U.S. patent number RE38,238 [Application Number 10/117,082] was granted by the patent office on 2003-08-26 for method for treating wastewater sludge.
This patent grant is currently assigned to N-Viro International Corp.. Invention is credited to Jeffrey C. Burnham, John P. Nicholson.
United States Patent |
RE38,238 |
Nicholson , et al. |
August 26, 2003 |
Method for treating wastewater sludge
Abstract
A method of decontaminating wastewater sludge to a level that
meets or exceeds USEPA Process to Further Reduce Pathogens
standards, wherein lime or kiln dust and/or other alkaline
materials are mixed with wastewater sludge in sufficient quantity
to raise the pH of the mixture to 12 and above for a predetermined
time and drying the resulting mixture.
Inventors: |
Nicholson; John P. (Toledo,
OH), Burnham; Jeffrey C. (Naples, FL) |
Assignee: |
N-Viro International Corp.
(Toledo, OH)
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Family
ID: |
26692717 |
Appl.
No.: |
10/117,082 |
Filed: |
April 8, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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019888 |
Feb 27, 1987 |
4781842 |
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Reissue of: |
149575 |
Jan 28, 1988 |
04902431 |
Feb 20, 1990 |
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Current U.S.
Class: |
405/129.27;
210/764; 210/916; 71/13 |
Current CPC
Class: |
C02F
1/50 (20130101); C02F 11/13 (20190101); C02F
1/02 (20130101); C02F 11/18 (20130101); C02F
11/12 (20130101); C05F 7/00 (20130101); Y02A
40/20 (20180101) |
Current International
Class: |
C05F
7/00 (20060101); C02F 11/18 (20060101); C02F
11/12 (20060101); C02F 1/50 (20060101); C02F
1/02 (20060101); C02F 011/14 () |
Field of
Search: |
;405/129.27 ;210/764,916
;71/13 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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25 23 628 |
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Dec 1976 |
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DE |
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28 00 915 |
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Jan 1978 |
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DE |
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Other References
Complaint, N-Viro International Corp. v. The City of Warren, Ohio,
No. 4:00CV531 (N.D. Ohio), Feb. 25, 2000. .
Answer and Counterclaims, N-Viro International Corp. v. The City of
Warren, Ohio, No. 4:00CV531 (N.D. Ohio), Apr. 17, 2000. .
Reply to Counterclaims, N-Viro International Corp. v. The City of
Warren, Ohio, No. 4:00CV531 (N.D. Ohio), May 8, 2000. .
Stipulation of Dismissal, N-Viro International Corp. v. The City of
Warren, Ohio, No. 4:00CV531 (N.D. Ohio), Sep. 14, 2000. .
Amended Complaint, RDP Technologies, Inc. v. N-Viro International
Corp., No. 00-697-RRM (D. Del.), Oct. 13, 2000. .
Answer to Amended Complaint, RDP Technologies, Inc. v. N-Viro
International Corp., No. 00-697-RRM (D. Del.), Jan. 5, 2001. .
Joint Pretrial Order, RDP Technologies, Inc. v. N-Viro
International Corp., No. 00-697-RRM (D. Del.), Oct. 19, 2001
(including Exhibits 1-6 and 11-14). .
Expert Report of Joseph B. Farrell, RDP Technologies, Inc. v.
N-Viro International Corp., No. 00-697-RRM (D. Del.), Jun. 1, 2001
(pertinent references listed separately). .
Rebuttal Expert Report of Robert S. Reimers, PH.D., RDP
Technologies, Inc. v. N-Viro International Corp., No. 00-697-RRM
(D. Del.), Jul. 26, 2001 (pertinent references listed separately).
.
Consent Judgment, RDP Technologies, Inc. v. N-Viro International
Corp., No. 00-697-RRM (D. Del.), Oct. 31, 2001. .
R.S. Reimers et al., "Persistence of Pathogens in Lagoon-Stored
Sludge," EPA 600/2-89/015, Apr. 1989. .
T. Kovacik, "Successful Recycling for Sludge and Solid Waste,"
presented to the Biocycle Southeast Conference '87, Nov. 5, 1987.
.
D. Angelbeck et al., "A New, Innovative Sludge
Stabilization/Management Process: Cement Kiln Dust (CKD) Alkaline
Stabilization Compared to Anaerobic Digestion--An Economic
Analysis," presented to the 16th Annual Conference of the Water
Pollution Control Federation, Oct. 5, 1987. .
"Design Manual: Dewatering Municipal Wastewater Sludges," EPA
625/1-87/014, Sep. 1987. .
"Toledo Puts Its Sludge Out to Pasture," Chemical Week, Sep. 2,
1987. .
"`N-Viro's Treatment of Sludge with Kiln Dust Most Economical
Method` According to Professional," Sylvania Herald, Aug. 5, 1987.
.
"Alkaline Treatment and Utilization of Municipal Wastewater
Sludges," presented to the Water Pollution Control Dept. of the
U.S. EPA by the Nat'l Kiln Dust Management Association and the
Nat'l Lime Association, Mar. 25, 1987. .
News Release by Medical College of Ohio, "Thomas Edison Grant
Award," Dec. 22, 1986. .
J. Burnham, "The Effect of Cement Kiln Dust and Lime on
Microorganism Survival in Toledo Municipal Waste Water Sludges,"
Nov. 26, 1986. .
J. Burnham, "The Effect of Cement Kiln Dust and Lime on
Microorganism Survival in Toledo Municipal Waste Water Sludges,"
Nov. 1, 1986. .
News Release by City of Toledo, Ohio Dept. of Public Utilities,
Oct. 6, 1986. .
L. Ruggiano, "Innovative Sludge Management: Imagination and
Technology Go a Long Way to Solve a City's Sludge Problem," Water
Pollution Control Association of Pennsylvania Magazine, May-Jun.
1986, 42-43. .
R.S. Reimers et al., "Project Summary: Investigation of Parasites
in Sludges and Disinfection Techniques," EPA 600/S1-85/022, Jan.
1986. .
R.S. Reimers et al., "Investigation of Parasites in Sludges and
Disinfection Techniques," EPA 600/1-85/022, Nov. 1985. .
W. Whittington, Memo. re "Application of 40 CFR Part 257
Regulations to Pathogen Reduction Preceding Land Application of
Sewage Sludge or Septic Tank Pumpings," U.S. EPA, Nov. 6, 1985.
.
"Sludge Stabilization and Conditioning at the Toledo Wastewater
Treatment Plant," presented to the 6th Annual International
Conference on Economic and Environmental Utilization of Kiln
Dust/Fly Ash Technology, Feb. 20, 1985. .
T. Marcinkowski, "Decontamination of Sewage Sludges with
Quicklime," Waste Management & Research, 55-64, 1985. .
"Mixer Saves Sludge Costs," Utah Waterline, Sep. 12, 1984. .
M. Iacoboni et al., "Project Summary: Windrow and Static Pile
Composting of Municipal Sewage Sludges," EPA 600/S2-84-122, Sep.
1984. .
"Use and Disposal of Municipal Wastewater Sludge," EPA
625/10-84-003, Sep. 1984. .
J. Montgomery, "Technology Evaluation of Brown Bear.TM. Tractor for
Sludge Dewatering," Sep. 1984. .
R. Ward et al., "Pathogens in Sludge: Occurrence, Inactivation, and
Potential for Regrowth," Sandia National Labs. Publ. No. SAND
83-0557, Jul. 1984. .
R.S. Reimers et al., "Parasites in Southern Sludges and
Disinfection by Standard Sludge Treatment," EPA 600/2-81-166, Sep.
1981. .
R. Otoski, "Project Summary: Lime Stabilization and Ultimate
Disposal of Municipal Wastewater Sludges," EPA 600/S2-81-076, Jun.
1981. .
Camp, Dresser, and McKee, Inc., "Lime Stabilization and Ultimate
Disposal of Municipal Wastewater Sludges," EPA 600/2-81-076, May
1981. .
G. Earnshaw, "Best of Both (Composting) Worlds," Sludge, May-Jun.
1980, 15-19. .
Criteria for Classification of Solid Waste Disposal Facilities and
Practices, 44 Fed. Reg. 53460-53464, Sep. 13, 1979 (codified at 40
C.F.R. .sctn. 257). .
"Process Design Manual for Sludge Treatment and Disposal," EPA
625/1-79-011, Sep. 1979. .
L. Andersson, "Lime Treatment of Sewage Sludge," Sep. 22, 1978.
.
R.F. Noland et al., "Full Scale Demonstration of Lime
Stabilization," EPA 600/2-78-171, Sep. 1978. .
J.P. Brannen et al., "Inactivation of Ascaris Lumbricoides Eggs by
Heat, Radiation, and Thermoradiation," Sandia National Labs. Publ.
No. SAND 75-0163, Jul. 1975. .
C. Counts and A. Shuckrow, "Lime Stabilized Sludge: Its Stability
and Effect on Agricultural Land," EPA 670/2-75-012, Apr. 1975.
.
"Municipal Sludge Management," Proceedings of the Nat'l Conference
on Municipal Sludge Management, Jun. 11-13, 1974. .
J.B. Farrell et al., "Lime Stabilization of Primary Sludges," J.
Wat. Poll. Contr. Fed., No. 1, 113-122, Jan. 1974. .
E. Cram, "The Effects of Sludge Digestion, Drying and Supplemental
Treatment on Eggs of Ascaris lumbricoides," Proceedings of the
Helminthological Society of Washington, vol. 11, No. 1, Jan. 1944.
.
"Developments in Dewatering," BioCycle, 28 (undated). .
Chicago Drying Cells and St. Paul Compost, BioCycle, 38 (undated).
.
Product Application Reviews for Brown Bear auger tractor, Brown
Bear Corp. (undated)..
|
Primary Examiner: Hoey; Betsey Morrison
Attorney, Agent or Firm: Kenyon & Kenyon
Parent Case Text
.Iadd.This application is a reissue of U.S. Pat. No. 4,902,431,
which is a continuation-in-part of application Ser. No. 07/019,888
filed Feb. 27, 1987, now U.S. Pat. No. 4,781,842..Iaddend.
