JULY, 1937
INDUSTRIAL AND ENGINEERING CHEMISTRY
Construction of Blending Chart
It is often necessary to mix two samples of a cellulose derivative to obtain a desired viscosity. Philippoff (3) presented a blending formula as follows: C B [ ? I I O = ZCd[?lli (4) where CO = total concentration in mixture ci = concentration of individual constituents [?I] = viscosity constant of viscosity-concentration from Equation 1
As shown above, [ v ]is constant when the viscosity is determined under conditions such that structural viscosity does not influence the values obtained. Therefore it was not known whether the formula would apply when ordinary conditions of viscosity measurement were used. Figure 4 shows a blending chart similar to the logarithmic chart used for nitrocellulose (2). It was constructed by plotting the percentage of one component in the mixture against the eighth root of absolute viscosity in 5 per cent solution. The chart is used by drawing a line between the
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viscosities of the two components and reading off the percentage of the right-hand component corresponding to the viscosity desired. This blending chart has been tested for many mixtures of ethylcelluloses, as well as for mixtures of ethylcellulose with nitrocellulose. It was found to be accurate within the limits of experimental error even when components of very widely differing viscosities were used. As in the case of the visoosityconcentration chart, other viscosity scales may be used in place of the centipoise scale.
Literature Cited (1) Dow Chemical Co., “Ethocel” (1937); Hercules Powder Co., “Ethylcellulose,” 1937. (2) Gardner, H. A., “Physical and Chemical Examination of Paints. Varnishes, Lacquers and Colors,” 8th ed., p. 1056, Washing: ton, Institute of Paint and Varnish Research, 1937. (3) Philippoff, W., Cetlulosechem., 17, 55-77 (1936). RECEIVED April 19, 1937. Presented before the Division of Cellulose Chemistry at the 93rd Meeting of the American Chemical Society, Chapel Hill, N. C., April 12 to 15, 1937.
Effect of Trade Wastes on Highand Low-Temperature Digestion WILLEM RUDOLFS N. J. Agricultural Experiment Station, New Brunswick, N. J.
Certain organic wastes may cause a delay in digestion time and gas production; others have less effect. With acclimatization, a nonodorous well-draining ripe sludge may be produced when from 10 to 20 per cent organic wastes are added intermittently on the basis of the volatile matter in the fresh solids, and as much as 20 to 40 per cent when added continuously either under mesophilic or thermophilic conditions. Odors tend to increase with organic and poisonous wastes. Thermophilic sludge is less sensitive to organic trade wastes than sludge digested under mesophilic conditions. Drainability of sludge produced from waste-sewage sludge mixtures is poorer. The composition of the gases produced is but slightly affected.
T
HE! transformation of putrefactive organic solids by bacterial action to gases and an inodorous, well-draining residue is affected by several factors. The studies of several factors, such as temperature, inoculation, and reaction control, have yielded considerable practical information. The information available on the effects of certain trade wastes upon sludge digestion under mesophilic conditions is not great, and still less is known about the effects of such wastes under thermophilic conditions.
Laboratory studies to determine the relative effects of organic and poisonous wastes on volatile matter reduction, gas production and composition, hydrogen sulfide formation, and drainability of the residue, together with the possible “acclimatization” of the sludge, present an indication of the behavior of the sludge and show probable operation difficulties. The studies on high- and low-temperature digestion have extended over several years, including pilot plant operation, resulting in a great number of mixtures tried and a large mass of information. The intention is to present briefly the general findings on two groups of wastes, divided for convenience into (a) organic and (b) poisonous wastes. The specific wastes in the first group include different types of tannery waste, slaughterhouse, wool-scouring, rug-cleaning and -dyeing wastes; the poisonous wastes include sodium arsenate, copper sulfate, sulfuric acid; gasoline and waste crankcase oil form a more or less intermediate type. The detailed information will be presented elsewhere. For the determination of the effect of the different trade wastes, varying quantities of wastes were added to digesting mixtures of fresh solids and ripe sludge. The resulting sludges were then used for the same and increased additions of waste to determine the limits of toleration and the degree of acclimatization, if any. The organic trade waste additions varied from 10 to 60 per cent on the basis of fresh solids added, the mineral oils from 1 to 25 per cent, and the poisonous from 0.01 to 5 per cent. The individual series of experiments lasted until practically all gas that could be expected had been produced, and results were compared on the basis of a number of control mixtures. Gas formation was recorded daily, and gas composition, hydrogen sulfide production, and volatile matter reduction a t intervals.
