Browsing by Author "Sharp, Emma"

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    Comparison of coagulation performance and floc properties using a novel zirconium coagulant against traditional ferric and alum coagulants
    (Elsevier Science B.V., Amsterdam., 2012-09-03T00:00:00Z) Jarvis, Peter; Sharp, Emma; Pidou, Marc; Molinder, Roger; Parsons, Simon A.; Jefferson, Bruce
    Coagulation in drinking water treatment has relied upon iron (Fe) and aluminium (Al) salts throughout the last century to provide the bulk removal of contaminants from source waters containing natural organic matter (NOM). However, there is now a need for improved treatment of these waters as their quality deteriorates and water quality standards become more difficult to achieve. Alternative coagulant chemicals offer a simple and inexpensive way of doing this. In this work a novel zirconium (Zr) coagulant was compared against traditional Fe and Al coagulants. The Zr coagulant was able to provide between 46 and 150% lower dissolved organic carbon (DOC) residual in comparison to the best traditional coagulant (Fe). In addition floc properties were significantly improved with larger and stronger flocs forming when the Zr coagulant was used with the median floc sizes being 930 υm for Zr; 710 υm for Fe and 450 υm for Al. In pilot scale experiments, a similar improved NOM and particle removal was observed. The results show that when optimised for combined DOC removal and low residual turbidity, the Zr coagulant out-performed the other coagulants tested at both bench and pilot sca
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    Natural organic matter coagulation
    (Cranfield University, 2005-10) Sharp, Emma; Jefferson, Bruce; Parsons, Simon
    The removal of natural organic matter (NOM) is one of the main challenges facing water utilities in both the UK and the US. As a consequence of changes in land management and an increased carbon loss from solids, a greater amount of accumulated organics is now being flushed into the aquatic environment during increased surface run-off events such as snowmelt or heavy rainfall. Furthermore, whilst traditional treatment with trivalent coagulants has proven a successful strategy in the past, operational problems are now being reported during periods of elevated organic levels in the water. These include the formation of fragile flocs, a greater particulate carryover onto downstream processes and increased disinfection by product (DBP) formation. Resin adsorption techniques were employed to fractionate the water samples into their hydrophobic and hydrophilic components. This, coupled with raw water monitoring, revealed that NOM composition and characteristics can vary, even if the total organic concentrations appear stable. In particular, hydrophobic NOM fractions contribute the majority of the charge compared to the hydrophilic fractions, and therefore exert a greater impact on coagulation conditions. Comparison across different source waters, seasons, at varying experimental scales and under varying coagulation conditions, revealed that zeta potential monitoring during coagulation takes into account the changing electrical property of the water, and in general, maintaining a value between -10<ζ<+3 mV will result in low and stable residuals. A similar operational zeta potential range exists for clarification processes, although the zeta potential value at the positive threshold is influenced by the hydrophobic NOM content, such that the range is extended as the specific UV absorbance (SUVA) value of the raw water decreases. Whereas the hydrophilic concentration was found to control the achievable dissolved organic carbon (DOC) residual, attributed to a negligible charge density and poor coagulant-interactions. Consequently, the key finding of this study is that raw water characterisation coupled with zeta potential monitoring will provide a straightforward guide to the mechanistic understanding of treating NOM rich waters.