Physical-Chemical Treatment and Disinfection of A
PHYSICAL-CHEMICAL TREATMENT AND DISINFECTION
OF A LANDFILL LEACHATE
by
Victor B. Bjorkman
B.A.Sc., University of British Columbia, 1951
A THESIS SUBMITTED IN PARTIAL FULFILLMENT
OF THE REQUIREMENTS FOR THE DEGREE OF
MASTER OF APPLIED SCIENCE
in
The Faculty of Graduate Studies C The Department of Civil Engineering)
We accept this thesis as conforming
to the required standards
THE UNIVERSITY OF BRITISH COLUMBIA
May, 1979 Victor Bernhard Bj orkman In presenting this thesis in partial fulfillment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study.
I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the Head of my Department or his representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my permission.
Victor B. Bjorkman
Department of Civil Engineering
The University of British Columbia 2075 Westbrook Place Vancouver, British Columbia V6T 1W5 Canada ii
ABSTRACT
Water, flowing through beds of refuse in a sanitary landfill, will leach organic and inorganic substances from the fill. These leached substances may be a source of pollution for receiving surface or ground waters. The leachate, before it is diluted by the receiving water, can usually be classed as a very strong waste water; that is, the levels of the waste water parameters COD, Suspended Solids, low dissolved oxygen and turbidity are many times those found in normal, municipal waste water.
Added to these foregoing parameters are possible high levels of toxic chemicals and metals.
It is now generally recognized that the leachate from refuse landfills should be controlled, and in some recently designed landfills, leachate collection is incorporated into the overall design. Toxic chemicals and metals are not adequately removed from waste waters by the standard biological sewage treatment processes; thus, the collected landfill leachate often requires pretreatment before it can be discharged to a municipal sewer system. If it is to be discharged to a natural receiving water, it requires more complete treatment.
It was the purpose of this research to attempt to develop a physical-chemical treatment system for landfill leachate, such that the effluent might be safely discharged to a biological treatment plant or a natural receiving water.
To deal with the extremely large number of possible chemical reagents, and to a lesser extent, physical methods available-, it was first necessary to select a number of primary candidates from prior information and theory available in the literature; secondly, it was advantageous to use a statistically designed experimental programme for screening those candidates chosen.
In the screening process, no changes in the physical parameters screened, such as duration and speed of mixing or duration of settling, were found to be significant, if normal minimum times and usual speeds were used. Four chemical reagents, lime, ozone, ferric sulfate, and alum were indicated as having a potentially significant effect on the leachate- contained Total Solids (TS), Total Carbon (TC), Turbidity (Turb), Cadmium
(Cd), Copper (Cu), Iron (Fe), Zinc (Zn), Potassium (K), Calcium (Ca),
Sodium (Na), Phosphorus and the acid-base relationship as expressed by the term pH. The follow-up experiments determined that only two of the above four reagents were significantly effective in removal of the afore-named pollutants, as well as Manganese (Mn), Lead (Pb), Colour, Chemical Oxygen
Demand (COD), the components of Total Carbon (TC) Total Inorganic Carbon
(TIC) and Total Organic Carbon (TOC), and the components of Total Solids
(TS)—Suspended Solids (SS) and Dissolved Solids (DS).
All of the multivalent metals, except Calcium, were significantly removed from this wastewater by pH adjustment with lime, with additional minor removals by oxidation with ozone. Dissolved organic materials were not removed by pH adjustment and only removed in approximate stoichiometric amounts by reaction with ozone. In these experiments, the polymers tested were not effective in the removal of the named pollutants.
Ozone is indicated to be an effective disinfectant, but highly
sensitive to the COD of the leachate. An ozone-COD ratio, which determines the quantity of applied ozone necessary for the oxidation of some of the dissolved metals and for disinfection, as a function of the contained COD, is proposed for this leachate. The possibility of the application of this ozone-COD ratio is put forth, subject to further investigation. V
TABLE OF CONTENTS
ABSTRACT t ii
LIST OF TABLES' viii
LIST OF FIGURES xi
ACKNOWLEDGEMENT xiii
Chapter
1 INTRODUCTION 1
1.1 The Sanitary Landfill 1
1.2 Landfill Leachate 1
1.3 Leachate Production 2
1.4- Effect of Leachate on Receiving Environment 2
1.5 The Character of Leachate 3
1.6 Purpose of This Research Project 3
2 LITERATURE REVIEW AND EXPERIMENTAL DESIGN 10
2.1 Previous Research on the Treatment of Landfill
Leachate 10
2.2 Experimental Programme 12
3 . GENERAL-REVIEW OF PHYSICAL CHEMICAL PROCESSES 14
3.1 General Process Description 14
3.2 Physical Unit Processes 14
3.3 Chemical Unit Processes 14
3.4 Advantages and Disadvantages of Physical-Chemical
Processes 15
4„ SELECTION OF REAGENT AND PROCESS CANDIDATES 17
4.1 Division of the Experimental Programme into Two Phases 17 vi
4.2 Chemical Reagents 17
4.3 Physical Unit Operations Screened 18
5 EXPERIMENTAL DESIGN 20
5.1 Statistical Factorial Design 20
5.2 Fractional Factorial Design 20
5.3 Calculation of Effects 24
5.4 Calculation of the Standard Deviation 26
5.5 Determining the Significant Effects 28
6 EXPERIMENTAL APPARATUS AND ANALYTICAL METHODS 42
6.1 Ozone Generating and Contact System 42
6.2 Physical Unit Processes Simulation 44
6.3 Analytical Methods 45
6.4 Disinfection with Ozone • 46
6.5 Ozone Disinfection Procedure 47
7 PRESENTATION AND DISCUSSION OF DATA 48
7.1 Data—Screening Experiments 48
7.2 Discussion of Screening Data 48
7.3 Post-Screening Experimental Data 50
7.4 Discussion of Post-Screening Data 72
7.5 Data—Ozone Disinfection 77
7.6 Discussion of Disinfection Data 77
7.7 General Discussion 80
7.8 Application of Results to Predict Ozone Requirements . 83
7.9 Cost Considerations 89
8 CONCLUSIONS AND RECOMMENDATIONS 91
8.1 Conclusions 91 vii
8.2 Recommendations 92
9 LIST OF REFERENCES 9 5
10 APPENDICES
General Bibliography 98
Raw Data 99 viii
LIST OF TABLES
TABLE
1 LIMITS FOR EFFLUENT PARAMETERS THAT MAY BE OF CONCERN IN
SPECIFIC DISCHARGE 4
2 RECEIVING WATER QUALITY MAINTENANCE OBJECTIVES .... 6
3 TYPICAL COMPOSITION OF LEACHATES 9
4 TREATMENT VARIABLES SCREENED AND APPLIED LEVELS OF EACH
CORRESPONDING TO "HIGH" AND "LOW" LEVELS INDICATED IN
SCREENING DESIGN MATRIX OF TABLE 5 19
5 PLACKET-BURMAN DESIGN FOR DETERMINING THE EFFECT OF 15
VARIABLES, AT 2 LEVELS EACH, USING 16 RUNS 22
6 POLLUTANTS MEASURED IN THE SCREENING PROCESS .... 23
7 FOUND VALUES OF THE POLLUTANTS MEASURED IN THE SCREENING
EXPERIMENTS 25
8 COMPILATION OF STATISTICALLY SIGNIFICANT EFFECTS FOR
VARIABLES OF SCREENING EXPERIMENTS 41
9 COMPILATION OF REAGENT DOSING LEVELS FOR GROUPS 1, 2 AND
3 WITH SIGNIFICANT POLLUTING CHARACTERISTICS SHOWN WHERE
APPLICABLE 52
10 COMPILATION OF REAGENT DOSING LEVELS FOR GROUPS 4, 5 AND
6 WITH SIGNIFICANT POLLUTING CHARACTERISTICS SHOWN WHERE
APPLICABLE 53
11 COMPILATION OF REAGENT DOSING LEVELS FOR GROUPS 7, 8 AND
9 WITH SIGNIFICANT POLLUTING CHARACTERISTICS SHOWN WHERE
APPLICABLE 54
12 COMPILATION OF REAGENT DOSING LEVELS FOR GROUPS 10 AND 11
O ix
WITH SIGNIFICANT POLLUTING CHARACTERISTICS SHOWN WHERE
APPLICABLE 55
13 COMPILATION OF REAGENT DOSING LEVELS FOR GROUP 12,
RUNS 101-104 56
14 NAME CODES FOR THE INDEPENDENT VARIABLES FOR THE
POST-SCREENING EXPERIMENTS (.GROUPS 2-12) 57
15 REMOVAL OF SELECTED POLLUTANTS FROM LANDFILL LEACHATE IN
EXPERIMENTAL GROUP 2, RUNS 17, 18, 20, 23, 27, 29, 30,
31, 32 58
16 REMOVAL OF SELECTED POLLUTANTS FROM LANDFILL LEACHATE IN
EXPERIMENTAL GROUP 4, RUNS 37-52 59
17 REMOVAL OF SELECTED POLLUTANTS FROM LANDFILL LEACHATE IN
EXPERIMENTAL GROUP 5, RUNS 53-56 60
18 REMOVAL OF SELECTED POLLUTANTS FROM LANDFILL LEACHATE IN
EXPERIMENTAL GROUP 6, RUNS 57-61 61
19 REMOVAL OF SELECTED POLLUTANTS FROM LANDFILL LEACHATE IN
EXPERIMENTAL GROUP 7, RUNS 57, 62-64 62
20 REMOVAL OF SELECTED POLLUTANTS FROM LANDFILL LEACHATE IN
EXPERIMENTAL GROUP 8, RUNS 65-72 63
21 REMOVAL OF SELECTED POLLUTANTS FROM LANDFILL LEACHATE IN
EXPERIMENTAL GROUP 9, RUNS 73-80 64
22 REMOVAL OF SELECTED POLLUTANTS FROM LANDFILL LEACHATE IN
EXPERIMENTAL GROUP 10, RUNS 81-96 65
23 REMOVAL OF SELECTED POLLUTANTS FROM LANDFILL LEACHATE IN
EXPERIMENTAL GROUP 11, RUNS 97-100 66
24 REMOVAL OF SELECTED POLLUTANTS FROM LANDFILL LEACHATE IN
EXPERIMENTAL GROUP 12, RUNS 101-104 67 X
25 EXAMPLE OF A FACTORIAL DESIGN MATRIX USED IN THE
POST-SCREENING EXPERIMENTS WITH THE MAIN EFFECTS AND THE
INTERACTION EFFECTS CALCULATED FOR EACH OF THE FOUR
TREATMENT VARIABLES USED IN GROUP 4 (EFFECT ON DEPENDENT
VARIABLE—COLOUR) % 69
26 SUMMARY OF BEST LOW' RESIDUALS OBTAINED WITH'REAGENT
DOSES AND DOSE RANGES AS INDICATED 78
27 STANDARD PLATE COUNTS AT 35°C FOR LEACHATE TREATED WITH
OZONE (COD OF 14,300 irig/1) 79 xi
LIST OF FIGURES
FIGURE
1 HALF-NORMAL PLOT OF THE SCREENING DATA FOR TURBIDITY
WITH RELATED TABULATED EXAMPLE OF THE STANDARD
DEVIATION CALCULATION 27
2 HALF-NORMAL PLOT OF THE SCREENING DATA FOR pH WITH
RELATED TABULATED EXAMPLE OF THE STANDARD DEVIATION
CALCULATION 30
3 HALF-NORMAL PLOT OF THE SCREENING DATA FOR TOTAL
CARBON WITH RELATED TABULATED EXAMPLE OF THE
STANDARD DEVIATION CALCULATION 31
4 HALF-NORMAL PLOT OF THE SCREENING DATA FOR PHOSPHORUS
WITH RELATED TABULATED EXAMPLE OF THE STANDARD
DEVIATION CALCULATION 32
5 HALF-NORMAL PLOT OF THE SCREENING DATA FOR TOTAL
SOLIDS WITH RELATED TABULATED EXAMPLE OF THE
STANDARD DEVIATION CALCULATION ... 33
6 HALF-NORMAL PLOT OF THE SCREENING DATA FOR CADMIUM
WITH RELATED TABULATED EXAMPLE OF THE STANDARD
DEVIATION CALCULATION 34
7 HALF-NORMAL PLOT OF THE SCREENING DATA FOR COPPER
WITH RELATED TABULATED EXAMPLE OF THE STANDARD
DEVIATION CALCULATION 35
8 HALF-NORMAL PLOT OF THE SCREENING DATA FOR ZINC
WITH RELATED TABULATED EXAMPLE OF THE STANDARD
DEVIATION CALCULATION 36 xii
9 HALF-NORMAL PLOT OF THE SCREENING DATA FOR CALCIUM
WITH RELATED TABULATED EXAMPLE OF THE STANDARD
DEVIATION CALCULATION 37
10 HALF-NORMAL PLOT OF THE SCREENING DATA FOR POTASSIUM
WITH RELATED TABULATED EXAMPLE OF THE STANDARD
DEVIATION CALCULATION 38
11 HALF-NORMAL PLOT OF THE SCREENING DATA FOR SODIUM
WITH RELATED TABULATED EXAMPLE OF THE STANDARD
DEVIATION CALCULATION 39
12 HALF-NORMAL PLOT OF THE SCREENING DATA FOR IRON
WITH RELATED TABULATED EXAMPLE OF THE STANDARD
DEVIATION CALCULATION 40
13 SCHEMATIC OF OZONATING SYSTEM 43
14 EXAMPLE OF THE HALF-NORMAL PLOT OF THE ABSOLUTE VALUES
OF THE CALCULATED DEPENDENT VARIABLE EFFECTS ON COLOUR
WITH THE RELATED STANDARD DEVIATION CALCULATION 71
15 CHART FOR ESTIMATING OZONE DOSE REQUIRED TO OXIDIZE
CERTAIN METALLIC IONS AND LIVING ORGANISMS 88 xiii
ACKNOWLEDGMENT
The author gratefully acknowledges the guidance, assistance and
interest of his Supervisor, Dr. D. S. Mavinic. Acknowledgment is also made of the helpful advice received from Dr. W. K. Oldham and
Dr. R. D. Cameron. Much assistance was received from Mrs. Elizabeth
McDonald, Mary Mager and Susan Harper of the Civil Engineering Environ• mental Laboratory. Financial support for this work originated from the
National Research Council of Canada. CHAPTER 1
INTRODUCTION
1.1 The Sanitary Landfill
The sanitary landfill technique is currently the most widely used solid waste disposal method. The predominant use of the sanitary landfill is based on its acceptability, measured in the combined terms of time and volume effectiveness, nuisance abatement and cost. The increasing volumes of solid waste being generated today, containing more and more compounded materials of great complexity, introduce new problems for landfill solid waste disposal.
Basically, a sanitary landfill is a land area where solid waste is deposited, compacted for volume reduction, and then the deposition is covered with earth at regular time and space intervals.
Notwithstanding the simple description of the sanitary landfill
'process, there are a number of associated problems which can only be over• come by proper design, efficient operation, and control of all of the products of decomposition generated from the solid waste.
1.2 Landfill Leachate
Possibly the most serious problem caused by deposited solid waste in a landfill is the production of grossly polluted liquids from the extraneous water entering and passing through the landfill. The water entering the landfill forms solutions of the anaerobic decomposition 2
products of the solid waste in the landfill, and these solutions, generally- termed "leachates," contain both dissolved and suspended polluting substances.
1.3 Leachate Production
Landfill leachate is only produced when there is more water entering the landfill than is required to saturate the mass of the deposited solid waste. A desired function of the sanitary landfill is the effective stabilization of the organic putrescibles in the deposited solid waste; this stabilization is expedited in a moist-to-wet environment.
Totally preventing infiltration of water into the landfill would be costly and counter-productive to the stabilization process (1).
Recognizing that it may not be practical or desirable to limit all leachate production, it becomes necessary to both collect and manage the produced leachate, so that the harm caused to a receiving environment may be minimized.
1.4- Effect of Leachate on a Receiving Environment
The "insult" caused to a receiving environment by landfill leachate is widely discussed in the literature (2, 3). Qualitative and quantitative limits on specified pollutants have been set by many governmental regulatory agencies. Tables 1 and 2 are examples of regulating limits and are those set by the Pollution Control Board of the
Province of British Columbia (4-). 3
1.5 The Character of Leachate
The character of leachate has been described by many investigators
(2, 3, 5). Table 3 displays a range of values of selected leachate pollutants as given by some of these investigators.
1.6 The Purpose of This Research Project
The purpose of this research project was to evaluate the effectiveness of certain selected chemicals, combined with physical separation processes, to remove pollutants from landfill leachate; it was also decided to evaluate ozone, both as a pollution removal chemical and as an alternate disinfection medium. 4
TABLE 1
LIMITS FOR EFFLUENT PARAMETERS THAT MAY BE OF CONCERN IN SPECIFIC DISCHARGE (1)* (Ref. 4, Tab. 5-2)
Maximum Concentration (2)* Parameter mg/1 (except pH and TI^)
Level AA Level BB
Methylene Blue Active Substances 5 - Oil and Grease 15 30 pH 6.5-8.5 6.5-8.5 Phenol 0.2 0.4
TLm(96 hr.) (3) 100% 75% Aluminum (Total) 2.0 •4.0 Arsenic (Total) 0.05 0.25 Barium (Dissolved) 1.0 1.0 Boron (Dissolved) 5 5 Cadmium (Dissolved) 0.005 0.01 Chromium (Total) 0.1 0.3 Cobalt (Dissolved) 0.1 0.5 Copper (Dissolved) 0.2 0.5 Cyanide (Total) 0.1 0.5 Fluoride (Dissolved) 5 - Iron (Dissolved) 0.3 1.0 Lead (Total) 0.05 0.1 Manganese (Dissolved) 0.05 0.5 Mercury (Total) 0.0006 0.002 Molybdenum (Total) 0.2 0.5 Nickel (Dissolved) 0.3 0.5 Nitrogen (4) - - Resin Acid Soaps 5 - Selenium (Total) 0.05 0.1 Silver (Total) 0.1 1.0 Sulphate (Dissolved)(5) 50 250 Sulphide (Dissolved) 0.5 1.0 Tin (Total) 5 10 Zinc (Total) 0.5 5.0
* Bracketed numbers refer to Appendix to Table 1 which follows. 5
APPENDIX TO TABLE 1
Explanatory Notes
1. The limits apply to discharges to all receiving waters and to ground
unless otherwise noted. However, a limit will only be shown on a
permit where investigations in accordance with Section 5.12 indicate
this is needed.
