DEMONSTRATING LEACHATE TREATMENT
REPORT ON A FULL-SCALE OPERATING PLANT
This report (SW-758) was written
by R. L. Steiner, J. D. Keenan, and A. A. Fungaroli,
and is reproduced as received from the grantee.
U.S. ENVIRONMENTAL PROTECTION AGENCY
1979
-------
This project was conducted at the GROWS (Geological Reclamation
Operations and Waste Systems, Inc.) landfill in Falls Township,
Pennsylvania, with partial funding from the U.S. Environmental
Protection Agency, demonstration grant No. S-803926.
Publication does not signify that the contents necessarily reflect
the views and policies of the U.S. Environmental Protection Agency, nor
does mention of commercial products constitute endorsement by the U.S.
Government.
An environmental protection publication' (SW-758) in the solid
waste management series.
-------
CONTENTS
Page
Summary and Conclusions 1
!. INTRODUCTION 8
II. OVERVIEW OF LEACHATE TREATMENT OPTIONS 12
Leachate Composition 12
Leachate Treatment 22
Summary 31
III. LEACHATE TREATMENT SYSTEM 33
Design Overview 36
Design Flow 36
Design Leachate Characteristics 38
Design Concept 4o
Leachate Collection System-- 40
Chemical/Physical Section -,- 42
Chemical Precipitation 42
Air Stripping of Ammonia 43
Neutralization and Nutrient Supplementation 44
-------
w>
V *
CONTENTS (Continued)
';. ". ::; ;-ป '^'' '' Page
< ! . ' ! : *':',' -, ' ."
Biological Treatment Section 44
IV. MATERIALS AND METHODS -------__--.*' 47
Experimental Systems -- 47
System 1 - Chemical/Physical fol owed by
.Biological Treatment--- 47
System 2 - Chemical/Physical Treatment 47
System 3 - Biological followed by Chemical/
Physical Treatment -- "- 49
System 4 - Biological Treatment 49
System 5 - Bench-Scale Testing 49
1 " '" " ' ''I ..'.'-' ,.' i'; ~ \ . '.' ..
Process Monitoring 50
Statistical Tests ___-__________________ 52
Presentation of Results ; - 54
V. RESULTS AND DISCUSSION 55
Preliminary Results 55
Raw Leachate Quality 55
Lime Dosage -- -----" 59
Sulfuric Acid Dosage 60
Phosphoric Acid Dosage 60
System 1 - Physical/Chemical Plus Activated Sludge 61
Operational, Comments _________:,___.__. _ 53
Cost Data - 72
* ' ' . i ." : '] ' n , - ' ' - f r
Nitrification __-___ .______._ _..., 75
Summary ,-ซ-^-^ซ- 90
-------
';. " , ' CONTENTS (Contfnuedj
vt- Page
System 2 - Chemical/Physical Treatment 90
Operational Comments 95
Cost Data : --' 95
Factors Influencing Lime Treatment Performance 95
Systems 3 and 4 - Biological Treatment of Raw Leachate 104
System 5 - Laboratory Studies 107
Activated Carbon ' 107
Additional Laboratory-Scale Studies 115
Leachate Treatment Plant Startup 125
VI . CONCLUSIONS 132
VII. REFERENCES _-_. 136
-------
LIST OF TABLES
Page
1 - Summary of System 1 Operation Data- 6
2 - The Strength of Raw Leachates 13
3 - Effect of Solid Waste Disposal on Groundwater Quality 17
k - Effect of Landfill Depth on Leachate Composition and
Pollutant Removal at the University of West Virginia
iOฃE:____________________________________________________ 1S
I j3Op " IO
5 - Theoretical Removal of Heavy Metals During Lime
Precipitation 27
6 - Leachate Treatability as Hypothesized by Chian and Dewalle 30
7 - Precipitation and Average Monthly Temperature Data
Trenton, New Jersey 35
8 - Summary of Effluent Criteria for GROWS Sanitary Landfill
Leachate Treatment Facility -* 37
9 - Design Leachate Characteristics 39
10 - Periods of Operation of Leachate Treatment Systems 48
11 - Routine Laboratory Chemical Analysis 51
12 - Landfill Leachate Characteristics 57
13 - Effect of Equalization Pond on Raw Leachate Variability 58
\k - System 1 Treatment Performance after Acclimation of
Activated Sludge (August 1, 1976 - May 1, 1977 and
July 1, 1978 - August 31, 1978) ~ 63
15 - Summary of System 1 Operation
(8/1/76 to V30/77 and Vl/78 to 8/31/78) 68
16 - Warm Weather Operation of System 1 ซ 70
17 - Comparison of Series and Parallel Operation of Activated
Sludge Units - - 71
18 - Operation and Maintenance Costs Incurred During the
Operation of System 1 following Acclimation of Activated
Sludge (8/1/76 to 5/1/77 and 7/1/78 to 8/31/78) 73
-------
LIST OF TABLES (Continued)
Page
19 - Ammonia Removal in Activated Sludge Units-"-*-.--*..-* 78
20 - Summary of System 2 Results-- ------ ,---*~ 91
21 - Summary of Effects of Chemical/Physical Treatment---'"'- 93
22 - Summary of Operation and Maintenance Costs During
Evaluation of System 2 (11/15/75-5/1/77 and 11/1/77-
8/31/78) - 96
23 - Summary of Operational Data for Lime Treatment and
Clarification *-*-, 97
2k - Results of Batch Draw-and-Fi 11 Activated Sludge
Experiments to Determine the Extent of Phosphorus
Limi tat ion------------------"--------"*-----*-'"--""'"""""""' 106.
25 - System 3 Operation 108
26 - System k Operation 109
27 - Summary of System 3 Operation Data (5/1/77-8/31/77) 110
28 - Summary of Results of Carbon Adsorption Treatment of Raw
Leachate 112
29 - Treatment of Final Effluent with Bench-Scale Activated
Carbon Columns 113
30 - Pilot-Scale Carbon Treatment of Final Effluent 114
31 - Results of Alkaline Chlorination Studies 118
32 - Experimental Protocol and Preliminary Results in
Evaluation of Lime Treatment Additives 120
33 - Results of Additive Evaluation 121
3k - Preliminary Filtration Results ]2k
35 - Process Loading Rates and Concentrations Observed During
the Period April 1, 1978 through June 30, 1978 129
-------
LIST OF FIGURES
Page
1 - Reduction in COD During Aerobic Treatment 2k
2 - Changes in Total Dissolved Solids (TDS) During Aerobic
Treatment Studies 25
3 - Location of Leachate Treatment Plant 3k
k - Schematic Flow System 1 with Ammonia Stripping Lagoon k]
5 - Schematic of Pilot Leachate Treatment Plant
(Scaled Version of System 1) 53
6 - Raw Leachate Chemical Oxygen Demand 56
7 - Flow Chart for Activated Sludge in Series 67
8 - Effect of Temperature on Specific Oxidation Rate 82
9 - Substrate Inhibition of Nitrification 85
10 - Effect of Low Concentrations of Substrate on Specific
Oxidation Rate (R,) 87
11 - Effect of pH on Clarifier Effluent Nickel Concentration 101
12 - Effect of pH on Clarifier Effluent Mercury Concentration 102
13 - Effect of Leachate Temperature on Clarifier Effluent
Nickel Concentration 103
\k - Carbon Breakthrough Curve 116
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DEMONSTRATING LEACHATE TREATMENT
Report on a Full-Scale Operating Plant
R.L. Steiner, Ph.D., P.E., J.D. Keenan, Ph.D.,
A.A. Fungaroli, Ph.D., P.E.
Summary and Conclusions
The results of 3 years of operation of a full-scale sanitary
landfill leachate treatment plant are reported. The plant is designed
to provide a variety of chemical/physical and biological treatment
sequence options. The chemical/physical units include equalization,
lime precipitation, sedimentation, air stripping, neutralization and
nutrient supplementation. These treatment processes are designed to
remove heavy metals, ammonia and organic materials, and to encourage
subsequent biological treatment by reducing the pH and adding the
nutrient phosphorus. The biological treatment process is activated
sludge designed to provide both organic 5-day biochemical oxygen
demand (BOD,-) degradation and nitrification. The demonstration
leachate treatment plant is designed to provide operational flexibility
in that the flow can be directed through the various unit processes and
i
operations in any sequence.
The purpose of this project was to demonstrate the efficiency of a
number of treatment sequences. Specifically, five modes of operation
were defined and have been investigated. System 1 consists of chemical/
physical treatment followed by activated sludge; System 2, chemical/
-1-
-------
physical treatment only; System 3, biological treatment followed by
chemical/physical; System 4, biological treatment only; and, System 5,
bench-scale studies, including activated carbon adsorption treatment.
Data have been collected which can be used to characterize the
quality of raw leachate generated in an operating sanitary landfill.
These data show that the leachate from this sanitary landfill source
is high in organic matter (average chemical oxygen demand (COD)/liter
of 18,553 mg, average BOD,./! iter of 10,907 mg) and nitrogen (average
NH^-N/liter of 1,001 mg). At the end of the first 2 years of operation
these figures were 11,210 and 17,562; 4,460 and 10,773; and 1,503 and
1,0^7, respectively. Thus, although influent nitrogen values have
fallen, the increase in organic strength has been extremely large. The
raw leachate heavy metal concentrations are somewhat lower than
expected, possibly reflecting the relatively high pH of the leachate.
(Note that all data have been collected with nonfiltered samples.)
High concentrations of ammonia in the raw leachate exceed the
plant's effluent criterion and are sufficient to inhibit the growth of
the activated sludge microorganisms. For this reason the original
plant design was augmented with an ammonia stripping lagoon.
System 5 studies have been conducted for a number of purposes.
Bench-scale tests have provided optimal operating data for chemical/
physical units. In particular, System 5 has provided data for the
r
development of lime, sulfuric acid, and phosphoric acid dosages.
Activated carbon adsorption has been evaluated as a treatment
method for raw leachate. For raw leachate, carbon adsorption did not
prove to be an effective treatment procedure. The inability to use
-2-
-------
carbon adsorption is the result of high suspended solids loading causing
/
pore plugging and the wide range of flow variability.
Pilot scale data have been, collected for System 5, carbon
"**
adsorption of System 1 effluent. In this mode, the carbon column would
serve as a tertiary, or advanced waste, treatment process. The results
indicate that the carbon can remove much of the remaining COD and heavy
metals. The results have been analyzed in terms of Langmuir adsorption
isotherms and carbon breakthrough curves. This way of handling the data
provides preliminary full-scale design information.
Systems 3 and k, those in which raw leachate is influent to the
biological units, have received considerable operating attention. The
results indicate that the raw leachate is not directly treatable by
biological means. Systems 3 and k yield an effluent which is high in
organic matter. The mean effluent BOD from System 3 was 763 mg per
liter. The performance of Systems 3 and 4 has not been satisfactory
for the treatment of this leachate.
Systems 1 and 2 are those In which the raw leachate is treated
first by chemical and physical means. The results of these systems'
are most promising. During the third year, these systems were preceded
by equalization. Lime precipitation followed by sedimentation has been
successful in removing the heavy metals and a portion of the organic
matter. Specifically, this sequence (System 2) has removed about one-
quarter of the nitrogen; one-third of the dissolved solids; one-half
of the organic matter; three-quarters of the suspended solids; and
ninety percent of the phosphates. The sequence has been successful in
-------
removing the heavy metals including one-half of the cadmium and
mercury; two-thirds of the lead, chromium, and nickel; three-quarters
of the copper; over ninety percent of the iron and zinc.
The performance of System 2 has been studied carefully in order to
determine the treatment unit's response to a number of operational
parameters. It was found that temperature and pH both exert an effect
on the concentration of heavy metals in the lime treatment effluent.
However, the response is not identical for all heavy metals. It may be
possible to use the differences in these responses in an operational
control strategy to achieve optimal removal efficiences of selected
contaminants.
An ammonia stripping lagoon is included in the chemical/physical
treatment sequence because of the excessive ammonia levels in the raw
leachate. During the lime precipitation/clarification/ammonia stripping
mode of operation, the following removal efficiencies have been achieved:
66 and 50 percent of the BOD and COD, respectively; approximately 60
percent of the ammonia-N and total Kjeldahl-N; approximately 75 percent
of the suspended solids; 25 percent of copper; 50 to 60 percent of
cadmium and nickel; 64 to 68 percent of lead; approximately 96 percent
of zinc; 98 percent of iron.
The ammonia lagoon has a detention time of 1.7^ days, thereby
providing an equalizing effect. That is, the effect of the lagoon is
to dampen the peaks and to minimize shock loadings on subsequent
treatment units. For example, during the period in which the lagoon
was included in the treatment sequence, the mean ammonia concentration
-------
In the raw leachate was 1001 mg per liter with a standard deviation
slightly larger, indicating tremendous variability. During the same
period, the t] standard deviation interval for the ammonia lagoon
effluent was 203 to 641 mg per liter. Thus, the equalization effect is
significantly beneficial in terms of lessening shock loadings.
During the third year, an equalization pond was used to further
dampen the fluctuations in leachate quality and quantity. This was
done to provide a more even flow to the lime treatment unit. The
effect of the equalization was to reduce influent variability for many
parameters, as measured by the coefficient of variation; and to enable
more uniform dosing of raw leachate with lime.
System 1 provided the best degree of treatment. This sequence
consists of equalization, lime precipitation/clarlficat ion/ammonia
stripping/neutralization/phosphorus addition/activated sludge. In this
operational configuration, excellent removal efficiencies have been
observed, following the adaptation of the activated sludge to the waste
(Table 1). Except for NH^-N, BOD^ and lead, the effluent concentrations
comply with the criteria developed by the Pennsylvania Department of
Environmental Resources and the Delaware River,Basin Commission for
discharge to the Delaware River. The standards for these parameters
were not met because of the unusually severe temperatures of the winter
of 1976-77, and secondarily because of the great increase in raw
leachate strength which began during the second year of this project.
(The treatment performance of System 1 met all standards during periods
with relatively warm weather. During the period up to January 1977
-5-
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TABLE 1
SUMMARY OF, SYSTEM 1 OPERATION DATA
Parameter
Ammonia-N
BOD_
Cadmium
Chromium
COD
Copper
I ron
Lead
Mercury
Nickel
Zinc
8/1/76
Raw
Leachate
mc/l iter
758
11886
0.08
0.26
18490
0.40
333
0.74
0.006
1.76
19.5
to 5/1/77 and 4/1/78 to 8/31/78
Final Discharge
Effluent Percent Standard
mq/liter Removal mq/Hter
75
153
0.017
0.07
945
0.11
2.7
0.12
0.004
0.75
0.53
90.1
98.7
78.2
73.1
94.9
72.5
99.2
83.8
27.4
57.4
97.3
35
100
0.02
0.1
*
0.2
7.0
0.1
0.01
sV
0.6
No discharge standard for this parameter.
-6-
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System 1 consistently met the effluent criteria. Likewise, during
the third project year, the summertime performance of System 1 was
excel lent.)
The System 1 operating data have been examined closely in order to
characterize the ammonia removal mechanisms. In the lagoon this occurs
as the result of volatilization of the free ammonia predominant at high
pH levels. In the activated sludge units, the principal mechanism for
ammonia removal is biological nitrification to nitrate. The rate of
nitrification, expressed as the specific oxidation rate, is a function
of temperature which follows the vari't-Hoff Arrhenius relationship.
The results show that the activation energy is approximately 12350 cal.
q _i
per mole, and the Arrhenius frequency factor is 2.18 x l(r day
The data indicate that substrate inhibition due to ammonium ion
concentration occurs in this system. This relationship has been fitted
to the Haldane inhibition model. The maximum specific oxidation rate
is 3.5 g N oxidized per g biomass/day. The saturation constant is 4
mg per liter, and the inhibition constant is 36 mg per liter.
-7-
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DEMONSTRATING LEACHATE TREATMENT
Report on a Full-Scale Operating Plant
R.L. Steiner, J.D. Keenan, and A.A. Fungaroli
I. INTRODUCTION
The potential for water pollution from sanitary landfill sites has
become recognized in recent years. A number of studies have documented
the great pollutional strength of landfill leachates. The quality
of this material varies with landfill age, nature and moisture content
of the wastes disposed at the site, and hydrologic and soil factors.
In spite of this variability, it can be stated that, especially for
young landfills, the values of the critical sanitary parameters of
leachate are at least an order of magnitude greater than for domestic
sewage. The deleterious consequences following contamination of ground
and/or surface waters by leachate may be severe, and it is for this
reason that leachate treatment is receiving attention.
Solid waste consists of matter which can be decomposed by bacterial
or microbial action, as well as of materials which are inert to
microbiological activity. Some of the compounds, cellulose in
particular, are resistant to biological breakdown, but with sufficient
time decomposition will occur. Because of this resistivity and
necessity to acclimate the biological system, the chemical characteristics
of leachate are time-dependent. To complicate treatment, as the paper
-8-
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decomposes, some of the Inorganic ions which are bound to the organic
matrix are released and can be removed by water percolating through
the landfill. The actual mechanism of removal varies with the component
but includes solution as well as colloidal transport.
The generation of leachate in landfills is complicated and cannot
be generalized simply as surface water percolating through the sanitary
landfill. When refuse is placed in the landfill, decomposition begins
to occur. Some decomposition products may be water soluble whereas the
parent products might not have been. This is especially true of
cellulose. In addition, the inorganic constituents also must be
considered since they vary with the state of decomposition. The amount
of water percolating through a sanitary landfill is the primary control
of leachate quality, but the chemical characteristics of the leachate
are dependent on other parameters, including temperature, water
composition, moisture content, time, mode of decomposition (aerobic,
etc.) and the amount of infiltration of rainfall at the landfill.
Recent studies have shown that leachate is produced in a sanitary
landfill when the precipitation exceeds the net evapotranspiration of
the region. Remson, Fungaroli and Lawrence developed a model for
predicting the movement of leachate through a sanitary landfill.'"
Further results using this model have substantiated the validity of the
approach and prediction of leachate generation patterns is reasonably
accurate. Dass et_ a^. have also used a water budget method for
predicting leachate generation. '
Ground and surface waters can be protected if the landfill is
underlain with an impervious membrane. With proper design, leachate
-9-
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Is then directed toward collection points. A waste such as this, which
Is properly considered an industrial waste, must be treated prior to
surface discharge. The leachate treatment state-of-the-art is still
embryonic, although a few small scale studies have been conducted.
These have demonstrated that neither conventional chemical treatment
nor biological treatment can achieve the high degree of treatment
efficiency expected today. Consequently, although we know that the
pollution potential of sanitary landfill leachate can be avoided by
interception using impervious liners, we are not yet able to define
the optimum sequence of unit operations and processes required for
adequate wastewater renovation.
The U.S. Environmental Protection Agency, Office of Solid Waste,
awarded a demonstration grant (S-803926) to investigate the
effectiveness of alternative treatment sequences as employed at the
full-scale facility in Falls Township, Pennsylvania. A 380 liter
per minute (0.144 mgpd) plant had been constructed to treat leachate
from the GROWS (Geological Reclamation Operations and Waste Systems,
Inc.) landfill. This project had as its primary goal the evaluation
of the technical feasibility, operational efficiency, and cost
effectiveness of four alternative treatment sequences. These are:
(1) chemical/physical followed by biological; (2) chemical/physical
alone; (3) biological followed by chemical/physical; and (4) biological
alone. The chemical/physical processing includes precipitation of
heavy metals by lime addition, sedimentation, air stripping of ammonia,
and neutralization using sulfuric and/or phosphoric acids. Equalization
-10-
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of raw leachate was Initiated during the third year of the project.
Biological treatment consists of conventional activated sludge.
Additional objectives of the study were the bench-scale evaluation of
carbon adsorption on both raw leachate and unit process effluents; and
bench-scale testing to determine chemical dosage, sludge return rates,
aeration rates, and other plant operation criteria (System 5). The
purpose of this document is to present and discuss the results of the
3 years of operation of this facility.
-11-
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M. OVERVIEW OF LEACHATE TREATMENT OPTIONS
The purpose of this chapter is to review the literature regarding
the composition of sanitary landfill leachates and their treatment. In
brief, the character and variability of the leachate dictates the types
of treatment systems which will be effective. The contaminants of
greatest concern fall into several groups. The first group is the
organic chamicals, important primarily because they exert an oxygen
demand on receiving waters which may result in a depletion of dissolved
oxygen deleterious to aquatic life. The second major group of
contaminants found in sanitary landfill leachates is comprised of the
heavy metals. As a group, these elements are of concern because they
are toxic at sufficiently high concentrations. It is conventional
practice to chemically characterize wastewaters such as leachate in terms
of a number of other parameters. These are used for a variety of
purposes including design, operation control, and evaluation of pollution
potential.
Leachate Compos i tion
In 1932, one of the first studies indicating that the disposal of
. solid waste could cause environmental pollution was reported by Calvert
who investigated the liquid waste from a garbage reduction plant in
r\
Indianapolis. In this process the garbage was cooked and the grease
removed to produce fertilizer and animal feed, and the liquid waste was
discharged into an impounding pit or lagoon. An analysis of this liquid
is presented in Table 2, Column 1. Calvert analyzed the groundwater
from existing wells surrounding the lagoon and found that wells up to
-12-
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TABLE 2
THE STRENGTH OF RAW LEACHATES21*'25*
Parameter
Acidity, as CaC03
Alkalinity, as CaCOj
Aluminum Oxide
Ammonla-H
Arsen c
Barium
BOD- 5
BOD -20
Cadmium
Calcium
Carbon, Total Organic
Chloride
COD
Copper
Cyanide
Dlsso ved Oxygen
Fluoride
Hardness, as CaCOj
Iron
Lead
I Hagne I urn
* Manga ese
\jO Nlckc
| NItra e-N
Hitrl e-N + Nitrate-H
Nitrogen, Total
Organ c-N
ptl
Pltosphates, P
Phosphorus. Total, P
Potassium
Sodium
'Specific Conductance
Sulf*te
Sulfide
Suspended Solids
Total Dissolved Solids
Total Sol Ids
Zinc
(I)
3,000-3,300
-
874
_
-
-
-
-
-
66.3
2,950
-
-
-
-
-
-
246
-
182
-
-
-
-
-
-
-
-
-
-
_
-
_
1,000-2. 500
-
.
