TlLEAl
 ^ IfrfrM^  WATER POLLUTION CONTROL RESElatt« SERIES • '4010 EIZ 12/71
 Studies of Limestone Treatment

      of Acid Mine Drainage
              Part  II
     U.S. ENVIRONMENTAL PROTECTION AGENCY

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           WATER POLLUTION CONTROL RESEARCH SERIES

The Water Pollution Control Research Series describes the
results and progress in the control and abatement of pollution
in our Nation*s waters.  They provide a central source of
information on the research, development,  and demonstration
activities in the Environmental Protection Agency, through
inhouse research and grants and contracts  with Federal, State,
and local agencies, research institutions, and industrial
organizations.

Inquiries pertaining to Water Pollution Control Research Reports
should be directed to the Head, Publications Branch (Water),
Research Information Division, R&M, Environmental Protection
Agency, Washington, B.C. 20460.

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Studies of Limestone  Treatment of Acid Mine Drainage
                             Part  II
                                by
                  Bituminous Coal Research, Inc.
                              for the
                   Commonwealth of Pennsylvania
               Department of Environmental Resources
                              and the


                   ENVIRONMENTAL PROTECTION AGENCY
                      EPA Grant No. 14010 EIZ
                           December 1971
    For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402 - Price $1.25

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                   EPA Review Notice
This report has been reviewed by the Environmental
Protection Agency and approved for publication.   Approval
does not signify that the contents necessarily reflect
the views and policies of the Environmental Protection
Agency, nor does mention of trade names or commercial
products constitute endorsement or recommendations for
use.
                              ii

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                               ABSTRACT
Laboratory studies were conducted with limestone as the neutralizing
agent for coal mine water.  Batch tests were used to determine the
properties of limestone necessary for effective neutralization.
Continuous flow tests were used to determine conditions required for
an effective neutralization process.

The following variables are of importance for limestone to be an
effective neutralizing agent:  (a) particle size, (b) Ca and Mg content,
and (c) surface area.  Limestones having the smallest particle size
commercially available were tested and found to be effective if crite-
ria for variables other than particle size were met.

Data obtained with a small laboratory continuous flow test apparatus
were used in determining operating conditions for a continuous treat-
ment process for neutralizing mine water with limestone.  An evaluation
of this process indicated technical feasibility, advantages and dis-
advantages, and need for further study of certain aspects of this
process.

The cost of treating coal mine water with the BCR limestone treatment
process compares favorably with the published costs of treating mine
water by other processes.

This report was submitted in fulfillment of Project Number 1^)10 EIZ
under the joint sponsorship of the Water Quality Office of the
Environmental Protection Agency, the Commonwealth of Pennsylvania, and
Bituminous Coal Research, Inc.
                                  111

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                               CONTENTS


Section                                                             Page

     I    Conclus ions ............................................     1

    II    Recommendations ........................................     3

   III    Introduction ......................................... . .     5

            Objectives ...........................................     5
            Nature and Scope of the Problem ......................     5
            Approach to the Problem and Research Procedure .......     7

    IV    Description of Pilot Plant .............................    11

            Materials and Equipment ..............................    11
            Detention Time Study to Quantify Efficiency of
              Reactor ............................................    iM-

     V    Experimental ...........................................    17

            Analytical Procedures ................................    17
            Evaluation of Limestones .............................    17
            Continuous Flow Experiments ....... . ..................    21
            Sludge Properties ......... , ..........................    25

    VI    Results and Discussion of Laboratory Studies ...........    27

            Evaluation of Limestones .............................    27
            Continuous Flow Experiments ..........................    78

   VII    Evaluation of BCR Limestone  Treatment Process ..........   103
            Description of Individual Treatment Units ............
            Flow Schematics, Unit Designs, and Material
              Balances ...........................................   106
            Summary Technical Evaluation of the Process ..........   107
            Cost Evaluation of the Process .......................   12 4

  VIII    Acknowledgments ........................................   137

    IX    References ............. , ...............................   139

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                                FIGURES

                                                                 PAGE

 1     Flow Diagram of Conceptual Limestone Treatment Process.0.     8

 2     General View of Continuous Flow System	    12

 3     Continuous Flow System	    13

 k     Detention Time Study - Limestone Reactor	    15

 5     Apparatus for Neutralization of Coal Mine Water	    20

 6     Numbered Tanks for System of Nomenclature	    23

 7     Effect of Particle Size of Limestone No. 1809 on
         Neutralization of Synthetic Coal Mine Water	    31

 8     Model Curve for Judging Effectiveness of Limestones I...0    3^-

 9     Model Curve for Judging Effectiveness of Limestones II...    ^1

10     Effect of Particle Size of Limestones on Neutralization
         of Synthetic Coal Mine Water	0    62

11     Effect of Particle Size of Limestones on Neutralization
         of South Greensburg Coal Mine Water	    63

12     Effect of Particle Size of Limestones on Neutralization
         of Thorn Run Coal Mine Water	    6k
13     Neutralization of Synthetic Coal Mine water with Finely
         Divided Limestones "As Received"	0.   65

Ik     Neutralization of Synthetic Coal Mine Water with Finely
         Divided Limestones (After Pulverizing)	   66

15     Neutralization of South Greensburg Coal Mine Water with
         Finely Divided Limestones "As Received"	   67

16     Neutralization of South Greensburg Coal Mine Water with
         Finely Divided Limestones (After Pulverizing)	„ „ 0   68

17     Neutralization of Thorn Run Coal Mine Water with Finely
         Divided Limestones "As Received"„	„„..   69

18     Neutralization of Thorn Run Coal Mine Water with Finely
         Divided Limestones (After Pulverizing)	   70
                                  vii

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                              FIGURES

                                                                 PAGE

19     Settling Behavior of Sludge ..............................   7^

20     Lime Versus Limestone Sludge after Settling for Five
         Minutes and Thirty Minutes .. .......................... .   ?6
21     Lime Versus Limestone Sludge after Settling for One
         Hour and One Week0 .................................... .   77

22     Effect of Aeration and Sequence of Unit Operations on
         Continuous Flow Treatment of South Greensburg Coal
         Mine Water .............................................   8U
23     Effect of Volume of Slurry Recirculated on Continuous
         Flow Treatment of South Greensburg Coal Mine Water . « . . .   9^

2k     Effect of Aging on Solids Content of Sludge Formed in
         Continuous Flow Experiments ............................   99

25     Plant Flow Schematic, Plant Flows and Unit Design Basis
         for 0.1 mgd Limestone Treatment Plant for Class I Coal
         Mine Drainage ...0 .................... „ ............. «...  10 8

26     Plant Flow Schematic, Plant Flows and Unit Design Basis
         for 1.0 mgd Limestone Treatment Plant for Class I Coal
         Mine Drainage . . . „ . „ ................................. <>..  109

27     Plant Flow Schematic, Plant Flows and Unit Design Basis
         for 7«0 mgd Limestone Treatment Plant for Class I Coal
         Mine Drainage .......................... . ........ „ ......  110

28     Plant Flow Schematic, Plant Flows and Unit Design Basis
         for U.O mgd Limestone Treatment Plant for South
         Greensburg Coal Mine Drainage ..........................  Ill

29     Plant Layout and Hydraulic Profile for k.O mgd Limestone
         Treatment Plant for South Greensburg Coal Mine
         Drainage ........ . ............................ „ ....... 0.  11?

30     Material Balance for Limestone Treatment of Class I,
         Case A Coal Mine Drainage at 0.1 mgd Flow Rate ..... «...  113

31     Material Balance for Limestone Treatment of Class I,
         Case B Coal Mine Drainage at 0.1 mgd Flow Rate .........
32     Material Balance for Limestone Treatment of Class I,
         Case C Coal Mine Drainage at 0.1 mgd Flow Rate .........  115
                               viii

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                                FIGURES

                                                                  PAGE

33     Material Balance for Limestone Treatment of Class I,
         Case A Coal Mine Drainage at 1.0 mgd Flow Rate	  116

3^-     Material Balance for Limestone Treatment of Class I,
         Case B Coal Mine Drainage at 1.0 mgd Flow Rate	  117

35     Material Balance for Limestone Treatment of Class I,
         Case C Coal Mine Drainage at 1.0 mgd Flow Rate	  118

36     Material Balance for Limestone Treatment of Class I,
         Case A Coal Mine Drainage at 7.0 mgd Flow Rate	  119

37     Material Balance for Limestone Treatment of Class I,
         Case B Coal Mine Drainage at 7.0 mgd Flow Rate	,...  120

38     Material Balance for Limestone Treatment of Class I,
         Case C Coal Mine Drainage at 7.0 mgd Flow Rate	„...  121

39     Material Balance for Limestone Treatment of South
         Greensburg Coal Mine Drainage at U.O mgd Flow Rate......  122
                                  IX

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  TABLES




                                   PAGE
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18


Evaluation of Limestones with South Greensburg Coal
Relative Effectiveness of Limestones with Synthetic and
Evaluation of Limestones with Dilute Sulfuric Acid and
Evaluation of Limestone with Dilute Sulfuric Acid and
Relative Effectiveness of Limestones with Synthetic and
South Greensburg Coal Mine Waters and with Dilute
Sulfuric Acid 	 	 	

Particle Size Analyses of Twelve Finely Divided
Particle Size Analyses of Twelve Finely Divided
Particle Size Analyses of Twelve Finely Divided
Limestones as Received and Pulverized - Percent
Passing 200 Mesh 	 	
Moisture Content of Twelve Finely Divided Limestones . . . . 0
Neutralization Data for Limestone No. 2501 and 2501-P....
Neutralization Data for Limestone No. 2502 and 2502-P....
Neutralization Data for Limestone No. 2503 and 2503-P0<>00
Neutralization Data for Limestone No. 2504 and 2504-P.00.
Neutralization Data for Limestone No, 2522 and 2522-P..0.
?Q
3^>
33
35
37
3^
3°*
42
44
4s
46
47
48
49
50
51
52
XI

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                              TABLES

                                                                 PAGE

19     Neutralization Data for Limestone No.  2523 and 2523-P ----    53

20     Neutralization Data for Limestone No.  2^kk and 25^-P-.-.    ^

21     Neutralization Data for Limestone No.  25^5 and 25^5-P. . . .    55

22     Neutralization Data for Limestone No.  25^7A and
23     Neutralization Data for Limestone No.  25^7B and
         25V/B-P ................................................   57

2h     Neutralization Data for Limestone No.  2576 and 25?6-P....   58

25     Neutralization Data for Limestone No.  2577 and 2577-P....   59

26     Relative Area Under Neutralization Curves - Twelve
         Finely Divided Limestones with Synthetic and Two
         Actual Coal Mine Waters ................................   6l

27     Evaluation of Five Additional Materials with Synthetic
         Coal Mine Water ........................................   72

28     Properties of Sludge Formed in Batch Neutralization
         Experiments ............................................   73

29     Effect of Flow Rate and Amount of Limestone on Continuous
         Flow Treatment of South Greensburg Coal Mine Water
         No Slurry Recirculated .................................   80

30     Effect of Aeration and Sequence of Unit Operations on
         Continuous Flow Treatment of South Greensburg Coal
         Mine Water ................ . ............................   82

31     Effect of Slurry Recirculation and Aeration in One Tank
         on Continuous Flow Treatment of South Greensburg Coal
         Mine Water .............................................   85

32     Effect of Flow Rate and Aeration in One Tank on
         Continuous Flow Treatment of South Greensburg Coal
         Mine Water. . „ ..........................................   86

33     Effect of Slurry Recirculation and Aeration in Two Tanks
         on Continuous Flow Treatment of South Greensburg Coal
         Mine Water ............................................ 0   88
                                XII

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                                TABLES

                                                                 PAGE

3^     Effect of Flow Rate and Aeration in Two Tanks on
         Continuous Flow Treatment of South Greensburg Coal
         Mine Water	„...    89

35     Effect of Slurry Eecirculation and Ux the Stoichiometric
         Amount of Limestone on Continuous Flow Treatment of
         South Greensburg Coal Mine Water	    91

36     Effect of the Volume of Slurry Recirculated on
         Continuous Flow Treatment of South Greensburg Coal
         Mine Water	    93

37     Effect of the Volume of Slurry Recirculated on
         Continuous Flow Treatment of South Greensburg Coal
         Mine Water.	    95

38     Continuous Flow Treatment of Thorn Run Coal Mine Water..    96

39     Properties of Sludge Formed in Continuous Flow
         Experiments with No Slurry Recirculated	    98

Uo     Properties of Sludge Formed in Continuous Flow
         Experiments with Recirculated Slurry	   100

Ul     Effect of Shape of Vessel on Solids Content of Sludge...   102

h2     Estimate of Capital Cost for Limestone Treatment Plant
         to Treat Class I Coal Mine Drainage 0.1 mgd Flow
         Rate	   12?

lj-3     Estimate of Capital Cost for Limestone Treatment Plant
         to Treat Class I Coal Mine Drainage at 1.0 mgd Flow
         Rate	   128

hk     Estimate of Capital Cost for Limestone Treatment Plant
         to Treat Class I Coal Mine Drainage at 7.0 mgd Flow
         Rate	   129

il5     Estimate of Capital Cost for Limestone Treatment Plant
         to Treat South Greensburg Coal Mine Drainage at
         h.O mgd Flow Rate	   130

U6     Basis for Estimated Costs of Limestone Treatment of Coal
         Mine Drainage Presented in Table k2, Table ^3,
         Table kk, and Table ^5	   131
                                 Xlll

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                              TABLES

                                                                  PAGE

lj-7     Estimated Costs of Limestone Treatment of WQp, EPA
         Class I Case A Coal Mine Drainage.  All Costs
         Reported as Cents per 1,000 Gallons of Water
         Treated. <>...<, 0»	o	o	•	

1+8     Estimated Costs of Limestone Treatment of WQP, EPA
         Class I Case B Coal Mine Drainage.  All Costs
         Reported as Cents per 1,000 Gallons of Water
         Treated	  132

49     Estimated Costs of Limestone Treatment of WQp, EPA
         Class I Case C Coal Mine Drainage.  All Costs
         Reported as Cents per 1,000 Gallons of Water
         Treated	o  133

50     Estimated Costs of Limestone Treatment of South Greensburg
         Coal Mine Drainage.  All Costs Reported as Cents per
         1,000 Gallons of Water Treated	  133

51     Comparison of Costs for Treating Mine Drainage	
                                 xiv

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                               SECTION I

                              CONCLUSIONS
Studies on the limestone treatment of coal mine drainage have led to
the following conclusions:

1.   A process has been developed whereby coal mine drainage containing
ferrous iron can be treated with limestone.  This process results in
complete neutralization of acidity and removal of iron to acceptable
limits.

2.   The BCR limestone treatment process consists of the following
unit operations in sequence:  (a) mine drainage holding or equalization,
(b) adding pulverized limestone and mixing, (c) aerating, (d) slurry
recirculation to the mixing area, (e) sludge settling, and (f) sludge
dewatering and disposal.

3.   The advantages of using limestone instead of lime are lower costs
per unit weight of chemical reagent necessary to neutralize the same
quantity and quality of coal mine drainage, fewer safety problems in
handling a less reactive reagent, and a less harmful effect on the
body of water receiving the effluent in case of accidental overtreatment.
An additional advantage is a reduction in sludge volume and an increase
in sludge solids content.  In fact, the volume of sludge from limestone
treatment can be as little as one-fifth that from lime treatment, and
the solids content of the limestone sludge can be almost 15 times
greater than that from treatment with lime.  This reduction in sludge
volume would mean that smaller settling basins would be required.  This
fact, by itself, may be sufficient reason for selecting limestone treat-
ment over lime in areas where space is at a premium.

k.   The major disadvantage of the process can be attributed to the
slow rate of oxidation of ferrous iron at the relatively low pH
attainable with limestone.  Long detention times and, consequently,
big tanks are required for mixing the mine water with limestone and
for aerating until most of the ferrous iron has been oxidized.  This
would result in higher costs and inefficient mixing, diffusion of
oxygen, and sparging of carbon dioxide.  Other disadvantages of the
process include the production of fine particles in the effluent,
which do not settle rapidly and may require coagulant aids for their
removal, and the questionable availability of finely divided limestone
of the desired quality.

5.   For use in a treatment operation, the particle size of the lime-
stone should be 7^ microns (200 mesh) and preferably smaller.  In
addition, the limestone should approach pure calcium carbonate in
composition.  Those stones which have a relatively low calcium content,

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but which contain calcite and have a high surface area, are equally
effective neutralizing agents.  Magnesites are the least effective
neutralizing agents, followed closely by dolomitic limestones.

6.   Coal mine waters containing ferrous iron in quantities as great
as 5)000 mg/1 (such as those waters used for the technical and cost
evaluations) present particular problems in treatment which have not
been solved.  Treatment of such waters would result in precipitation of
calcium sulfate (gypsum) during treatment with resultant scaling
problems on tanks, pipes, mixers, aerators, and pumps.  Also, the
volume of sludge would be greater than the volume of treated water
obtained.  These two problems are inherent in both limestone and lime
treatment.

7-   The cost of treating coal mine water with the BCR limestone
process compares favorably with the published costs of treating mine
water with other processes.  Chemical costs for treating, using the
BCR limestone process, were 5.0 to 5-8 cents per mg/1 of acidity per
1,000,000 gallons.  Total costs for treating coal mine discharges within
the limits of quality normally encountered, ranged from 13.6 to 97.3 cents
per 1,000 gallons of water.  These costs include sludge disposal.

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                              SECTION II

                            RECOMMENDATIONS


The following additional studies are recommended:

1.   To optimize the BCE limestone treatment process, a pilot plant
such as a field research unit or equivalent should be utilized as
follows:

     a.   Bench-scale tests were conducted with diffused air
     for aeration and sparging of carbon dioxide.  Future
     studies should be directed toward use of more efficient
     mechanical aerators to determine if adequate sparging of
     carbon dioxide is accomplished with the mechanical-type
     aerator.

     b.   Units permitting continuous build up of sludge should
     be employed to study the sludge to raw feed requirements
     to determine if smaller volumes of more concentrated
     sludge can be used to accomplish the required treatment.

     c.   Further studies should be conducted on coal mine
     waters having sulfate concentrations of up to 20,000 mg/1,
     as formation of calcium sulfate would occur at these con-
     centrations and would have a significant effect on the
     volume of sludge precipitated as well as result in
     problems of scaling on equipment such as mixers, aerators,
     etc.

     d.   Tests should be conducted to determine the effect of
     coagulant aids on settling rates and volumes of sludge to
     possibly reduce the detention time in and, therefore, the
     size of the settling basins.  The effect of coagulated sludge
     on sludge recycling should also be determined.

     e.   Data obtained through this bench-scale study indicate
     sludge volume will be significantly lower than with lime
     treatment.  This should be verified in large scale units
     and with more concentrated coal mine drainage.

2.   The effect on cost of on-site grinding of coarse limestones to
the desired size by such means as an autogeneous grinder should be
studied and compared with the cost effect of using pulverized limestone.

3.   Studies should be conducted on a scale as large as an actual treat-
ment plant operation to determine the requirements and velocities
necessary to provide adequate mixing and to prevent the deposition of
solids.

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k.   Studies with a field research unit or equivalent pilot plant should.
incorporate the most recent information developed to increase the rate
of ferrous iron oxidation in the coal mine water, such as by catalytic
oxidation.

5.   Although the emphasis during this study has been on treatment of
waters containing iron in the ferrous state, the tests conducted on
Thorn Run water, which contains iron principally in the ferric state,
indicate that treatment of this type of water is less complicated,
since the factors associated with the oxidation of ferrous iron are
not present.  A significant percentage of mine discharges are of the
ferric iron type; therefore, it is recommended that additional laboratory
studies be conducted to optimize the BCE limestone treatment process
for this type of water.  Practical application of the process to treat-
ment of actual mine waters could, then,  be brought about more quickly.