Claims
We claim:
1. A method of treating wastewater sludge to provide a fertilizer
for agricultural lands which can be applied directly to the lands
which consists essentially of the following steps: mixing said
sludge with at least one alkaline material.[.; wherein.]. .Iadd.,
.Iaddend.the amount of added material mixed with said sludge being
sufficient to raise the pH of said mixture to at least 12 and to
hold the pH of greater than 12 for at least 7 days .[.,.]. .Iadd.;
.Iaddend.and .Iadd.actively .Iaddend.drying said mixture for at
least 30 days and until a minimum solids concentration of 65%
solids is reached, the amount of added material being also
sufficient to maintain the pH above 12 until the sludge solids
achieve at least 60% solids by weight, the amount of added material
mixed with said sludge and the length of time of drying being
sufficient to reduce significantly offensive odor of the sludge to
a level that is tolerable .[.;.]. .Iadd., .Iaddend.to reduce animal
viruses therein to less than one plaque forming unit per 100 ml of
said sludge.[.;.]. .Iadd., .Iaddend.to reduce pathogenic bacteria
therein to less than three colony forming units per 100 ml of said
sludge .[.;.]. .Iadd., .Iaddend.to reduce parasites therein to less
than one viable egg per 100 ml of said sludge .[.;.]. .Iadd.,
.Iaddend.to reduce vector attraction to said sludge .[.;.]. and to
prevent significant regrowth of the pathogenic
microorganisms.Iadd., while being insufficient to eliminate all
beneficial non-pathogenic microorganisms from the
sludge.Iaddend..
2. The method set forth in claim 1 wherein the added material
comprises kiln dust and the amount of added material comprises
about 35% by weight of the sludge to reduce the odor to a level
that is tolerable in a closed room even though the pH may drop
below 9 during the drying, and maintain that odor control
indefinitely even though said mixture is exposed to climatic
conditions.
3. The method set forth in claim 1 wherein the amount of added
material mixed with said sludge and the length of time of drying is
sufficient to reduce the odor to a level that is tolerable in a
closed room even though the pH may drop below 9 during the drying,
and maintain that odor control indefinitely even though said
mixture is exposed to climatic conditions.
4. The method set forth in claim 1 wherein the alkaline material is
selected from the group consisting of lime, cement kiln dust and
lime kiln dust to form a mixture.
5. A method of treating wastewater sludge to provide a fertilizer
for agricultural lands which can be applied directly to the lands
which consists essentially of the following steps: mixing said
sludge with at least one alkaline material.[.; wherein.]. .Iadd.,
.Iaddend.the amount of added material mixed with said sludge being
sufficient to raise the pH of said mixture to at least 12 for at
least 72 hours .[.,.]. .Iadd.;.Iaddend. concurrently with the high
.Iadd.pH.Iaddend. .Iadd.pH, .Iaddend.heating the mixture to at
least 50.degree. C., but not at a temperature sufficient to cause
sterilization, the amount of heat being sufficient that the sludge
stored in a static condition will be maintained at a temperature of
at least 50.degree. C. for at least 12 hours .[.,.]. .Iadd.;
and.Iaddend. .Iadd.actively drying said mixture until a minimum
solids concentration of 50% solids is reached,.Iaddend. the amount
of added material mixed with said sludge.Iadd., the heating,
.Iaddend.and the length of time of drying being sufficient to
reduce significantly offensive odor of the sludge to a level that
is tolerable .[.;.]. .Iadd., .Iaddend.to reduce animal viruses
therein to less than one plaque forming unit per 100 ml of said
sludge .[.;.]. .Iadd., .Iaddend.to reduce pathogenic bacteria
therein to less than three colony forming units per 100 ml of said
sludge .[.;.]. .Iadd., .Iaddend.to reduce parasites therein to less
than one viable egg per 100 ml of said sludge .[.;.]. .Iadd.,
.Iaddend.to reduce vector attraction to said sludge .[.;.]. and to
prevent significant regrowth of the pathogenic microoganisms.Iadd.,
while being insufficient to eliminate all beneficial non-pathogenic
microorganisms from the sludge..Iaddend.
6. The method set forth in claim 5 wherein the added material
comprises kiln dust and the amount of added material comprises
about 35% by weight of the sludge to reduce the odor to a level
that is tolerable in a closed room even though the pH may drop
below 9 during the drying, and maintain that odor control
indefinitely even though said mixture is exposed to climatic
conditions.
7. The method set forth in claim 6 wherein the amount of added
material mixed with said sludge and the length of time of drying is
sufficient to reduce the odor to a level that is tolerable in a
closed room even though the pH may drop below 9 during the drying,
and maintain that odor control indefinitely even though said
mixture is exposed to climatic conditions.
8. The method set forth in claim 5 wherein the alkaline material is
selected from the group consisting of lime, cement kiln dust and
lime kiln dust to form a mixture.
Description
This invention relates to a method of treating wastewater sludge
designed to decontaminate the sludge so that it can be safely
applied as fertilizer to agricultural lands.
BACKGROUND OF THE INVENTION
Romans used lime to disinfect and deodorize human waste. The use
has continued throughout the development of civilization. However,
prior to this invention, the use of lime for wastewater, sludge
treatment has been severely limited by governmental regulations
including the United States Environmental Protection Agency
(EPA).
The EPA has promulgated rules governing the type of processes that
can be used to treat wastewater sludge.
Under 40 CFR 257, a Process to Further Reduce Pathogens (PFRP) (See
p. 5,6) must be used where sewage sludge or septic tank pumpings
are to be applied to a land surface or are incorporated into the
soil, and crops for direct human consumption are to be grown on
such land within eighteen (18) months subsequent to application or
incorporation.
A Process to Significantly Reduce Pathogens (PSRP) (See p. 5) must
be used where sewage sludge or septic tank pumpings are to be
applied to a land surface or incorporated into the soil and the
public will have access to such land within twelve (12) months
subsequent to application or incorporation, or grazing animals,
whose products are consumed by humans, will have access to such
land within one (1) month subsequent to application or
incorporation.
Appendix II of 40 CFR 257 classifies the following as PSRP and PFRP
processes:
A. Processes to Significantly Reduce Pathogens Aerobic digestion:
The process is conducted by agitating sludge with air or oxygen to
maintain aerobic conditions at residence times ranging from 60 days
at 15.degree. C. to 40 days at 20.degree. C., with a volatile
solids reduction of at least 38 percent. Air Drying: Liquid sludge
is allowed to drain and/or dry on under-drained sand beds, or paved
or unpaved basins in which the sludge is at a depth of nine inches.
A minimum of three months is needed, two months of which
temperatures average on a daily basis above 0.degree. C. Anaerobic
digestion: The process is conducted in the absence of air at
residence times ranging from 60 days at 20.degree. C. to 15 days at
35.degree. to 55.degree. C., with a volatile solids reduction of at
least 38 percent. Composting: Using the within-vessel, static
aerated pile or windrow composting methods, the solid waste is
maintained at minimum operating conditions of 40.degree. C. for 55
days. For four hours during this period the temperature exceeds
55.degree. C. Lime Stabilization: Sufficient lime is added to
produce a pH of 12 after 2 hours of contact. Other methods: Other
methods or operating conditions may be acceptable if pathogens and
vector attraction of the waste (volatile solids) are reduced to an
extent equivalent to the reduction achieved by any of the above
methods.
B. Processes to Further Reduce Pathogens Composting: Using the
within-vessel composting method, the solid waste is maintained at
operating conditions of 55.degree. C. or greater for three days.
Using the static aerated pile composing method, the solid waste is
maintained at operating conditions of 55.degree. C. or greater for
three days. Using the windrow composting method, the solid waste
attains a temperature of 5.degree. C. or greater for at least 15
days during the composting period. Also, during the high
temperature period, there will be a minimum of five turnings of the
windrow. Heat drying: Dewatered sludge cake is dried by direct or
indirect contact with hot gases, and moisture content is reduced to
10 percent or lower. Sludge particles reach temperatures well in
excess of 80.degree. C., or the web bulb temperature of the gas
stream in contact with the sludge at the point where it leaves the
dryer is in excess of 80.degree. C.
Heat treatment: Liquid sludge is heated to temperatures or
180.degree. C. for 30 minutes. Thermophilic Aerobic Digestion:
Liquid sludge is agitated with air or oxygen to maintain aerobic
conditions at residence times of 10 days at 55-60.degree. C., with
a volatile solids reduction of at least 38 percent. Other methods:
Other methods of operating conditions may be acceptable if
pathogens and vector attraction of the waste (volatile solids) are
reduced to an extent equivalent to the reduction achieved by any of
the above methods. Any of the processes listed below, if added to
the processes described in Section A above, further reduce
pathogens. Because the processes listed below, on their own, do not
reduce the attraction of disease vectors, they are only add-on in
nature. Beta ray irradiation: Sludge is irradiated with beta rays
from an accelerator at dosages or at least 1.0 megarad at room
temperature (ca. 20.degree. C.). Gamma ray irradiation: Sludge is
irradiated with gamma rays from certain isotopes, such as .sup.60
Cobalt and .sup.137 Cesium, at dosages of at least 1.0 megarad at
room temperature (ca. 20.degree. C.). Pasteurization: Sludge is
maintained for at least 30 minutes at a minimum temperature of
70.degree. C. Other methods: Other methods of operating conditions
may be acceptable if pathogens are reduced to an extent equivalent
to the reduction achieved by any of the above add-on method.
Prior to this invention, many concerns have been raised about the
long term disinfection and stabilization capability of lime
treatment. Parrel et al, in "Lime Stabilization of Primary
Sludges", Journal of Water Pollution Control Fed 46, 113 Jan. 1974
published by USEPA, states: "Lime stabilization does not make the
sludges chemically stable. The pH eventually falls and surviving
bacteria may return if conditions are favorable. . .higher
organisms such as Ascaris survive short term exposure to pH of 11.5
and possibly long term exposure."