-
(2)
100-9,450
25-4,000
-
-
-
-
6-7.330
-
-
-
-
280-12,300
-
-
-
0-5.6
-
-
-
-
-
-
-
-
-
-
-
5.7-8.4
-
-
-
.
-
_
.
-
-
-
(3)
.
730-9,500
-
0.2- '180
-
-
-
21.700-30.300
-
240-2,330
-
96-2,350
-
-
-
.,
-
890-7.600
., 7-220
-
64-410
-
-
-
-
-
2-465
6.0-6.5
0.1-10
-
28-1,700
85-1,700
_
84-730
.
-
-
-
(4)
_
.
-
54
-
-
975
-
-
-
-
128
-
-
-
-
-
523
-
.
-
-
_
-
-
.
7
_
-
-
.
_
3
10
-
-
(5)
_
_
,,-
700
-
-
7,745
-
-
-
-
2.000
-
-
-
-
-
-
-
_
-
-
-
-
--
-
200
-
.
-
-
.
_
1,950
_
.
-
-
-
Average Ag
0.5 yr.
(6)
_
3.255
-
4.31
8.5
54,610
-
-
-
1,697
39,680
0.05 .
0.024
_
-
7,830
5,500
-
-
1.66
-
1.70
-
-
-
.
2
-
-
900
680
_
.
11,144
-
e of Fill
6 yr.
(7)
-
4.159
-
O.I
0.8
-
14,080
-
-
-
1.330
8,000
0.05
0.005
-
2
2,200
6.3
-
0.06
-
0.70
-
-
-
6.3
-
-,
810
2
-
_
6.734
0.13
Material
17 yr.
(8)
.
1.001
-
-
4.6
0.3
225
-
-
-
135
40
0.05
0.02
-
0.31
540
0.6
.
.
0.06
-
r.6o
-
_
7.0
3.0
.
74
2
.
.
1,198
0.10
(9)
.
_
"
177
-
-
.
-
-
_
.
2,340
50.715
5.0
_
_
5,500 '
1,640
_
-
0.8
-
-
.
482
43
_
3,800
_
375
-
26.500
_
43,000
129
(10)
_
2,600-23,000
-
- '
-
41,000-180,000
-
-
-
.
-
-
-
_
_
_
.
-
_
. _
-
-
-
-
2,000-10,000
-
-
-.
-
-
-
-
-
-
-
-
J
-'
Range 1
(It)
_
0-20,850
-
0-1,106
-
-
81-33,360
-
0.03-17
60-7.200
256-28,000
4.7-2,467
40-89,520
0-9.9
-
-
-
0-22,800
0-2,820
<0. 1-2.0
17-15,600
0.09-125
-
" -
0.2-10.29
.
-
3.7-8.5
6.5-85
0-130
28-3.770
0-7,700
2,810-16,800
1-1,558
-
10-700
584-44,900
0-59,200
0-370
Range 2
(12)
_
142-3,520
-
1.4-1,028
-
-
3.9-57,000
-
-
76-3,900
70-27,700
60.2-2,467
31.1-71,680
-
.
_
-
.
0.5-2,200
_
35-1. 140
-
-
0.4-10.29
-
-
5.09-7.25
0.25-85
0.5-98
35-2.300
44-1.580
978-16,800
7.4-1,558
-
8.9-923
-
911-55,348
-
Range 3
(13)
_
560
-
155
-
-
6,300
-
-
550
3,600
470
8,000
-
-
.
-
,
<440
_
210
-
-
-
1.5
r
-
5.98
3.2
9
380
280
4,970
90
-
197
-
6,080
-
Reference No.
10 "
*A1T untts are mg per liter except pH (pH units) and specific conductance
(pmho/cm).
-------
500 feet downstream of the site showed a marked increase in magnesium,
calcium, total dissolved solids and carbon dioxide.
Carpenter and Setter, working at New York University in 19^0,
conducted one of the earliest studies concerned with landfill leachate.
Auger holes were drilled through an existing landfill of undetermined
age into the subsoil. Twenty-eight samples of leachate which were
collected in the bore holes were analyzed chemically. The range of
concentrations is presented in Table 2, Column 2. These results showed
a wide variation of concentration over the site, thus indicating the
difference of filled materials at various locations, or the differences
in the age of the refuse at different points. Analysis of groundwater
in the area was not performed; therefore, the effect on the subsurface
environment was undefined.
The first comprehensive research study of sanitary landfills under
controlled conditions was conducted at the University of Southern
20
California. Test bins, simulating landfill conditions, were constructed.
Water was added to simulate the infiltration of 1.12 m and leachate was
collected and analyzed. Table 2 gives the minimum and maximum (Column
3) values of the initial (first ^5.9 liters of leachate per cu m of
compacted refuse) leachate. The most rapid removal (the highest
concentrations) occurred with the first 232 liters per cu m of refuse.
Thus, it was postulated that removal would continue for many years but
at a very slow rate, and it was considered unlikely that all the
constituents would ever be removed.
-------
The same study also examined a field site consisting of 2.4 m of
refuse and 0.61 m of cover material. The refuse was in intermittent
contact with the groundwater, analysis of which showed increases in all
organic ions and a maximum biochemical oxygen demand of 125 mg/liter.
One conclusion of the study was that the dissolved inorganic ions
entering the groundwater through intermittent contact would decrease in
concentration as a result of dilution and adsorption and travel in the
direction of the groundwater movement.
The other conclusions reached in this study are summarized as
follows: (1) A landfill, if located so that it is in intermittent or
continuous contact with ground water, will cause the ground water in the
immediate vicinity of the landfill to become grossly polluted and unfit
for domestic or irrigational use; (2) dissolved mineral matter, entering
ground water as a result of intermittent and partial contact of a
landfill with the underlying ground water will have its greatest travel
in the direction of flow, undergo a vertical diffusion to a limited
extent, and be subject to dilution, the result of which will be a
minimizing of the effect of the entering pollutant ions; (3) a landfill,
if located so that no portion of it intercepts the ground water, will
not cause impairment of the ground water for either domestic or
irrigational use; (4) rainfall alone (in the area of this study) will
not penetrate a 2.3 m thick landfill sufficiently to cause entry of
leachate into the underlying ground water.
Longwel1 stated in 1957 that an appreciable proportion of refuse
could be extracted by water to produce a leachate rich in organic
-15-
-------
21
matter, Inorganic salts (ions), and bacteria. The analysis of a
surface leachate obtained from an unnamed landfill is given in Table
2 (Column 4).
In 1961 the British Ministry of Housing and Local Government
conducted extensive research on the placement of landfills above the
groundwater table (which they called "dry tipping"), and the placement
of landfills below the groundwater table (which they called "wet
99
tipping"). In the "wet tipped" experiment the refuse was completely
submerged and the horizontal groundwater flow rate was equivalent to
138 liters per sq m per day. The leachate quality is Included in Table
2 (Column 5). Analyses of the groundwater before and after contact with
the refuse are given in Table 3. These results show the considerable
extent of groundwater quality degradation due to pollution by leachate.
In 1965, Qasim studied the seepage waters from simulated landfills
23
at the University of West Virginia. Three concrete cylinders 0.9 m in
diameter and 1.2, 2.4 and 3.7 m in height were filled with municipal
refuse. Approximately 102 cm of precipitation were artificially added
to the cylinders over a period of 6 months and leachate samples were
collected. The maximum concentrations of certain organic and Inorganic
components in the leachate from the three cylinders are presented in
Table k. Table 4 also presents the total weight removed per cubic
meter from each depth of fill by 102 cm of simulated infiltration.
A summary of results presented by Qasim demonstrates the effect of
depth on leachates generated by landfills. Concentrations of various
pollutants were higher in leachates obtained from deeper fills.
Concentrations of various pollutants per unit depth of fill decrease
-16-
-------
TABLE 3
EFFECT OF SOLID WASTE DISPOSAL ON GROUNDWATER QUALITY-
GROUNDWATER QUALITY BEFORE AND AFTER INTRODUCTION
OF "WET TIPPED" LANDFILL - 196126
Concentration (mg/liter)
Measured Quantity
Total Solids (Residue)
Chloride
Alkalinity, as CaC03
Sulfate
Biochemical Oxygen Demand (BOD^)
Organic Nitrogen
upstream or
Landfill
450
30
180
120
0
0
Downstream or
Landfill
5,000
500
800
1,300
2,500
70
-17-
-------
Table 4
EFFECT OF LANDFILL DEPTH ON LEACHATE COMPOSITION AND
POLLUTANT REMOVAL AT THE UNIVERSITY OF WEST VIRGINIA - 1965
29
CO
I
Concentration (mg/liter)
Parameter
Alkalinity, as CaCO
Bicarbonate ^
BOD5
Chloride
Hardness, as CaCO^
Nitrogen, Total
Sodium and Potassium
Solids, Total
Sulfate
0./6 m
Fill
10,630
14,760
951
7,600
613
1,63'f
21,140
--
1.98 m
Fill
16,200
26,200
2,000
13,100
i,389
3,963
49,800
__
3.1 m
Fill
20,850
--
33,360
2,310
10,950
2,508
5,109
59,000
Pollutant Removal (kq
0.76 m
Fill
..
9.4
12.7
0.8
2.8
0.6
22.0
__
nc
1.98 m
Fill
7.1
10.6
0.6
1.8
0.6
16.6
n *
j>er cu m)
3.1 m
Fill
5.9
9.0
0.6
1.1
0.6
14.4
n o
-------
with increasing depths of refuse. For an equal amount of influent,
shallower fills showed greater extraction rate per unit volume of fill
than deeper fills. The bulk of the pollution was attributed to initial
leaching.
Anderson and Dornbush conducted an extensive investigation of the
27
groundwater leaving a landfill in Brookings, South Dakota in 1967.
An abandoned gravel pit of 160 acres with its base well below the
water table was filled with municipal solid waste. The purpose of the
investigation was to determine which chemical parameters were the most
reliable indicators of the influence of landfi1 Is on the groundwater.
Groundwater samples from 22 wells located over the site were analyzed
for chloride, total hardness, alkalinity, sodium, pH, potassium, iron,
nitrate, and specific conductance. A considerable increase in all
constituents measured was observed in three wells immediately downstream
of the fill area. Although the authors did not evaluate the potential
pollution of municipal refuse, they did report an increase of up to
50 times the chloride content of native waters in the groundwater
affected by the leachate. The major conclusion of this investigation
was that two of the most important indicators of pollution from
landfills are chlorides and specific conductance or total dissolved
solids. Chloride ions are easily detectable, not readily absorbed by
soils, not affected by biological processes, and apparently an abundant
product of leachates.
Disposal sites in northern Illinois were investigated in 1970 by
28
Hughes et_ aJL Leachate samples from three landfills of varying age
-19-
-------
were obtained as near to the base of the refuse layer as possible. The
results of these analyses are presented in Table 2 (Columns 6-8).
Although no information is given In the study as to the composition of
the solid waste in each fill, and the analyses were performed on only one
sample, the results do show a decreasing trend with time. However, it
was noted that refuse more than 15 years of age can still have a high
total dissolved solids contentindicating that the stabilization of
landfills is a long process.
The laboratory simulated landfill or lysimeter study conducted at
Drexel University from 196? to 1972 is the only study reported that was
conducted under completely controlled laboratory conditions. It was
also the only study reported in which the environmental conditions
completely simulate the existing climatic conditions of a region, In
this case, southeastern Pennsylvania. The refuse was placed at as
received moisture content and allowed to reach field capacity naturally
through the addition of amounts of distilled water equal to the
precipitation of the area m'nus the evapotranspiration. This
infiltration was added on a weekly basis and varied from a rate of 8.9
cm per month during the wet periods to zero during the dry or summer
periods. Approximately one year was required for the refuse to reach
field capacity, but small quantities of leachate were generated before
field capacity was reached. The maximum concentrations obtained in the
first year are given in Table 2, Column 9.
It was concluded that this initial leachate production came from
the following sources: (l) From the refuse. Most of the initially
generated leachate is squeezed from the organic components of the refuse
-20-
-------
by the compaction and placement procedure. (2) From channeling. Some
of the water added at the top of the lysimeter may find a direct route
through the refuse to the collection trough, due to any inhomogeneities
in the refuse. (3) From an advanced wetting front. The wetting front
in the refuse probably moves as a broad band rather than as a single
line interface. As a result, substantial increases in leachate will
occur before the entire system is at field capacity, (4) From the main
wetting front. This is the leachate which is produced when the system
reaches field capacity. At this time,:the input water and the output
leachate quantities become approximately equal.
Other studies have mentioned the leachate problem of refuse
disposal in papers dealing with other aspects of the solid waste problem.
Leo Weaver has stated that municipal refuse can generate leachates high
in organic pollutants. Data from this study are included in Table
2 (column 10).
Engineering Science in a study conducted in 196? in southern
California concluded that groundwater pollution, which may arise from
refuse leachate reaching a water source, will be shown largely as an
32
increase in total dissolved solids and specific conductance.
Walker in 1969 found that a sand and gravel aquifer in Illinois
was ineffective in removing dissolved chemical ions generated by a
landfill. He did report that travel of leachate through a short
distance (3 to 5 m) of this aquifer will remove organic pollutants
generated by landfills in Illinois and concluded by stating that
inorganic pollutants constitute the greatest source of concern.
-21-
-------
Roessler noted an increase in inorganic pollutants in an industrial
water supply 2ฃ miles downstream from a refuse dump 10 years after the
3k
dump had started operation.
Table 2 (columns 11 to 13) presents a summary of values of raw
leachate composition as compiled by Chian and DeWalle." The ranges
represent leachates examined by a number of investigators (Range 1
Column II) and a variety of leachates studied at the University of
Illinois (Range 2Column 12). These data are the results of a recently
completed literature review. Another recent report summarizes the
state-of-the-art with respect to ground water monitoring for leachate
contamination.^6This paper should be consulted before initiating a
monitoring program.
The conclusion to be drawn from this review of landfill leachate
quality (as summarized in Table 2) is that its composition is highly
variable from site to site. In addition, the data show that even at
a given landfill, considerable variation is encountered with respect
to both space and age. That is, variability is a factor within a
landfill and also over the history of the site. Consequently, it is
concluded that landfill leachate quality cannot be predicted a priori;
and that this quality is even variable at a given site.
Leachate Treatment
Leachate treatment systems have been evaluated on a laboratory
scale at Drexel University. In one study, the purpose was to
characterize the biodegradation of organic matter both with and without
the supplementary addition of chemicals. The system consisted of
-22-
-------
five aerobic units which were treated in the following manner:
(1) control-no treatment; (2) addition of sodium hydroxide to pH 9;
(3) addition of sodium hydroxide to pH 11; (A) addition of lime;
(5) addition of lime plus sodium carbonate. Otherwise, all units were
handled in the same manner. This procedure included preparation of an
activated sludge culture by aerating leachate. Each experimental unit
was seeded with this culture and was aerated at a rate of Sk liters of
air per gram chemical oxygen demand (COD) (1500 cu ft per Ib COD).
During the testing, all settled solids were recycled to the aeration
tank with no sludge wastage. The aeration treatment systems were
operated on a continuous basis with a hydraulic residence time of
five days.
The COD values decrease quite rapidly during the first six days
and thereafter approach a limit (Figure 1). The results Indicate that
there are components of leachate which are not amenable to treatment
in an aerobic system. The time of adaptation of microorganisms for
treatment of the organic fraction of leachate may be considerably longer
than normal sewage. Volatile solids concentrations In these tests were
low when compared to normal activated sludge systems. This may be one
reason for the long time required for stabi1ization.
A high variation in the concentration of total dissolved solids
in the treated effluent was noted (Figure 2). The cyclic variation of
several systems is of interest, but not all of the systems show this
phenomenon. Since the withdrawal and addition of leachate was constant,
there was no reason for the cyclic effect. Only pretreatment with lime
-23-
-------
I
NJ
3000
FIGURE 1. REDUCTION IN COD DURING
AEROBIC TREATMENT
2000
D)
o 1000
o
Treatment^
No
o Lime.NdjCO,
Lime
0 2
TIME (DAYS)
-------
Is)
VJ1
I
FIGURE 2. CHANGES IN TOTAL DISSOLVED
SOLIDS (TDS) DURING AEROBIC
TREATMENT STUDIES
-------
gave any type of stability and COD reduction.
Thus, neither biological waste treatment nor chemical-physical
treatment separately is able to reduce the biochemical oxygen demand
(BOD)more than eighty percent. In fact, the efficiency of the
chemical-physical process is considerably below this level. It is
hypothesized that two reasons exist fpr the poor removal efficiency of
each individual system: l) the large percentage of high molecular weight
organic materials, and 2) the biological inhibition caused by heavy
metal presence. The physical-chemical treatment is needed to remove
the metals and also to hydrolyze some of the organics, and biological
treatment to stabilize the degradable organic matter.
In addition, biological treatment alone does not remove significant
amounts of the heavy metals. In fact, biological units may be inhibited
due to the toxic effects of the metals. Consequently, chemical and/or
physical processing is needed for the removal of substantial amounts of
these1materials. Lime treatment is particularly effective in that it
creates the alkaline conditions under which the metals become insoluble.
The removal of heavy metals during lime precipitation depends upon
the formation of insoluble metal compounds, primarily hydroxides, at
alkaline pH. The optimum set of conditions is not identical for all
metals, and the result is that it is impossible to achieve the maximum
theoretical removals for each metal within a single tank. In general,
jQ
the optimum pH levels are in the range of 7-10.3 (Table 5).
Hexavalent chromium is not removed by lime addition unless It has
previously been reduced to trivalent chromium.
-26-
-------
TABLE 5
THEORETICAL REMOVAL OF HEAVY METALS DURING LIME PRECIPITATION**1
Cadmium
Hexavalent chromium
Trivalent chromium
Copper
Soluble Iron
Lead
Nickel
Zinc
Theoretical Effluent
Optimum pH Range Concentration mg/liter
10
8.5-9.5
9.0-10.3
7
10
1.0
0.01
0.01
-27-
-------
These studies demonstrated that the aerobic treatment of sanitary
landfill leachate is feasible and that pretreatment may be required.
Lime precipitation appears to be the most favorable pretreatment method.
The organic fraction of leachate was found to contain substances not
readily assimilated by the microorganisms, and it was hypothesized that
chemical treatment is needed to remove these organics.
39
Chian and DeWalle have treated lyslmeter leachate anaerobically.
They used a completely mixed anaerobic filter with recirculation of
effluent. The unit responded well to shock loads, produced low sludge
yields and operated without nutrient supplementation in spite of a COD:
N:P ratio as high as 4360:112:1. Heavy metal toxicity was minimized by
the addition of sodium sulfide.
Chian and DeWalle have recently completed an extensive review of
40
leachate treatment techniques. Their conclusion was that leachate
collected from recently leaching landfills is best treated biologically.
This is because the organic fraction of such leachate is composed
predominantly of free volatile fatty acids which are readily
biodegradable by either aerobic or anaerobic means. On the other hand,
leachate from older landfills is more efficiently handled by
chemical-physical processes, because these organics are more resistant
to biodegradation. They also concluded that activated carbon and reverse
osmosis were the most efficient chemical-physical methods in terms of the
removal of organ Ics.
A more recent study by Chian has been devoted to a detailed analysis
of the constituents of the organic fraction of grossly polluted
groundwater and of leachate collected from wells or underdrains near
-28-
-------
k2
solid, waste disposal sites. The techniques used for concentrating;
separating, and characterizing the soluble organics were membrane
ultrafiltration, gel permeation chromatography and'analysis for functional
groups and specific organics. The free volatile fatty acids constituted
the largest fraction and this fraction became relatively smaller as the
age of the landfill increased. Increasing stability with increasing
landfill age was noted for other groups of organics. These results tend
to confirm the concept that biological treatment is best suited for
treating leachate from a young landfill, and that physical-chemical
processes are more appropriate for older landfills.
The compilation of data presented by Chian and Dewalle indicate
the following range of COD removal efficiencies for various treatment
methods: 0 to 98 percent for aerobic biological; 87 to 99 percent for
anaerobic biological; 17 to kO percent for aerobic/anaerobic biological;
0 to kO percent for chemical precipitation with alum, ferric chloride,
ferrosulfate or lime; 3k to 3k percent for activated carbon and ion
exchange; 0 to k8 percent for chemical oxidation; 56-98 percent for
k3
reverse osmosis.
As a means to bring order to the wide disagreement found in the
literature, Chian and DeWalle postulated that the age of the landfill
affected the character of the leachate, and that this character is best
measured in terms of the ratios of chemical oxygen demand to total
organic carbon (COD/TOC) or of biochemical oxygen demand to chemical
oxygen demand (BOO/COD) (Table 6).
A recent laboratory scale study by Uloth and Mavinic is closely
related to the present effort. They studied aerobic biological
-29-
-------
TABLE 6
LEACHATE TREATABILITY AS HYPOTHESIZED BY CHIAN AND DeWALLE^7
COD
TOC
>2.8
2.0-2.8
<2.0
Leachate Qual i ty
BOD
COD
>0.5
D.l-0.5
<0.1
Age of
Fill
Young
(<5 yr)
Med i urn
(5 yr-10 yr)
Old
(>10 yr)
Treatment Efficiency"
COD,
mg/1
>10,000
500-10,000
<500
(D
U
ซ
01
o
"o
CO
G
F
P
c
o
4->
(D
r~ <4-J
(D
0 D.
'i '5
0) U)
tft .
Rever
Osmos
F
G
G
o
0>
4J
TO C
> O
J3
4-> U
U (D
< 0
P
F
G
0)
01
c
ro
.c
C U
O X
LU
P
F
F
O
I
*(G ป good; F = fair; P = poor)
-------
treatment of very strong leachates. They were able to develop kinetic
constants fitting the Lawrence-McCarty model. Successful operation was
attained at mixed liquor volatile suspended solids concentrations of
8000 to 16000 ppm at sludge ages in excess of ten days.