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                               SECTION III

                              INTRODUCTION
This is the final and summary report on the Pennsylvania Department
of Environmental Resources Project CR-75-A1 activated November 10,
with financial support from the Pennsylvania Coal Research Board and
the Federal Water Quality Administration2 through Grant 1^010 EIZ to
the Commonwealth of Pennsylvania.  The project is based on work con-
ducted on Pennsylvania Coal Research Board Project CR-75 activated
July 1, 1967, with financial support from the Pennsylvania Coal
Research Board, Bituminous Coal Research, Inc., and the United Mine
Workers of America, and expanded February 7> 1968, with additional
financial support through Grant WPRD 63-01-68 to the Commonwealth of
Pennsylvania by the Federal Water Quality Administration, (l)3

Work on the project was conducted according to the BCR Research Program
Proposal RPP-162R submitted to the Pennsylvania Coal Research Board on
April 2k, 1969, as revised in the Revision of Scope dated February 20,
1970, and submitted as a result of meetings between the sponsors and
project personnel.  The experimental work was conducted during the
period November 10, 1969 to June 25, 1971.
                               Objectives

 The  overall, long-range objective of the program is to design and
 develop to pilot-plant stage an improved process for the control and
 prevention of pollution of waters by drainage from coal mines.

 The  objectives  of the studies  conducted in the period covered by this
 report were:   (a) to improve and optimize the chemical techniques
 involved  in the limestone treatment of coal mine drainage with emphasis
 placed on the evaluation of limestones and continuous flow tests, and
 (b)  to utilize  the information developed in these studies for both a
 technical evaluation and a cost evaluation of the BCR limestone process
 projected for full-scale operation.
                     Nature and Scope of the Problem

The occurrence of acid drainage associated with coal mining has been
well documented. (2)  In the Appalachian region alone, more than
5,000 miles of streams are adversely affected on a continuing basis
by drainage resulting from the mining of coal.  The coal  industry  is
1 Formerly the Pennsylvania Coal Research Board Project  CR-75-A.
3 Currently the Water Quality Office of the Environmental  Protection
 Agency  (WQO, EPA).
3Numbers in parenthesis indicate references listed at end of  report.

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proceeding with a vigorous abatement program by constructing water
treatment plants wherever polluting waters might be discharged from
active mines into open streams.  At the present time, there are over
200 mine water treatment plants built and operating in the state of
Pennsylvania alone.  Also, an additional 100 plants are in various
stages of design and construction. (3)

In all but a few cases, lime neutralization, often in conjunction with
aeration and settling ponds, is the type of treatment used.  However,
the relatively high cost of lime and the poor sludge quality (slow
settling, large volumes, and low solids content) have stimulated work
in the utilization of limestone, (^)  The claimed advantages of lime-
stone neutralization over lime neutralization are:  (a) lower costs
for chemical reagent, (b) decreased hazard to the operator handling
a less reactive reagent, (c) little or no harmful effect on streams
and stream life from an accidental overtreatment , and (d) potential
for decreased sludge volume by an increased solids content in sludge.

Recent reports in the literature tend to confuse rather than clarify
the issue of limestone treatment.  One such report (5) describes the
limestone treatment of a coal mine water containing iron principally
in the ferric, Fe3"1" , state and concludes that their studies resulted
in successfully "treating mine waters of the wide range of acidity and
iron normally encountered."  The same report "recommended that, to
effect maximum economics in treatment costs and in land conservation,
consideration be given to the use of the limestone neutralization
process wherever other treatment processes are now in use or con-
templated. "

Conversely, a more recent study concludes that "he who tries to treat
large quantities of acid mine water containing high proportions of
ferrous iron with a straight calcium carbonate neutralizer is likely
to be in for some real interesting and expensive experiences." (6)

The key phrase is "ferrous iron."  There are fundamental differences
in treating water containing iron in the ferrous , Fe3* , state and
water containing iron in the ferric, Fe3'1' , state.  In the treatment
of ferric iron waters, only neutralization is involved since the
system has already attained equilibrium with respect to iron and,
therefore, no further acid will be generated during treatment.

In contrast, the neutralization of ferrous iron waters also involves
oxidation which, in turn, generates more acid.  This can be repre-
sented by the following (unbalanced) reaction:

                   Fe2* + Oa + HgO -*Fe(OH)3 + if
If the oxidation proceeds slowly,  acid is generated slowly, requiring
further neutralization.   With lime,  an additional amount can be
added, which raises the  pH substantially and speeds up the oxidation,

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since a hundredfold increase in the rate of ferrous iron oxidation is
reported per unit increase in pH. (7)  On the other hand, an excess
quantity of limestone will not raise the pH sufficiently high to
increase the rate of ferrous iron oxidation, since limestone is only
a weakly "basic material.

The present program of laboratory investigation was designed to
resolve some of the difference in results reported and to design a
limestone treatment process that would be applicable to all types
of mine waters.
             Approach to the Problem and Research Procedure

A neutralization process for coal mine drainage entails a series of
individual unit operations .  One general concept of the limestone
neutralization process is  shown in Figure 1.  The individual parts
of the total system are:   (a) holding tank,  (b) pulverized limestone
storage tank, (c) limestone feeder, (d) limestone reactor, (e) aerator,
(f) settling tank,  (g) optional sludge recirculation, (h) optional
oxidation catalyst, and  (i) optional coagulant aid.
For a mine water containing ferrous iron  (FeS04 ) and free acid
the overall neutralization reaction using limestone (CaC03 ) and
including oxidation can be represented in the following simplified
manner:

3  CaC03  + 2 FeS04  + HsS04 + 0.5 03 + 2 HgO -» 3  CaS04 + 2 Fe(OH)3 + 3 C0
The products of this reaction are hydrated ferric hydroxide (yellow-
boy) , gypsum, and carbon dioxide gas which must be removed by sparging.

To develop and optimize a limestone neutralization process and thereby
achieve the stated objectives of this program, work was conducted in
the following categories :

Evaluation of Limestone — Preliminary experiments were conducted using
limestones of various size consists and a number of synthetic and
actual coal mine waters.  Then, commercially available finely divided
limestones were used in batch tests as neutralizing agents; it had
been established (8) that, for use in a treatment operation, the
particle size of the limestone should be 7^ microns (200 mesh) and
preferably smaller.

Sludge properties were measured from selected batch tests as part of
the evaluation of these limestones.

Continuous Flow Experiments — Two actual coal mine waters were treated
with limestone utilizing a small laboratory pilot plant to determine
basic operating conditions required to neutralize acid mine drainage.

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        Sludge
 G    Recirculation
       (Optional)
                                     Coal
                                     Mine
                                    Water
                                   Holding
                                     Tank     A
                                  Limestone
                                    Reactor
                                      D
                                   Aerator

                                      E
                                   Settling
                                     Tank
                                   Sludge To
                                   Disposal
        Pulverized
        Limestone
          Storage
           Tank
Limestone
 Feeder
                                                              Oxidation
                                                               Catalyst   H
                                                              (Optional)
                                                      Air
        Coagulant Aid  j
          (Optional)

         Treated Water
              To
        Receiving Stream
                                                Bituminous Coal Research, Inc. 2036G15
Figure 1.  Flow  Diagram  of Conceptual  Limestone Treatment  Process
                                     8

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Properties of the sludges from selected experiments were measured as
part of the evaluation of the effectiveness of continuous treatment.

Technical and Cost Evaluations—As the final phase of the project,
information gained from the laboratory "batch studies and continuous
flow studies of the limestone treatment process was utilized in a
technical and cost evaluation of the BCR limestone treatment process
as projected for full-scale operation.

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                               SECTION IV

                       DESCRIPTION OF PILOT PLANT
A continuous flow test apparatus was designed and constructed for
use in evaluating the limestone neutralization process.  This test
apparatus was a modification of a unit originally designed and
constructed for use on Pennsylvania Coal Research Board Project
CR-75 conducted at BCR. (l)  A photograph of the actual system is
shown in Figure 2.
                         Materials and Equipment

Figure 3 is an artist's conception of the continuous flow system,
indicating the location of the holding tanks, etc.  The following
paragraphs describe the equipment and the materials used in its
construction.

Holding Tanks:  The two Glascote glass-lined holding tanks each have
bottom discharge and lids.  The tanks have 90-gallon and 60-gallon
capacities, for a total capacity of 150 gallons.

Sample Cooling and Circulating System:  The Forma "Forma-Temp"
portable cooler can maintain the sample at temperatures as low as
k6 F.  The cooler has a rated capacity of ^,000 Btu/hr.  Circulation
of the sample between the two holding tanks is accomplished by use
of a Gorman-Rupp Model 11698, 5600 series, centrifugal pump, with a
Gorman-Rupp Model 12500-21 oscillating pump used for priming.

Limestone Reactor:  The stirred-tank reactor consists of a 60-gallon
stainless steel tank equipped with four 3-inch stainless steel baffles.
Stirring is accomplished by use of a "Lightnin" Model ND-1A, I/if
horsepower, 1,750 rpm motor, 350 rpm propellor, portable mixer equipped
with two 7-7-inch diameter "Super Fitch" propellers.  All wetted parts
of the mixer are of 30^ stainless steel.  The sample is transferred
to the stirred-tank reactor from the holding tanks using a Gorman-
Rupp Model 11698, 5600 Series centrifugal pump.  The flow rate is
controlled by a 1/2-inch Whitey Model ^558-316 stainless steel ball
valve and is measured by a Brooks Model 1305 flowmeter.  Compressed
air can be introduced into this tank through a manifold consisting of
four spherical gas diffuser stones (Fisher Scientific) mounted at the
end of 3/l6-inch stainless steel tubing.  The diffuser stones are
directly under the lower propellor two inches from the bottom of the
tank and two inches from the propellor.  The other propellor is
mounted 15 inches above the lower propellor and 6 inches below the
surface of the water when the tank has been filled to the 50-gallon
level.
                                    11

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                                                            (2036P5)
Figure 2. General View of Continuous Flow System

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H
UJ
                                                           Legend


                                                                A - Holding Tanks

                                                                B - Limestone Hopper

                                                                C - Limestone Feeder
D - Limestone Reactor

E - Aeration Tank

F - Settling Tanks
                                                   ^  ^.          ^
                                        Figure 3.  Continuous Flow System
                                        v        ^     ~-
                                                                               D '                  '
                                                                               Bituminous Coal Research, Inc. 2036G18

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Limestone Feeder;  Pulverized limestone is fed to the reactor by a
Vibra Screw feeder composed mainly of a 3-cu ft  Live Bin,   a mechan-
ical variable speed drive, a trough, and 1/4-inch diameter  feed screw.

Aeration Tank:  The polyethylene cylindrical tank has a capacity of
60 gallons and has an air manifold identical to the one mentioned
above.  The sample can be transferred to the aeration tank  rrom
limestone reactor using a Gorman-Rupp Model 11698, 5&00 Series
centrifugal pump.  The flow rate is controlled by a 1/2-inch W
Model 4558-316 stainless steel ball valve and is measured by a Brooks
Model 1305 flowmeter.

Settling Tanks:  Two 105-gallon polyethylene settling tanks are used
to collect the sludge.  A third 105-gallon polyethylene tank is
available for storage of the sludge to be recirculated.  The sample
can be transferred to the settling tanks from the aeration  tank using
a Gorman-Rupp Model 11882-2, 200 series, centrifugal pump.   The flow
rate is controlled by a 1/2-inch Whitey Model 4558-316 stainless
steel ball valve and is measured by a Brooks Model 1305 flowmeter.
The sludge can flow by gravity from the first to the second and third
settling tanks.

Piping:  Piping  is  stainless steel, except for the large diameter
flexible Tygon connectors between the settling tanks.

An auxiliary portable pumping system consists of a Gorman-Rupp
Model 11698, 5600 Series centrifugal pump and a Gorman-Rupp Model
12500-21 oscillating pump.  A second portable system, used primarily
for recirculating sludge, consists of a Gorman-Rupp Model 11882-2,
200 Series centrifugal pump and a Gorman-Rupp Model 12500-21 oscil-
lating pump.
       Detention Time Study to Quantify Efficiency of Reactor

Studies using tracer techniques were initiated to determine the
detention time in the limestone reactor.  A solution of 570g of
NaCl dissolved in 2 liters of tap water was added spontaneously to
the stirred reactor tank which contained 50 gallons of tap water and
which was operating at an inflow-outflow rate of 1.0 gallons per
minute (gpm).  Conductivity readings were taken at the reactor dis-
charge at 30-second intervals for the first 2 minutes, every minute
for the next 3 minutes, and then every 5 minutes.  About 4 hours were
required for the salt to pass through the reactor, as shown in
Figure 4, by the conductivity returning to essentially the initial
reading.   Evidence of rapid mixing is also shown in this figure by
the peak of the conductivity curve occurring 60 seconds after the
addition of NaCl.  The data were fitted to a probability density
function (pdf).  From this, the average detention time (the expected
or mean value of the pdf) was 44.5 minutes.  The theoretical detention
                                  14

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H
VJl
CONDUCTIVITY,
MICRO MJHOS/CM
fl 6000-
5000-
4000-
3000-
2000-
1000-
0-
\
\
\
\
X
\
\.
X.
X.
^~--__


1 1 1 1 1 1 1 1 1 1 1 1
20 40 60 80 100 120 140 160 180 200 220 240
TIME, minutes
Bituminous Coal Research, Inc. 2036G34
                                   Figure 4. Detention Time Study—Limestone Reactor

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time was 50 minutes (gallons of water in limestone  reactor/flow rate,
gpmj.  Therefore, the efficiency of the  reactor  (average  detention
txme x 100/theoretical detention time) was  89.0 percent.
                               16

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                                SECTION V

                              EXPERIMENTAL
General procedures, including apparatus and analytical procedures for
evaluating the limestones and conducting the continuous flow experi-
ments, are reported here.
                          Analytical Procedures

Both raw mine water and treated water samples were analyzed routinely
for:   (a) ferrous iron colorimetrically using o-phenanthroline,
(b) cations, Si, Al, Fe, Ca, Mg, Mn, and Na, either by emission
spectrographic techniques using a Jarrell Ash Model 78-000 1.5 meter
Wadsworth grating spectrograph or by atomic absorption spectrophoto-
metric techniques using an Instrumentation Laboratory Model IL-153
atomic absorption spectrophotometer, (c) acidity by adding hydrogen
peroxide, boiling, cooling to room temperature, and titrating to
pH 8.2, and  (d) pH.
                        Evaluation of Limestones

Selected limestones were evaluated by consideration of (a) their
physical and/or chemical properties and (b) their effectiveness in
neutralizing coal mine water.

Materials

Tests were conducted with the Ik limestones which were used on
Pennsylvania Coal Eesearch Board Project CR-75. (l)  These were pro-
cured as fairly coarse material and pulverized to the desired size.

A number of the suppliers of the l4 limestones were contacted to
request information concerning rock dust and/or other finely divided
grades of limestone which might be commercially available.  Specific
information solicited included:  grades and quantities available,
cost at the source and cost of delivery, chemical and sieve analyses,
cost and method of grinding coarse fractions, and specifications for
a rock dust grade.  Bagged (80 Ib) quantities of finely divided lime-
stone were ordered, where available, for testing on this project.

Of the companies contacted, 11 responded and 9 of these supplied
samples.  Not all of the materials were specified as rock dust grade.
The cost per ton of the materials f.o.b. shipping point ranged from
$3.50 to $6.75 in bulk, from $5.50 to $10.00 bagged, usually in 80-lb
bags.  The cost of bagging the material was usually $2.50 per ton.
Grinding costs, based on limited available data, were approximately
$2.25 per ton.  Average cost of delivery was $0.05 per ton per mile.
                                    17

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Hypothetically, 10 tons of limestone (bulk) at an initial cost of
$1.50 per ton delivered 35 miles would have a total cost of $6.25 per
ton, while bagged limestone at $7-00 per ton delivered the same dis-
tance would have a total cost of $8.75 per ton.

Chemical and Physical Properties of the Limestones

The chemical composition of the individual limestones was determined
by conventional emission spectrographic techniques.  Structure was
determined by X-ray diffraction analyses utilizing a Picker Nuclear
powder diffraction unit.  Densities and surface areas of the limestones,
where applicable, were determined, respectively, with a Beckman air
pycnometer and either by the standard BET (Brunauer, Emmett, and Teller]
technique using nitrogen as the adsorbate at liquid nitrogen tempera-
tures or by a modified BET technique using a Micromeritics Model 2200
surface area analyzer.

Sampling the Finely Divided Limestones

The twelve finely divided limestones procured for use on this project
arrived at BCR laboratories in 50 or 80 Ib bags (in one case, in pails).
In each case, the contents of one of the containers was piled in a
cone (allowed to run down the apex of the cone equally in all direc-
tions to mix the sample) and spread in a circle to uniform thickness.
The flat pile was marked into quarters and the two opposite quarters
discarded.  The process of piling, flattening, and rejecting two
quarters was repeated (approximately five times) until the desired
quantity was obtained and stored in glass jars.  Samples for experi-
mentation and analyses were taken from these glass jars.

Sieve Analyses of the Finely Divided Limestones

For the sieve analysis of each of the finely divided limestones,
approximately 50.Og was weighed to an accuracy of at least 0.1 percent.
The sieves selected were:  Tyler mesh Wo. 20, 100, 200, and ^00.
Starting with the finest mesh sieve (No. ^00), each sieve, with a
solid pan at the bottom, was placed in a Ro-Tap Testing Sieve Shaker
until less than 0.05g of material passed the particular sieve in one
minute.

Synthetic Coal Mine Water

For these tests, fresh quantities of synthetic coal mine water were
prepared as needed.  Ferrous sulfate was added to deionized water to
yield a solution containing 250 mg/1 of Fes+ .  The pH of the solution
was then adjusted to 3.0 by addition of sulfuric acid.

In some tests, dilute sulfuric acid (pH 3.0) was employed in place of
the synthetic coal mine water.
                                  18

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Actual Coal Mine Waters

Most of the experiments with actual coal mine waters were conducted
using a water designated South Greensburg, a discharge from an inactive
drift mine in Westmoreland County, Pennsylvania.  During these tests,
the South Greensburg discharge contained from 69 to 98 mg/1 of ferrous
iron, from 1^0 to 199 nig/1 of acidity as CaCQ, equivalents, and had
a pH of ^.9 to 6.1.

The remainder of the experiments were conducted with a water desig-
nated Thorn Run which is actually from a reservoir also in Westmoreland
County, Pennsylvania, where a number of small discharges are impounded.
During these tests, the Thorn Ron discharge contained iron mostly in
the ferric state (typically about 150 mg/l), only small amounts of
ferrous iron, from 8^5 to 1,0^3 mg/1 of acidity as CaCOg equivalents,
and had a pH of 2.6 to 2.8.

General Procedure for Neutralization Reactions

Specified amounts of limestone were added to 1,500 ml of the water to
be neutralized.  The amount of limestone used was based on the acidity
of the water-  The mixture was stirred at a constant rate and aerated
at a rate of 2,500 ml/min continuously for a 5-hour period.  Aeration
was carried out by bubbling air into the mixture through a gas diffu-
ser at the bottom of the container.  Changes in pH were recorded with
time.  The apparatus for conducting these experiments is shown in
Figure 5«  An Orion Model ^01 meter with a Sargent/Jena combination
electrode was used to measure pH and a Houston Instrument Omnigraphic
T-Y recorder, Model HR-80, was employed to record changes in pH.