In January 1979, the EPA published a Wastewater Sludge Manual (EPA
625/1-79-001) titled "Process Design Manual for Sludge Treatment
and Disposal" which states: "Lime stabilizations a very simple
process. Its principal advantages over other stabilization
processes are low cost and simplicity of operation. . .lime
addition does not make sludges chemically stable; if pH drops below
11.0, biological decomposition will resume producing noxious odors.
Second, the quantity of sludge for disposal is not reduced as it is
by biological stabilization methods. On the contrary, the mass of
dry sludge is increased by the lime added and by the chemical
precipitates that derive from the addition. Thus because of the
increased volume, the costs of transport and ultimate disposal are
often greater for lime stabilized sludges than for sludge
stabilized by other method. . .quantitative observation under a
microscope has shown substantial survival of higher organisms, such
as hook worms, amoebic systs and Ascaris ova after contact time of
24 hours at high pH."
Reimers, Englande et al (EPA 600/2-81-166) reported that:
"Application of like to primary aerobic digested and anaerobic
digested sludge was found to be effective with greater than 80%
reduction of Ascaris viability in 5 days following aerobic
digestion at a lime dosage of about 1000 mg/gram of sludge solids
(one part lime to one part sludge solids). . . In the case of the
35.degree. C. aerobically-digested sludge, there was no apparent
effect of lime on the viability of Ascaris eggs at dosages up to
3000 mg of lime per gram of dry sludge solids under anaerobic
conditions, in the period of 20 days. However, under aerobic
conditions, a 98% reduction of viable Ascaris eggs was observed
within one hour at dosages greater than 1000 mg of lime per gram of
dry sludge solid, but only 77% reduction of the viable eggs was
observed at a dosage of 100 mg lime per gram of dry sludge solids
after 20 days. The explanation of these differentials is not
apparent."
In July 1984, the Sandia National Laboratories published a report
titled "Pathogens in Sludge Occurrence, Inactivation and Potential
for Regrowth" which states: "To summarize the effects of lime on
sludge pathogens viruses are destroyed by high pH values, although
it has not been shown that viruses within sludge itself are
inactivated; parasite ova are resistant to high pH, and most will
probably survive lime treatment; bacteria are rapidly inactivated
at pH 12 but, because of pH decreases at levels suitable for
bacteria growth, their numbers increase with time."
In October 1984, the EPA published a report (EPA 625/10-84-003)
titled "Use and Disposal of Municipal Wastewaster Sludge" which was
the basis for future regulations. Section 3 of the report states:
"If crops for direct human consumption are grown within 18 months
of sludge application, sludge must be treated with a PFRP. These
processes destroy pathogenic bacteria, viruses and protozoa as well
as parasites in most cases by exposing the sludge to elevated
temperatures over a period of time."
On November 6, 1985 the EPA issued a memorandum regarding
application of 40 CFR 257 regulations to pathogen reduction
preceding land application of sewage sludge or septic tank
pumpings. One of the purposes of issuing the memorandum was to
outline procedures to enable enforcement agents to determine
whether processes other than those listed in the regulation (40 CFR
257) qualify as a PFRP process. To qualify a process as a PSRP, one
must demonstrate that the process reduces animal viruses by one log
and pathogenic bacterial densities by at least two logs and must
reduce the vector attractiveness such that vectors, like flies or
rats, are not attracted to the sludge. To qualify a new process as
PFRP, one must demonstrate reduction of pathogenic bacteria, animal
viruses, and parasites "below detectable limits" of one (1) plaque
forming unit (PFU) per 100 ml of sludge for animal viruses; three
(3) colony forming units (CFU) per 100 ml of sludge for pathogenic
bacteria (Salmonella sp.); and one (1) viable egg per 100 ml of
sludge for parasites (Ascaris sp.). Vector attractiveness must also
be reduced for PFRP.
If only PSRP disinfective is utilized, land application for
fertilization purposes is controlled by EPA restrictions (it cannot
be used on root crop: "40 CFR 257"). If the process achieves PFRP
criteria these restrictions are eliminated ("40 CFR 257").
In my U.S. Pat. No. 4,554,002, it was shown that kiln dust could be
used to reduce pathogens and dry wastewater sludge prior to land
application.
Roediger, U.S. Pat. No. 4,270,279, describes a method of drying and
sterilizing sewage sludge wherein sheet-like sewage sludge is
broken up into ball-like sludge particles and dusting the outer
surface only with quicklime. This technology utilizes exothermic
heat generated from the reaction of adding H.sub.2 O to quick lime
to sterilize the sludge. This heat sterilization is typical to the
traditional aforementioned PFRP processes. To this date, the EPA
has not approved a petition for approval of this technology as a
PSRP process. Moreover, there are problems with this method. If
this method actually sterilizes the sludge, it would kill all life
forms contained in the sludge, whether they were pathogenic or
beneficial non-pathogenic microorganisms. In contrast, the present
invention decontaminates sludge, killing pathogens to a level below
PFRP standards but does not eliminate all nonpathogenic
microorganisms from the sludge.
None of the above references suggest that lime or kiln dust, in
combination with a natural drying process, could be used to produce
the pathogenic reducton in wastewater sludge equivalent to PFRP
processes, and thus provide an inexpensive method of treating
wastewater sludge such that it can be applied directly to land as a
fertilizer to grow crops for direct human consumption.
SUMMARY OF THE INVENTION
In accordance with the invention, lime, cement kiln dust or lime
kiln dust or mixtures thereof and/or other alkaline materials are
mixed with wastewater sludge in sufficient quantity to raise the pH
to 12 and above for at least two hours and the resulting mixture is
.Iadd.actively .Iaddend.dried by an aeration process. The process
produces a product wherein the pathogen viability has been reduced
to a level that meets or exceeds USEPA criteria for PFRP processes
.Iadd.without eliminating all of the beneficial non-pathogenic
microorganisms.Iaddend..
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 are curves of the percent solids of sludge versus days of
treatment.
FIG. 2 are curves of the pH of sludge versus days of treatment.
FIG. 3 are curves of the log number of fecal coliform per weight of
sludge versus days of treatment.
FIG. 4 are curves of the log number of fecal streptococci per
weight of sludge versus days of treatment.
FIG. 5 are curves of the log number of Salmonella enteritidis
typhimurium per weight of combined sludge versus days of
treatment.
FIG. 6 are curves of the log number of Salmonella enteritidis
typhimurium per weight of digested sludge versus days of
treatment.
FIG. 7 is a bar chart of the log number of enterovirus per weight
of sludge versus days of treatment.
FIG. 8 are curves of the number of viable Ascaris eggs per weight
of combined sludge versus weeks of treatment.
FIG. 9 are curves of the umber of digested sludge versus weeks of
treatment.
FIG. 10 is a bar chart of the relative sludge odor after two weeks
of treatment.
DESCRIPTION
Basically, the process of this invention comprises mechanically
dewatering the sludge; chemical stabilizing of the wastewater
sludge with quantities of lime, cement kiln dust or lime kiln dust
or mixtures thereof sufficient to maintain a pH of 12 and above for
at least two hours and preferably for days; and then .Iadd.actively
.Iaddend.drying the sludge by an aeration process such as a Brown
Bear aerating device. To achieve PFRP pathogen reduction criteria,
the treated sludge is .[.aerated.]. .Iadd.dried .Iaddend.such that
the sludge is at least eighty percent (80%) by weight solids and
preferably ninety percent (90%) by weight solids. The product is
allowed to air cure for about 10 days after .Iadd.the
.Iaddend.desired solids content is achieved. The drying and curing
of the mixture may also be accomplished by a windrow method,
turn-over-method, or other forced air methods. The curing time or
aeration time is dependent on the type of storage facility
(.[.cover.]. .Iadd.covered.Iaddend., enclosed, or open), aeration
procedure, mix design, physical and chemical properties of the
admixtures, quality of the mixing facilities, percent solids of
dewatering cake, and type of sludge. The chemical stabilizing
admixture can be added after mechanical dewatering, if desired.
Lime, cement kiln dust and lime kiln dust are excellent flocculents
and thus can be useful in conditioning prior to mechanical
dewatering with most equipment.
The range of lime, cement kiln dust or lime kiln dust mixed with
the sludge is about ten percent (10%) by weight to 200% by weight
of the dry sludge depending on the variables listed above.
The addition of high reactant-heat generating materials or heating
the sludge and materials may be used to reduce the total amount of
admixture required and/or .Iadd.to .Iaddend.reduce the .Iadd.drying
and/or .Iaddend.curing time required. Addition of anhydrous ammonia
and either phosphoric acid or sulphuric acid to chemical stabilized
sludge, having a pH of 12 and above, produces sufficient heat to
help reduce pathogens to a level equivalent to PFRP processes and
at the same time increases the nutritional value of the sludge
while reducing curing time and .[.natural.]. .Iadd.active
.Iaddend.drying requirements. In addition to chemical generated
heat, mechanical or electrical heat may be applied to dry and cure
the mixture.
The solid waste generated by cement manufacture is primarily kiln
dust. This dust contains a mixture of raw kiln feed, partly
calcined material, finely divided cement clinker and alkaline and
alkali carbonates and sulfates (usually sulfates). There is
economic value in returning the dust to the kiln, but when the
alkali content of the returned dust is too high for the product
clinker to meet specifications, the dust must be discarded. Up to
about 15% of the raw materials processed may be collected as dust
and of this about half may be low enough in alkalis to be returned
to the kiln. The rest usually stockpiled as a waste material which
usually is discarded and may be a nuisance and possibly a
hazard.
Typically, the major oxide found in a cement kiln dust are:
SiO.sub.2, A1.sub.2 O.sub.3, Fe.sub.2 O.sub.3, CaO, MgO, So.sub.3,
Na.sub.2 O and K.sub.2 O.