2. Levels may be adjusted to take account of background levels in the
water supply. Other parameters may be added at the discretion of the
Director.
3. TL^^S hr.) samples to be prior to chlorination.
4. A limitation on nitrogen may be required where site-specific studies
indicate nitrogen to be a controlling factor for eutrophication or
where the nitrogen level of the effluent is considered to be abnormally
high.
5. Applies to freshwater only. 6
TABLE 2
RECEIVING WATER QUALITY MAINTENANCE OBJECTIVES (1)* (Ref. 4, Tab. 5-3)
PARAMETER OBJECTIVE
Dissolved Oxygen Decrease not to exceed 10%
Residual Chlorine Below detectable limits (amperometric method)
Nutrients No detectable increase in site specific productivity-limiting parameters (2)" (5)*
Coliforms-receiving waters (3)* -shellfish meat (3)*
Toxicity No increase above background (4-)*
Settleable Solids Negligible increase
Floatable Solids and Scum Negligible increase
Oil None visible on water surface
Organisms No change in productivity or development of nuisance conditions (5)*
Heavy Metals Negligible increase
* Bracketed numbers refer to Appendix to Table 2 which follows. 7
APPENDIX TO TABLE 2
Explanatory Notes
These objectives are for the maintenance of background receiving water quality, generally expressed in terms of the maximum allowable change for specified parameters. They are not applicable within the initial dilution zone as defined in this document. Other discharges may be taken into account in determining whether the allowable maximum change is to be less than any value given. Other parameters may be added by the Director.
Limiting parameters will normally be taken as phosphates and/or nitrogen forms.
In general, total coliform levels are not to exceed a median MPN of
1000/100 ml or a fecal coliform median MPN of 200/100 ml and in shellfish waters are not to exceed a fecal coliform median MPN of
14/100 ml and shellfish meats may not show a fecal coliform level greater than MPN of 230 per 100 gm. Reference may be made to British
Columbia Health Branch "Recommended Water Quality Standards" and the
"National Shellfish Sanitation Program Manual of Operation" published by the United States Department of Health, Education and Welfare.
As measured in a 96-hour TI^ static bioassay test.
Productivity refers to biological parameters which are not amenable to tabulation; however, the following nuisance conditions are typical of those to be considered:
In freshwater lakes, presence of: a) massive growths of
planktonic bluegreen algae (Cyanophyceae for more than 8
several days duration; b) massive growths of attached filamentous diatoms (Bacillariophyceae) and/or rooted aquatic plants especially near the shoreline.
In rivers and streams, presence of massive growths of attached green algae CChlorophyceae), filamentous diatoms (Bacillariophyceae) and/or rooted aquatic plants, slime-forming bacteria (as "Sphaerotilus"), sludge worms (Tubificidae) or chironomids (Chironomidae).
At sea or in estuaries, presence of sludge beds with reduced species diversity and a restricted range of predominant organisms such as "Capitella capitata." 9
TABLE 3
TYPICAL COMPOSITION OF LEACHATES (1, 5)
T
Parameter Range of Values or Concentration*
PH 3.7 8.5 Total Carbon (TC) 715 28,000 Total Organic Carbon (TOC) 256 28,000 Chemical Oxygen Demand (COD) 0 90,000 Calcium (Ca) 5 7,200 Cadmium (Cd) 0 17 Copper (Cu) 0 23.4 Iron (Fe) 0 5,500 Potassium (K) 2.8 3,770 Sodium (Na) 0 7,700 Phosphorus—Total (P) 0 130 Manganese (Mn) 0.06 1,558 Lead (Pb) 0 5 Zinc (Zn) 0 1,000 Total Solids (TS) 584 45,000 Suspended Solids (SS) 10 16,800 Dissolved Solids (DS) 584 44,900
* All values except those for pH are in Milligrams per Litre (mg/1). 10
CHAPTER 2
LITERATURE REVIEW AND EXPERIMENTAL DESIGN
2.1 Previous Research on Treatment of Landfill Leachate
The ongoing research directed to landfill leachate treatment, carried on at the University of British Columbia (l, 2, 3) and by others
(5, 6, 7) demonstrates the difficulty of developing a universal treatment for all landfill leachate. The extreme variability, in both concentration and numbers of polluting constituents in landfill leachate, is the principal cause for the treatment difficulties; to these difficulties must be added the problem of providing an adequate and nonpolluting disinfection step, to cope with the potential for bacterial and viral contamination (8) of the landfill leachate.
Poorman (2) in an investigation of anaerobic biological treat• ment of landfill leachate, found that with detention times of 5 to 20 days good removals of organics was possible; but in the case of the heavy metal pollutants, while the;."percentage reduction appeared relatively high, the effluent concentrations were still above acceptable limits (4).
Lidkea (3) found, in treating landfill leachate with peat, that adsorption of metals on the peat was high up to the adsorption capacity of the peat for any particular metal,
Uloth and Mavinic (1) treated leachate by an aerobic biological process and obtained results similar to the Poorman (2) anaerobic study but also identified some inhibition of biological activity and attributed 11
this partially to the heavy metal content. Corbett (9), using a leachate with lower concentrations of the polluting constituents than are found in most leachates, compared treating leachate by adsorption/filtering through peat and chemical treatment using lime and ferric chloride; he found both to be effective for metal removal, with no real advantage in combined chemical-peat treatment. Bioassays indicated that toxicity to fish
(rainbow trout) increased with higher pH values.
Thornton and Blanc (.5) treated leachate with alum and lime, finding that lime was much superior to alum for metal removal but neither gave satisfactory removal of BOD or COD. Chian and De Walle (6) experimented with biological and physical-chemical treatments of leachate and concluded that a combined physical-chemical-biological system was required for proper leachate treatment. Boyle and Ram (7) conducted biological and physical-chemical research on landfill leachate and reported on removals of COD, Iron, Chloride, Total Solids, pH, Alkalinity, Hardness and Color. The biological processes were more effective for BOD and COD removals, whereas chemicals provided a better removal of colour and Iron.
Chlorination is the most widely used process for the disinfection of wastewater in North America but this process is now being criticized because of the possible reaction between chlorine and the organics found
in leachate. It has been reported (10) that it is probable that every conceivable chloro-organic reaction occurs and that some of these reactions produce products that are carcinogenic. Yao (11) examined the undesirable aspects of chlorination and the advantages of using ozone as a disinfectant, but the use of ozone, as a disinfectant of leachates, is just now being researched. 12
2.2 Experimental Programme
The experimental programme was designed such that the effect of each of the chemical reagents, and the physical separation methods tested, could be statistically evaluated, both as direct single effects and as combined interacting effects. Several sequentially sized reagent dose ranges were applied, to quantify the actual range in which the reagents were most effectively reacting with the pollutants in the leachate.
Early in the experimental programme it was found that the ozone required to oxidize and consequently remove some of the metallic pollutants was part of, and intermediate to, an initial total rapid take up of the applied ozone by the leachate. "Rapid take up" of ozone as used here refers to the total ozone that is reacted before any of the ozone is carried through the leachate by the carrier gaseous oxygen.
Using this concept of "rapid take up," an attempt was made to relate this to a measurable leachate parameter and a distinguishing physical characteristic of the polluting metallics. The total chemical oxygen demand (COD) of the leachate was used as the measurable base parameter for the leachate, while for the metallic pollutants, the ratio of the ionic radius to the valence was used as the distinguishing metallic parameter.
Use of the ionic radius to valence ratio as a measure of the oxidizeability of metallics has been described by Goldschmitt (12) and by
McKenzie et al. (13). The way in which an atom or ion will react is conditioned, in part, by size (14). By plotting the ionic radius-valence ratio versus the ratio of applied ozone to leachate-contained COD, it was possible to predict an "ordered," ozone promoted, removal sequence for some of the metallic pollutants, and equally important to predict those 13
that would not be removed by practically sized ozone applications.
It was found that bacterial kill was also a function of the applied ozone-COD ratio and this was incorporated empirically into the ionic radius-valence ratio. The foregoing plot then estimates the amount of ozone required to oxidize some of the metallic pollutants and the living organisms in a leachate for which the COD is known. It should be noted that it was not intended in this research to "model" the ozone reaction or disinfection process, but only to find a working relationship between a leachate parameter, the ozone dose and the leachate-contained metallic and biological pollutants.,
Ozone is both corrosive to treatment plant and equipment and toxic to living animals and plants. These corrosive and toxic qualities, coupled with the cost of producing ozone, have constrained the use of ozone, both as a pollutant removal agent and as a disinfectant. If an effective, minimum, specific, metallic-pollutant removal and/or disinfecting
ozone dose could be fixed, so that no nonreacted ozone is produced, then much of the treatment plant toxicity containment and corrosion resistance
construction costs could be avoided; also, those ozone production costs resulting from overdosing could be minimized. 14
CHAPTER 3
GENERAL REVIEW OF PHYSICAL-CHEMICAL PROCESSES
3.1 General Process Description
In treating wastewater, any processes that do not use living organisms to effect treatment are broadly classified as physical-chemical.
Many such combinations are possible and are usually made up of several physical or chemical unit processes.
3.2 Physical Unit Processes
Physical unit processes are those treatment processes that use some physical characteristic of the wastewater contaminant or treatment mechanism to separate the contaminant from the carrying liquid. This characteristic may be density, weight, size, colour, shape or any other physical form. Some processes that use physical characteristics are: screening, mixing, flocculation, sedimentation, flotation, filtration and
induced drying (15).
3.3 Chemical Unit Processes
Chemical unit processes are those processes that use chemical reactions between an added reagent and the contaminant of the wastewater to change the chemical form of the contaminant. It may be rendered harmless in, or removed from, the carrying liquid. Examples of chemical 15
unit processes are: chemical precipitation, gas transfer, absorption, disinfection, coagulation, oxidation or reduction (15) and adsorption (16).
Most chemical unit processes require a contemporary or following physical unit process to complete the separation of the pollutant from the wastewater.
3.4 Advantages and Disadvantages of Physical-Chemical Processes
A viable physical-chemical treatment process for landfill leachate would have some inherent advantages over a biological treatment process. The most important advantages would be:
1. A quick start-up and shut-down of the process to adjust
to climatic and seasonal variability of leachate
production.
2. Physical-chemical processes are not affected by toxic
substances in the leachate.
3. Physical-chemical processes are often only nominally
temperature dependent.
4. Physical-chemical treatment processes are more readily
directed to treat and remove specific target constituents
of the wastewater than are biological treatment processes.
Some of the disadvantages of physical-chemical treatment, in comparison to biological treatment, might be:
1. Physical-chemical treatment processes generally produce
large quantities of sludges containing the removed
pollutant plus chemicals, and these sludges are often
refractory in nature, and hence not amenable to
further management. 16
2. In the chemical unit portion of a physical-chemical
treatment process, the chemical reagents are usually
added in molecular forms. The reagent molecules
disassociate into the component ions or radicals and
one of these components takes part in the treatment
reaction and is consequently removed. The other
component remains in the treated wastewater effluent
and may not be acceptable in the following use or
disposal stages of the wastewater.
3. Where satisfactory pollutant residuals could be
achieved with either physical-chemical or
biological treatment, the physical-chemical process
would probably be at a cost disadvantage. 17
CHAPTER 4
SELECTION OF REAGENT AND PROCESS CANDIDATES
4.1 Division of the Programme into Two Phases
Because of the multiplicity of physical and chemical process candidates available, it was necessary to divide the experimental programme into two phases. In this programme division, the first phase was a screening of candidates, for both physical and chemical processes; the second phase consisted of a more rigorous investigation of the treatment levels attainable by the physicals-chemical candidates emerging from the previous phase.
The dependence of the second phase on the results of the preceding screening step necessitated a preliminary analysis of the first phase results, and this format is adhered to in this report.
4.2 Chemical Reagents
A published list of chemicals (17) used for treatment of water and wastewater, shows 73 chemical reagents. Utilizing the results of some preliminary experiments and a review of the general practice reported in the literature, this large number of potential candidates was reduced to six: lime, alum, ferric chloride, ferric sulfate, powdered activated carbon and ozone.
Powdered activated carbon was only used as a reagent dose mixed
into the leachate being treated because experimentation with carbon in 18
this and other forms, such as adsorptive-filtering of leachate, was already being carried out at the University of British Columbia (3, 9).
Ozone was included mainly as an alternative disinfectant, to replace the common disinfectant chlorine; however, its effect as an overall pollutant remover was examined.
Supplemental to the six direct-acting chemicals listed above, three high-molecular-weight synthetic polymers were tested as coagulation and settling enhancers in a sixteen-experiment, statistical group. A polymer from each charge potential was chosen; anionic, nonionic and cationic, from a number supplied by manufacturers' agents. The suppliers' directions were followed for preparing and using the polymers.
4.3 Physical Unit Operations Screened
Four physical unit operations, auxiliary to the use of the chosen chemicals and polymers, were selected; these were coagulation, flocculation, sedimentation and a gas-contacting column system, to inject the ozone into the wastewater. Since development of the effectiveness of the chemical portion of the experimental programme depended heavily on the success of the physical unit process operation, several application variables such as contact time, mixing speed and the time allowed for settling were investigated in the screening design. Table 4 lists the chemical reagents and the physical parameters examined in the screening experiments, as well as the quantities or measurements used in applying these reagents and physical unit processes. 19
TABLE 4
TREATMENT VARIABLES SCREENED AND APPLIED LEVELS OF EACH, CORRESPONDING TO THE "HIGH" AND "LOW" LEVELS INDICATED IN THE SCREENING DESIGN MATRIX OF TABLE 5
Variable Variable High Level Low Level Designation ( + ) (-)
A Lime 1,000 mg/1 0 B Lime 2,000. mg/1 0 C Alum 75 mg/1 0 D Ferric Chloride 167 mg/1 0 . E Alum 125 mg/1 0 F Time of Flocculation 4-0 min 20 min G Blank - - H Speed of Flocculation 40 rpm 20 rpm I Settling Time 60 min 30 min J Sludge Recycle 10,000 mg/1 0 K Activated Carbon 50 mg/1 0 L Ferric Sulfate 250 mg/1 0 M Ozone 90 ± 30 mg/1 0 N Blank - - 0 Blank - 20
CHAPTER 5
EXPERIMENTAL DESIGN
5.1 Statistical Factorial Design
Because the purpose of this investigation involved the possible effects of a number of factors, that is, chemical reagents and the control of physical techniques in the removal of pollutants from landfill leachate, a statistical, factorially designed series of experiments was chosen as the most efficient approach.
In a statistical, factorially designed experiment, the applied variables are used at two or more levels (in this case two) and in all possible combinations with each other at the chosen levels. By an appropriate manipulation of the obtained data, for a block of experiments, the effect of each variable in causing a change in the dependent parameter can be determined. In addition to this main effect, a measure of the interaction of the applied variables may be determined, in a complete factorial design.
5.2 Fractional Factorial Design
A special case of the factorially designed experiments is a saturated fractional factorial design, which permits the investigation of up to "n - 1" applied or independent variables in "n" experiments; however, this saturated fractional design does not give an estimate of the interactions between any two applied variables. These particular designs, 21
often referred to as Placket-Burman (.18) designs are notably useful for screening applied variables (.19), that is, in determining which applied variables have a significant effect, in going from one applied level to another applied level, on a particular dependent variable. "Significant effect," as used here, means an effect greater than the variations that appear in any experimental work due to errors or manipulative causes.
A saturated, fractional design matrix is shown in Table 5 for
"n" = 16 experiments. This is the screening design used, and by using only 12 of the 15 possible treatment variables, the data manipulations for the unused treatment variable positions may be used to provide an estimate of the variance and the standard deviation.
In the design matrix shown in Table 5, the pluses (+) and minuses (-) (in the columns under the applied variables designations) indicate the particular high and low levels respectively, for the applied variables in each of the rows of runs or individual experimental tests, numbered 1 to 16 in the left-hand column. Shown in Table 4, in addition to the variables, are the Variable Designations and the high and low of the applied variables used in the screening experiments. Because of the importance of lime and alum indicated in the literature, these were included as two separate variables, each with the consequent four applied levels and all combinations of those levels.
In the screening experiments, twelve polluting characteristics or dependent variables of the leachate were measured before and after treatment, for each of the sixteen experimental runs. These twelve dependent variables are listed in Table 6, as are the concentrations or value of that dependent variable in the particular untreated leachate.
The experiments were performed in random order and the response measured 22
TABLE 5
PACKET-BURMAN DESIGN FOR DETERMINING THE EFFECT OF 15 VARIABLES, AT TWO LEVELS EACH, USING 16 RUNS
MATRIX FOR SCREENING DESIGN
APPLIED VARIABLES
RUN NO. A B C D E F G* H I J K L M N* 0*
1 + + + t - + - + + - - + - - -
2 + + + - + - + + - - + - - - +
3 + + - + - + + - - + - - - + +
4 + - + - + + - - + - - - + + +
5 - + - + + - - + - - - + + + +
6 + + + - - + - - - + + + + -
7 - + + - - + - - - + + + + - +
8 + + - - + - - - + + + + - + -
9 + - - + - - - + + + + - + - +
10 - - + - - - + + + + - + - + +
11 - + - - - + + + + - + - + + -
12 + - - - + + + + - + - + + - -
13 - - - + + + + - + - + + - - +
14 - - + + + + - + - + + - - + -
15 - + + + + - + - + + - - + - -
16 + + + + - + - + + - - + - - -
Note: For the purpose of the project, 12 variables represent real changes in the level of the variables, while 3 variables, marked with an asterisk (.*) are dummy variables used to estimate experimental error (19). TABLE 6
POLLUTANTS MEASURED IN THE SCREENING PROCESS
PH 5.03 Iron (Fe) 441
Turbidity (turb) 60 Calcium (Ca) 560
Total Carbon (TC) 7,380 Potassium (K) 270
Total Solids (TS) 8,600 Sodium (Na) 370
Cadmium (Cd) 0.035 Phosphorus (P) 15.10
Zinc (Zn) 32.5 Copper (Cu) 0.043
Dependent variables (pollutants) measured in the leachate for the experimental block of 16 screening experiments. Values shown are in mg/1 except for pH, which is in pH units, and turbidity, in Hach formazin turbidity units, and are the values of each variable in untreated leachate. 24
for each dependent variable, that is, the residual in the treated leachate was measured by appropriate laboratory analytical techniques(20). The response measurements, for the screening experiments, are displayed in
Table 7.