Neutralizing Efficiency of the Limestones

Evaluations of the limestones were based on consideration of the areas
under the neutralization curves as compared to the areas under simi-
lar curves prepared using either BCR limestone No. 1809 or No. 2177-
Relative areas under the neutralization curves were measured either
by (a) copying the curves on relatively constant-weight paper and
cutting out the area under each curve and weighing, or  (b) using a
planimeter-  The limestones were also evaluated by comparing the
neutralization curves with a composite neutralization curve of all
results of past tests.

The chemical composition, particle size, and crystalline structure of
the limestones as well as the pH, ferrous iron content, and acidity
of the mine water were also considered.

Effect of Particle Size

Ten experiments were conducted according to the general procedure.
A single limestone, BCR No. 1809, was pulverized and neutralization
curves prepared by adding 10 discrete particle size fractions each
                                  19

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ro
o
                                                                                              (2036P6)
                           Figure  5. Apparatus for  Neutralization of Coal Mine Water

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of No. 1809 to synthetic coal mine water.  The amount of limestone
used was twice the stoichiometric amount "based on the acidity of the
water.

Studies with Actual Coal Mine Water

Fourteen limestones, pulverized and sieved to a narrow particle size
range, 325 x ^00 mesh  (37 to hk microns), were each used with the
South Greensburg discharge.  The amount of limestone used was twice
the stoichiometric amount based on the acidity of this discharge.
Neutralization curves were prepared according to the general procedure.

Studies with Dilute Sulfuric Acid

Two series of neutralization experiments were conducted using the lU
pulverized limestones.  The amount of limestone was based on the
acidity of the test water, in this case, dilute sulfuric acid (pH 3-0).
In one series, the exact stoichiometric requirement of each of the
l4 limestones was used to prepare neutralization curves according to
the general procedure.  In the next series, the same procedure was
followed except for the use of twice the stoichiometric amount of each
of the ±k limestones.

Studies with the Finely Divided Limestones

A representative sample of each of the 12 finely divided limestones
was obtained.  Neutralization curves were prepared with each limestone
as received and with synthetic and two actual coal mine waters accord-
ing to the general procedure.  The amount of limestone used in each
case was twice the stoichiometric amount based on acidity of the
water.  Each limestone was again tested after having been passed once
through a pulverizing mill.
                       Continuous Flow Experiments

To determine basic operating conditions required to neutralize acid
mine drainage with limestone, two actual coal mine waters were treated
utilizing the small laboratory pilot plant which has been described
in the previous section.

Actual Coal Mine Waters

Most of the experiments were conducted using the water designated the
South Greensburg discharge.  During the continuous flow tests, the
South Greensburg discharge contained from ^0 to 105 mg/1 of ferrous
iron, from 1^0 to 228 mg/1 of acidity as CaC03 equivalents and had a
pH of k.6 to 5.6.  The iron in this water was principally in the
ferrous, Fe2+, state.
                                    21

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A few experiments were conducted with the water designated the Thorn
Run discharge.  During these tests,  the Thorn Run discharge contained
21 to 37 mg/1 of ferrous iron,  995 to 1,0^9 rag/1 of acidity as CaC03
equivalents and had a pH of 2. k to 2.8.  The iron in this water was
principally in the ferric, Fe3+ , state.  Total iron found in this
water was typically about 150 mg/1.

General Procedure for Continuous Flow Tests

A sample of mine water was brought to the BCR laboratories and the
continuous flow experiment conducted on the same day.  The holding
tanks and the limestone reactor were filled initially with 150 and
50 gallons, respectively, of this water.  The appropriate amount of
BCR Wo. 1809 limestone (of which 85 percent passed through a 200 mesh
screen) was added and the mixture stirred for 50 minutes when the
flow rate was 1.0 gpm or 100 minutes when the flow rate was 0.5
After this initial period, the flow of coal mine water was adjusted
to the specified rate, both from the holding tanks to the limestone
reactor and from the limestone reactor to the aeration tank.

Limestone was then added at a specified constant rate based on acidity
of the water.

Compressed air was fed into the aeration tank as it was being filled
to the 50-gallon mark; aeration was continued and the level held at
50 gallons by pumping the aerated sample into the settling tank.
Water remaining in the aeration tank at the end of the test was pumped
into the settling tanks .

Aliquots (200 ml) were withdrawn periodically from the mixing tank,
aeration tank, and the settling tanks; the pH, ferrous iron concen-
tration, and, at times, the acidity were determined on each.

System of Nomenclature for Continuous Flow Tests

The continuous flow system was designed in a flexible manner to permit
changes in the sequence of unit operations to be planned as part of
the test program.  It was necessary, therefore, to devise the following
system of nomenclature for describing the numerous conditions and
sequence of operations possible in these flow experiments.

The general procedure used for treating coal mine water with limestone
utilizing the continuous flow pilot plant shown in Figure 3 has just
been described.  The sequence of unit operations specified in that
description was (a) mixing the limestone and mine water in the lime-
stone reactor followed by (b) aeration in a separate tank.  The lime-
stone reactor tank, which was also equipped to accomplish aeration and
in which the limestone was always added, was designated tank No. 1.
The aeration tank was designated tank No. 2.  The numbered tanks are
shown in Figure 6.  Aeration in the selected tank was specified as "A"
                                  22

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                                            (2036P7)
Figure 6. Numbered Tanks for  System of  Nomenclature
                        23

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and no aeration in the tank "N."  The general procedure was then
labeled 1N-2A, mixing the limestone and mine water with no aeration
in tank No. 1 followed by aeration in tank Wo. 2.   If aeration was
accomplished first in tank No.  2 and then the aerated water mixed
with limestone in the reactor,  that experiment was labeled 2A-1N.
In that manner, "2A" and "IN" were considered two  distinct unit
operations .

The labeling system was then carried one step further.  If, in the
sample 2A-1N experiment, the slurry, "(S)", the mixture of sludge
and treated water, was recirculated and added to the raw mine water
during the first unit operation, this experiment was labeled 2A(S)-1W.

In this manner the experiments  were designed and labeled to include
the various combinations of unit operations including the addition of
recirculated slurry to one of two tanks .

Recirculation of the slurry (sludge plus treated water) resulting from
this process only begins to simulate conditions of actual sludge re-
circulation.  Neither time nor  sufficient funds were available to
redesign the continuous flow system once the necessity of recirculating
this slurry became apparent.

No Slurry Recirculation:  Effect of Flow Rate and  Amount of Limestone
Flow rates of 0.5 and 1.0 gpm using twice (2X)  and four times
the stoichiometric amount of limestone based on acidity for each rate
of flow were employed in experiments with the South Greensburg water.

No Slurry Recirculation:  Effect of Aeration and Sequence of Unit
Operations

Aeration was carried out in either or both tanks No. 1 and No. 2 and
either before or after addition of limestone.  In each of these experi-
ments , the amount of limestone used was twice the stoichiometric amount
based on the acidity of the coal mine water. The flow rate was 1.0 gpm
in treatment of the South Greensburg water.

Slurry Recirculation:  Effect of Flow Rate and  Aeration in Only
One Tank

In these experiments, slurry was recirculated as part of the treatment
process.  Slurry was added to either tank No. 1 or tank Wo. 2 at a
rate of 0.5 gpm and the raw mine water, the South Greensburg discharge,
treated at a rate of 0.5 gpm.  Total flow into  the settling tanks was
then 1.0 gpm.  Aeration was carried out in tank Wo. 2 only.

With the same conditions, this water was also treated at a flow rate
of raw water of 1.0 gpm and slurry recirculated at 1.0 gpm.  Total
flow into the settling tanks was then 2.0 gpm.

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Slurry Recirculation:  Effect of Flow Rate and Aeration in Two
Separate Tanks

Slurry was added to either tank No. 1 or No. 2 at a rate of 0.5
and the raw mine water, the South Greensburg discharge, treated at a
rate of 0.5 gpm for a total flow into the settling tanks of 1.0 gpm.
Aeration was carried out simultaneously in both tank No. 1 and tank
No. 2.

This same water was also treated using the same conditions except at
a flow rate of 1.0 gpm of raw mine water and 1.0 gpm of recirculated
slurry for a total flow of 2.0 gpm into the settling tanks.

Slurry Recirculation:  Effect of ^4-X the Stoichiometric Amount
of Limestone

In this series of experiments, the customary quantities of limestone
(twice the Stoichiometric amount based on acidity) were doubled and/or
the slurry from the experiments with this greater quantity of lime-
stone was recirculated.  The South Greensburg discharge was again the
water which was treated.

Slurry Recirculation:  Effect of Amount Eecirculated

Water from the South Greensburg discharge was treated with limestone
and raw mine water:slurry ratios of 1:1, 3:2, and 3:1.  In each
case, the total flow of the treated water entering the settling tanks
was held at 1.0 gpm.  Aeration was carried out in tank No. 2 only.

The same water was treated at a rate of 0.5 SPmj the quantities of
slurry recirculated were twice (l.O gpm) that of the raw mine water.
Total flow into the aeration tank was 1.5 gpm.  Aeration was carried
out in both tank No. 1 and tank No. 2.

Treatment of Thorn Run Water

For a cursory examination of treatment of a water containing iron princi-
pally in the ferric state, three experiments were conducted with Thorn
Run water.  In the first two, with flow rates of 1.0 and 2.0 gpm of
raw mine water respectively, no slurry was recirculated.  In the third
experiment, slurry was recirculated; raw mine water was treated at a
flow rate of 1.0 gpm and slurry recirculated at a flow rate of 1.0 gpm.
Total flow into the settling tanks was then 2.0 gpm.
                           Sludge Properties

Volume, settling behavior, and solids content of sludge from selected
batch experiments and continuous flow experiments were measured.
Aliquots of 1,000 ml of combination sludge-treated water were taken
                                  25

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at the end of a 5-hour batch experiment or at specified times during
continuous flow experiments.  The influence of the shape of the vessel
on properties of the sludge, specifically on solids content, was also
determined.

Sludge Volume and Settling Behavior

A well-mixed 1,000 ml sample of treated water containing sludge was
placed in an Imhoff cone.  Sludge volume was recorded at 5? 10, 15,
30, V?, and 60 minutes and 2k hours and was expressed as a percent
of the 1,000 ml at 2k hours.  A description of the settling "behavior
of the sludge was obtained by plotting the sludge volume with time.

Solids Content

From the Imhoff cone used in volume measurements, the water was
siphoned off to the level of the settled sludge by means of a filter
pump, Tygon tubing, and a Pasteur pipet.  All water was then removed
from the tubing and pipet, and about 2 ml of sludge was then drawn
into the pipet.  The sludge was placed into a preweighed beaker,
weighed wet, and dried to constant weight at 105 C.  Solids content
was expressed as percent solids by weight in the sludge.
                                 26

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                               SECTION VI

              RESULTS AND DISCUSSION OF LABORATORY STUDIES


                        Evaluation of Limestones

As part of the research program initiated at BCR to investigate the
limestone treatment of coal mine drainage (l), an attempt was made to
find which type of limestone would be most effective.  As a result
of that program, a method was established to evaluate the effective-
ness of individual limestones as neutralizing agents for coal mine
water.  The evaluation resulted in certain conclusions concerning
the limestones.  For example, to be effective the stone must have a
minimum particle size and relatively high calcium and low magnesium
content, indicating finely divided calcites and ruling out dolomites
and magnesites as neutralizing agents.  The importance of a high
surface area in some cases was also established.  Fourteen limestones
of varying origin, composition, and structure were used in that study.

These same 1^ limestones were also used in part of this program to
continue the evaluation of limestones as neutralizing agents for coal
mine water and, therefore, the following data from the past program,
Project CR-75, are included here to provide the necessary background
information.

The results of the analyses of the lU limestones by conventional
emission spectrographic techniques are listed in Table 1.  Structure
determinations of the limestones by X-ray diffraction analyses are
listed in Table 2.  Density, as determined with an air pycnometer,
and surface area, as determined either by a standard or modified BET
technique, of each of these stones are listed in Table 3.

These lU stones which had been received as fairly course material and
pulverized to the desired size were used in studies (a) to optimize
the particle size variable in limestone treatment, (b) to determine
any relationship between the tests with synthetic coal mine water and
the neutralization of an actual mine water, and (c) to attempt to
simplify the test which had been established to evaluate limestones.

Twelve additional limestones were evaluated according to the procedures
established in the above studies.  These were received in a finely
divided state, evaluated, pulverized further, and evaluated again.

Effect of Particle Size

Neutralization curves were prepared according to the general procedure
with ten particle size fractions of BCR limestone No. 1809 and synthetic
coal mine water.  A composite of these neutralization curves is illus-
trated in Figure 7.  The particle size in microns of each fraction is
                                    27

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ro
00
                             TABLE 1.  ANALYSES OF FOURTEEN LIMESTONES  SELECTED FOR  STUDY



                                             Spectrochemical Analyses,  Mineral Samples
BCR
Sample
No.
1462
1337
1461
1654
Reported as Percent
Loss on
Ignition
48.4
46.5
47.2
45.8
Si03
3.90
1.4o
1.05
2.05
A1303
1.24
0.3
0.3
0.54
Fe203
1.46
0.32
0.30
1.83
by Weigh
MgO
80.0
43.0
45.0
38.0
t of Ignr
CaO
11.5
55.0
53.0
5600
ted Sampl
TiOs
0.03
0.03
0.03
0.03
e (,900 c;
Na30 K20
0.02 <0.1
0.02 O.I
O.02 O.I
O.02 O.I

Mn03
0.03
0.03
0.03
0.03
1352
1364
1355
1362
2136
2135
1335
42.6
30.4
34.0
36ol
36.7
34.6
42.8
8.00
28.5
25.5
10.6
15.8
19.5
3.35
2.75
10.7
4.4o
2.17
4.4o
60lo
0.77
1.08
3.70
1.95
12.8
1.70
2c70
0.33
30.0
4020
1.80
3.80
2.80
2.4o
0.72
56.0
46.5
64.0
69.0
72.0
66.0
94.0
0.11
0.50
0.25
0.12
0.23
0.27
0.05
0.08
0.70
o.4o
0.03
0.36
0.33
0.02
0.87
2.25
0.91
0.20
0.62
Io50
0.1
<0003
0.07
0.03
0.37
0.03
o003
0,03
2145
1809
2177
41.7
42.1
42.7
5°00
406o
1.4l
1.69
1.50
0042
0.88
1.30
0.3
1.48
1.06
0.90
90.0
89 00
95.0
0.07
0.05
0.03
0.03
0.02
0.02
O.I
0.12
0.1
0.03
0.12
0.03

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    TABLE 2.  X-RAY ANALYSES OF FOURTEEN LIMESTONES
 BCR
Sample
 No.               _ Compounds Identified
                   MgCOg, CaMg(C03)2

1337               CaMg(C03)s

                   CaMg(C03)3

                   CaMg(C03)3, CaC03

1352               CaMg(C03)3, CaC03

136U               CaCOg, Si03, [6si03-Al303-9Mg0.7H20]

1355               CaC03, SiOs

1362               CaCXV, Si03, aB"eaOa, Ca(MgFe)(C03 )3

2136               CaC03, Si02

2135               CaC03, Si03

1335               CaC03

21^5               CaC03, Si03

1809               CaC03, Si03

2177               CaCOg
                              29

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TABLE 3-  DENSITY AND SURFACE AREA OF FOURTEEN LIMESTONES
BCR
Sample
No.
1462
1337
1461
165^
1352
1364
1355
1362
2136
2135
1335
21^5
1809
2177
Density,
D,
g/ml
3.27
2.74
2.9^
2.32
3.57
2.87
2.63
3.02
2.46
2.64
2.70
2.59
3.18
2.54
Surface
Area, SA,
a /
m3/g
1.98*
0.62*
1.11*
1.22*
2.29*
2.13*
2.94*
2.53*
5.39*, 5.13*
7.18*
0.88*
2.05*
1.76*, 1.72*
1.17*
                       *  Standard BET




                       *  Modified BET
                             30

-------
                       7-
                       6-
U)
H
                       5-
                       4-
                                         44-37
                                       (325x400)
                      KEY
                      74-44  = Microns

                      (200 x 325) = Mesh Size
                                                  74-44
                                                (200 x 325)
                                                        149-74
                                                       (100 x 200)
                                                (30x50)
                                           2380-1190
                                           (8x16)
         4760-2380
           (4x8)
                                                                                9510-4760
                                                                               (3/8"x 4M)
                                        60
~~l              r~
 120            180
   TIME,  minutes
                                                                                  T
               1
240           300

 Bituminous Coal Research, Inc., 2036G2R1
                        Figure  7. Effect of Particle Size of Limestone No. 1809 on Neutralization
                                            of Synthetic Coal Mine Water

-------
listed on the appropriate curve with the corresponding mesh size shown
in parentheses.  The two largest size fractions,  k,j6o to 9,510 microns
and 2,380 to U,76o microns, were relatively undisturbed by the mixing
action and remained on the bottom of the beaker throughout the test.
Size fractions between 7^ to 2,380 microns effected essentially the
same response—an initial increase of 2 to 3 pH units.  After about
90 minutes, the pH was slightly higher for the finer size fractions.
As indicated in Figure 7, the response from size fractions below
7^ microns was significantly different.  An immediate increase to
about pH 6 was observed followed by a further, less rapid increase to
approximately pH 8.  This series of experiments led to the choice of
the 37 to kk micron (325 x hoo mesh) fractions for all further experi-
ments with the iM- limestones.

Studies with Actual Coal Mine Water

Neutralization experiments were conducted according to the general
procedure with ik limestones and the South Greensburg discharge.  The
results are presented in Table 4.  The second column in this table
contains the relative weights of the papers which were cut to include
only the areas under the ik neutralization curves.  The weight of
blank papers is presented in the third column.  The size of the blanks
was arbitrarily chosen but was identical for a particular series of
tests.  The weights of the blanks indicated that the weights of equal
sizes of paper were essentially the same.

On the basis of the results as listed in Table k, on the visual observa-
tions of the lU neutralization curves, and on comparison of these curves
with the model curves in Figure 8, limestones Wo. 2135, 1335, 2136,
l8095 21^5j and 2177 were judged to be effective limestones to neutral-
ize this actual coal mine water.  Figure 8 shows the composite curves
resulting from the past evaluations of limestones with synthetic coal
mine water and has been presented before as Figure 12 on page ^7 of
Reference 1.  From the past studies, area A on this figure represents
the curves produced by effective limestones; areas B and C represent
those from ineffective limestones.

In Table 5, the limestones are listed in order of increasing effective-
ness based on these tests, with limestone No. 2177 being the most
effective.  The relative effectiveness of the lU limestones, as a result
of these tests with the South Greensburg water, is compared to the
relative effectiveness from tests conducted in the past with synthetic
coal mine water-  Relative areas under the neutralization curves with
the synthetic systems were obtained by integration.  The relative areas
with the South Greensburg coal mine water were obtained by the cut and
weigh method.  Agreement between results of the tests with synthetic
coal mine water and the results of the tests with the actual coal mine
water was good.  This is shown in Table 5 by the similarities in
relative effectiveness of each limestone in both tests.  Both the

-------
TABLE k.  EVALUATION OF LIMESTONES WITH SOUTH GREENSBURG
                  COAL MINE WATER
BCR
Sample
No.
1U62
1^1
1337
165^
1352
I36ii
1355
1362
2135
1335
2136
1809
211+5
2177
Relative Area
tinder Curve
16
19
25
26
36
I*
55
62
70
78
79
Qh
97
100
Weight of
Paper-blank,
gm
1.2686
1.2332
1.2677
1.2630
1.2777
1.2o77
1.2567
1.2561
1.2687
1.29011
1.2777
1.2572
1.2801
1.271+0
                                   Mean   1.2670
                           33

-------

pH
                                                                 KEY
                                                                 A =  Effective Limestones
                                                                 B and C = Ineffective  Limestones
                                          120           180

                                            TIME, minutes
240
300
                                                                       Bituminous Coal Research, Inc. 2036G35
                Figure 8. Model Curve for  Judging Effectiveness of Limestones I

-------
 TABLE 5.   RELATIVE EFFECTIVENESS OF LIMESTONES  WITH SYNTHETIC
             AND SOUTH GREENSBURG COAL MINE WATER

  Relative               Synthetic            South Greensburg
Effectiveness         Coal Mine Water              Water
lU 1^62
13 1337
12 iU6l
11 165^
10 1352
9 1364
8 1355
7 1362
6 2136
5 2135
4 1335
3 2lU5
2 1809
1 2177
1^62
lU6l
1337
165^
1352
1364
1355
1362
2135
1335
2136
1809
21^5
2177
                                35

-------
synthetic and the South Greensburg waters contained iron principally
in the ferrous state and, therefore, treatment of these waters involved
oxidation as well as neutralization with limestone.