Summary
The state-of-the-art concerning the composition and treatment of
sanitary landfill leachates has been assessed. The most obvious
characteristics of leachate are its strength and its variability.
Leachate Is generally of much greater strength than domestic sewage.
This Is especially true in terms of organic materials and the potentially
toxic heavy metals. As important a characteristic as strength is the
variability of leachate composition. Leachate quality not only
fluctuates from landfill site to site, but also from time to time at
one landfill. Changes over time result from differences in seasonal
hydrology and microbiological activity. Rainy weather may dilute the
leachate, but, at the same time, may flush out large quantities of
pollutional material. The typical pattern observed over many years is
that the pollution potential of leachate is greatest during the first
five years or so after placement, but that leachate strength remains
significant for as long as ten to twenty years. This sequence is
encountered because the microbiological processes responsible for the
decomposition of the solid wastes are relatively slow acting and are
first directed at the most readily biodegradable components of the
waste.
Considerable differences are encountered in leachate quality when
comparing landfills. In addition to the seasonal, hydrologlc and age
-31-
-------
of landfill factors mentioned above, there are several other reasons
for this observation. The chemical nature of the wastes accepted at
the landfill has a marked effect on the composition of the leachate.
The land disposal of industrial liquid and solid wastes is critical in
this light.
The variability and the strength of leachate have important waste
treatment implications. First, the sheer magnitude of the measures of
pollution potential dictate the use of thorough waste treatment. Second,
the changes encountered from landfill to landfill are such that waste
treatment techniques applicable at .one site are not necessarily directly
transferable to other locations. That Is, It may be mandatory that each
instance be separately engineered to achieve adequate treatment. Third,
the fluctuations in leachate quality which occur over both short and
long term intervals must be accounted for in the treatment design. Not
only must processes be designed to treat efficiently the waste flow from
minute to minute, but the design must also reconcile the possibility
that treatment techniques which work well for a young leachate may
become wholly inadequate as landfill age increases.
It is apparent today that most landfill leachate cannot be treated
adequately by just conventional chemical/physical treatment or
conventional biological treatment. Rather, what Is needed is a
combination of the two approaches with perhaps a supplementary form of
advanced wastewater treatment. The purpose of this project is to
Investigate, at both the full and bench-scale levels of operation, the
efficiency of treatment afforded by these processes. """""
-32-
-------
III. LEACHATE TREATMENT SYSTEM
The,, leachate treatment faci 11 ty used fn this study Is located at
the GROWS landfill In Tullytown, Falls Township, Bucks County,
Pennsylvania (see Figure 3). The plant is designed to provide maximum
operational flexibility in order to permit full-scale testing of a
variety of treatment sequences. Plant design and treatment modes are
considered in subsequent paragraphs.
The sanitary landfill has a surface area of 50 acres. The landfill
will be filled with about 1,400,000 cu rn of refuse over the next several
years. The time required to fill the landfill depends upon many unknown
factors, but it is estimated that it will probably be between 5 and 10
years. The receipt of refuse is about 800 tons per day. Eighty-five
percent of the refuse is from municipal sources. The remainder is
industrial and commercial. The landfill is also permitted to accept
sewage sludge and selected industrial liquid wastes.
The landfill is located in the semi-humid northeastern part of the
United States. The thirty year monthly average precipitation and
temperature data are given in Table 7. In this region there is a net
positive infiltration of rainfall into the landfill. As long as there
is a net positive infiltration, leachate will eventually begin to be
produced by the landfill. *
Because of these meteorological conditions and the site hydrologic
situation, groundwater pollution potential existed. To alleviate this
pollution potential the Pennsylvania Department of Environmental Resources
required the landfill to be underlain by an impervious asphaltic membrane.
This membrane system was designed to collect and transport the leachate
-33-
-------
. LOCATION OF LEACHATE TREATMENT. PLANT
15
' PENNSBURY MANOBJ
STATIC PARK!
, , .iii?ir<
- ja&iy-J ^ :
x%v "
ง0" 518 J83COOO FEET (PA.)
74ฐ45'
Heavy-duty
Medium-duty
ROAD CLASSIFICATION
Light-duty
PENNSYLVANIA
Unimproved dir' = =
O State
- S- Route
Interstate Route
QUADRANGLE LOCATION
TRENTON WEST, PA. N. J.
NEM BURLINGTON 15' QUADRANGLE
N 4007.5 W 7445/7.5
-34-
-------
TABLE 7
'PRECIPITATION AND AVERAGE MONTHLY TEMPERATURE DATA
TRENTON, NEW JERSEY**8
Month
January
February
March
April
May
June
July
August
September
October
November
December
Total
Rainfall
cm
8.87
6.58
9.75
8.15
9.19
9.14
10.62
12.12
8.89
7.21
8.03
7.29
104.85
in.
3. JO
2.59
3.o4
3.21
3.62
3.60
4.18
4.77
3.50
2.84
3.16
2.87
41.28
Temperature
0.8C
1.0
5.1
11.1
16.9
21.7
24.2
23.3
19.6
13.5
12.7
1.7
33. 4 F
33.8
41.3
52.1
62.7
71.4
76.0
74.3
67.6
56.5
45.1
35.1
-35-
-------
to the leachate treatment plant.
The treated effluent is discharged to the Delaware Estuary. The
river zone is tidal and flow figures are not available. At the nearest
gage (Trenton) the drainage area is 6700 square miles and the projected
low flow is 33,000 liters per second. The discharge of treated effluent
directly to the Delaware River occurs only during the months of December
through April. During the remainder of the year, the effluent is
returned to the landfill. During the latter portion of the third year,
a program of land disposal was initiated. The landfill has ample storage
capacity in the pore space so that storage for 6 months does not create
any difficulties. The effluent is spread on the landfill using aeration
nozzles.
The treatment plant operates under permits from the Commonwealth of
Pennsylvania Department of Environmental Resources Water Quality Section
and the Delaware River Basin Commission. The effluent criteria for the
facility are summarized in Table 8.
Design Overview
The purpose of this section Is to summarize briefly the design
criteria and to discuss the design of the treatment facility. The
effluent limits have been mentioned above and presented in Table 8.
The following paragraphs are devoted to a discussion of the leachate
quantity and quality as estimated for design purposes.
Design Flow. The source of liquid waste is the leachate which
results from the degradation of refuse and percolation of rain water
through the landfill. In addition, as the treated effluent is recycled
to the landfill during the summer months, and to the Delaware River
-36-
-------
TABLE 8
SUMMARY OF EFFLUENT CRITERIAH3 FOR
GROWS SANITARY LANDFILL LEACHATE TREATMENT FACILITY
Maximum Concentration
Parameter mg/liter
BOD5
Ammonia-N?trogen
Phosphate
Oi 1 and grease
I ron
Zinc
Copper
Cadmium
Lead
Mercury
Chromium
100.0
35.0
20.0
10.0
7.0
0.6
0.2
0.02
0.1
0.01
0.1
-37-
-------
during the winter, the raw leachate volume Includes this recycled
effluent. The quantity of waste which is generated is dependent upon
many Individual factors of the landfill. The maximum generation of
waste (Including the recycled volume) for design purposes was estimated
to be about 20 liters per sq m-week at this site. However, the production
of leachate Is dependent upon the time cycle, both as to placement and to
the season of the year. Leachate itself occurs as the result of the
excess of infiltration over evapotransplration and the soil moisture
deficit. Thus, the actual generation of leachate depends upon
precipitation patterns, landfill moisture and effluent recycling.
Since the generation of leachate is also a function of the age of
the fill, not all the expected leachate will be produced simultaneously.
There Is an initial period of operation when the landfill comes to field
capacity, followed by an extended period of leaching of contaminants,
after which there exists a period when the leachate is no longer of a
polluting nature. It is possible that some portions of the landfill
will be in this latter state when the final parts of the landfill are
being completed. Hence, the maximum flow of 20 liters per sq m-week Is
a value which may never be attained for extremely strong leachate. This
maximum flow rate was determined using the site meteorological data
presented In Table 7 and the procedure developed by Remson, Fungaroli
and Lawrence.
Design Leachate Characteristics. The leachate strength parameters
used for design purposes are presented in Table 9. These were obtained
through a modest sampling program conducted during the very early stages
-38-
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TABLE 9
DESIGN LEACHATE CHARACTERISTICS
Const!tuents
Raw
BODg
Suspended Sol ids
Total Solids
Percent Volatile
pH, pH units
Chlorine
Iron, total
Zinc
Chloride
Organic Nitrogen
Nitrate
Sulfate
Copper
Hardness
Alkalinity
Color, standard units
Flow, mod
Temperature, F
1500
1500
3000
55
5.5
200
600
10
800
100
20
300
1
800
1100
50
.iMt
80
''All units are mg/liter except pH, color,
flow, and temperature.
-39-
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of the landfill. However, as discussed In Chapter II, the exact
character of waste is difficult to predict for a number of reasons,
including the fact that it is subject to dilution when the infiltration
is high. In addition, because of the on-slte variability, it is
possible that single samples do not accurately reflect the character
of the waste.
Design Concept. As discussed in Chapter II, a combination of
chemical/physical treatment plus biological treatment is often required
for leachate treatment. The principle is that the chemical/physical
units can be used for the removal of refractory organics and for
pretreatment prior to the biological process. In the latter case, the
chemical/physical processes are used for the removal of potentially
inhibitory materials such as heavy metals and ammonia-nitrogen. The
function of the biological units Is the stabilization of organic matter
and the oxidation of ammonia nitrogen. As a result of the findings
discussed in Chapter II and the design leachate quality, this treatment
plant was designed to consist of lime treatment and sedimentation
followed by activated sludge and chlorination. Equalization, air
stripping of ammonia and nutrient addition have subsequently been added
into the chemical/physical section. A schematic of the leachate treatment
plant appears as Figure 4.
Leachate Collection System. The raw leachate is contained within
the lined landfill which was designed to allow for the collection by
gravity of leachate at three locations. These locations are outfitted
with manholes from which the leachate is pumped and transported via
pressure lines to the treatment facility. The leachate entered the plant
-40-
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FIGURE k. SCHEMATIC FLOW SYSTEM l.WITH AMMONIA STRIPPING LAGOON
Unit volumes are shown in cubic meters (l cu m = 1000
liters = 264.2 gal = 35-3 cu ft)
Sludge
Holding .-
21 cu m-*V
i
^x-
Manhole flleac
""' Pump7
Equalization
Lagoon
950 cu m
23.7 cu m each
75.71 cu m /I Chlorine ,
"* Aeration *J -^-, Contact /" i'b cu m
Chamber / ,JU
<*ฃ ซ)i ., /.,. . River
/3.7-1 cu m ^i * -' ป
ป Aeration ^ b . ,r , ,
Chamber ' LdndFill
L Sludge '
^_H2S0l| J
^^"^ II M IV 1
V ft
Ammonia Stripping
Lagoon
950 cu m
-------
via a one thousand gallon holding tank In which little mixing occurred
because the flow from the individual manholes is highly variable, and
pumped sequentially. Following start-up of the equalization pond in
the third year, the holding tank was by-passed.
Chemical/Physical Section
The chemical/physical portion of the plant consists of the
following: equalization, chemical precipitation and coagulation,
sedimentation of precipitate, air stripping at elevated pH for ammonia
removal, neutralization and nutrient supplementation. Each of these are
discussed in the following paragraphs.
An equalization pond was put on-line during the final project year.
The volume is 950 cu m, and so the design detention time is 1.7^ days.
This pond is aerated to maintain aerobjosis and prevent solids deposition.
A chlorinated polyethylene liner is used as the inner wall of the pond.
Chemical Precipitation. In the chemical treatment phase, the major
design goal was the removal of inorganic materials. In particular, metals
that may interfere with the subsequent biological treatment process are
removed; also, the metals are removed to achieve discharge standards
(Table 8). As part of the chemical treatment, the biochemical oxygen
demand will also be reduced, and the design percentage of reduction was
30 to 50 percent, on the basis of the experience with municipal
wastewater and with leachate as discussed In Chapter II.
The chemical treatment step consists of flash mixing followed by
quiescent conditions favorable for coagulation as well as sedimentation
of the chemical sludge. Lime has been the only chemical utilized in
-42-
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this chemical precipitation step. However, additional feeders and points
of injection have been provided for the use of other chemicals if
necessary. Other chemicals which might be used include alum, ferric
chloride, synthetic polymers, and powdered activated carbon.
This unit is an upfldw solids contact reactor clarifier. Lime
slurry is added to cause coagulation and precipitation of the waste
materials. The time is pumped at a rate commensurate with the rate of
leachate production. The lime slurry is flash mixed with the Incoming
waste, and mixing, flocculation and upflow clarification occur within
a single unit. Solids contact may be optimized by variable sludge
recycle. The chemical treatment facIIIty Is a 3.66 m diameter, 3.66 m
deep cylinder with a hydraulic retention time of 1.7 hours at 380
liter/min flow rate.
Sludge Is drawn off the bottom of the reactor clarifier and placed
in a common sludge holding tank with the waste activated sludge. Sludge
return pumps are available to recirculate the sludge and mix it with the
incoming waste water to reduce the amount of chemicals that are needed
for precipitation. (However, the practice to date has been to use fresh
lime and to not recircUlate the sludge,). The amount of sludge that
is produced in this step depends upon the composition of the leachate.
The design projection was that approximately 5 percent of the flow will
be produced as sludge at 1 percent solids concentration.
Air Stripping of Ammonia. As a means of controlling excessive
levels of ammonia In the lime treated stream and in the final effluent,
a lagoon incorporating air stripping of ammonia is included in the
chemical/precipitation-clarification unit In order to take advantage of
-43-
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the high pH of the .upflow solids contact reactor clarifier effluent and
to minimize the solids loading on the lagoon. On occasion, sodium
hydroxide has been added to the lagoon to further elevate the pH and
force off additional ammonia. This has been done during cold weather
periods.
The volume of the ammonia lagoon Is 950 cu m, thus providing a
detention time of approximately 1.7^ days at design flow. The primary
function of the lagoon is to encourage air stripping of ammonia by an
elevated Influent pH of 10,.aeration and high internal recycle. The
lagoon is lined with chlorinated polyethylene. In addition to ammonia
removal, the-lagoon provides equalization in terms of both flow and
sanitary parameters.
Neutralization and Nutrient Supplementation. Sulfuric and
phosphoric acids are added to reduce the pH of the leachate prior to
entering the biological waste treatment portion of the process.
Phosphoric acid replenishes the supply of o-phosphate, a necessary
biological nutrient, which Is precipitated and removed following the
addition of 1Ime.
Biological Treatment Section
The biological treatment units consist of two aeration tanks and two
secondary clarifiers. The units may be operated in series or parallel.
The capacity of each tank is 75,710 liter, which corresponds to a 6,6
hour detention time at the maximum flow rate of 380 liter/mln. The
aeration chambers are provided with diffused aerators, each driven by
a 1^.2 cu m per min blower.
-------
Depending on the actual hydraulic residence time In the aeration
tanks, the activated sludge units were designed to operate in either the
conventional or extended aeration modes. In order to achieve this, the
mixed liquor volatile suspended solids (MLVSS) would be maintained In
the range of 3000 to 8000 mg/liter. Because of the high organjcs loadings
experienced during the last 2 years, the MLVSS was in the 8000 to 16,000
mg per liter range. This level Is high relative to that normally
maintained in units handlIng municipal wastewater. However, It is
necessary because of the high BOD loading, and because of the requirement
to remove about 90 percent of the BOD remaining after chemical/physical
treatment. The MLVSS is maintained by return sludge pumps capable of
delivering a return sludge flow equal to 200 percent of the Influent
flow.
The waste sludge from the activated sludge units and from the
chemical treatment process is stored in the sludge holding tank. The
capacity of this tank is 21 cu m, and sludge Is removed as required
and conveyed back to the landfill via tank truck.
Separation of treated wastewater from the MLVSS is achieved by
gravity sedimentation in the secondary clarifiers. The total clarifier
volume is 47,318 liters, in two parallel independently SperSble units.
Sludge return is provided with air lifts Installed In the final settling
tanks. A skimming device is located fn the settling basin in front of
the scum baffle to remove floating material which is returned to the
aeration compartment. The maximum surface overflow rate is 20.k cu m
per day per sq m (500 gpd/sq ft) based on the peak flow of 380 liter/
min.
-------
Final effluent Is directed to the chlorine contact tank after
secondary clarification. The chlorine contact tank provides a retention
time of 20 minutes at the 380 liter/min flow rate. The effluent after
chlorinatlon is discharged to the Delaware River or to the land disposal
site depending upon the season of the year. The effluent is not
chlorinated when it is recycled to the landfill. The chlorine contact
tank is a simple baffled tank to assure mixing of the chlorine which is
provided by hypochlorlnatlon.
-46-
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IV. MATERIALS AND METHODS
Experimental Systems
The leachate treatment plant', although designed for chemical /physical
treatment followed by biological treatment, was equipped with sufficient
flexibility to provide for operational evaluation of a variety of treatment
sequences. These sequences are each defined in the following paragraphs
with reference to Figure 4. Note that the final effluent is disinfected
with sodium hypochlorite prior to discharqe during the winter months.
The periods of operation of each system is summarized in Table 10. The
principal analysis was conducted during the first two years. Additional
trials were conducted during the third year. The flow rate and raw
leachate qualIty was sufficiently different In the third year to
oftentimes prevent direct comparisons,
System 1 - Chemical/Physical followed by Biological Treatment.
System 1 is the basic treatment sequence with lime treatment for metals
removal followed by ammonia stripping and conventional activated sludge.
System la refers to the use of System 1 when the air stripping was not
used, whereas System Ib signifies that the lagoon was included in the
'flow sequence. System la was tested in the late winter of 1975-76,
and System Ib in the summer of 1976, the winter of 1976-77, the early
spring of 1977, and the spring and summer of 1978. During the 1978 test
period, the raw leachate entered the plant via the equalization pond.
System 2 - Chemical/Physical Treatment. Two subsystems have been
evaluated. These, Systems 2a and 2b, consist of lime treatment either
without or with subsequent removal of ammonia by air stripping. The
-47-
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TABLE 10
PERIODS OF OPERATION OF LEACHATE TREATMENT SYSTEMS
System
la*
Ibt
2a*
2b+
vV
Period of Operation of Full-Scale Units
November 15, 1975 through January 12, 1976
June 14, 1976 through April 30, 1977
January 1, 1978 through August 31, 1978
November 15, 1975 through January 12, 1976
June 14, 1976 through April 30, 1977
January 1, 1978 through August 31, 1978
January 12, 1976 through April 2, 1976
May 1, 1977 through August 31, 1977
January 12, 1976 through April 2, 1976
May 1, 1977 through August 31, 1977
Neither ammonia lagoon nor equalization pond used.
Ammonia lagoon used.
Both ammonia lagoon and equalization pond used.
-48-
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system without ammonia stripping (System 2a) was evaluated in the winter
of 1975-1976; and System 2b in the summer of 1976, the winter of
1976-1977, early spring of 1977, and the spring and summer of 1978.
The equalization pond was included in this treatment sequence during
the most recent,period.
System 3 '- Biological followed by Chertical/Physical Treatment.
This is the reversal of System 1. This system was studied during the
winter of 1976. The results indicated poor treatment efficiency, most
likely due to heavy metal and ammonia toxicity. However, it might have
been argued that a sufficient amount of activated sludge had not
developed. Therefore, System 3 was reevaluated in order to test this
latter hypothesis. This took place during the late spring and early
summer of 1977.
System k - Biological Treatment. This system has been tested, the
results showing poor treatment efficiency. However, as indicated above,
the performance might have improved if a previously acclimated activated
sludge were available. Consequently, System k was operated and tested
simultaneously with System 3 during the spring and early summer of 1977.
System 5 - Bench-Scale Testing. As a supplement to the full-scale
treatment processing, some smaller scale work has been undertaken. This
effort serves two purposes. First, it allows the operator to readily
develop operational guidelines. For example, jar tests have been used
to determine proper chemical dosages.
The second purpose is to provide an opportunity for evaluating
additional treatment techniques. Specifically, bench-scale testing has
been used to evaluate activated carbon treatment of raw leachate,
-49-
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Granular activated carbon has been used fn column studies to obtain
performance characteristics. The results are discussed In Chapter IV,
P rbces s Monitor]ng
An analytical laboratory was established in a trailer located
Immediately adjacent to the treatment plant. The trailer Is outfitted
with the apparatus to perform the analyses indicated below and Is
environmentally controlled with a heating/air conditioning system.
The need for extensive bench-scale testing and the large number of
i
analyses needed for process control and monitoring made the on-site
laboratory mandatory. The laboratory Is operated by the chemist-operator
employed specifically for this project.
The chemical analyses performed routinely are presented in Table 11.
These have been selected on the basis of four criteria: they represent
the most common chemical parameters used in the literature to characterize
landfill leachate; they provide sufficient data to completely evaluate the
unit operations in terms of process and total system efficiency; they are
needed for process control; and they are required to specifically define
the leachate.
All analyses are performed In accordance with the 13th edition
of Standard Methods, ASTM Standards pt-23, and the 1974 edition
of EPA Methods. The analyses are performed on total samples as
opposed to filtrate samples. Some preparation of the raw leachate is
required for heavy metals determinations.
Electrometric techniques are used in the determination of ammonia-N,
dissolved oxygen (with periodic checks using the Azlde Modification of
-50-
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TABLE 11
ROUTINE LABORATORY CHEMICAL ANALYSIS
Item
pH
Chemical oxygen demand
Dissolved oxygen
Mixed liquor suspended solids
Mixed liquor settleable solids
Dissolved sol ids
Volatile suspended solids
Total residue
Alkalinity
Biochemical oxygen demand
Total hardness
Kjeldahl nitrogen
Ammonia nitrogen
Phosphate
Sulfate
Chloride
Total iron
Chromium
Copper
Cadmium
Lead
Mercury
Zinc
Nickel
Ca 1 c i urn
Magnesium
Sod i uin
Potassium
Daily
Method
Dichromate reflux
Electrode
Gooch crucible
Imhoff cbne
PotentiometrJc
Gooch crucible
Drying crucible
Weekly
Titrimetric (pH 4.5)
Probe method
Titrimetric
Titrimetric
Distillation S
Potentiometric
Persulfate digestion
Gravimetric
Titrimetric
AA*
AA
AA
AA
AA
Mercury analyzer
AA
AA
AA
AA
AA
AA
Aperiodic
EPA
Storet
No.