5.3 Calculation of Effects
Calculating the net average effect and its statistical significance, in going from the low level to the high level of any of the applied independent variables, were the next two steps. For each of the designated, independent applied variables, that is, applied reagents or unit process level, the net effect is the difference between the average of the sum of the dependent responses obtained at the high level applied and that obtained at the low applied level. For example, the effect of
"variable A (lime)" on the dependent variable "turbidity" is:
T,r.r. £ Responses at "( + )" Z Responses at "(-)" EffectA = No. Responses at "(+)" No. Responses at "(-)"
Therefore, from Tables 5 and 7, the effect of lime (A) on turbidity is given by:
. vV 95 + 66 + 40 t 120 + 100 + 24 + 76 + 55 Effect (Turb)=
78 + 104 + 60 + 93 + 45 + 72 + 106 + 60
5.25 Hach Turbidity Units, TABLE 7
FOUND VALUES OF POLLUTANTS MEASURED IN THE SCREENING EXPERIMENTS
DEPENDENT VARIABLE
RUN NOS. PH Turb TC TS Cd Zn Fe Ca K Na P Cu
1 8.05 95 6,420 12,279 0.029 1.08 • 27.9 900 257 360 0.625 0.043 2 8.50 66 6,374 12,642 0.029 1.17 13.5 625 240 336 2.975 0.042 3 8.45 40 6,480 12,876 0.018 1.07 9.4 775 242 330 0.82 0.036 4 5.55 120 6,480 10,559 0.042 38.0 137.5 880 249 359 11.44 0.054 5 7.40 78 6,360 12,146 0.030 3.13 37.5 700 248 399 16.20 0.049 6 5.60 100 5,975 10,428 0.064 33.75 175.0 525 249 358 10.80 0.070 7 6.70 104 6,620 12,326 0.035 16.5 105.0 750 256 351 7.28 0.071 8 9.11 24 6,930 12,797 0.031 0,72 3.5 752 243 326 0.375 0.030 9 5.06 76 6,540 10,965 0.039 32.25 250 575 257 350 11.70 0.065 10 5.09 60 7,200 8,769 0.041 40.75 440 580 270 365 16.20 0.051 11 6.93 93 6,330 12,032 0.037 14.5 43.75 990 225 220 3.90 0.057 12 5.55 55 6,550 10,701 0.041 30.25 150 537 248 353 5.25 0.040 13 5.00 45 6,785 9,251 0.042 33.75 457 490 267 360 15.00 0.130 14 5.00 72 7,160 9,005 0.048 32.5 475 350 266 370 16.20 0.057 15 6.16 106 6,780 11,793 0.031 25.0 16.705 675 248 351 9.60 0.041 16 5.03 60 7,380 8,598 0.035 32.5 441 560 270 370 15.10 0.043
Note : The above represent the found values of dependent variables measured in treated leachate for the 16 screening runs. All values are in mg/1 except for pH and turbidity which are in pH units and Hach formazin turbidity units respectively. 26
This states that in going from the low level of "A" (lime) to the high level of "A" (lime), 0 and 1,000 mg/1 respectively, the turbidity is decreased 5.25 Hach units. As will be shown later, this change in turbidity is less than the estimated standard error (deviation) and there• fore not deemed significant; however, it illustrates the calculation methodology.
5.4 Calculation of the Standard Deviation
The data accompanying Figure 1 (shown below the figure) is a six-column table and from the left these columns represent:
1. The rank or order number of the calculated effect
2. The symbol name of the independent variable
3. The absolute value of the calculated effect
4. The technically corrected value of Z, the area
under a normal curve for a half-normal distribution (21)
5. The absolute value of the effect multiplied by the
Z value, and finally,
6. The square of the Z values.
This presentation permits a ritualistic calculation of the standard error or deviation of the effects from the formula (21, 22)
E(Value)(Z)
It is to be noted that the standard deviation of the responses may be determined from the unused or dummy columns (17) where: 27
0 2 4 6 8 10 II 12 13 14
ORDER NUMBERS
ORDER EFFECT ABSOLUTE 2 (VALUE HZ) (Z) NUMBER NAME VALUE z
1 H 0.50 0.079 0.0395 0.0062 2 D 2.00 0.158 0.3160 0.0250 3 B 2.25 0.239 0.5377 0.0571 4 N 2.50 0.322 0.8050 0.1037 5 0 3.75 0.408 1.5300 0.1665 6 K 4.25 0.496 2.1080 0.2460 7 A 5.25 0.589 3.0922 0.3469 8 I 5.50 0.688 3.7840 0.4733 9 F 6.75 0.794 5.3595 0.6304 10 E 7.75 0.910 7.0525 0.8281 11 G 8.00 1.040 8.3200 1.0816 12 L 9.00 £32.9444 Z3.9648 13 J 15.00 14 C 31.50 Z(VALUE)(Z)
15 s - 2 M 33.75 £(Z )
- 32•944 ~ 3.9648 = 8.31 Figure 1. Half-normal plot of the screening data for turbidity with related tabulated example of the standard deviation calculation. 28
_ C2 + N2 + O2 S 3 , (2)
where C, N, and 0 are the effects of the dummy variables. The difference in the estimate of the standard deviation, by the two calcula• tions , is not sufficient to alter the end result.
5.5 Determining the Significance of the Effects
Using the method proposed by Daniel (23) and modified by Zahn
(21, 22) for determining the significant effects in a single replication factorial experiment, the calculated absolute values of the effects are plotted versus the corresponding order number of the ranked effects. The scale of the vertical axis, on which the effect values are plotted, is in multiples of the estimated standard deviation, while on the horizontal axis, the ranked order numbers are plotted at their corrected ( 21) half-normal percentiles. Included on the plotting grid are so-called
"Guard Rails" (21, 23), marking off the 60%, 80% and 95% confidence limits used to detect the significance of the larger effects, that is, those effects that do not fall on. the normal expected positions for nonsignificant effects. The normally expected positions of the nonsignificant effects are indicated by the diagonal line beginning at the origin.
For the screening experiments (runs 1-16), the half-normal plot
of the independent variable effects on turbidity are shown in Figure 1.
In Figure 1 the significant effects (the effects above the 95% confidence
limit), are the ones caused by M"(ozone) and C (alum). However, both
effects M and C were calculated positive values, thus indicating that 29
ozone, and alum contribute to increasing turbidity. The effect of
J (sludge recycle) was calculated as a negative effect, thereby diminishing turbidity, but the probability of sludge recycle being a real effect, and lowering turbidity, is low, somewhere in the order of 65%, since it falls only slightly above the 60% confidence limit "Guard Rail."
Figures 1 through 12, with the accompanying effect data and standard deviation calculation, show the plotting for significance of the
"calculated effect" data, derived from the raw data of Table 7, for the
sixteen screening experiments.
Table 8 is a compilation of the leachate characteristics which were significantly effected by the chemical and physical treatments applied. From this table, it is noted that only lime and ozone are
effective in reducing some of the monitored pollutants, while alum and
ferric sulfate had a real, but negative, effect on one characteristic each.
Nevertheless, the latter two reagents were included in the follow-up
experimentation because of their common usage in water and wastewater
treatment. 30
ORDER NUMBERS
ORDER EFFECT ABSOLUTE z (VALUE HZ) (Z)2 NUMBER NAME VALUE
1 J 0.0500 0 .079 0.00395 0.006241 2 H 0.0650 0 .158 0.01270 0.024964 3 I 0.0925 0 .239 0.02211 0.057121 4 E 0.1025 0 .322 0.03300 0.103684 5 D 0.1075 0 .408 0.04385 0.166464 6 G 0.1450 0 .496 0.07192 0.246016 7 K 0.1450 0 .589 0.08541 0.346921 8 D 0.1500 0 .688 0.10320 0.473344 9 F 0.1575 0 .794 0.12806 0.630436 10 L 0.1600 0 .910 0.14550 0.828100 11 C 0.3025 1 .040 0.31450 1.081600 12 N 0.3175 E0.96420 E3.964891 13 M 0.5925 . 14 A 1.1375 E(VALUE)(Z) 15 B 2.3600 s : E(Z2)
3.964891 = 0.24
Figure 2. Half-normal plot of the screening data for pH with related tabulated example of the standard deviation calculation. 31
0 2 4 6 6 10 II 12 13 14 15
ORDER NUMBERS
ORDER EFFECT ABSOLUTE z (VALUE HZ ) (Z)2 NUMBER NAME VALUE
1 C 43.375 0.079 3.43 0.006241 2 E 5.9.375 0.158 9.38 0.024964 3 H 63.875 0.239 15.27 0.057121 4 N 68.875 0.322 22.18 0.103684 5 I 71.875 0.408 29.33 0.166464 6 0 87.625 0.496 43.46 0.246016 7 L 87.625 0.589 51.61 0.346921 8 F 92.125 0.688 63.38 0.473344 9 K 118.625 0.794 94.19 0.630436 10 D 170.125 0.910 154.81 0.828100 11 G 177.125 1.040 184.21 1.081600 12 B 221.875 £671.25 £3.964891 13 J 570.625 14 A 359.875 £(VALUE)(Z) = 15 M 386.875 s E(Z2)
_ 671.25 ~ 3.964891
- 169.3
Figure 3. Half-normal plot of the screening data for total carbon with related tabulated example of the standard deviation calculation. 32
0 2 4 6 8 10 II 12 13 14 15
ORDER NUMBERS
ORDER EFFECT ABSOLUTE z (VALUE HZ) (Z)2 NUMBER NAME VALUE
1 L 0.063125 0.079 0.0049 0.006241 2 H 0.268125 0.158 0.0244 0.024964 3 I 0.724375 0.239 0.1731 0.057121 4 C 0.783125 0.322 0.2521 0.103684 5 K 0.939375 0.408 .3832 0.166464 6 J 1.013125 0.496 .5025 0.246016 7 N 1.111875 0.589 .655 0.346921 8 M 1.173125 0.688 .807 0.473344 9 E 1.265625 0.794 1.005 0.630436 10 G 1.858125 0.910 1.690 0.828100 11 0 2.406875 1.040 2.503 1.081600 12 F 2.740625 LB. 019372 L3.964891 13 D 3.64375 14 A 6.998125 £(VALUE)(Z) 15 B 7.553125 s E(Z2)
8.019372 3.964891 = 2.02
Figure 4. Half-normal plot of the screening data for phosphorus with related tabulated example of the standard deviation calculation. 33
0 2 4 6 8 10 II 12 13 14 15
ORDER NUMBERS
ORDER EFFECT ABSOLUTE 2 Z (VALUE HZ) (Z) NUMBER NAME VALUE
1 0 0.636 0.079 0.050165 0.006241 2 K 0.665 0.158 0.09975 0.024964 3 C 0.680 0.239 0.16252 0.057121 4 J 0.711 0.322 0.228942 0.103684 5 E 0.793 0.408 0.323594 0.166464 6 I 0.839 0.496 0.416144 0.246016 7 H 0.857 0.589 0.504773 0.346921 8 N 0.874 0.688 0.601312 0.473344 9 G 0.893 0.794 0.709042 0.630436 10 D 0.917 0.910 0.83447 0.828100 11 M 0.924 1.040 0.96096 1.081600 12 F 0.982 1.191 £4.891622 £3.964891 13 A 2.042 1.376 14 B 3.451 1.626 E(VALUE)(Z) S - —r 15 L 4.035 2.051 Z(Z2)
4.891622 3.964891 = 1.23
Figure 5. Half-normal plot of the screening data for total solids with related tabulated example of the standard deviation calculation. 34
0 2 4 6 6 10 II 12 13 14 15
ORDER NUMBERS
ABSOLUTE 2 ORDER EFFECT z (VALUE KZ) (Z) NUMBER NAME VALUE
1 I 0.0000625 0 .079 0.049375 X 10 - 4 0.006241 2 H 0.0016875 0 .158 2.666 X 10 - 4 0.024964 3 A 0.0018375 0 .239 4.391625 X 10 - 4 0.057121 4 J 0.0019375 0 .322 6.23875 X 10 - 4 0.103684 5 D 0.0022125 0 .408 9.027 X 10 - 4 0.166464 6 E 0.0023125 0 .496 11.47 X 10 - 4 0.246016 7 0 0.0025875 0 .589 15.240375 X 10 - 4 0.346921 8 N 0.0025875 0 .688 17.802 X 10 - 4 0.473344 9 G 0.0027875 0 .794 22.13275 X 10 - 4 0.630436 10 F 0.0027875 0 .910 25.36625 X 10 - 4 0.828100 11 L 0.0032875 1 .040 34.19 X 10 - 4 1.081600 12 K 0.0062125 1148.57438 x 10 - 4 E3. 964891 13 C 0.0065875 14 M 0.0066625 Z(VALUE)(Z) 15 B 0.0130625 s — Ul2)
148.57438 x 10 - 4 3.964891 = 0.0037
Figure 6. Half-normal plot of the screening data for cadmium with related tabulated example of the standard deviation calculation. 35
0 2 4 6 8 10 II 12 13 14 15
ORDER NUMBERS
ORDER EFFECT ABSOLUTE Z (VALUE HZ) (Z)2 NUMBER NAME VALUE
1 M 0.000625 0.079 0.000049 0.006241 2 E 0.003375 0.158 0.000533 0.024964 3 C 0.005125 0.239 0.001224 0.057121 4 N 0.006375 0.322 0.002052 0.103684 5. H 0.006375 0.408 0.002601 0.166464 6 L 0.008500 0.496 0.004216 0.246016 7 G 0.009375 0.589 0.0055287 0.346921 8 F 0.009625 0.688 0.006622 0.473344 9 I 0.010375 0.794 0.00823775 0.630436 10 0 0.012125 0.910 0.0113375 0.828100 11 A 0.012325 1.040 0.012818 1.081600 12 J 0.014625 ZO.05491056 £3.964891 13 D 0.015375 14 K 0.018250 E(VALUE)(Z) s 15 B 0.020125 2 Z(Z )
0.05491056 3.964891
= 0.014
Figure 7. Half-normal plot of the screening data for copper with related tabulated example of the standard deviation calculation. 36
ORDER NUMBERS
EFFECT ABSOLUTE 2 ORDER z (VALUE )(Z) (Z) NUMBER NAME VALUE
1 0 0.210 0 .079 0.01659 0 006241 2 F 0.4525 0 .158 0.071495 0 024964 3 K 0.580 0 .239 0.13862 0 057121 4 D 1.2325 0.32 2 0.396865 0 103684 5 E 1.2350 0 .408 , 0.50388 0 166464 6 N 1.260 0 .496 0.62496 0 246016 7 L 2.3825 0 .589 1.4032925 0 346921 8 G 2.6950 0 .688 1.85416 0 473344 9 J 2.8950 0 .794 2.29863 0 630436 10 H 3.2075 0 .910 2.918825 0 828100 11 I ' 4.6475 1 .040 4.8334 1 081600 12 C 4.803375 £15.060717 £3 964891 13 M 6.4800 14 A 7.2925 £(VALUE)(Z)
15 B 26.560375 s 2 £(Z )
_ 15.060719 3.964891 = 3.8
Figure 8. Half-normal plot of the screening data for zinc with related tabulated example of the standard deviation calculation. 37
0 2 4 6 8 10 II 12 13 14 15
ORDER NUMBERS
ORDER EFFECT ABSOLUTE z ( VALUE )(Z) (Z)2 NUMBER NAME VALUE 1 0 10.75 0.079 0.84925 0.006241 2 c 11.75 0.158 1.8565 0.024964 3 H 18.85 0.239 4.48125 0.057121 4 L 24.50 0.322 7.889 0.103684 5 G 33.75 0.408 13.770 0.166464 6 N 56.25 0.496 27.90 0.246016 7 A 59.25 0.589 34.89825 0.346921 8 K 68.75 0.688 47.30 0.473344 9 M 75.00 0.794 59.55 0.630436 10 E 80.75 0.910 73.4825 0.828100 11 J 84.50 1.040 87.880 1.081600 12 F 85.00 E359.85675 E3.964891 13 D 85.50 14 I 127.50 E(VALUE)(Z) 15 B 208.75 s - E(Z2) _ 359.85675 3.964891 = 90.76
Figure 9. Half-normal plot of the screening data for calcium with related tabulated example of the standard deviation calculation. 38
0 2 4 6 6 10 II 12 13 14 15
ORDER NUMBERS
ORDER EFFECT ABSOLUTE Z (VALUE )(Z) (Z)2 NUMBER NAME VALUE
1 0 0.125 0 .079 0.009875 0.006241 2 F 0.625 0 .158 0.09875 0.024964 3 E 0.625 0 .239 0.149375 0.057121 4 J 0.875 0 .322 0.28175 0.103684 5 C 1.875 0 .408 0.765 0.166464 6 L 2.625 0 .496 1.302 0.246016 7 I 2.875 0 .589 1.693375 0.346921 8 K 3.875 0 .688 2.666 0.473344 9 L 4.125 0 .794 3.27525 0.630436 10 H 4.125 0 .910 3.75373 0.828100 11 A 5.625 1 .040 - 5.8500 1.081600 12 D 6.625 119.845125 £3.964891 13 N 9.125 14 G 9.375 E(VALUE)(Z) 15 B 12.125 s — Ul2)
_ 19.845125 3.964891
= 5.0
Figure 10. Half-normal plot of the screening data for potassium with related tabulated example of the standard deviation calculation. 39
0 2 4 6 8 10 II 12 13 14 15
ORDER NUMBERS
ORDER EFFECT ABSOLUTE z ( VALUE HZ) (Z)2 NUMBER NAME VALUE
1 A 1.41 0.079 0.11139 0.006241 2 J 4.25 0.158 0.6715 0.024964 3 0 5.25 0.239 1.25475 0.057121 4 E 6.25 0.322 2.0125 0.103684 5 F 6.50 0.408 2.6520 0.166464 6 H 9.50 0.496 4.7120 0.246016 7 I 9.50 0. 589 5.5955 0.346921 8 M 9.50 0.688 6.5360 0.473344 9 L 10.75 0.794 4.5355 0.630436 10 D 12.25 0.910 11.1475 0.828100 11 G 14.00 1.040 14.5600 1.081600 12 K 14.50 £57.7864 £3.964891 13 N 14.75 14 C 17.75 £(VALUE)(Z)
s 2 15 B 26.50 £(Z )
57.7864 3.964891 = 14.57
Figure 11. Half-normal plot of the screening data for sodium with related tabulated example of the standard deviation calculation. 40
0 2 4 6 8 10 II 12 13 14 15
ORDER NUMBERS
ORDER EFFECT ABSOLUTE z (VALUE KZ)
1 G 1.8875 0 .079 0.1491 0 006241 2 0 3.3875 0 .158 0.5352 0 024964 3 E 5.4875 0 .239 1.3115 0 057121 4 H 8.1125 0 .322 2.6122 0 103684 5 I 14.487 5 0 .408 5.9109 0 166464 6 K 14.7625 0 .496 7.3222 0 246016 7 F 16.1375 0 .589 9.5050 0 346921 8 C 17.8875 0 .688 12.3066 0 473344 9 L 18.4875 0 .794 14.6791 0 630436 10 D 32.3625 0 .910 29.4499 0 828100 11 J 34.2375 1 .040 35.6070 1 081600 12 N 61.8620 1119.3887 964891 13 M 99.3625 14 A 175.7625 £(VALUE)(Z) B 265.3625 s - 15 £(Z2)
3.964891
= 30.1
Figure 12. Half-normal plot of the screening data for iron with related tabulated example of the standard deviation calculation. 41
TABLE 8
COMPILATION OF STATISTICALLY SIGNIFICANT EFFECTS FOR INDEPENDENT VARIABLES IN THE SCREENING EXPERIMENTS
EXPERIMENT DESCRIPTION LEACHATE CHARACTERISTIC SIGNIFICANTLY AFFECTED BY CHANGE IN LEVELS OF TREATMENT VARIABLES
Statistical Group 1
Runs #1-16 (Screening)
Treatment Variables
Variable High" Low* Level Level
Lime 1000 0 pH, P, Fe
Lime 2000 0 pH, P, Cd, Zn, Fe
Alum 200t 0 Turb.**
Ferric Chloride 167 0
Ferric Sulfate 200 0 TS**
Activated Carbon 50 0
Sludge Recycle 50 0 Turb.