Studies with Dilute Sulfuric Acid

As part of a study to simplify the test to evaluate limestones, dilute
sulfuric acid was used in place of the synthetic or actual coal mine
waters employed in earlier studies; the neutralization tests were con-
ducted according to the general procedure.  The results of experiments
with twice the stoichiometric amount of each of the l4 limestones are
presented in Table 6.  The relative areas under the neutralization
curves, as measured by the cut and weigh method, are presented in the
second column in this table.  The pH values at the times specified
were taken from the neutralization curves and are listed in the last
columns.  Comparison of the results in Table 6 with the results of
tests with l4 limestones and the South Greensburg water (Table ^)
shows smaller differences in the areas under the neutralization curves
when dilute sulfuric acid was used.

The results of neutralization experiments with the exact stoichiometric
amount of each of the ik limestones and dilute sulfuric acid are pre-
sented in Table 7.  Relative areas under the neutralization curves
were measured either by the cut and weigh method or with a planimeter
and are presented in the second column in this table.  The pH values
at the times specified are listed in the last columns.  Prom this
table, some of the limestones judged from past tests to be effective
neutralizing agents, for example No. 2135 and 2136, were among the
least effective stones.  With the exact stoichiometric amount of lime-
stone, the amount of impurities in the stones, specifically the
presence of inert Si03. is an important factor.  The stones which were
not effective (Table 7) contain significant quantities of SiOg, with
the exception of No. l462 which is principally a magnesite, MgCOg,
and for that reason was the least effective of the 1^-.

In only two cases, with limestones No. 1809 and 2177, did the pH reach
a value of 6 after 60 minutes as indicated by the data in Table 7-
Even with the effective limestones, after 300 minutes the pH value
was not much greater than 6.

A comparison of the relative effectiveness of the ik limestones from
tests with (a) synthetic coal mine water, (b) South Greensburg water,
(c) dilute sulfuric acid using twice the stoichiometric amount of
limestone, and (d) dilute sulfuric acid with the exact stoichiometric
requirement of limestone is presented in Table 8.  The limestones are
listed in order of increasing reactivity, the most reactive being
No. 2177.  In an columns but the last, limestones in positions 1
through 6 were the effective stones; those in positions 7 through lh
were not effective as neutralizing agents.
                                  36

-------
TABLE 6.  EVALUATION OF LIMESTONES WITH DILUTE SULFURIC  ACID
      AND TWICE THE STOICHIOMETRIC AMOUNT OF LIMESTONE
                Relative Area     	pH after
Sample No.
1U62
165U
lU6l
1337
1355
1352
1361+
1362
2136
2135
21^5
1335
1809
2177
under Curve
7
61
63
67
7^
76
77
87
90
91
92
93
99
100
30 min
3.2
5.1
5.0
5.^
5.1
6.U
6.0
6.8
7.0
7.0
7.3
7.2
7.1*
7.7
60 min
3.2
5.8
6.0
6.3
6.5
6.7
6.7
7.2
7.3
7.3
7.5
7.5
7.7
7.8
300 min
3.5
6.6
6.6
6.8
7.3
7.2
7.^
7.7
7.8
7.7
7.9
7.8
8.0
8,0
                             37

-------
TABLE 7.  EVALUATION OF LIMESTONE WITH DILUTE SULFURIC ACID
      AND THE EXACT STOICHIOMETRIC  AMOUNT OF LIMESTONE
     Relative Area
Spectrochemical
   Analysis
BCR
Sample
Number
11+62
1361+
1355
2135
2136
1362
1651+
11+61
1352
1337
1335
211+5
1809
2177
under Curve
Cut and
Weigh
ii
ll+
19
22
30
31
1+2
1+8
56
65
65
75
98
100
Planimeter
1+
11+
19
22
30
31
1+2
^9
57
61+
66
77
96
100
Percent of Ignited
(900 C) Sample
_SiOg
3-9
28.5
25-5
19.5
15.8
10.6
2.0
l.l
8.0
1.1+
3.^+
5.0
1+.6
1.1+
pH Attained
after
30 min 60 min
3.0
3.^
3-5
3-7
l+.O
3.8
3-5
3A
3.7
3-5
li s
ij. C
5.2
5.9
3.1
3.5
3.7
3.8
l+.l
l+.O
3.7
3.7
l+.l
l+.O
>+.7
5.2
6.2
6.3
300 min
3.2
3.5
3.7
3.8
l+.l
^.3
^.5
6.0
6.0
6.1+
5.8
6.3
7.0
6.9
                          38

-------
TABLE 8.  RELATIVE EFFECTIVENESS OF LIMESTONES WITH SYNTHETIC AND
 SOUTH GREENSBURG COAL MINE WATERS AND WITH DILUTE SULFURIC ACID
Relative
Effectiveness
13
12
11
10
9
8
7
6
5
1+
3
2
1
Synthetic Coal
Mine Water*
ll+62
1337
1U61
1651+
1352
136*+
1355
1362
2136
2135
1335
21^5
1809
2177
South
Greensburg
Water*
LU62
11+61
1337
165^
1352
1361+
1355
1362
2135
1335
2136
1809
21U5
2177
Dilute
Sulfuric
Acid*
165^
11+61
1337
1355
1352
136^
1362
2136
2135
211+5
1335
1809
2177
Dilute
Sulfuric
Acid*
1361+
1355
2135
2136
1362
165>+
1U61
1352
1337
1335
211+5
1809
2177
            *  Twice the stoichiometric amount of limestone employed.

            4=  The exact stoichiometric amount of limestone employed.
                                  39

-------
With the exact stoichiometric amount of limestone and dilute sulfuric  -
acid  the differences in reactivity of the l4 limestones were amplified
compared to the other tests,  but the effect of the presence of inert
materials in the stones was such that there was poor agreement with the
results of the other tests.  There was better agreement between the
results with the synthetic and South Greensburg waters than with dxlute
sulfuric acid (2X) and the South Greensburg water.  The test had been
simplified by the use of dilute sulfuric acid, but the results seemed
less meaningful in relation to the neutralization of coal mine water.
Therefore, no further tests were made with dilute sulfuric acid as the
test water.

Both the cut and weigh method and the planimeter were used to obtain
the data in Table 7 on relative areas under the neutralization curves.
One study  (9) reports the relative standard deviation for obtaining
the area under a curve using a planimeter as 4.06 percent compared to
1.74 percent by the cut and weigh method, the latter being the more
precise.   The same study, though, reports the time required for the
planimeter method to be half that of the cut and weigh method.  The
planimeter was used for all measurements given hereafter in this
report.

Recommended Test Method

With the data available, the following test is recommended to evaluate
limestones as potential neutralizing agents for coal mine water:

Finely  divided  (37 to kk microns, 325 x 400 mesh) limestone should be
added and  air introduced to a solution of synthetic coal mine water at
pH 3.0,  containing from 200 to 250 mg/1 of Fe2+ added as ferrous sulfate;
this solution should be stirred and aerated continuously for a 5-hour
period  and the changes in pH recorded with time.  The amount of lime-
stone added should be twice the stoichiometric amount based on the
acidity of the synthetic coal mine water and based on the assumption
that the stone consists of pure CaC03 .  Air should be bubbled into the
solution through a gas diffuser at the bottom of the container.  The
aeration should be maintained throughout the reaction at a rate of
2,500 ml/min.

A composite curve including results from all past tests should be used
to judge the results of this test.  Such a curve  is presented in
Figure  9-  The curve from an effective limestone would be located in
area A  of  Figure 9; curves from ineffective limestones would be located
in areas B or C.  Finally, the test should be repeated with the coal mine
water to be treated and with the  selected limestone.

Evaluation of Finely Divided Limestones

Twelve  samples of finely divided  limestones were  procured for use on
this project and are listed in Table  9.  These were requested from the

-------
i5f
                   PH
                               8-
                               7-
                               6-
5-
                               4-
                                                60
                           120
                                           KEY
                                           A =  Effective Limestones
                                           B and  C = Ineffective Limestones
180
240
                                                                                           300
                                                          TIME, minutes
                                                                                    Bituminous Coal Research., Inc. 2036G17
                            Figure  9. Model Curve for  Judging  Effectiveness  of Limestones

-------
                                  TABLE 9.   ANALYSES  OF TWELVE FINELY  DIVIDED LIMESTONES
                                            Spectrochemical Analyses, Mineral Samples
                                                 Reported as Percent ty Weight
                                                    of Ignited Sample (900 C)
-P-
ro
 BCR
Sample
Number

2501
2501-P
2502
2502-P

2503
2503-P
250*1
25Ql*-P

2522
2522-P
2523
2523-P

251*1*
251A-P
251*5
251*5 -p
          25V7B
          25l*7B-P

          2576
          2576-P
          2577
          2577-P
   Source

South Dakota
South Dakota
South Dakota
South Dakota

South Dakota
South Dakota
Ohio
Ohio

Pennsylvania
Pennsylvania
Pennsylvania
Pennsylvania

New York
New York
West Virginia
West Virginia

Michigan
Michigan
Michigan
Michigan

Pennsylvania
Pennsylvania
Kentucky
Kentucky


CaO
93
93
90
90
90
90
55
53
87
85
81*
86
96
95
97
96
95

93
91
1*1
10*
93
88


MgO
0.61*
0.72
1.12
1.15
0.88
0.9!*
1*2.0
1*3.0
0.91
1.16
9.80
7.80
1.1*5
1.55
0.58
0.75
1.00
1.80
1.28
2.55
21*. 5
23.0
2.68
1*.35


SiOa
1*.15
3.85
5.80
6.00
6.20
6.05
2.10
2.1*0
7.30
7.30
3.30
3.00
1.1*0
1.20
1.15
1.15
1.53
1.95
3.30
3.30
23.0
20.0
2.73
i*.oo


AlaOa
1.12
1.17
1.50
1.53
1.57
1.70
0.1*1
0.1*8
2.15
2.55
1.35
1.13
0.20
0.23
0.33
0.35
0.59
0.6l
1.27
0.99
2.15
1.90
0.51
0.69


FeaOa
0.1*6
0.33
0.55
0.53
0.59
0.62
0.28
0.2l*
1.32
1.35
0.1*8
0.37
0.37
0.28
0.16
0.21
0.1*1*
0.51*
0.60
0.59
6.80
6.20
0.1*3
0.93

Loss On
Ignition
1*2.3
1*2.2
1*1.5
1*1.1*
1*1.3
!*1.3
1*6.5
1*6.1
1*0.1*
1*0.5
1*3.2
1*3.1
1^3 5
l*3A
1*3.2
1*2.9
1*3.2
1*3.0
1*2.9
1*2.6
35.0

i*a!8
1*1.6
X-ray Analyses

Compounds Identified

CaCCfe; SiOa

CaC03; Si02

CaC03; SiOa

CaMg(C03 )a

CaC03; SiOa

CaCCi,; CaMg(COa)8

CaCOg

CaC03

CaC03

CaCOg

CaC03; SiOa; CaMg(COg)a; Ca(OH)a

CaC03; SiOa; CaMg(C03)a

-------
companies supplying the limestones for the studies under Pennsylvania
Coal Research Board Project CR-75.  Of the 12, two were dolomitic
limestones; the remainder were high calcium limestones.

The finely divided limestones were first tested and analyzed for
particle size and chemical composition as received.  In addition,
each one was passed once through a pulverizing mill; in Table 9 the
pulverized samples are indicated by the suffix "P."  Tests and analyses
were repeated with crystalline structure by X-ray diffraction also
being determined on the pulverized materials.  The chemical composition
and crystalline structure are included in Table 9-

The complete particle size analyses for each of the limestones as
received are listed in Table 10; those for the stones pulverized once
are in Table 11.  The mesh size listed on the containers in which the
limestones were received was the determining factor in choosing the
size of screens used in these analyses.

Screen analyses for as-received and pulverized stones are listed in
Table 12.  Specifications for rock dust require that 70 percent of
the material pass through a 200 mesh screen.  Only 7 of the 12 lime-
stones, as received, met this standard.  After pulverizing once (desig-
nated "P"), all met this standard.

The percent moisture of each limestone as received and dried to con-
stant weight at 105 C is listed in Table 13.  The amount of moisture
was not judged to be significant.

Neutralization curves were prepared for batch experiments by testing
each limestone, both as received and after pulverizing once, with
synthetic coal mine water and two actual coal mine waters, the South
Greensburg and Thorn Run discharges.  During these experiments, the
synthetic coal mine water contained from 196 to 252 mg/1 of ferrous
iron, Fe3+, from U8l to ^97 mg/1 of acidity as CaCOg equivalents, and
had a pH of 2.9 to 3-0.  The South Greensburg discharge contained from
69 to 98 mg/1 of ferrous iron, from 1^0 to 199 mg/1 of acidity as
CaC03 equivalents, and had a pH of U.9 to 6.1.  The Thorn Run discharge
contained from 10 to 23 mg/1 of ferrous iron, from 8^5 to 1,0^3 mg/1
of acidity as CaC03 equivalents, and had a pH of 2.6 to 2.8.

Data from the neutralization curves are listed in the following tables:
limestone Wo. 2501 and 2501-P, Table l4; limestone No. 2502 and 2502-P,
Table 15; limestone No. 2503 and 2503-P, Table l6; limestone No. 250U
and 25QJ+-P, Table 17; limestone No. 2522 and 2522-P, Table 18; lime-
stone No. 2523 and 2523-P, Table 19; limestone Wo. 25^4- and 25^4-P,
Table 20; limestone Wo. 25^5 and 25%-P, Table 21; limestone Wo.

-------
          TABLE 10.   PARTICLE  SIZE ANALYSES OF  TWELVE FINELY DIVIDED  LIMESTONES  "AS RECEIVED"
Tyler
Mesh
        No. 2501
                 II
              III
              IV
                            No. 2502
I
26.2
11.1
2.2
2.0
8.3
II
52.6
22.3
4.4
4.0
16.7
III
52.6
74.9
79-3
83.3
100.0
IV
47.4
25.1
20.7
16.7
--
                                           100.0
                                                        No.  2303
                                                                       II
      III
                                                                     IV
                            No. 2504
'I
0.0
0.3
5.3
11.5
32.8
II
0.0
0.6
10.6
23.0
65.7
ill
0.0
0.6
11.2
34.2
99.9
IV
100.0
99.4
88.8
65.8
--
Tyler
Mesh
Tyler
Mesh
No. 2522
                 II
              III
No. 2547A
                II
             III
              IV
 0.0    0.0    0.0  100.0
14.2   28.5   28.5   71.5
 7.0   14.0   42.5   57.5
 3-9    7.8   50.3   49.7
24.7   49.6   99.9    —
             rv
          0.1   0.2    0.2   99.8
          0.1   0.2    0.4   99.6
          0.4   0.8    1.2   98.8
          1.2   2.4    3.6   96.4
         47.8   96.4  100.0    —
               100.0
      I = Weight on sieves, grams
                            No. 2523
I
0.0
1.6
10.1
9.2
29.1
50.0
I
38.1
5.9
1.1
1.1
n
0.0
3.2
20.2
18.4
58.2
100.0
No.
II
76.6
11.9
2.2
2.2
7.0
_99.9
III
0.0
3.2
23.4
4i.8
100.0
25472
ill
76.6
88.5
90.7
92.9
99.9
IV
100.0
96.8
76.6
58.2

IV
23.4
11.5
9-3
7.1
—
No. 2544
                                                                       II
                                                              III
                                                               No. 2576
              IV
                                                                 0.0    0.0    0.0  100.0
                                                                 1.9    3.8    3.8   96.2
                                                                 4.9    9.8   13.6   86.4
                                                                 5.9   11.8   25.4   74.6
                                                                 37-1   74.5   99-9    --
I
0.0
9.5
13.5
13.2
14.8
51.0
II
0.0
18.6
26.5
25-9
29.0
100.0
III
0.0
18.6
45.1
71.0
100.0
—
IV
100.0
81.4
54.9
29.0
-_
—
                                       III =  Total percentage  on each sieve
                                                                                           No.2545
I
0.1
4.2
10.3
8.5
26.7
II
0.2
8.4
20.7
17.1
53.6
III
0.2
8.6
29.3
46.4
100.0
IV
99.8
91.4
70.7
53.6

                                                                                                  100.0
                                                                                    No. 2577
     II =  Percent by weight on sieves
                                        IV =  Total percentage passing each sieve

-------
    TABLE 11.  PARTICLE SIZE  ANALYSES OF TWELVE FINELY DIVIDED  LIMESTONES  (AFTER PULVERIZING)
Tyler
Mesh
20
100
200
400
Pan
Total
0.0
0.4
3.1
8.7
37.7
49.9
0.0
0.8
6.2
17.4
75.6
100.0
0.0
0.8
7.0
24.4
100.0
—
100.0
99-2
93.0
75.6

—
0.0
0.4
2.9
6.6
40.2
50.1
0.0
0.8
5.8
13.2
80.2
100.0
0.0
0.8
6.6
19.8
100.0
~
100.0
99-2
93.4
80.2
—
—
0.0
0.1
0.7
3.9
45.2
49.9
0.0
0.2
1.4
7.8
90.6
100.0
0.0
0.2
1.6
9.4
100.0
—
100.0
99.8
98.4
90.6
—
—
0.0
0.0
1.1
8.0
40.6
49/7
0.0
0.0
2.2
16.1
81.7
100.0
0.0
0.0
2.2
18.3
100.0
—
100.0
100.0
97.8
81.7
—
—
 Tyler
 Mesh
 Tyler
 Mesh
No. 2501-P
0.0
0.4
3.1
8.7
37.7
0.0
0.8
6.2
17.4
75.6
III
0.0
0.8
7.0
24.4
100.0
IV
100.0
99-2
93.0
75.6
49.9 100.0
No. 2522 -p
I
0.0
0.4
1.5
3.7
44.1
I
0.0
0.1
0.7
47 .'6
5978"
II
0.0
0.8
3.0
88 .'7
99.9
No. 25
II
0.0
0.2
1.4
2.8
95.6
100.0
III
0.0
0.8
3.8
11.2
99-9
47-A-P
III
0.0
0.2
1.6
4.4
100.0
—
IV
100.0
99.2
96.2
88.8

IV
100.0
99-8
98.4
95.6
--
 No.  2502-P
No. 2503-P
                                     0.0    0.0    0.0  100.0
                                     0.1    0.2    0.2   99.8
                                     2.5    5.0    5.2   94.8
                                     8.0   16.1   21.3   78.7
                                    3_9J12   78.7  loo.o    —
                                          100.0
No. 2547-B-P
I
0.0
0.3
2.4
6.8
40,1
II
0.0
0.6
4.8
13-7
80.8
III
0.0
0.6
5.4
19.1
99-9
IV
100.0
99.4
94.6
80.9
--
       I  = Weight on sieves,  grams