The solid waste generated by lime manufacture is primarily lime
stack dust. This dust contains a mixture of raw kiln feed, partly
calcined material, and finely divided material. There is no value
in returning the dust to the kiln, as it is too fine and passes
directly through to the precipitator again. Up to about 15% of the
raw materials processed may be collected as dust. It is usually
stockpiled as a waste material which usually is discarded and may
be a nuisance and possibly a hazard.
Typically, the major oxides found in line stack dust are: CaO, MgO,
SO.sub.3, CO.sub.2 and Availabe Free Lime.
A combination of materials may be used to provide the most
economical system such as using line, cement kiln dust or lime kiln
dust or mixtures thereof to achieve chemical stabilization, and
adding bulking material such as slag fines, fly ash, gypsum,
fluidized bed residue, dry sulphur scrubber residue, calcium
sulphate fines, and the like, to assist in dewatering. Lime, cement
kiln dust or lime kiln dust alone cannot achieve the desired
results of reducing pathogens to PFRP levels, but when used in
combination with a drying process, the decontamination can achieve
PFRP levels.
The process will drastically reduce the odor of the sludge, even
though the pH may drop below 9 during the curing period and the use
of admixtures as bulking agents reduces the volume of the sludge
for disposal or utilization.
In a test, the use of cement kiln dust (CKD) and lime to stabilize
and disinfect sludge from the Toledo municipal wastewater treatment
plant was studied.
Specifically, tests were conducted to determine whether the
processes embodying this invention met requirements to be
classified as a Process to Significantly Reduce Pathogens (PSRP)
and a Process to Further Reduce Pathogens (PFRP). As indicated
above, for PSRP classification, the fecal and total coliform
bacterial counts must be reduced by two logs and the animal virus
count must be reduced by one log. For PFRP classification, animal
viruses must be less than one (1) plaque forming unit (PFU) per 100
ml of sludge; pathogenic bacteria (Salmonella) must be less than
three (3) colony forming units (CFU) per 100 ml of sludge; and
parasites (helmonth eggs - Ascaris) must be less than one (1)
viable egg per 100 ml of sludge, wherein 100 ml of sludge is
equivalent to about five (5) gms of dry solids. (As indicated in
EPA Memorandum of November 6, 1985).
FIG. 1, comprises a curve of the percent solids of combined sludge
versus days of treatment, without any added materials, with
twenty-five percent (25%) by weight cement kiln dust (CKD), and
with ten percent (10%) by weight lime.
As illustrated by FIG. 1, the addition of either ten percent (10%)
by weight of lime or twenty-five percent (25%) by weight of cement
kiln dust (CKD) enhanced the drying rate of sludges, particularly
in the first four weeks of treatment. Combined sludge is a mixture
of primary sludge and secondary (waste activated) sludge.
FIG. 2, comprises a curve of pH of combined sludge versus days of
treatment, without any added materials, with twenty-five percent
(25%) by weight cement kiln dust (CKD), and with ten percent (10%)
by weight lime.
FIG. 2, shows that the pH of ten percent (10%) by weight lime
treated sludge did not decline appreciably during the study and
that twenty-five percent (25%) by weight cement kiln dust treated
sludge maintained a pH level of 12.4 for one (1) day before slowly
declining and reading control levels in about four weeks.
FIG. 3, comprises a curve of the log number of fecal coliform per
weight of combined sludge versus days of treatment, without any
added materials, with twenty-five percent (25%) by weight cement
kiln dust (CKD), and ten percent (10%) by weight lime.
FIG. 3, shows that fecal coliforms, one of the most common types of
indicator bacteria used for water quality assays, were unaffected
in untreated sludge regardless of the amount of drying. However,
the sludge treated with twenty-five percent (25%) by weight cement
kiln dust showed a rapid five (5) log reduction in coliforms in one
(1) day and dropped even further in one week to one (1) bacterium
per five (5) gms dry weight of sludge. The sludge treated with ten
percent (10%) be weight lime treated sludge experienced a six (6)
log reduction in coliforms in the first day. Some regrowth was
found in both lime and cement kiln dust treated sludge with the
final population measured at 500 bacteria/5 gm dry at sludge.
FIG. 4, comprises a curve of the log number of fecal streptococci
per weight of digested sludge versus days of treatment, without any
added materials, with twenty-five percent (25%) by weight cement
kiln dust (CKD), and ten percent (10%) by weight lime.
FIG. 4 illustrates that the fecal streptococci decreased in both
the lime and cement kiln dust treated samples by over two logs but
did not decline any further over the course of the study. The
significance of this observation is that the cement kiln dust and
lime did not possess an inherent toxicity sufficient to kill all
microorganisms and that the killing process selected out only
certain microbial populations such as Salmonella.
FIG. 5, comprises a curve of the log number of Salmonella
enteritidis typhimurium per weight of combined sludge verses days
of treatment, without any added materials, with twenty-five percent
(25%) by weight cement kiln dust, and ten percent (10%) by weight
lime.
FIG. 6, comprises a curve of the log number of Salmonella
enteritidis typhimurium per weight of digested sludge verses days
of treatment, without any added materials, with twenty-five percent
(25%) by weight cement kiln dust (CKD), and with ten percent (10%)
by weight lime.
The principal bacterial indicator used by EPA in the setting of
PFRP standards for agricultural use of sludge is the pathogen
Salmonella enteritidis typhimurium. FIGS. 5 and 6 show that
following an initial three to four (3-4) log decrease in one day,
the Salmonella in all samples regrew to over 1000 Salmonella/5 gm
dry weight sludge. Only after a combination of drying and pH
exposure for over four (4) weeks did the Salmonella die off to
levels associated with PFRP processes. The untreated or controlled
Salmonella samples did not decrease over the eighty (80) days.
FIG. 7 comprises a bar chart of the log number of enterovirus per
weight of combined sludge verses days of treatment, without any
added materials, with twenty-five percent (25%) by weight cement
kiln dust (CKD), and with ten percent (10%) by weight lime.
The enterovirus, Poliovirus type I, was measured for survival by
assaying for viable virus on tissue culture lawns of Vero cells.
The virus viability was decreased by cement kiln dust and lime
treatment to levels associated with PFRP processes in one day, i.e.
less than one viable virus per five (5) gm dry weight sludge as
illustrated in FIG. 7. Virus levels in the untreated sludge sample
decreased almost two (2) logs in one day and the entire population
died in one (1) week.
FIG. 8, comprises a curve of the number of viable Ascaris eggs per
weight of combined sludge versus weeks of treatment, without any
added materials, with twenty-five percent (25%) and thirty-five
percent (35%) by weight cement kiln dust (CKD), and with ten
percent (10%) by weight lime.
FIG. 9, comprises a curve of the number of viable Ascaris eggs per
weight of digested sludge versus weeks of treatment, without any
added materials, with twenty-five percent (25%) and thirty-five
percent (35%) by weight cement kiln dust (CKD), and with ten
percent (10%) by weight lime.
In other treatment processes for the stabilization of wastewater
sludge the viability of the helminth ova has been the major
difficulty encountered and certainly the most stringent of the EPA
parameters to meet. The initial level of Ascaris eggs added to the
sludge was 16000/5 gm dry weight sludge. Recovery following the
procedure for measuring viability of these eggs ranged from about
two percent (2%) in the digested sludge to about six percent (6%)
in the combined sludge. The viability of these recovered eggs is
shown in FIGS. 8 and 9 for combined and digested sludges
respectively. The viability of these eggs decreased to PFRP
required levels of one (1) viable eggs/5gm dry weight sludge in the
twenty-five percent (25%) and thirty-five percent (35%) by weight
cement kiln dust and in the ten percent (10%) by weight lime
treated combined and digested sludges only after six (6) weeks of
incubation.
The reduction of pathogens that occurred in the sludge as a result
of cement kiln dust or lime addition appears to be due to the
samples initially achieving a pH of 11.5 followed by a synergistic
interaction of elevated pH and drying. This proposition is
supported by the following facts: a) the samples without high pH
but with significant drying did not experience a significant
decline in microorganisms; b) the samples such as the twenty-five
percent (25%) by weight cement kiln dust treated combined sludge
exhibited an initial high pH but a subsequent lower pH plateau and
showed a killing of the Ascaris eggs continued at nearly
logarithmic rates; c) the longer the pH remained elevated above
9.5, as in the twenty-five percent (25%) by weight and thirty-five
percent (35%) by weight cement kiln dust samples, the better the
killing results with the Ascaris eggs; d) as shown in the curve for
the five percent (5%) by weight lime samples, higher pH by itself,
without elevated drying, showed a delay in the killing of the
Ascaris eggs.
FIG. 10, comprises a bar chart of the relative sludge odor after
two weeks for digested and combined sludge, without any added
materials, with fifteen percent (15%), twenty-five percent (25%),
and thirty-five percent (35%) by weight cement kiln dust, and with
five percent (5%) and ten percent (10%) by weight lime.
As illustrated by FIG. 10, the addition of cement kiln dust or lime
did have an effect on the odor of the sludge. However, while all
cement kiln dust and lime treatments improved the odor of the
sludge, only the thirty-five percent (35%) by weight cement kiln
dust treated sludge reduced the odor to a level that could be
considered tolerable in a closed room.
It was also determined that the addition of cement kiln dust or
lime to sludge had an effect on the material handling aspect of
such sludge. The thirty-five percent (35%) by weight cement kiln
dust treated sludge had an individual particle size averaging about
two to five (2-5) mm in diameter and thus rendered the treated
sludge easy to handle. In contrast, the lime treated and the
fifteen percent (15%) and twenty-five percent (25%) by weight
cement kiln dust treated samples all contained very large lumps
averaging about three to eight (3-8) cm in diameter and rendered
the treated sludge less easy to handle.
The following conclusions were reached regarding lime and kiln dust
treated sludge processes:
1. Sludge treated with cement kiln dust or lime in all cases tested
met PSRP classification requirements.
