A ctivated Sludge-Milorganite Constituents, Elements, and Growth-Producing Substances C. J. REHLING AND E. TRUOG University of Wisconsin, Madison, Wis.
A
large amount of resistant organic matter remaining necessitated several treatments with 30 per cent peroxide to remove it. Two sodium sulfide-oxalic acid treatments with an intervening peroxide treatment were necessary to remove completely the free iron oxide and last traces of organic matter. The resulting light gray, silty residue, which resembled that obtained from an average soil by the same procedure, was mechanically separated into sand, silt, and clay fractions by sedimentation, using a centrifuge for the latter two fractions.
CTIVATED sludge, produced a t the Milwaukee Sewage Disposal Plant to the extent of approximately 110 metric tons per day and sold under the trade name of “Milorganite”, has given excellent results as an ingredient of mixed fertilizers and as a direct fertilizer for lawns, golf course fairways, and certain special fruit and truck crops grown on sandy or other soils low in organic matter. Results of preliminary experiments relative to its fertilizer value were reported by Noer (6) in 1926. Although its nitrogen and available phosphoric acid contents of about 6 and 2.5 per cent, respectively, account for its main fertilizer value, the results obtained in practice seem to indicate appreciable benefits from other constituents. This has raised the question as to whether or not Milorganite contains sufficient amounts of the minor nutrient elements and possibly plant hormones to promote plant growth in certain cases. I n order to help answer this question, it was decided to make a rather extended analysis of Milorganite, the results of which are here reported.
TABLE 11. CHEMICAL COMPOSITION OF MILORGANITH Composite Sample Constituents
%
Gross Composition The main groups of organic compounds and mechanical separates of inorganic substances are given in Table I. The protein content as given was calculated from the nitrogen content, since it is known that practically all the nitrogen is present in the form of protein. A calculation by difference of protein was also made using the data of Tables I and 11; the result checked closely with that based upon the nitrogen content.
Ha0 lost at 110’ C. Ignition loss with Mg(N0s)z Si02 Fez03 AlzOs CaO
FA0
NazO Ti02 MnO CUO BaO ZnO PbO NiO coo Pa05
50s
c1 CraOs AszOa BzOs Iodine Total
TABLE I. GROSSCOMPOSITION OF MILORGANITE Constituents Determined
Air-Dry Basis
% Water (lost a t 110’ C.) Protein Cellulose Fat Fen08 (free) Sand Silt Clay Total
-Composite Sample, 193132Air-dry basis Water-free 1 2 Av. baais 7.240 63.620 7.800 6.630 2.957 1.541 1.680 0.795 0.885 0.075 0.0301 0.0435 0.061 0.0145 0.209 0.00526 0.00019 2.880 2.640 0,463 0.203 0.013 0,0038 0.0010
% 7.260 63.540 7.880 6,630 2.997 1.567 1.680 0.804 0.948 0.079 0.0304 0.0427 0.052 0.0155
%
%
%
7.250
.....
.... .... .... ....
68.550 63.580 8.452 7.840 7.148 6.630 3.211 2,977 1.554 1.675 1,680 1.810 0.800 0.862 0.916 0.988 0.077 0.083 0,0302 0.0327 0.0431 0.0465 0.0565 0.0611 0.0150 0.01627 0.209 0.225 0,00561 0 Obi16 0.0052 0.00018 0.000185 0.00020 2.850 3.089 2.865 2.740 2.900 2.690 0.467 0.501 0.465 0.219 0.203 0.01347 0,0125 0,012 0,00395 0,0041 0.00113 0.00426 0.0011 0.00105 99.9131 99.9036
:
.
.
.
I
1931-35, Air-Dry Basis
.... ....
0 : 807
.... ....
0.025 0.0487
....
0.030
.... ....
....
3.180 2.93
.... .... .... 0.0115
....
6.2
37.5 7.0 6.5 6.1 2.4 13.4 14.4 93.5 6.5‘‘ ’’ Water not lost a t 110’ C., lignin, and various easily soluble salts.
