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Floc breakage during particle-liquid separation can lead to significant operational problems, such asreduced clarification rates and filter run times. For natural organic matter (NOM) removal usingconventional coagulation, previous research has shown that improved floc properties may be seenwhen the ratio of organics to coagulant is reduced. However, that implies the addition of highercoagulant doses leading to increased sludge production. Water pretreatment with a magnetic ionexchange resin (MIEX) followed by conventional coagulation can reduce the coagulant dose by up to80 % without negatively affecting the level of NOM removal. However, the impact of MIEX pretreatmentand reduced coagulant dose on floc particles has not yet been fully investigated. Results haveshown that MIEX is able to significantly reduce the charge concentration in organic rich waters.Logically this reduction, was thought to be the reason, for the potential coagulant dose reduction. It isknown that the charge of the anionic organics has to be neutralized in order to remove it effectively byprecipitation.Further on it was shown in this study that NOM character was important in determining how the flocphysical properties were affected by MIEX pretreatment. A significant increase in floc size, strengthand settling velocity was measured for coagulated NOM after MIEX pretreatment, in comparison toconventional coagulation for waters dominated by hydrophobic compounds. Treatment of hydrophilicwaters did not result in such significant improvement of floc physical properties. Considering theseresults, MIEX looks capable of engineering robust downstream floc particles for selected waters,while also reducing potential sludge production by applying very low coagulant doses. Includes 38 references, table, figures.

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Edition: Vol. - No. Published: 11/01/2006 Number of Pages: 15 File Size: 1 file , 520 KB