Abstract: The method and apparatus for filtering a liquid including a filter vessel divided into an upper filter compartment and a lower plenum compartment. An external vessel is positioned at or below the elevation of the tops of the filter element fittings in the plenum compartment. A pressurized gas is supplied to the upper portion of the external vessel forcing backwash liquid from the external vessel into the lower portion of the plenum compartment backwashing filter elements within the filter compartment.

Abstract: A filter element including a perforated tubular member for supporting a filter medium, a tubular distributor core concentrically located within the support member and having a plurality of apertures in the core wall, and a plurality of dividers positioned around the tubular distributor core to prevent the unimpeded flow of liquid through the annular space between the support member and the distributor core and to provide a plurality of annular chambers between the core and the support member. The dividers are located so that the ratio of the flow of liquid through the apertures into an annular chamber to the area of the support member served by the annular chamber is the same for all chambers. In an alternative embodiment the diameter of the apertures is varied along the length of the filter element to assist in distributing the flow of liquid.

Abstract: A liquid precoat filter has a multitude of elongated replaceable filter elements that have one of their ends supported on tubes that project upwardly from a tube sheet. A multi-component, spring-biased, sliding seal prevents leakage between the filter elements and their support tubes. Externally engageable connectors are used to releasably fasten the filter elements to their tubes.

Abstract: The invention relates to a method for converting strong-base anion exchange resins from the monovalent anion form to the hydroxide form. A .?.solution.!. .Iadd.source .Iaddend.of polyvalent anions is first passed through the resin to displace the monovalent anions. A solution of alkali metal hydroxide is then passed through the resin to convert it to the hydroxide form, and to produce an effluent solution of hydroxide ions and polyvalent anions. This effluent solution is then neutralized with an acid containing .Iadd.a source of .Iaddend.polyvalent anions, and the neutralized solution is passed through a second batch of resin in the monovalent anion form. In the preferred embodiment, a portion of the effluent is retained without neutralization and is delivered to the second batch of resin after the neutralized effluent to perform a portion of the hydroxide regeneration.