Ozone 50 ± 10 0 pH***, pA**9 Turb.**, Fe***
Time for Flocculation 40 Min 20 Min
Settling Time 60 Min 30 Min
Speed for Flocculation 40 RPM 25 RPM
* Mg/1 unless otherwise shown. ** Significantly increased this characteristic in effluent. "f* This is value for combined high levels. *** Of low significance. 4-2
CHAPTER 6
EXPERIMENTAL APPARATUS AND ANALYTICAL METHODS
The components of the apparatus assembled to conduct the experimental programme consisted of two main units, the "ozone generation and contacting" system assembly, and the "physical unit processes simulation" system assembly.
6.1 Ozone Generating and Contacting System
A schematic flow diagram of the ozone generation and contacting system is shown in Figure 13. For ozone generation, a Grace Laboratory
Generator was used. This type of ozone generator produces ozone, from the oxygen in air or from pure oxygen, by passing these gases between electrodes with an alternating high-voltage difference. A uniform glow discharge, commonly called a silent discharge, is maintained in the gas by inserting a dielectric between the electrodes. Only oxygen was used in this study; this was zero grade (hydro-carbons less than 5 ppm) commercial oxygen supplied from a pressure cylinder.
The flow rate of the ozone-oxygen mixture stream from the ozone, generator was controlled and proportioned into two parts, by a set of three rotameters. One part went directly into a.potassium-iodide trap for the analysis of the ozone content, followed by volume measurement via a wet-test volume meter. The second part was introduced into a 1.37 meter high by 9.5 centimeter inside diameter polished lucite cylinder, containing CONTACT CYLINDER
WET TEST METER
OZONE OZONE —r> DETERMINATION OF GENERATOR OZONE IN OFF - OXYGEN STREAM OXYGEN
WET TEST K.I.TRAP .METER DETERMINATION OF OZONE IN OZONE- OXYGEN STREAM LEACHATE RECYCLE PUMP 0 Control Valves
FIG.I3'SCHEMATIC OF OZONATING SYSTEM CO 44
the sample of leachate to be ozonated.
The ozone-oxygen stream was dispersed into the leachate through
a fine-porosity fritted gas dispersion tube, mounted near the bottom of
the lucite contact cylinder. The leachate in the cylinder was recycled
at a constant rate of 1.5 liters per minute, counter-current to the gas
flow; this was performed mainly to provide a foam dispersion spray on the
top surface of the leachate in the cylinder.
The gas stream exiting the contact cylinder was led to a second
potassium iodide trap and then to a wet-test volume meter assembly, to measure the ozone content and volume of the exiting gas. It should be
noted that all experiments were conducted with no ozone escaping the
contact chamber, indicating that all of the ozone being applied reacted
in the leachate. The foregoing was excepted in one run that was carried
through to the point where a breakthrough, of unreacted ozone, was noted;
this breakthrough caused a discolouration of the contents of the potassium
iodide trap.
6.2 Physical Unit Processes Simulation
The physical unit processes simulation was made using two
standard, six-paddle laboratory stirring devices, commonly called "jar test
apparatus." The apparatus allows rapid mixing during and after the
addition of reagents and then the stirring paddles may be slowed to any
chosen speed, thus permitting the coagulation and flocculation of the
precipitate or floe formed. The specific apparatus used was manufactured
by Phipps and Bird. 45
6.3 Analytical Methods
Measurement of the characteristics of the raw leachate, used in this investigation, was made by the staff of the Environmental Engineering
Laboratory, Department of Civil Engineering, University of British Columbia.
These measurements were in accordance with procedures of Standard Methods
(20), with minor modifications as noted in the reference by McDonald and
Cameron (24). Bacterial counts on ozonated leachate were determined using procedures that are described in the following Section 6.5.
The "after treatment" characteristics were measured using the same procedures as for the raw leachate and these procedures are briefly described in the following:
pH - All determinations were made with a Fisher
accumet pH Meter, Model 210.
Turbidity - The turbidity was measured with a
nepholmeter procedure (20), using a Hach
Turbidimeter, Model 2100A.
Colour - The colour was determined using a Helige
Aqua Tester in accordance with the
manufacturer's specifications.
Solids - Solids determinations were made using methods
described in Standard Methods (20).
Metallic Ions - The metallic-ion species Cd, Ca, K, Na, Cu,
Mn and Zn were determined on a Jarrel-Ash
Model 82-516, Atomic Adsorption
Spectrophotometer. The method employed 46
direct aspiration with both concentrated
and nonconcentrated samples of leachate,
as appropriate, for the quantity of
contained metallic ion.
Total Carbon The carbons were analyzed by the
and Inorganic procedures of Standard Methods (20),
Carbon using a Beckman Model 915, coupled
total-carbon and inorganic carbon analyzer.
Chemical Oxygen COD was determined by the "Dichromate
Demand Method" of Standard Methods (20).
Ozone Ozone was determined by the "Idiometric"
procedure, as outlined in Standard Methods
(20).
6.4 Disinfection with Ozone
The literature contains numerous references and information establishing the effectiveness of ozone as a viral and bacterial disinfectant. Bringman (25) states that, in tests carried out, ozone was
600 to 3,000 times more rapid than chlorine in bacterial disinfection.
Ingols and Fetner (26) conclude that bacterial kill by chlorine is progressive, as compared to ozone which is sudden and.'total,rafter a
"threshold" dose has been applied. Because of this established disinfection ability of ozone, only a limited confirmatory evaluation of the disinfection by ozone was planned into this experimental project; the main emphasis was on determining the dose at which bacterial kill was accomplished. 1+7
6.5 Ozone Disinfection Procedure
Standard Plate Counts at 35°C using Plate Count Agar (Tryptone
Glucose Yeast Agar) (20) were made on a series of nondiluted samples of ozonated leachate. Each sequential sample, numbered from 1 to 9, had an increasing ozone dose ranging from 0 mg/1 to 163 mg/1. Following this sequentially increasing ozone dose test, 9 Standard Plate Counts at 35°C were made, using leachate samples ozonated with a common ozone dose of
110 mg/1 each; 5 of these samples were undiluted and 4 were diluted 1-10, with Stock Buffer Solution (20). All plate counts were made using a Quebec colony counter. Recording of Plate Counts were in accordance to the procedures of Standard Methods (20). 48
CHAPTER 7
PRESENTATION AND DISCUSSION OF DATA
7.1 Data—Screening Experiments
Table 4 shows the applied dose levels of the reagents screened, as well as the parameters of the physical unit operations screened.
Table 6 lists the dependent variables (pollutants) measured in the treated leachate, and also shows the original concentration of the monitored pollutants in the untreated leachate. Table 7 gives the residual concentration of each of the monitored pollutants in the treated leachate from the screening experiments.
7.2 Discussion of Screening Data
The detailed method of manipulating the raw data is presented in
Chapter 5 of this paper. The calculated independent effect data, accompanying Figures 1 through 12, is plotted in the figures to determine those effects that are statistically significant.
Because the low level of the applied reagent doses was a zero dose, the calculated effect, caused by applying the reagent at the high level, is a close approximation of the real removal caused by the named reagent at the high level applied. This approximate real effect of the particular dose is noticeable even when a reagent is applied as two separate doses. This separation of dose effect may be noted, in the screening experiments, in the application of lime. In Figure 2, where the dependent variable is pH, the calculated effect of increasing the lime dose 49
from 0 mg/1, low-level dose, to 1000 mg/1, high-level dose, is to raise the pH by 1.1375 pH units, while the calculated effect of increasing the lime dose from 0 mg/1 to 2000 mg/1 is 2.360 pH units. This ability of the statistically designed experiment to estimate the effect of a particular reagent or reagent dose is a useful datum. An example of one of these useful data observations is illustrated in Figure 6, where it is shown that the dependent variable Cadmium is not significantly removed using a
1000 mg/1 lime dose but is significantly removed by a lime dose of 2000 mg/1.
The results, derived from the plots in Figures 1 to 12, are tabulated in Table 8 and can be summarized for each of the applied independent variables as follows:
Lime. Lime was shown to have a significant potential for decreasing the concentration of three of the monitored pollutants, P, Zn, and Fe, while the increase in total solids, attributable to lime, approached a significant level. Lime effected a change in pH, raising the pH from the original value of 5.03 up to 9.11, depending on the quantity applied and the interacting effect of other reagents used at the same time.
Ozone. Ozone was shown to effect a reduction in pH and Fe.
Turbidity was shown to increase from the ozone application. The confidence estimate for the reduction in pH by ozone was approximately 90 percent.
The found reduction in pH differs'-from the findings of other investigators
(27), who found that in ozonating wastewaters, the wastewater pH consistently changes towards neutrality, pH 7, during the ozone treatment.
In this set of experiments, the wastewater was ozonated at an original pH of 5.03. To be consistent with the previously reported work, the pH should 50
have been increased towards pH 7 by the ozone treatment• The following lime addition increased the pH to well above pH 7 but the calculated effect for ozone shows a net pH reduction. No explanation for this anomaly can be made at this time.
Alum. Alum had one significant effect, namely to increase the turbidity of the leachate.
Ferric Sulfate. Ferric sulfate increased the total solids content of the treated leachate, when compared to leachate treated without using ferric sulfate.
Sludge Recycle. Slude recycle was possibly effective in reducing turbidity but the probability for this was low, about 60 percent, as demonstrated in the Figure 1 plot.
None of the other applied variables, reagents or physical unit processes were found to effect a significant change in the quantity or quality of any of the leachate characteristics measured.
Lime and ozone became the prime reagent candidates for the follow-up research, from the results of the screening experiments. Alum and ferric sulfate were included in the follow-up work because of the near universal acceptance of these reagents as useful water and wastewater treatment chemicals. The low significance of the single, sludge-recycle effect precluded sludge recycle as a useful treatment variable.
7.3 Post-Screening Experimental Data
Tables 9 to 13 display the doses of applied reagents and the order of reagent application for the 11 groups of experiments (group numbers 2 to 12) in the post-screening experimentation. For continuity, 51
the information for the "screening experiments" is included in these tables as group number 1.
The leachate characteristics affected by increasing any specific reagent used from a low-level dose to a higher-level dose are also shown in these tables. Table 14- lists the name code for each of the independent variables (reagents) used in the follow-up experimentation.
Tables 15 to 24 show the original concentration, the high, low and mean of the residual concentrations, the standard deviation of the residuals and the percent of the original concentrations that were removed in the best removal (lowest residual) during the treatment for each of the
19 characteristics that were monitored.
Table 26 shows the best (lowest) values for the selected pollutants in the treated leachate with the treatment reagents and the effective reagent'dose or dose range indicated.
Tables to , in the appendix to this report, are compilations of the residual measured concentrations of the monitored leachate polluting characteristics, for all of the post-screening experimental runs, and is the raw data from which the previous tables were developed.
The found values for the post-screening experiments were statistically and numerically manipulated, with variants to suit the number of applied reagents and the data available, in the same manner as detailed in Chapter 5 for the screening experiments. For example, for the experimental groups numbers 2, 4 and 10, the experimental design used was one in which 4 independent variables (reagents) were tested in all possible combinations of two levels of application in 16 runs or separate experiments. Table 25 is an illustration of the computational matrix used 52
TABLE 9
COMPILATION OF REAGENT DOSING LEVELS FOR GROUPS 1,2, AND 3 WITH SIGNIFICANT POLLUTING CHARACTERISTIC SHOWN WHERE APPLICABLE
EXPERIMENT DEFINITION LEACHATE CHARACTERISTIC EFFECTED
Statistical Group 1
Runs #1-16 (Ozonation First) Treatment Variables Lime 0 mg/1 - 1000 mg/1 pH, P, Zn, Cd, Fe 0 mg/1 - 2000 mg/1 . Alum 0 mg/1 200 mg/1 Turbidity*
Fe2(S04)3 0 mg/1 - 200 mg/1 TS*
Ozone 0 mg/1 - 50 mg/1 pH**, Turbidity*", Fe**
Sludge Recycle 0 mg/1 - 50 mg/1 Turbidity**
Statistical Group 2
Runs #17-32 (Ozonation First)
Lime 1200 mg/1 - 2000 mg/1 pH, Turbidity**, SS*,**, Mn, Zn
Alum 25 mg/1 - 125 mg/1
Fe2(S04)3 25 mg/1 - 125 mg/1
Ozone 25 mg/1 - 107 mg/1
Runs 19, 21, 24, 25, 26, 28 of this group not completed due to loss of treated leachate sample
Statistical Group 3
Runs #33-36
Four replicate runs not completed as in Group 2
* Indicates effect was an increase ** Indicates effect was of low statistical significance 53
TABLE 10
COMPILATION OF REAGENT DOSING LEVELS FOR GROUPS 4, 5 AND 6 WITH SIGNIFICANT POLLUTING CHARACTERISTIC CHANGES SHOWN WHERE APPLICABLE
EXPERIMENT DEFINITION LEACHATE CHARACTERISTIC AFFECTED
Statistical Group 4
Runs #37-52 (Ozonation First)
Treatment Variables
Lime 1200 mg/1 - 2000 mg/1 TC*, TS*, TOC*, Colour, SS, Fe, Mn pH*, DS, Zn Alum 30 mg/1 - 150 mg/1 TC
Fe2(S04)3 30 mg/1 - 150 mg/1
Ozone 51 mg/1 - 98 mg/1 TC, TS, TOC, Colour, SS, COD, Mn, Turbidity, pH, DS, Cu
(1) Statistical K J Group 5
Runs #53-56 ^ (Ozonation First)
Lime 1600 mg/1 - 2000 mg/l(2) pH, Turbidity, Colour, TC*, TS*, SS, Pb*, Zn, Fe, Ca*, Mn Alum 90 mg/1
Fe2(S04)3 90 mg/1
Ozone 43 mg/1
Statistical Group 6
Runs #57-61 (Ozonation First)
Lime 2460, 2630, 2790, 2870 and 3140 mg/1 (3)
Alum 71 mg/1