      II  = Percent by weight  on sieves
I
0.0
0.1
0.7
3.9
45.2
^2
II
0.0
0.2
1.4
7.8
90.6
100.0
III
0.0
0.2
1.6
9-4
100.0
— ~
IV
100.0
99.8
98.4
90.6
—
—~
No. 2544-P
I
0.0
0.0
0.6
4.o
45.1
49V7
II
0.0
0.0
1.2
8.0
90.7
99-9
III
0.0
0.0
1.2
9.2
99-9

IV
100.0
100.0
98.8
90.8
--

No. 2576-P
I
0.0
0.2
3.7
10.4
35.5
4g. 8
II
0.0
0.4
7.4
20.9
71.3
100.0
III
0.0
0.4
7.8
28.7
100.0
--
IV
100.0
99-6
92.2
71.3
—
--
No. 25Q4-P
      III =  Total percentage on each sieve

       IV =  Total percentage passing each sieve
                                                                                            0.0    0.0    0.0  100.0
                                                                                            0.0    0.0    0.0  100.0
                                                                                            1.1    2.2    2.2   97.8
                                                                                            3.7    7-6    9.8   90.2
                                                                                           44.2   90.2  100.0    --
                                                                                            ?.0  100.0

-------
TABLE 12.  PARTICLE SIZE ANALYSES OF TWELVE
 FINELY DIVIDED LIMESTONES AS EECEIVED AND
   PULVERIZED - PERCENT PASSING 200 MESH
BCR
Sample
Number
2501
2502
2503
2504
2522
2523
25^4
25^5
25^?A
2547B
2576
2577
Percent
Passing
200 Mesh
k.6
20.7
92.2
88.8
57.5
76.6
86.4
70.7
98.8
9.3
54.9
78.9
BCR
Sample
Number
2501- P
2502-P
2503 -P
2504-P
2522-P
2523-P
2544-P
2545-P
25^7A-P
2547B-P
2576-P
2577-P
Percent
Passing
200 Mesh
93.0
93.^
98.1+
97.8
96.2
9^.8
98.8
97.6
98.4
9^.6
92.2
97.8

-------
TABLE 13-  MOISTURE CONTENT OF TWELVE
      FINELY DIVIDED LIMESTONES
BCR
Sample
No.
2501
2502
2503
250U
2522
2523
25Mt
25^5
25^?A
25^73
2576
2577
Moisture (105 C)
Percent
0.23
o.ok
0.42
O.l6
0.07
0.1+5
0.27
0.00
oM
0.07
0.03
0.13

-------
               TABLE  Ik.  NEUTRALIZATION DATA FOR  LIMESTONE
                           NO.  2501 AND 2501-P
                     Synthetic        South Greensburg       Thorn Run
                   2501     2501-P    2501      2501-P     2501     2501-F

 Experiment No.     396-31    396-71    396-50    396-93     396-47   396-83
    0 min
   15
   30
   45
   60

  120
  180
  240
  300
   2k hr
    0 min
   15
   30
   45
   60

 120
 180
 240
 300
225
225
221
213
211
192
193
180
177
114
243
183
106
69
47
6
6
6
6
1
75
72
69
72
67
•65
65
64
47
4l
92
86
82
76
63
39
22
14
11
2
17
22
21
21
21
21
21
— —
— —
17
15
15
15
15
14
13
11
11
7
1
3.0
4.8
5.4
5.4
5.3
5.2
5.1
5.0
5.0
3-0
6.0
6.0
5.9
5.8
7.2
7-7
7.8
7.9
5.5
6.2
6.0
5.9
5.8
5.6
5.4
5.4
5.3
5.0
6.5
6.5
6.5
6.5
6.5
6.5
6.5
6.7
2.8
3.4
3.8
4.3
4.4
4.4
4.4
4.5
4.6
2.8
5.5
6.1
6.3
6.5
7.1
7.4
7.5
7.6
Initial Acidity,
   ^g/1            497      487       141      195       9^0      845
Final Acidity,
   mg/1 (24 hr)    273      -13       117       -1       107       -Ij.
                                  48

-------
             TABLE 15.  NEUTRALIZATION DATA FOR LIMESTONE
                        NO. 2502 AND 2502-P

                    Synthetic        South Greensburg      Thorn Run
                  2502     2502-P    2502     2502-P    2502     2502-P

Experiment No.    396-34   396-72    396-48   396-58    396-94   396-84

 Fea+,mg/l

   0 min
  15
  30
  45
  60

 120
 180
 240
 300
  2k hr
231
211
207
206
199
182
177
176
173
133
24l
177
106
70
48
6
5
5
5
1
74
69
71
66
63
64
61
61
46
40
91
75
67
55
32
7
7
3
3
3
17
21
18
19
17
11
11
12
8
1
14
15
15
15
14
14
13
11
7
3
3.0
5.5
5.4
5.4
5.4
5.3
5.2
5.2
5.1
3-0
5.9
5.8
5.8
5.8
7.3
7.7
7.8
7.8
5.8
6.4
6.2
6.1
6.0
5.7
5.6
5.4
5.4
5.0
6.4
6.4
6.4
6.4
7.0
7.6
7.7
7.7
2.8
3.2
3.3
3.4
3.6
4.0
4.1
4.2
4.2
2.8
5.4
6.0
6.3
6.5
7.0
7.3
7-4
7.5
   0 min
  15
  30
  45
  60

 120
 180
 240
 300

Initial Acidity,
  mg/1             497      48?       154      195      1005      845
Final Acidity.
  mg/1 (24 hr)     264      -18       103       -9       110        4
                                   49

-------
              TABLE  16.  NEUTRALIZATION DATA FOR LIMESTONE
                         NO.  2503 AND 2503-P

                     Synthetic        South Greensburg       Thorn Run
                  2503      2503-P    2^03     2503-P     2503     2503-P

 Experiment No.    396-36    396-73    396-49   396-95     396-57  396-85

  Fe3 + ,  mg/1

    0 min
   15
   30
   45
   60

  120
  180
  240
  300
   2k hr
   0 min
   15
   30
   45
   60

 120
 180
 240
 300
227
151
101
72
15
6
5
5
5
1
242
133
67
13
10
9
6
6
9
l
69
57
50
41
21
10
8
6
3
1
95
87
8l
72
67
37
10
9
9
1
19
19
24
22
23
23
22
23
16
2
14
Ik
16
14
13
13
12
9
9
2
3.0
6.0
5.9
5.9
5-9
7.6
7.8
7.9
7.9
3.0
6.0
6.0
6.2
7.3
7.8
7.9
7.9
8.0
6.1
6.4
6.3
6.3
6.3
6.5
7.2
7.6
7.7
5*0
6.6
6.6
6.6
6.6
6.4
6.5
6.8
7.2
2.8
3.2
3-3
3.4
3.6
4.0
4.1
4.2,
4.2
2.8
6.0
6.4
6.6
6.9
7.4
7.6
7.7
7^7
Initial Acidity,
  Wl             497      487       154      198      1005     880
Final Acidity.
  mg/1 (24 hr)     -25      -19        -7       .5       359       0
                                  50

-------
             TABLE I?.  NEUTRALIZATION DATA FOR LIMESTONE
                        NO. 2504 AND 2504-P

                    Synthetic        South Greensburg      Thorn Run
                  25042504-P    2504     2504-P    25042504-P

Experiment No.    396-38   396-7^    396-51   396-96    396-62   396-87

 Fe2+, mg/1

   0 min
  15
  30
  45
  60

 120
 180
 240
 300
  24 hr
218
212
212
212
207
207
220
204
201
102
242
236
228
224
221
213
207
199
149
110
71
70
73
67
52
54
52
5^
51
49
97
91
90
87
87
90
90
96
57
52
19
17
18
18
19
21
19
19
15
3
15
17
19
19
18
17
17
14
15
l
2.9
3.6
3.8
3-9
5.0
5.3
5.3
5-3
5-3
3.0
4.8
5.3
5.3
5.3
5.3
5-3
5.3
5.3
5.6
6.3
6.1
5.8
5.8
5.6
5.5
5.^
5.^
5.0
5.5
5.6
5.6
5.5
5.^
5.3
5.3
5.2
2.8
3.0
3.1
3.1
3-1
3-7
4.2
4.3
4.5
2.8
3.2
3-2
3.2
3-3
4.3
4.4
4.5
4.5
   0 min
  15
  30
  45
  60

 120
 180
 240
 300

Initial Acidity,
  mg/1             497      487       140      198      1043      880
Final Acidity.
  mg/1 (2k hr)     245      200       112      152        49       54
                                   51

-------
              TABLE 18.  NEUTRALIZATION DATA FOR  LIMESTONE
                         NO.  2522 AND 2522-P

                      Synthetic       South Greensburg       Thorn Rim
                   2522      2522-P    2522      2522-P     2522     2522-P

 Experiment Wo.     396-40    396-75    396-52    396-97     396-63    396-87

  Fes+,  mg/1

    0 min
   15
   30
   45
   60

  120
  180
  240
  300
   24 hr
   0 min
   15
   30
   45
   60

 120
 180
 240
 300
218
156
123
101
87
60
48
39
33
12
236
130
52
13
11
11
10
8
7
1
72
69
60
60
42
31
25
18
11
l
92
88
77
68
60
23
12
10
7
1
Ik
21
21
21
21
17
9
9
9
1
13
20
17
18
17
15
12
11
15
2
2.9
6.0
5.8
5.6
5.6
5.4
5.3
5-3
5.3
3.0
6.0
6.0
6.4
7-5
7.8
7.9
7-9
8.0
5-3
6.4
6.4
6.3
6.3
6.2
6.2
6.1
6.1
k.9
6.6
6.6
6.6
6.6
6.6
6.7
7.2
7.5
2.8
4.8
5o2
5.5
5.7
6.0
6.2
6.5
6.7
2.8
6.2
6.5
6.8
7.0
7.4
7.6
7.6
7.7
Initial Acidity,
  mg/1             497      487       140      191      1043      912
Final Acidity.                                             J      y
  mg/1 (2k hr)      22      -26       109        8        12       -9
                                 52

-------
               TABLE 19.  NEUTRALIZATION DATA FOR LIMESTONE
                          NO. 2523 AND 2523-P

                     Synthetic       South Greensburg      Thorn Run
                  2523     2523-P    2523     2523-P    2523     2^23-P

Experiment No.    396-39   396-76    396-53   396-98    396-6^   396-88

 Fe3+, mg/1

   0 min
  15
  30
  ^5
  60

 120
 180
 2^0
 300
  2k bx
   0 min
  15
  30
  k5
  60

 120
 180
196
lJ+9
87
68
57
23
13
11
11
1
23^
132
52
32
23
12
11
8
8
1
73
65
56
55
37
28
23
17
11
1
91
80
7^
60
25
22
13
5
6
1
13
Ik
Ik
15
12
11
6
6
6
l
13
18
17
17
15
12
11
7
7
3
2o9
6.0
5-9
5.8
5-7
5.7
6.5
7A
7.6
3-0
5.9
5.8
5.8
5.9
7.3
7.6
7.8
7.8
5-3
6.6
6.6
6.5
6.5
6.k
6.3
6.3
6.3
k.9
6.k
6.k
6.k
6.k
6,3
6.k
6,5
6.7
2.8
^.9
5.^
5.7
5.9
6.3
6o5
6.8
7.1
2.8
5.8
6.2
6.k
6.5
7.0
7.3
7-5
7.6
 300

Initial Acidity,
  mg/1             k<$7      ^87       ikO      191      10^3      912
Final Acidity.
  mg/1 (2k hr)     ^87      -15       107        0        11      -10
                                    53

-------
              TABLE 20.   NEUTRALIZATION DATA FOR LIMESTONE
                          NO.  2544 AND 2544-P

                      Synthetic        South Greensburg      Thorn Run
                   p^Ij.!^      pslili—p    p^jlili     2544—P    2544     2544—P

 Experiment  No.     396-41   396-77    396-54   4o6-l     396-65   396-89

  Fe3+, mg/1

    0 min            223      233         71        92        13       22
   15                154      155         67        82        16       23
   30                87        84         65        78        13       21
   45                21        13         58        71        10       16
   60                13        10         31        65         6       16

  120                  6        7         25        60         6       12
  180                  5        7         11        13         59
  240                  5        7          6         5         5        7
  300                  575857
   24 hr               11          1         5         22
   0 mi*           2.9      3.0       5.1        5.0       2.8      2.8
  !5               6.0      6.0       6.4        6.6       5.9      6.0
  30           .    5.9      6.0       6.4        6.6       6.4      6.3
  45               5.9      6.1       6.4        6.6       6.6      6.5
  60               6.2      7.4       6.4        6.5       6.8      6.5

 120               7.8      7.8       6.4        6.5       7.4      7.2
 !8o               7.9      7.9       6.4        6.6       7.6      7.1*
 2^°               8.0      7.9       6.6        6.9       7.6      7.6
 300               8.0      8.0       6.8        7.4       7.7      7.g

Initial Acidity,
  "g/l             497      487       153        199      1043      889
Final Acidity.
  mg/1 (24 hr)     -12      -12         7        _i6        _i       _^
                                  54

-------
             TABLE 21.  NEUTRALIZATION DATA FOR LIMESTONE
                          NO. 2545 AND 2545-P

                     Synthetic       So. Greensburg     Thorn Run
                    25452545-p     25452545-p    25452545-p
Experiment No.     396-42  396-78    396-55  4o6-2    396-66  396-90

  Fea+, mg/1
0 min
15
30
45
60
120
180
24-0
300
24 hr
pH
0 min
15
30
45
60
120
180
24-0
300
Initial Acidity,
mg/1
Final Acidity.
mg/1 (24 hr)
21?
128
73
34
16
6
6
6
5
1
2.9
6.0
5.8
5.8
5.8
7.2
7.6
7.7
7.8
497
_2
230
83
13
13
11
10
8
7
7
1
3.0
6.1
7.7
7.8
7.8
7.8
7.8
7»8
7.8
k&7
-21
70
59
U7
Uo
17
12
6
6
6
1
5.1
6.U
6.1*
6.4
6.U
6.1*
6.4
6o7
7.0
153
6
96
77
68
52
^3
7
6
5
6
3
5.0
6.6
6.6
6.6
6.6
7.1
7.6
7.7
7.7
199
-11
13
13
12
8
8
7
1+
3
1*
l
2.8
5.8
6.1
6.3
6.1*
6.8
7.2
7.4
7.5
1001*
3
23
21
17
17
17
16
11
7
8
5
2.8
6.5
6.8
7.1
7.3
7.5
7.6
7.6
7.7
889
_j_
                                   55

-------
                  TABLE 22.   NEUTRALIZATION DATA FOE
                    LIMESTONE NO.  25^4-?A AND 2547A-P
                         Synthetic
 Experiment  No.

   Fe3+, mg/1

       0 min
      15
      30

      60
    120
    180
    240
    300
      24 hr
     PH
396-44   396-81   396-60   406-3
      0 min
     15
     30
     ^5
     60
    120
    180
    240
    300
Initial Acidity,
  mg/1
Final Acidity,
  mg/1
 219
  97
  11
  11
   7
   8
   8
   8
   7
   1
 3.0
 6.1
 6.6
 7.9
 8.1
 8.1
 8.1
 8.1
 8.1
495

  2
233
127
 11
 11
  9
  8
  9
  9
  9
  3
3.0
6.1
6.5
7.8
7.9
8.0
8.0
8.0
8.1
         481

         -30
                    76
                    69
                    59
                    47
                     8
                     4
                     8
                     4
                     4
                     l
                  5.0
                  6.5
                  6.6
                  6.6
                  6.7
                  7.7
                  1-7 Q
                  7.0
                  1-7 O
                  7.8
                  7-9
         153

          -7
•eensburg Thorn Run
2547A-P 2?47A 254-7A-P
406-3
87
79
63
59
48
7
5
4
4
1

6.' 8
6.8
6.7
6.7
7.4
7.8
7.9
8.0
197
-16
396-67
15
9
6
7
8
5
5
5
5
1
2.8
6.9
7.3
7.5
7.5
7-7
7-7
7-7
7.7
1004
7
396-91
23
21
17
15
13
12
9
9
9
l
2.7
6.6
7.0
7.2
7.3
7.5
7.6
7.6
7.6
1009
-9
                                 56

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                   TABLE 23.  NEUTRALIZATION DATA FOR
                     LIMESTONE NO. 2547B AND 2547B-P
                      Synthetic
Experiment No.

 Fe3+. mg/l

   0 min
  15
  30
  45
  60

 120
 180
 240
 300
  2k hr
 2547B

396-68
2547B-P

396-82
South Greensburg
 2547B2547B-. F

396-61   406-4
                                          Thorn Run
 2547B

396-69
2547B-P

396-92
24l
235
231
233
235
235
237
243
182
173
235
129
56
14
14
10
11
11
18
3
74
73
72
74
73
76
62
59
59
57
85
77
65
62
57
20
7
3
3
l
16
16
16
16
17
17
17
17
17
6
23
26
26
25
17
13
11
10
9
2
   0 min
  15
  30
  ^5
  60

 120
 180
 2^0
 300

Initial Acidity,
  mg/l
Final Acidity
  mg/l (2k hr)
3.0
3.6
3-9
4.1
4.2
4.8
4.8
4.7
4.6
3-0
5.9
5.9
6.0
7.2
7.8
7.9
7.9
7.9
5.0
5.3
5.3
5.4
5.^
5.4
5-3
5.2
5.2
4.9
6.5
6.5
6.5
6.5
6.4
6.6
7.0
7.3
2.7
3.1
3.1
3-3
3-^
4.2
4.2
4.2
^•3
2.7
6.0
6.3
6.5
6.6
7.2
7.4
7.5
7.5
495
421
481
-15
153
145
199
-9
988
310
1009
-11
                                   57

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            TABLE 2k.   NEUTRALIZATION DATA FOR LIMESTONE
                         NOo  2576 AND 2576-P
                    Synthetic

Experiment No.
Fe2+, mg/1
0 min
15
30
45
60
120
180
240
300
2k hr
PH
0 min
15
30
45
60
120
180
240
300
2576
406-15

255
247
21+7
2^9
2^8
2^7
2kk
2k5
238
177

3»0
k.O
k.3
k.9
5c2
5o2
5.2
5»2
5.2
2576-P
1+06-17

2l+8
2l+7
2l+3
237
237
232
215
196
188
110

3.0
5»5
5.0
5.5
5.H
5.4
5.3
5.2
5.2
So. Greensburg
Thorn Run
2576
4o6-27
89
88
90
85
87
81
88
89
90
77
5.0
5.2
5o2
5.2
5.2
5.2
5.2
5o2
5.1
2576-P
406-28
95
95
9^
95
91
89
87
86
85
68
5.0
6.0
6.0
6.0
5.9
5.6
5.5
5«4
5.3
2576
406-33
10
17
18
19
21
23
1+0
41
46
3
2.6
2.6
2.8
2,8
2o9
3.0
3.0
3.1
3.2
2576-P
406-30
10
27
23
21
22
18
18
12
8
3
2.7
3.0
3.0
3.1
3.2
4.0
4.3
4.3
4.4
Initial Acidity,
  mg/1             484     1+84       182

Final Acidity.
  mg/1 (2k hr)     315     216       180
          181+
          150
998


354
889
                                                               300
                                 58

-------
             TABLE 25.  NEUTRALIZATION DATA FOR LIMESTONE
                           NO.  2577 AND 2577-P
                      Synthetic
Experiment No.
 Fes+, mg/1
      0 min
     15
     30
     ^5
     60
    120
    180
    2l+0
    300
     2l+ hr

     PH
      0 min
     15
     30
     1+5
     60
    120
    180
    2l+0
    300
2577
1+06-16
252
88
60
32
23
17
15
13
13
l
3.0
6.0
5o8
5.8
6.0
7-1+
7.6
7.7
7.8
2577-P
1+06-18
2l+8
123
57
23
20
13
12
11
1
1
3.0
6.0
6.0
7.1
7.8
7.8
7.8
7.8
7.8
So, Greensburg
                 Thorn Run
2577
1+06-26
88
77
66
60
^
13
6
8
6
1
5.0
6.5
6.5
6.5
6.1+
6.5
6.6
6.8
7.3
2577-P
1+06-29
98
82
70
56
1+5
20
17
16
ll+
1
5.0
6.U
6.U
6.1+
6,1+
6.6
7.2
7^
7,5
2577
1+06-3!+
10
11
12
n
10
6
27
23
21+
1
2.6
5.3
5.6
5.7
5.8
6.2
6.5
6.6
6.8
2577-P
1+06-31
10
12
12
11
10
8
7
7
7
2
2.7
5o9
6.2
60i+
6.6
7.0
7.2
7ol+
7.U
Initial Acidity,
  mg/1
Final Acidity.
  mg/1 (2l+ hr)
1+8U
-16
182
 -3
          181+
            0
                                                         998

                                                           1+
889
                                    59

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and 25^7A-P, Table 22; limestone No.  25^7B and 25^7B-P,  Table 23;
limestone No. 2576 and 2576-P, Table  2U;  and limestone No. 2577 and
2577-P, Table 25.  Ferrous iron and pH versus time are shown, as well
as initial and final acidity of the coal  mine water.

