title: Characteristics of flocs formed by polymer-only coagulation in water treatment and their impacts on the performance of downstream membrane separation.
abstract: Two different quaternary amine polymers were examined as primary coagulants for the removal of natural organic matter (NOM) and concurrent production of flocs favorable for downstream membrane separation. The primary issue explored was the relationship between various coagulation conditions on the floc characteristics and the subsequent performance of microfiltration when filtering coagulated NOM. The size distribution and morphological properties of flocs formed through the coagulation of NOM were characterized and the effects of polymer type and dose on these characteristics were also examined. Coagulation of NOM using polydiallyldimethyl-ammonium chloride (pDADMAC) produced looser and less settleable flocs compared to dosing the equivalent amount of epichlorohydrin/dimethylamine (epi/DMA). This was associated with the formation of a relatively denser cake layer on the top of the membrane for the filtration of NOM coagulated with epi/DMA. The charge neutralization coagulation condition with the polymers removed almost all of the fouling tendency that had occurred when filtering raw NOM. The median diameter and the fractal dimension of the flocs produced increased as the zeta potential approached zero, which resulted in the formation of a cake layer that was easily removed from the surface of the membrane.
authors.affiliation: a Department of Civil and Environmental Engineering , Sejong University , Seoul , Republic of Korea.
authors.forename: Sung Kyu
authors.initials: SK
authors.lastname: Maeng
authors.affiliation: b US Army Center for Environmental Health Research , Fort Detrick , MD , USA.
authors.forename: Thomas C
authors.initials: TC
authors.lastname: Timmes
authors.affiliation: c Water Resources Research Institute, Sejong University , Seoul , Republic of Korea.
authors.forename: Hyun-Chul
authors.initials: HC
authors.lastname: Kim
mesh_terms: D005374:Filtration; D005427:Flocculation; D008567:Membranes, Artificial; D011108:Polymers; D018508:Water Purification
chemical_list: D008567:Membranes, Artificial; D011108:Polymers
keywords: Natural organic matter; floc characteristics; membrane fouling; primary in-line coagulation; quaternary amine polymer