Fe2(SOl|)3 169 mg/1
Ozone 104, 111, 115, 119, 126(3)
* Indicates effect was an increase. Note (1) Runs 53-55 were replicate runs with the lime dose at 1600 mg/1. Note (2) Run 56 had lime dose at 2000 mg/1 with the other applied variable constant with runs 53-55. Note (3) Lime and ozone doses increased in each respective run. 54
TABLE 11
COMPILATION OF REAGENT DOSING LEVELS FOR GROUPS 7, 8 AND 9 WITH SIGNIFICANT POLLUTING CHARACTERISTIC CHANGES SHOWN WHERE APPLICABLE
EXPERIMENT DEFINITION LEACHATE CHARACTERISTIC EFFECTED
Statistical Group 7
Runs #57, 62, 63, 64 (Ozone First)
Treatment Variables
Lime 2460 mg/1 (constant)
Alum 0 mg/1 - 75 mg/1
Fe2(S04)3 0 mg/1 - 150 mg/1
Ozone 104 mg/1 (constant)
Statistical Group 8
Runs #65-72 (Ozonation First)
Lime 2100 mg/1 - 2900 mg/1 SS, COD
Alum 50 mg/1 - 100 mg/1
Ozone 108 mg/1 - 130 mg/1 Colour, K*, COD*
Statistical Group 9
Runs #73-80
(1600 mg/1 lime added before ozonation)
Lime 250 mg/1 - 750 mg/1 Ca*
Alum 25 mg/1 - 75 mg/1
Ozone 11 mg/1 - 127 mg/1 TIC*
* Indicates effect was an increase. 55
TABLE 12
COMPILATION OF REAGENT DOSING LEVELS FOR GROUPS 10 AND 11 WITH SIGNIFICANT POLLUTING CHARACTERISTIC CHANGES SHOWN WHERE APPLICABLE
EXPERIMENTAL DEFINITION LEACHATE CHARACTERISTIC EFFECTED
Statistical Group 10
Runs #81-96
(1600 mg/1 lime added before ozonation)
Lime 750 mg/1 (constant)
Alum 75 mg/1 (constant)
Ozone 97 mg/1 - 248 mg/1 Colour, TS, Mn**
Anionic Polymer 0 mg/1 - 2 mg/1 Fe**
Cationic Polymer 0 mg/1 - 2 mg/1
Nonionic Polymer 0 mg/1 - 2 mg/1
Statistical Group 11
Runs #97-100^
(1600 mg/1 lime added before ozonation)
Lime 750 mg/1 (constant)
Alum 75 mg/1 (constant)
Ozone 159 mg/1 (constant)
Anionic Polymer 1 mg/1 (constant)
Cationic Polymer 1 mg/1 (constant)
Nonionic Polymer 1 mg/1 (constant)
Note (1) Runs 97-100 were replicate runs made to establish the standard deviation. ** Low significance. 56
TABLE 13
COMPILATION OF REAGENT DOSING LEVELS FOR GROUP 12, RUNS 101-104
EXPERIMENT DEFINITION LEACHATE CHARACTERISTIC CHANGED
Statistical Group 12
Runs #101-104
(1600 mg/1 added before ozonation)
Lime 750 mg/1 (constant)
Alum 75 mg/1 (constant)
Ozone 0, 124, 181, 181 mg/1 respectively for runs 101 -104
Anionic Polymer 0 mg/1 - 0.5 mg/1
Cationic Polymer 0 mg/1 - 0.5 mg/1
Nonionic Polymer 0 mg/1 - 0.5 mg/1 TABLE 14
NAME CODES FOR THE INDEPENDENT VARIABLES THE POST-SCREENING EXPERIMENTS (GROUPS 2 to 12)
NAME CODE INDEPENDENT VARIABLE
A Lime
B Alum
C Ferric Sulfate
D Ozone
E Anionic Polymer
F Cationic Polymer
G Nonionic Polymer 58
TABLE 15
REMOVAL OF SELECTED POLLUTANTS FROM LANDFILL LEACHATE IN EXPERIMENTAL GROUP 2, RUNS 17, 18, 20 , 23, 27, 29, 30, 31, 32
Original Value Range and Mean of Standard Percent Pollutant or Concentration Residual Concentrations Deviation Removed in mg/1 in mg/1 "s" (best) High Low Mean
pH 5.28 5.99 6.95 6.67 0.015
Turbidity 53 230 4 98 75 92
Colour 2500 2500 500 1200 289 80
Total Carbon 5230 4400 3220 3998 31 38
Total Inorganic Carbon 36.6 40.0 4.0 15.8 0.32 89
Total Organic Carbon 5193 4285 3215 3983 31 38
COD 14105 12718 9734 11507 706 31
Ca 482 2140 780 1163 785 -61
Cu 0.039 0.106 0.030 0.064 0.006 23
Fe 665 325 1.0 86 7.6 99.8
K 156 160 134 150 3.46 14
Mn 10.1 8.2 4.6 6.82 0.095 54
Na 186 185 152 157 10.7 18
P 11.5 0.190 0.110 0.149 0.026 99
Pb 0.035 0.213 0.164 0.181 0.063 -368
Zn 12.45 6.35 0.27 2.71 0.20 98
TS 6775 9135 7535 8366 62 -11
SS 924 183 14 118 0.4 98.5
DS 5851 9107 7266 8248 63 -24 59
TABLE 16
REMOVAL OF SELECTED POLLUTANTS FROM LANDFILL LEACHATE IN EXPERIMENTAL GROUP 4, RUNS 37-52
Original Value Range and Mean of Standard Percent Pollutant or Concentration Residual Concentrat ions Deviation Removed in mg/1 in mg/1 "s" (best) High Low Mean pH 5.28 8.60 6.05 6.85 0.015
Turbidity 100 255 25 145 12 75
Colour 2500 5000 250 1920 289 90
Total Carbon 4095* 4510 3700 4143 31 9.6
Total Inorganic Carbon 29. 5* 29.2 3.0 13 0.32 90
Total Organic Carbon 4065* 4496 3694 4131 31 9.1
COD 13480* 14403 9706 12518 706 28
Ca 475* 1870 570 1077 785 -20
Cu 0.06 0.11 0.041 0.065 0.006 32
Fe 628* 250 0.66 79.3 7.6 99.9
K 152* 148 114 139 3.46 25
Mn 9.79* 8.2 1.5 6.12 0.095 85
Na 160* 255 128 159 10.7 20
P 10.1* 0.41 0.07 0.13 0.026 99.3
Pb 0.033* 0.203 0.057 0.13 0.063 -73
Zn 11.8 4.83 0.04 1.88 0.20 99.7
TS 6602* 8945 7006 8355 62 -3.7
SS 823* 1061 14 286 0.4 98.3
DS 5799* 9111 6949 8074 63 -20
* Average of two eight-litre lots. 60
TABLE 17
REMOVAL OF SELECTED POLLUTANTS FROM LANDFILL LEACHATE IN EXPERIMENTAL GROUP 5, RUNS 53-56
Pollutant Original Value Range and Mean of Standard Percent or Concentration Residual Concentrations Deviation Removed in mg/1 "s" (best) High Low Mean pH 5.28 8.20 6.80 7.16 0.015
Turbidity- 100 200 50 153 75 50
Colour 2500 1500 500 1000 289 80
Total Carbon 4000 3980 3750 3832.5 31 6.25
TIC 2 2..4 17.2 5 8.32 0.32 78
TOC 3978 3963 3744 3819 31 5.0
COD 12854 12823 11511 11977 706 10
Ca 468 1870 1065 1076 785 -127
Cu 0.08 0.063 0.051 0.058 0.006 36
Fe 590 90 6 63 7.6 98.9
K 147 138 126 13 5 3.46 14.3
Mn 9.48 6.90 2.50 5.72 0.095 73.6
Na 135 160 140 146.5 10.7 -3.7
P 8.70 0.180 0.108 0.147 0.026 98.9
Pb 0.030 0.154 0.080 0.115 0.063 -166
Zn 10.35 0.70 0.015 0.355 0.20 99.8
TS 6449 8714 8416 8526 62 -30
SS 723 51 24 41 0.4 96.7
DS 5726 8690 8365 8485 63 -46 61
TABLE 18
REMOVAL OF SELECTED POLLUTANTS FROM LANDFILL LEACHATE IN EXPERIMENTAL GROUP 6, RUNS 57-61
Original Value Range and Mean of Standard Percent Pollutant or Concentration Residual Concentrations Deviation Removed in mg/1 "s" (best) High Low Mean pH 5.27 11.44 10.25 10.94 0.015
Turbidity 62 52 2.2 25.44 75 96.4
Colour 1500 165 85 133 289 94.3
TC 4000 2820 2640 2708 31 34
TIC 22.4 4.2 0.8 1.92 0.32 96.4
TOC 3978 2816 2639 2706 31 34
COD 14300 11259 10687 11045 706 25
Ca 450 1770 1500 1625 785 -233
Cu 0.06 0.075 0.030 0.052 0.006 -
Fe 660 - - - 7.6 50
K 109 138 134 136 3.46 -23
Mn 8.7 0.15 0.05 0.086 0.095 99.4
Na 126 111 110 111 10.7 12.7
P 9.3 0.125 0.065 0.084 0.026 99.3
Pb 0.023 - - - 0.063 -
Zn 9.4 0.035 0.020 0.026 0.20 99.8
TS 6022 12284 9169 9948 62 -52
SS 817 85 26 64 0.4 97
DS 5205 12199 9113 9882 63 -75 62
TABLE 19
REMOVAL OF SELECTED POLLUTANTS FROM LANDFILL LEACHATE IN EXPERIMENTAL GROUP 7, RUNS 57, 62-64
Original Value Range and Mean of Standard Percent Pollutant or Concentration Residual Concentrations Deviation Removed in mg/1 "s" (best) High Low Mean
PH 5.26 10.50 10.21 10.345 0.015 -
Turbidity 62 19 2.2 14.55 75 96.4 '
Colour 1500 165 165 165 289 89
TC 4000 2830 2660 2730 31 34
TIC 22.4 4.2 0.7 1.75 0.32 97
TOC 3978 2829 2655 2728 31 33
COD 14300 11180 8385 10247 706 41
Ca 450 1590 1500 1535 785 -233
Cu 0.06 0.056 0.045 0.052 0.006 25
Fe 660 - - - 76 -
K 109 138 134 137 3.46 -22
Mn 8.7 0.09 0.05 .07 0.095 99.4
Na 126 111 109 110 10.7 13
P 9.3 1.9 0.069 0.54 0.026 99.2
Pb - - - - 0.063 -
Zn 9.4 0.03 5 0.020 0.029 0.20 99.8
TS 6022 9169 9049 9112 62 -50
SS 817 47 26 37 0.4 97
DS 5205 9143 9002 9075 63 -73 63
TABLE 20
REMOVAL OF SELECTED POLLUTANTS FROM LANDFILL LEACHATE IN EXPERIMENTAL GROUP 8, RUNS 65-72
Original Value Range and Mean of Standard Percent Pollutant or Concentration Residual Concentrations Deviation Removed in mg/1 "s" (best) High Low Mean pH 5.27 10.61 9.2 9.88 0.015 -
Turbidity 62 17 14 15.5 75 77
Colour 1500 250 200 212.5 289 87
TC 4000 2870 2740 2806 31 32
TIC 22.4 5.8 1.24 2.8 0.32 94
TOC 3978 2869 2737 2803 31 31
COD 14300 12132 10737 11313 706 25
Ca 450 1640 1410 1516 785 -213
Cu 0.06 0.09 0.065 0.077 0.006 -8
Fe 660 0.971 0.301 0.46 7.6 99.9
K 109 174 131 154 3.46 -20
Na 126 111 108 110.6 10.7 12.7
P 9.3 0.087 0.045 0.067 0.026 99.5
Mn 8.7 0.053 0.036 0.043 0.095 99.6
Pb 0.023 0.060 0.011 0.034 0.063 52
Zn 9.4 0.207 0.024 0.050 0.20 99.7
TS 6002 9577 8747 9135 62 -45
SS 817 25 11 18 0.4 98.6
DS 5205 9562 8722 9117 63 -68 64
TABLE 21
REMOVAL OF SELECTED POLLUTANTS FROM LANDFILL LEACHATE IN EXPERIMENTAL GROUP 9, RUNS 73-80
Original Value Range and Mean of Standard Percent Pollutants or Concentration Residual Concentrations Deviation Removed in mg/1 "s" (best) High Low Mean pH 5.29 10.19 8.21 8.97 0.39 -
Turbidity 62 27 13 18.6 14.93 79
Colour 800 500 125 253 25 84
TC 3210 2600 2495 2563 53 22
TIC 26.7 17.8 1.4 7.5 4.41 95
TOC 3183 2599 2492 2555 53 22
COD 9920 10058 9006 9453 182 9
Ca 333 1270 1050 1186 72 -215
Cu 0.019 0.074 0.056 0.066 0.003 -194
Fe 500 3.428 0.285 1.380 0.496 99.9
K 78 102 93 98 5.12 -19
Na 85 85 80 82.4 0.368 5.8
P 11.4 0.115 0.01 0.081 0.377 99.9
Mn 7.34 0.721 0.107 0.283 0.005 98.5
Pb 0.018 0.024 0.011 0.014 0.014 39
Zn 6.60 0.021 0.015 0.0175 0.036 99.8
TS 4846 7516 6465 7111 126 -33
SS 801 24 3 12.4 39 99.6
DS 4326 7492 6453 7099 93 -49 65
TABLE 22
REMOVAL OF SELECTED POLLUTANTS FROM LANDFILL LEACHATE IN EXPERIMENTAL GROUP 10, RUNS 81-96
Original Value Range and Mean of Standard Percent Pollutant or Concentration Residual Concentrations Deviation Removed in mg/1 "s" (best) High Low Mean
PH 5.29 10.59 10.0 10.26 0.39 -
Turbidity 96 32 2 6.38 14.93 97.9
Colour 1000 600 100 294 25 90
TC 3190 3075 2800 2982 53 12.2
TIC 56.6 3.6 0.8 2.00 4.41 98.6
TOC 3133 3073 2799 2979 53 11
COD 10071 9045 8128 8553 182 19.3
Ca 349 1788 1512 1702 72 -354
Cu 0.023 0.056 0.017 0.034 0.003 26
Fe 510 2.0 0.18 0.68 0.496 99.9
K 72 103 87 94 5.12 -21
Na 76 76.70 75.10 75.76 0.368 1.2
P 14.6 0.39 0.13 0.17 0.377 99.1
Mn 6.44 0.22 0.10 0.15 0.005 98.4
Pb 0.025 0.014 0.003 0.0085 0.014 88
Zn 5.73 0.0143 0.0027 0.0064 0.036 99.9
TS 4623 7292 6912 7110 126 -49.5
SS 520 46 3 17.6 39 99.4
DS 4103 7281 6907 7086 93 -68 66
TABLE 23
REMOVAL OF SELECTED POLLUTANTS FROM LANDFILL LEACHATE IN EXPERIMENTAL GROUP 11, RUNS 97-100
Original Value Range and Mean of Standard Percent Pollutant or Concentration Residual Concentrations Deviation Removed in mg/1 "s" (best) High Low Mean
PH 5.29 11.60 11.52 11.57 0.39 -117
Turbidity 96 41 7 25.25 14.93 92.7
Colour 1000 100 81.5 87.5 25 91
TC 3190 2985 2875 2907 53 9.9
TIC 56.6 9.75 4.4 7.55 4.41 92
TOC 3133 2981 2866 2910 53 8.5
COD 10071 8380 8030 8221 182 20
Ca 349 1956 1788 1872 72 -412
Cu 0.023 .038 .030 .033 0.003 -30
Fe 510 1.30 0.11 0.70 0.496 99.9
K 72 98 86 91 5.12 -19.4
Na 76 77.2 76.3 76.7 0.368 -0.4
P 14.6 0.28 0.21 0.23 0.377 98.5
Mn 6.44 0.04 0.03 0.325 0.005 99.5
Pb 0.025 0.036 0.016 0.017 0.014 36
Zn 5.73 0.0836 0.0026 0.0307 0.036 99.9
TS 4623 7613 7332 7429 126 -58
SS 520 100 10 54.5 39 98
DS 4103 7513 7322 7374 93 -78 67
TABLE 24
REMOVAL OF SELECTED POLLUTANTS FROM LANDFILL LEACHATE IN EXPERIMENTAL GROUP 12, RUNS 101-104
Original Value Range and Mean of Standard Percent Pollutant or Concentration Residual Concentrations Deviation Removed in mg/1 "s" (best) High Low Mean pH 5.29 11.63 11.5 11.56 0.39 -
Turbidity 96 28 5 14 14.93 94.8
Colour 1000 250 100 137.5 25 90
TC 3190 3050 2950 2996 53 7.5
TIC 56.6 10.2 2.2 6.96 4.41 96
TOC 3133 3649 2941 3292 53 6.1
COD 10071 8936 8323 8582 182 17.3
Ca 349 2037 1575 1842 72 -362
Cu 0.023 0.054 0.023 0.036 0.003 0
Fe 510 0.96 0.10 0.63 0.496 99.98
K 72 97 89 94 5.12 -24
Na 76 77.8 76.75 77.4 0.368 -1
P 14.6 0.34 0.09 0.18 0.377 99.3
Mn 6.44 0.05 0.01 0.03 0.005 99.8
Pb 0.025 0.043 0.003 0.02 0.014 88
Zn 5.73 0.017 0.006 0.010 0.036 99.9
TS 4623 7663 6636 7368 126 -44
SS 520 73 7 26 39 98.6
DS 4103 7590 6623 7341 93 -61 68
to find the average response or effect of each of the 4 reagents tested,
as well as the effect of the 11 possible reagent interactions in the
overall response. The "Found Values" shown in Table 25 are the actual residual values for "Colour" in the Group 4 experiments.
The average effect caused by increasing the dose of each of the
applied reagents and interactions is calculated, the ranking noted in
order of absolute value and then transferred to the numerical list
accompanying Figure 14. This data list demonstrates the calculation of
the Standard Deviation used to find the significant effects on the Figure
14 graph. It may be noted that Figure 14 demonstrates the appearance of
a half-normal plot, when a number of the effects of equal size are plotted.
These equal effects could be plotted as one average effect located at the
average order position.
Figure 14 shows that in going from a dose of 51 mg/1 to 98 mg/1
of ozone, ozone has the largest average effect of the reagents tested,
that is, reducing the colour by approximately 2500 units. Lime also has
significant colour-reducing effect of 2000 colour units, in the application
range between 1200 mg/1 and 2000 mg/1. The interaction between lime and
ozone in these application ranges has the effect of increasing the colour
by approximately 1125 colour units. The three foregoing effects of Ozone
and Lime deviate in a statistically significant manner from a half-normal
distribution of nonsignificant effects, and may be estimated to occur with
a confidence of more than 95 percent.
The standard deviation, estimated in the numerical data
accompanying Figure 14, is different from the standard deviation estimated
in Table 16; the latter is arrived at by the results from 3 replicate runs 69
TABLE 25
EXAMPLE OF A FACTORIAL DESIGN MATRIX USED IN THE POST-SCREENING EXPERIMENTS WITH THE MAIN EFFECTS AND THE INTERACTION EFFECTS CALCULATED FOR EACH OF THE FOUR TREATMENT VARIABLES USED IN GROUP 4 (EFFECT ON DEPENDENT VARIABLE—COLOUR)
DEPENDENT VARIABLE Colour ORIGINAL VALUE 2500 Helige Units
INDEPENDENT INTERACTIONS FOUND RUN VARIABLE VALUE NO. mg/1 A B C D AB AC AD BC BD CD ABC ABD ACD BCD ABCD
37 - - - - + + + + + + - - - - + 5000
38 + + + + + + + - - 1500
39 - + - - - + + - - + + + - + - 5000
42 + + - - + - - - - + - - + + + 1500
40 - - + - + - + - + - + - + + - 5000
43 + - + - - + - - + - - + - + + 1500
45 - + + - - - + + - - - + + - + 4000
48 + + + - + + - + - - + - - - - 2000
41 - - - + + + - + - - - + + + - 1000
44 + - - + - - + + - - + - - + + 250
46 - + - + - + - - + - + - t - + 1500
49 + + - + + - + - + - - + - - - 250
47 - - + + + - - - - + + + - - + 1000
50 + - + + - + + - - + - - + - - 250
51 - + + + - - - + + + - - - + - 1000
52 + + + + + + + + + + + + + + + 250 1 o LO o LO o o CN LO CN LO H CN H CN -12 5 112 5 -12 5 -25 0 -12 5 -12 5 -200 0 -250 0 Effect s
Rank 14 3 9 15 8 12 13 7 6 2 11 10 5 1 4 70
in Group 4- and is used as the estimate of the standard deviation for the
"Found Values" of the 16 experiments of Group 4-. The standard deviation of the responses ("Found Values") and average effects are related by the equation:
where s^. Standard Deviation of effect
s Standard Deviation of response r
nH Number of runs at high level reagent dose
nL Number of runs at Low Level reagent dose
While some disparity may be noted in some of these estimates of the standard deviation of effects by the two methods, in no case would the final interpretation of the results be different in these experiments.