-
Cellulose was determined by the crude-fiber method (1). Although pectin, some lignin, and related compounds, which are present in small amounts, are usually included under “crude fiber”, they are here included under cellulose, being complex insoluble carbohydrates which have escaped biological digestion. The 7 per cent of cellulose present in Milorganite is probably not sufficient to interfere with the availability of the nitrogen to plants because of temporary microbial fixation which is induced by excessive supplies of carbohydrates (8). Fat, or ether-soluble extract, was determined by the usual standard procedure (I). Although an appreciable amount of fat-6.5 per cent-was found, because of its low activity this has no special significance as regards the fertilizer value of Milorganite. The mechanical separations of the inorganic materials were made essentially as described in a special case for soils (9). After leaching out fatty material with ether, the relatively 281
The very low sand content indicates that the plant operation for removal of heavy coarse material such as sand is effective. The silt and clay fractions, as with soils, contained inorganic base-exchange material, and determinations by the usual method revealed exchange capacities of 26.2 and 31.1 milliequivalents per 100 grams, respectively. This is equivalent to an exchange capacity of 28.7 milliequivalents per 100 grams of the ‘combined silt and clay as these occur in Milorganite. The total exchange capacity of Milorganite was found to be 22.4 milliequivalents per 100 grams, 5.9 milliequivalents of which are accounted for by the weighted capacity of the silt and clay, while the balance, 16.5 milliequivalents, is presumably due to organic matter. This rather high exchange capacity of Milorganite may have some value as a reservoir for holding bases when large amounts of the material are applied to very sandy soils, which are generally lacking in this respect. The free iron oxide was determined by analysis of the extract obtained in the sodium sulfide-oxalic acid treatment. This iron originates partly from the ferric chloride which is added for coagulation just prior to filtering. A small portion (see Table 111)is present in the ferrous state, and represents iron which is very readily available for plant growth. Biological decomposition of the associated organic material undoubtedly results in the reduction and solution of more of the
VOL. 11, NO. 5
INDUSTRIAL AND ENGINEERING CHEMISTRY
282
iron oxide. Milorganite is thus probably a very good source of iron for plants, since plants absorb and utilize largely the ferrous form (4).
Chemical Composition A rather complete chemical analysis of the inorganic constituents of Milorganite is presented in Table 111.
portance in certain cases. Based upon these figures, a ton of Milorganite contains the equivalent of 1.36 kg. of cupric sulfate pentahydrate, 0.95 kg. of zinc sulfate heptahydrate, 0.48 kg. of manganese sulfate tetrahydrate, and water-soluble boron equivalent to 0.18 kg. of borax. The high solubility of the minor nutrient elements in weak solvents indicates a high degree of availability.
Heteroauxin Production CONSTITUENTS OF MILORGANITE TABLE111. MAINFERTILIZER -Sample, Constituent6
1
Air-dry basis 2 Av.
% Nitrogen, total Citrate-soluble PzOa Citrate-insoluble P20s Water-soluble PzOa Exchangeable KzO Exchanaeable NazO Oreanic- and water-soluble - BO8
Water-solubIe BzOa Ferrous iron CUO total Sol. in COz-satd. Hz0 Sol. in 0.002 N HzS04 MnO total Sol: in COz-satd. HzO Sol. in 0.002 N HzSO4 ZnO total Sdl. in COz-satd. Hz0 Sol. in 0.002 N HzSO4
1931-32-
6.060 2.250 0.630 0,0052 0.284 0.151
...... .. .. .. .... .... .... .... .... .... .. .*.... ....
%
%
6.040 6.050 2.230 2.240 0.620 0,625 0.0052 0:281 0.282 0.151 0.151
... ... ... ... . . #
.... ..
... .,.
... ... ...
.... .... .... .... ..*. .... .... ....
..... ...
Waterfree basis
Composite Sample 1931-37: Air-Dry Basis
%
%
6.52 2.42 0.675 0.0056 0.304 0.163
6.04 2.52 0.66 0.0041 0.465
.... .... .... ..... ... .... .... .... .... .... .... ....
0.621 0.0073 0.016 0.0431 0.0035 0,0461 0.0250 0.0062 0.0204 0.030 0.026 0.032
....
After ashing, silica, sesquioxides, titania, the alkaline earth metals, and the alkali metals were determined by the usual methods. In the acid extract of the ash, cobalt and nickel were determined gravimetrically by precipitating with nitroso-p-naphthol and dimethylglyoxime, respectively, and copper, manganese, and zinc colorimetrically as pyridine-thiocyanate complex, permanganate, and ferrocyanide, respectively. Chromium was determined iodometrically after fusion of the ash with sodium peroxide and solution in water. After ignition of a sample with excess magnesium nitrate and solution of the residue in acid, phosphorus was determined by titrations of the precipitated ammonium phosphomolybdate. Sulfur and chlorine were weighed as the respective barium and silver salts, which were precipitated from a solution of a sample after ignition with a mixture of magnesium oxide and sodium carbonate. Iodine was determined colorimetrically in the water extract of a sample after controlled ignition of the original material with potassium hydroxide. The Gutzeit method was used t o determine arsenic. In the oomposite sample of Milorganite collected in the period 1931to 1932,total boron was determined by titration after separation as the ester by distillation, while in the sample collected during the period 1931 t o 1937 water-soluble boron was determined after extraction with boiling water by means of the quinalizarin colorimetric method (5). The data of Table I1 show that Milorganite contains appreciable amounts of many elements, Because of the diverse sources from which the material comes, one might expect the presence of a t least traces of practically all the elements.