00349
00299
70300
50086
00536
00529
00520
00410
00310
00900
00625
00610
00665
009*15
00940
--
--
--
Detec-
tion
Limit
--
-- .
~*
_..
ซ
--
0.02
0.02
0.01
0.002
0.05
0.0002
0.005
0.005
0.003
0.005
0.002
0.005
Oil & Grease
Freon extraction
Mtomic Absorption Spectroscopy
-51-
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the Winkler lodometric procedure), pH, and dissolved solids. Atomic
absorption spectroscopy is used for iron, chromium, copper, nickel, zinc,
sodium, cadmium, lead, and potassium.
A number of sampling points are used in the analysis program.
Routinely, samples are collected of (l) the raw leachate; (2) chemical/
physical sedimentation tank effluent; (3) ammonia lagoon effluent;
(4) final effluent. In addition, samples are collected on an irregular
basis from the three landfill manholes and directly from the individual
treatment units. In all cases, every effort is made to ensure that a
representative sample is obtained.
A pilot-scale treatment plant was constructed in order to facilitate
the smaller scale studies. This pilot plant was built durinq the spring
of 1977- The basis of its design was to simulate System 1 operation as
it was apparent that this was the most efficient treatment sequence for
this leachate. Thus, the pilot plant would generate final effluent which
could be used in the bench-scale experiments using granular activated
carbon. A schematic of the pilot plant is presented in Figure 5,
Statistical Tests
The following notation is used throughout: n, number of data points;
x, arithmetic mean; and s, standard deviation. The mean is calculated as
x = 1 Vx.
n <' i
and the standard deviation as
s - E(x-x;)2
~ n-1
where the x. are the n data points,
and the coefficient of variation is
-52-
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FIGURE 5. SCHEMATIC OF PILOT LEACHATE TREATMENT PLANT (SCALED VERSION OF SYSTEM l)
i
Ul
OJ
I
Mixing
Tank
? i-
0_ - -100 ml/min
Clari-
fier
(10 qt
1
Sludge
Lime Slurry Raw Leachate
Storage Storage
(50 gal) (50 gal)
Lagoon
gal)
Aeration
Tank
(45 gal)
neutralization
Acid Storage
(10 qt)
Return Sludge
(40 gal)
(35 gal)
(30 gal)
Clarifier
(10 gal)
-------
The value of the coefficient of variation decreases with decreasing
variability.
Presentation of Results
A note of caution is placed here for the reader. As would be
expected in a three year study of this magnitude, a vast array of data
has been collected. It is not appropriate to present the entire data
set in this report. Consequently, many of the tables presented represent
averages taken over certain specified time periods. Thus, values given
In different tables are not necessarily comparable. This is especially
true If the time periods are not identical. The reader is asked to pay
particular attention to the time periods and to avoid making comparisons
when these periods differ.
-54-
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V. RESULTS AND DISCUSSION
Preliminary, Results
Raw Leachate Quality. A summary of actual leachate quality is shown
In Table 12. These data are a summary of the entire set of results. As
is evident from a comparison of Tables 9 and 12, there are significant
differences between the two. These changes toward Increased leachate
strength are seen mainly between the design and actual raw leachate
organic matter, dissolved solids, pH and ammonia. The biodegradable
organics concentration is three times the design level. Dissolved
solids are an order of magnitude greater, caused by increased hardness,
organic matter and chloride. The ammonia concentrations actually
observed have been extremely high and have been a source of operating
problems especially in the biological units. The factors influencing
this difference between the projected and observed leachate quality
have been discussed in Chapter II.
Considerable variability in the raw leachate quality has been noted
on a day-to-day basis. The influent COD data are presented in Figure 6
to show this variability. (An additional indication is provided by the
coefficient of variation data provided In Table 13, columns 1 and 2.)
It was felt that the raw leachate variability had an adverse Impact on
the efficiency of the subsequent treatment units. This was because it
was impossible to fine tune the operational controls as quickly as the
influent quality changed. This was especially true for the lime dosage
in the heavy metals removal step. For this reason, the equalization
pond was constructed. The effect of the pond on dampening of the
-55-
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FIGURE 6. RAW LEACHATE CHEMICAL OXYGEN DEMAND
(Note change In scale on ordinate)
!_
<0
o
o
o
ff\
o
X
J_
-------
TABLE 12
LANDFILL LEACHATE CHARACTERISTICS*
Item
Biochemical oxygen demand
Chemical oxygen demand
Suspended sol ids
Dissolved sol ids
pH, pH units
Alkalinity, as CaCO,
Hardness, as CaCO_
Calcium . ^
Magnesium
Phosphate
,Ammonia-N
Kjeldahl-N
Sulfate
Chloride
Sod i urn
Potassium
Cadmium
Chromium
Copper
Iron
Nickel
Lead
Zinc
Mercury
11/15/75-9/1/76
(5-day) 4,460
11,210
1,994
11,190
7.06
5,685
5,116
651
652
2.81
1,966
1 ,660
114
4,816
1,177
969,
0.043
0.158
0.441
2^5
.531
.524
8.70
.0074
Concentration*
9/1/76-9/1/77
13,000
20,032
549
14,154
6.61
5,620
4,986
894
454
2.61
724
760
683
4,395
1,386
950
0.09
0.43
0.39
378
1.98
0.81
31
.0051
9/1/77-8/31/78
11,359
21,836
1,730
13,181
7.31
4,830
3,135
725
250
2.98
883
611
428
3,101
1,457
968
0.10
0.22
0.32
176
1.27
0.45
11.0
0.012
11/15/75-8/31/78
10,907
18,553
1,044
13,029
6.85
v v j
5,404
4,652
818
453
~ *> J
2 74
mm + ง f
1 ,001
984
^^* i
462
4,240
1,354
961
0.086
0.28
0.39
312
1.55
0.67
21
0.007
These values represent the arithmetic mean of raw leachate- data collected during the indicated intervals.
+A11 units mg/Uter except pH.
-------
TABLE 13
EFFECT OF EQUALIZATION POND ON RAW LEACHATE VARIABILITY
Coefficients of Variation
Unequal ized
Raw Leachate
Equal ized
Raw Leachate
Project Year
Alkal inity, as CaCO_
Ammonia-N
BOD
Cadmium
Calcium
Chloride
Chromium
COD
Copper
Dissolved Sol ids
Hardness, as CaCO,
Iron
Kjeldahl-N
Lead
Magnesium
Mercury
Nickel
PH
Phosphates
Potassium
Sodium
Sqlfate
Suspended Sol ids
Zinc
First Second
0.23 0.21
1.14 0.21
0.60 0.72
0.39 0.80
0.31 0.57
0.58 0.16
0.56 0.32
0.40 0.66
0.81 1.00
>0.24 0.58
1.02 0.48
0.65 0.77
1.23 0.19
0.60 0.68
0.47 0.32
0.90 1.04
0.33 0.97
0.64 2.33
0.63 0.74
0.32 0.21
0.32 0.31
0.90 2.10
0.65 1.32
0.65 0.62
Third
0.26
0.33
0.50
0.73
0.57
0.30
0.49
0.25
0.67
0.16
0.41
0.33
0.39
0.53
0.29
1.73
0.52
--
0.84
0.19
0.16
0.71
0.64
0.68
-58-
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Influent quality Is Impossible to ascertain because raw leachate samples
were not collected after pond startup, Rather, the Influent samples were
taken from the pond. As an approximate Indicator of the degree of
attained equalization, Table 13 was constructed. This compares the
coefficients of variation for each parameter during the three project
years. As shown In Table 13, the variability decreased for one-half
of the parameters and was approximately the same for several others.
This is taken as indirect evidence of the efficiency of equalization.
Lime Dosage. Jar tests were carried out In the laboratory in order
to determine proper dosages for the 1Jme treatment unit. In the first
series of tests, three types of 1 ime were monitored for their ability
to raise the pH of raw leachate to 10,0, The 1Jmes used were high
magnesium lime, high calcium quick 1|me and high calcium hydrated lime.
The results may be summarized as:
Dosage
lb/1000 gal kg/cu m
High Magnesium Lime
High Calcium Quick Lime
High Calcium Hydrated Lime
125
52
50
15
6.2
6.0
It is economically impractical to use the high magnesium because its
properties are such that to raise the pH to 10.5 requires 30 kg per
cu m (250 lb per 1000 gal).
Required dosages to obtain pH 10,0 are nearly identical for both
types of high calcium lime. For pH greater than 10,0, the high calcium
quick lime becomes more efficient and hence (s desirable economically.
However, the slaking characteristics of the quick lime have caused
problems with pumping the resultant slurry so that this lime cannot be
-59-
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used with the available lime feed system. On the other hand, the hydrated
lime does not offer such problems, and consequently, the high calcium
hydrated lime is being used.
Sulfuric Acid Dosage. The amount of sulfuric acid required to lower
the clarifier effluent pH to 6.5 has been determined. To do this,
approximately 0.6 ml of concentrated sulfuric acid per liter leachate
(0.6 gal/1000 gal) is required. The actual dosages used are presented
later in this chapter as part of treatment costs.
Phosphoric Acid Dosage. The heed for a phosphoric acid supplement
became apparent from three lines of evidence: (a) very low phosphate
levels in the chemical/physical effluent; (b) unrealistically low values
obtained In the biochemical oxygen demand test; and (c) poor biological
treatment performance following the chemical/physical process. These
points all Indicated that the chemical/physical treatment effluent is
phosphorus deficient, and that, if biological treatment is to follow, it
must be supplemented with phosphorus. Additional evidence was collected
by performing a series of BOD,, tests in which a variable amount of
phosphorus supplement was added to the bottles. It was observed that
the BOD increased with the amount of phosphorus. In addition, bench
scale tests Indicated greater activated sludge production when o-phosphate
was added. Thus, it has been concluded that orthophosphate, as
phosphoric acid, should be added to form a nutrient supplement.
Additional experiments were performed to address the phosphate
Issue. These were conducted using the pilot scale unit shown in Figure
5. The unit was operated with and without an addition of phosphorus.
-60-
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Raw leachate COD was 4528 mg per liter during the no addition run, and
4823 and 21406 mg per liter during the two runs receiving a phosphate
supplement. The lime clarifier effluent COD values for these runs were'
3926, 4062 and 18121, respectively, and the average fractions of COD
removed during biological treatment were 0.711, 0.811, and 0.762,
respectively. These results indicate that the removal efficiency of
acclimated activated sludge can be improved by the addition of phosphorus,
and that the removals were acceptable when the effluent phosphate
concentration is 1 to 2 mg per liter as P.
The preliminary calculation of phosphoric acid dosage has been made
on the basis of providing a ratio of BQD:N;P of 100:5:1. This is
approximately 4-6 liter (1-1.5. gal) phosphoric acid per day. More
recently, however, the criterion is to add phosphoric acid so that
there is measurable o-phosphate in the bio-unit effluent. This amounts
to about 3.8 liter (l gal) of phosphoric acid per day.
Sy s tern 1 - Phys I ca 1 /C hem i ca 1 Plus Act i va ted S1 udge
System 1 consists of chemical/physical treatment followed by
activated sludge. The early attempts (winter and spring 1976) to develop
an activated sludge culture were not successful. As discussed In
connection with Systems 3 and 4, phosphorus limitation and ammonia
toxicity inhibited these efforts. These two difficulties were overcome
by the addition of phosphoric acid as a neutralizing agent for the lime
treatment effluent and by the use of air stripping of ammonia. System
1 was successful only after the Implementation of these measures and,
as a result, this discussion Is limited to the time period after
implementation.
-61-
-------
The BOD, COD, and ammonia-N data showed a dramatic improvement in
treatment efficiency during and after August, 1976. Approximately four
weeks had been needed to develop the activated sludge microorganisms to
the point where they were capable of rapid growth at the expense of the
leachate substrate. A similar time sequence was observed in 1978
during a re-test of System 1. Table 14 shows the results following the
successful adaptations of the activated sludge. The starting dates for
analysis of these data were chosen at the points.at which the activated
sludge had become fully acclimated In terms of ammonia-N, BOD and COD
removals. The time periods are August 1, 1976 to May 1, 1977 and July
1, 1978 to August 31, 1978,
The results presented in Table H demonstrate the high level of
treatment efficiency attainable with System 1, This treatment system
achieved removals during the 1976-77 trial of approximately eighty-nine
percent or more for ammonia, BOD, COD, suspended solids, and iron; and
greater than two-thirds for alkalinity, hardness, kjeldahl nitrogen,
copper, chromium, magnesium, cadmium, lead, and zinc. Relatively poor
removals of mercury were achieved with System #1, The fairly low removals
of nickel may be related to the relatively low hydrogen ion concentrations.
Based on theoretical considerations of the solubility of nickel hydroxide,
the nickel concentration in the effluent should be on the order of 0,01
35
mg/1 , as opposed to observed average of 0,75 mg/1. This observation
Is perhaps also due to the formation of nickel complexes with unknown
chelating agents within the landfill. Thus, we are able to see removals
as a function of clarifier pH, and this opens the possibility that the
-62-
-------
TABLE 14
SYSTEM 1* TREATMENT PERFORMANCE AFTER ACCLIMATION OF ACTIVATED SLUDGE
(August 1, 1976 - May 1, 1977 and July 1, 1978 - August 31, 1978)
i
ON
(JO
August 1 ,
1976 - May 1,
1977
Concentration
Parameter
Suspended solids
Dissolved sol ids
COD
BOD
Alkal inity
Hardness
Magnesium
Calcium
Chloride
Sulfate
Phosphate
Ammonia-N
Kjeldahl-N
Sodium
Potassium
Cadmium
Chromi-uir;
Copper
Iron
Nickel
Lead
Zinc
Mercury
Flow, gpd
*ft
Influent
686
13563
18M8
12468
51(79
5331
499
929
1(264
645
2.15
70S
748
1310
906
0.08
0.23
0.44
376
1.91
0.82
22
0.006
21034
Effluent**
101
5693
939
118
685
1314
107
347
2592
951
13.7
80
102
821
524
0.01
0.07
0.10
3.0
0.76
0.12
0.57
.004
Percentage
Removal
97.4
58.0
94.9
99.1
87.5
75.4
78.6
62.6
39.2
88.7
86.4
37.3
42.2
87.5
75.0
77-3
99.2
60.2
85.4
97.4
28.9
July 1,
1978 - August
31, '978
Concentration
;VA
Influent
1655
13091
18505
8143
5262
2504
275
653
8578
178
1.39
1076
1248
872
0.06
0.16
0.'20
9.7
0.88
0.30
3.38
.0.003
10,010
**
Effluent
478
7244
1008
464
1496
1456
105
113
2254
836
17.2
6.3
1145
743
0.04
0.04
0.16
0.71
0.67
0.11
0.16
0.002
Percentage
Removal
71.1
44.7
94.6
94.3
71.6
41.9
62.0
82.7
73.7
99.4
8.3
14.8
33-3
75.0
25.0
99.3
24.1
64.6
95.3
33.3
* 1_. . C I JJ. J. .... ...
This system consists of lime addition, sedimentation, air stripping, neutralization, nutrient supplementation
and activated sludge.
**mg/l
-------
operator can control pH as a method of differentially affecting
effluent heavy metals concentration.
The results observed with phosphates and sulfates should be noted.
The concentration of phosphates and sulfates Increase during the course
of treatment because of the addition of sulfuric and phosphoric acids
as neutralizing agents. Initially, both acids were used In excess in
order to encourage the growth of the activated sludge microorganisms.
That is, the goal was to provide a very favorable environment in terms
of both pH and the nutrient phosphorus,- However, following the
successful acclimation of the activated sludge, the addition of sulfuric
acid practically stopped while that of the phosphoric acid was
drastically cut back. Neutralization was not needed because of the
recarbonation effect of aeration in the lagoon. The final criterion
for phosphoric acid addition was to provide just enough to satisfy
the microorganisms' demand as indicated by an effluent concentration of
about 1 mg/Uter. That is, the criterion was to add enough H-PO, so
that there is residual phosphorus (l mg/llter) in the effluent. This
level is one to two orders of magnitude greater than the amount In
the lime clarifier effluent.
The difficulties in obtaining a healthy culture of activated sludge
were overcome. The operating experience indicated that the earlier
problems were in fact due to ammonia toxicity and phosphorus limitation.
The ammonia stripping lagoon maintained the concentration of this
Inhibitor below toxic levels. The mean and standard deviation of the
lagoon effluent ammonia concentration were such that 95 percent of the
-64-
-------
time, the feed to the activated sludge unit was less than 423 mg
NH,-N/liter. The corresponding raw leachate concentration was 1072
mg NH--N/1iter. (Similar results were obtained during the other test
period. Pooling all the data, the -1 standard deviation interval for
the lagoon effluent was 203 to 6k] mg per liter, whereas, for the raw
leachate, the mean was 1,001 mg NH,"N per liter and the standard
deviation, 1049 mg per liter.) Thus, the lagoon functioned to minimize
the shock loading effect of inhibitory ammonia concentrations. This in
turn provided an opportunity for the development of microorganisms
capable of extracting carbonaceous BOD, As this group became established,
organic concentrations in the mixed liquor were reduced and this created
conditions suitable for the development of nitrifying organisms. Growth
of these groups of microorganisms has resulted in the low effluent
concentrations of both BOD and ammonia.
As seen in Table 14, a considerable change in alkalinity occurs
during biological treatment. There are two main mechanisms by which
this occurs. First, the aeration causes some removal of gaseous
carbon dioxide, resulting in a shift of the carbonate equilibria and a
change in total bicarbonate alkalinity, |t is probable, however, that
in this case, nitrification has a more profound errect on alkalinity.
As a result of nitrification, alkalinity is consumed and carbon dioxide
is produced. Neglecting the effect of bipmass synthesis, the
theoretical value is 7.14 mg alkalinity as CaCO, destroyed per mg
NH.-N oxidized. In this study a ratio of 4,46 mg alkalinity per mg
NHi-N removed was observed after the development of the activated sludge
culture. This is in excellent agreement with the theoretical value if
-65-
-------
one considers that the observed value Includes the effects of bfomass
growth and ammonia stripping in the bio-units as well as shifting
chemical equilibria in addition to those of nitrification. These
conclusions are drawn from the data presented in Tables 15 (Column 7)
and 20 (Column 12) which represent activated sludge effluent and
influent values, respectively.
System 1 was re-tested from January 1, 1978 through August 31, 1978,
following completion of the equalization pond. Cold weather, the extreme
strength of the process influent, and the high flows Inhibited
development of an activated sludge until April, 1978. The sludge did not
become acclimated until July 1, 1978, following a process change from
parallel to series deployment of the aeration tank-secondary clarifler
system. A schematic ?s shown in Figure 7. The change was undertaken
in an effort to gain greater use of the available aeration capacity.
This was deemed necessary because of the tremendous process loadings
observed in 1978 (Table 35).
The acclimated activated sludge performed well. The average flow
into the biological- units was 10,000 gpd, whereas, during the same
period, the raw leachate flow was 50,000 gpd. The difference Is due
to the extreme strength of the leachate which inhibited the activated
sludge so that only a portion of the flow could be treated biologically,
(The entire flow was treated in the chemical/physical section of the
plant during this period.)
The data for the re-test of System 1 are presented in Table ]k,
and a summary of both tests appears in Table 15, The results Indicate
-66-
-------
FIGURE 7. FLOW CHART FOR ACTIVATED SLUDGE IN SERIES
I
ON
AMMONIA
LAGOON
ACTIVATED
SLUDGE
UNIT #1
CLARIFIER
#1
ACTIVATED
SLUDGE
UNIT #2
ฃLARIplER
#2 X- ,
EFFLUENT
-I
SLUDGE
I
SLUDGE
-------
oo
i
TABLE 15
SUMMARY OF SYSTEM 1 OPERATION
(8/1/76 to 4/30/77 and 4/1/78 to 8/31/78)
Alkalinity, as CaCO.
Ammonia-N
BOD
Cadmium
Ca 1 c i urn
Chloride
Chromium
COD
Copper
Dissolved Sol ids
Hardness, as CaCO-
Iron *
Kjeldahl-N
Lead
Magnesium
Mercury (ppb)
Nickel
PH
Phosphate
Potassium
Sod i urn
Sulfate
Suspended Solids
Zinc
51*50
758
11886
0
888
4161
0
18490
0
13516
5054
333
748
0
465
5
1
6
2
903
1301
577
555
19
.*
X
.078
.26
.40
.74
.52
.76
.74
.05
.5
Raw
cv
0.26
0.32
0.78
0.91
0.57
0.23
0.77
0.71
1.06
0.63
0.49
0.85
0.25
0.80
0.34
1.15
1.13
1.32
0.63
0.20
0.29
2.77
1.46
1.14
n
53
56
52
54
54
53
54
172
53
171
51
52
44
54
54
48
55
197
53
47
53
48
167
52
X
1878
350
3930
0.025
293
2616
0.07
6892
0.31
5995
1211
3.24
294
0.17
107
3.95
0.61
8.60
0.12
514
785
363
193
0.63
Lagoon
cv
0.43
0.05
0.63
1.37
0.61
0.08
1.19
0.57
1.33
0.30
0.54
1.00
0.24
0.74
0.45
1.29
1.18
1.09
3.89
0.22
0.38
0.68
1.13
1.69
n
44
53
46
45
44
43
44
165
48
175
38
42
35
44
43
38
43
181
43
38
43
41
165
44
X
803
75
153
0.017
314
2544
0.07
945
0.11
5824
1327
2.71
102
0.12
107
4.01
0.75
7.61
14.1
535
862
937
133
0.53
Effluent
cv
1.02
1.01
1.75
1.64
0.52
0.33
0.59
0.80
0.44
0.25
0.55
1.04
1.46
0.65
0.36
2.70
0.78
__
0.50
0.15
0.39
0.76
1.42
1.15
n
48
74
69
55
57
57
66
223
56
213
54
70
49
69
57
61
56
237
66
50
56
55
209
70
Percent
Removal
85.2
90.1
98.7
78.2
64.6
38.9
73.1
94.9
72.5
56.9
73.7
99.2
86.4
83.8
72.0
27. 4
57.4
__
40.8
33.7
76-. 0
97.3
vt-
x
mean, mg per 1iter
cv = coefficient of variation
n = number of data points
-------
that System 1 Is able to handle large loading rates, and to achieve
high removal efficiencies. Data collected during the warm weather
months (August 1, 1976 to December 1, J976 and July 1, 1978 to August
31, 1978) have been analyzed separately.- These data show that System 1
can produce an effluent of sufficient quality to meet the final effluent
criteria (Table 16),
Approximately equivalent results are obtained using the biological
reactors in either the parallei (1976"77) or the series (1978) mode
(Table 17). In terms of percent removal efficiency, the series and
parallel operations provided approximately equal performance with
respect to BOD and COD. Removals of ammonia-N were much greater with
the series operation. This is due to the localization of NhV-N removal
in the second tank following BOD oxidation fn the first, (Note that the
average flow during the series test was 10010 gpd, whereas during the
parallel test, the flow was 21034 gpd (Table 14),
Operational Comments. Operating problems were encountered In the
biological treatment unit. The most serious of these was a tendency of
solids to float in the secondary clarifier. The result of this has been
a decreased ability to achieve the expected level of solids separation.