Group 2 data was analyzed in the manner described in the foregoing but, because of the missing data points from the missing runs noted in Table 9, the results of the analysis was only used to confirm the data from the complete group.
Where three applied independent variables were used, as in
Groups 8 and 9 (requiring only 8 runs to include all possible combinations of those three variables at two levels), one half of the matrix in Table
25 was used. Plotting of the calculated effects on a half-normal plot, for determination of the significant effects was performed in the same manner as for the 4- independent variable groups. 71
0 2 4 6 8 10 II 12 13 14 15
ORDER NUMBERS
ORDER EFFECT ABSOLUTE z (VALUE HZ) (Z)2 NUMBER NAME VALUE
1 BCD 0 0.079 0 0.006241 2 CD 0 0.158 0 0.024964 3 B 0 0.239 0 0.057121 4 ABCD 125 0.322 40.25 0.103684 5 ACD 125 0.408 51.00 0.166464 6 BD 125 0.496 62.00 0.246016 7 BC 125 0.589 73.625 0.346921 8 AB 125 0.688 86.00 0.473344 9 C 125 0.794 99.25 0.630436 10 ABD 250 0.910 227.50 0.828100 11 ABC 250 1.040 260.00 1.081600 12 AC 250 1899.625 13. 964891 13 AD 1125 14 A 2000 E(VALUE)(Z) 15 D 2500 s = E(Z2)
899.625 3.964891
= 226.89778
Figure 14. Example of the half-normal plot of the absolute values of the calculated dependent variable effects on colour with related standard deviation calculation (name code in accordance to Table 14) 72
7.4 Discussion of Post-Screening Experimental Data
While Tables 9 to 24 summarily describe the experiments and results of the post-screening experimental programme, added discussion of the effects of the treatment on the individual pollutants monitored is given in the following (and summarized in Table 26):
pH. The "best value" chosen for pH is the value closest to neutral (pH 7). This best value occurred in Group 4, Run 38 and for this group the most significant cause of pH adjustment was lime. In Group 4 ozone also contributed significantly to pH adjustment, raising the pH, as would be expected, where both the original and treated leachate pH is at or below neutral (see also p. 46, Section 7.2, Ozone). The adjustment of pH is a critical step in the removal of many pollutants by chemical precipitation and for this type of adjustment lime is the most effective reagent of those used in this investigation.
Turbidity. The best value for turbidity was produced in Group
10, Run 85, with a lime dose of 2350 mg/1. There was no significant added turbidity removal by increasing the ozone dose up to 248 mg/1 in the
Group 10 experiment. Ozone had been shown to effect significant turbidity removal in Group 4 when the ozone dose was increased from 51 to 98 mg/1; therefore, it is considered that, for this particular leachate, the
effective ozone dose is in this range for turbidity removal.
Colour. The statistical analyses of the residual colour measurements obtained indicate that lime effects a significant reduction
in colour in the dose range 0 to 2000 mg/1, but that the most effective
colour reduction was by ozone. Unlike turbidity, for which the most
effective ozone range was between 51 mg/1 and 98 mg/1, the colour reducing 73
effectiveness of ozone continued well above doses of 98 mg/1; this was demonstrated in experimental Groups 8 and 10 with high-level ozone doses
of 130 mg/1 and 24-8 mg/1, respectively. Reproducibility of colour measurements was not good, with, standard deviations larger than "best low" measurements. The treated leachate samples with the low colour measurements were visually acceptable.
Total Carbon. The Total Carbon content of the leachate was not
greatly reduced by the treatments used. The best Total Carbon removal
was 38 percent, while the "best value" in the treated leachate was 2495 mg/1, corresponding to a 22 percent removal rate for that sample. Lime,
in all cases, acted as an inhibitor of Total Carbon removal. The only
effective removal agent was ozone and the amount removed by ozone was
directly affected by the amount of lime added. Overall Total Carbon removed
was not sufficient to produce an acceptable treated leachate effluent.
Total Inorganic Carbon. Low Total Inorganic Carbon residuals
were obtained throughout the experimental programme. It was not possible,
from the statistical analysis, to name any one applied reagent as effective
in causing the removal of inorganic carbon. Total Inorganic Carbon was a
relatively small part of the Total Carbon contained in the untreated
leachate, generally less than 2 percent. The "best value" was obtained
in Group 10, Run 96, with a residual of 0.8 mg/1 and a 98.6 percent removal
rate. The low residuals indicate that the carbonate in the added lime
reagent was not residual in the treated leachate.
Total Organic Carbon. Total Organic Carbon represented more
than 98 percent of the Total Carbon in the leachate; therefore, the results
for Total Organic Carbon are nearly identical to the results for Total
Carbon. 74
Chemical Oxygen Demand. The "best low value" for Chemical Oxygen
Demand was obtained in Group 11, Run .97, with a residual of 8030 mg/1 and a 20 percent removal rate; the best efficiency of removal was in Group 7,
Run 63, at 41 percent. It should be noted that the untreated leachate contained Suspended Solids that were settleable without treatment or by flocculation alone. These Suspended Solids probably contain a considerable part of the COD present (possibly also TC) in the untreated leachate. The
COD removal effect of these self-settling Suspended Solids is not apportioned to any chemical reagent, and may be the real cause of the
"best low value." The indication that settling may be the cause of the best value is that the most efficient removal rate, of 41 percent in Run
63, was shown to have been effected by lime when the lime dose was increased from 2100 mg/1 to 2900 mg/1. The lime dose for Run 97 was 2350 mg/1 with no removal effectiveness shown for lime. From the foregoing, it is very probable that the lime dose range for removal of COD is near
2900 mg/1.
Calcium. There was no effective removal of calcium. The "best low value" for calcium was the result of a zero lime dose. Lime was shown to effectively increase the calcium content of the treated leachate.
Copper. Copper was only removed by lime. The most effective lime dose range was between 1200 to 2000 mg/1. The interaction between lime and ozone was shown to inhibit copper removal. This inhibition of copper removal by the lime-ozone interaction may confirm that the findings of other investigators (27) whereby the pH adjustment of ozone is always towards neutral. Precipitation and consequent removal of copper by lime is a function of pH; if ozone lowers the pH then this would account for 75
the inhibiting interaction.
Iron. The "best low value" for iron was in Group 12, Run 104-, with a low of 0.01 mg/1 of residual Fe and a removal rate of 99.9 percent.
The lime dose was 2350 mg/1 and the ozone dose 181 mg/1 for this run.
The found effective dose ranges, on an individual reagent basis, were for lime, between 1200 and 2000 mg/1, and for ozone between 0 and 98 mg/1, in Group 4- and Groups 1 and 4 respectively.
Potassium. The best "apparent" removal rate for Potassium was
25 percent where 152 mg/1 of K appeared to be removed. The effective removal was caused by ozone in the dose range of 51 to 98 mg/1. In Group
8, with the ozone dose raised from 108 to 130 mg/1, the removal rate was lowered; that is, removal was less at 130 mg/1 ozone than at 108 mg/1.
Since, in most of the found results, K residuals in the treated leachate were higher than in the original untreated leachate, the found values for
K are suspect but the effective removal ranges are not affected.
Manganese. The "best low value" for Manganese was 0.01 mg/1
(99.8 percent removed) found in Group 12, Run 104, with a lime dose of
2350 mg/1 and an ozone dose of 181 mg/1. The effective dose ranges for lime and ozone were for lime 1600 to 2000 mg/1 and for ozone 51 to 98 mg/1.
An effect of low significance was found to continue into the ozone dose range of 96 to 248 mg/1, which may indicate that the effective range of ozone for manganese removal may be something more than 98 mg/1.
Sodium. Behaviour of Sodium, in the leachate under treatment was not definitive; in some cases there was an apparent removal but the effects attributable to any reagent were of low significance and caused by interactions between the applied reagents. The "best low value," found in Group 10, Run 93, was 75.1 mg/1 Na with an apparent removal rate 76
of 1.2 percent. A higher removal rate was found in one of the screening runs, but Na was not found to be significantly removed by any factor applied in the screening group.
Phosphorus. Phosphorus responds readily to pH adjustment by lime, with an effective removal by lime occurring in the 0 to 1220 mg/1 range. Ozone showed no effect on P removal, while ferric sulfate had a low significance effect, depressing the removal of P. The "best low value" was found in Group 9, Run 75, with a low of 0.01 mg/1 and a removal rate of 99.9 percent from an untreated leachate with 11.4 mg/1 phosphorus.
Lead. Lead appeared to be removed up to 88 percent from an original value of 0.025 mg/1. This high removal rate from an original, quite low concentration, occurred in Group 10, Runs 84, 86, 87, 88, 90 and 92, and in Group 12, Run 101. For each of these runs the lime dose was 2350 mg/1 and ozone doses were Run 87--97 mg/1, Runs 84, 86, 88 and
90—248 mg/1, Run 101—0 mg/1. This would indicate that lime was the removing agent and, because increasing the lime dose higher than 1200 mg/1 in any of the post-screening experiments did not produce a significant increase in the removal of Pb (effect), it may be assumed that this was the effective dose. It may be noted that, in going from 1600 to 2000 mg/1 of applied lime in the Group 5 experiments, the average removal of Pb decreased.
Zinc. The "best low value" found for zinc occurred in Group 5,
Run 56; removal rates were high, that is, between 98 and 99.9 percent, in all cases. Significantly effective Zn removals were entirely due to treatment with lime, with the significant removals in the 0 to 2000 mg/1 lime dose range. Ozone had no removal effect but a cationic polymer seemed 77
to have an effect of low significance, in the Group 10 experiments.
Total Solids. Total solids were not decreased in any treatment but instead were increased; an exception to this occurred when there was no added lime. The residual total solids increased with larger lime doses.
Suspended Solids. Lime was effective in suspended solids removal over a wide dose range, from 1200 to 2900 mg/1 of lime. The "best
low value" for SS of 3 mg/1 was found in Group 9, Run 77, with a 99.6 percent removal rate. Ozone had a significant removal effect when the dose was increased from 51 to 98 mg/1 and the lime dose was at 1200 and
2000 mg/1.
Dissolved Solids. Dissolved solids were increased in the treated leachate in all experimental runs when the treatment involved lime.
Ozone had a significant removal effect when the applied dose was increased
from 51 to 98 mg/1. The least increase in dissolved solids occurred in
Group 4, Run 51, when the lime dose was 1200 mg/1 and the ozone dose was
98 mg/1.
7.5 Data—Ozone Disinfection
Table 27 displays the data resulting from the bacteriologic
examination of samples of ozonated leachate. The data of Table 27 is
shown in accordance with recording procedure prescribed by Standard
Methods (18).
7.6 Discussion of Disinfection Data
Two obvious anomalies appear in the results of Table 27. 78
TABLE 26
SUMMARY OF BEST LOW RESIDUALS OBTAINED ' WITH REAGENT DOSES AND DOSE RANGES AS INDICATED
CHARACTERISTIC LOW RESIDUAL RUN EFFECTIVE TREATMENT DOSE OR RANGE (BEST VALUE) NO. Lime Ozone pH (1) (2) 6 .9 pH Jnits 38 2000 mg/1 51 mg/1 Turbidity (2) 2 Hach Units 85 2350 mg/1 51-98 mg/1 Colour (4) 50 colour Units 100 1200 -2000 mg/1 51-248 mg/1 TC (2) 2495 mg/1 78 2630 mg/1 51-98 mg/1 TIC (3) 0.8 mg/1 96 2350 mg/1 248 mg/1 TOC (2) 2492 mg/1 78 2630 mg/1 51-98 mg/1 COD (2) 8030 mg/1 97 2350 mg/1 51-98 mg/1 Ca (1) (2) 350 mg/1 14 0 13 mg/1 Cu (4) 0.017 mg/1 90 1200 -2000 mg/1 51-98 mg/1 Fe (4) 0.10 mg/1 104 1200 -2000 mg/1 0-50 mg/1 K (3) 114 mg/1 51 1200 mg/1 98 mg/1 Mn (4) 0.01 mg/1 104 1200 -2000 mg/1 51-98 mg/1 Na (3) 75.1 mg/1 93 2350 mg/1 98 mg/1 P (2) 0.01 mg/1 75 0 -2000 mg/1 11 mg/1 Pb (1) (5) 0.003 mg/1 84 2350 mg/1 248 mg/1 Zn (2) (4) 0.0026 mg/1 97 1200 -2000 mg/1 158 mg/1 TS (2) (4) 7006 mg/1 51 1200 mg/1 51-98 mg/1 SS (4) 3 mg/1 77 1200 -2900 mg/1 51-98 mg/1 DS 6946 mg/1 51 1200 mg/1 51-98 mg/1
Notes: (1) Underlined dose is single effective dose. (2) Dose not underlined is dose at which low residual achieved. (3) Both doses not underlined indicates no dose range determined. (4) Range of dose underlined indicates range at which reagent was found to be effective. Effective dose in low residual run may be in this range or greater. (5) See Qualification in text on p. 71. TABLE 27
'STANDARD PLATE COUNTS AT 35°C FOR LEACHATE TREATED WITH OZONE (COD of 14,300 mg/1)
Plate No. Dilution Mg/1 03 Dose Colonies Counted
1 1:1 0 17
2 1:1 10 More than 300
3 1:1 20 More than 300
4 1:1 30 More than 300
5 1:1 40 More than 300
6 1:1 89 More than 300
7 1:1 102 More than 300
8 1:1 137 270
9 1:1 163 More than 300
10 to 18 1:1 £ 1:10 110 Average 7 80
Firstly, Plate No. 1, with no applied ozone, shows a relatively low microbial colony count. A critical examination of the procedures used determined that it was possible that this low count may have been caused by residual disinfectant (chlorine), collecting in the sample drain-off line leading from the ozone contacting cylinder (left from the washing and disinfection of the apparatus prior to the test). Secondly, because of the prescribed method of recording the plate counts, Nos. 2 to 9 do not show a distinct point at which bacterial kill occurred, i.e., between
PlatesNos. 7 and 8. However, visual examination of these plates indicated that a noteworthy change in bacterial density had occurred, viz., between the 102 and 137 mg/1 ozone doses.
The choice of 110 mg/1 ozone dose-for plates 10 to 18 was made on the basis of the foregoing change in density, as the approximate ozone dose for bacterial kill. The plate counts for Plates Nos. 10 to 18 confirm that the 110 mg/1 ozone dose was sufficient to produce a satisfactorily disinfected leachate. The high colony count for Plate No. 9, at 163 mg/1 ozone dose, was not obviously explainable, but was discounted as an errant high. The leachate samples for Plates Nos. 10 to 18 were drawn off from the leachate recirculation system, thereby preventing the contamination experienced in the previous sampling.
7.7 General Discussion
The data produced from this investigation is not considered to be definitive for all leachates because of the extreme variability possible in the constituent make-up of landfill leachate. The data generally confirms the findings of other investigators (28, 29) in that many metallic 81
pollutants, with a valence of two or more, may be removed by pH-adjusted precipitation. The degree of removal was most probably governed by the chemical equilibrium of the waste water components and the added reagents, and the effect of this equilibrium on the solubility products of the precipitating ion-product substances. There was some concurrent removal by ozone. Investigated in this project were these multivalent metallics:
Cu, Fe, Mn, P, Pb, and Zn. By referring to Table 26, it is possible to determine the range of "levels" of applied lime and ozone in which the metallic removals were significant. There was no significant removal of
K and Na, univalent metallic ions. Ca, a bivalent metallic, was, in some dose ranges, significantly increased in the treated leachate by the use of lime.
Total carbon, consisting of mostly organic carbon, and contained in the leachate as both dissolved and suspended solids, was only partially removed by the treatment methods used in these investigations. Therefore, it was not possible to produce an acceptable effluent for discharge to a natural receiving water, even though Table 26 shows that significant effective removals were accomplished.
Colour and turbidity were removed mainly by ozone, although lime was somewhat effective as well. This colour removal by lime takes place in a narrow range of pH adjustment, made by increasing the lime dosage from 1200 to 2000 mg/1 (pH 6.05-8.5). Lime "colour removal" was probably due, in part, to the change in the form of the Fe present, that is, from the ferrous to the ferric form. This particular colour removal may be attributed to the following.
Because the leachate used in these experiments was ozonated by introducing ozone in an oxygen carrier, before the pH adjustment with 82
lime, the leachate entering the lime treatment stage was highly oxygenated.
Ferrous iron is oxidized to the ferric form in accordance with (16):
++ 2Fe + j 02 + 5H20 -»• 2Fe(0H)3 (s) + 4H
An examination of a solubility chart for Fe(OH)3 and the various other trivalent-iron components (for example, see page 29-17 Ref. (16))
indicates that the solubility of Fe(OH)3 (s) is at a minimum in the approximate pH range under discussion, with a consequent increase in the combined trivalent iron, ionic species Fe(OH)^ , Fe(OH)* and Fe(OH)++.
Organic colour, such as that in leachate, probably is related to humic substances. Chemically, these humic substances are polymeric compounds with carboxylic functional groups. Chemical interactions account for colour removals by trivalent iron. Together with OH ions, the functional groups of colour anions occupy coordinative sites of the trivalent-metal ionic species (16).
Anionic, nonionic, and cationic polyelectrolytes were tested in doses of 0.5, 1.0, and 2.0 mg/1, but none were found to significantly increase any pollutant removals. However, since polymers serve as settling or flocculation aids by increasing the floe size and improving the settling characteristics of the resulting sludge, this noneffect may be used as an indication that the physical processes used (stirring and settling) were working well.
The ozone disinfection data was discussed in the previous section.
This data confirmed the ability of ozone to disinfect wastewaters noted by others (11, 27). Others have also noted that ozone doses as small as 83
1 to 2 mg/1 can effectively disinfect drinking water. Wastewaters, contaminated with -a high concentration of BOD or COD, require larger doses for disinfection, although this has been reported as "time to kill" (25).
Analysis of the data for the experiments reported on here indicate that there is an ordered sequence of ozone priorities by the contaminating wastewater constituents. During this ozone priority sequence, the reaction of ozone is very rapid, that is, instantly with the transfer of the ozone to the wastewater. This rapid reaction of ozone continues up to and beyond the order position at which microorganisms are destroyed.
