A variety of water quality improvements can be accomplished by properly operated filtration plants. These include reduction of turbidity, micro-organisms, asbestos fibers, color, trihalomethane precursors, and organics adsorbed to particulate matter. The focus of the paper is on the reduction of turbidity and microorganisms. Historical data on water treatment are reviewed, and typhoid fever death rates are compared for time periods before and after treatment. Generally water treatment improvements were followed by declines in the typhoid death rate. The paper also presents a review of microorganism removal research in the context of EPA's recently proposed Surface Water Treatment Rule. Properly operated water filtration processes can effectively remove microorganisms, and the Surface Water Treatment Rule can help attain better plant operation.