Main Fertilizer Constituents Results of analyses for essential plant nutrients by methods which reflect availability to plants are given in Table 111. The copper, zinc, and manganese soluble in carbonated water and 0.002 N sulfuric acid were determined by extracting 10 grams of 100-mesh Milorganite with 1000 cc. of the respective extractants and then applying the methods of determination mentioned above. The organic and water-soluble sulfur was determined by extraction with hot water after destruction of organic matter with bromine, and then precipitating and weighing as the sulfate. Exchangeable potassium was extracted by leaching with a neutral solution of ammonium acetate. Although nitrogen and phosphoric acid make up the chief portion of the available plant nutrients, the appreciable amounts of other nutrient elements including the minor ones given in the last column may well be of considerable im-
Substances of the hormone type which are capable of promoting plant growth are classified in two groups-namely, the auxins or natural plant hormones found in living plants, and heteroauxin or indole acetic acid which is a produat of animals and microorganisms. Thimann and Dolk (7) and Thimann (6) have shown that the latter type is produced when certain fungi are grown on media containing peptone, and they have devised rather accurate methods of measuring small quantities. Since activated sludge is partly a microbial product, it seemed desirable to make tests for the presence of heteroauxin. Results were negative in every case. Since the biological changes which nitrogenous organics undergo in the soil may be regarded as paralleling the growth of fungi upon media containing peptone, hormone production in the former case should be expected. Soil cultures, each containing 200 grams of sand, 100 grams of soil, and 50 grams of Milorganite were prepared, and after moistening were incubated in open Erlenmeyer flasks in the greenhouse. At intervals of 3 days, one of the cultures was examined for growth-promoting substances by extracting with 95 per cent alcohol, and purifying as recommended by Thimann (6). The product was then tested by the Avena coleoptile method described by Avery et al. (g), which is sensitive to a few tenths of a gamma of heteroauxin. TABLEIV. HETEROAUXIN PRESENT AFTER 10 DAYSIN CULMILORGANITE AND OTHERNITROGENOUS MATERIALS
TURES OF
(Cultures:
50 grams of organics, 100 grams of soil, and 200 grams of sand)
Nitrogenous Substance Mllorganita Cottonseed meal Cantor uomaoe
Percentage Nitrogen 6.04 0.64 6.20
Heteroauxin, Gammas per Culture
1.7 2.4 1.3
Results of these tests showed that measurable quantities of heteroauxin were present in the cultures after a few days of incubation, and that a maximum amount was present after 10 to 14 days of incubation. A continuous decline took place thereafter. Since control cultures gave negative results, i t was evident that the hormone production was dependent upon the Milorganite added. Other common organics were then cultured in a similar manner, and hormone production after 10 days was found to be approximately proportional to the nitrogen contents of the organics added. These results, together with the negative results obtained with two nonprotein sources of nitrogen-ammonium sulfate and ureaare presented in Table IV.
Summary Activated sludge, “Milorganite”, consists approximately of the following substances: protein 37.5 per cent, cellulose 7.0 per cent, fat 6.5 per cent, free iron oxide 6.1 per cent, sand 2.4 per cent, silt 13.4 per cent, clay 14.4 per cent, and water 6.2 per cent. The balance of 6.5 per cent consists of phosphates, sulfates, and compounds containing calcium, magnesium, potassium, aluminum, titanium, sodium, and measurable amounts of manganese, copper, zinc, cobalt, boron, iodine, and many other elements. The appreciable quanti-
MAY 15, 1939
ANALYTICAL EDITION
ties of the minor nutrient elements present, being easily soluble for the most part, may have significant fertilizer value is accounted for in certain cases. The main fertilizer by the nitrogen and available phosphoric acid which are present t o the extent of approximately 6 and 2.5 per cent, respectively. The material has a base-exchange capacity of 22.4 milliequivalents, a property which may be of some value when the material is applied to very sandy soils. Tests made on the material directly failed to reveal the presence of plant hormones. However, after mixing and incubation of the materialwith a sandy soil, hormones of the indole-substituted fatty acid type were produced in amounts comparable to those produced with similarlv treated fish meai, cottonseed castor and tankage* Urea and ammonium to promote hormone production when mixed with the sandy soil.