7.8 Application of the Results to Predict Ozone Requirements
Much of the investigation carried out in this programme was concerned with finding the dose at which applied reagents were most effective in removing or altering selected characteristics of the leachate wastewater. Knowing these levels can only be useful if they can be correlated to some measurable characteristic of the leachate and to some unique, useful characteristic of the polluting substance. Where lime is the applied reagent, the measurable wastewater character is the product pH, and the useful, unique, known characteristic of the pollutant is its hydroxide-form, solubility product.
At this time, little is known of the ozone requirements necessary to promote removals or desirable changes of pollutants in any wastewater.
For the purpose of formulating a method for predicting the ozone require• ment to treat leachate, to remove any specific metallic pollutant, COD was chosen as the measurable leachate characteristic that will be used as the reference base for the leachate. The ratio obtained by dividing the 84
given metal's valence by its ionic radius in Angstrom units (A), was the unique and useful characteristic chosen for the metallic pollutants.
The rationale for the foregoing ozone-related choices is as follows: COD is an estimate of the ability of the organics in a wastewater to reduce a strong oxidant (dichromate). However, the test does not measure all, or only, the organic compounds, but rather the wastewater's ability to reduce the chemical oxidant. Many inorganic substances coincidentally reduce the oxidant as well. Since ozone is also a strong chemical oxidant, the use of COD, as a measure of the effectiveness of ozone as an oxidant, is cognately useful.
Valence, in chemistry, is a property of an element that determines the number of other atoms with which the atom of the element can combine. The size of an ion is a function of an ion's nuclear positive charge in relation to the total negative charge of the electrons surrounding that nucleus. There will be an attractive force between two adjacent ions, where one has a preponderant positive charge and the other a negative charge. Thus, an ion's size, as measured by its radius, is an important factor in the chemical reactivity of an ion (14). The calculation of the activity, or more specifically the"activity coefficient," for an ion in aqueous solution, may be made approximately from the summary
"DeBye-Huckle" equation (.16):
2 y (4) log f± = 0.5Zi - 1 + \{'- 85
in which: f\ = the ratio of the activity to the molar concentration
= the electronic valence of the ion
y - the ionic strength as defined by the following
equation (31).
2
y = 0.5Ei ciZi (5)
where: -c^ = the molarity of the i^1 ion
Z^ = the valence of the i ion.
The complete equation from the "DeBye-Hu'ckle" theory more effectively
demonstrates the utility of the valence-ionic radius ratio, for describing
the activity of an ion in an aqueous solution:
2 k2 0.511 x zi + y lQgm f 10 1 o V 1 + 0.329 x v x y2
where: f^ , Z^ , y are as above and
f" = the ionic radius in Angstrom units (A).
Calling it the "ionic potential," the ratio of ionic charge
(valence) to ionic radius in Angstrom units (A) was first put forward by
Goldschmitt (.12), to explain the distribution of elements between sediments
and sea water. On the basis of their ionic potential, the elements are
divided into three groups, which become separated from one another during 86
sedimentation in the sea. The cations, with low ionic potential (less than three), generally remain in ionic solution. Intermediate ionic potential ions, in the range of 3 to 12, have hydroxy1 bonds in their hydroxides and are deposited as hydrolysates. The elements with higher ionic potentials, generally greater than 12, form complex anions with oxygen and these usually remain in solution. Nitrogen, carbon, sulphur and phosphorus belong to this group.
It is also known that the metals which have a small atomic or ionic radius are more active in complex ion formation (30). From the periodic table, the metals with atomic numbers 24- through 30, that is,
Cr, Mn, Fe, Co, Ni, Cu and Zn, with ionic radii in the range of 0.64 A to
0.80 A, have a much greater tendency to form complexes than those with
larger ionic radii such as K and Ca, with ionic radii 1.33 A and 0.99 A, respectively. The process of "complex forming" is also enhanced by the electronegativity of the ligand or electron donor and conversely the size of the positive charge on the metal cation.
Ozone is the strongest known oxidant, much used in research and
industry to break or destroy organic ligands. At the same time, ozone is a ready donor of electrons and may be expected to oxidize such hydroxo- complexes, viz.: The hydroxo-complex would form in a neutral to basic
solution as
Al+++ + OH" ^ A1(0H)++
while a simplified ozone reaction on mixing with water,
0o + Ho0 - 20H~ + 0o+ 87
followed by the combination reaction,
++ A1(0H) + 20H~ Al(0H)3(s).
The reaction by ozone with hydroxo- and organo-metal complexes may account for some of ozone's ready reactivity when mixed with the leachate.
In these experiments, the ozone dose was kept within the level that would transfer and be reacted in the residence time of the oxygen- carrier gas, in the contact cylinder (see Figure 13). When ozone was applied at up to 248 mg/1 to the leachate, with a COD concentration of approximately 10,000 mg/1, all of the ozone was transferred to the leachate. At more than 24-8 mg/1, some of the ozone exited the contact cylinder with the carrier-oxygen stream, indicating a slower reaction rate between the*ozone and the remaining ozone-reacting substances. The utility of staying within the above-mentioned ozone dose will be discussed in
Section 7.9.
The nomographic chart shown in Figure 15 was constructed to possibly provide a quick and simple method of predicting the ozone dose required to both increase the metal removal in a lime-induced, pH-adjusted precipitation, and to disinfect the treated wastewater. The construction of this chart may be criticized in that only two points, from the generated data, were used to position the diagonal line indicating the ozone-to-COD ratio, and thereby, the ozone dose necessary to oxidize some metallic pollutants, and to disinfect the leachate. In Figure 15, ozone is given in mg/1 while COD is in grams/1.
In accordance with Goldschmitt's (12) presentation, the elements with a small (less than: 3) ionic potential are not readily oxidized. In 88
CODg/l FIG 15 » CHART FOR ESTIMATING OZONE DOSE REQUIRED TO OXIDIZE CERTAIN METALLIC IONS AND LIVING ORGANISMS. 89
this work, this was confirmed for those elements monitored—Na, K and Ca.
For the elements with an ionic potential greater than 12, such as carbon
(C), some removals were noted but it may be that this was due, in part, to mechanical removal in settling. The intermediate ionic potential metallics (ionic potential 3 to 12), were only significantly effected in one case, that is, in the case of Mn. This may partly be due to the fact that the ozone was applied to the leachate before pH adjustment, when, at acidic pH ranges, those elements that have more than one valence state may be expected to be in the lower state. For example, iron at valence 2, has an ionic potential of 2.7 as compared to valence state 3, when the ionic potential is 4.68.
The bounds shown for the "Estimated ozone/COD for disinfection,"
in Figure 15, is an empiric impositioning of the value found in these
experiments, of the ozone dosage required to kill bacteria. This value for bacterial kill, related as it is to the ozone-COD ratio, may
indicate the mechanism of the often reported "threshold value" or "all or nothing" phenomena reported in the literature for ozone disinfection.
Since this concept of ozone-COD ratio would be most useful in determining
the quantities of ozone required for disinfection, the graph, as shown in
Figure 15, is adequate.
Colour and turbidity, as noted in Section 7.3, are both changed
and removed by ozone. It is possible that an empiric position for both
colour and turbidity removal could be entered on the Figure 15 graph, so
that it might also predict the ozone required for this procedure. 90
7.9 Cost Considerations
It is beyond the scope of this examination to provide a detailed cost elaboration for treating leachate by physical-chemical systems. It should be noted, however, that this study indicates the cost for disinfection, by ozone, is very sensitive to the COD of the wastewater being treated, and that the cost of ozone required will increase, directly, with increasing COD in the wastewater being treated.
Traditionally, disinfection of water and wastewater has been quantified by overdosing as measured by a residual of the disinfecting agent in the treated effluent. In the case of wastewaters with relatively high COD strengths, this may lead to considerable overdosing, beyond the point where disinfection has taken place. By using the ozone-COD ratio proposed here, to determine the ozone dose required for disinfection, the overdosing may be prevented. In the case of the leachate under consideration here, with a COD in the order of 10,000 mg/1, the ratio of ozone in mg/1 to COD in grams/1 is approximately 10, but to approach a ratio where a residual is possible, this ratio must be increased by at least 7\ times.
When extensive overdosing is practiced with ozone, it becomes necessary to equip the ozonation plant with a recycle system to return the unused ozone and carrier gas to the generation point. This recycle system must be ozone corrosion proof, hence, costly to install. The carrier gas, having passed through the wastewater, is moisture laden and must be dessicated before reentering the ozonator again. This drying of the gas is, in most cases, more difficult and more expensive than is the drying of free air from the atmosphere. All these considerations lead to higher 91
capital costs for the ozonating plant-.
It has been estimated that it requires 28 watt-hours of electrical energy to produce and dose 1000 mg of ozone (32). This figure includes energy for the ozonator and ancillary energy for injection and air preparation. Using this estimate and using an electrical energy cost of 5 cents per KWH, it would cost, for energy, approximately 10 cents per
1000 gallons for disinfection. Diaper (32) estimates the cost of amortizing a 10 mgd ozone-dosing plant at 2 times the power costs; there• fore, the total cost for disinfection of the leachate used in this project would be in the order of 30 cents per 1000 gallons for that size.
For comparison, a plant designed to treat effluent from a 10 mgd secondary sewage treatment plant, with an effluent COD of 100 to 150 mg/1, would cost approximately 3 cents per 1000 gallons to disinfect the effluent 92
CHAPTER 8
CONCLUSIONS AND RECOMMENDATIONS
8.1 Conclusions
1. The bulk of the metallic pollutant removal was accomplished
in the lime-initiated, pH adjustment phase of the treatment. Metallic
ion pollutants with valences of 2 or more were removed by precipitation
to levels adequate to meet regulatory standards (4), but not to levels
indicated by the solubility products of their hydroxides. This nonconformity to solubility-product constants is probably due to
interference by interionic phenomena in a strong solution.
2. Soluble organics in the leachate were not removed
sufficiently by lime pH adjustment to produce an effluent that would meet
regulatory standards (.4-). "Ozone" organic removals were small and appeared
to be directly proportional to the applied ozone dose.
3. Turbidity was increased by lime addition, but ozone is
effective in reducing turbidity. The effective elimination of turbidity
by ozone appears to take place, in the main part, at comparatively low
ozone-COD ratios (5-10 mg/1 ozone per gram/1 COD) with some tailing of
to higher ratios (10-20 mg/1 ozone per gram/1 COD).
4. Leachate colour was reduced by both lime and ozone. There
are two sources of colour in the leachate treated; one from multivalent
metals, mainly iron, and the other from organic materials. Both lime and
ozone caused reduction in colour caused by metals, while only ozone reduced 93
colour from organics. The organic colour reduction took place at relatively low ozone doses.
5. Ozone is an effective disinfectant but the disinfection
process only took place after the ozone demand of those substances with a
greater reactivity with ozone had been satisfied. When these substances
were measured as COD in the untreated leachate, the ratio of mg/1 of ozone
required to grams per litre of COD in the leachate was 10 to 1.
6. Alum, ferric sulfate and polyelectrolites had no real effect
in assisting the removal of any pollutants when used in combination with
ozone and lime. These reagents were not tested singly, so that no
judgement is made of their singular capabilities.
7. Based on the results of this study, for the reagents tested
and this particular leachate, the "best" overall treatment would be an
application of 110 mg/1 ozone, followed by pH-adjusted precipitation,
using 2350 mg/1 of lime. This would result in: (a) disinfection,
(b) removal of 97.9 percent of the pretreatment turbidity and 90 percent
of the colour, (c) removal of 20 percent of the COD, and (d) metals would
be removed as listed: Cu—26%, Fe—99.98%, K—0%, Mn—99.8%, Na—0%,
P—98.5%, Pb—39%, Zn—99.9%. The resulting pH would be high, over 10 pH
units.
8.2 Recommendations
1. It is recommended that a controlled investigation of ozone
demand be carried out, using, in place of leachate, prepared mixtures of
known concentration of soluble metals, organic materials and microbes.
2. Ozone oxidizing efficiencies were not investigated in this 94
project. Other investigators (28) have noted oxidation efficiencies greater than 100 percent, based on the reduction of COD, utilizing one effective oxygen atom per molecule of ozone. It is possible that this greater than 100 percent efficiency is due to short life, single-oxygen, radicals formed during the splitting of oxygen molecules in the electric- discharge, ozone-generating process. These radicals have a "forbidden" electric configuration that does not invite union with an oxygen molecule to form an ozone molecule. The life of this radical is short, in the order of 100 seconds (33), and the possibility of it becoming a reactant
in a wastewater is present if the ozone-oxygen stream is quickly contacted with the wastewater. An investigation of this possible phenomenon should be carried out by increasing the^time, from generation to reaction through
storage, of the newly generated ozone.
3. Additional and more comprehensive studies are necessary before a practical and economic physical-chemical system can be developed
for treating raw landfill leachate with lime and ozone. These studies
should include:
a. As in (1) above
b. An investigation to treat the effluent biologically
to reduce COD and other parameters to acceptable levels
c. An investigation to pretreat the raw leachate
biologically in a biosystem or otherwise, to reduce
heavy organics and other substances, prior to physical-
chemical treatment.
4. Before any other investigations with ozone are carried out,
the laboratory concerned should have an ozone meter and constant voltage
regulators for the ozone generator. 95
CHAPTER 9
LIST OF REFERENCES
1. Uloth, V. C. and Mavinic, D. S., "Aerobic Biostabilization of a High Strength Landfill Leachate," Faculty of Applied Science Report, University of British Columbia, Page 3, February 1976.
2. - Poorman, B. L., "Treatability of Leachate from a Sanitary Landfill by Anaerobic Digestion," Master of Applied Science Thesis, University of British Columbia, 7 5 pages, April 1974.
3. Lidkea, T. R. , "Treatment of Sanitary Landfill Leachate with Peat." M.A.Sc. Thesis, Department of Civil Engineering, University of British Columbia, 61 pages, September 1974.
4. Pollution Control Board, "Report on Pollution Control Objectives for Municipal Type Waste Discharges in British Columbia," Department of Lands, Forests, and Water Resources, Government of the Province of British Columbia, September 1975.
5. Thornton, R. J. and Blanc, F. C. , "Leachate Treatment by Coagulation and Precipitation," Journal of the Environmental Engineering Division, Proc. Amer. Soc. Civil Engineers, 99, No. EE4, pp. 535-544, 1973.
6. Chian, E. S. K. and DeWalle, F. B., "Characterization and Treatment of Leachate Generated from Landfills," Water-1974: ii, Municipal Waste Treatment, AIChE. Symposium Series, 145, Vol. 71, pp. 319-327, 1974.
7. Boyle, W. C. and Ham, R. K., "Treatability of Leachate from Sanitary Landfills," Proceedings of the 27th Industrial Waste Conference, May 1972, Part 2, Engineering Extension Series, Purdue University, Purdue, Indiana.
8. Cooper, R. C., Potter, J. L. and Leong, C., "Virus Survival in Solid Waste Leachates," Water Research, Pergamon Press, Vol. 9, pp. 733-739, Great Britain, 1975.
9. Corbett, J. R. E., "Treatment of a Low Strength Landfill Leachate with Peat," M.A.Sc. Thesis, Department of Civil Engineering, University of British Columbia, 174 pages, April 1975.
10. "Impact of Water Chlorination," Environmental Science and Technology, Vol, 10, Page 21, January 1976.
11. Yao, K. M., "Is Chlorine the Only Answer?" Water and Waste Engineering, Page 30, January 1972. 96
12. Goldschmitt, V. M., "The Principles of Distribution of Chemical Elements in Minerals and Rocks,"-- Journal of the Chemical Society, pp. 655-673, London, 1937.
13. MacKenzie, G., Tracey, J. and Ellis, M. W., "Geology of the Arkansas Bauxite Region," Professional Paper 299, United States Government Printing Office, Washington, D.C. , 1948.
14. Drummond, A. H., "Atoms-Chrystals-Molecules, Modern Views of Atomic Structure and Chemical Bonding," American Education Publications, The Wesleyan University Press, Columbus, Ohio, 1964.
15. Wastewater Engineering, Metcalf and Eddy, McGraw Book Company, New York, N.Y. , 1972.
16. Fair, G. M. , Geyer, J. J. and Okun, D. A., Water and Wastewater Engineering, Vol. 2, John Wiley and Sons, Inc., New York, N.Y. , 1968.
17. B. I. F., A Unit of General Signal Corp., "Chemicals Used in the Treatment of Water and Wastewater," Water and Sewage Works, Reference Number, 1972.
18. Placket, R. L. and Burman, J. P., "Design of Optimum Multifactorial Experiments," Biometrica, Vol. 33, Page 305, 1946.
19. Stowe, R. A. and Meyer, R. P., "Efficient Screening of Process Variables," Industrial and Engineering Chemistry, Vol. 58, No. 2, February 1966.
20. A.P.H.A., A.W.W.A., W.P.C.F., Standard Methods for the Examination of Water and Wastewater, American Public Health Association, Inc., 13th Edition, 1971.
21. Zahn, D. A., "Modification of and Revised Critical Values for the Half-Normal Plot," Technometrics, 17, 2, May 1975.
22. Zahn, D. A., "An Empirical Study of the Half-Normal Plot," Technometrics, 17, 2, May 1975.
23. Daniel, C, "Use of Half-Normal Plots in Interpreting Factorial Two Level Experiments," Technometrics, 1, 311, November 1959.
24. Cameron, R. D. and MacDonald, E. C., "Procedures for the Analysis of Landfill Leachate," Appended Seminar Proceeding Report, Environment Canada, Solid Waste Management Report, EPS-4-752, October 1975.
25. Bringman, G., "Determination-of the Lethal Activity of Chlorine and Ozone on E. Coli," Zeitsschift fiir Hygiene, 130, Page 130, 1954.
26. Ingols, R. S.. and Fetner, R. H., "Some Studies of Ozone for Use in Water Treatment," Proceedings of the Society for Water Treatment and Examination, 6, 8, 1957. 97
27. Wynn, C. S., Kirk, B. S. and McNabney, R., "Pilot Plant for Tertiary Treatment of Wastewater with Ozone," Water, A.L.Ch.E. Symposium Series, No. 129, Vol. 69, Page 42, October 1974.
28. Nilson, R., "Removal of Metals by Chemical Treatment of Municipal Waste Water," Water Research, Pergamon Press, Vol. 5, pp. 51-60, Great Britain, 1971.