The presence of the floating sludge has been investigated and is
characterized as being the result of three separate and distinct causes;
flotation, turbulence and denitrification. It was apparent that there
was some carryover of floating materials to the clarifier from the
aeration tank. The leachate contains considerable amounts of surface
active materials capable of flotation, and this contributes significantly
-69-
-------
TABLE 16
WARM WEATHER OPERATION OF SYSTEM 1
Parameter
Ammonla-N
BOD
Cadmium
Chromium
Copper
Iron
Lead
Mercury
Zinc
Effluent Concentration
8.7
75.8
0.02
0.06
0.10
1.22
0.11
0.0045
0.37
Permit Standard
35.0
100.0
0.02
0.10
0,20
7.0
0.10
0.01
0.60
Time periods included are 8/1/76 to 12/1/76 and 7/1/78 to 8/31/76.
All units are mg per liter.
-70-
-------
I
-J
TABLE 17
COMPARISON OF SERIES AND PARALLEL OPERATION OF ACTIVATED SLUDGE UNITS
Parallel Operation
(8/1/76 - 5/1/77)
Parameter
Alka Unity, as CaCO-
Ammonia-N
BOD-5
Cadmium
Calcium
Chloride
Chromium
COD
Copper
Dissolved sol ids
Hardness, as CaCO-
Iron *
Kjeldahl-N
Lead
Magnes i urn
Mercury
Nickel
Phosphates
Potassium
Sodium
Sulfate
Suspended sol ids
Zinc
*mg/ liter
a.
Influent
1604
286
356k
0.021
308
2508
0.08
6481
0.34
5710
1242
3.6
294
0.18
105
0.004
0.61
0.041
487
712
384
147
0.72
ซ
Effluent
685
80
118
0.01
347
2592
0.07
939
0.1
5697
1314
3.0
102
0.12
107
0.004
0.76
13.7
524
821
951
101
0.57
Remova 1
Efficiency
57.3
72.0
96.7
52.4
-12.7
-3.3
12.5
85.5
70.6
0.3
-5.8
16.7
65.3
33.3
-1.9
0.0
-24.6
-7.6
-15.3
31.3
20.8
Series Operation
(7/1/78 - 8/31/78)
n
Influent
3127
738
5966
0.04
227
2933
0.06
9873
0.16
8635
1007
1.85
0.12
116
0.003
0.62
0.53
743
1160
258
663
0.24
JL
Effluent
1496
6.3
464
0.04
113
2254
0.04
1088
0.16
7244
1456
0.71
0.11
105
0.002
0.67
17.2
743
1145
836
478
0.16
Remova 1
Efficiency
52.2
99.1
92.2
0.0
50.2
23.2
33.3
89.0
0.0
16.1
-44.6
61.6
8.3
8.7
33.3
-8.1
0.0
1.3
27.9
33.3
-------
to the carryover phenomenon,. The original scum control device was not
capable of handling the unexpectedly large amount of these materials.
At the same time, an excessive amount.of turbulence existed in the
secondary clarifier.
The reduction of solids separation efficiency was compounded by a
propensity of the activated sludge to become anaerobic and to rise in
the clarifier due to denitrification. This is seen clearly when one
follows closely the settleable solids test. At first, the sludge
settles properly with a dense sludge layer overlain by a clear
supernatant containing little turbidity, so that at the end of 30 to 45
minutes the settleable solids are about 300 mg/liter. If the test is
continued for another hour, the sludge comes to the surface in typical
rising sludge fashion. This is not a case of filamentous bulking as
indicated by microscopic examination, the clear supernatant observed
in the settleable solids test, and the sludge volume index of approximately
80 ml/g. Another indication of anaerobic denitrification as the cause
of the floating sludge is the repeated observation of very low DO levels
in the clarifier. This problem was accentuated when a portion of the
plant aeration capacity was diverted to the ammonia-stripping lagoon.
These problems were resolved by minor design and operational changes.
The installation of a more efficient scum removal system has ameliorated
the floating sludge problem. Additional baffles were used to control
the turbulence in the clarifier. Extra aeration capacity was installed
to maintain appropriate concentrations of dissolved oxygen,
Cost'Data. Costs incurred during the operation of the biological
t
units are indicated in Table 18. The operation and maintenance costs
-72-
-------
TABLE 18
OPERATION AND MAINTENANCE COSTS INCURRED DURING THE OPERATION OF SYSTEM 1
, FOLLOWING ACCLIMATION OF ACTIVATED SLUDGE
(8/1/76 to 5/1/77 and 7/1/78 to 8/31/78)
Characteristics
Total Flow, gal
cu m
Lime, Ib
lb/1000 gal
kg/ cu m
Sulfuric acid, gal
gal/1000 gal
1 i ter/cu m
Phosphoric acid, gal
gal/1000 gal
NaOH, gal
gal/1000 gal
1 i ter/cu m
NaOCl, gal
gal/1000 gal
1 i ter/cu m
8/1/76- 5/1/77
5332635
20186
132600
24.9
3.0
407
0.076
0.076
80.25
0.015
733
0.137
0.137
571.5
0.107
0.107
7/1/78 - 8/31/78 Total
620620*
2368
84300
27.2
3.3
380
0.122
0.122
35
0.011
0
0
0
330
0.532
0.532
5953255
22554
216900
25.7
3.1
787
0.093
0.093
115.25
0.014
733
0.123
0.123
901.5
0.151
-0.151
Costs, $/1000 gal
Power
Lime
HjPOj,
NaOH
NaCl
Total
1.92
0.75
0.06
0.04
0.09
0.08
2.94
1.92
0.82
0.10
03
40
3.27
1.92
0.77
Q.07
0.04
0.08
0.11
2.99
During this time period, the average flow through the chemical/physical section of the plant
was 50,000 gpd.^whereas that through the biological units was 10,010 gpd. The dosages in this table
reflect these different flows.
-------
are shown for the operational periods following-acclimation: August 1,
1976 to May 1, 1977 and July 1, 197B to August 31, 1978. The costs
Include those for NaOH, added to the ammonia lagoon to enhance ammonia
stripping, and NaOCl, added to the final effluent to provide disinfection
prior to discharge and to provide ammonia oxidation during the cold
months.
>
The data Indicate a cost of $2,99 per thousand gallons treated.
The high power costs reflect the demand for electricity for leachate
pumping, effluent pumping, and maintenance of the laboratory in addition
to the requirements for actual treatment.
The costs during the re-test of System 1 warrant discussion. During
this period, the flow through the System 2 section of the plant was
approximately 50,000gpd, while the flow through the activated sludge
units was 10,010 gpd. The dosages of chemicals and the costs of treatment
shown in Table 18 take account of these differences. Thus the dosage
for lime is based on 50,000 gpd, whereas that for NaOCl is based on 10,010
gpd. The costs during the re-test are somewhat higher than anticipated.
This results from two causes. First, the final effluent was chlorinated
during the entire 1978 test period prior to land disposal, The effluent
was chlorinated for a relatively small portion of the time during the
earlier test. The second reason is that lime and sulfuric acid dosages
were greater during the re-test. This was because more lime was added
to enhance ammonia removals in the ammonia lagoon, and, as a consequence,
sulfuric acid dosages were also high. The labor requirement is
approximately 20 man-hours per week,
-Ik-
-------
Nitrification
Nitrification is becoming a standard and widely used wastewater
treatment process. It is the aerobic microbiological conversion of
ammonia nitrogen to nitrate nitrogen. As such, nitrification is
applied In situations where the pollution potential of ammonia is
severe, especially in comparison with nitrate nitrogen. The adverse
impacts associated with high concentrations of ammonia are promotion
of eutrophication; toxicity, especially as a function of pH, to aquatic
organisms; Interference with chlorinatlon due to reactions leading to
the formation of chloramines; and, depletion of dissolved oxygen fn
receiving streams concomitant with the oxidation of ammonia to nitrate,
As a result of considerations such as these, effluent ammonia standards
are often established by regulatory agencies,
The nitrifying bacteria, typified by Nitrosomanas and Nitrobacter,
oxidize ammonia to nitrite and nitrite to nitrate, respectively. These
microorganisms are chemoautotrophs, and the nitrogen oxidation reactions
provide the bacteria with a source of energy. A stoichiometric
relationship can be written for the overall synthesis of biomass and
56
oxidation of ammonia and nitrite as follows:
NH4+ +1.83
1.88 H2C03
1.98 HC0
0.020
1.041
0.98 N0
(1)
Nitrifying bacterial biomass is represented as C,-H7N02. Eqn (1)
indicates that the theoretical cellular yield is 0.16 g biomass per g
NH.-N completely oxidized, (Also evident from Eqn (l) is the destruction
of 7.1 g alkalinity per g NH.-N oxidized, as discussed previously,)
-75-
-------
Much of the literature concerned with waste treatment applications
of nitrification has been devoted to municipal sewage. A recently
published design manual has summarized this literature. The ammonia
content of municipal sewage is characteristically on the order of twenty
to forty mg per liter. Occasionally, however, industrial wastes with
rQ ฃ1
much higher concentrations are encountered, |n this section of
the report, dqta are presented gnd discussed showing that nitrification
is inhibited at high substrate concentrations. Substrate inhibition
such as described herein must be considered during both the design and
operation of biological treatment plants intended for nitrification.
Boon and Laudelot have investigated the nitrite oxidizing bacterium,
62
Nitrobacter winogradskyi. They have shown that the rate of nitrite
oxidation,which is inhibited by nitrite, is a function of the nitrite
concentration which can be expressed as
(2)
1
-1
where y is the specificgrowth rate, time ; y, the maximum specific
growth rate in the absence of inhibition, time ; S, the limiting
substrate concentration, mass per unit volume; K , saturation constant,
numerically equal to the lowest concentration of substrate at which y
A,
is one-half of y, mass per unit volume; K., inhibition constant,
numerically equal to the highest concentration of substrate at which
A
y is one-half of y, mass per unit volume.
The assumption of neglecting substrate inhibition Is not particularly
misleading at low substrate concentrations. This is because the third
-76-
-------
term in the denominator of Eqn (2) becomes much less than the second
term. As a result, as the value of 5 is reduced, Eqn (2) approaches
the more conventional Monod expression
TJL_ {3)
3
This equation is a reasonable description of nitrification at low values
of S, as are encountered in municipal sewage treatment applications.
Equation (2) becomes increasingly invalid as S increases, as in the
treatment of leachate. The purpose of this section is to consider
nitrification at high ammonia concentrations, and to discuss the results
in terms of designing and operating nitrification and leachate treatment
faci1ities.
The data were collected during the period August 1, 1976 to May 1,
1977. The fraction of nitrifying bacteria in the biomass has been
calculated directly from the amounts of BOD and NH.-N oxidized, and from
the estimated yields of the two groups of oxidizers. The assumed yield
values are 0.15 g biomass per g nitrogen oxidized-day, and 0.55 g biomass
per g BOD oxidized-day.
More detailed results of the removal of ammonia in the bio-units
are given in Table 19. The concentration of NH.-N is calculated from
the equation,
H_0 NH^ + H20
using the observed temperature to determine the equilibrium constant,
the observed pH and the analytical results of the sum of NH.-N plus
NH -N (denoted as NT in Table 19). Three removals are given in Table 19
-77-
-------
TABLE 19
AMMONIA REMOVAL IN ACTIVATED SLUDGE UNITS*
00
I
Date Influent Data
NT
5/27/76 549
6/10 241
6/1 it 277
6/22 283
6/30 325
7/15 308
7/21 350
7/27 290
8/3 322
8/10 255
8/20 305
8/23 364
8/24 364
8/25 364
8/26 360
8/27 356
8/28
8/29
8/30
9/3 369
9/10 302
9/13 364
9/15 364
9/23 322
BOD
2020
i.
2970
3550
3670
2499
2049
2555
1763
1949
2760
3780
2905
2637
COC
4863
_*_
4961
4047
4351
3984
3915
3960
3672
3621
4843
5078
5175
5080
5039
3347
5118
5381
4220
5061
6370
5118
4264
Temp.
24.6
?<; n
t-J * V
25.2
26.0
25.0
26.3
26.5
27.1
24.5
26.5 .
24.5
28.8
27.5
24.4
26.5
26.5
28.2
27-3
24.5
21.3
20.8
23.7
22.0
24.5
NT
. 736
___
496
392
330
367
302
261
297
161
36
15
10
14
17
6
1.
1.
1.
1.
2.
8.
3.
6.
Bio-Reactor
NH4+-N
._
...
35
14
2
5
5
9 1.9
7 2.6
8
6 3.5
0 5.8
Data
PH
8.04
7.59
7.37
7.80
7.36
7.57
7.34
7.74
7.42
7.45
7.43
7.31
7.35
7.42
7.22
7.82
7.59
7.3
7.7
7.5
7.6
7.7
BOD
2980
2325
2200
3710
1152
180
1181
111
30
48
12
36
27
24
14
35
25
35
43
310
37
123
COD
9725
4186
1556
4656
717
775
3280
664
621
768
406
420
384
526
474
299
396
565
546
1053
710
599
620
Remova 1 s
"I
0
0
0
0
0
.14
.10
.08
.37
.88
.96
.96
.96
.95
.98
...
.99
.99
.98
.99
.98
R3
.61
.63
.53
.50
.92
"4
.026
.012
.015
.022
.036
.
NT refers to the analytically determined value of NHj,-N plus NHj, whereas NH/,-N is the calculated
ammonia concentration. R| is the removal of NT based on influent and effluent concentrations, R2 is the
fraction of NT oxidized, and R3 is the specific oxidation rate, g NT oxidized/g biomass-day. Units are
mg per liter unless otherwise noted.
-------
TABLE 19 (Cent.)
Date
9/29/76
10/7
10/13
10/19
10/28
11/3
11/13
11/18
11/23
11/24
12/2
12/4
12/6
12/11
12/13
12/14
12/22
12/27
1/4/77
1/10
1/12
1/14
1/24
1/25
2/1
2/9
2/17
2/23
3/2
3/3
3/10
3/17
3/24
3/30
4/6
4/14
4/21
Influent Data
NT
367
255
218
240
227
235
275
296
319
319
400
342
353
361
442
308
251
233
232
231
230
176
162
164
244
283
160
289
316
296
255
247
246
BOD
2660
1788
1590
1850
1750
1830
1880
2730
3020
6630
4435
3885
1630
1620
1725
1570
1490
1906
5360
9870
8990
9750
9440
2560
4090
5010
COD
4360
3068
2-791
3310
3170
3454
3262
3461
5910
6423
6902
8055
8716
9154
8550
9077
7116
7871
6798
3152
3178
2675
2936
2761
2526
2557
8635
15271
16351
1,5683
15895
3881
6853
8651
Temp.
22.7
23.2
18.9
15.5
12.5
14.7
11.2
12.2
10.2
12.9
6.9
4.4
4.2
11.0
8.0
3.2
4.1
3.0
5.0
4.0
3.0
0.0
0
0
1.0
3.0
6.6
9.0
11.3
12.3
15.5
12.6
5.8
11.0
15.0
15.0
20.9
Bio-Reactor Data
NT
i.
13.
5.
5.
1.
3.
3.
110
63
65
7*(
33
123
95
30
15
83
185
151
161
145
146
151
144
156
153
165
174
140
195
196
202
187
164
i
NH^-N pH
5 1.5 '7.6
2 12.9 7.5
2 5.2 7-0
8 5.7 7.4
0 1.0 7.6
4 3.4 7.6
2 3.2 7.4
109 7.6
58 8.6
8.5
71 8.4
8.4
8.4
7.9
7.9
10 7.8
83 7.2
8.0
143 8.6
8.4
8.5
139 8.6
140 8.6
145 8.6
140 8.4
151 8.3
149 8.1
162 7.8
170 7.9
135 8.0
183 8.3
7.9
188 8.2
197 7.9
184 7.7
154 8.1
BOD
83
31
52
46
53
39
29
97
78
38
19
100
61
25
37
43
47
86
84
94
666
587
834
478
983
364
686
COD
581
299
271
295
268
321
286
296
400
382
392
501
. 564
518
398
410
645
864
2830
730
582
560
550
538
586
565
917
1559
2321
3842
1713
2560
1820
1787
Removals
Rl
.99
.95
.98
.98
.99
.99
.99
.63
.80
.77
.69
.91
.96
.77
.66
.48
.38
.37
.34
.18
.04
.07
.32
.39
.13
.33
.34
.21
.24
.33
R3
.52
.57
.43
.27
.65
.48
.35
..52
.50
.70
.34
r
.38
.17
.09
0
0
0
.15
.05
.12
.33
.14
.19
.28
R4
.013
.019
.014
.007
.022
.011
.010
.015
.015
.020
.008
.006
.001
.001
0
0
'o
.0.15
'.0.08
0.45
0.98
0.08
.68
.68
-------
The first, R., is the percent removal efficiency based on influent and
effluent concentrations; the second, R2, is the fraction of N_ which
is oxidized in the aeration tank; and R-, is the specific oxidation
rate. The units of R, are g nitrogen oxidized per g biomass-day, and
it is calculated as the daily mass of nitrogen oxidized divided by the
biomass. R, is determined using the fraction of nitrifiers in the
biological solids, expressed as volatile suspended solids.
As indicated in Table 19 the overall removal of ammonia in the
activated sludge units was considerable. Although this Is primarily
due to the microbial process of nitrification, the physical stripping
of ammonia caused by aeration accounts for some or the removal. It Is
the purpose of this discussion to consider the fgctors affecting the
ammonia converted by nitrification. It is apparent from Table 19 that
a profound inhibitory effect was placed on the specific oxidation rate.
as a result of extreme winter temperatures. Since the result was to
decimate the nitrifying population, the following discussion is limited
to the data obtained up to 25 January 1977. Data are not included from
the third year of operation because of changes in flow rates and loading
rates.
No simple pattern could be perceived which related nitrification
measured as the specific oxidation rate (R-, Table 19) with the
concentration of organic matter. Nitrification did not occur when the
reactor BOD,, exceeded one gram per liter and when the COD exceeded three
grams per liter. However, subsequent to the formation of a culture of
acclimated activated sludge, capable of nitrification and organics
oxidation, there was no consistent relationship between the specific
-80-
-------
oxidation rate and the concentration of organic matter in the reactor,
Nitrification proceeded even though the activated sludge Influent
concentration of BQD_ and COD averaged 3564 and 648] mg per liter,
respectively. This was true when the ammonia content of the bio-un?t
influent did not exceed 300 mg per liter. At higher ammonia levels,
the toxicity of aromonig predominated and very little oxidation of either
organics or ammonia occurred.
It is reasonable to expect some inhibition due to the elevated
levels of BOD,, and COD recorded in Table 19, The nitrlfers, such as
NItrosomonas and N|trobacter, are chemolJthotrophs, i.e., they are
autotrophs, and their carbon source is Inorganic. These bacteria are
especially sensitive to organics In pure culture. Certain heterotrophlc
bacteria, fungi, and actinomycetes are capable of performing
nitrification, ' although it is generally believed that the rate
of heterotrophic nitrification is much less than that of the autotrophic
nitrifiers. The sensitivity of these organisms to organics is
presumably much less than it is for the autotrophs. Wild et al.
observed no effect of BOD, in the range of 5"!10 mg per liter, on the
rate of nitrification in activated sludge processes.
The effect of temperature on the specific oxidation rate Is shown
in Figure 8. This curve agrees well with curves developed and presented
68
recently by the Environmental Protection Agency. The curve has been
fitted in the least squares sense and the equation of the line is
R3 P. Xe"E/RT (5)
-81-
-------
oo
to
i
FIGURE 8. EFFECT OF TEMPERATURE ON SPECIFIC OXIDATION
RATE. THE LEAST SQUARES LINE OF BEST FIT
SHOWN. THE NOTATION 1 REFERS TO TEMPERATURE, K:
AND R IS SPECIFIC OXIDATION RATE.
R,ซ 2.1754 * 109,xp |- I2347/I.99T)
10 20
Tempergture, K
-------
"
where, R, * specific oxidation rate, day
9 ' "1
2,175 x 10 .day s Arrhehiu
activation energy * 123^7 cal/mple
9 ' "1
X =f 2,175 x 10 .day s Arrhehius frequency factor
R s gas constant ป 1 ,99 cal/mole"K
T = temperature, K
The curve of Figure 8 is somewhat lower than the theoretical one
developed by the EPA, and this is most likely due to an inhibitory
effect of some wastewater fraction such as heavy metals, organ fcs, and
substrate.
A number of values for E have been reported in the 1 iterature.
