High capacity composite depth filter media with low extractables

A process for pre-use water flush of depth filters having lower bioburden comprising:

• a. providing a synthetic composite depth filter media comprising at least two layers, wherein at least one layer comprises synthetic fibrillated polymeric fibers comprising polyacrylonitrile and/or polyacrylonitrile copolymers, and a synthetic filter aid comprising one or more of silica, alumina, glass, metal oxides or mixed-metal oxides, ion-exchange resins and carbon;
• b. treating the depth filter media by,
• i. irradiating the depth filter media at a dose of about 10 to 45 kGy;
• or
• ii. flushing the depth filter media with 0.5 N NaOH for at 100 to 300 liters/m2/hr for 30 min., and
• c. flushing the treated depth filter media with water at flow rates ranging from about 10 liter/m2/hr to about 600 liter/m2/hr such that the level of total organic extractables measured in the filtrate is about 0 to 3 ppm.