Beneficiating waste sludges for agricultural use and product made thereby

A method of beneficiating waste sludge which comprises mixing kiln dust with waste sludge, exposing the mixture at ambient temperature without compacting for a time sufficient to produce a disintegratable, friable product which can be applied to land as a soil conditioner.

This invention relates to a method of beneficiating waste water treatment 
sludge and other human, animal, and poultry manures with kiln dust to 
facilitate land application of the waste. 
BACKGROUND AND SUMMARY OF THE INVENTION 
The development of clean water legislation has dramatically increased the 
amount of sludge residue from municiple waste water treatment plants. In 
the late 1960's and early 1970's, there was strong momentum toward 
treating these sludges by incineration. The energy crisis of 1974 and 
subsequent escalation of all energy sources makes incineration both costly 
and an unnecessary use of energy. It has long been clear to 
environmentalists, conservationists, and agronomists that the most 
desirable technology for sludge disposal was land farming utilization. The 
Resource Conservation and Recovery Act of 1976 committed the United States 
to a course of action to utilize waste materials in lieu of disposing of 
them whenever possible if economically feasible. The land farming of 
sludges has always represented the best economic opportunity in most 
cases. However, environmental, sociological, political and administrative 
concerns have created substantial roadblocks for widespread land farming. 
The Environmental Protective Agency (EPA) has reported that less than 30% 
of all waste water treatment sludge is land applied. The balance is either 
disposed in landfills or incinerated. The latter usually costs the 
community more than land farming. In addition, the inherent value of the 
sludge is lost to the community when landfilled or incinerated and 
additional environmental concerns are created. 
Over the past 15 years, billions of dollars have been spent by federal, 
state, and local public bodies on improving and modernizing waste water 
treatment facilities. 
In typical treatment facilities the sludge is developed as follows: The raw 
source enters the plant over grids, which remove large objects. It is then 
usually treated with alum to aid flocculation (lime can be used but a high 
pH at this point in the process is usually undesirable) and moved to the 
primary clarifier. Here the sludge (suspended particles) settles out. At 
this point, the sludge is separated from the effluent. Secondary and 
tertiary treatments of the effluent may produce additional sludge but most 
is generated during primary clarification. 
If the sludge is to be stabilized (as it all should be), it now goes from 
the clarifier to the stabilization process. Many waste water treatment 
plants, which stabilize the sludge, use digestors--either anaerobic or 
aerobic for stabilization. The objective of stabilization is to reduce 
pathogens and volatile solids (organic materials) which in decay create 
offensive odors. The usual digestive period is from 15-30 days. 
Other methods of stabilization are composting, heat and chemical 
stabilization which requires caustic materials to increase the pH of the 
sludge above 12 for at least two hours. This process destroys the 
pathogens. This technology is little used due to the high operating cost 
and unavailability of lime and other caustic materials such as soda ash 
and caustic soda. 
After stabilization, many treatment facilities route the sludge to 
dewatering systems. The three primary systems currently being used are the 
vacuum filter system, the centrifuge system, and the belt pressure system. 
The sludges are pre-treated to aid in flocculation. Usually 
polyelectrolytes (polymers) are used, but some plants which use a vacuum 
filter dewatering system use lime-ferrous chloride combinations in lieu of 
polymers. While these materials may be more expensive than polymers in 
dewatering, the resultant high pH is an advantage in sludge disposal or 
utilization. 
Some plants do not stabilize their sludge at all. The sludge is taken from 
the clarifier, dewatered, and hauled to landfills for disposal or hauled 
to incinerators. 
Most waste water treatment sludge leaves the facility at a pH of about 7. 
If lime is used to precipitate or flocculate phosphorus, to chemically 
stabilize the sludge, or to pre-treat the sludge prior to dewatering with 
a vacuum filter, the pH will be significantly higher. There are many 
distinct advantages to a high pH sludge exiting the plant. 
EPA publications and other published documents are almost unanimous in 
their discussions on the relative costs and problems associated with 
methods of sludge disposal other than land farming. Incineration costs 
have become especially prohibitive. Since 1973 the cost of a barrel of oil 
has increased tenfold. Conservation of both oil and gas have become 
congressionally determined national objectives. Incineration costs are now 
estimated at over $150 per dry ton or $30 per wet ton (20% solids). 
Higher percentage solids sludges will cost less per dry ton and lower 
percentage solids will cost more per dry ton. The cost and wasted energy 
of evaporating water is prohibitive. With incineration, the nutrient and 
organic values of waste water treatment sludges are destroyed, ash 
disposal is a problem, and bacteria are released into the air. With 
incineration, 15-20 gallons of oil or 2500-3500 cubic feet of gas is used 
unnecessarily per wet ton. 
Landfill costs and problems are not much better. Typical costs are running 
at least $20 per wet ton or $100 per dry ton (20% solids). Unstabilized 
sludges create serious environmental concerns relative to leaching and 
ground water contamination. Offensive odors at the treatment plant, in 
transit, and at the landfill operation are a serious concern. The use of 
good land to bury a valuable resource seems idiotic unless the sludge is 
unacceptable and untreatable. A typical patent directed to making landfill 
is U.S. Pat. No. 4,028,130. 
The most reasonable approach to sludge disposal appears to be sludge 
utilization through land farming. The nutrient value of sludge and the 
organic value of sludge will vary depending upon the method used in 
processing it at the waste water treatment facility. The following 
publications discuss these values: Application of Sewage to Cropland, by 
Council for Agricultural Science and Technology; Report No. 64, November 
1976. Research Bulletin 1079 (revised), by Ohio Agricultural Research and 
Development Center. Use of Sewage Sludge in Crop Production, Sommers, 
Nelson and Spies in Energy Management in Agriculture, a publication of the 
Cooperative Extension Service, Purdue University. Applications of Sludges 
and Wastewaters on Agricultural Land; A Planning and Educational Guide, 
Edited by Bernard D. Knezck and Robert H. Miller. 
The aforementioned Research Bulletin 1079 has shown that practically all 
wastewater sludges will have a total value of at least $50 per dry ton. 
This value is derived from phosphate (P.sub.2 O.sub.5), value about $0.018 
lbs. (average percent per dry solids--5.7%); Nitrogen (approximately 67% 
organic nitrogen and 33% ammonia nitrogen), value about $0.15 lb. (average 
percent per dry solids--3.3%); Potash (K.sub.2 O) $0.10 lb. (average 
percent per dry ton--0.4%); and organic materials-average value per dry 
ton of at least $25. 