From these data, the dolomitic limestones, No. 250*4- and 2576 were
ineffective as neutralizing agents even after having been pulverized
further (see No. 250^-P and 2576-P, Tables 17 and 2k).  The others,
all essentially high calcium limestones,  performed with varying degrees
of effectiveness.  The areas under the individual neutralization curves
relative to that of limestone No. 1809, which has been used most in
mine drainage studies at BCR, are presented in Table 26.  Limestone
No. 1809 is from the same source as,  and  is similar to,  No. 2522-P.
The difference in performance between 2522-P and 1809 with the South
Greensburg water (See Table 26) is attributed to differences in quality
of the discharge when each test was conducted.

The effect of particle size of the limestones on neutralization can be
seen in Figures 10, 11, and 12.  The  percent of limestone "as-received"
passing 200 mesh (from Table 12) is plotted against the relative areas
under the neutralization curves (from Table 26) for the synthetic coal
mine water, Figure 10; the South Greensburg water, Figure 11; and the
Thorn Run water, Figure 12.  In all cases, effectiveness of the lime-
stones increased with the smaller particle size fractions.

The effect of further pulverizing the limestones (and, therefore, the
effect of particle size) can also be  seen in the following neutral-
ization curves:  the finely divided limestones with synthetic coal
mine water, Figures 13 and 1^; with South Greensburg water, Figures 15
and 16; and with Thorn Run water, Figures 17 and 18.   The first of
the two sets of curves with each type of  water represents limestones
as-received; the second set of curves, limestones after pulverization
When the pulverized limestones were used, the neutralization curves of
10 of the 12 limestones became more similar, since the particle size
of the stone was made more similar.

The dolomitic limestones, No. 250^ and 2576, were no more effective
neutralizing agents even after the particle size was reduced sub-
stantially by pulverization.

It is significant that in no case were any special precautions nec-
essary in handling the limestones during  pulverization, analyses, and
testing.  The lesser reactivity of the limestones with mine water (as
compared to that of lime) is a distinct advantage to those who will
handle this chemical reagent.

In summary, the performance of the best of the finely divided lime-
stones in these batch neutralization experiments was similar to that
of limestone No. 1809.  Particle size, again, was determined to be a
most significant factor.  The possibility of using these limestones,
which are commercially available in a finely divided state, in a
                                  60

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TABLE 26.  RELATIVE AREA UNDER NEUTRALIZATION CURVES
   TWELVE FINELY DIVIDED LIMESTONES WITH SYNTHETIC
           AND TWO ACTUAL COAL MINE WATERS
   Limestone                      South        Thorn
     Number      Synthetic      Greensburg      Run

     2501            U5            27            31
     2502            U8            33            21
     2503            90            88            88
     250*4-            U3            29            19

     2522            52            55            70
     2523            73            63            77
     25*44            95            68            98
     25^5            86            68            90
                    10*4-           110           106
                     32            15            22
     2576            kk             7             1
     2577            89            76            75

     2501-P          88            67            93
     2502-p          87            99            91
     2503-P          97            75            99
     2504-P          k7            17            2*4.

     2522-P          98            83           100
     2523-?          88            66            92
     25M+-P          97            78            96
                    101           103           103
            p        103           H2           103
     25^7B-P         96            77            95
     2576-P         50            28            20
     2577-P         99            89            91

     1809           100           100           100
                             61

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  AREA  UNDER
NEUTRALIZATION
CURVES  RELATIVE
 TO LIMESTONE
    NO. 1809
110-


100-


 90-


 80-


 70-


 60-


 50-


 40-


 30-


 20-


 10-
                          Line Fitted by Method of Least Squares
              0    10    20   30    40   50    60   70   80    90   100
                     PARTICLE SIZE, PERCENT PASSING  200 MESH
                                           Bituminous Coal Research, Inc. 2036G8R1
      Figure 10. Effect of Particle Size  of Limestones  on Neutralization
                      of Synthetic Coal Mine Water
                                   62

-------
  AREA UNDER
NEUTRALIZATION
CURVES RELATIVE
 TO  LIMESTONE
    NO. 1809
           llO-i


          100-


           90-


           80-


           70-


           60-


           50-


           40-


           30-


           20-


           10-
                         •
Line Fitted by Method of Least Squares
                    \     I     T     I     I      I     I     I      I     I
                   10   20    30   40    50   60   70    80   90   100
                       PARTICLE SIZE, PERCENT PASSING 200  MESH
                                            Bituminous Coal Research, Inc. 2036G7R1
      Figure 11. Effect of Particle Size of Limestones on Neutralization
                  of South  Greensburg Coal Mine Water
                                   63

-------
  AREA  UNDER
NEUTRALIZATION
CURVES  RELATIVE
 TO LIMESTONE
   NO.  1809
110-


100-


90-


80-


70-


60-


50-


40-


30-


20-


 10-
                                  Line Fitted by Method  of Least Squares
                   10    20   30    40   50    60   70    80   90   100
                      PARTICLE SIZE, PERCENT  PASSING 200  MESH
                                          Bituminous Coal Research, Inc. 2036G217R1
      Figure 12. Effect of  Particle Size  of Limestones  on Neutralization
                      of Thorn  Run Coal Mine Water

-------
ON
VJ1
                    pH
                                                                   150    180    210   240   270    300
                                                           TIME, minutes
                                                                                   Bituminous Coal Research, Inc. 2036G9R1
                                  Figure 13. Neutralization of Synthetic Coal Mine Water

                                       with Finely  Divided Limestones  "As Received"

-------
                                         2547A-P
cr\
                 pH
                                            2547B-P
                                           2503-P
                                      30     60    90    120    150    180    210    240   270    300
                                                        TIME, minutes
                                                                                  Bituminous Coal Research, 2036G10R1
                         Figure 14. Neutralization of Synthetic Coal  Mine  Water  with  Finely
                                        Divided Limestones (After Pulverizing)

-------
ON
                         8-1
                         7-
                         6-
                   PH
                         5-
                         4-
                                                    2547A
                                       30     60    90     120    150    180    210    240    270   300
                                                         TIME,  minutes
                                                                                 Bituminous Coal Research, Inc. 2036G11R1
                            Figure 15. Neutralization of South Greensburg Coal  Mine Water
                                      with  Finely Divided Limestones "As  Received"

-------
PH
      8-,
      7-1
      6-1
      5H
      4-1
             0
                                     2545-P
                                                                           2547B-P
                               2577-P
                          2502-P^
                                   2522-P
 I
30
60
90
 120    150

TIME,  minutes
180    210    240   270   300
                                                             Bituminous Coal Research, Inc. 2036G12R
         Figure 16. Neutralization of South Greensburg Coal  Mine Water
                with Finely  Divided Limestones (After  Pulverizing)

-------
                                                                                                2547A
                                                                                                       2544
                   PH
o\
VD
                                                                                                       2576
                                    I
                                    0
30
 I
60
90    120    150   180

        TIME, minutes
                                        1
                                 T
              T
210    240   270    300


 Bituminous Coal Research, Inc. 2036G13R1
                                Figure 17. Neutralization of Thorn  Run Coal Mine Water

                                      with Finely Divided Limestones "As Received"

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pH
                        2547A -P
      7-
      6-
      5-
      4-
      3
                                         2547B-P
                    30    60    90    120    150   180    210   240   270    300
                                         TIME,  minutes
                                                             Bituminous Coal Research, Inc. 2036G1SR
              Figure 18. Neutralization of Thorn Run Coal Mine Water
                 with Finely Divided Limestone (After Pulverizing)

-------
treatment process depends on the results of the studies to optimize the
treatment process utilizing the continuous flow system.

Evaluation of Five Additional Materials

Five additional materials were received, but were less completely
evaluated than the 12 limestones.  These included aragonite, siderite,
and three waste materials.  All contained water and were dried prior
to testing and analyses.  The data from tests with synthetic coal
mine water are presented  in Table 27.  The aragonite, the orthorhombic
form of CaCOs, No. 15^9, was as effective a neutralizing agent as
calcite,  (the rhombohedral, most abundant form).  Siderite, No. 2578,
which is essentially FeC03, had little or no effect on neutralization.
The remaining three materials were described as principally limestones
but were  waste products  from the manufacture of asbestos products.
Two of them, No. 2603 and 26o4, exhibited properties similar to each
other, including neutralizing effectiveness.  The third, No. 2605, was
judged to be ineffective.

Sludge Properties

Properties of sludge formed during selected batch experiments with
the finely divided limestones were measured and are presented in
Table 28.  Synthetic and  two actual  coal mine waters, the South
Greensburg and Thorn Run  discharges, were employed in these tests.

Synthetic Coal Mine Water—A complete description of the neutralization
portion of each experiment with synthetic coal mine water has previously
been presented in the following tables:
                           Experiment
                              No.

                             396-k)
                             396-75
As presented  in Table  28,  sludge volumes ranged from 0.8 to 1.6 per-
cent;  solids  content of the  sludge  ranged  from 4.2 to 13.4 percent.
Experiments No. 4o6-l6-l and 4o6-l6-2 were conducted to check repro-
ducibility.   These  identical experiments produced reasonably compa-
rable  results.  Experiment No.  4o6-l6-3 was  also identical to
No.  4o6-l6-l  and  No. 4o6-l6-2,  but  in this experiment the sludge was
"aged" for 48 hours before putting  it in the Imhoff cone.  A lower
sludge volume and a substantially higher solids content resulted.  In
general,  the  more effective  iron removal resulted in a greater volume
of sludge.  Relatively effective limestones  were used in each of these
                                   71

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                       TABLE 27.  EVALUATION OF FIVE ADDITIONAL MATERIALS WITH
                                      SYNTHETIC COAL MINE WATER


                     Spectrochemical Analyses, Mineral Samples
                           Reported as Percent by Weight            X-ray       Area Under
 BCR                 	of Ignited Sample (900 C)	    Analyses   Neutralization  Percent
Sample                                                  Loss on   Compounds   Curve Relative  Moisture
Number  Description   CaO   _Mg°__   SiOv,  AlgOa  FesOa  Ignition  Identified   to No. 1809     105 C

 1549    Aragonite   95      1.98   1.37   0.3k   0.38    43.6    Calcite;        102
                                                                   Aragonite


 2578    Siderite     4.9    4.55  16.3    5.60  67.0     29.1    FeC03;            0.1
                                                                   SiOs


 2603    Waste       80     14.4    3.0    0.98   1.10    45.2        —          111          52.90


 2604    Waste       82      9.0    4.7    0.88   2050    44.5        —          HI          53.57


 2605    Waste       40     45.0   10.3    3.05   1.16    30.1        —            64          33.53

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                    TABLE 28.  PROPERTIES OF SLUDGE FORMED IN BATCH NEUTRALIZATION EXPERIMENTS
-o
u>
Volume
Experiment Limestone
Number
Number
A - Synthetic Coal Mine
396-i+0
396-75
1+06-16-1
1+06-16-2
1*06-16-3
1+06-18
B - South
1+06-27
1+06-28
1+06-26
1+06-29
C - Thorn
1+06-33
1+06-30
1+06-3^
i+06-31
2522
2522-P
2577
2577
2577
2577-P
5
min
Water
0.3
3.0
6.0
5.5
3.5
15.0
Greensburg Coal Mine
2576
2576-P
2577
2577-P
Run Coal Mine
2576
2576-P
2577
2577-P
0.1
0.2
0.1
0.1
Water
0.9
0.6
0.5
0.2
10
min

1.2
10.5
15.0
11.0
7.5
18.0
Water
0.1
0.2
0.2
0.1

1.1
3.0
15.0
1.1+
15
min

2.5
12.0
17.0
12.0
11.0
18.0

0.1
0.2
0.2
0.2

1.2
3.2
39.0
7.0
of Sludge, ml
30
min

5.5
12.5
16.5
12.0
12.0
17.5

0.1
0.3
0.5
0.1+

1.3
i+.o
33.0
30.0
^5
min

6.5
12.0
16.0
12.0
11.5
17.0

0.1
0.3
1.3
0.9

1.3
^.5
26.0
25.0
60
min

7.0
12.0
16.0
12.0
11.5
l60 5

0.1
0.1+
2.2
1.8

1.2
1+.5
25.0
2k. 0
2k
hr

8.0
13.0
15.5
12.0
11.5
15.5

0.8
1.9
7.0
5.5

1.1
k.6
22.0
21.8
Sludge
Volume
Percent
21+

0
1
1
1
1
1

0
0
0
0

0
0
2
2
hr

.8
.3
.6
.2
.2
.6

.1
.2
.7
.6

.1
.5
.2
.2
Solids
Content
Percent
2l+ hr

9.1
1+.2
6.3
8.1
13. ^
10.1

k.7
8.9
6.1+
7.6

1+8.8
26.0
12.5
11.1+
Initial
218
236
252
252
252
21+8
89
95
88
98
10
10
10
10
Final
33
7
17
15*
13*
1
89
85
6
ll+
1+6*
8*
21+4
7+
               * - To check reproducibility
               * - Sludge aged for 1+8 hours
              ** - Final acidity > 300 ppm
               4- - Final acidity < 5 ppm

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SLUDGE
VOLUME,
   ml
 5.0-|

 6.0-

 7.0-

 8.0-

 9.0-

10.0-

 11.0^

12.0-

13.0-

14.0-1

15.0-

16.0-

17.0-

18.0
                                      Experiment No. 406-16-1
                   5  10  15  20  25  30  35  40  45  50 55  60  24 (hr)
                                   TIME,  minutes
                                             Bituminous Coal Research, Inc. 2036G14R1
                  Figure 19. Settling Behavior of Sludge

-------
experiments.  Limestone No. 2522-P is from the same source as, and
should be reasonably identical to, Wo. 1809 which has been used ex-
clusively in the continuous flow experiments.

The settling behavior of these sludges can be described by a curve from
experiment No. 4o6-l6-l as presented in Figure 19.  The absence of a
boundary during settling prevented the measurement of settling rates in
the customary manner.

Limestone versus Lime Neutralization—Experiment No. 396-75 was repeated
(synthetic coal mine water with limestone No. 2522-P).  Initially the
synthetic coal mine water contained 230 mg/1 of Fes+ , U8? mg/1 of
acidity as CaCOg, and had a pH of 3.0.  After the standard 5-hour batch
experiment, the limestone-treated water contained 1 mg/1 of Fe3"1", minus
20 mg/1 of acidity of CaC03 (denoting alkalinity), and had a pH of 8.0.

Another 1,500 ml portion of the synthetic coal mine water was treated
with 1.1 times the stoichiometric amount of lime, Ca(OH)2, based on
acidity.  The solution was aerated for 30 minutes while being stirred
at the same rate as in the limestone batch experiments.  At the end of
this time the lime-treated water contained 1 mg/1 of Fe2*, minus 28 mg/1
of acidity as CaCOs  (denoting alkalinity) and had a pH of 7.6.

Each slurry was placed in an Imhoff cone and photographed at specific
time intervals.  After 5 minutes  (See Figure 20), some of the more
granular particles  (probably limestone) had already settled in the
Imhoff cone on the right.  The lime-treated material in the cone on
the left had not yet begun to settle.  After 30 minutes  (same figure),
the bulk of the limestone sludge  (cone on the right) had already
settled.  The water above the sludge was uniformly cloudy (and yellow)
at all depths in the cone.  The absence of any definite boundary
(other than the almost Immediate settling of the granular material at
the bottom) as the sludge settled is evident in this figure.  The
sludge from lime treatment  (cone on the left) can be seen settling much
more slowly with the typical definite boundary between sludge and clear
water on top.  The atypical settling rate curves can be attributed to
the absence of definite boundaries between limestone sludge and super-
natant liquid during settling.  Figure 19 described settling behavior
in a qualitative sense but was not meant to be a settling rate curve.

The next figure, No. 21, shows the settling of both sludges after
1 hour and 1 week.  The water above the limestone sludge is still some-
what hazy after 1 hour.  After 1 week, the water above each sludge was
clear.  At the end of this time the volume of the sludge from limestone
treatment was 1.2 percent; that from lime treatment was 6.8 percent.
The volume of sludge from lime treatment was greater than five times
that from limestone treatment.

The solids content of the sludge from limestone treatment was 8.9 per-
cent; that from lime treatment was 0.6 percent.  Solid content of the
limestone sludge was almost 15 times greater than that from treatment
                                   75

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Thirty  Minutes
  Lime
                                                (2036P8)
                                               Limestone
 (2036P3)
Limestone
  Figure 20. Lime versus Limestone Sludge after Settling
           for Five Minutes and Thirty Minutes

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                                              (2036P4)

                                            Limestone
                                              (2036P9)
                                            Limestone
Figure 21. Lime versus Limestone Sludge after Settling
            for One Hour and One Week
                         77

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with lime.  The quality of the original water being treated was identical
in "both cases.

South Greensburg Coal Mine Water— A complete description of the neutral-
ization portion of each experiment with the South Greensburg water has
been presented in the following tables :


                        Experiment     Table
                            No.         No.

                          ^06-27        2k
                          ko6-28        2k
                          ko6-26        25
                               9        25
As presented in Table 28, sludge volumes ranged from 0,1 to 0.7 percent;
solids content ranged from 4.7 to 8.9 percent.

Data on sludge properties can be evaluated only in terms of the neutral-
ization reaction which produced the sludge.  For example, experiments
using limestone No. 2576 and 2576-P resulted in substantially no re-
moval (oxidation) of ferrous iron because of the ineffectiveness of the
dolomitic limestone in increasing the pH of the coal mine water.  In
these instances, properties of sludge containing very little material
other than limestone are being measured.

Thorn Run Coal Mine Water — A complete description of the neutralization
portion of each experiment with the Thorn Run water has been presented
in the following tables :


                        Experiment     Table
                            No.         No.