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VOL. 29, NO. 7
INDUSTKlAL AYD ENGINEERING CHEMISTRY
Mesophilic Digestion
Thermophilic Digestion
I n general, the quantities of gas produced per gram of volatile matter added decreased in all cases with increasing quantities of waste added. I n several instances the addition of small quantities of organic wastes caused the production of more gas than the controls. For convenience a number of statements are given for the different types of waste. TANNERY WASTE. The general relation between percentage volatile matter reduction and gas production held for all mixtures receiving tannery composites, tannery vat and tannery lime wastes. Additions of tannery composite waste up to 14 per cent by volume produced as much or more gas than the control, even though the volatile matter had not been reduced to the same extent. Hydrogen sulfide production was comparatively low. BLOODWASTE. These Tastes produced violent foaming, high production of hydrogen sulfide, and low gas per gram of volatile matter and an odorous sludge. WOOL-SCOURING WASTE. Addition of about 10 per cent by volume had only a slight effect although some retardation was apparent. With 20 per cent addition the digestion time was increased about 25 per cent. RUGDYE WASTE. At the peak of daily gas production for the control mixtures, gas production from 10 per cent dye waste mixture was about 35 per cent less, and with increasing quantities retardation was greater. GASOLINE.Addition of 0.1 per cent gasoline caused retardation, and additions of 0.5 per cent by volume affected digestion to such an extent that after 150-day digestion the mixture had not progressed as far as the control in 30 days. SODIUM ARSEKATE. With the addition of 4 p. p. m. the digestion had, for example, progressed after 60 days as far as the controls in 12 days. COPPER SULFATE. Gas production was but slightly affected by copper sulfate in concentration up to 0.025 per cent of the total mixture. Gas production was more affected than liquefaction.
Experiments conducted under thermophilic conditions were similar to those with mesophilic sludge. On the basis of volatile matter reduction, quantities of organic trade wastes up to 10 per cent had no effect and a slight retardation was noticed with quantities of 20 per cent. It was found that acclimating thermophilic sludge was easier than acclimating mesophilic sludge. The quantities of organic trade waste could be increased without difficulty. Gasoline appeared again to be toxic, but the quantities could eventually be increased to as much as 5 per cent on a volume basis of sludge. This would be equivalent to about 15 p. p. m. gasoline present in an aveyage sewage of about 200 p. p. m. suspended solids, provided all the gasoline settled with the sludge and no gasoline was present in the seed material. Thermophilic sludge appeared to be somewhat more sensitive to poisons. The results seem to indicate clearly that thermophilic sludge is not only capable of handling moderate quantities of waste but will produce as much gas as from mixtures without waste, digested under mesophilic conditions, in a shorter time, without requiring acclimation to the same extent.
Acclimatization Repeated additions of the same waste to sludge produced previously under mesophilic conditions when similar quantities of waste have been added showed that the observed retardation was reduced or overcome. This process of acclimating was further tested by adding increasing quantities of the same type of waste. It was possible in'this way to increase the quantities of organic waste from 15 to 20 per cent on the basis of volatile matter in the fresh solids to 20 to 40 per cent. I n other words, when waste is received intermittently, the digesting sludge tolerates considerably less than when received continuously. I n the case of gasoline the sludge could be only slightly acclimated to a maximum of about 1 per cent addition. It was even more difficult to acclimate sludge to copper sulfate and nearly impossible to sodium arsenate. Of considerable interest is that, in nearly all cases when trade wastes are added, gasification is retarded, reduced, or inhibited, whereas volatile matter reduction, or so-called liquefaction, is affected to only a slight extent. It is natural to expect that with increased liquefaction hydrogen sulfide production increases. The quantities of hydrogen sulfide found in the gas varied from 0.1 to 4 per cent. With from 1 to 2 per cent hydrogen sulfide in the gas, corrosion problems in flues, condenser pipes, and boilers increase. Upon acclimatization the hydrogen sulfide production decreased.
Dewatering Experiments on vacuum filtration on filters standardized against an Oliver filter showed that in all cases (except when larger quantities of poisons were added) dewatering of the digested sludge-waste mixtures was poorer than of the controls. I n general, it appears that with the increase in the quantity of trade waste added, the dewatering and drying of the digested sludges would be adversely affected. This does not hold when certain inert or mineral wastes are present.
Odors Odor production as measured by the quantities of hydrogen sulfide in the gas varied under thermophilic conditions from 0.01 to 0.4 per cent. This compares with 0.06 to 2.7 per cent found in the gas formed under mesophilic conditions. The fact, that less hydrogen sulfide was present in the gas when thermophilic digestion was employed, does not indicate the total odor produced. I n addition to the volatile sulfur, certain ammoniacal odors are produced which in combination with the hydrogen sulfide become very offensive. In the case of thermophilic digestion the odors from the sludge were more pronounced, chiefly due to the fact that ammonia compounds cause the sludge to smell like warm barnyard manure. The poisons, with less effect on thermophilic mixtures, caused relatively greater odor prcduction than similar mixtures digested under thermophilic conditions. Mercaptan (pig pen and onion) odors together with the warm ammoniacal odors were very offensive with poisons. RECEIVED April 20, 1937. Presented before the Division of Water, Sewage, and Sanitation Chemistry at the 93rd Meeting of the American Chemical Society, Chapel Hill, N. C., April 12 to 15, 1937. Journal Series Paper, Division of Water and Sewage Research, N. J. Agricultural Experiment Station.
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