2. Cement kiln dust treated sludge enhanced the drying rate of
sludges particularly in the first four (4) weeks of treatment.
3. Cement kiln dust treated sludge loses its pH value more rapidly
than lime treated sludge.
4. Bacterial pathogens such as Salmonella are controlled to PFRP
levels by five (5) weeks when such sludges are treated with
twenty-five percent (25%) and thirty-five percent (35%) by weight
cement kiln dust or ten percent (10%) by weight lime.
5. Enterovirus levels were controlled to PFRP levels within one day
by both cement kiln dust and lime treated sludges.
6. Ascaris egg survival was reduced by more than three (3) logs by
higher dosage treatments within four (4) weeks. The twenty-five
percent (25%) CKD, thirty-five percent (35%) CKD and ten percent
(10%) by weight lime treated sludges have been shown to reach PFRP
(1 viable egg/5 gm dry wt sludge) levels by day forty-six (46). The
sample containing fifteen percent (15%) CKD in the combined sludge
did not reach PFRP standards, while the sample with fifteen percent
(15%) CKD in digested sludge did.
7. Both CKD and lime treatments reduce sludge odor. Only
thirty-five percent (35%) CKD by weight treatment reduced odor to
mild levels.
8. Drying was not sufficient by itself to kill microorganisms in
sludge.
9. Regrowth of pathogens (Salmonella) was effectively prevented
over the eighty (80) days of the study.
10. All EPA PFRP standards were reached after six (6) weeks of
incubation of the twenty-five percent (25%) CKD, the thirty-five
percent (35%) CKD and the ten percent (10%) lime by weight treated
sludges.
With regard to the three PFRP standards the following results were
achieved by six plus (6+) weeks (46 days):
STANDARD SLUDGE TREATMENT Salmonella Virus Ascaris All COMBINED
Control No No No No 15% CKD No -- No No 25% CKD Yes (35) Yes (1)
Yes (46) Yes 35% CKD Yes (27) -- Yes (46) Yes 5% Lime Yes (46) --
Yes (46) ? 10% Lime Yes (27) Yes (1) Yes (46) Yes DIGESTED Control
No No No No 15% CKD Yes (46) -- Yes (46) ? 25% CKD Yes (46) -- Yes
(46) Yes* 35% CKD Yes (27) -- Yes (46) Yes* 5% Lime No -- Yes (46)
No 10% Lime Yes (27) -- Yes (46) Yes* Key: No = PFRP not achieved
Yes = PFRP achieved (3) = day that achievement was detected ? =
results not completed *conclusion based upon data with combined
sludge
Tests were conducted on the following 12 treatment groups:
Combined Digested 1. Untreated 7. Untreated 2. 15% CKD 8. 15% CKD
3. 25% CKD 9. 25% CKD 4. 35% CKD 10. 35% CKD 5. 5% Lime 11. 5% Lime
6. 10% Lime 12. 10% Lime
Each of these treatment groups (5000g sludge plus treatment) was
contained in a 10 liter plastic tub. These were kept dry at 68F and
were mixed twice weekly to facilitate drying. Samples were removed
at 0, 1, 7, 13, 27, 46 and 80 days and processed to determine
pathogen and microorganism survival. The parameters that were
determined at each sampling are listed as follows: percent solids
pH volume fecal coliforms fecal streptocci Salmonella enteritidis
typhimurium Ascaris suum eggs Human enteric virus (Polio Type
I-vaccine strain)
The data from which the above referenced results and FIGS. 1-10
were compiled are summarized in the following tables.
TABLE I % Volume/ # FC/ # FS # Sal/ # Virus/ # V Ascaris Eggs Tub #
Treatment ph Solids 100 gS 5 g DWS* 5 g DWS 5 g DWS 5 g DWS 5 g DWS
1 combined CONTROL 6.8 92.7 76 1.7 .times. 10.sup.6 6.5 .times.
10.sup.5 7.5 .times. 10.sup.5 -- -- 2 15% CKD/COMB 8.3 94.8 -- 1.7
.times. 10.sup.5 3.4 .times. 10.sup.7 12.5 -- -- 3 25% CKD/COMB 8.9
95.2 57.2 5 .times. 10.sup.2 3.4 .times. 10.sup.5 0.4 -- -- 4 35%
CKD/COMB 9.3 93.3 -- 5 .times. 10.sup.2 2.8 .times. 10.sup.2 0.4 --
-- 5 5% LIME/COMB 8.4 91.2 -- 5.5 .times. 10.sup.2 3.5 .times.
10.sup.3 2.9 -- -- 6 10% LIME/COMB 11.7 92.2 74.0 5 .times.
10.sup.2 6.5 .times. 10.sup.0 2.9 -- -- 7 DIGEST CONTROL 6.3 92.4
74.0 4.7 .times. 10.sup.6 2.4 .times. 10.sup.5 3.5 .times. 10.sup.6
-- -- 8 15% CKD/DIG 8.4 93.9 6.5 .times. 10.sup.3 1.1 .times.
10.sup.5 0.4 -- -- 9 25% CKD/DIG 9.2 93.6 56.0 5 .times. 10.sup.2
6.5 .times. 10.sup.2 0.4 -- -- 10 35% CKD/DIG 9.6 92.4 5 .times.
10.sup.2 2.4 .times. 10.sup.1 0.4 -- -- 11 5% LIME/DIG 8.6 92.4 2.8
.times. 10.sup.2 4.8 .times. 10.sup.1 0.4 -- -- 12 10% LIME/DIG
12.0 92.5 72.0 4.9 6.5 .times. 10.sup.1 0.4 -- -- Dry weight
sludge; FC = Fecal coliforms; FS = Fecal streptococci; Sal =
Salmonella enteritidis typhimurium; # V Ascaris eggs = Viable
Ascaris suum eggs; # Virus = Viable enterovirus; COMBINED CONTROL =
Untreated combined sludge; CKD/COMB = Combined sludge treated with
cement kiln dust; LIME/COMB = combined sludge treated with Lime;
DIGEST CONTROL = Untreated digested sludge; CKD/DIG = digested
sludge treated with cement kiln dust, LIME/DIG = Digested sludge
treated with lime. Elapsed Time 80 days
TABLE II % Volume/ # FC/ # FS # Sal/ # Virus/ # V Ascaris Eggs Tub
# Treatment ph Solids 100 gS 5 g DWS* 5 g DWS 5 g DWS 5 g DWS 5 g
DWS 1 COMBINED CONTROL 7.3 92.3 76.0 1.9 .times. 10.sup.6 2.8
.times. 10.sup.8 6.5 .times. 10.sup.4 -- 80.8 2 15% CKD/COMB 8.4
94.7 1.0 .times. 10.sup.4 1.5 .times. 10.sup.7 4.9 .times. 10.sup.1
-- 2.8 3 25% CKD/COMB 8.4 94.2 68.0 4.9 .times. 10.sup.0 2.6
.times. 10.sup.4 .4 -- 0 4 35% CKD/COMB 10.1 91.9 0.4 6.5 .times.
10.sup.1 .4 -- 0 5 5% LIME/COMB 8.1 93.1 3.5 .times. 10.sup.2 6.5
.times. 10.sup.4 .4 -- 0 6 10% LIME/COMB 12.5 89.7 82.0 6.7 1.1
.times. 10.sup.3 .4 -- 0 7 DIGESTED CONTROL 6.5 93.6 76.0 3.4
.times. 10.sup.7 6.5 .times. 10.sup.4 5.5 .times. 10.sup.4 -- 37 8
15% CKD/DIG 8.4 93.9 1.0 .times. 10.sup.5 5 .times. 10.sup.5 .4 --
0.3 9 25% CKD/DIG 8.2 95.2 62.0 4.9 1.1 .times. 10.sup.4 .4 -- 0 10
35% CKD/DIG 10.3 92.5 4.9 2.4 .times. 10.sup.2 .4 -- 0 11 5%
LIME/DIG 8.1 92.9 3.5 .times. 10.sup.2 3.7 .times. 10.sup.3 3.65 --
0 12 10% LIME/DIG 12.7 92.4 88.0 4.9 3.7 .times. 10.sup.3 .4 -- 0
Dry weight sludge; FC = Fecal coliforms; FS = Fecal streptococci;
Sal = Salmonella enteritidis typhimurium; # V Ascaris eggs = Viable
Ascaris suum eggs; # Virus = Viable enterovirus; COMBINED CONTROL =
Untreated combined sludge; CKD/COMB = Combined sludge treated with
cement kiln dust; LIME/COMB = combined sludge treated with Lime;
DIGEST CONTROL = Untreated digested sludge; CKD/DIG = digested
sludge treated with cement kiln dust, LIME/DIG = Digested sludge
treated with lime. Elapsed Time 46 days
TABLE III % Volume/ .# FC/ # FS # Sal/ # Virus/ # V Ascaris Eggs
Tub # Treatment ph Solids 100 gS 5 g DWS* 5 g DWS 5 g DWS 5 g DWS 5
g DWS 1 COMBINED CONTROL 3 25% CKD/COMB <0.5 4 5 5% LIME/COMB
3.2 6 7 8 9 10 11 5% LIME/DIG <0.5 12 Dry weight sludge; FC =
Fecal coliforms; FS = Fecal streptococci; Sal = Salmonella
enteritidis typhimurium; # V Ascaris eggs = Viable Ascaris suum
eggs; # Virus = Viable enterovirus; COMBINED CONTROL = Untreated
combined sludge; CKD/COMB = Combined sludge treated with cement
kiln dust; LIME/COMB = combined sludge treated with Lime; DIGEST
CONTROL = Untreated digested sludge; CKD/DIG = digested sludge
treated with cement kiln dust, LIME/DIG = Digested sludge treated
with lime. Elapsed Time 35 days
TABLE IV % Volume/ # FC/ # FS # Sal/ # Virus/ # V Ascaris Eggs Tub
# Treatment ph Solids 100 gS 5 g DWS* 5 g DWS 5 g DWS 5 g DWS .5 g
DWS 1 COMBINED CONTROL 8.28 50.6 82.0 2.8 .times. 10.sup.6 6.5
.times. 10.sup.8 6.5 .times. 10.sup.6 -- 332 2 15% CKD/COMB 8.2
94.4 -- 1.9 .times. 10.sup.6 3.4 .times. 10.sup.6 5 .times.