283
Literature Cited (1) Assoc. official Agr. Chem., Officialand Tentative Methods of Analysis, 2nd ed., p. 117, 1925. (2) Avery, G. S., Burkholder, P. R., and Creighton, H. B., Am. J . Botany, 24, 226 (1937). (3) Berger, K. C., and Truog, E., IND.ENQ.CHEM.,Anal. Ed., in (4) (5)
press.
s.,
Sei. sot. Am. proc., 2, 385 (193,).
Noer, 0. J., J . Am. SOC.Agron., 18, 953 (1926). (6) Thimann, K. V., J . B i d . Chem., 109, 279 (1935). (7) Thimann, K. V., and Dolk, H. E., Bid. Zentr., 53, 49 (1933). (8Thomas, WiS. Agr. ExPt. Sta., Research Bull. 105 (1930). (9) Truog, E., Taylor, J. R., Jr., Pearson, R. W., Weeks, M. E., and Simonson, R. W., Soil Sci. SOC.Am. Proc.,1, 101 (1937). PUBLISEBD with the permission of the director of the Wisconsin Agricultural Experiment Station. This work was supported in part by a fellowship grant from the Milwaukee Sewerage Commission, Milwaukee, Wis.
Laboratory Columns for Close Fractionation Conical Type of Stedman Packing L. B. BRAGG, Foster Wheeler Corporation, Carteret, N. J.
T
HE conical type of Stedman packing was developed by D. F. Stedman in the laboratories of the National Research Council of Canada a t Ottawa and patented in the United States (16),Canada ( l a ) , and elsewhere. Stedman has reported the efficiencies obtainable with conical-type packing 2.5 cm. (1inch) in diameter as determined by testing with mixtures of n-hexane and cyclohexane (IO,11, 13, 14). This packing is being further developed, and three sizes of the conical type have been produced, the operating characteristics of which are presented below.
edges, through the vapor hole in the lowest cone. It then flows through the space between these two cones, practically at right angles to the axis of the column, and out through the vapor opening in the upper cone of the pair. The vapor then divides and flows around the .point where two cones are joined back to back, and across to the side of the column where it first entered the packing. This flow is then repeated until the vapor leaves the packing at the top of the column. There is a continual mixing and separation of liquid and vapor, so that channeling is not possible. The tubing in which the packing is inserted must fit the packing closely, so that any openings between the packing and the tubing are sealed by the liquid to prevent by-passing of the vapor. The underside of the liquid stream
Description of Packing The conical type of packing is made of wire cloth which has been embossed and trimmed into flat, truncated, conical disks. A semicircular hole is cut out of one side of the cone and extends about two thirds of the distance from the ed e of the cone to the flat in the center. The disks are welded togeker alternately back to back and edge to edge, so as to form a regular series of cells, with the holes which serve as vapor passageways located alternately on opposite sides of the section of packing. The construction may be readily understood by reference to Figure 1. The three sizes of packing on which tests are reported herein had nominal diameters of 25 mm. (0.984 inch), 19.0 mm. (0.750 inch), and 9.5 mm. (0.375 inch) and were called Nos. 112, 104, and 105, respectively. The packing is customarily fabricated from stainless-steel wire cloth of 15.75 X 23.6 meshes per cm. (40 X 60 meshes per inch), using wire 0.0229 cm. (0.009 inch) in diameter. It may, however be made of any other material that can be drawn into wires and woven into wire cloth of the proper mesh, in accordance with the particular use to which the packing is to be put. Other mesh sizes will be satisfactory, so long as the packing has sufficient mechanical strength and the surface tension of the liquid is great enough to seal the openings of the mesh and prevent the passage of vapor through the mesh, but certain sizes of mesh and wire diameter are best (11). I n operation the liquid flows along the screen and seals the openings of the mesh. The liquid flows out toward the walls of the column on a cone that is concave downward, and then back toward the center of the column on a cone that is concave upward, which is welded to the first cone at the outer edge. The lower cone is welded to another still lower cone a t the center and the liquid flows through the mesh a t the point of junction, then outward toward the walls on this lower cone, and so on until the liquid dro s off the lowest cone of the column. The vapor enters the spacegetween two cones which are welded around the outer
SIZESOF STEDMAN PACKING, CONICAL TYPE FIGURE 1. THREE