It would seen that this would immediately result in use of sludges in 
agriculture. However, there are realistic environmental and sociological 
concerns. There are administrative management problems. There are private 
interest groups who do not want to see sludges utilized since such 
utilization creates competition for their fertilizer products. There are 
private interest groups who do not want to see incinerators or land fills 
shut down as the supply or operations of these facilities are their 
business. It has been easier for public leaders to obtain federal funding 
for capital expenditures such as incinerators (presently as much as 90% 
federal participation) than to develop methods and technology to utilize 
the sludge in a manner that is sociologically, environmentally and 
politically acceptable. It is thus necessary that public officials must be 
given the technology to satisfy these concerns. 
The use of waste water treatment sludge in land farming has been limited by 
combinations of at least six realistic concerns and one sociological 
impediment: 
1. Concern for virus or other pathogens in the sludge. 
2. Concern that plants might accumulate heavy metals from the sludge. 
3. Inability of responsible officials to insure liming of soil prior to 
receipt of sludge. 
4. Concern of community--at waste treatment plant, in transit, and at the 
land farm site for offensive odors. 
5. Runoff of sludge to surface waters, thus affecting quality of surface 
water and creating movement of sludge from applied field to neighboring 
community. 
6. Leaching of chemical from sludge to ground water. 
7. A sociological problem is created when farmers obtain the sludge for 
nothing. Their community reacts that the urban area is giving something 
away to a few, but the entire neighboring community takes the perceived 
risk and discomfort so that the urban area can solve its disposal problem. 
If the farmers were paying for a processed sludge, the resistance would be 
significantly reduced. 
In accordance with the invention, the controlled addition of substantial 
monitored quantities of an industrial waste product (kiln dust from cement 
or lime plants) to waste water sludge either during the in-plant 
processing or after it has been processed at the treatment plant, can 
dramatically improve the characteristics of the sludge. Reasonable 
objections to land farming can be eliminated or significantly reduced. 
Kiln dust alone is an excellent, low cost, soil conditioner. Its fine 
particle size makes it difficult to distribute to the soil. When mixed 
with sludge, a process similar to lime soil modification results. The fine 
particles agglomerate during curing, forming a friable material readily 
granulated and easily land applied. The value added to the sludge can be 
redeemed by marketing the combined materials at bargain values to the 
agricultural community or the combined materials can be sold as a feed 
stock to the fertilizer industry. 
In accordance with the invention, a mixture of waste water treatment sludge 
and kiln dust, a by-product of the cement and lime industry, are combined 
to produce an acceptable soil conditioner and partial fertilizer by 
eliminating or significantly reducing undesirable characteristics of each 
material considered separately. The mixture is permitted to cure until it 
is sufficiently cohesive so that it can be readily formed into granulated 
particles by shredding or crushing and the like. The resultant product is 
friable so that upon placement on the ground and exposed to the elements 
as in farming it will break down into small fine particles. 
The soil conditioner will improve the workability of the soil, which will 
improve the water carrying capacity of the soil and which will increase 
the ion exchange capacity of the soil. The partial fertilizer will provide 
macro nutrients such as nitrogen, phosphorus, potassium, calcium, sulfur 
and magnesium and limited quantities of micro nutrients such as 
molybdenum, zinc and copper. 
Difficulties of land applications of sewage sludge were discussed earlier. 
Problems associated with the migratory nature of sludge are particularly 
minimized by this invention. Concerns for fugitive dust associated with 
the land use of dry kiln dust are eliminated or drastically reduced by 
this invention. 
Mixtures of sludge and kiln dust are determined based on the following 
considerations: 
1. Kiln dust, though a by-product, is a costly resource and thus should 
only be used in sufficient quantity to achieve desired granulation and pH 
results. 
2. Preferably approximately 70% of the mixture will be sludge and 30% kiln 
dust. 
3. The percentage of kiln dust may be reduced by: 
a. Increasing the percentage of solids in the sludge. 
b. Using a kiln dust of higher reactivity. 
c. Beneficiating the dust by the addition of a caustic compound, i.e. 
CA(OH).sub.2 or CAO, (up to 15% of total dust). 
d. Increasing the curing time and/or temperature to produce the desired 
cohesiveness. This will vary depending on the needs of the waste water 
treatment plant and the climate. 
4. Sufficient dust must be added to develop sufficient cohesiveness to 
achieve friability through granulation techniques in a time period 
acceptable to the appropriate waste water authority. 
Two primary aspects of this invention are: 
1. The ability of this friable mixture to be handled and stored and yet 
break down where exposed in the field to climatic conditions. This differs 
significantly with other solidification technology which has been 
developed primarily to achieve land fill disposal objectives, i.e. 
minimize leaching through development of structurally durable strength. 
2. This mixture will maintain a desired non-acidic pH much longer than lime 
treated sludges due to the nature and percentages of alkaline material in 
the mixture. Calcium silicate reactions in the kiln dust will also 
minimize the availability of metal ions. A recent study by the United 
States Bureau of mines concludes cement kiln dust is a large volume 
material and a potential resource as a substitute for lime. Any 
environmental considerations are minor, as the results of this extensive 
survey show that United States cement kiln dust is not a hazardous waste 
as defined by current regulations. The blending of sludge and kiln dust 
will result in not only minimizing the availability of undesirable trace 
metals but in dilution as well. 
