has advanced to an economically and technically feasible process, requiring low contact times and small resin inventories, with a large tolerance for flow fluctuations. Depending on the water source, adding a relatively low concentration of coagulant after IX removes even greater quantities of DOC, especially in the fraction of the high molecular weight organic carbon (whilst the IX primarily removed the humic and fulvic organic fractions). The most important advancement is that almost any commercially available resin can be used, creating the desired flexibility in resin suppliers for water supply companies. This paper describes the process and its advantages and disadvantages compared to conventional technologies. NOM-characterisation with size exclusion chromatography, liquid chromatography – organic carbon detection (SEC/LC-OCD) before and after this process showed the outstanding performance of the process, especially on water types which contain high colour/DOC-concentrations and low total dissolved solids, which are typical of the majority of the surface waters in the north-west of Europe.

In-line coagulation adsorption (ILCA) followed by ceramic microfiltration (CMF) was tested at pilot scale and compared to a full scale traditional process consisting of coagulation and dissolved air flotation (DAF) followed by rapid gravity sand filtration (RGF), for treating a reservoir water source which is prone to high concentrations of algae. The ILCA CMF process was shown to remove 10–16% more dissolved organic carbon (DOC) and reduced disinfection by-product formation potential (DBPFP) by 9–13% in comparison to conventional treatment (optimised coagulation). ILCA effectively controlled membrane fouling allowing the ceramic membranes to be operated at high flux (200 l/m2h) with low membrane fouling (0.9–1.9 kPa/day). A process comprising ILCA and direct ceramic microfiltration was shown to provide very stable treated water quality under a range of challenging conditions. Additionally, the process is more compact showing significant reductions (circa 60%) in footprint relative to a conventional DAF/RGF process.