Water treatment process

Claim 1

A water treatment process for removing turbidity-causing impurities from said water, said process comprising: a. adding to the impure water a minor amount of a filter aid material; b. contacting said impure water with said filter aid material for a time sufficient for impurities in said water to become absorbed on said filter aid material; and c. flowing said impure water containing said filter aid material having said impurities absorbed thereon through a pre-filter having a flow rate of at least two (2) liters/min./sq. m., and thereafter through a filter medium in the form of a porous, non-woven matrix made by a wet-lay procedure on a suitable support element and consisting essentially of the following constituents: (1) randomly arranged, irregularly intersecting and overlapping cellulose fibers in an amount sufficient to retain the integrity or continuity of the mat during said water treatment; (2) micro-bits produced from a polymer which is non-brittle in expanded form, and selected from (a) an expanded, thermoplastic styrene-polymer, (b) an expanded lower polyolefin, which is the polymer of a ethylenically unsaturated hydrocarbon monomer having from 2 to 6 carbon atoms, (c) an expanded melt alloy of polyethylene with up to about 10 percent by weight of polystyrene, (d) an expanded copolymer of propylene with from about 20 to about 30 percent by weight of ethylene, (e) an expanded melt alloy composed of at least 50 percent by weight of polypropylene and the balance being a copolymer of ethylene with up to about 30 percent of said copolymer being vinyl acetate, or micro-bits of a flexible foamed polyurethane, said polymer micro-bits being substantially completely free of intact cells of the expanded polymer from which they are produced, the amount of said micro-bits present in said filter medium being sufficient to provide the medium with a porosity enabling flow required for said water treatment, and at least one of the following: (i) a wet web support releasing agent in an amount sufficient to facilitate removal of the filter medium from the support on which it is prepared; (ii) a wet-strength enhancing agent in an amount sufficient to enhance the wet-strength of said filter medium, but less than that which will impair the functions of the constituents of said filter medium other than said wet-strength enhancing agent; (iii) an adsorbing agent selected from the group consisting of (a') finely divided activated carbon in an amount below that at which substantial release of finely divided carbon from the filter medium can occur during said water treatment (b') diatomaceous earth in an amount below that at which substantial release of diatomaceous earth from the filter medium can occur during said water treatment; (c') colloidal alumnia monohydrate in an amount sufficient for removing a substantial portion of any chromic acid and its salts from said water undergoing treatment; and (d") a finely divided ion exchange resin in an amount sufficient to remove a substantial portion of ionized substances from said water undergoing treatment; and (iv) a wet web strengthening agent in an amount that together with the cellulose fibers is sufficient to provide the filter medium with a degree of tensile strength to withstand manpulation during its preparation, and below that amount at which said agent will agglomerate while being admixed with the aforementioned constituents of the filter medium.