Typical physical characterization test results for cement kiln dust are set 
forth in the following TABLE 1: 
TABLE 1 
__________________________________________________________________________ 
PHYSICAL CHARACTERIZATION TEST RESULTS FOR CEMENT KILN DUSTS 
TICLE SIZE DISTRIBUTION 
PERCENT PASSING OTHER 
SAMPLE 
TOP 60 200 325 0.02 
0.01 
0.006 BLAINE 
NUMBER 
SIZE MESH 
MESH 
MESH 
mm mm mm SG FINENESS 
pH.sup.c 
__________________________________________________________________________ 
CD-1 100 99 97.5 
87.5 
3 2.76 
9090 11.9 
CD-2 #50 99.6 
96.7 
93 11 0.5 2.78 
4890 11.9 
CD-3 #20 97.5 
83.2 
71 2.5 
0 2.78 
5870 11.9 
CD-4 #50 98.7 
84 70 28 2.76 
7190 11.9 
CD-5 #14 97.2 
71 50 14 2.87 
7550 12.1 
CD-6 #50 99.9 
84 61 19 2.74 
9980 12.1 
CD-7 #50 98.7 
86 76.5 
35 0.3 2.84 
5120 11.9 
CD-8 #50 98.6 
72 52 21.5 2.84 
4610 11.9 
CD-9 #10 96.5 
85.7 
77 1.2 
0.3 
0 2.85 
4940 12.0 
CD-10 100 97.5 
76 2.79 
10760 12.0 
CD-11 #50 99.5 
95.2 
91.5 
55 4.4 
2.2 
2.76 
8130 11.8 
CD-12 #50 99.9 
94 89.5 
77.5 
44 19 2.74 
10370 11.9 
CD-13 #10 97.8 
79.5 
59.5 
21.5 2.84 
7110 11.9 
CD-14 #50 98.6 
80 68 38 2.78 
6810 12.0 
CD-15 #50 99 89 82 67 27 19.3 
2.69 
7090 11.5 
CD-16 #50 99.5 
94 88 63 2.77 
8700 12.0 
CD-17 #50 98.5 
79.3 
63 34.5 2.79 
10010 12.1 
CD-18 #50 99.5 
97.4 
96.3 
80 3 1.3 
2.74 
9120 12.0 
CD-19 #50 99.5 
88.5 
81.2 2.85 
5680 12.1 
CD-20 #50 99.5 
90 80 3.5 2.75 
6090 12.1 
CD-21 #50 97 78 66 4.5 
0 2.79 
4460 12.1 
CD-22.sup.a 
1/2" 32 12 
(99.5%) 
CD-22.sup.b 
#10 79 57.5 
46.5 
28 14 8.5 
2.60 
3740 11.8 
CD-23.sup.a 
1/2" 11 2 
(95%) 
CD-23.sup.b 
#10 76 57 41 29.5 
22 16.8 
2.78 
13900 11.2 
CD-23 #50 99.5 
85.5 
68 2.93 
5630 12.0 
CD-25 100 97.5 
86.5 
0 2.70 
13060 12.0 
CD-26 3/4" 29.5 
17.5 
12.5 
9 2.5 
1.3 
2.48 
6950 12.0 
CD-27 #50 99.5 
86 72 25 0 2.79 
5520 12.0 
CD-28 #50 99.6 
98 95.6 
4.7 
3 2.86 
7370 12.1 
CD-29 #50 99 86 79 2.83 
5600 12.0 
CD-30 #100 98.8 
97.7 
80 2.5 
1.8 
2.76 
8780 11.9 
Calcitic 
Hydrated 100 98 91 0 2.31 
Lime 
__________________________________________________________________________ 
Notes:? 
.sup.a As received. 
.sup.b Ground. 
.sup.c 15 gm in 150 ml distilled, deionized water, stirred 1 minute, pH o 
slurry, (pH of water 7.8). 
Typical chemical characterization test results for cement kiln dust are set 
forth in the following TABLE 2: 
TABLE 2 
__________________________________________________________________________ 
CHEMICAL CHARACTERIZATION TEST RESULTS FOR CEMENT KILN DUSTS 
PERCENT 
SAM- OX- TO- 
PLE LOI IDE LOI 
TAL 
NUM- SO.sub.3 
1050.degree. 
TO- LOI 550.degree. 
CAR- 
BER CaO 
SiO.sub.2 
Al.sub.2 O.sub.3 
MgO 
Na.sub.2 O 
K.sub.2 0 
Fe.sub.2 O.sub.3 
MnO 
TiO.sub.2 
P.sub.2 O.sub.5 
LECO 
C. TAL 150.degree. C. 
C. BON CO.sub.2 
__________________________________________________________________________ 
CD-1 
38.3 
13.2 
4.61 
2.49 
0.15 
3.96 
2.32 
0.12 
0.20 
0.16 
6.74 
25.3 
97.6 
&lt;0.1 
0.87 
6.77 
24.8 
CD-2 
44.5 
17.1 
4.84 
1.15 
0.27 
2.91 
1.97 
0.00 
0.18 
0.12 
3.82 
22.8 
99.7 
0.1 1.71 
5.97 
21.9 
CD-3 
39.1 
15.4 
2.93 
2.63 
0.55 
3.52 
2.13 
0.00 
0.18 
0.06 
8.56 
22.8 
97.9 
0.1 0.93 
6.19 
22.7 
CD-4 
37.2 
12.5 
4.18 
2.02 
0.68 
4.70 
1.51 
0.02 
0.15 
0.16 
6.79 
27.3 
97.3 
0.1 1.99 
6.79 
24.9 
CD-5 
38.0 
15.3 
4.25 
0.91 
0.32 
7.30 
1.83 
0.10 
0.13 
0.15 
7.94 
19.6 
95.8 
0.1 2.13 
5.21 
19.1 
CD-6 
25.8 
9.71 
2.21 
1.13 
1.35 
15.3 
1.77 
0.01 
0.10 
0.04 
17.40 
19.5 
94.2 
&lt;0.1 
3.12 
5.47 
20.1 
CD-7 
41.9 
16.2 
4.11 
1.64 
0.34 
3.22 
2.39 
0.06 
0.18 
0.24 
4.79 
22.9 
98.0 
0.2 2.35 
6.14 
22.5 
CD-8 
39.4 
17.7 
4.07 
0.92 
1.20 
3.90 
2.84 
0.00 
0.16 
0.07 
3.47 
22.7 
96.5 
0.2 2.03 
5.11 
18.7 
CD-9 
41.6 
20.0 
5.76 
2.22 
0.41 
3.76 
2.46 
0.01 
0.27 
0.11 
6.69 
12.7 
95.9 
&lt;0.1 
1.24 
3.16 
11.6 
7.85 
28.8 
CD-10 
45.9 
11.9 