                          ko6-33        2k
                               0        2k
                               k        25
                               l        25

As presented in Table 28, sludge volumes ranged from 0.1 to 2.2 percent;
solids content ranged from 11.5 to 48.8 percent.  The experiments with
the dolomitic limestone No. 2576 and 2576-P resulted in ineffective
neutralization; again the sludge consisted mainly of unreacted limestone.


                      Continuous Flow Experiments

The laboratory pilot plant described in a previous section was utilized
to optimize the continuous treatment of acid mine drainage with lime-
stone.  Tests were conducted with two actual mine waters—the South
Greensburg discharge which contained iron principally in the ferrous,


                                  78

-------
Fe3+ , state, and the Thorn Run discharge which contained iron prin-
cipally in the ferric, Fe3+ , state.  BCR limestone No. 1809 (minus
325 mesh), since the evaluation of limestones had shown it to be one of
the most effective neutralizing agents, was employed in all cases.
Variables studied were the amount of limestone, flow rate, aeration,
order of mixing and aeration (sequence of unit operations), and sludge
recirculation.  Because of the numerous conditions studied in con-
tinuous treatment, involving primarily the sequence of the mixing and
aerating operations and the specific tank to which recirculated slurry
was added, a thorough understanding of the nomenclature used to describe
these experiments is necessary.  The system of nomenclature is detailed
in the experimental section on page 22.

No Slurry Recirculation t  Effect of Flow Rate and Amount of Limestone

Flow rates of 0.5 and 1.0 gpm each, using twice (2X) and four times (^X)
the stoichiometric amount of limestone, were employed in four 1N-2A
continuous flow experiments involving treatment of South Greensburg
water.  The results of these experiments are presented in Table 29.

Although the pH of the raw mine water increased, essentially no decrease
in the Fe2+ concentration was observed during the initial 50-minute
batch mixing period in the limestone reactor.

The decrease in both pH and Fe2+ concentration after 30 minutes in the
settling tank under quiescent conditions without aeration indicates that
oxidation of Fe2+ was still occurring after treatment in all cases.
In at least one case, (Experiment Wo. U02-5), however, the Fe3"1" concen-
tration in the settling tank reached a value of 30 mg/1 within 2k hours,
and did not decrease further over an additional S-day period.
Doubling the amount of limestone employed had a more pronounced effect
on the efficiency of iron removal than did halving the flow rate,
i.e., doubling the theoretical detention time in the limestone reactor
to 100 minutes.  For example, halving the flow rate resulted in a 1.17-
fold increase in percentage Fe3* removed during treatment at both the
2X and 4x limestone levels .  Doubling the amount of limestone led to a
nearly 3-fold increase in percentage Fe3+ removed; the actual percent-
age increases were 2.95 and 2.9*1 times the initial values at flow rates
of 0.5 and 1.0 gpm, respectively.  The nearly perfect agreement between
these factors in each case may be fortuitous, especially since in some
instances the experimental conditions necessitated operating the lime-
stone feeder near its lower limit.  In fact, for the test with 2X lime-
stone and a flow rate of 0.5 gpm, the calculated feed rate could be
attained only by operating the feeder on a 5-minute on- off cycle.

The increased effectiveness of iron removal when Ux limestone was used
probably cannot be attributed to the slightly higher pH as compared to
the test with 2X limestone (See Table 29).  One possibility is that
some FeP+ was adsorbed on the surface of the excess limestone.
                                  79

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Co
o
                           TABLE  29.  EFFECT OF FLOW RATE AND AMOUNT OF  LIMESTONE  ON CONTINUOUS
                                      FLOW TREATMENT OF SOUTH GREENSBURG COAL MINE WATER
                                                       NO SLURRY RECIRCULATED
           Conditions  of Experiment*
           Experiment  No.
	Sampling Point

Eaw mine water

Limestone reactor
effluent after
batch mixing
period

Aeration tank
effluent after:

  Initial filling
  period

  60 min flow after
  filling was
  completed

Contents of settling
tank 30 min
after flow
ceased

Percent Fe8*
removed during
treatment**
    1N-2A

2X limestone,
 1.0 gal/min*

        Fe3*-!-
8k
82
78
70
                                             5.2
                                             6.2
                                             6.6
                                             6.6
                                             6.2
                                                 18
                                                            1N-2A
                                                            kO2-k
                                                        2X limestone,
                                                         0.5 gal/min*
5.5
6.k
6.6
6.6
              6.k
                               82
                               82
                               71
                               66
         65
                  21
                                       1N-2A
                                       1)02-6
                                    kX. limestone,
                                    1.0 gal/min*
                                    5.5
6.5
6.5
6.8
                                             6.5
         66
         31
                                         53
                            * Limestone reactor = 1; Aeration tank = 2; Ho aeration in the tank specified = N;
                              Aeration in the tank  specified = A.  Therefore, LA-2A specifies a limestone
                              reactor to aeration tank sequence with aeration carried out in both tanks.

                            4- All Fe3* concentrations are expressed as milligrams per liter (mg/l).

                           ** Based on analyses of  samples from settling tank 30 min after flow
                              ceased.
                                                1N-2A
                                                402-7
                                            kx. limestone,
                                             0.5 gal/min*
pH_

5.6
6.7
63
58
6.8      35


6.8      30



6.6      2k


     62
                            * Detention time at  1.0 gal/min = 50 min; at 0.5 gal/min = 100 min

-------
The most significant fact is that iron removals achieved in each of the
four experiments can not be considered satisfactory.  The results indi-
cate that, at least for this particular coal mine water, simple "one
pass" limestone treatment with aeration is not feasible using limited
amounts of limestone and retention times.  This finding is in agreement
with our earlier observations (l) regarding continuous flow limestone
neutralization of coal mine water containing iron principally in the
ferrous state.

No Slurry Recirculation;  Effect of Aeration and Sequence of
Unit Operations

In most of the following experiments the sequence of operations as
described in the general procedure was not followed.  This variation
necessitated the system of nomenclature used to illustrate the experi-
mental conditions in each test.  Twice the stoichiometric amount of
limestone was employed in this series of tests.

Aeration was carried out before and/or after addition of limestone in
eight experiments.  The South Greensburg water was treated at a rate
of flow of 1.0 gpm in each case.  The results of these experiments are
summarized in Table 30.  That the results are reproducible can be seen
by the results of duplicate experiments listed in this table.  Dupli-
cate experiments were conducted at random in all other series of experi-
ments but are not included in this report.  They, too, showed that the
results of these experiments are, in fact, reproducible.

Experiments UT-2A.  Two identical experiments were conducted using
these conditions.  This is essentially the general procedure followed
in past experiments.  Ferrous iron was removed as effectively as in
past tests.

Experiment 1A-2N.  No advantage was gained by aerating and mixing with
limestone at the same time.

Experiments 1A-2A.  Two identical experiments were conducted.  No advan-
tage was gained in removal of iron by aerating and mixing with limestone
followed by another aeration step.  Final pH (after 2^ hr) was slightly
higher than with no second aeration step.

Experiments 2A-1A.  In two identical experiments, the mine water was
aerated prior to and during mixing with limestone.  The percentage of
ferrous iron removed was essentially double that of the other experi-
ments reported here.  (See last line, Table 30.)

Experiment 2A-1N.  Again the mine water was aerated prior to mixing
with limestone; this time, though, there was no aeration during the
second step, mixing with limestone.  The percentage of ferrous iron
removal was still substantially doubled by the preaeration step even
without subsequent aeration.
                                  81

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CD
K>
                      TABLE  30.   EFFECT OF AERATION AND SEQUENCE OF UNIT  OPERATIONS ON CONTINUOUS
                                     FLOW TREATMENT OF SOUTH GREENSBURG  COAL MINE WATER
Conditions of
Experiment* 1W-2A 1N-2A
Experiment No. 1*02-8 1*02-17
Sampling Point pH Fe3+* pH Fe2+*
Raw nine water 5.0 91 5.2 72
Tank used in "first
unit operation"
after batch mixing
period 6.2 86 6.1* 68
Effluent from
"second unit
operation" after:
Initial filling
period before
start to flow 6.5 78 6.8 69
60 min after
start of flow
conditions 6.6 80 6.8 68
1A-2ET 1A-2A
1*02-9 1*02-11
jpH Fe3** pH Fea+*
5.1 82 5.1* 58
6.6 70 6.8 50

6.5 7!* 6.8 1*8
6.6 79 6.8 1*0
1A.-2A 2A-1A
1*02-12 1*02-11+
pH Fe3** pH FeSlf*
5.2 1+0 5.2 61+
6.5 30 6.1 62

6.6 32 6.7 51
6.7 29 6.6 1*2
2A-1A
1*02-16
•pH Fe3**
5.0 73
5.5 71*

6.1* 61*
6.7 1*8
2A-1H
1*02-15
. pH Fe3* *
5.2 73
5.8 73

6.7 61*
6.5 56
            Contents of set-
             tling tank 2l* hr
             after flow ceased    6.1    59

            Percent Fe3+ re-
             moved during
             treatment               35
6.3   39*  6.5    55    6.7
   37   6.7    27   6.1*    20   6.1*
22
    1*6
                33
36          32          69          70
6.3
            27
         63
                    * Limestone reactor = 1; Aeration tank = 2; Wo aeration in the tank specified = H; Aeration in the tank
                      specified = A.   Therefore, 1A-2A specifies a limestone reactor to aeration tank sequence with aeration
                      carried out in both tanks.

                    * All Fe3* concentrations are expressed as milligrams per liter (mg/l).

                   ** Contents of settling tank after week end (approximately 61* hr).

-------
In none of the experiments described above was the iron removal satis-
factory; therefore, the acidity value was not determined for this series.

An improvement, however, was seen in iron removal by the data from
experiments involving an aeration step prior to mixing the mine water
with limestone.  The experiments with and without the preaeration step
are compared in Figure 22.

Slurry Recirculation;  Effect of Flow Rate and Aeration in Only
One Tank

The results of the first series of experiments designed to examine the
effect of slurry recirculation on pH, iron content, and acidity are
summarized in Table 31-  The pH of the South Greensburg discharge, used
in almost all of the slurry recirculation experiments, ranged from 5-0
to 5-3? the ferrous iron concentration ranged from 6l to 90 rng/1, and
the acidity value as CaC03 equivalents ranged from 1^0 to 184 mg/1.
The raw water was treated at a flow rate of 0.5 gpm.  Slurry from a
previous experiment was stirred and the entire mass (sludge + treated
water) added to the tank specified at a rate of 0.5 gpm.  In each test,
twice the stoichiometric amount of limestone was employed.

Experiment 1N-2A(S).  In a typical experiment, 85 percent of the ferrous
iron was removed compared to 35 percent ferrous iron removed during a
similar experiment without slurry recirculation.  Little or no residual
acidity was found in the effluent.

Experiment lN(s)-2A.  Adding the slurry to the first unit operation
resulted in slightly improved ferrous iron removal--92 percent as
compared to 85 percent in the previous experiment 1N-2A(S).

Experiment 2A-lN(s).  Aerating the raw mine water followed by mixing
with slurry and limestone gave results similar to the previous experi-
ment 1KF(S)-2A.  These were the two most effective treatments in this
series.

Experiment 2A(s)-lN.  Less effective treatment was obtained from this
experiment in which the slurry was added to the raw mine water while
aerating, followed by mixing with limestone.

In general, recirculation of slurry improved the effectiveness of lime-
stone treatment as shown by pH and percent ferrous iron removed from
the raw coal mine water.  Residual acidity in the effluent in this
series of experiments was negligible.  (See Table 30, this report, for
a comparison with similar experiments involving no slurry recirculation.)

In the next experiments, with slurry recirculation and aeration in only
one tank, the raw water was treated and the slurry added to the tank
specified, both at 1.0 gpm.  The results of these experiments are
summarized in Table 32.  Also included in this table for comparison are
                                  83

-------
PERCENT Fe2+
  REMOVED,
  24 HOURS
    AFTER
FLOW CEASED
                                                                         With Preaeration
Without Preaeration
                     IN-2A   IN-2A   IA-2N   IA-2A   IA-2A             2A-IA   2A-IA   2A-IN
                                      SEQUENCE OF  UNIT  OPERATIONS
                                                                     Bituminous Coal Research. Inc.  2036G5R1
         Figure 22. Effect of Aeration and Sequence of Unit Operations on Continuous Flow
                         Treatment of South Greensburg Coal Mine Water

-------
                        TABLE 31.  EFFECT OF SLURR3C RECIRCULATION AND AERATION IN ONE TANK ON
                            CONTINUOUS  FLOW TREATMENT OF SOUTH GREENSBURG COAL MINE WATER
Co
VJl
Conditions of Experiment*
Experiment No.
Sampling Point
Raw mine water
Tank used in "first unit operation" after
batch mixing period
Effluent from "second unit operation"
after:
Initial filling period before
start of flow
60 min after start of flow
conditions
Contents of settling tank 24 hr after
flow ceased
Percent Fe2"1" removed during treatment
Acidity* of contents of settling tank
24 hr after flow ceased
1N-2A(S)
402-34
pH Fea+ *
5.2 75
6.3 75

6.9 31
6.9 26
6.4 n
85
+2
1N(S)-2A
402-21
PH Fea+*
5.2 79
6.5 48

6.9 46
6.6 36
6.5 6
92
+6
2A-1N(S)
402-32
_SH Fea+*
5.0 88
5.4 82

6.8 28
6.7 23
6.6 6
93
-7
2A(S)-1N
402-29
pH Fea+*
5.1 81
6.4 36

6.6 31
6.6 33
6.2 16
80
+16
               Limestone reactor = 1; Aeration tank = 2;  No aeration in the tank specified = N.  Aeration in the
               tank specified = A; Recirculated slurry added to the tank specified = (S).  Therefore,  1N(S)-2A
               specifies a limestone reactor to aeration  tank sequence with slurry added to the limestone reactor
               and aeration only in the aeration tank.

               All Fe3+ concentrations and acidity (as CaCO equivalents) expressed as milligrams per liter (mg/l).

-------
                       TABLE  32.   EFFECT  OF FLOW BATE AMD AERATION IN ONE TANK ON CONTINUOUS
                               FLOW TREATMENT OF SOUTH GREENSBURG COAL MINE WATER
CO
Conditions
of
Experiments*
1N-2A(S)
™(s)-"
2A-1N(S)
Experiment
Number
402-65
402-34
402-66
402-67
402-21
402-71
402-32
Total
Flow-
Rate
t
2.0
1.0**
2.0
2.0
1.0**
2.0
1.0**
Initial
4.8
5-2
4^9
5.2
4.9
5.0
Fe2+*
99
75
91
91
79
74
Acidity*
199
144
199
202
159
200
162
Final
pH Fes+*
6.3
6.4
6.4
6.4
6.5
6.1
6.6
22
11
23
34
6
37
6
Acidity*
30
2
25
32
6
16
-7
Percent
Removed
78
85
75
63
92
50
93
         *See Table 31 for labeling system.

        **Experiments at 1.0 gal/min were first described in Table 31.

         *A11 Fe2* concentrations and acidity  (as CaC03 equivalents)  expressed
          as milligrams per liter (mg/l).

         -(•Detention time at 2.0 gal/min = 25 min; at 1.0 gal/min = 50 min

-------
the results from the experiments with the same sequence of operations
but a flow rate of raw water and slurry of 0.5 gpm each (See Table 3l)•
In all cases, the lower flow rate of 0.5 gpm and, therefore, longer
detention (reaction) times resulted in a lower level of Fe   remaining
in the treated water (effluent); at a flow rate of 180 gpm, the lowest
level of Fes+ attained in the effluent was 22 mg/1 (experiment
No. ^02-65, a 1N-2A(S) experiment).  A pH greater than 6.0 was always
realized along with a very low level of acidity.  The most satisfactory
treatment occurred when the flow rate was 0.5 gpm.

Slurry Recirculation;  Effect of Flow Rate and Aeration in Two Tanks

The second series of experiments with slurry recirculation was conducted
to examine the effect of aeration during two unit operations.  The
South Greensburg water was treated at a rate of flow of 0.5 gpm and the
slurry added to the tank specified at a rate of flow of 0.5 gpm.  In
each test, twice the stoichiometric amount of limestone was employed.
The results are summarized in Table 33.

Experiment 1A-2A(S).  Aerating while mixing the raw mine water with
limestone in the limestone reactor, and aerating again while mixing
the recirculated slurry with raw mine water containing limestone in
the aeration tank, resulted in the most effective treatment with lime-
stone thus far.  Only 4 mg/1 (5 percent) of ferrous iron remained, with
no residual acidity in the effluent.

Experiment 1A(S)-2A.  Introducing the slurry to the first unit operation
in this experiment gave results comparable to those achieved in the
previous experiment IA-2A(s).

Experiment 2A-1A(S).  The treatment conditions specified in this experi-
ment also resulted in effective treatment.

Experiment 2A(S)-1A.  The conditions specified in this experiment re-
sulted in slightly less effective treatment than the other three experi-
ments in this series.  Even with the less effective treatment, ferrous
iron concentration in the effluent was only 7 mg/1.  There was a slight
(+22 mg/l) residual acidity.

Aeration during two unit operations along with recirculation of slurry
has resulted in the most effective treatment thus far.  This double
aeration might be acceptable as part of a treatment process since it
would effect a reduction in the holding times required in the limestone
reactor and aeration tanks.

In the next experiments with slurry recirculation and aeration in two
tanks, the raw water was treated and the slurry recirculated at a rate
of flow of 1.0 gpm each.  Detention time at 2.0 gpm flow was
25 min.  The results are summarized in Table 3^.  Also included in this
table for comparison are the results from the experiments with the

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                       TABLE 33.  EFFECT OF SLURBS' KECIRCULATION AND AERATION IN TWO TANKS ON
                           CONTINUOUS FLOW TREATMENT OF SOUTH GREENSBURG COAL MINE WATER


        Conditions of Experiment*                      1A-2A(S)       1A(S)-2A       2A-1A(S)       2A(S)-1A
        Experiment No.                                  402-39*-*       402-38**       402-36**       402-37**

        	Sampling Point	      pH   Fe3+ j    _p_H   Fe2+=j:    _j>H   re2**     pH   Fe3+i

        Raw mine water                                5.1     76     5.2     77     5.1     jk     5.3     74

        Tank used in "first unit operation" after
          batch mixing period                         6.6     67     6.7     27     6.1     74     6.6     30

        Effluent from "second unit operation"
          after:

co               Initial filling period before
                start of flow                         6.7     19     6.7     20     6.8     25     6.7     26

                60 min after start of flow
                conditions                            6.7     15     6.7     17     6.8     22     6.8     21

        Contents of settling tank 24 hr after
          flow ceased                                 6.6      4     6.6      4     6.4      6     6.4      7


        Percent Fe2+  removed during treatment             95              95             92             90

        Acidityt of contents of settling tank
          24 hr after flow ceased                         -3              +7             -2            +22


        * See  Table 31 for labeling  system.

        * All  Fe3+ concentrations and acidity (as  CaCOs  equivalents)  expressed as milligrams per liter (mg/l).

       **• Detention time = 50 min

-------
               TABLE 3k.  EFFECT OF FLOW RATE AM) AERATION IN TWO TANKS ON CONTINUOUS FLOW TREATMENT OF
                                           SOUTH GREENBBURG COAL MINE WATER
CD
VO
Conditions
of
Experiment*
1A-2A(S)



1A(S)-2A


2A-1A(S)

2A(S)-1A


Experiment
Number
402-68
402-69
402-74
402-39
402-70
402-75
402-38
402-73
402-36
402-76
402-37
Total
Flow
Rate
gpm4-
2.0
2.0
2.0
1.0**
2.0
2.0
1.0**
2.0
1.0**
2.0
1.0**
Initial

PH

4.9
5.0
5.1
4 9
k'.Q
5.2
4.9
5.1
4.9
5.3

Fe3+*
100
100
101
76
101
103
77
84
74
100
74

Acidity*
198
205
209
146
203
210
146
210
160
218
148

pH
6.4
6.3
6.5
6.6
6.2
6.4
6.6
6.0
6.4
6.3
6.4
Final

Fe2+*
20
11
17
4
6
19
4
21
6
9
7

Acidity*
20
4
5
-3
62
-1
7
21
-2
11
22
            *See Table 31 for labeling system.
           ^^Experiments at 1.0 gal/min were first described in Table 33.
            4=A11 Fe2+ concentrations and acidity (as CaC03 equivalents)
             expressed as milligrams per liter (mg/l).

