Water purification in membrane separation rejection of bacteria and virus and factors effecting permeate flux.

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It is important to elucidate the characteristics of membrane filtration and separation to know feasibility and applicability of membrane technology in water purification. In this research, rejection of bacteria and virus was investigated as well as removal of turbid and colloidal materials. Factors affecting permeate flux was also studied. The results obtained are summarized as below.1) The removals of kaolin suspensions, humic substances and E. coli groups by externally pressurized hollow fiber microfiltration membrane (30 nm of pore size) were almost the same as those by tubular ultrafiltration membrane (14, 000 dalton of molecular weight cut off size). The permeate flux of hollow fiber module used ranged from 2.5 to 6 m/d and it was high enough for practical application.2) By using latex particles for artificial cake formation on membrane surface, factors affecting permeate flux were investigated experimentally and theoretically. Initial flux decline rate was significantly affected … More by porosity and particle size. As cross-flow velocity determines back transport rate. It gave steady-state flux value. When polidispersity of influent was considered, numerical, calculation showed that smaller particles accumulated in cake layer formed on membrane with time elapsed. It was because shear effect was increased with increase on particle size enchancing back transport.3) New microfiltration membrane with pore size of 100 nm rejected 90% of E. colt Q_<beta> (ca. 25 nm in size) applied due to adsorption. The cake layer, formed on membrane significantly increased the rejection in natural pond water filtration. Significant leak of Q_<beta> was observed through ultrafiltration membrane (40, 000 dalton of molecular, cut off size). Even though real rejection was high enough, observed rejection might be significantly reduced due to concentration polarization.4) Based on the above results, preliminary design of of a purification plant (capacity 50, 000 m^3/d) was done adopting hollow fiber module as membrane configuration. It was shown that land area required for the membrane plat was much smaller than that for, a conveational purification plat with same capacity, in case the permeate flux was maintained 0.5 m/d. In case no recycling of feed stream is the system, the operational cost becomes always cheaper than that of the conventional one. Less