2.92 
1.39 
0.07 
1.54 
2.04 
0.01 
0.14 
0.06 
6.24 
28.2 
100.3 
0.1 1.29 
7.70 
28.2 
6.46 
23.7 
CD-11 
40.8 
13.3 
4.85 
1.02 
0.27 
2.90 
2.26 
0.00 
0.21 
0.10 
6.24 
25.6 
97.5 
&lt;0.1 
1.82 
6.48 
23.8 
CD-12 
44.4 
12.0 
3.13 
1.66 
0.08 
2.86 
1.27 
0.00 
0.12 
0.05 
3.30 
31.8 
100.6 
&lt;0.1 
2.50 
8.67 
31.8 
CD-13 
45.2 
16.8 
3.88 
1.37 
0.18 
1.78 
2.11 
0.00 
0.18 
0.24 
3.72 
23.2 
98.7 
&lt;0.1 
1.67 
6.21 
22.8 
CD-14 
34.6 
15.1 
4.24 
1.83 
0.58 
7.05 
2.06 
0.02 
0.21 
0.07 
8.64 
22.9 
97.2 
0.2 2.82 
5.85 
21.4 
21.3 
CD-15 
19.4 
22.4 
10.0 
0.64 
1.34 
14.1 
4.06 
0.01 
0.42 
0.19 
10.14 
13.2 
96.0 
0.1 3.88 
3.37 
12.4 
CD-16 
37.4 
15.2 
4.75 
1.96 
0.48 
5.03 
2.78 
0.02 
0.21 
0.06 
6.37 
24.0 
98.3 
0.1 1.77 
6.39 
23.4 
CD-17 
26.8 
13.0 
4.50 
0.54 
1.47 
12.4 
2.04 
0.13 
0.18 
0.15 
16.93 
13.5 
91.8 
0.1 2.19 
3.48 
12.8 
CD-18 
47.6 
9.91 
3.08 
1.33 
0.11 
1.08 
1.21 
0.00 
0.11 
0.04 
2.92 
31.6 
99.0 
0.1 1.00 
8.59 
31.5 
CD-19 
41.1 
15.2 
3.92 
1.30 
0.20 
3.39 
2.19 
0.02 
0.16 
0.08 
13.76 
11.7 
93.0 
&lt;0.1 
0.54 
3.13 
11.5 
CD-20 
45.5 
14.0 
3.39 
1.16 
0.28 
2.50 
1.26 
0.00 
0.14 
0.05 
2.40 
28.4 
99.3 
0.3 1.12 
7.52 
27.6 
CD-21 
42.9 
14.9 
4.62 
0.89 
0.14 
3.16 
2.31 
0.00 
0.19 
0.27 
5.54 
22.2 
97.0 
0.3 1.20 
6.26 
23.0 
CD-22 
39.6 
17.6 
4.42 
2.04 
0.20 
2.60 
2.04 
0.01 
0.21 
0.09 
3.75 
26.6 
99.3 
2.8 6.73 
5.60 
20.6 
CD-23 
31.4 
11.7 
3.18 
0.97 
0.13 
1.65 
2.16 
0.01 
0.15 
0.07 
8.24 
40.4 100.0 
1.8 11.85 
3.81 14.0 
CD-24 
57.1 
9.70 
4.18 
1.81 
0.00 
0.22 
0.24 
0.00 
0.15 
0.03 
2.67 
21.1 
97.2 
&lt;0.1 
1.08 
5.52 
20.2 
CD-25.sup.a 2.60 
CD-26 
44.2 
11.9 
3.24 
1.73 
0.27 
2.92 
1.45 
0.02 
0.14 
0.12 
2.40 
30.2 
98.5 
2.3 9.03 
5.48 
20.1 
CD-27 
42.5 
14.3 
3.34 
2.09 
0.44 
5.21 
1.82 
0.03 
0.13 
0.09 
3.10 
23.8 
96.9 
0.1 1.48 
6.04 
22.3 
6.12 
22.4 
CD-28 
49.7 
13.2 
3.24 
1.73 
0.40 
4.03 
1.48 
0.04 
0.13 
0.12 
3.02 
18.7 
95.0 
&lt;0.1 
0.97 
4.96 
18.2 
4.91 
18.0 
CD-29 
47.5 
14.3 
3.03 
1.20 
0.30 
2.02 
1.93 
0.01 
0.12 
0.05 
3.20 
24.1 
97.8 
&lt;0.1 
0.81 
6.35 
23.3 
CD-30 
43.0 
16.0 
3.97 
3.28 
0.28 
2.09 
2.20 
0.01 
0.28 
0.22 
2.15 
27.1 
100.6 
0.1 1.42 
6.70 
24.6 
__________________________________________________________________________ 
NOTE: 
.sup.a Testing to be completed. 
Typical pH characterization test results for lime kiln dust are set forth 
in the following TABLE 3: 
TABLE 3 
__________________________________________________________________________ 
PHYSICAL CHARACTERIZATION TEST RESULTS FOR LIME KILN DUSTS 
TICLE SIZE DISTRIBUTION 
PERCENT PASSING OTHER 
SAMPLE 
TOP 60 200 325 0.02 
0.06 
0.001 BLAINE 
NUMBER 
SIZE MESH 
MESH 
MESH 
mm mm mm SG FINENESS 
pH.sup.b 
__________________________________________________________________________ 
LD-1 #20 99.5 
89.3 
73 0 2.96 
2920 12.0 
LD-2 #50 99.7 
86.5 
40 2.85 
5180 12.0 
LD-3 #10 90.5 
78.3 
65 2.87 
3650 11.9 
LD-4 100 98 49 2.73 
10350 12.0 
LD-5 #10 92.3 
49.5 
4 2.89 
1310 12.0 
LD-6 #10 98.9 
88.5 
69 2.83 
2180 12.0 
LD-7 #10 97 79 56 2.93 
1870 12.0 
LD-8.sup.a 
LD-9.sup.a 
LD-10 #50 98.5 
62.5 
43 23.3 
13 7.6 
2.98 
2090 12.0 
LD-11 #10 84.8 
74 56 3.04 
1750 12.0 
LD-12 #10 80.5 
57 43 19.5 
4.5 2.83 
2630 11.9 
(99.5%) 
__________________________________________________________________________ 
NOTES: 
.sup.a Testing to be completed. 
.sup.b 15 gm in 150 ml distilled, deionized water; stirred 1 minute, pH o 
slurry, (pH of water 7.8). 
Typical chemical characterization test results for lime kiln dust are set 
forth in the following TABLE 4: 
TABLE 4 
__________________________________________________________________________ 
CHEMICAL CHARACTERIZATION TEST RESULTS FOR LIME KILN DUSTS 
PERCENT 
SAM- OX- TO- 
PLE LOI IDE LOI TAL 
NUM- SO.sub.3 
1050.degree. 
TO- 105.degree. 