Wong-Chong and Loehr presented data showing the variation of E with
pH.' Their results indicated that for the ammonia oxidation, the value
of E ranges from 16 to 21.6 K cal per g mole, Sutton et/a_l_. state that
E is a function of the treatment mode, and in particular of the staging
of the biological units, and the sol ids retention time. For single
stage units, such as this one (August 1 , 1976 - May 1, 1977), they report
that the values of E are 25.1, 21.25, and 11,9 k cal/g mole for solids
retention times (SRT) of 4, 7, and 10 days, respectively. The figures
refer to the overall nitrification process. The last number is of
particular importance since an SRT of ten days is considered to be the
minimum needed for thorough nitrification7 (although Hutton and LaRocca7
7k
considered thirty days to be more reasonable, and others consider three
to four days as the minimum needed to ensure successful nitrification).
The value of 12350 cal per g mole obtained here is in good agreement with
that of Sutton et al.
-83-
-------
A number of factors were Investigated for potential Inhibition of
nitrification. As discussed above, there Is no consistent observed
effect of organic matter, measured as BOD,, and COD, on nitrification.
However, based on the literature. It Is probable that some of the
Inhibition noted above results from the relatively high BOD and COD
concentrations in the aeration tanki The heavy metals are another
likely source of inhibition, although an obvious relationship was not
observed. Average heavy metals concentrations in the aeration tank
are listed in Tables 14 and 15 as effluent values.
The clearest reason for the observed inhibition is that increasing
concentrations of substrate are the cause. This is shown in Figure 9,
where the data show a reasonable fit to the classic substrate inhibition
model. The model is based on the Haldane mechanism for the substrate
inhibition of enzymes, and is expressed here as
1 * Ks * S
S K,
(6)
where R_ is the specific oxidation rate, day " ; R_ is the maximum
specific oxidation rate which would be obtained in the absence of
substrate inhibition, day~ ; K is the saturation constant; and, K, is
the inhibition constant. Kg and K, are numerically equal to the higher
and lower substrate concentrations, respectively, at which R, equals
A
one-half of R,.
The curve in Figure 9 has been developed using a quasiซleast squares
procedure and LIneweaver-Burke plots to evaluate the kinetic constants,
-84-
-------
3r-
I
CO
vn
FIGURE 9. SUBSTRATE INHIBITION OF NITRIFICATION.
R IS THE SPECIFIC OXIDATION RATE
U4 -i-
S 36
200
NH^-N, mg/1iter
-------
The equation used to generate the line Is
3,50
(7)
Indicating that the value of R. Is 3.5 day , Kg is 4.0 mg per liter,
and K. Is 36 mg per liter.
Figure 10 shows a Michaelis-Menton plot of the data obtained at
the lower concentrations. These values correspond to the situation
encountered in the treatment of domestic sewage, and this figure therefore
78
resembles the type curve usually presented,7 In the treatment of
Industrial wastes where the Influent ammonia-N may be much higher, it
will be necessary to consider the substrate inhibition of nitrification.
It should be mentioned that the nature of the situation, I.e., a full
scale plant treating a variable Influent, with differences in pH,
temperature, and other operating variables, contributes to the scatter
of the data observed in Figures 9 and 10,
In the excellent review prepared by Focht and Chang, much of the
79
literature regarding nitrification has been summarized. They report
that the saturation constant for the Michaelis-Menton model Is In the
range of one to ten mg N per liter for ammonium oxidation, and five to
nine mg N per liter for the conversion of nitrite. Poduska and Andrews
state that the saturation constants for N11 ro somona s and N11 r6bac te r
are approximately one mg per liter for full scale activated sludge
systems. The value of four mg N per 11ter reported here Is consistent
with these data.
-86-
-------
i
00
FIGURE 10, EFFECT OF LOW CONCENTRATIONS OF
SUBSTRATE ON SPECIFIC OXIDATION
RATE (R )
+ 20
NH.-N, mg/llter
30
-------
Focht and Chang also state.that the fIrst observation of substrate
Inhibition in nitrification was made in tne early studies of Meyerhof
who showed that Nitrosomonas and Nitrobacter are inhibited at
concentrations of NH.-N and NOj-N exceeding 60 and 350 mg per liter,
8l
respectively. Wild ฃฃฃ]_. found no evidence for inhibition due to
82
ammonia in the range of six to sixty mg per liter. Focht and Chang
also point out that end product inhibition has been demonstrated with
83
both Nitrosomonas and Nitrobaeter, This refers to the situation in
which accumulated nitrate or nitrite inhibits further nitrification,
A number of Investigators have reported that inhibition of
OJ. OO
nitrification is due to ammon!a-N and to unionized nitrous acid,
Verstraete eฃ a\_. recommend that startup of nitrification units treating
highly nitrogenous wastes must consist of a gradual increase in the
nitrogen loading In order to avoid the deleterious effects of these
89
undissoctated species of nitrogen. The data shown in Table 19 have
been examined in this light in order to assess nitrification inhibition
which could be attributed to the free ammonia concentration. When
this is done, however, it is observed that there is no relationship
between the specific oxidation rate and the concentration of free
ammonia. In this respect, the results of this study are In conflict
with those cited above, and the question merits further study,
Kholdebarin and Oertli have reported recently their studies of
90 4>
batch growth nitrification. They observed that the Ionized NhV-N has
a stimulating effect on nitrite oxidation, |n the present study,
NH.-N was observed to exert an inhibitory effect. As shown in Figure 9,
-88-
-------
the effect is not profound until the concentration exceeds ten to
twenty mg NHj^-N per liter. The ammonium ion levels used by Kholdebarin
and Oertli were 2,8 mg N per liter, and in one experiement, 28 mg N per
liter. Thus, assuming that Nt^-N inhibits nitrification, the
experiments of Kholdebarin and Qertlj must be performed at higher
concentrations in order to be comparable with the results presented here.
The approach which has been tollowed here has been to attempt to
simplify an exceedingly complex mjcrobial process. The conversion of
ammonia has been considered the rate limiting step, and has received
primary attention. The maximum growth rate of Nltrobacter is larger
than that of Nitrosomonas and the value of the saturation constants
is approximately the same. Thus, nitrite is oxidized more quickly than
is the ammonia, and this forms the basis of the above assumption.
Certain aspects of the inhibition of nitrification have not been
considered. Examples are product inhibition due to nitrite and nitrate,
and the non-competitive inhibitory effect of nitrous acid. A third area
of simplification is that the environmental factors are quite variable
at the leachate treatment plant, due to influent quality and quantity
changes.
It is contended that this approach Is justified because of the
complexity of full-scale operation. The value is that nitrification is
viewed from the overall perspective, and it is seen that substrate
inhibition is a phenomenon operating fn this system. This knowledge can
serve as a gu(ae ?n both the design and operation of nitrification
QO
systems, and can ultimately be incorporated within steady-state and
93
dynamic models of the process,
-89-
-------
Summary. The rate of nitrification, as expressed as the specific
oxidation rate, follows the van't-Hoff Arrhenius relationship which
indicates that the activation energy Is approximately 12350 cal per mole,
9 ~1
and that the Arrhenius frequency factor is 2,18 x 10 day . The data
Indicate that substrate inhibition due to ammonium ion concentration
occurs In this system. This relationship has been expressed as a
Haldane inhibition model in which the maximum specific oxidation rate
is 3.5 g N oxidized per g biomass day, K Is 4 mg per liter, and KI is
36 mg per 1Iter.
System 2. Chemical/Physical Treatment
This discussion is presented In two parts. The first consists of
the results associated only with lime treatment, and the second includes
the ammonia stripping lagoon. Full-scale data were collected for System
2a without the lagoon during the periods November 15, 1975 to January
12, 1976 and June 14, 1976 to April 30, 1977, all dates inclusive. The
\
results of this phase of the treatment plant operation are summarized
In Table 20, columns 1-7. The distinction between the two periods permits
an assessment of the performance of the ammonia lagoon.
Table 20 summarizes the changes in each parameter attributable to
the lime treatment. In very approximate terms, the 1ime precipitation/
clarification sequence, System 2a, removed (see Column 7, Table 20)
one-quarter of the nitrogen; one-third of the dissolved solids; one-half
of the organic matter, hardness and alkalinity; three-quarters of the
suspended solids; and ninety percent of the phosphates. The removal of
heavy metals was over one-half of the mercury and cadmium; two-thirds
-90-
-------
TABLE 20
SUMMARY OF SYSTEM 2 RESULTS. EACH SYSTEM CONSISTS OF LIME TREATMENT AND CLARIFICATION
., SYSTEM 2a and 2b ARE WITHOUT AND WITH AIR STRIPPING OF AMMONIA, RESPECTIVELY.*
Parameter
Alkalinity, as CaCO,
Ammonia-N
BOD-5
Cadmium
Calcium, as CaC03
Chloride
Chromium
COD
Copper
Dissolved Sol ids
Hardness, as CaC03
Iron
Kjeldahl-N
Lead
Magnesium, as CaCO?
Mercury
Nickel
PH
Phosphates
Potassium
Sod i urn
Sulfate
Suspended Sol ids
Zinc
System 2a
Influent
n
(l)
65
66
65
62
63
75
63
212
62
274
76
61
72
60
70
66
63
300
63
75
78
72
224
61
X CV
(2) (3)
5668 0.23
1167 1.25
10356 0.86
0.07 0.87
863 0.54
4590 0:43
0.25 0.75
16618 0.74
0.46 0.93
12652 0.56
5257 0.41
350 0.74
1157 1.28
0.75 0.73
562 0.42
5.69 1.30
1.58 1.21
6.80 1.28
2.40 0.63
941 0.27
1284 0.35
409 3.23
843 1.14
19 1.06
Effluent
n
(4)
43
48
46
41
43
45
43
151
52
218
49
43
50
43
43
40
43
242
42
46
48
46
183
43
X CV
(5) (6)
3052 0.30
890 1.26
5265 1.03
0.03 0.49
696 0.57
3516 0.74
0.09 0.58
7188 0.67
0.10 0.47
7972 0.32
2461 0.50
3.8 3.05
867 1.39
0.24 0.85
209 .90
2.85 1.22
.57 1.44
8.46 8.04
.26 .83
613 .36
830 .45
426 .89
239 1.15
0.61 1.35
R
(7)
46.2
23.7
49.2
57.1
19.4
23.4
64.0
56.7
78.3
37.0
53.2
98.9
25.1
68.0
62.8
49.9
63.3
89.2
34.9
35.4
-4.2
71.6
96.8
System 2b
Influent
n
(8)
79
88
77
80
80
78
80
261
79
232
76
74
61
80
80
74
81
394
84
61
78
79
255
86
X
(9)
5316
785
11668
0.086
841
3927
0.25
18566
0.43
10456
4645
300
739
0.68
421
0.021
1.60
6.93
2.52
944
1366
512
967
15.9
CV
(10)
0.78
0.31
0.71
0.82
0.57
1.49
0.71
0.62
0.94
1.04
0.49
0.82
0.27
0.76
0.42
2.43
1.06
1.56
0.75
0.21
0.30
2.46
1.11
1.15
Effluent
n
(11)
70
86
71
71
70
68
70
254
73
236
64
68
52
67
69
63
67
383
74
52
66
70
253
70
X CV
(12) (14)
2374 0.28
412 0.52
3600 0.84
0.035 1.09
424 0.70
2669 0.15
0.08 0.94
8793 0.63
0.27 1.27
4650 1.09
1587 0.53
5.61 1.28
349 0.41
0.23 1.31
117 0.62
0.0101.96
0.73 0.93
866 1.79
0.27 2.07
572 0.25
956 0.40
525 0.67
288 0.93
0.85 1.39
R
55.3
47.5
69.1
59.3
49.6
32.0
68.0
52.6
37.8
55.5
65.8
98.1
52.7
65.6
72.1
52.4
54.3
89.3
39.4
30.0
-2.6
70.2
94.6
x - mean, mg/liter. R stands for percent removal. System 2a effluent is the lagoon influent.
-------
of the chromium, nickel, and lead; three-quarters of the copper and
over ninety percent of the iron and zinc. The increase in sulfate is
due primarily to contaminants in the chemicals, although oxidation of
sulfides may contribute somewhat, in other words, this section of the
system performed as expected in pre-tfeating the leachate prior to
biological treatment.
The results of the overall chemical/physical section including the
ammonia lagoon (System 2b) are listed in Table 20 (Columns 8-1*0 which
shows the basic statistical relationships. Treatment performance in
terms of percent removal efficiency of the lagoon alone and in
conjunction with lime treatment are also seen in Table 20. The primary
goal of the lagoon was achieved as the concentration of ammonia-N was
reduced to a level which was found to be tolerable for purposes of
biological waste treatment. A splash plate, which was installed to
promote air/water contact, did not produce an appreciable effect on
lagoon ammonia removals, and was therefore removed.
Many parameters other than ammonia were altered while in the lagoon
(see Table 21). There was some stabilization of organic matter as shown
by the reductions in BOD, COD and dissolved solids. This was mediated
by biochemical processes and the increase in suspended solids is related
to the growth of microorganisms. The reduction in alkalinity is due to
aeration effects although nitrification reactions may partially contribute
to the observation. The reduction of hardness, calcium and magnesium are
related and may be explained by the formation of calcium and magnesium
carbonates. In this form, these would not be detected by the usual
tests. Most of the other changes noted in the lagoon effluent vs. lagoon
-92-
-------
TABLE 21
SUMMARY OF EFFECTS OF CHEMICAL/PHYSICAL TREATMENT*
Suspended Solids
Dissolved Sol ids
COD
BOD5
Alkal inity
Hardness
Magnes ium
Calcium
Chloride
Sulfate
Phosphate
Ammonia-N
Kjeldahl-N
Sod i um
Potassium
Cadmium
Chromium
Copper
1 ron
Nickel
Lead
Zinc
Mercury
pH
4.
Influent
1044
13029
18553
10907
5404
4652
453
818
4240
462
2.74
1001
984
1354
961
0.086
0.28
0.39
312
1.55
0.67
21
0.007
6.85
Lime Treatment
Effluent*
239
7972
7188
5265
3052
2461
209
696
3516
426
0.26
890
867
830
613
0.03
0.09
0.10
3.8
0.57
0.24
0.61
0.003
8.46
Ammon i a
Lagoon
Effluent+
288
4650
8793
3600
2374
1587
117
424
2669
525
0.27
412
349
956
572
0.04
0.08
0.27
5.6
0.73
0.23
0.85
0.010
8.66
*The influent data are those collected during the entire operational
period, whereas the effluent figures refer to those periods when the
specific units were operating.
+A11 units are mg/liter except pH which is expressed in pH units.
-93-
-------
Influent comparison are due to the.1 Imitations of the experimental
techniques or to the radically variable nature of the raw leachate.
The overall treatment efficiency .of the complete chemical/physical
section Is summarized In Table 20,. These data do not Include the effect
of neutralization. The values In the last column (Column 14) represent
removal efficiencies for the 1ime precipltation/sedimentat Ion/ammonia
stripping sequence. In terms of organic matter, 69.1 and 52.6 percent
of the BOD and COD are removed, respectively. Approximately fifty to
sixty percent of the ammonia-N, total nitrogen, suspended solids,
alkalinity and hardness are removed. The removal of metals was as
follows: 38-54 percent of copper, nickel and mercury; 59~68 percent of
chromium, cadmium, and lead; 95 percent of zinc; and 98 percent of iron.
Chlan and Dewalle have formed an hypothesis, which is summarized in
Oil
Table 6, concerning the treatability of raw leachate. The BOD/COD
ratio observed in this study (Column 2 of Table 20) of the leachate was
0.62 and the average COD was 16618 mg/liter. This is also shown in
Column 9 of Table 20, in which it is seen that the ratio is 0.63, and
the average COD, 18566 mg/liter. Thus, according to Chian and DeWalle,
the leachate treatment efficiency obtainable with lime should be fair.
In this study (Column 7, Table 20) the lime treatment efficiency for
BOD and COD has been about fifty percent. Hence, in terms of the removal
95
of organ Ics, the Chian and DeWalle hypothesis is supported. However,
It must be mentioned that their hypothesis did not include the removal
of heavy metals, and that the lime treated heavy metal removals have been
good to excellent at this facility.
-94-
-------
An additional effect of the ammonia stripping lagoon Is the
equalizing effect which, as noted by LaGrega and Keenan, can be measured
96
in terms of both flow variability and quality fluctuations. The
presence of the lagoon has allowed the operator to control the flow
leaving the lagoon by control of the pump settings. This has provided
additional flow equalization to the biological units.
Operational Comments. The primary operational factor has been the
chemicals required for precipitation and neutralization. A summary of
these is presented in Table 22. The rows labeled "average applied dose"
have been calculated by omitting those days on which chemicals could not
be added because of equipment malfunctions.
Cost Data. The cost of materials and electricity is a part of Table
22. The units are given in terms of dollars per one thousand gallons of
leachate treated. The data indicate that the cost of System 2 with, and
without, operation of the lagoon has been $2.37 and $2.35 per thousand
gallons treated, respectively. The total cost figures have been obtained
as the ratio of total costs to total volume of liquid treated. The power
costs are quite high, reflecting energy consumption not only for chemical
treatment, but also for leachate pumping, air compressors and the
laboratory. Manpower costs for operation and maintenance are approximately
twenty hours per week.
Factors Influencing Lime Treatment Performance
The principal operating characteristics of the lime treatment system
are presented in Table 23 for data collected during the period June 14,
1976 to April 21, 1977. These data only are included as this was the
-95-
-------
TABLE 22
SUMMARY OF OPERATION AMD MAINTENANCE COSTS DURING EVALUATION OF SYSTEM 2
(11/15/75-5/1/77 and 11/1/77-8/31/78)
us
During Operation
Without Lagoon
11/15/75-5/1/77
Flow,
Lime,
NaOH,
NaOCl
Costs
average gpd
Ipd
total gal
total cu m
average dose,
lb/1000 gal
kg/cu m
total Ib
kg
average dose,
gal/1000 gal
1/cu m
total gal
total liter
, average dose,
gal/1000 gal
1 cu/m
total gal
total liter
, $/1000 gaJ
Power
Lime
NaOH
NaOCl
Total
22,805
86,326
8,004,483
30,300
29.7
3.57
238,055
108,077
0
0
0
0
0
A
0
0
1.1.8
.89
0
0
2.37
Total
38,618
146,170
16, 798, 842
63,584
19,
2,
326,050
147, 894
0
0
733
2,926
0
0
901
3,413
1
0
2
During Operation with Lagoon
(Ammonia)
6/14/76-5/1/77 ฃ 11/1/77-8/31/78
.40
.33
.044
.044
.054
.054
.5
.70
.58
.03
.04
.35
6/14/76-8/1/77
21 .391!
80,987
5,348,622
20,247
36.6
4.39
195,650
88,825
0
0
733
2,926
0
0
571
2,163
1
1
0
0
2
.137
.137
.107
.107
.5
.70
.10
.09
.08
.97
1/1/77-8/31/78
17,224
65,183
11,450,220
42,337
11.
1.
130,400
59,069
0
0
0
0
0
0
330
1,250
1
0
0
0
2
39
37
.03
.03
.70
.34
.02
.06
-------
TABLE 23
SUMMARY OF OPERATIONAL DATA FOR LIME TREATMENT AND-CLARIFICATION*
--g
i
Cadmium
Date
6/14
6/22
6/30
7/15
7/21
7/27
8/3
8/10
8/20
8/25
9/3
9/15
9/23
9/29
10/7
10/19
11/13
11/18
11/23
12/14
12/22
C
.020
.028
.01
.025
.018
.020
.025
.02
.05
.05
.05
.019
.015
.017
.015
.021
.009
.012
.03
.009
.01
R
.231
.282
.700
.50
.617
.615
- .667
.091
.444
.286
.375
.525
.400
.'(52
.50
.222
.710
.707
.333
.95
.90
Chromium
C
.01*
.04
.06
.06
.06
.08
.Ok
.03
.09
.10
.09
.07
.06
.09
.05
.08
.03
.03
.11
.07
.08
R
.50
.60
.25
.684
.739
714
--
.25
.571
.286
.625
.632
.625
.654
.500
.529
.625
.667
.500
.854
.333
Copper
C
.08
.10
.09
.12
.26
.2
.01
.18
.078
.064
.10
.1
.11
.13
.05
.08
.02
.03
.01
.04
.06
R
.771
.895
.763
.90
.807
.796
.808
.926
.559
.545
.919
.931
.859
.643
.75
.90
.786
.909
.934
.455
Iron
C
.48
2.72
2.54
2.22
1.52
2.89
.1
.92
.68
.58
.85
1.09
1.15
.42
1.74
2.59
1.98
2.13
2.43
2.99
1.78
R
.994
.982
.98}
.964
.996
.995
.997
.997
.997
.997
.997
.997
.996
.999
.983
.994
.966
.981
.995
.997
.996
Lead
C
__
--
.07
.05
.07
.02
.03
.11
.04
.48
.22
.35
.-
, .
.4
.
.
t
--
.2
R
__
.873
.889
.879
.80
.864
.929
.871
.392
.728
.646
.815
.667
.20
.875
.981
.787
.333
Magnesium
C
312
312
323
87
43
36
22
123
257
250
225
45
25
54
71
92
212
136
115 -
97
101
R
.448
.525
.441
.858
.936
.860
.900
.836
,471
.520
.595
.912
.947
.894
.862
.793
.668
.809
.818
.883
.789
Mercury
C
1.17
1.06
6.5
2.96
1.72
8.5
3.1
3.4
3.5
3.
5.5
2.1
3.9
7.5
1.8
1.78
.09
.21
.15
.22
.15
R
.957
.960
.606
.80
.204
.444
.852
.364
.857
.633
.781
.074
--
.282
.930
.756
.865
.808
.934
For each chemical species, the effluent concentration (C) Is given in mg/liter except mercury (tig/liter),
pH (pH units), lime dosage (ib), Temp. (C), and flow (gpd), and R represents the fraction of material removed
by this treatment section.
