Patented Jan. 28,1947 2,414,930 STATES 1 PA 2,414,930 WASTE LIQUOR DISPOSAL Benjamin W. Collins, Swarthmore, and Edmond T. Roetman, Ridley Park, Pa, assignors to American Viscose Corporation, Wn, Del., a corporation of Delaware No Drawing. Application February 19,1943, 1 Serial No. 4 Claims. This invention relates ‘to improvements in 2 . ?rst treated with an acid such as waste sulfuric methods of preparing waste liquors for disposal.v More particularly, the invention relates to im-' provements in methods of preparing for disposal waste liquors which result from the manufacture acid to reduce the pI-I of the waste liquor to ap proximately within the range of 8 to 10, prefer ably approximately 8.‘ The waste liquor is then this process containing the polysuliides presents in contact with the waste liquor and atmospheric collected in a storage tank and is withdrawn from of viscose rayon and which contain sul?des. the tank and sprayed’ or otherwise deposited onto In the manufacture of rayon by the viscose ' a ?lter bed. The ?lter bed contains aerobic and/ process, a cellulose xanthate solution is extruded or anaerobic micro organisms which cause the into an acid bath wherein the cellulose inthe so lution is regenerated and free sulfur and sulfur 10 sul?de in the waste liquor to be oxidized to stable sulfur compounds, chiefly sulfates. The filter compounds are formed. The cellulose product bed is made of crushed rock having sufficient containing free sulfur is then treated with an spaces or interstices to permit the waste liquor alkaline sul?de such as ammonium sul?de or an to slowly trickle or percolate through the bed alkali metal sul?de preferably sodium sul?de and at the same time to present extended sur which forms with the sulfur readily removable polysul?de compounds. The waste liquors from 1153 faces on which the micro organisms may grow oxygen. Sludge such ‘as activated or digested a dimcult disposal problem. The polysulfldes as sludge from a domestic. sewage disposal system such have a biochemical oxygen demand (B. O. D.) and if discharged directly into a river or 20 is deposited on the ?lter bed and serves to supply the micro organisms used in carrying out the stream will deplete the supply of dissolved oxygen process. A portion of the e?luent that has ' in the water, thereby endangering the biological trickled through the ?lter bed may be introduced ‘ life (?sh, crustacea, etc.) in the stream. Also it into the waste liquor collected in the storage tank . will lower the capacity of the river or stream to to seed the waste liquor with micro organisms to dispose of other polluting substances. 25 act on the sul?des and assist the action of the A principal object of the present invention is micro organisms in the ?lter bed. Also, the micro to provide a method or" preparing for disposal organisms added to the waste liquor in the storage waste liquors containing sulfides wherein the sul tank serve to replenish the micro organisms in ?des are converted into more highly oxidized compounds which may be discharged into a river 30 the filter bed ‘which, in effect, increases its op erating capacity as well as the length of time or stream without endangering the biological life that the ?lter bed can be continued in operation. therein or decreasing the capacity of the river or In the operation of the process the Waste liquor stream to dispose of other forms of oxidizable containing the sul?de is maintained in contact matter. . A further object of the invention is to provide 35 with the micro organisms until substantially all of the sul?des are oxidized to sulfates, which are a method of preparing for disposal waste liquor ‘ containing sul?des wherein the sul?des are sub jected to the action of micro organisms and are final oxidation products and are therefore stable, and the pH of the waste liquor is reduced to with the range of approximately 5 to 7, preferably converted into more, highly oxidized compounds. . in Other objects and advantages of the invention 40 approximately 7. By applying this procedure the treated waste liquor may be discharged into a will be apparent from the following description ' riverv or stream without affecting its biochemical and appended claims. oxygen demand, endangering the animal life in the manufacture of rayon by the viscose ‘ therein, or lowering its capacity to dispose of process, the rayon containing sulfur is treated with an alkali metal sul?de such as sodium sul 45 other forms of domestic or industrial pollution. While a preferred procedure has been de ?de, portions of which react'with the sulfur in scribed, it is to be understood that changes and the rayon to form-sodium polysul?des of varying variations may be made without departing from chemical composition such as NazSz, NazSs, Na2S4, the spirit and scope of the invention as de?ned or Nazss. The rayon is drained and washed and the appended claims. the preparation of the waste liquor from this 50 in We claim: stage of the process forms the subject matter of_ 1. A method of treating of waste liquor from the present invention. In accordance with the the manufacture of viscose rayon containing sul present invention the hydrogen ion concentration ?des and polysul?des comprising adding acid to (pH) of the waste liquor is carefully controlled. the waste liquor to reduce the pH of the waste The waste liquor, being substantially alkaline, is 55 -liquor to approximately within the range of 8 to aeiaoeo I 10, and then subjecting the waste liquor to the action of micro organisms which occur in sludge thereby oxidizing by their action the sul?des and polysul?des to stable-sulfurofcompounds. waste liquor from 2. A method of treating - d mately within the'range oi.’ 8 to 10, passing the waste liquor through a ?lter bed containing micro-organisms which occur in sludge thereby oxidizing the sul?des to stable‘ sulfur compounds hy the action of the micro-organisms. 4. A method of treating waste liquor from the manufacture of viscose rayon and containing sul tides, comprising adding sulfuric acid to the waste liquor to reduce the pH of the liquor to approxi uor to reduce the pH of the waste liquor to ap- proximately within the range of 8 to 10. and then mately within’ the range of 8 to 10, passing the 10 passing the waste liquor through a ?lter bed con waste liquor through a ?lter bed containing talnlng micro organisms which occur in sludge micro-organisms which occur in sludge thereby thereby oxidizing by their action the sul?des to oxidizing the sul?des to stable sulfur compounds stable sulfur compounds and adding a portion - by the action of the micro-organisms, and adding of the effluent from the ?lter bed to the raw waste a portion of the e?iuent from the ?lter bed to liquor before the waste liquor is passed through 15 the raw waste liquor before the waste liquor is of viscose rayon containing sul the manufacture ?des comprising adding an acid to the waste liq the ?lter bed. i 3. A method of treating waste liquor from the manufacture of viscose rayon and containing sul tides, comprising adding sulfuric acid to the waste _ liquor to reduce the oil of? the liquor to apprcxi= 20 passed through the ?lter bed. BENJAMIN ‘W. COLLINS. EDMOND T. ROETMAN.