Browsing by Author "Finkbeiner, Pascal"

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    The combined influence of hydrophobicity, charge and molecular weight on natural organic matter removal by ion exchange and coagulation
    (Elsevier, 2019-08-21) Finkbeiner, Pascal; Moore, Graeme; Pereira, Ryan; Jefferson, Bruce; Jarvis, Peter
    Three different source waters were investigated using virgin and pre-used anion exchange resins, coagulation, and ion exchange combined with coagulation (IEX&Coagulation). The hydrophobicity, size distribution and charge of natural organic matter (NOM) were used to evaluate its removal. Dissolved organic carbon (DOC) removal by pre-used IEX resin was 67–79%. A consistent ratio of different hydrophobicity fractions was found in the removed DOC, while the proportion and quantity of the molecular weight fraction around 1 kDa was important in understanding the treatability of water. For pre-used resin, organic compounds were hypothesised to be restricted to easily accessible exchange sites. Comparatively, virgin resin achieved higher DOC removals (86–89%) as resin fouling was absent. Charge density and the proportion of the hydrophobic fraction were found to be important indicators for the specific disinfection byproduct formation potential (DBP-FP). Treatment of raw water with pre-used resin decreased the specific DBP-FP by between 2 and 43%, while the use of virgin resin resulted in a reduction of between 31 and 63%. The highest water quality was achieved when the combination of IEX and coagulation was used, reducing DOC and the specific DBP-FP well below that seen for either process alone.
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    Interactions between organic model compounds and ion exchange resins
    (American Chemical Society , 2019-07-22) Finkbeiner, Pascal; Moore, Graeme; Tseka, Tebogo; Nkambule, Thabo; De Kock, Lueta-Ann; Jefferson, Bruce; Jarvis, Peter Robert
    Ion exchange (IEX) can successfully remove natural organic matter (NOM) from surface water. However, the removal mechanism is not well understood due to the complexity and variability of NOM in real source waters as well as the influence of multiple parameters on the removal behaviour. For example, this includes the physicochemical properties of the NOM and IEX resin, and the presence of competing anions. Model compounds with a range of physical and chemical characteristics were therefore used to determine the mechanisms of NOM removal by IEX resins. Fifteen model compounds were selected to evaluate the influence of hydrophobicity, size and charge of organic molecules on the removal by ion exchange, both individually and in mixtures. Three different resins, comprising polystyrene and polyacrylic resin of macroporous and gellular structure, showed that charge density (CD) was the most important characteristic that controlled the removal, with CD of >5 meq mgDOC-1 resulting in high removal (≥89%). Size exclusion of compounds with high MW (≥8 kDa) was evident. The hydrophobicity of the resin and model compound was particularly important for removal of neutral molecules such as resorcinol, which was best removed by the more hydrophobic polystyrene resin. Relationships were identified that provided explanations of the interactions observed between NOM and IEX resin in real waters.
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    Understanding the potential for selective natural organic matter removal by ion exchange
    (Elsevier, 2018-09-27) Finkbeiner, Pascal; Redman, J.; Patriarca, V.; Moore, G.; Jefferson, Bruce; Jarvis, Peter
    Dissolved organic carbon (DOC) removal from a river water source was investigated using ion exchange (IEX), coagulation and membrane filtration. This research linked the variable charge characteristics of the organic compounds present in the source water with removal by IEX and coagulation. The raw water charge density fluctuated considerably (between 5.4 and 10.7 meq mgDOC−1) and controlled removal of the charge loading. Importantly, charge density was not correlated with the organic carbon concentration. The combined IEX and coagulation process reduced the specific DBP-FP (sDBP-FP) of the final water, with values as low as 18 μg mgDOC−1 for both haloacetic acids and trihalomethanes. IEX removed a particular fraction of NOM that 1) enhanced coagulation efficiency, providing increased removal of overall DOC; and 2) enabled coagulation to subsequently remove higher levels of specific components of NOM that have a high DBP-FP. The component of NOM removed by IEX that had a positive impact on coagulation was identified to be charged low molecular weight organic compounds of all hydrophobicity levels, resulting in a reduced specific DBP-FP compared to coagulation alone.
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    Understanding the removal of natural organic matter using ion exchange for drinking water treatment.
    (Cranfield University, 2019-04) Finkbeiner, Pascal; Jarvis, Peter; Jefferson, Bruce
    Drinking water processes that utilise surface water require the removal of natural organic matter (NOM), primarily to reduce the formation of harmful disinfection by-products. This is particularly important given that NOM concentrations in source waters have risen over the past decades in many parts of the world. An effective technology to remove NOM is ion exchange (IEX), which has reportedly offered high final water quality (low DOC, down to 0.25 mg L⁻¹) when used prior to coagulation. However, the performance of IEX varies depending on the water source characteristics and this is currently difficult to estimate. To better understand the relationship between physicochemical properties of NOM and their removal, the individual and combined characteristics charge, hydrophobicity and molecular weight were explored at pilot and bench scale. It was shown that charge plays a major role in the removal of NOM. Model compounds were increasingly removed with increasing charge density. While this emphasised the importance of charge, the results also showed that hydrophobicity became more important at low charge densities. Molecular weight distribution analysis revealed that medium sized organic compounds were dominant in the investigated waters and were well removed. However, high concentrations of this fraction were seen to limit removal. Size exclusion of high molecular weight compounds resulted in low removal of this NOM fraction. The most treatable water by IEX was identified to contain a high charge, a low concentration of high molecular weight compounds and a large proportion of hydrophobic organic matter. For these water types removal of 90% can be expected. Resin properties influenced the removal efficiency, not only by their state (virgin or used) but also by their properties. The use of three different resins showed that larger pore sizes improved the removal of NOM. Resin made of polystyrene was seen to provide higher removal of aromatic compounds due to the contribution of non- electrostatic interactions. The combination of IEX and coagulation showed consistently high treated water quality for varying source water through selective removal of NOM by IEX, which facilitated an improvement in the coagulation process, resulting in higher dissolved organic carbon and reactive disinfection by- product precursor removal.