This book introduces in a clear and concise manner the basic concepts and principles of ultrafiltration, a membrane separation process. It discusses various models used to explain the flux decline phenomenon and covers the application of ultrafiltration in various industrial effluent disposal problems in a general way. In the later part, the innovative application of ultrafiltration have been presented for two industrial effluent – Kraft black liquor and Casein whey. Advantage of rotating disc membrane module over fixed disc module in terms of permeate flux etc. has been reported and analyzed in detail. In case of Kraft black liquor, recovery of lignin in the retentate and improvement of water quality parameters of permeate in term of BOD, COD, total solids, etc. have been thoroughly investigated and presented. In case of Casein whey, recovery of low molecular weight proteins have been described. A two-stage ultrafiltration along with ion-exchange-membrane-chromatography for purification of beta-lactoglobulin has been presented.