LOI CAR- 
BER CaO 
SiO.sub.2 
Al.sub.2 O.sub.3 
MgO 
Na.sub.2 O 
K.sub.2 O 
Fe.sub.2 O.sub.3 
MnO 
TiO.sub.2 
P.sub.2 O.sub.5 
LECO 
C. TAL C. 550.degree. C. 
BON CO.sub.2 
__________________________________________________________________________ 
LD-1 
28.5 
9.19 
5.27 
20.5 
0.21 
0.49 
6.82 
0.03 
0.53 
0.13 
6.37 
18.2 
96.2 
0.1 
+1.01.sup.b 
5.13 
18.8 
+0.95 
LD-2 
31.2 
2.46 
0.74 
23.5 
0.00 
0.09 
0.94 
0.00 
0.05 
0.03 
2.80 
37.4 
99.3 
&lt;0.1 
7.73 
10.36 
37.0 
LD-3 
54.5 
9.94 
4.16 
0.49 
0.03 
0.22 
1.98 
0.00 
0.17 
0.08 
7.97 
14.2 
93.8 
&lt;0.1 
1.07 
3.61 
13.2 
LD-4 
44.3 
10.1 
4.92 
3.56 
0.14 
0.38 
1.36 
0.00 
0.24 
0.10 
4.84 
27.5 
97.4 
0.2 
0.66 
6.56 
24.1 
LD-5 
66.1 
1.92 
0.48 
2.16 
0.00 
0.13 
0.43 
0.00 
0.03 
0.09 
1.72 
19.6 
92.6 
&lt;0.1 
1.21 
5.11 
18.7 
LD-6 
56.7 
3.45 
1.83 
1.11 
0.00 
0.21 
0.80 
0.00 
0.06 
0.03 
0.27 
34.4 
98.9 
&lt;0.1 
+0.91.sup.b 
11.40 
41.8 
+0.11 
LD-7 
58.0 
3.21 
1.18 
0.43 
0.00 
0.10 
3.48 
0.00 
0.03 
0.03 
2.20 
27.6 
96.3 
&lt;0.1 
0.38 
9.71 
35.6 
LD-8.sup.a 
LD-9.sup.a 
LD-10 
35.6 
0.62 
0.06 
23.8 
0.00 
0.00 
0.56 
0.02 
0.01 
0.06 
0.87 
36.2 
97.8 
0.1 
0.33 
9.96 
36.5 
LD-11 
62.4 
12.7 
4.85 
0.70 
0.09 
0.19 
1.36 
0.00 
0.21 
0.04 
2.05 
8.47 
93.1 
&lt;0.1 
1.50 
2.30 
8.4 
LD-12 
35.1 
6.41 
1.41 
21.5 
0.02 
0.12 
0.75 
0.00 
0.07 
0.05 
0.05 
35.3 
100.8 
0.1 
6.78 
8.66 
31.8 
__________________________________________________________________________ 
NOTES: 
.sup.a Testing to be completed. 
.sup.b Plus sign indicates gain in weight. 
The addition of kiln dust to waste water treatment sludge beneficiates the 
sludge in many ways: 
1. The pH of the combined materials will rise significantly thus providing 
vastly increased pathogen removal. 
2. The high pH of the combined materials will result in the precipitation 
of heavy metals in the sludge. This fixation process reduces concern that 
these elements will go into solution in the soil and thus penetrate the 
plants. 
3. The inability of responsible officials to monitor preliming requirements 
prior to distribution of sludge on most farmlands has been a constant 
concern of agricultural, environmental, and waste water treatment 
officials. The blending of kiln dust and sludge eliminates that concern. 
4. The blending of kiln dust, a high lime product, with sludge greatly 
reduces offensive odors at the treatment plant, in transit, and on the 
field. 
5. A great concern in past sludge land farming applications has been the 
danger of water run-off to adjacent ditches, streams, areas, etc., causing 
public outcry. The granulation of the sludge through the blending with 
kiln dust eliminates this concern. 
6. Leaching of sludges, particularly in sandy soils, has previously created 
concern for ground water contamination. The granulation by blending with 
kiln dust minimizes these concerns. 
7. The granulated material is much more easily land applied than either the 
current sludge cake or liquid sludge. It facilitates storing for seasonal 
application. 
8. The value added to waste water treatment sludge by blending kiln dust 
with the sludge creates a combined material with significant economic 
value without the many environmental and sociological problems of sludge 
by itself. As such, the product can be sold thus minimizing the often 
heard complaint that certain farmers are "getting something for nothing at 
the community's expense". 
Kiln dust has excellent compounds for soil conditioning and partial 
fertilizing. However, due to its extremely fine particle size, it is very 
difficult to handle and distribute to soils. By blending with waste water 
treatment sludge, it becomes an important part of a system which can 
readily be distributed on farm land without generating air pollution 
(so-called fugitive dust). 
In order to solidify some waste water treatment sludges in friable 
particles, it may be desirable to add fly ash, another industrial waste 
product, in small quantities. 
Additives such as nitrogen, phosphorus and magnesium can easily be 
incorporated at a blending facility to improve the characteristics and 
marketability of the blended sludge and dusts. 
The same solification and beneficiation technology discussed herein can be 
applied to other forms of human, animal, and poultry waste. Kiln dust can 
be added to septic tank wastes, animal and poultry manure to raise the pH, 
to dry the material, to reduce offensive characteristics and to improve 
both the physical and chemical characteristics. 
The addition of kiln dust to waste water treatment, septic tank waste, or 
animal and poultry waste will create one problem. The raising of the pH of 
the combined materials above 9 will cause the release of ammonia. In waste 
water treatment plants, this is a common occurance where lime is utilized. 
This can be corrected by adding a balancing, lower pH material such as 
calcium sulphate or a bituminous fly ash. However, the positive effects of 
high pH in most cases will be more important than the loss of ammonia. 
An important aspect of the invention is the ability to treat sludge in such 
a way as to granulate the material making it possible to be easily spread 
without run-off to surface water and ground water. This prevents migration 
of the sludge, which is an important sociological and environmental 
concern. 
However, as the process will differ depending upon types of sludge, types 
of shredding equipment, value of sludge/dust combinations, needs of soils, 
etc., no firm gradation specifications are realistically possible or 
practical. 
Basically, the method comprises mixing between 10% and 50% kiln dust by dry 
weight with waste water treatment sludge to achieve sufficient 
solidification so that shredding of the combined material will result in a 
granular mixture capable of spreading without emitting fugitive dust 
and/or migratory liquids. 
This combined material will have a pH in excess of 9, so that available 
heavy metals are precipitated or made insoluble, so that odor is reduced, 
so that pathogens are further reduced. 
This combined material will have significant percentages of calcium and 
phosphates and beneficial percentages of nitrogen, sulphur, potassium, and 
in some cases, magnesium. 
Preferably, the process comprises mixing from 10% to 50% kiln dust (either 
lime or cement, old or new) with from 90% to 50% waste water treatment 
sludge, curing the mixture at ambient temperatures at least three days or 
preferably until it achieves sufficient cohesiveness to be granulated, 
shredded, crushed, etc., into particles resembling a bank run sand and 
gravel mixture. Exact mixtures will vary with percent solids of sludge, 
time allowed for curing, pH requirement, and reactivity of kiln dust. 
Preferably, sufficient kiln dust or a combination of kiln dust and caustic 
material (up to 15% of the kiln dusts) is provided to generate a pH in 
excess of 12 for at least two hours to meet EPA criteria for "a process to 
reduce pathogens". 
If the pH is raised to in excess of 10, it has been found that the 
resultant product will maintain a pH above 6.5 for extended periods of 
time such as 90 days or more. 
It has been further found that the mixture can be beneficiated by the 
addition of fine dolomitic limestone in sufficient quantity to supply 
magnesium to the soil and improve the workability of the mixture. 