-------
CM o mm UM/MAJT rno u\r*c* IAPJ eg eg CM
u\vDu\vo\or~-a-vo^r-a- CM -a- CM m tn CM O m.3
eMCMCMCMCgcMegcMCMCMCMCMCMCMCM
OOOOOOOOOOOOOO
*s22aas
in1 eg rwrrnrn'in' CAOO in-^
" """ ^ ^ *" *
ง"ซ S IN SSS i
oocr\
Q)
T3
~ o cooo i f\ tr\vO in un CT\ro en I
3-ocor~.r~.cn i o^mr~.tr\o->oieor~.<^i
, o o o eg -3* moo en o o o o o
__ _>r~.cocM-a-cMcocMinomcMoovOi
> \o eg CMCO eg CM eg eg
u> o:
u
4J
ra
jr
Q.
Ul
O
JC
0. O
cgco inclines eg r~.mtno^o^eg\o rno^^r r~.vo r~.vp
ooooooooooooooooooooo
^i- . uii.iป_f o o vo en CM in cr\ r m
-------
period of primary analysis, and also because of the change in the
!
leachate which occurred during the third year.
The function of the lime treatment/clarification section of the
plant is to pre-treat the leachate prior to biological treatment, i.e.,
to remove a portion of the organic matter and toxic substances. The
latter include ammonia as well as the heavy metals. The lime
precipitation process has consistently produced an effluent which meets
the standards except for cadmium and lead, (it should be noted that the
final effluent met these standards up to the onset of cold weather, and
that the probable mechanism for the additional removal is adsorption
onto the surface of the biological floe.) It Is apparent that,
considering the variability of the incoming waste, equalization would
improve process efficiency and effluent quality. The influent changes
occur so rapidly that the lime feed mechanism cannot maintain a constant
dose, with the result that there are occasions when the lime dosage is
inefficient and/or inadequate. As a result of this consideration, the
raw leachate equalization lagoon was constructed.
A desirable goal is to be able to operate the lime treatment process
selectively to Improve the quality of the effluent with respect to one or
more of the heavy metals. As the solubilities of the metals vary as
18
different functions of pH , it is not possible to optimize the removal
of all metals at a given pH, and the pH becomes an operational indicator
the operator can use to achieve differential removals. Thus, one can fine
tune the operation to provide an effluent of suitable characteristics.
With this goal in mind, the data of Table 23 were examined to discover a
-99-
-------
relationship between pH, temperature, and the concentration of heavy
metals In the clarjfier effluent.
In order to develop a relationship, which could be used as an
operational tool, between pH and the removal of heavy metals, the
effluent concentrations were examined as possible functions of pH.
Figures 11 and 12 show the relationship between pH and nickel and mercury
effluent concentrations, respectively, [n these figures, the circled
data points were collected when leachate temperatures were less than
16 C, whereas the others represent higher tempratures (see Figure 13).
The effects of pH and temperature on the nicKel content of the
clarffier effluent are shown in Figure 11. Process efficiency is not
a strong function of pH over the range of 8.9 to 11.7, and jt does not
matter whether one measures nickel in the effluent or the fraction
removed. Effluent concentrations of nickel centered about 0.20-0.30
mg/1 over the entire pH range, except at low temperatures. For liquid
temperatures less than 16 C, the effluent nickel level increased
substantially. This is shown In Figure 13.
Iron concentration decreased with increasing pH with the lowest
concentrations resulting at pH 10.3-12.2, The effect of low temperatures
(<16 C) was to increase the amount of iron in the clarifier effluent. In
terms of the Iron removal efficiency, the fraction of iron removed was
independent of pH and temperature, as It was always greater than 0,98.
The response of chromium, lead and phosphate to pH was more or less
flat with no apparent relationship. In each case, temperature did not
Influence the effluent concentrations. There was a tendency for lower
effluent chromium concentrations In the pH 9-10,5 range, and for better
-100-
-------
s_ i n
d) ' "-
i ^Z
0 "ฃ,
UJ
Z ;5
H
LU
_l
U.
fc -25
h
' 1 MVI >iป i i u.p | |_u
THE C
LESS "
ฎ
x x ฎ
1
8.5
9.0
EFFECT OF pH ON CLARIFIER EFFLUENT NICKEL CONCENTRATION.
THE CIRCLED VALUES REPRESENT WASTEWATER TEMPERATURES OF
x x
10.0
pH
11 .0
12.0
-------
10
FIGURE 12. EFFECT OF pH ON CLAR.IFIER EFFLUENT MERCURY CONCENTRATION.
THE CIRCLED VALUES REPRESENT WASTEWATER TEMPERATURES OF
LESS THAN 16ฐC. -
1
o
I
r 6
CTl
a:
o
LU
z:
t-
LU
LU
L
8.8 9
10
ฉ
<ฃ>
11
12
12.5
PH
-------
FIGURE 13. EFFECT OF LEACHATE. TEMPERATURE ON CLARIFIER EFFLUENT
NICKEL CONCENTRATION
1.0--
o
10
o
UJ
.-5
10 20
TEMPERATURE, K
30
-------
removals of lead at pH levels below 10.1, . However, these effects are
certainly not dramatic.
The concentration of zinc In the clarifier effluent decreased with
Increasing pH. Minimum concentrations occurred at pH 10.k to 12.2. The
effect of low temperatures was to increase the zinc content of the
effluent.
Chromium, copper and mercury concentrations show a tendency toward
a U-shaped response to pH. The curve for mercury best illustrates this
relationship and is presented in Figure 12.. For each of these metals,
the effect of low temperatures is to reduce effluent concentrations.
The best pH values for chromium, copper and mercury removal are 10.2-
11.2,' 10-11, and 9.8-10.8, respectively,
Systems 3 and k - Biological Treatment of Raw Leachate
These treatment sequences were tested in full-scale during the late
winter and early spring of 1976. Severe problems were encountered in
achieving successful treatment. The primary reason underlying these
problems was the inability to develop a healthy activated sludge.
Approximately eight weeks were allocated to attempts to adapt a sewage
activated sludge culture to the law leachate. After this did not succeed,
an investigation revealed that growth of activated sludge was not possible
because of ammonia inhibition and phosphorus limitation. The problems
were demonstrated by the observations that the average concentrations in
the biological units during this time were 9^0 mg/Hter of ammonia-N and
less than one of phosphorus. The data thus indicated that in the aeration
tanks, the ratio of BOD:N:P was 6620:760:1 which is in marked contrast
to the usual recommendations which are in the range of 90-150:5:1.
-104-
-------
The phosphorus limitation was Investigated in two ways. First,
replicate BOD tests were set up with varying additions of phosphate
buffer. It was found that the BQD_ increased with the phosphorus
addition up to an upper level, indicating that, within this range,
phosphorus was limiting. As a result of this finding, the BOD
procedure was modified by the addition of sufficient phosphorus to
overcome the limitation.
Second, a bench test was initiated to evaluate the hypothesis that
phosphorus limitation was the reason for the poor development of
activated sludge (see Table 24). The tests consisted of once daily
batch draw-and-fi]1 experiments in which the increase in settleable
solids was used to monitor the growth of activated sludge. The control
reactor received raw leachate only, whereas the sample reactor received
raw leachate plus seven ml of BOD phosphate buffer per liter of raw
leachate. Thus, in the sample reactor, the BOD:N:P ratio was about
118:13.5:1. The results are summarized in Table 24. It' is seen that
over the short-term, there was an apparent positive impact upon the
production of activated sludge and the utilization of COD. However,
when the tests were continued for several weeks, it became obvious
that there was no effect of phosphorus addition on either the development
of activated sludge or the removal of organics.
The results of these experiments have been interpreted in the
following manner. First, the biochemical oxygen demand tests, and
the chemical analyses showed that the leachate was severely phosphorus
limited. This problem became more serious when biological treatment
-105-
-------
TABLE 24
RESULTS OF BATCH DRAW-AND-FILL ACTIVATED SLUDGE EXPERIMENTS TO DETERMINE
THE EXTENT OF PHOSPHORUS LIMITATION. RESULTS SHOW GROWTH OF ACTIVATED
SLUDGE AS ML SETTLEABLE SOLIDS PER LITER, AND COD AS MG/LITER.
\*)D:N:P
time, days^
0
1
2
3
4
5
6
7
8
9
10
11
12
13
15
16
17
18
19
Control
6620:760:1
Influent effluent
COD COD SS
12813
7704
9339
--
8388 26
12868 10698 20
10193 15
11603
NR
9912
5963
9012 7115
13174
8606
8221
NR
6349
5625
Sample
118:13.5:
influent
COD
12813
7704
9339
8388
12868
10193
11603
--
9912
5963
9012
13174
8606
8221
--
6349
1
effluent
COD SS
40
7597 ^0
35
7115
5469
-106-
-------
followed lime addition because of the precipitation of calcium phosphate
salts !n that unit. Secondly, the batch draw-and-fil1 experiments showed
that alleviatlon of the phosphorus limitation alone Is not enough to
encourage the growth of activated sludge microorganisms. It was concluded
it would be necessary to reduce ammonia concentrations to a non-inhibitory
level before successful biological treatment could be achieved.
Consequently, the ammonia-stripping lagoon was started up prior to
evaluating System 1.
Systems 3 and k were re-evaluated during the spring and summer of
1977. The change-over from System 1 occurred on May 1, 1977, and data
were collected until August 31, 1977. Summaries of the operating results
for Systems 3 and k are presented in Tables 25'and 26, respectively.
System k did not operate well enough to recommend its further use.
System 3, biological treatment followed by chemical/physical
treatment, achieved very good removal efficiencies, as shown in Table 25:
approximately three-quarters or more of nitrogen, all the heavy metals,
and suspended solids; and, ninety percent or more of the organic matter.
However, as shown in Table 27, the effluent quality does not approach
' the standards placed on it, in terms of ammonia-N and organic matter.
In addition, the standard for lead has not been met with System 3. In
sharp contrast, System 1 met all standards during the warmer months of
late summer and early Fall, 1976 (see Table 16). .
System 5 - Laboratory Studies
Activated CarDon. The preliminary evaluation of this system
(System 5) has been carried out for raw leachate treatment. These data
-107-
-------
TABLE 25
SYSTEM 3 OPERATION5'
Alkalinity, as CaCOj
Ammonia-N
8005
Cadmium
Calcium
Chloride
Chromium
COD
Copper
Dissolved Sol ids
Hardness, as CaC03
I ron
Kjeldahl-N
Lead
Magnesium
Mercury
Nickel
pH
Phosphates
Potassium
Sodium
Sulfate
Suspended Sol ids
Zinc
influent
n
12
12
13
13
13
13
13
38
13
39
13 '
13
12
13
13
13
13
39
12
13
13
14
39
13
X
5087
649
12649
0.11
937
4178
0.48
21152
0.27
14742
4463
348
708
0.76
350
0.007
2.0
7-6
2.3
1076
1536
658
1136
40
cv
0.20
0.17
0.22
0.52
0.17
0.19
0.33
0.21
0.38
0.20
0.21
0.39
0.16
0.28
0.22
0.51
0.50
0.56
0.57
0.13
0.09
0.23
0.47
0.42
effluent
n
8
8
9
10
10
9
10
32
10
33
10
10
8
10
10
10
10
32
8
10
10
9
32
10
X
1178
153
763
0.02
287
1496
0.08
2257
.07
5353
924
1.02
180
0.15
48
.002
0.27
10.20
0.56
476
719
513
180
0.51
cv
0.83
0.85
1.42
1.15
0.51
0.73
0.36
1.06
0.60
0.42
0.43
1.15
0.76
0.75
0.58
1.08
0.78
4.38
1.26
0.56
0.68
0.87
1.38
0.51
Percent
Remova 1
76.8
76.4
94.0
81.8
69.4
64.2
83.3
89.3
74.1
63.7
79.3
99.7
74.6
80.3
86.3
71.4
86.5
__
75.7
55.8
53.2
22.0
84.2
98.7
Data collected from May 1, 1977 through August 31, 1977. System
3_is biological treatment followed by chemical/physical treatment.
(x ** mean, mg/liter)
-108-
-------
TABLE 26
SYSTEM 4 OPERATION'
AI ka Unity, as CaC03
Ammonia-N
BOD 5
Cadmium
Ca 1 c i urn
Chloride
Chromium
COD
Copper
Dissolved Solids
Hardness, as CaCO-j
Iron
Lead
Magnesium
Mercury
Nickel
pH
Phosphates
Potassium
Sod i urn
Sulfate
Suspended Solids
Zinc
Kjeldahl-N
n
12
12
13
13
13
13
13
38
13
39
13
13
13
13
13
13
39
12
13
13
14
39
13
12
influent
5
5087
649
12649
0.11
937
4178
0.48
21152
0.27
14742
4463
348
0.76
350
0.007
2.0
7.6
2.3
1076
1536
658
1136
40
708
cv
0.20
0.17
0.22
0.52
0.17
0.19
0.33
0.21
0.38
0.20
0.21
0.39
0.28
0.22
0.51
0.50
0.56
0.57
0.13
0.09
0.23
0.47
0.42
0.16
n
1
1
2
I
1
1
1
37
11
39
11
1
1
1
1
1
38
10
11
11
12
36
11
16
effluent
* - " cv
2788 0.13
312 0.35
2150 0.72
0.08 0.46
573 0.66
3778 0.23
0.37 0.39
468o 0.77
0.22 0.22
10081 0.20
2805 0.48
195 0.79
0.50 0.52
242 0.46
.0070.47
1.29 0.37
8.55 0.78
4.6 0.84
996 0.14
1412 0.09
853 0.44
1322 0.68
19 0.65
347 0.38
Percent
Kemova 1
45.2
51.9
83.0
27.3
38.8
9.6
22.9
77.9
18.5
31.6
37.1
44.0
34.2
30.9
0
35.5
7.4
8.1
--
52.5
51.0
"Data collected from May 1
is biological treatment only.
1977 through August 31
(x = mean; mg/liter)
1977. System
-109-
-------
TABLE 27
SUMMARY OF SYSTEM 3 OPERATION DATA
(5/1/77-8/31/77)
Parameter
AmmonJa-N
BOD5
Cadmium
Chromium
COO
Copper
Iron
Lead
Mercury
Nickel
Zinc
Raw
Leachate
mg/1
649
12649
0.11
0.48
21152
0.27
348
0.76
0.007
2.0
40
Final
Effluent
mg/1
153
763
0.02
0.08
2257
0.07
1.02
0.15
0.002
0.27
0.51
Percent
Remova 1
76.4
94.0
81.8
83.3
89.3
74.1
99.7
80.3
71.4
86.5
98.7
Discharge
Standard
mg/1
35
100
0.02
0.1
*
0.2
7.0
0.1
0.01
*
0.6
*No discharge standard for this parameter.
-110-
-------
are presented in Table 28. These tests have been performed with an
upflow column of depth 0,3 m and diameter 0,46 m, containing 15.9 kg
of granular activated carbon. The influent flow was 38 liter/min, thus
providing a hydraulic loading rate of 232 liter/min-sq m. As shown in
Table 28, no appreciable treatment cgn be attributed to the carbon
treatment. It should be noted that excessive suspended solids loading
and influent variability contributed to this finding. The effect of,the
solids is to cause blockages and hence reduce process efficiency. The
influent was not constant during any of the tests because it was drawn
from the actual plant influent. Therefore ft is impossible to calculate
removal efficiency. However, it Is evident from Table 28 that no
renovation is occurring in the carbon columns. Hence, it is concluded
that carbon adsorption is not appropriate when applied to raw leachate,
although, as mentioned below, it may be suitable for final effluent
polishing.
System 5 has also been assessed as an advanced waste treatment
technique. This has been done using the effluent from the pilot
facility shown in Figure 5. A summary of the data is given in Tables
29 and 30. The data in Table 28 have been developed using small carbon
columns and a flow rate of 10 ml per mln, |n each case, a 25 ml sample
was collected at each sampling Interval, Although batch data are more
amenable to such mathematical treatment, a preliminary analysis has
been conducted to describe the results of Table 29 In terms of a Langmu.ir
adsorption isotherm. The Langmuir Isotherm results from assuming
reversible adsorption and an adsorbed monolayer;
-111-
-------
TABLE 28
SUMMARY OF RESULTS OF CARBON ADSORPTION TREATMENT OF RAW LEACHATE*
Parameter
Gal Ions Treated
PH
Suspended Solids
Dissolved Solids
Total Volatile Solids
Chemical Oxygen Demand
Experiment Number
0
8.31
2880
10570
4240
4450
1
50 250
7.90 8.11
2280 3060
10490 9130
4040
3840 5760
0
___
980
10600
5120
8645
2
50
640
10450
3950
7217
320
20
11150
4230
9864
0
820
11100
5220
9530
3
100
___
540
11000
4930
9440
370
___
430
10970
5000
9841
Experiment Number
Gal Ions Treated
PH
Suspended Sol ids
Dissolved Solids
Total Volatile Solids
Chemical Oxygen Demand
0
520
10060
4530
9840
4
60
420
10690
5330
10784
0
__-
770
10460
5010
10013
5
20
500
10130
4360
9170
260
740
11040
5020
10040
0
___
1120
10040
6440
8833
6
60
___
1020
9400
6170
9723
300
___
1040
10230
6 180
9960
All units are mg/liter except pH and gallons treated.
-------
TABLE 29
TREATMENT OF FINAL EFFLUENT WITH BENCH-SCALE ACTIVATED CARBON COLUMNS*
Sample
1
2
3
k
5
6
1
2
3
k
5
6
7
8
9
10
Carbon
Volume, cm3
270
270
270
270
270
270
14.5
14.5
26.2
26.2
40.7
40.7
52.5
52.5
77.8
77.8
Weight Flow
of Carbon, g ml
100
100
100
100
100
100
5
5
10
10
15
15
20
20
30
30
0
100-125
225-250
350-375
475-500
600-625
725-750
250-275
500-525
250-275
500-525
250-275
500-525
250-275
500-525
250-275
500-525
COD
2088
354
657
830
748
827
869
1858
1818
1660
1760
1620
1660
1500
1620
1386
1500
Cu Fe
0.015 5.10
0 2.58
0 3.98
.015 4.80
.30 5.50
.68 1.60
.12 2.30
Zn Cr NJ
0.99 0.30 1.46
.30 .15 .08
.58 .20 .15
.53 .16 .26
.56 .15 .22
.61 .19 .26
.55 .18 .25
Ca Mg
174 142
0.74 0.89
1.72 2.00
2.29 2.59
2.05 3,47
5.86 8.6
>10 >10v
*A11 units are mg per liter, unless otherwise stated.
-------
TABLE 30
PILOT-SCALE CARBON TREATMENT OF FINAL EFFLUENT
Volume of Carbon Treated
Final Effluent, liter
0
95
189
289
379
416
454
492
530
568
606
662
719
795
871
Sorbate Concentration Following
Carbon Treatment, mg COD/liter
1900
25
35
395
1312
1539
1695
1773
1828
1859
1875
1852
1891
1883
1848
-114-
-------
-
m
( ) H value of when monolayer has been completed
x =" moles of sorbate adsorbed
m
weight of carbon
C =i equilibrium molar concentration of sorbate
b B adsorption coefficient
The analysis Indicated that (2~)ฐ is 9,709 mg per nig, and that b is 5,79
1 1 ters per mg.
The data shown in Table 30 have been collected from a larger column
charged with 120 Ib of carbon at 3 flow rate of 4 gal per min. These
results have been plotted as a carbon breakthrough curve In Figure 14.
The cross-hatched area of Figure \k can be used to determine the
fractional capacity, f, of the adsorption zone. The value of f is
estimated at 0.31. From this, it is estimated that the depth of the
adsorption zone Is 8.99 ft. These values can be used as the basis of
the design of a full-scale unit.
Additional Laboratory-Scale Studies. A number of smaller scale
studies were undertaken during the third year. These were designed to
evaluate a number of possible technologies which might be applied to more
efficiently treat the leachate. In addition to the activated carbon
treatment discussed above, the following were also assessed: alkaline
chlorination, effluent filtration, and effluent breakpoint chlormation.
In addition, the use of additives in the lime treatment process was
investigated as a means of increasing the compaction of the lime sludge,
Each of these topics is discussed in subsequent paragraphs.
-115-
-------
-9U-
EFFLUENT SOLUTE CONCENTRATION, COD, mg/liter
K>
vn
ui
o
< -^i
o vn
s; o
> o
H
m
;5
m
73 to
vn
rn
to
01
vn
o
CO
o
o
N>
vn
-------
Alkaline Chlorination, During a part of the third year, difficulties
were encountered in the efficiency of the Iime treatment process. It was
believed that the problems were possibly due to excessive hydraulic
loadings. In this light, the use of compacting agents as discussed
below was studied, and minor design changes were Instituted. One other
explanation for the difficulties encountered In the removal of heavy metal
is that the metals may have formed complexes with organic matter or with
cyanides. In this chemical form, the metals resist removal by lime
treatment. It might have been possible to improve the efficiency of lime
precipitation of heavy metals by adding chlorine during this step.
Alkaline chlorination has the effect of disrupting heavy metal complexes,
particularly those involving cyanides. In this manner, the metals are
freed from the complex ing agents, after which they precipitate under the
alkaline pH conditions.
Preliminary evaluations of alkaline chlori-nation were conducted.