10.sup.1 -- 8.5 3 25% CKD/COMB 8.6 91.7 71.2 3.7 .times. 10.sup.9
1.1 .times. 10.sup.6 8.5 .times. 10.sup.2 -- 5.8 4 35% CKD/COMB
10.2 83.4 -- 1.2 .times. 10.sup.1 1.9 .times. 10.sup.3 <.5 --
1.9 5 5% LIME/COMB 8.12 88.9 -- 2.0 .times. 10.sup.2 4.9 .times.
10.sup.4 2.7 .times. 10.sup.3 -- 12.0 6 10% LIME/COMB 12.4 82.0
79.2 1.0 3.9 .times. 10.sup.3 <.5 -- 6.5 7 DIGEST CONTROL 6.8
72.2 84.0 4.5 .times. 10.sup.6 4.5 .times. 10.sup.8 9.5 .times.
10.sup.6 -- 156.6 8 15% CKD/DIG 8.4 94.9 -- 4.7 .times. 10.sup.3
4.9 .times. 10.sup.2 1.1 .times. 10.sup.2 -- 19.7 9 25% CKD/DIG 8.4
92.9 68.0 4.8 1.1 .times. 10.sup.4 4.3 -- 8.6 10 35% CKD/DIG 10.4
82.1 -- 3.2 2.2 .times. 10.sup.3 <0.5 -- 0.8 11 5% LIME/DIG 8.2
83.5 -- 4.1 1.2 .times. 10.sup.4 5.5 .times. 10.sup.2 -- 0.8 12 10%
LIME/DIG 12.4 80.1 74.0 <.5 2.8 .times. 10.sup.3 <0.5 -- 1.7
Dry weight sludge; FC = Fecal coliforms; FS = Fecal streptococci;
Sal = Salmonella enteritidis typhimurium; # V Ascaris eggs = Viable
Ascaris suum eggs; # Virus = Viable enterovirus; COMBINED CONTROL =
Untreated combined sludge; CKD/COMB = Combined sludge treated with
cement kiln dust; LIME/COMB = combined sludge treated with Lime;
DIGEST CONTROL = Untreated digested sludge; CKD/DIG = digested
sludge treated with cement kiln dust, LIME/DIG = Digested sludge
treated with lime. Elapsed Time 27 days
TABLE V % Volume/ # FC/ # FS # Sal/ # Virus/ # V Ascaris Eggs Tub #
Treatment ph Solids 100 gS 5 g DWS* 5 g DWS 5 g DWS 5 g DWS .5 g
DWS 1 COMBINED CONTROL 8.9 41.6 86.4 2.4 .times. 10.sup.7 4.4
.times. 10.sup.8 >7.5 .times. 10.sup.6 -- 378 2 15% CKD/COMB 8.3
74.7 -- 6.0 .times. 10.sup.6 1.4 .times. 10.sup.8 >4.3 .times.
10.sup.5 -- 74.9 3 25% CKD/COMB 10.0 75.1 68.8 3.5 .times. 10.sup.1
1.4 .times. 10.sup.5 >4.3 .times. 10.sup.4 -- 35.5 4 35%
CKD/COMB 11.5 70.4 -- 3.2 .times. 10.sup.2 2.6 .times. 10.sup.2
>7.0 .times. 10.sup.2 -- 9.4 5 5% LIME/COMB 12.4 50.8 -- 3.2
.times. 10.sup.4 6.5 .times. 10.sup.4 >9.5 .times. 10.sup.2 --
55.7 6 10% LIME/COMB 12.4 52.7 84 0.8 6.0 .times. 10.sup.3 >9.0
.times. 10.sup.2 -- 20.3 7 DIGEST CONTROL 8.9 34.9 84 7 .times.
10.sup.7 4.6 .times. 10.sup.7 >1.2 .times. 10.sup.6 -- 351.9 8
15% CKD/DIG 8.9 80.4 -- 2 .times. 10.sup.3 4.0 .times. 10.sup.5
>8.5 .times. 10.sup.4 -- 63.0 9 25% CKD/DIG 9.9 76.1 67.2 0.6
4.2 .times. 10.sup.4 >1.1 .times. 10.sup.3 -- 17.6 10 35%
CKD/DIG 12.3 72.8 -- 4.7 2.5 .times. 10.sup.3 >1.1 .times.
10.sup.3 -- 9.2 11 5% LIME/DIG 12.4 59.3 -- 8 1.2 .times. 10.sup.4
>2.0 .times. 10.sup.2 -- 80.7 12 10% CIME/DIG 12.4 59.5 80.8 8
5.5 .times. 10.sup.3 >2.0 .times. 10.sup.2 -- 15.7 Dry weight
sludge; FC = Fecal coliforms; FS = Fecal streptococci; Sal =
Salmonella enteritidis typhimurium; # V Ascaris eggs = Viable
Ascaris suum eggs; # Virus = Viable enterovirus; COMBINED CONTROL =
Untreated combined sludge; CKD/COMB = Combined sludge treated with
cement kiln dust; LIME/COMB = combined sludge treated with Lime;
DIGEST CONTROL = Untreated digested sludge; CKD/DIG = digested
sludge treated with cement kiln dust, LIME/DIG = Digested sludge
treated with lime. Elapsed Time 13 days
TABLE VI % Volume/ # FC/ # FS # Sal/ # Virus/ # V Ascaris Eggs Tub
# Treatment ph Solids 100 gS 5 g DWS* 5 g DWS 5 g DWS 5 g DWS .5 g
DWS 1 COMBINED CONTROL 8.8 29.9 88.0 5.5 .times. 10.sup.7 1.3
.times. 10.sup.8 1.3 .times. 10.sup.6 0 445.6 2 15% CKD/COMB 10.0
51.0 9.5 .times. 10.sup.5 2.8 .times. 10.sup.7 5.0 .times. 10.sup.4
-- 201.4 3 25% CKD/COMB 11.3 54.4 70.0 0.6 5.0 .times. 10.sup.3 7.5
.times. 10.sup.2 0 107.8 4 35% CKD/COMB 12.5 65.8 0.5 7.5 .times.
10.sup.2 3.3 .times. 10.sup.1 -- 27.8 5 5% LIME/COMB 12.3 46.8 0.7
8.5 .times. 10.sup.2 0.7 -- 96.3 6 10% LIME/COMB 12.3 46.2 76.8 0.7
8.0 .times. 10.sup.0 0.7 0 57.7 7 DIGEST CONTROL 8.6 36.1 87.2 4.1
.times. 10.sup.7 2.3 .times. 10.sup.6 1.1 .times. 10.sup.6 -- 243.7
8 15% CKD/DIG 10.2 49.7 6.5 .times. 10.sup.1 1.0 .times. 10.sup.4
>5.5 .times. 10.sup.2 -- 155.7 9 25% CKD/DIG 11.2 51.9 70.0 1.3
.times. 10.sup.0 7.5 .times. 10.sup.2 7.5 .times. 10.sup.1 -- 16.2
10 35% CKD/DIG 11.7 61.7 0.5 4.3 .times. 10.sup.2 6.0 .times.
10.sup.1 -- -- 11 5% LIME/DIG 12.3 42.8 0.8 6.0 .times. 10.sup.2
9.0 .times. 10.sup.1 -- 130.5 12 10% LIME/DIG 12.4 42.8 76.0 0.8
5.0 .times. 10.sup.2 9.0 .times. 10.sup.1 -- 105.6 Dry weight
sludge; FC = Fecal coliforms; FS = Fecal streptococci; Sal =
Salmonella enteritidis typhimurium; # V Ascaris eggs = Viable
Ascaris suum eggs; # Virus = Viable enterovirus; COMBINED CONTROL =
Untreated combined sludge; CKD/COMB = Combined sludge treated with
cement kiln dust; LIME/COMB = combined sludge treated with Lime;
DIGEST CONTROL = Untreated digested sludge; CKD/DIG = digested
sludge treated with cement kiln dust, LIME/DIG = Digested sludge
treated with lime. Elapsed Time 7 days
TABLE VII % Volume/ # FC/ # FS # Sal/ # Virus/ # V Ascaris Eggs Tub
# Treatment ph Solids 100 gS 5 g DWS* 5 g DWS 5 g DWS 5 g DWS .5 g
DWS 1 COMBINED CONTROL 7.3 31.61 78.0 6.5 .times. 10.sup.8 1.3
.times. 10.sup.7 4.0 .times. 10.sup.5 3.3 .times. 10.sup.4 520.5 2
15% CKD/COMB 11.7 44.9 3.4 .times. 10.sup.6 9.0 .times. 10.sup.6
8.0 .times. 10.sup.4 -- 130.5 3 25% CKD/COMB 12.7 51.3 80.0 1.2
.times. 10.sup.2 1.5 .times. 10.sup.2 7.0 .times. 10.sup.1 0 99.6 4
35% CKD/COMB 12.9 59.2 5.5 .times. 10.sup.2 1.7 .times. 10.sup.3
6.0 .times. 10.sup.2 -- 448.5 5 5% LIME/COMB 12.4 36.7 2.1 .times.
10.sup.1 1.1 .times. 10.sup.4 <1.2 -- 54.4 6 10% LIME/COMB 12.4
43.7 84.0 4.5 .times. 10.sup.0 1.7 .times. 10.sup.2 <1.2 0 61.0
7 DIGEST CONTROL 7.6 34.8 90.0 2.2 .times. 10.sup.7 2.2 .times.
10.sup.6 6.5 .times. 10.sup.4 -- 99.3 8 15% CKD/DIG 11.7 44.4 2.8
.times. 10.sup.2 1.4 .times. 10.sup.4 1.3 .times. 10.sup.1 -- -- 9
25% CKD/DIG 12.5 55.1 74.0 1.1 .times. 10.sup.2 1.4 .times.