In addition to use directly in farming, the resultant product can also be 
used as feed stock in fertilizer blends. When used in this manner, it may 
be necessary to reduce the moisture content further. In some cases, it 
will be beneficial to add nitric acid to the kiln dust and sludge 
combination. The use of the kiln dust provides an excellent carrier which 
will minimize crystal growth of calcium nitrate by preventing crystals 
from contacting each other. This same process may be usable and beneficial 
without the use of sludge. Previously, the "caking" effect of calcium 
nitrate has prevented its use in the United States.* 
FNT *Boynton: Lime and Limestone

EXAMPLE I 
Nine mixtures of cement kiln dust or lime kiln dust and untreated waste 
water treatment sludge from Detroit, Mich., were made and were tested for 
pH values and for moisture content. Five additional mixtures of kiln dust 
and sludge with additions of fly ash and/or powdered Ca(OH).sub.2 were 
also made and tested. Two control samples of only sludge were also tested. 
One control sample refers to the six mixtures on one date, the other 
control refers to the eight mixtures made 3.4 and 7 days later. 
Three pound mixtures of kiln dust and sludge (and fly ash and Ca(OH).sub.2 
if used) were thoroughly blended using the paddle attached to the 
planetary drive of the mixer. Mixing time was three minutes. The mixture 
was placed into waxed cardboard cylinders 6 inches in diameter by 12 
inches high. These containers were open at the top to allow some air 
circulation. 
Immediately after mixing, the samples for the initial pH measurement and 
the initial moisture determination were taken. Additional samples for pH 
and moisture determination were taken from the storage container at 4, 72 
and 168 hours after mixing. 
To minimize the strong, objectionable odor associated with the sludge, the 
waxed containers holding the mixtures and the small oven used to dry the 
moisture samples were placed inside the large double-door curing oven. The 
oven had previously been connected to the blower venting the hood. By 
keeping the doors partially open and the hood blower running, a draft was 
induced which carried away much of the odor and most of the heat from the 
drying oven. However, because the drying oven was inside the larger oven, 
it is probable that the containers stored nearest the small oven were 
slightly warmer than those farther away from it. A heat effect such as 
this could explain the large decrease in moisture content of the control 
sample of the fourth day. 
The pH and moisture samples were taken from the cylindrical containers 4, 
72 and 168 hours after mixing. A slurry of 50% by weight distilled, 
deionized water was used to measure the pH. The pH value was recorded 
after the pH electrode had been immersed in the continuously stirred 
slurry for five minutes. 
About 200 grams of mixture was used for moisture determination. After 
drying at least two days at 105.degree. C., the moisture contents were 
calculated on a wet basis by the following formula: 
##EQU1## 
Table 5 lists the weight percentages of kiln dust, fly ash, calcium 
hydroxide, and untreated waste water treatment sludge. It also lists the 
pH values of water slurries of the mixtures and the moisture contents of 
the mixtures. 
Table 6 lists the percentage changes from the initial moisture contents. 
This percentage change was calculated from the following formula: 
##EQU2## 
Because the sludge content of the mixtures varied from 58.5% to 70%, the 
initial moisture content changed. Using the percentage change from the 
initial mixture content should compensate for the unequal initial moisture 
contents. 
TABLE 5 
__________________________________________________________________________ 
pH VALUES OF WATER SLURRIES OF KILN DUST - FLY ASH - SLUDGE MIXTURES AND 
MOISTURE 
CONTENTS OF THESE MIXTURES 
Percentage of pH Values of Slurry of 50% by 
Trenton 
Ad- Weight Kiln Dust - Sludge 
Moisture Content (%) 
Kiln Channel Fly 
mixture 
Sludge 
ture and 50% by Weight Water 
Wet Basis 
Source of 
Dust in 
Ash in in in 4 72 4 72 
Kiln Dust 
Mixture 
Mixture 
Mixture 
Mixture 
Initial 
Hours 
Hours 
7 Days 
Initial 
Hours 
Hours 
7 
__________________________________________________________________________ 
Days 
No. 1 30 None None 70 11.82 
12.15 
12.36 
11.87 
55.6 
55.1 
50.5 
46.6 
No. 2 30 None None 70 10.57 
11.32 
11.42 
10.17 
56.5 
55.3 
51.4 
45.5 
No. 3 30 None None 70 11.85 
11.23 
10.24 
11.35 
56.2 
55.3 
50.2 
43.4 
No. 4 30 None None 70 12.31 
11.68 
10.45 
11.82 
56.8 
55.7 
52.3 
46.7 
No. 4 30 None 1.5 68.5 11.58 
11.65 
10.18 
11.88 
53.8 
56.4 
51.7 
45.8 
No. 4 30 None 2.5 67.5 11.46 
11.68 
10.18 
11.97 
55.4 
56.6 
49.5 
41.8 
No. 4 18 Reclaimed 
None None 70 11.68 
10.84 
10.26 
12.01 
58.1 
57.7 
52.7 
42.5 
No. 3 12 Fresh 
No. 4 22.5 Rec. 
None None 70 11.83 
11.41 
10.26 
11.89 
58.1 
59.2 
53.0 
44.8 
No. 3 7.5 Fresh 
No. 4 40 None None 60 12.20 
11.28 
10.46 
12.10 
50.8 
50.9 
44.4 
36.4 
No. 5 20 20 None 60 10.89 
10.41 
9.83 
10.17 
51.3 
50.5 
44.6 
33.2 
No. 4 20 20 None 60 10.24 
10.17 
11.93 
12.00 
49.8 
49.6 
46.3 
30.2 
No. 4 20 20 1.5 58.5 10.45 
10.20 
12.03 
11.99 
51.0 
50.3 
45.1 
22.8 
Sludge only 
None None None 100 6.85 
ND 7.00 
7.09 
85.0 
83.6 
81.9 
76.8 
(Oct. 1) 
Sludge only 
None None None 100 6.89 
6.95 
6.93 
7.11 
87.8 
86.9 
85.1 
70.7* 
(Oct. 5) 
No. 6 30 None None 70 10.19 
10.27 
10.36 
9.63 
57.3 
56.9 
51.0 
37.1 
No. 7 30 None None 70 11.76 
11.99 
11.93 
12.08 
58.6 
58.4 
52.5 
39.8 
__________________________________________________________________________ 
ND -- Not Determined 
*Possibly caused by proximity of drying oven to container of sludge. 
TABLE 6 
__________________________________________________________________________ 
PERCENTAGE CHANGE FROM INITIAL MOISTURE CONTENT OF MIXTURES OF KILN 
DUST, FLY ASH, AND WASTE WATER TREATMENT SLUDGE FROM DETROIT, MICHIGAN 
Percentage of 
Kiln Trenton Admixture 
Sludge 
Percentage* Change from Initial 
Dust in 
Channel Fly 
in in Moisture Content, Percent 
Source of Kiln Dust 
Mixture 
Ash in Mixture 
Mixture 
Mixture 
4 Hours 
72 Hours 
7 Days 
__________________________________________________________________________ 
No. 1 30 None None 70 -0.9 -9.2 -16.2 
No. 2 30 None None 70 -2.1 -9.0 -19.5 
No. 3 30 None None 70 -1.6 -10.7 -22.8 
No. 4 30 None None 70 -1.9 -7.9 -17.8 
No. 4 30 None 1.5 68.5 +4.8 -3.9 -19.7 
No. 4 30 None 2.5 67.5 +2.2 -12.8 -24.5 
No. 4 18 Reclaimed 
None None 70 -0.7 -9.3 -26.8 
No. 3 12 Fresh 
No. 4 22.5 Rec. 
