Virus removal and transport in saturated and unsaturated sand columns

The purpose of this research was to determine the role that unsaturated flo w conditions play in virus sorption and inactivation during transport throu gh sand columns. Column flow experiments were conducted in Ottawa sand unde r both saturated and unsaturated flow conditions using two bacteriophages, MS2 and phi X174. Input solution containing bromide (Br-) tracer and the vi ruses was applied to the column as a step function and samples were collect ed at the effluent end using a fraction collector. The convection-dispersio n equation, partially calibrated with the transport parameters measured fro m the Br- signal, was used to evaluate the sorption and inactivation charac teristics of the viruses. We found that, while removal of both MS2 and phi X174 increased significantly under unsaturated flow conditions, the mechani sms responsible for removing the two viruses seemed to be different. The re sults from elution experiments using beef extract solution revealed that th e increased removal of phi X174 in the Ottawa sand under unsaturated condit ions appeared to be caused by increased sorption whereas the increased remo val of MS2 was due to inactivation. The difference in virus removal and tra nsport behavior between saturated and unsaturated conditions was likely cau sed by additional sorption at the solid surfaces and the presence of the ai r-water interface (AWI) in the unsaturated system. (C) 2000 Elsevier Scienc e B.V. All rights reserved.