10.sup.3 <0.9 -- 43.6 10 35% CKD/DIG 13.0 60.5 1.0 .times.
10.sup.1 2.7 .times. 10.sup.3 <0.9 -- 42.9 11 5% LIME/DIG 12.2
38.2 1.6 .times. 10.sup.1 2.0 .times. 10.sup.3 <1.3 -- -- 12 10%
LIME/DIG 12.4 46.1 82.0 1.3 .times. 10.sup.1 1.3 .times. 10.sup.3
<1.1 -- 58.6 Dry weight sludge; FC = Fecal coliforms; FS = Fecal
streptococci; Sal = Salmonella enteritidis typhimurium; # V Ascaris
eggs = Viable Ascaris suum eggs; # Virus = Viable enterovirus;
COMBINED CONTROL = Untreated combined sludge; CKD/COMB = Combined
sludge treated with cement kiln dust; LIME/COMB = combined sludge
treated with Lime; DIGEST CONTROL = Untreated digested sludge;
CKD/DIG = digested sludge treated with cement kiln dust, LIME/DIG =
Digested sludge treated with lime. Elapsed Time 1 day
TABLE VIII % Volume/ # FC/ # FS # Sal/ # Virus/ # V Ascaris Eggs
Tub # Treatment ph Solids 100 gS 5 g DWS* 5 g DWS 5 g DWS 5 g DWS
.5 g DWS 1 COMBINED CONTROL 8.28 50.6 82.0 2.8 .times. 10.sup.6 6.5
.times. 10.sup.8 6.5 .times. 10.sup.6 -- 332 1 COMBINED CONTROL 5.9
30.9 92.0 ml 9.7 .times. 10.sup.6 7.8 .times. 10.sup.5 1.5 .times.
10.sup.4 2.0 .times. 10.sup.6 n = 582.4 2 15% CKD/COMB 11.5 33.2 --
9.7 .times. 10.sup.6 7.8 .times. 10.sup.5 1.5 .times. 10.sup.4 --
-- 3 25% CKD/COMB 12.5 42.9 76.0 ml 9.7 .times. 10.sup.6 7.8
.times. 10.sup.5 1.5 .times. 10.sup.4 -- -- 4 35% CKD/COMB 12.8
45.3 -- 9.7 .times. 10.sup.6 7.8 .times. 10.sup.5 1.5 .times.
10.sup.4 -- -- 5 5% LIME/COMB 12.3 49.4 -- 9.7 .times. 10.sup.6 7.8
.times. 10.sup.5 1.5 .times. 10.sup.4 -- -- 6 10% LIME/COMB 12.4
49.4 74.0 ml 9.7 .times. 10.sup.6 7.8 .times. 10.sup.5 1.5 .times.
10.sup.4 -- -- 7 DIGEST CONTROL 7.0 34.6 88.0 ml 1.8 .times.
10.sup.7 4.1 .times. 10.sup.5 5.2 .times. 10.sup.4 -- -- 8 15%
CKD/DIG 11.7 35.5 -- 1.8 .times. 10.sup.7 4.1 .times. 10.sup.5 5.2
.times. 10.sup.4 -- -- 9 25% CKD/DIG 12.4 37.0 -- 1.8 .times.
10.sup.7 4.1 .times. 10.sup.5 5.2 .times. 10.sup.4 -- -- 10 35%
CKD/DIG 12.7 39.1 -- 1.8 .times. 10.sup.7 4.1 .times. 10.sup.5 5.2
.times. 10.sup.4 -- -- 11 5% LIME/DIG 12.4 40.2 -- 1.8 .times.
10.sup.7 4.1 .times. 10.sup.5 5.2 .times. 10.sup.4 -- -- 12 10%
LIME/DIG 12.4 46.9 -- 1.8 .times. 10.sup.7 4.1 .times. 10.sup.5 5.2
.times. 10.sup.4 -- -- Dry weight sludge; FC = Fecal coliforms; FS
= Fecal streptococci; Sal = Salmonella enteritidis typhimurium; # V
Ascaris eggs = Viable Ascaris suum eggs; # Virus = Viable
enterovirus; COMBINED CONTROL = Untreated combined sludge; CKD/COMB
= Combined sludge treated with cement kiln dust; LIME/COMB =
combined sludge treated with Lime; DIGEST CONTROL = Untreated
digested sludge; CKD/DIG = digested sludge treated with cement kiln
dust, LIME/DIG = Digested sludge treated with lime. Elapsed Time 0
days
The above results are disclosed and claimed in U.S. patent
application Ser. No. 019,888, filed Feb. 27, 1987, having a common
assignee with the present invention.
In accordance with the present invention, it has been found that
the method can be optimized to achieve optimum results. In
accordance with the present invention, the method comprises
advanced alkaline stabilization with subsequent accelerated
drying.
Definitions:
1. Alkaline Materials. Cement kiln dust (CKD), lime kiln dust
(LKD), quicklime fines, pulverized lime, or hydrated lime in the
preferred forms disclosed in Appendix A. Alternative alkaline
materials may be substituted in whole or in part if they meet
performance criteria shown below. 2. Advanced Alkaline
Stabilization with Subsequent Accelerated Drying.
Alternative #1: Sufficient addition of the alkaline materials
described above to produce the following specifications: The amount
of alkaline materials added is sufficient to achieve a pH of
greater than 12 and to hold the pH of greater than 12 for at least
seven (7) days. Thorough mixing sufficient to achieve hydrolysis
within the sludge cake is required. The advanced alkaline
stabilized sludge is then dried, for example, as by aeration, for
at least 30 days and until a minimum solids concentration of 65%
solids is reached. The amount of alkaline materials is sufficient
that the sludge solids will achieve at least 60% solids by weight
before the pH drops below 12.0.
Alternative #2: Sufficient addition of alkaline materials plus
predetermined heat described above to produce the following
specifications: The amount of alkaline materials added is
sufficient to achieve a pH of greater than 12 and to hold a pH of
greater than 12 for at least 72 hours. Thorough mixing sufficient
to achieve hydrolysis with the sludge cake is required. Concurrent
with this high pH, the sludge is heated to a temperature of at
least about 50.degree. C., but not a temperature sufficient to
cause sterilization. Sufficient heat is added so that the sludge
when stored in a static condition will be maintained at a
temperature of at least 50.degree. C. for at least 12 hours. The
temperature increase may be obtained using exothermic reactions
from the alkaline materials or from other thermal processes.
Stabilized sludge is then dried by aeration until a minimum solids
concentration of 50% solids is achieved.
When mixed or blended with sludge, the fine alkaline materials
described above not only provide uniform intimate contact with
sludge to maintain an unfavorable biochemical environment but also
have large specific surface area which can provide sorptive odor
control and accelerated drying rates. The process will reduce
vector attraction and reduce pathogens to below detectable limits.
Specifically, the process, advanced alkaline stabilization with
subsequent accelerated drying, will achieve a maximum of
approximately 1 PFU (plaque forming unit) of animal viruses per 100
ml of sludge, 3 CFR (colony forming units) of pathogenic bacteria
(salmonella) per 100 ml of sludge when sludge is equivalent to
approximately 5 grams of dry solids per 100 ml.
The fine CKD, LKD, lime materials (as described in Appendix A) are
uniformly mixed into either liquid sewage sludge or dewatered
sewage sludge cake. Uniform and thorough additions are achieved
utilizing either mechanical or aeration mixing (wet sludges), or
mechanical mixing (dewatered sludges) to produce advanced alkaline
stabilized treated sludge. If the resulting sludge is in cake form,
the .[.air.]. .Iadd.active .Iaddend.drying process described below
is directly initiated. However, if the resulting sludge is in
liquid form, it is dewatered while pH still exceeds 12 utilizing
convention thickening/filtering process technology to an
intermediate solids level to produce a .[.handlable.].
.Iadd.handleable .Iaddend.cake material (appoximately 15-50%
solids). The alkaline materials are added in sufficient quantity to
ensure elevation of pH greater than 12 and mixing should be
sufficiently thorough as to cause hydrolysis of the sludge.
Alternative #1: The advanced alkaline stabilized dewatered sludge
cake is then .[.air.]. .Iadd.actively .Iaddend.dried (while pH
remains above 12 for at least seven days) through intermittent
turning of windrows or other .Iadd.active .Iaddend.drying processes
at least thirty (30) days and until the solids level reach and
maintain a minimum of 65% solids. The amount of alkaline materials
is sufficient to maintain the pH above 12 until the solids level
exceeds 60%. Alternative #2: The advanced alkaline stabilized
dewatered sludge cake is heated while the pH exceeds 12 using
exothermic reactions from the alkaline materials or other thermal
processes to achieve a temperature of at least about 50.degree. C.
throughout the sludge; but not at a temperature sufficient to cause
sterilization, and stored in static condition in such a manner as
to maintain said temperature for at least 12 hours. The
heat-treated advanced alkaline stabilized dewatered sludge cake is
then .[.air.]. .Iadd.actively .Iaddend.dried (while pH remains
above 12 for at least three days) through intermittent turning of
windrows or other .Iadd.active .Iaddend.drying processes until the
solids level reach and maintain a minimum of 50% solids.
The PFRP product resulting from the process as specified and
described above can be ultimately utilized through
marketing/distribution channels, land application programs,or as a
landfill cover material.
Experiments have been conducted as follows:
Experiment 1.
In this experiment, 5000 g samples of Toledo sludge were mixed with
15%, 25% or 35% cement kiln dust or 5% or 10% lime. The mixture was
kept at 72.degree. F. at approximately 20% humidity for over 60
days. The results showed that drying of the sludge was improved
with the CKD and that PFRP criteria were met for each microbial
standard with the 25% and 35% CKD and for the 10% lime. The pH of
the sludge/CKD mixture stayed above 12 for three days. The odor
control on the sludge treated with 35% CKD was better than any
other treatment and was quite satisfactory. The microbial results
can be summarized as follows: (Numbers represent viable counts per
5 gm of dry weight of sludge.) (No regrowth of pathogens occurred
after the days listed.)
