Method of treating papermaking white water

Abstract

A method of treating papermaking white water which contains dissolved solids, usually of a biodegradable organic nature. According to the invention, the dissolved organic solids, which are objectionable because they cause process equipment corosion, undesirable product and process odors and water pollution, are treated with ultraviolet light so as to lower their concentration and eliminate these problems. The light treatment causes material of relatively simple chemical structure to polymerize into more complex, less soluble materials which can easily be removed from the system as they become less soluble. The method is applicable to papermaking and other industries process using large quantities of process water. The treatment cell, which preferably operates on clarified white water, may be placed in series with the process while water flow or in parallel therewith, and can be operated as a continuing treatment process or as a intermittent treatment process.

What is claimed is: 
     
       1. An improved method of papermaking, said method comprising dispersing papermaking fibers in a slurry, depositing said fibers from said slurry on a papermaking apparatus which includes fiber laying means and a white water recovery system, recovering the white water from said papermaking machine and elsewhere in the papermaking process, clarifying said white water after recovery thereof from said papermaking apparatus, and thereafter at least intermittently exposing said clarified white water to ultraviolet light of sufficient wavelength and quantity to initiate polymerization of dissolved solid materials contained in said papermaking white water into more complex, less soluble molecular structure, permitting said polymerization to continue until said substantial portions of said dissolved solid materials become insoluble, and periodically removing said insolubilized materials from said clarified white water while recirculating said white water within said papermaking apparatus. 
     
     
       2. A method as defined in claim 1 which includes the step of continuing said exposure of papermaking white water until said reduced concentration reaches equilibrium, and thereafter maintaining said exposure at a rate sufficient to maintain said equilibrium. 
     
     
       3. A method as defined in claim 1 wherein said exposure of said papermaking white water is accomplished by removing sample portions of clarified papermaking white water from said papermaking process from time to time, and continually exposing said withdrawn sample portions of said papermaking white water to said ultraviolet light, and subsequently returning said exposed sample portions of said treated papermaking white water to said papermaking process. 
     
     
       4. A method as defined in claim 1 wherein all of said papermaking white water is passed through a ultraviolet light exposure treatment cell, and wherein said papermaking white water in said treatment cell is periodically exposed to said ultraviolet radiation. 
     
     
       5. A method as defined in claim 1 wherein said polymerization is carried out by a reaction mechanism which produces free radicals of increasingly complex molecular structure.