The results were negative as shown In Table 31. The samples of raw
leachate were supplemented with the chemicals indicated in Table 31,
mixed for 5 min with a magnetic stlrrer, and then allowed to settle for
30 min. The volume of sludge produced was recorded, and analyses for
heavy metals were performed on the clarified supernatant. The addition
of NaOCl had no significant effect on sludge volume, nor on the
concentration of copper and cadmium, may have been associated with
reduced concentrations of zinc, nickel and lead, and was definitely
associated with reduced concentrations of iron and chromium. The results
were deemed negative, because the addition of small amounts of chlorine
-117-
-------
TABLE 31
RESULTS OF ALKALINE CHLORINATION STUDIES
00
Sample
#
1
2
3
4
5
6
7
Lime
Addition*
0
19
19
25
30
19
19
NaOCl
Addition*
0
0
5
10
15
10
15
PH
11.3
11.2
11.1
11.3
10.5
10.0
Sludge
Volume*
100
120
150
120
>90
>90
Fe+
7.5
2.28
0.3
0.263
0.275
0.313
0.425
Cu+
0.25
0.213
0.275
0.216
0.293
0.21
0.209
Cr+
0.175
0.153
0.141
0.134
0.138
0.104
0.099
Pb+
0.25
0.3
0.25
0.24
0.24
0.15
0.18
U- +
Ni
1.095
0.831
0.769
0.691
0.668
0.69
0.668
Cd+
0.076
0.071
0.061
0.073
0.056
0.04
0.059
Zn+
10.6
0.09
2.08
1.27
1-95
0.09 '
0".05 ".
millillters
mi 11igrams per 1iter
-------
did not significantly affect the ability of the process to meet effluent
r h
standards. Very high concentrations of NaOCl may be helpful jn attaining
the chromium standard (see Table 1),
Compaction of Lime Sludge, The second possible cause of poor lime
treatment performance to be investigated was that of inferior
settleabl1ity of the sludge, A number of Jar tests have been conducted
in an effort to evaluate the effect of additives on the efficiency of
heavy metal precipitation and on the compaction of the resultant lime
sludge. These tests have been performed to evaluate the performance of
lime, a commercial aluminate preparation, and sodium hydroxide. The
results are presented in Tables 32 and 33, The first of these tables
shows the experimental protocol whjch was, fn brief, to treat each flask
with lime to give a final pH of 11,7, Aluminate was added at the rate of
300 mg/1 as recommended by the manufacturer's representative. Sodium
hydroxide was added at the rate of 125 ppm in accordance with the
observation of the leachate treatment plant operator who noted a decided
improvement in process efficiency at this dosage of caustic. |t should
t
be noted that the use of aluminate did not result in an especially clear
supernatant and that it did result in a relatively large volume of
sludge. On the other hand, the addition of NaOH provided a very clear
supernatant, at least equal to that obtained with lime alone, and a
relatively small sludge volume. The results, in terms of the removal
ป
of heavy metals, are presented in Table 33, None of the additives were
an improvement over lime alone, in terms of meeting the standards (see
Table 1). In absolute terms, neither additive, alone or in combination,
provided improved treatment across the board. In fact, in several cases,
-119-
-------
TABLE 32
EXPERIMENTAL PROTOCOL AND PRELIMINARY RESULTS
IN EVALUATION OF LIME TREATMENT ADDITIVES*
Preliminary Results
Experimental Protocol
Flask
Number
1
2
3
4
5
Lime, ml
0
18
18
12
15
Additives
Aluminate, ml
0
0
10
0
10
Supernatap
NaOH, ml ClarityJ-
0
0 ++
0
0.1 ++
0.1 +
t Sludge
Volume, ml
0
110
120
80
120
The experimental flasks each contained raw leachate plus the
additives as indicated.
$The clarity of the supernatant was evaluated qualitatively as
follows: , very turbid; -, turbid; +, clear; -H-, very clear. Also
the volume of sludge (in ml) produced was noted.
-120-
-------
TABLE 33
RESULTS OF ADDITIVE EVALUATION'
Experimental Protocol
Parameter
Analyzed
Iron
Copper
Cadmium
Chromium
Lead
Zinc
Nickel
Mercury
Raw
Leachate
Control
52.0
0.2k
0.0k
0.15
0.19
6.40
0.71
0.002
Lime
Only
0.45
0.14
0.06
0.09
0.16
0.03
0.56
0.002
Lime
+
Aluminate
1.21
0.16
0.04
0.07
0.19
0.12
0.52
0.002
Lime
+
NaOH
0.77
0.14
0.07
0.08
0.16
0.10
0.58
0.001
Lime + NaOH
-i-
Aluminate
1.71
0.24
0.03
0.09
0.15
0.08
0.53
0.002
*
All units are mg per liter in the supernatant following
indicated protocol.
-121-
-------
the removal decreased due to the additives. The conclusion is that
neither NaOH nor aluminate, when added to lime and leachate at a final
pH of 11.7, results in improved removal of heavy metals. However, the
addition of 125 ppm NaOH provides a significant reduction in sludge
volume, a fact which would improve the efficiency of the lime clarifier
operation. Sludge handling and disposal will also be rendered more
efficient. Therefore, the addition of NaOH was recommended.
An added benefit is a higher pH in the ammonia lagoon which
increases the ammonia stripping capacity of the lagoon. This is
illustrated by the observation that the supernatant pH where NaOH was
added had fallen to only 11.5, whereas, in the flasks not receiving
NaOH, the supernatant pH had dropped to less than 11. This is a
demonstration of the strong buffering properties attributable to the
addition of NaOH.
An additional recommendation was made which improved the efficiency
of the lime clarifier. This was that the depth of the sludge blanket
be kept minimal. This prevented solids carryover which occurred on
occasion in the past. Sludge blanket depth may be minimized by
sem?-continuous withdrawal of settled sludge. An automatic timing
mechanism was installed to ensure sludge removal semi-continuously on
a 2k hr basis.
Effluent Filtration. The physical process of filtration has
several potential applications in leachate treatment. Filtration of
activated sludge effluent would be needed before activated carbon or
ion exchange treatment, if these operations are necessary. This is
-122-
-------
required to reduce the solids loadings on these units, and hence, to
minimize problems due to clogging.
A second application of filtration would be to use it between the
ammonia stripping lagoon and the activated sludge process. The purpose
of doing this is to remove residual heavy metal precipitates as well as
calcium carbonate which may form during lagooning or which may escape
the lime clarifier unit. The benefits which would accrue include
lower heavy metals loadings and solids loadings on the biological
treatment units.
The first step in evaluating the efficacy of filtration is a
number of small scale units. The purpose of these would be to provide
a preliminary evaluation of the removal of heavy metals and particulates
from the ammonia lagoon effluent, and to determine the compatability of
a filtered effluent from the activated sludge process with granular
activated carbon.
The principal design parameters which must be considered are filter
configuration; method of flow control; terminal headless (ft of water);
filtration rate (gal/min-sq ft); filter media, sizes and depths; and,
backwashing requirements. The basic filter configurations are upflow
filtration through a relatively deep, coarse filter medium; using a
filtered water collection device within the filter medium and bringing
water in from both the bottom and the top; dual or mixed media with
conventional downflow; and single medium downflow filtration.
Preliminary testing of filtration has been conducted using filter
paper (Whatman No. 40). The results are presented in Table 3k, and
they show that additional removals of most of the heavy metals are
-123-
-------
IS)
-t-
TABLE 34
j
PRELIMINARY FILTRATION. RESULTS'
Metal
1 ron
Copper
Cadmium
Chromium
Lead
Nickel
Mercury
Zinc
Unfil
256.
0.
0.
0.
0.
1.
0.
23.
Raw Leachate
tered Filtered
48
13
36
47
46
003
4
194
0
0
0
0
1
0
17
.
.40
.08
.36
.35
.29
.004
.2
Ammon
Unfil
32.
0.
0.
0.
0.
1.
0.
4.
ia Lagoon Effluent
tered Filtered
13
06
18
23
22'
003
63
18.
0.
0.
0.
0.
1.
0.
3.
20
08
15
19
08
0025
36
Final Effluent
Unfil tered Filtered
10
0
0
0
0
1
0
1
.26
.05
.12
.12
.06
.004
.28
5.6
0.25
0.04
0.09
0.10
0.88
0.0025
1.70.
All units are mg per liter.
-------
achieved by filtration at any intermediate step of the treatment
sequences.
Effluent Breakpoint ChlorinatJon. Although nitrification is an
extremely efficient process for the removal of ammonia-N, it is a
biological treatment method. As a result, nitrification can be
temperamental and prone to upset. As noted earlier, the nitrifying
organisms are very sensitive to temperature. Also, the ammonia
stripping process is less effective during the winter. Consequently,
the effluent in the colder months is very high in ammonia-N. The
removal of residual ammonia in the final effluent may be accomplished
by breakpoint chlorination. This procedure oxidizes the NH.-N to
gaseous end-products including N2- Breakpoint chlorination has been
practiced at the GROWS treatment facility and is a proven technology
for meeting the effluent criterion for ammonia (see Table l).
The chlorine demand, and therefore chlorination operating costs,
are expected to decrease as the degree of organics removal increases,
and this savings can affect some portion of the carbon costs. An
economic tradeoff can be made here vis-a-vis the costs of activated
carbon treatment of the final effluent.
Leachate Treatment., Plant Startup. The results of this study have
indicated clearly that Systems 1 and 2 are very effective in the
treatment of leachate. The best results were obtained with a process
train consisting of raw leachate equalization, lime precipitation and
clarification, ammonia stripping lagoon, activated sludge providing
for carbonaceous and nitrogenous oxidation, sedimentation, and
-125-
-------
effluent chlorination. As noted in Tables H, 15, 20 and 21, the
removal efficiencies observed with Systems 1 and 2 are extremely high,
and provide the best opportunity for meeting the effluent criteria.
Nevertheless, in spite of the success of Systems 1 and 2, some
problems were encountered during startups. Some of these have been
discussed elsewhere. These include the nutrient deficiency due to
phosphate precipitation in the lime treatment unit; and substrate
inhibition resulting from excessive ammonia-N concentrations.
Excessive loadings have been received by the plant in terms of
ammonia, metals, and organlcs. For the past year, raw leachate flows
have been in the 50,000 to 80,000 gpd range, which when coupled with
the extremely high influent concentrations yields process loadings in
excess of those which had been experienced during the initial
operational phase of the plant. The combination of excessive
concentrations and loadings is the primary factor inhibiting rapid
successful process startup.
There are a number of secondary reasons for the poor startup
performance. The first of these is that the third year operational
effort was initiated in mid to late winter. As a result, the
development of a healthy activated sludge culture was inhibited due to
low temperatures, as well as to the presence of high concentrations of
metals and organics. These high concentrations resulted not only
because of the leachate strength, but also because of operational
problems. Examples of these problems include instances where raw
leachate has by-passed the chemical/physical section, and insufficient
air has been provided to the bio units.
-126-
-------
Other secondary factors underlying the startup problems include
those relating to plant operation and the behavior of the sedimentation
tanks. Frequent problems were encountered which affected adversely the
performance of both the chemical/physical and the secondary clarifiers.
Eddy currents were occasionally noted in the secondary clarifier and
these resulted in carry-over of biological solids. The high rate of
internal recycle in the activated sludge undoubtedly contributed to this
condition. In the case of the chemical/physical sedimentation tank,
some reduction in clarification efficiency was observed as a result of
excessive sludge volumes. Lime sludge production had increased as the
acidity and the rate of generation of 1eachateJncreased.
Many of the problems mentioned above are essentially different
aspects of plant reliability. Each section of the plant needs a high
level of reliability. This is especially true of the lime treatment
section. It is recommended that, in the future, as these plants become
more sophisticated, greater consideration be given to automatic process
control techniques. As an example consider the lime slurry system. At
the present time, if this system malfunctions such that the 1ime feed
stops, then raw 1eachate passes to the ammonia lagoon and thence to the
bio units where pronounced inhibitory effects are observed. These
problems could be avoided by an automatic valving system which would
recycle the lime clarifier effluent to the equalization pond whenever
the effluent pH dropped below some set point such as pH 10 or pH 10.5.
Process reliability is important at plants such as this because they
normally operate at very close to inhibitory concentrations of
-127-
-------
materials such as ammonia, metals, and organics. Thus, small
..perturbations can result in process upset followed by an extensive
period during which the discharge standards are contravened.
Most of the startup problems, however, are related directly to the
increased leachate flow and strength. Higher flows have not diluted
the leachate, but have been associated with increased concentrations of
pollutants. This, in turn, is partially a result of the introduction
of industrial liquid wastes.
An indication of the extremely high loadings is provided in Table
35- The data show process loadings applied to System 2 (lime treatment/
ammonia lagoon) and to System 1 (activated sludge). These data are for
the period April 1, 1978 through June 30, 1978. This represents the
startup period for the most recent evaluation of Systems 1 and 2. For
comparison, the original design loadings, derived from Table 9, are
included. It can be seen that the more recent loadings are very high
(except for the metals and suspended sol ids). When this is coupled
with the high concentrations of inhibitory substances, the basis for
the poor startup performance becomes clear.
The role of high concentrations relates to a previous discussion.
As noted in Figure 9, the phenomenon of substrate inhibition must be
considered. Even substrates such as ammonia-N or BOD which are vital
requirements at low concentrations become inhibitory at higher
concentrations. The significance for leachate treatment is that the
system operates at influent concentrations high enough to be inhibitory.
Slight perturbations result in process instabi1ity and/or poor startup.
-128-
-------
TABLE 35
PROCESS LOADING RATES AND CONCENTRATIONS OBSERVED
DURING THE PERIOD APRIL 1, 1978 THROUGH JUNE 30, 1978.
Concentration
of Raw Leachate
mg/1 iter
Observed Design
Alkal inity, as CaCO,
Anwion i a-d
BOD
Cadmium
Calcium
Chloride
Chromium
COD
Copper
Dissolved Solids
Hardness, as CaC03
1 ron
Kjeldahl-N
Lead
Magnesium
Mercury
Nickel
Organic-N
Phosphates
Potassium
Sodium
Sulfate
Suspended Solids
Total Solids
Zinc
4915
990
13695
0.09
895
2965
0.24
19864
0.24
13225
3750
165
860
0.37
275
0.253
1.45
=0
1.98
1000
1455
515
1510
14735
11.44
1100
1500
800
--
ซ
1
--
800
600
100
__
__
300
1500
3000
10
Process Loading Rates
Ib per day
Raw Leachate
Observed
2710
546
7550
0.05
493
1634
0.13
10950
0.13
7290
2065
90
475
0.20
150
0.14
0.80
1.09
550
800
285
830
6.31
Design
1320
1800
--
960
1.20
960
720
.-
__
_ซ-
__
__
__
__
360
.1800
12
Appl led to
Lime Treat-
ment Section
1730
350
4830
0.03
315
1045
0.08
7000
0.08
4660
1320
60
305
0.13
95
0.09
0.51
0.80
350
515
180
530
4.03
Appl led to
Activated
Sludge System
210
40
560
0.003
40
155
0.007
880
0.009
605
135
0.42
45
0.02
7.8
0.01
0.07
0.02
55
80
55
20
0.06
-------
Thus, the principal source of process startup problems are the
combination of excessive loadings and concentrations near the upset
threshhold.
The activated sludge system has been operated most successfully at
a mixed liquor volatile suspended solids (MLVSS) concentration of
6000-12,000 mg per liter, depending upon the influent BOD concentration.
During periods of satisfactory operation the food to microorganism
ratio has been in the 0.12 to 0.32 day" range, as calculated by
where
L - F:M, Ib BOD per Ib MLVSS-day
0_ ~ Process hydraulic loading, gpd
C = Process influent BOD, mg per liter
V = Aeration tank volume, gal
X = MLVSS, mg per liter
3
The operation of the activated sludge units in series (see Figure 7)
was accomplished by maintaining 12,000 mg MLVSS per liter and 6000 mg
MLVSS per liter, in the first and second stages, respectively.
The following recommendations are made in an effort to reduce
future startup problems:
1. Raw leachate equalization is a valuable aid in dampening peak
concentrations of materials which are inhibitory to subsequent
biological processes; and, in controlling chemical dosages in
the lime precipitation units.
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Ammonia removal ,by stripping via aeration reduces concentrations
to a level below the point of inhibition.
Nutrient: supplementation may be necessary. This is especially true
for the case of a high carbon waste with biological treatment units
preceded by lime precipitation.
Excessive loadings may necessitate treatment of only a portion of
the total waste flow during startup. At these times, the balance
of the flow should be recycled to the landfill.
With a waste containing very high levels of ammonia-N, startup
should occur during warm weather months. Otherwise, nitrification
will be inhibited, and the resulting ammonia concentrations will not
permit biological activity.
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VI. CONCLUSIONS
The GROWS landfill leachate is characterized by high organic strength
and by large day-to-day variations. Much of the variability can be
dampened by raw leachate equalization.
Considerable experience has been gained in the operation of activated
sludge units on raw leachate and on leachate which has received
chemical/physical treatment. It has been concluded that this raw
leachate must be pre-treated in order to render it amenable to
activated sludge processing. The results indicate that the raw
leachate inhibits the growth of the activated sludge microorganisms.
System 3 (biological treatment of raw leachate) has yielded an
average effluent BODj. of 763 mg per liter, a concentration which is
clearly not acceptable.
The operation of the chemical/physical units (System 2) has continued
for some time to gain experience under a wide variety of operating
conditions and sufficient data have been collected to provide an
evaluation of this method of treating raw leachate. Lime treatment
alone (System 2a) provides removal efficiencies of approximately 50
percent of the organic matter, 75 percent of suspended solids,
one-half of mercury and cadmium, and at least two-thirds of the
other heavy metals.
f
The complete chemical/physical treatment sequence consisting of
lime precipitation/sedimentation/ammonia stripping (System 2b)
achieved the following removals of efficiency: kS to 69 percent
of the organic matter, ammonia-N and total kjeldahl-N; 70 percent
of the suspended solids, and 50 percent or better of the heavy
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metals except copper, for which,fhe removal efficiency was 37.8.
percent. In the final year of the project, System 2b was augmented
with an initial raw leachate equalization step.
5. Temperature and pH have an effect on the concentration of heavy
metals in the lime treatment effluent. However, the response is
not identical for all heavy metals. If the differences were more
thoroughly characterized, it might be possible to use them in an
operational control procedure.
6. Activated sludge treatment of the effluent from the chemical/physical
units has been extremely successful (System 1). It is apparent that
the reduction in ammon'ia-N afforded by the ammonia stripping lagoon
provides conditions suitable for the growth of activated sludge
microorganisms. The ammonia lagoon, in conjunction with the balance
of System 2, provides ammonia removals of approximately 50 percent
resulting in activated sludge influent concentrations of 1^9-423 mg
NH-N/liter (95 percent confidence interval). During the final
year of the project, these concentrations increased somewhat due
to the maintenance of a lower pH in the lagoon. Under this condition,
the activated sludge quickly adapted to the leachate with the result
that effluent BOD- concentrations were consistently low except during
cold weather. Nitrifying organisms developed and produced a
nitrified effluent with very low concentrations of ammonia. Cold
winter weather inhibited the biochemical oxidation of organics and
ammon i a.
7. Activated sludge treatment has been effective in both the series
(Figure 7) and parallel (Figure 4) modes of operation. That is, the
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plant configuration has had the aeration tanks in either parallel
or series, with approximately equal results.
8. Overall, the treatment sequence consisting of chemical/physical
(lime precipitation, sedimentation, ammonia stripping, and
neutralization) followed by activated sludge (System 1) has
produced an excellent final effluent with the following
characteristics:
a. Organic matter has been reduced to 153 mg BODg/liter.
This is a 99 percent removal. The corresponding COD
removal efficiency is 95 percent. The effluent BOD
co COD ratio is 0.16.
b. The effluent ammonia concentration is 75 mg/liter,
representing 90 percent removal.
c. Heavy metals are found in the effluent at the following
levels (percent removals are shown in parenthesis):
0.017 mg cadmium/liter (78.2 percent); 0.07 mg
chromium/liter (73.. 1 percent); 0.11 mg copper/liter
(72.5 percent); 2.7 mg iron/liter (99.2 percent);
0.12 mg lead/liter (83.8 percent); 0.004 mg mercury/
liter (27.4 percent); 0.75 mg nickel/liter (57.4
percent); 0.53 mg zinc/liter (97.3 percent).
9. The kinetics of nitrification have been followed during System Ib
operation. The rate of nitrification, expressed as the specific
oxidation rate, follows the van't-Hoff Arrhenius relationship.
The data indicate that the activation energy is approximately
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12350 cal per mole, and that the Arrhenlus frequency factor is
2.18 x 109 day"1.
10. The data show that substrate Inhibition due to ammonium Ion
concentration occurs in System Ib nitrification. This relationship
has been expressed as a Haldane inhibition model in which the maximum
specific oxidation rate is 3.5 g N oxidized per g biomass day, K
is k mg per liter, and Kj is 36 mg per liter.
11. Pilot scale operation of System 5 shows that activated carbon
treatment of System 1 effluent is an effective way of removing
much of the remaining organic matter. In addition, considerable
removals of heavy metals occur in the carbon columns.
12. A bench-scale evaluation of alkaline chlorlnation as a means of
improving heavy metals removal Indicated that the technique is not
appropriate.
13- Studies of lime sludge compaction and supernatant clarity reveal
that the addition of sodium hydroxide (125 mg per liter) improves
both factors. The addition of a commercial aluminate preparation
(300 mg per liter) had an adverse impact on compaction and clarity.
14. Preliminary testing of filtration shows that additional removals
of most heavy metals can be achieved.
15. Full-scale studies of breakpoint chlorlnation have shown that this
method can be used to attain the ammonia effluent criterion.
-135-
-------
VII. REFERENCES
1.
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4.
5.
6.
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pal 764
SW-758
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EPA REGIONS
U.S. EPA. Region 1
Solid Waste Program
John F. Kennedy Bldg.
Boston, MA 02203
617-223-5775
U.S. EPA, Region 2
Solid Waste Section
26 Federal Plaza
New York, NY 10007
212-264-0503
U.S. EPA, Region 3
Solid Waste Program
6th and Walnut Sts.
Philadelphia, PA 19106
215-597-9377
U.S. EPA, Region 4
Solid Waste Program
345 Courtland St., N.E.
Altanta, GA 30308
404-881-3016
U.S. EPA, Region 5
Solid Waste Program
230 South Dearborn St.
Chicago, IL 60604
312-353-2197
U.S. EPA, Region 6
Solid Waste. Section
1201 Elm St.
Dallas, TX 75270
214-767-2734
U.S. EPA, Region 7
Solid Waste Section
1735 Baltimore Ave.
Kansas City, MO 64108
816-374-3307
U.S. EPA, Region 8
Solid Waste Section
1860 Lincoln St.
Denver, CO 80295
303-837-2221
U.S. EPA, Region 9
Solid Waste Program
215 Fremont St.
San Francisco, CA 94105
415-556-4606
U.S. EPA, Region 10
Solid Waste Program
1200 6th Ave.
Seattle, WA 98101
206-442-1260
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