DISPOSAL AND PURIFICATION OF FACTORY WASTES OR MANUFACTURING SEWAGE. By H. W. CLARK, Chemist to the Board. DISPOSAL AND PURIFICATION OF FACTORY WASTES OR MANUFACTURING SEWAGE. By H. W. CLARK, Chemist to the Board. The disposal and purification of manufactural wastes has been the subject of much investigation by the State Board of Health of Massachusetts during the past fifteen years, both at the Lawrence Experiment Station and at certain industrial establishments in the State. The nature of these wastes has been varied, including those from tanneries, woolen factories, paper mills, dye works, creameries, binders' board works, yeast factories, carpet works, batting works, silk mills, gas works, bleacheries, shoddy mills, glue works, paint mills, etc. As a result of these investigations practical and satisfactory methods for the disposal of many of these wastes have been developed, and at the present time a number of purification plants are in operation or under construction in Massachusetts. The subject is a broad one, and many difficulties have been encountered that are absent from the problem involved in the disposal of domestic sewage, and which, oftentimes, prevent a general application of the results. obtained. The chief difficulties are (1) the nature of the waste liquor in some manufacturing processes whereby purification by bacterial action. or nitrification is prevented; (2) the excessive amount of solid matter per unit volume of liquor, especially carbonaceous matter, often many times as great as that found in the strongest domestic sewage; (3) the enormous volume of liquor used in many industries, which liquor comes from such plants loaded with organic matter and chemicals of many kinds; (4) the varying character of the liquor coming from different manufacturing plants doing similar work, a fact which prevents the experimental data from being universally applicable; and (5) the liability to change, from time to time, in the processes carried on in any industrial plant. WASTES FROM TANNERIES.1 Tannery A. During the past fourteen years the wastes from three tanneries have been experimented upon. The first tannery investigated was engaged in preparing and tanning sheep skins. The daily volume of the waste varied from 20,000 to 50,000 gallons, and was composed of a thick, offensive liquor varying in color as different aniline dyes were used. The amount of organic matter present was large and in an advanced state. of putrefaction. It seldom contained any substance of a character to check bacterial action and was, therefore, easily nitrified. The sludge was at times great in volume and rich in fats and nitrogenous matters. A filter was constructed at this tannery, containing 2 feet in depth of sand of an effective size of 0.14 millimeter, over gravel underdrains; and sewage, made up of a mixture of the waste liquors from all the processes carried on at the tannery, was first applied to it on Sept. 27, 1895, at an average rate of 55,000 gallons per acre daily. During a large part of its period of operation, however, the rate was 25,000 gallons per acre daily, but even at this rate the filter became clogged quickly by matter in suspension in the waste. The following analyses show the character of the liquor as applied to and of the effluent from this filter during its period of operation: It was evident that better nitrification and higher rates of filtration could be obtained if suspended matter was removed from the sewage before filtration. 1 In some instances, the filters as described in the various annual reports in connection with the purification of manufactural wastes, bear different numbers than in this review. The numbers given here are for the sake of clearness and to prevent confusion. |