Salmonella typhimurium Fecal coliforms 0 days = 1.5 .times. 10 0
days = 9.7 .times. 10 28 days = <1 13 days = 3.2 .times. 10
Poliovirus Fecal streptococci 0 days = 2.0 .times. 10 0 days = 7.8
.times. 10 .sup. 1 day = <1 13 days = 2.6 .times. 10 7 days =
<1 46 days = 6.5 .times. 10 Ascaris suum eggs 0 days = 42 days =
<1
Experiment 2.
This experiment compared lab and field treatments of Monroe,
Michigan, sludge with 35% CKD. The field windrows were arranged 3
sets of 10 units of 7 tons each. The microbiology was conducted on
the middle set of windrows that received mixing with a "Brown Bear"
twice a week. The mean temperature was about 45.degree. F. and the
humidity showed a mean of about 65%. Drying in the field was very
poor with solids reaching 54% at 28 days and 72% only after 64
days. The pH of the windrows remained above 12 for over 28 days. At
64 days the pH had fallen to 10.6. The odor control was very good
immediately following the CKD addition. The microbiology can be
summarized as follows:
Salmonella typhimurium Fecal coliforms 0 days = 104 0 days = 8.9
.times. 10 28 days = <0.3 .sup. 1 day = 7.9 .times. 10
Poliovirus 7 days = <0.3 0 days = 0 Fecal streptococci 1 day = 0
0 days = 2.4 .times. 10 Ascaris suum eggs .sup. 1 day = 2.1 .times.
10 0 days = <1 14 days = 2.8 .times. 10 .sup. 1 day = <1 7
days = <1
Experiment 3.
Sludges from three cities were separately tested as described
below.
a. Des Moines, Iowa
Municipal sludge was mixed with 30% CKD. Drying at 7 days reached
65% solids while the pH remained above 12. Odor control with the
CKD was excellent. The microbiology can be summarized as
follows:
Salmonella typhimurium Fecal coliforms 0 days = <2 0 days = 2.4
.times. 10 7 days = <2 7 days = 2 Poliovirus Fecal streptococci
0 days = ND 0 days = 2.4 .times. 10 7 days = ND 7 days = 2.3
.times. 10 Ascaris suum eggs 0 days = 2.4 7 days = <1
b. Dupage County, Ill.
Municipal sludge was mixed with lime kiln dust at 35%. Drying was
good reaching 63% in 2 weeks and 85% in 5 weeks. The pH had fallen
to 9.0 at 2 weeks and 7.2 at 5 weeks. The odor control was good at
2 weeks and excellent at 5 weeks. The microbiology can be
summarized as follows:
Salmonella typhimurium Fecal coliforms 0 days = ND 0 days = 2.3
.times. 10 14 days = ND 14 days = 2 35 days = ND 35 days = 22
Poliovirus Fecal streptococci ND ND Ascaris suum eggs ND
c. Toledo sludge treated at Sylvania Township, Ohio
Approximately 550 tons of Toledo's municipal sludge was treated
with 6% lime fines at the treatment plant following which it was
trucked to the Sylvania site where it was mixed with 35% CKD and
mixed in windrows (8' wide, 3.5' high, 200' long) on a 3 times a
week basis with a "Brown Bear". The weather conditions were wet and
summer temperatures averaged about 80.degree. F. The drying was
good reaching 64% solids in 30 days and 69% in 60 days. The pH
remained above 12 for over 60 days and only fell to 11.2 at 90
days. The odor control was good initially and very good after 30
days. The microbiology can be summarized as follows:
Salmonella typhimurium Fecal coliforms 0 days = 1.4 .times. 10 0
days = 1.1 .times. 10 30 days = <2 30 days = 2 60 days = <2
60 days = <2 Poliovirus Fecal streptococci ND 0 days = 3.0
.times. 10 Ascaris suum eggs 30 days = <2 0 days = 20 60 days =
20 30 days = <1 60 days = <1
Experiment 4.
Municipal sludge from Toledo was brought to the Medical College for
mixing (25000 g per cooler) with "bag house" quicklime and/or CKD
in the following percentages: 1. Control 0%; 2. 35% CKD 3. 6% lime
+35% CKD; 4. 10% lime +35% CKD 5. surface application of 35% CKD 6.
20% lime
The purpose of using these combinations was to measure temperatures
achieved and determine if incubation times could be shortened in
order for treated sludges to reach PFRP standards. Maximum
temperatures recorded were as follows for each of the above: 1
(25.degree. C.); 2 (38.degree. C.); 3 (46.degree. C.); 4
(58.degree. C.); 5 (25.degree. C.); and 6(87.degree. C.). The
maximal temperatures of the limed samples could have been higher
given optimal mixing conditions since additional mixings soon after
lime additions reduced temperatures. Drying was good reaching 52%
in the CKD only treated samples in 14 days and exceeding 64% in all
others. The pH remained above 12 for 24 hours in the CKD (#2)
sample and remained above 12 for over 56 days in all others. Odor
control was good in all treated samples. The microbiology can be
summarized as follows:
Salmonella typhimurium Fecal coliforms 0 days = 2.4 .times. 10 0
days = 4.8 .times. 10 3 days 3 days # 2 = 3.5 .times. 10 # 2 = 1.3
.times. 10 # 3 = <1 # 3 = <1 # 4 = <1 # 4 = <1 # 6 =
<1 # 6 = <1 Poliovirus Fecal streptococci ND 0 days = 8.7
.times. 10 3 days # 2 = 3.0 .times. 10 # 3 = 2.3 .times. 10 # 4 =
3.0 .times. 10 # 6 = <1 Ascaris suum eggs 0 days = 145 1 day 7
days 28 days # 1 = 64 # 1 = 88 # 1 = 152 # 2 = 19 # 2 = 13 # 2 =
<1 # 3 = <1 # 3 = <1 # 3 = < 1 # 4 = <1 # 4 = <1
# 4 = <1 # 6 = <1 # 6 = <1 # 6 = <1
Experiment 5.
In this experiment, 6% or 8% "bag house" quicklime was added to
Toledo municipal sludge at the treatment plant and then this
mixture was incubated in storage bins for a minimum of 12 hours.
Temperatures did not drop below 52.degree. C. with the 6% lime or
56.degree. C. with the 8% lime over the 12 hours. After this
incubation, the limed sludge (approximately 50 tons) was trucked to
the Toledo Port Authority site for mixing with 35% CKD and then
mixed twice weekly with the "Brown Bear". The drying was good
reaching 58% in 14 days and 60% in 28 days with the 6% lime treated
mixture and 54% in 14 days and 63% in 28 days with the 8% lime
treatment mixture. The pH of the 6% lime treated mixture was over
12 for 66 days and in the 8% lime mixture it was over 12 for the 28
days of the test. Odor control once the 35% CKD was mixed in was
very good. In order to adequately test the killing power of the
two-stage lime/CKD process, a cloth bag containing sludge and the
correct treatment mixture (8% lime followed by 35% CKD) was seeded
with Ascaris eggs and inserted directly into the incubation bin and
subsequent windrow. The microbiology can be summarized as
follows:
Salmonella typhimurium Fecal coliforms 6% L + 35% CKD 6% L + 35%
CKD 0 days = <1 0 days = 2.8 .times. 10 1.sup. day = <1
1.sup. day = <1 14 days = <1 14 days = <1 8% L + 35% CKD
8% L + 35% CKD 0 days = <1 0 days = 2.8 .times. 10 1.sup. day =
<1 1.sup. day = <1 Poliovirus Fecal streptococci ND 6% L +
35% CKD Ascaris suum eggs 0 days = 8.9 .times. 10 6% + 35% CKD
1.sup. day = <1 days = 2 14 days = <1 1 day = <1 8% + 35%
CKD 14 days = <1 0 days = 2.8 .times. 10 8% L = 35% CKD 1.sup.
day = <1 0 days - 137 (seeded) 14 days = <1 1.sup. day =
<1 14 days = <1
The above results shows conclusively that the treatment process
using CKD or lime/CKD in a two-stage process both cause the treated
municipal sludges to meet the PFRP criteria. The specific treatment
determines the processing time necessary for the sludge (when
seeded with 1.times.10 Salmonella and 1.times.10 Ascaris eggs) to
reach PFRP levels. The process and process times are as follows: 1.
CKD only - always within 46 days 2. 6% lime +35% CKD, no heat - 30
days 3. 6% lime +35% CKD, with 46.degree. C./12 hrs - 3 days 4. 6%
or 8% lime +35% CKD with 52.degree. C./12 hrs - 1 day
Further tests have shown that the method results in a stabilization
of heavy metals.
APPENDIX A
Material Specifications
Quick Lime:
Shall meet specifications for quicklime as identified in ASTM C
911. At least 75% of the material shall pass a #100 sieve.
Hydrated Lime:
Shall meet specifications for hydrated lime as identified in ASTM C
911. At least 75% of the material shall pass a #200 sieve.
Kiln Dust:
Material collected in a rotary kiln producing portland cement or
quicklime in accordance with ASTM C 150 and ASTM C 911,
respectively.
In an oxide analysis the material must contain at least a total of
35% CAo and Mgo. The loss on ignition shall not exceed 30%.
Reactive alkalines and alkalis (CAo +Mgo - [LOI.times.1.2]+K2o
+Na2o) shall exceed 12%. Maximum allowable levels of trace
elements: cadmium (Cd): 25 mg/kg copper (Cu): 500 mg/kg lead (Pb)
900 mg/kg nickel (Ni) 100 mg/kg mercury (Hg) 5 mg/kg zinc (ZN) 1500
mg/kg
At least 75% of the material shall pass the #100 sieve.
At least 50% of the material shall pass the #200 sieve.
* * * * *