29. Netzer, A., Norman, J. D. and Vigers, G. A., "Removal of Trace Metals from Wastewater by Ozonation," Water Pollution Research in Canada 1972, Vol. 7, February 1972.
30. Masterton, W. M. and Slowinski, E. J., Chemical Principles, 2nd Edition, W. B. Saunders Company, Toronto, 1969.
31. Sawyer, C. N. and McCarty, P. L., Chemistry for Sanitary Engineers, 2nd Edition, McGraw-Hill Book Company, Toronto, 1967.
32. Diaper, E. 'W. J., "Ozone Moves More to the Fore," Water and Wastes Engineering, Page 65, May 1972.'
33. Yates, W. F. and Burleson, J. C, "Chemical Reactions in a Silent Electric Discharge," Chemtech, pp. 31-35, January 1973. 98
CHAPTER 10 - APPENDICES
GENERAL BIBLIOGRAPHY
1. Weber, Walter J., Jr., Physical-Chemical Processes for Water Quality- Control, John Wiley and Sons, New York, 1972.
2. Davies, 0. L., Design and Analysis of Industrial Experiments, Hafner Publishing Co., New York, 1954.
3. Netzer, A., Norman, J. D. and Vigers, G. A., "Removal of Trace Metals from Waste Water by Ozonation," Water Pollution Research in Canada 1972, Editor Murphy, K. L. , McMaster University, Ontario.
4. Gabovch, R. D., Vrochinskii, K. K. and Kurinnyi, I. L., "Decolorization, Deodorization and Decontamination of Drinking Water by Ozonation," Hygiene and Sanitation, Vol. 34, No. 6, pp. 336-340 (English).
5. Posselt, H. S., Reidies, A. H., Weber, W. J., Jr., "Coagulation of Colloidal Hydrous Manganese Dioxide," Journal AWWA, p. 50, January 1968.
6. Rebhun, M. Streit, S., "Physico-Chemical Treatment of Strong Municipal Waste Water," Water Research 8_, p. 195, 1974.
7. Linstedt, K. D., Houchk, C. P., O'Connor, J. T. , "Trace Element Removal in Advanced Waste Water Processes," Journal WPCF, 43, 7, p. 1507, July 1971.
8. 0'Melia,tC. R. , "Coagulation in Water and Waste Water Treatment," Water Quality Improvement by Physical and Chemical Processes, Edited by Earnest F. Glpyna and W. Wesley Eckenfelder, Jr., University of Texas Press, Austin, Texas, 1965.
9. Stumm, W., 0'Melia, C. R., "Stoichiometry of Coagulation," Journal AWWA, p. 515, May 1968.
10. Weber, W. J., Jr., Hopkins, C. B., Bloom, R. B., Jr., "Physiochemical Treatment of Waste Water," Journal WPCF 42, 1, p. 83, January 1970.
11. Mackriel, S., "Mechanism of Coagulation in Water Treatment," Journal Sanitary Engineering Division, Proceedings ASCE, SA3, p. 117, May 1962. 99
PHYSICAL CHEMICAL TREATMENT OF LANDFILL LEACHATE
RAW DATA - Mg/1 EXCEPT pH - TURBIDITY AND COLOUR
>, T) 4-> n U rH -P rH CO rH T3 RUN NO. o O rd o o o o ft H o H CJ H CO CO co CJ O O
1 8.05 95 6420 15680 78.78 0.029 — : 0.043
2 8.50 66 6374 12517 56.56 0.029 — ;0.042
3 8.45 40 6480 12923 58 0.018 — 0.036
4 5.55 120 6480 11864 639 0.042 — 0.054
5 7.40 78 6360 11904 117 0.030 — 0.049
6 5.60 100 5975 10354 574 0.064 — 0.070
7 6.70 104 6620 12238 339 0.035 — 0.051
8 9.11 24 6932 12792 190 0.031 — 0.060
9 5.06 76 6543 10674 638 0.039 — 0.065
10 5.09 60 7201 8841 146 0.041 — 0.051
11 6.93 93 6330 12201 394 0.037 — 0.057
12 5.55 55 6550 10560 549 0.041 — 0.040
13 5.00 45 6785 9140 258.3 0.042 — 0.013
14 5.00 72 7160 10188 • 1880 0.048 — 0.057
15 6.16 106 6790 11841 452 0.039 — 0.041
16 5.03 60 7380 8503 309 0.035 — 0.043
17 6.20 180 1500 3900 7576 183 11462 0.030
18 6.81 49 1500 4300 8942 34 12718 0.064
20 6.20 215 1000 4060 7669 346 9734 0.077
23R 6.95 71 2500 4400 9130 58 12564 0.044
27 5.99 230 1000 3220 7535 269 11455 0.073 100
PHYSICAL CHEMICAL TREATMENT OF LANDFILL LEACHATE
RAW DATA - Mg/1 EXCEPT pH - TURBIDITY AND COLOUR
DEPENDENT VARIABLES o o cu rd rd COM RUN NO. PH c o PH S H E-H
1 1.08 21.9 900 257 360 0.625 1
2 1.17 13.5 625 240 336 2.475
3 1.07 9.4 775 242 330 0.82
4 38.0 137.5 880 249 359 11.44
5 3.13 37.5 700 248 349 16.20
6 33.75 175.0 525 249 358 10.80
7 16.50 105.0 750 256 351 7.28 4-> •H 8 e 0.72 3.5 752 243 326 0.375 c 9 o 34.25 250 575 257 350 11.70 •H -P o 10 CD Q 11 14.50 43.75 990 225 270 3.90 o H 12 30.25 300.0 537 248 353 5.26 m
13 33.75 457 490 267 360 15.00
14 32.5 47 5 350 266 370 16.20
15 25.00 167.5 675 248 351 9.60
16 32.50 441.0 560 270 370 15.10
17 0.164 4.80 150 1025 140 152 0.18 7.99 3880 20.1
18 0.217 0.39 100 1125 156 152 0.116 6.65 4285 15.0
20 0.164 6.35 325 1040 134 152 0.110 8.00 4046 14.0
23R 0.190 0.90 53 780 160 152 0.170 7.24 4396 4.0
27 0.181 4.72 60 1020 153 158 0.176 8.20 3215 5.0 101
DEPENDENT VARIABLES
3 Carbo n Suspende d Colou r Tota l Tota l Solid s Solid s CO D RUN NO. ft Turbidit y o o
29 7.20 4 500 4260 8833 14 11906 — — 0.106
30 7.29 32 1000 4160 9135 28 12192 — — 0.069
31 6.09 100 1500 3800 7624 111 10930 — — 0.067
32 7.28 4 500 3890 8850 17 10604 — — 0.047
37 6.20 125 5000 4280 8707 106 13597 — — 0.081
38 6.90 240 1500 4430 8945 76 12887 — — 0.054
39 6.05 165 r'500 4180 8511 924 14403 — — 0.100
40 5.95 145 5000 4200 8694 852 13423 — — 0.094
41 6.48 210 1000 3780 7518 74 9706 — — 0.051
42 6.72 250 1500 4380 8843 68 13191 — — 0.041
43 6.85 235 1500 4510 9168 57 13536 — — 0.055
44 8.60 25 250 4190 8566 14 12582 — — 0.041
45 5.99 190 4000 4170 8450 822 13123 — — 0.091
46 6.44 145 1500 3700 7396 124 11398 — — 0.046
47 6.45 92 1000 3800 7524 215 11560 — — 0.046
48 6.70 255 2000 4370 8903 82 13056 — — 0.041
49 8.35 39 250 4220 8510 81 12169 — — 0.060
50 8.21 "64 250 4250 8461 20 12656 — — 0.085
51 6.39 78 1000 3700 7006 57 11025 — — 0.112
52 7.32 68 250 4140 8478 4.1 12108 — — 0.046
53 6.83 180 1000 3750 8534 4.7 11511 — — 0.051
54 6.80 200 1000 3810 8440 4.3 12823 — — 0.063
55 6.81 ' 180 1500 3790 8416 5.1 11714 0.060 102
DEPENDENT VARIABLES
o CJ rrj rrj o M RUN NO. c CJ 53 PH E-H E-H
29 0.164 0.43 1.0 1175 158 185 0.130 5.85 4220 40
30 0.164 0.45 8.3 1140 157 160 0.136 4.85 4147 12.8
31 0.170 6.06 75.5 1025 156 152 0.190 8.05 3789 10.9
32 0.213 0.27 1.5 2140 140 152 0.130 4.60 3869 20.8
37 0.124 1.15 250 650 140 140 0.146 8.10 4265 15.0
38 0.109 0.12 28.5 1225 140 175 0.160 5.35 4420 9.6
39 0.128 3.93 50.0 1870 142 145 0.146 8.20 4163 16.5
40 0.117 4.71 36 1020 141 255 0.092 8.05 4189 11.9
41 0.114 3.22 150 985 130 133 0.130 7.80 3764 16.0
42 0.057 0.42 53 1175 140 254 0.180 6.20 4373 6.5
43 0.129 0.13 32 705 148 145 0.154 5.50 4496 14
44 0.203 0.58 0.66 1210 133 132 0.160 1.50 4161 29.2
45 0.116 2.07 210 1055 134 175 0.150 8.05 4156 13.5
46 0.116 4.61 165 1040 137 140 0.170 8.05 3695 5.5
47 0.171 4.83 110 1005 130 137 0.41 7.99 3797 3.0
48 0.131 0.39 50 1160 143 139 0.070 6.25 4363 6.5
49 0.193 0.05 4.5 1200 126 147 0.124 2.15 4193 2.7
50 0.181 0.04 6.5 1180 124 128 0.130 2.50 4228 22.0
114 51 0.121 3.74 105 570 171 0.124 8.05 3694 4.5
52 0.115 0.06 J18 135 135 0.092 1180 4.20 4132 7.5
53 0.080 0.39 90 132 140 0.108 3744 5.6 1095 6.71
54 0.139 0.70 80 126 143 0.160 3805 5.5 1065 6.80
55 0.086 0.315 75 126 160 0.140 3785 5.0 2440 6.90 103
DEPENDENT VARIABLES
3 Carbo n Solid s CO D Colou r Solid s Suspende d Tota l Tota l RUN NO. a< Turbidit y o O
56 8.20 50 500 3980 8714 2.4 11860
57 10.25 2.2 165 2720 9169 26 10687 —
58 10.40 52 :165 2700 12284 85 10985 — 0.055
59 11.2 27 85 2640 9189 76 11135 — — 0.045
60 11.44 17 165 2660 9569 49 11159 — — 0.030
61 11.39 29 85 282Q 9527 83 11259 — — 0.075
62 10.42 18 165 2830 9049 4.7 10737 — — 0.050
63 10.21 19 165 2660 9076 32 8385 — — 0.055
64 10.50 19 165 2710 9155 42 11180 — — 0.045
65 10.51 17 250 2820 9221 22 11134 — — 0.082
66 10.61 16 200 2770 9230 17 10737 — — 0.065
67 9.71 16 200 2820 8747 25 11135 — — 0.069
68 9.60 15 250. 2740 8806 13 10928 — — 0.081
69 9.41 .'15 200 2815 8903 21 11913 — — 0.068
70 10.00 16 200 2870 9471 11 11391 — — 0.094
71 9.2 15 200 2820 9024 20 12132 — — 0.079
72 10.00 14 200 2790 9577 15 11135 — — 0.090
73 8.30 27 175 2560 6465 12 9553 — — 0.067
74 9.83 13 125 2600 7448 18 9694 — — 0.079
75 9.90 14 250 2590 7378 11 9089 — — 0.071
76 9.50 16 225 2550 7408 8 9652 — — 0.056
77 8.40 24 500 2560 6695 3 9395 — — 0.067
78 10.19 16 250 2495 7516 24 10058 0.060 104
DEPENDENT VARIABLES o O XA CD rrj rrj o 1—f RUN NO. c O IS3 56 0.154 0.015 6 1195 138 143 0.180 2.50 3963 17.2
57 0.020 1550 138 111 0.125 0.09 2719 0.7
58 0.020 1590 138 111 0.075 0.09 2697 2.7
59 0.030 1670 138 110 0.086 0.05 2639 0.8
60 0.025 1770 134 111 0.070 0.05 2659 1.2
61 0.035 1670 134 111 0.065 0.15 2816 4.2
62 0.035 1560 134 109 0.081 0.07 2829 0.7
63 0.025 1590 138 109 0.069 0.07 2655 4.5
64 0.032 1440 138 111 1:90 0.05 2709 1.4
65 0.014 0.038 0.427 1615 138 111 0.055 0.042 2826 4.2
66 0.019 0.023 0.314 1640 134 111 0.056 0:036 2768 1.7
67 0.011 0.026 0.771 1430 142 111 0.079 0.042 2819 1.4
68 0.052 0.026 0.328 1490 131 108 0.067 0.037 2737 2.8
69 0.052 0.025 0.301 1515 168 111 0.068 0.036 2809 5.8
70 0.060 0.207 0.421 1515 172 111 0.087 0.051 2879 1.24
71 0.060 0.024 0.543 1410 174 111 0.079 0.053 2817 3.0
72 0.057 0.025 0.371 1515 173 111 0.045 0.044 2788 1.9
73 0.011 0.0175 3.428 10'50 97 82 0.046 0.778 2555 ;4.6
74 0.011 0.015 0.342 1220 93 80 0.082 0.171 2599 1.4
75 0.014 0.018 0.298 1215 99 84 0.01 0.129 2583 6.5
76 0.014 0.018 0.285 1230 96 82 0.10 0.128 2546 4.2
77 0.018 0.021 3.314 1120 100 82 0.101 0.721 2544 15.6 78 0.011 0.016 0.614 1310 100 83 0.102 0.107 2492 3.3 105
C CO CO • H O H TJ • X) XA O rrj XA rrj •H DEPENDENT u H •P U -P H CO H Q O O rrj 0 0 3 O O VARIABLES H O EH O E-i CO CO CO O o o
RUN NO.
79 8.21 23 250 2560 6656 5 9180 — 0.062
80 9.45 16 250 2590 7326 18 9006 — 0.063
81 10.05 3 600 3075 7192 10 8805 — 0.028
82 10.00 32 100 3030 7078 46 8385 — 0.045
83 10.45 •9 400 2990 7226 34 8703 — 0.025
84 10.12 4 100 2990 7054 11.0 8853 — 0.069
85 10.59 2 500 3075 7292 14 8833 — 0.030
86 10.12 3 100 2985 7031 10 8162 — 0.047
87 10.50 8 400 2990 7190 38 8128 — 0.032
88 10.20 5 150 2990 7027 10 8449 — 0.028
89 10.58 4 350 3030 7252 14 8579 — 0.028
90 10.05 5 100 2800 7053 26 8703 — 0.017
91 10.40 3 500 2910 7164 32 9045 — 0.024
92 10.10 4 200 2915 6991 11 8253 — 0.023
93 10.40 4 550 3075 7125 14 8627 — 0.094
94 10.10 3 100 2905 6979 3 8162 — 0.032
95 10.40 9 450 2910 7093 40 8655 — 0.025
96 10.12 4 100 3040 6912 5 8504 — 0.056
97 11.52 7 100 2875 7332 10 8030 — 0.032
98 11.55 33 100 2985 7402 70 8374 — 0.030
99 11.60 20 100 2875 7368 38 8100 — 0.032
100 11.60 41 50 2895 7613 100 8380 -- 0.038
'101 11.60 6 250 2980 6636 13 8689 — 0.038 106
DEPENDENT VARIABLES
o O p 0) rd o I—I RUN NO. PL, O TO H E-<
79 0.024 0.020 1.942 1075 96 81 0.115 0.12 2542 17.9
80 0.018 0.015 0.814 1270 102 85 0.095 0.236 2583 6.8
81 0.007 0.0143 1.57 1712 90 76.20 0.20 0.21 3073 1.75
82 0.014 0.0121 1.96 1712 103 76.75 0.39 0.12 3021 8.60
83 0.014 0.0028 0.25 1725 75.4 0.17 0.18 2987 3.40
84 Tr 0.0054 0.66 1719 89 76 0.13 0.15 2986 3.6
85 Tr 0.0060 0.32 1721 88 "'75.9 0.13 0.19 3073 2.1
86 Tr 0.0028 0.57 1714 90 76.2 0.22 0.10 3981 3.6
87 0.007 0.0027 0.19 1775 88 76.3 0.14 0.19 2988 1.7
88 Tr 0.0043 0.67 1512 101 75.2 0.14 0.14 2989 1.4
89 0.007 0.0064 0.29 1788 88 75.4 0.15 0.10 3027 2.8
90 : Tr 0.0047 2.0 1721 100 75.2 0.15 0.13 2799 0.9
91 0.007 0.0027 0.30 1719 90 76 0.15 0.22 2906 3.6
92 0.007 0.0092 0.51 1712 100 76.7 0.14 0.13 2912 2.85
93 0.014 0.0121 0.28 1721 96 75.1 0.13 0.16 3071 3.55
94 0.020 0.0054 0.48 1687 99 76.3 0.14 0.10 2904 1.2
95 0.014 0.0094 0.18 1712 87 75.3 0.21 0.16 2908 1.5
96 0.014 0.0028 0.61 1575 96 75.15 0.13 0.13 3039 0.8
97 0.014 0.0026 0.11 1956 98 76.75 0.21 0.03 2875
98 0.014 0.0836 0.82 1844 86 76.70 0.28 0.03 2981 4.4
99 Tr 0.0236 0.57 1900 89 77.2 0.22 0.03 2866 8.5
100 0.036 0.0130 1.30 1788 90 76.3 0.28 0.04 2885 9.75
*101 Tr 0.0064 0.83 1575 97 77.8 0.16 0.04 2978 2.2 107
DEPENDENT VARIABLES
id 3 Solid s CO D Solid s Suspende d Carbo n Tota l
Turbidit y Tota l o RUN NO. a Colou r o o
102 11.63 28 100 3005 7663 73 8936 — — 0 .054
103 11.50 17 100 2950 7585 12 8323 — — 0 .028
104 11.52 5 100 3050 7586 7 8378 — — 0 .023 108
DEPENDENT VARIABLES o O -Q rrj rd o 1—I RUN NO. U O Ph EH u, 102 0.043 0.0121 0.96 2037 90 76.75 0.12 0.05 2995 10.25
103 0.020 0.0171 0.63 1912 99 77.8 0.09 0.03 2941 9.4
104 0.014 0.0070 0.10 1844 89 77.4 0.34 0.01 3044 6.0