None None 70 + 1.90 
-8.8 -22.9 
No. 3 7.5 Fresh 
No. 4 40 None None 60 +0.2 -12.6 -28.3 
No. 5 20 20 None 60 -1.6 -13.1 -35.3 
No. 4 20 20 None 60 -0.4 -7.0 -39.4 
No. 4 20 20 1.5 58.5 -1.4 -11.6 -55.3 
Sludge only (Oct. 1) 
None None None 100 -1.6 -3.6 -9.6 
Sludge only (Oct. 5) 
None None None 100 -1.0 -3.1 -19.5 
No. 6 30 None None 70 -0.7 -11.0 -35.3 
No. 7 30 None None 70 -0.3 -10.4 -32.1 
__________________________________________________________________________ 
ND -- Not Determined 
*See Table 5 for moisture contents 
The kiln dust from Source No. 1 had the following composition by weight: 
______________________________________ 
SiO.sub.2 15.01% 
Al.sub.2 O.sub.3 
3.90 
Fe.sub.2 O.sub.3 
2.18 
CaO 41.33 
MgO 2.25 
K.sub.2 O 6.94 
Na.sub.2 O 0.38 
SO.sub.3 7.41 
CO.sub.2 17.67 
H.sub.2 O -- 
LOI 20.38 
Insoluble SiO.sub.2 
-- 
CaO.sub.free 4.58 
Others -- 
______________________________________ 
The kiln dust from Source No. 2 had the physical and chemical 
characteristics as set forth in TABLES 3 and 4 for dust SAMPLE NUMBER 
LD-2. 
The kiln dust from Source Nos. 3 and 4 had the following chemical 
composition: 
______________________________________ 
SiO.sub.2 
15.66% 
Al.sub.2 O.sub.3 
5.91 
Fe.sub.2 O.sub.3 
4.95 
CaO 36.32 
MgO 2.05 
K.sub.2 O 
4.53 
Na.sub.2 O 
0.29 
SO.sub.3 
13.47 
CO.sub.2 
9.76 
H.sub.2 O 
-- 
LOI 12.29 
Insoluble 
2.18 
CaO.sub.free 
13.00 
Others 5.50 
______________________________________ 
The kiln dust from Source No. 5 had the following chemical composition: 
______________________________________ 
SiO.sub.2 
15.90% 
Al.sub.2 O.sub.3 
1.32 
Fe.sub.2 O.sub.3 
1.73 
CaO 51.32 
MgO 2.18 
SO.sub.3 5.38 
Ignition Loss 
23.89 
Na.sub.2 O 
0.40 
K.sub.2 O 
1.80 
______________________________________ 
The kiln dust from Source No. 6 had the physical and chemical 
characteristics as set forth in TABLES 1 and 2 for kiln dust SAMPLE NUMBER 
CD-14. 
The kiln dust from Source No. 7 had the following chemical composition: 
______________________________________ 
Calcium Oxide, Free Lime 
20.83% 
CaO 58.17 
MgO 1.91 
Sulfur Trioxide 5.82 
Silicon Dioxide 6.12 
Fe.sub.2 O.sub.3 1.86 
K.sub.2 O 0.34 
______________________________________ 
EXAMPLE II 
Six mixtures of cement kiln dust, fly ash, fine aggregate, and waste water 
treatment sludge were made for this study. Six additional mixtures were 
made using additions of various combinations of cement kiln dust, fly ash, 
and fine aggregate to the sludge. The cement kiln dust had the properties 
set forth in TABLES 1 and 2, SAMPLE NUMBER CD-14. 
Three pound batches were made of each mixture of sludge and addition. The 
additions were thoroughly blended into the sludge using the paddle 
attached to the planetary drive of the mixer. The mixer was run at the 
slow speed (72 rpm) for three minutes. 
The mixture were stored in polyethylene jars of one or two quart capacity. 
These jars had inside diameters of 4.5 inches and top openings 3.4 inches 
in diameter. The jars were left uncovered to provide access to air. 
The initial moisture content was determined on a wet basis for each mixture 
of sludge and additions. The moisture contents (wet basis) of the sludge 
from each of two cans of wet sludge and from one can of dry sludge were 
also determined. The average values of several determinations are reported 
as the "Initial Moisture Content of Sludge" in TABLE 7. 
Because this study was a preliminary one, the moisture contents of the 
mixtures at seven and 14 days were not measured. Instead, a description is 
given which estimates the hardness and dryness of the mixture. The degree 
of granularity is also described. 
The dry sludge (51% moisture, wet basis) used in mixtures numbered 9 and 10 
could not be broken up into small granules by the action of mixing paddle. 
It was necessary to break up the large, hard chunks of dry sludge in a 
mortar and pestle before mixing the dry sludge with the additions. 
TABLE 7 lists the weight percentages of each component in the mixtures, and 
the initial moisture contents (wet basis) of the sludge used in the 
mixture and of the mixture immediately after blending. Also listed are 
comments on the degree of granularity of the mixtures, and on the hardness 
and dryness after 7 and 14 days. 
The mixtures using dry sludge (Nos. 9 and 10) granulated very well, 
probably because they were hard and granular (after crushing with the 
mortar and pestle) before adding the kiln dust and fly ash. 
Most of the mixtures made from wet sludge did not develop any granularity. 
In the three mixtures which became granular (Nos. 4, 6 and 12) only No. 4 
had granules smaller than 3/4 inch. No correlation between granularity and 
initial moisture content of the mixture can be seen. 
Drying, however, appeared to be more rapid for mixtures which contained 
both cement kiln dust and fly ash than for those mixtures which contained 
only one of these additions. 
TABLE 7 
__________________________________________________________________________ 
Initial 
Initial 
Mix- 
Weight Percentages 
Moisture 
Moisture 
Granularity of 
Estimates of Hardness and 
ture 
of Components of 
Content of 
Content of 
Mixture at of Moisture Content 
No. 
