COLIPHAGE REJECTION UNDER ULTRAMEMBRANE FILTRATION

Virus rejection under ultramembrane filtration was examined by a dead- end filtration technique using two types of coliphages, T1 and Q beta. Four kinds of ultramembrane filters with different cut-off molecular weights were evaluated. The lowest rejection rate in each coliphage wa s observed in the filtration of coliphage suspension through the loose st ultramembrane filter used. The value was raised under the filtratio n of mixed suspension of coliphage and activated sludge, and more sign ificantly under the filtration of coliphage suspension after formation of cake- and gel-layers on the filter by filtrating activated sludge suspension in advance, The increase of the rejection rate was related to that of resistance value, Rcg, of cake- and gel-layers, and it was estimated that coliphages T1 and Q beta might be removed almost comple tely under Rcg not less than 5x10(12) m(-1) and 1x10(13) m(-1), respec tively. These values of Rcg correspond to those appearing in full- and pilot-scale plants using crossflow ultramembrane filtration for solid -liquid separation of bioreactor contents under a permeation flux of 1 -2 m . d(-1).