Mixture (%) 
Sludge (%) 
Mixture (%) 
7 Days at 7 and 14 Days 
__________________________________________________________________________ 
#1 33.3% CKD* 
78 50.4 None (single large mass) 
At 7 Days: 
Soft, still wet 
66.7% Sludge At 14 Days: 
Harder, cracks forming in 
large mass as it dries, 
somewhat damp 
#2 25% CKD 78 37.0 None (single large mass) 
At 7 Days: 
Rather soft, still damp 
15% FA* At 14 Days: 
Harder, quite dry 
10% Aggregate 
50% Sludge 
#3 30% CKD 78 48.7 None (single large mass) 
At 7 Days: 
Soft, still wet 
10% Aggregate At 14 Days: 
Harder, quite dry 
60% Sludge 
#4 15% CKD 78 47.5 Good(3/4" to 1/4" granules) 
At 7 Days: 
Rather soft, still damp 
15% FA At 14 Days: 
Moderately hard but can be 
10% Aggregate broken easily, quite dry 
60% Sludge 
#5 30% CKD 78 23.7 None (single large mass) 
At 7 Days: 
Moderately hard, slightly 
damp 
30% FA At 14 Days: 
Hard, nearly dry 
10% Aggregate 
30% Sludge 
#6 35% CKD 78 24.2 Coarse (about 3/4" granules 
At 7 Days: 
Moderately hard, slightly 
damp 
35% FA and one 21/2" ball) 
At 14 Days: 
Hard, nearly dry 
30% Sludge 
#7 25% CKD 78 38.1 None (single large mass) 
At 7 Days: 
Moderately hard, somewhat 
damp 
25% FA At 14 Days: 
Hard, quite dry 
50% Sludge 
#8 20% CKD 78 37.4 None (single large mass) 
At 7 Days: 
Moderately hard, somewhat 
damp 
20% FA At 14 Days: 
Hard, quite dry (Mixture 
10% Aggregate #8 appears nearly the same 
50% Sludge as mixture #7) 
#9 20% CKD 51 29.2 Excellent At 7 Days: 
Moderately hard, quite dry 
20% FA (.about.#8 mesh) 
At 14 Days: 
Hard, dry 
60% Sludge** 
(Dry) 
#10 
10% CKD 51 37.5 Very Good At 7 Days: 
Moderately hard, quite dry 
10% FA (granules up to 3/8") 
At 14 Days: 
Hard, dry 
10% Aggregate 
70% Sludge** 
(Dry) 
#11 
20% CKD 93 37.2 None (single large mass) 
At 7 Days: 
Soft, still damp 
20% FA At 14 Days: 
Harder, moderately dry 
20% Aggregate 
40% Sludge 
#12 
25% FA 93 46.9 Very Coarse At 7 Days: 
Soft, still wet 
25% Aggregate At 14 Days: 
Soft, damp 
50% Sludge 
__________________________________________________________________________ 
EXAMPLE III 
Five mixtures of waste water treatment sludge and various combinations of 
cement kiln dust, fly ash, and industrial grade Ca(OH).sub.2 were made and 
tested. One mixture contained only sludge and cement kiln dust. Two other 
mixtures contained sludge, cement kiln dust, and fly ash. Two additional 
mixtures were made of sludge, cement kiln dust, fly ash, and Ca(OH).sub.2. 
In addition, a control sample of sludge only was tested. 
Three pound mixtures of sludge and cement kiln dust (and fly ash and 
Ca(OH).sub.2 were used) were thoroughly blended using a paddle attached to 
the planetary drive of the mixer. Mixing time was three minutes. The 
mixture was placed into waxed cardboard cylinders 6 inches in diameter by 
12 inches high. These containers were open at the top to allow some air 
circulation. 
Immediately after mixing, the samples for the initial pH measurement and 
the initial moisture determination were taken. Additional samples for pH 
and moisture determination were taken from the storage container at 4, 72 
and 168 hours after mixing. 
To minimize the strong, objectionable odor associated with the sludge, the 
waxed containers holding the mixtures and the small oven used to dry the 
moisture samples were placed inside the large double-door curing oven. The 
oven had previously been connected to the blower venting the hood. By 
keeping the doors partially open and the hold blower running, a draft was 
induced which carried away much of the odor from the open containers and 
most of the heat from the oven used to dry the moisture samples. 
The pH and moisture samples were taken from the cylindrical containers at 
4, 72 and 168 hours after mixing. The pH of a slurry of 50% by weight 
sludge-CKD-F/A mixture and 50% by weight distilled, deionized water was 
measured. The pH value was recorded after the pH electrode had been 
immersed in the continuously stirred slurry for five minutes. 
About 200 grams of mixture was used for moisture determination. After 
drying at least two days at 105.degree. C., the moisture contents were 
calculated on a wet basis by the following formula: 
##EQU3## 
Table 8 lists the weight percentages of kiln dust, fly ash, calcium 
hydroxide, and waste water treatment sludge. It also lists the pH values 
of water slurries of the mixtures and the moisture contents of the 
mixtures. 
The data in Table 8 indicate the cement kiln dust alone is the most 
effective to drying sludge. Fly ash in the proportions tested does not 
seem to aid drying, but it does increase the pH at four hours and at seven 
days. 
It can be seen that these tests show the ability of kiln dust, kiln 
dust/fly ash, kiln dust/fly ash/lime, and kiln dust/lime systems to 
stabilize and solidify low percentage solids waste water treatment sludge. 
This technology provides dewatering, stabilization, and solidification in 
a single process. 
TABLE 8 
__________________________________________________________________________ 
PERCENTAGE OF pH Values of Slurry of 50% by Weight 
Cement Kiln 
Fly Ash 
Ca(OH).sub.2 
Sludge 
Cement Kiln Dust - Fly Ash - Sludge 
Moisture Content (%) 
Dust in 
in in in Mixture & 50% by Weight Water 
Wet Basis 
Mixture 
Mixture 
Mixture 
Mixture 
Initial 
4 Hours 
72 Hours 
7 Days 
Initial 
4 Hours 
72 
7 
__________________________________________________________________________ 
Days 
30 None None 70 12.11 
11.88 
12.06 12.03 
64.1 54.5 47.0 15.8 
15 15 None 70 11.88 
12.28 
11.58 12.03 
61.6 58.0 51.6 20.9 
20 20 None 60 12.04 
12.23 
11.83 12.32 
57.8 50.7 44.8 23.3 
15 15 1 69 11.98 
12.35 
11.93 12.28 
67.4 57.4 54.4 24.7 
15 15 2 68 12.07 
12.38 
12.26 12.47 
66.7 60.5 54.3 25.9 
0 0 0 100 6.48 
6.58 
6.42 7.23 
98.0 98.0 97.7 96.3 
__________________________________________________________________________ 
It can be seen that these tests clearly show the ability of kiln dusts to 
solidify waste water treatment sludge so that it can be granulated and 
easily spread without emitting fugitive dust or migatory liquids.