            4-Detention time at 2.0 gal/min = 25 min; at 1.0 gal/min =  50 min

-------
same sequence of operations but a flow rate of raw water and slurry of
0.5 gpm each for a detention time of 50 min (See Table 33).  Again,
in almost all cases the lower flow rate of 0.5 gpm and, therefore.
longer detention (reaction) times resulted in a lower level of Fe *
remaining in the effluent; at a flow rate of 1.0 gpm, a level of Fe2* of
as low as 6 mg/1 was attained (experiment No. 402-70, a 1A(S)-2A
experiment).  Conditions 2A(S)-1A (experiment Wo. 4-02-76) also resulted
in a low level (9 mg/l) of Fe^+ in the effluent.  A low level of acidity
and a pH of at least 6.0 were always attained.

Slurry Recirculation;  Effect of 4x the Stoichiometric Amounts
of Limestone

In the third series of slurry recirculation experiments, the effect of
aerating during one unit operation, adding four times (4x) the stoichi-
ometric amount of limestone based on acidity, and/or using recirculated
slurry produced during a 4X limestone experiment was examined.  The
rate of flow of the treated water and the slurry was each 0.5 gpm for a
total flow of 1.0 gpm.  The results are summarized in Table 35-

Experiments 1N(S)-2A and 2A(S)-1N.  In these experiments, four times the
Stoichiometric amount of limestone based on acidity was used.  The
recirculated slurry was produced from previous experiments with twice
the Stoichiometric amount of limestone.  In both cases, the ferrous
iron content in the effluent was at the lowest point attained with any
experiments utilizing the continuous flow system.  The excess amount
of limestone is apparent from the negative acidity values, denoting
alkalinity.  The excess limestone was beneficial, even more so than in
previous experiments involving no slurry recirculation (See experiments
No. 402-6 and 402-7, Table 29).

Experiments lN(s)-2A and 2A-XN(S).  In both these experiments, twice the
Stoichiometric amount of limestone was used, but the slurry recirculated
was from experiments with four times the Stoichiometric amount of lime-
stone.  In the 1N(S)-2A experiment, iron removal was satisfactory and
the residual acidity in the effluent only slight.  In the 2A-1N(S)
experiment, however, only 82 percent of the ferrous iron was removed;
the residual acidity in the effluent was still +109 mg/1.  This was
the only experiment in this series in which the slurry was added to the
second unit operation; therefore, the need is clear for introducing the
slurry as early as possible in the treatment process to achieve maximum
benefit from sludge recirculation where aeration is not carried out in
both tanks.

Experiment 2A(S)-U\f.  In this experiment, (a) limestone was added at a
rate of four times the Stoichiometric amount, and (b) the slurry
recirculated was that from an experiment with four times the Stoichi-
ometric amount of limestone.  Under what may be described as extra-
ordinary conditions, essentially all (99 percent) of the ferrous iron
was removed.  The negative acidity of the effluent denotes alkalinity.
                                  90

-------
                        TABLE 35.   EFFECT OF SLURRY RECIRCULATIOW AND kX THE  STOICHIOMETRIC
                                     AMOUNT OF LIMESTONE ON CONTINUOUS FLOW TREATMENT
                                            OF SOUTH GREENSBURG  COAL MINE WATER
vo
H
Tank from "first unit
  operation" after batch
  mixing period

Effluent from ''second unit
  operation" after:

    Initial filling period
    before start of flow

    60 min after start of
    flow conditions

Contents of settling tank
  2k hr after flow ceased

Percent Fe3+ removed during
  treatment

Acidity* of contents of
  settling tank 2k hr after
  flow ceased
ltf(S)-2A4- 1N(S)-2A**
1*02-22 1*02-25
pH Fea+* pH Fe3"1"*
5.1 90 5.0 8k
6.5 51 6.6 38
6.8 k2 6.7 25
6.8 39 6.7 23
7.0 1 6.5 3
99 96
2A(S)-1W
pH Fe2+ *
5.0 81
6.6 1*5
6.7 31
6.7 22
6.6 3
96
2A-1N(S)** 2A(S)-1N#
1*02-26 1*02-21*
pH Fe3** pH Fe3**
5.1 79 5.0 79
5.6 8l 6.6 31
6.6 36 6.8 21
6.7 31 6.8 l4
6.1* lk 7.0 1
82 99
                                            -191
+10
-109
+109
-115
            * See Table 31 for labeling system.
            4. ^X limestone.
           *-* 2X limestone with slurry- from kx limestone experiment.
            # kx limestone with slurry from kX limestone experiment.
            * All Fe2+ concentrations and acidity (as CaC03  equivalents) expressed as milligrams per liter (mg/l).

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Even with the excess amount of limestone used in the experiments, there
would have been no harmful effect on the stream receiving this effluent.
The pH remained at 7 or less under conditions which simulated an
accidental overtreatment.

Slurry Recirculation;  Effect of Volume Recirculated

In this series of experiments, the amount (volume) of slurry recirculated
and mixed with the raw mine water was varied.  The South Greensburg water
was treated and the slurry recirculated each at a rate of flow of 0.5
gpm each.  The results are summarized in Table 36.  Experiment No.
1402-21 from Table 31 is included for comparison.

Experiments 1N(S)-2A.  In two experiments, the amount (volume) of sludge
recirculated and mixed with raw mine water was reduced from the
customary 1:1 ratio of raw water to slurry, as in past experiments, to
3:2 to 3:1.  In these experiments the slurry was introduced into the
limestone reactor tank.  There is a direct relationship between the
amount (volume) of slurry used and the effectiveness of ferrous iron
removal and neutralization, as evidenced by acidity.  This can be
seen in Table 36 and in Figure 23.  As the amount of slurry mixed with
the raw mine water is increased, there is a corresponding decrease in
ferrous iron concentration and acidity in the effluent.   For maximum
benefit in the treatment of this particular water, it was necessary
to add a volume of slurry at least equal to the volume of mine water
being treated.

The amount of slurry recirculated in the next series was twice that of
the raw water.  Again, the South Greensburg water was treated at a
rate of flow of 0.5 gpm and the slurry recirculated at 1.0 gpm.  Data
from these four experiments are summarized in Table 37.   Treatment,
as judged by pH, Fe2+ and acidity, was most effective in all cases.
The combination of long detention time and greater volume of slurry
than used in past experiments resulted in negative acidities,
denoting alkalinity in all cases.

Limestone Treatment of Thorn Run Coal Mine Water

In the first two experiments, no slurry was recirculated through the
system during treatment.  The raw mine water had a pH of 2.8 and
contained the following (in mg/l):  Fe3* , 21; acidity, 995; FeT, 138;
Al, 72; Mn, 11; Ca, 135; Mg, 58; and Si, 19.

In the first experiment the water was treated at a rate  of 1.0 gpm.
The results of this experiment, No. k02-Q8, are summarized in Table 38.
The effluent had a pH of 6.2 and contained the following (in mg/l):
Fe +, 3;  acidity, -85 (alkalinity); FeT, 5; Al, < 2; Mn, 11; Ca, 590;
Mg, 70; and Si, 18.  Treatment was most effective.
                                  92

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                      TABLE 36.  EFFECT OF THE VOLUME OF SLURRY RECIRCULATED ON CONTINUOUS FLOW
                                    TREATMENT OF SOUTH GREENSBURG COAL MINE WATER
Conditions of Experiment*
Experimental No.
Raw Mine Water: Slurry Ratio

Raw mine
Sampling Point
water
Tank from "first unit operation" after
batch mixing period
1N(S)-2A
1+02- *a
3:1
pH Fe2+*
5.1 61
6.1+ 1+9
1N(S)-2A 1N(S)-2A
1+02-1+2 1+02-21
3:2 1:1
pH Fe3+* pH I
5.0 71 5o2
6.6 la 6.5
nea+t
79
1+8
                   Effluent from "second unit operation" after:

                        Initial filling period before
vo                      start of flow                             6.8   U9      6.8   36     6.9   46
CO
                        60 min after start of flow
                        conditions                                6.7   1+0      6.8   36     6.6   36

                   Contents of settling tank 2l+ hr after
                     flow ceased                                  6.5   31      6.1+   15     6.5    6


                   Percent Fes+ removed
                     during treatment                                1+9            79            92

                   Acidity* of contents of
                     settling tank 2l| hr after
                     flow ceased                                    +1+6          +22           + 6

                      *See Table 31 for labeling system.
                      tAll Fe2+ concentrations and acidity  (as CaC03 equivalents)  expressed
                       as milligrams per liter (mg/l).

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                  Fe2+ AND ACIDITY
              (AS CaC03 EQUIVALENT),
                CONCENTRATION  IN
                THE  EFFLUENT, mg/l
                                       50-


                                       45-


                                       40-


                                       35-
VO
-p-
25-

20-

15-


10-

 5-
                                                   o Fe
                                                       2 +
                                                   • Acidity
                                               I      I     I      I     1      I     I      \     I      I
                                              0.1    0.2   0.3   0.4   0.5   0.6   0.7   0.8   0.9   1.0
                                                              SLURRY ADDED,  gpm
                                                            RAW WATER ADDED, gpm
                                                                                  Bituminous Coal Research, Inc.  2036G6R1
                            Figure 23. Effect of Volume of Slurry Recirculated on Continuous
                                 Flow Treatment of South Greensburg Coal Mine Water

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           TABLE 37.  EFFECT OF VOLUME  OF  SLURRY  RECIRCULATED ON CONTINUOUS FLOW TREATMENT
                                 OF SOUTH  GREENSBURG COAL MINE WATER


Conditions                   Raw Water     Recirculated    	Initial	  	Final	
    of         Experiment    Flow Rate,      Slurry,
Experiment*      Number         gpm            gpm	     pH  Fes+t  Acidity*    pH  Fe3+i  Acidityt



1A(S)-2A         if02-77         0.5            1.0         if.8    73     228      6.3     7      -2



1A(S)-2A         if02-78         0.5            1.0         if.7   100     225      6.6     1     -23
1A-2A(S)         if02-79          0.5            1.0         if.7   105     225      7.0     1     -21
2A-1A(S)         if02-80          0.5            1.0         if.6    90     221      6.7     7     -21
          *See Table  31  for  labeling  system.
          tAll Fe2"1"  concentrations  and acidity (as  CaC03  equivalents)
           are expressed  as milligrams per liter (mg/l).

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                                   TABLE 38.   CONTINUOUS FLOW TEEATMENT  OF THORN RUN
                                                     COAL MINE WATER
VD
Conditions
of
Experiment *
2A-]JT
2A-1N
2A-1W(S)
Experiment
Number
^02-88
^02-89
U02-90
Raw Water
Flow Rate,
gpm
1.0
2.0
1.0
Re circulated
Slurry
gpm pH
none 2.8
none 2 . 5
1.0 2.U
Initial
Fe^"1"* Acidity*
21 995
37 998
3^ 10^9
Final
pH Fe^"1"*
6.2 3
5.2 9
7.1 k
Acidity*
-85
-50
-15
              *See Ta"ble 31 for labeling system.
                   Fe2+ concentrations and acidity (as  CaC03  equivalents)  are expressed
               as milligrams per liter (mg/1 ) .

-------
In the second experiment, (No. 402-89) the flow rate was increased to
2.0 gpm.  The acidity was again negative, denoting alkalinity, and the
Fe2+ concentration was at a low level; however, final pH was only 5.2.
Detention times in this experiment would be only 25 minutes (2.0 gpm,
50 gallon reactor tank).

In the final experiment (No. 402-90), slurry was recirculated.  The
flow of water being treated and the slurry being recirculated were
each 1.0 gpm.  The effluent at a pH of 7.1, 4 mg/1 of Fes+ and a nega-
tive acidity reflects this as the most effective treatment.

Sludge Properties

Properties of sludge formed during selected continuous flow experiments
with the South Greensburg and Thorn Run waters were measured.  These
experiments involved both slurry recirculation and no slurry recircu-
lation.

South Greensburg Coal Mine Water:  No Slurry Recirculation--No. 402-85
was a typical 2A-1A experiment with the South Greensburg water in-
volving no slurry recirculation.  That this experiment resulted in
essentially ineffective neutralization and ferrous iron removal can be
seen by the data in Table 39» particularly the residual 73 mg/1 of
Fe2+ at the end of the experiment (See No. 4-02-85-2).  After 8 days,
residual Fe2+ was about 1 mg/1.  These data were used in Figure 24
to show the effect of aging of sludge on solids content.  Generally,
solids content increased with aging.  There seemed to be a difference
in solids content depending on whether the sludge was allowed to "age"
in the settling tanks or in the Imhoff cone (See No. 402-85-6).  A
relatively large decrease in solids content of the sludge was effected
by aerating a portion of the sludge again 15 days after the experiment
(See No. 402-85-5).

Thorn Run Coal Mine Water:  No Slurry Recirculation—Experiments
No. 402-88 and 402-89 have been described in Table 380  The data on
sludges from these experiments are listed in Table 39.  Again, as in
Table 28, which summarizes the data from the batch experiments with
Thorn Run and the finely divided limestones, the data show the rel-
atively high solids content of the sludge from treatment of this water
with limestone, even though no slurry was recirculated in any of these
experiments with the Thorn Run coal mine water.

South Greensburg Coal Mine Water:  Slurry Recirculation--Experiment
No. 402-80 has been described in Table 37.  The data on sludge from
this experiment, as listed in Table 40, show about the same solids
content as a sludge prepared in an experiment in which slurry was not
recirculated (See, for example, experiment No. 402-85-2, Table 39).

No. 402-87-7 was a 2A-1N(S) experiment.  Sludge solids content, as
listed in Table 40, was 6.5 percent and increased to 7-3 percent after
aging the sludge for 24 hours.
                                  97

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                        TABLE  39.   PROPERTIES  OF SLUDGE FORMED IN CONTINUOUS  FLOW EXPERIMENTS

                                               WITH NO  SLURRY RECIRCULATED
\o
oo
Experiment
Number
A . South
402-85-2
402-85-3
402-85-4

402-85-5
402-58-5
402-85-6
402-85-6
Volume of Sludge, ml
5 10 15 30 45 60
min min min min min min
Greensburg Coal Mine Water
0.3 1.3 2.5 3-0 3.5 4.0
0.0 0.0 0.1 0.7 1.5 2.5
0,0 0.0 0.3 1.5 2.7 5.0

8.5 9.5 9.8 10.0 10.5 10.5
0.5 6.0 11.0 ll.O 11.. 0 11.5



24
hr
5.0
3-5
5.0

11.0
13-0
10.0
10.0
Sludge
Volume
Percent
24 hr
0.5
0.4
0.5

1.1
1.3
1.0
1.0
Solids
Content
Percent
24 hr
6.0
7.3
9-0

9.2
6.3
9.9
8.2
Experimental*
Conditions
2A-1A
2A-1A
2A-1A

2A-1A
2A-1A
2A-1A
2A-1A
Comments
73 mg/l
residual Fe
After 1 day,
41 mg/l
residual Fe2"1"
After 8 days,
1 mg/l
residual Fe
After 15 days
Same as above;
after aeration
After 17 days
Same as above;
in cone over
weekend
B. Thorn Run Coal Mine Water
402-88-2
402-89-3
0.5 l.O 23.0 17.0 17.0 17.0
0.4 10.0 13.0 12.0 12.0 12.0
17.0
12.0
1.7
1.2
10.6
10.0
2A-1N
2A-1N


            See Table 31 for labeling system

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          Experiment No. 402-90, Thorn  Run Coal Mine  Water
          13.0-1


          12.0-


          11.0-


          10.0-


          9.0-


          8.0-

 SOLIDS

CONTENT, 7.0-

 PERCENT

          6.0


          5.0-


          4.0-


          3.0-


          2.0-


           1.0-


          0.0
         Experiment No. 402-85, South Greensburg Coal Mine Water
I
2
                    I
                   6
                                         I
                                        10
 I
12
 I
14
 I
16
 I
18
20
 I
22
                            TIME,  days
                                    Bituminous Coal Research, Inc. 2036G16R1
Figure 24. Effect of Aging on Solids Content of Sludge

        Formed in Continuous Flow Experiments
                          99

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                  TABLE kO.  PROPERTIES OF SLUDGE FORMED IN CONTINUOUS FLOW EXPERIMENTS
                                       WITH RECIRCULATED SLUERY
                   Volume of Sludge, ml
                                    Sludge    Solids
                                    Volume    Content
Experiment
  Number
      10   15   30   45   60  2k    Percent   Percent  Experimental
min  min  min  min  min  min  hr
A—South Greensburg Coal Mine Water

402-80-7     1.6  2.0  2.5  3.0  3-5  4.0  3.6
2k hr
                                      O.k
2k hr    Conditions*
Comments
           6.6
           2A-1A(S)   2:1 Slurry:raw
                       water ratio

H
0
O



402-87-7
1102-87-8
B~ Thorn Run
402-90-8
402-90-8
1+02-90-9
^02-90-10
0.0
0.0
Coal
0.1
0.1

0.1 O.k
0.0 0.0
0.8
0.1
1.0 1
O.k 0
.0 3-5
.6 1.5
O.k
0.2
6.5
7.3
2A-IN(S)
2A-IN(S)

Same as
but 24

87-7,
hr later
Mine Water
0.3 8.5
3.0 10.0

7.0 10.0 12.0
11.0
9.0

12.0
10.0 10
8.5 9

12.0 12
.0 10.0
.0 10.0

.0 12.0
1.0
1.0
1.2
7.6
5.9
9.4
13.0
2A-IN(S)
2A-IN(S)
2A-IN(S)
2A-IN(S)

Same as

90-8,
aerated 2 hr
After 3 days
After 8 days
  * See Table 31 for labeling system

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Thorn Run Coal Mine Water:  Slurry Recirculation—Experiment No. 402-90
has been described in Table 38.  Properties of the sludge from this
experiment are listed in Table 40.  Again, aerating the sample resulted
in a decrease in the solids content of the sludge (See experiment
Wo. 402-90-8).  The effect of aging the sludge was noted and the infor-
mation plotted on Figure 2k along with the effect of aging the South
Greensburg sludge from experiment Wo. 402-85.  A solids content of
this sludge of 13-0 percent after 8 days is one of the highest of this
series and can be considered quite desirable.

Effect of Shape of Vessel on Sludge Settling—It has been mentioned
that, in experiment Wo. 402-85 described in Table 39 and Figure 24,
there seemed to be a difference in solids content whether the sludge
"aged" in the settling tanks or in the Imhoff cone as shown by
Wo. 402-85-6.  To further examine this effect of shape of vessel on
solids content, we conducted the standard 2A-1U(S) continuous flow
experiment, Wo. 402-95-8, with the South Greensburg coal mine water.
Ferrous iron and acidity were relatively low and pH was 6.4 at the
end of this experiment.,  We then placed 1,000 ml aliquots of the slurry
containing sludge and treated water in the following vessels:  round-
bottom flask, beaker, Erlenmeyer flask, graduated cylinder, poly-
ethylene round bottle, and Imhoff cone.  The solids content of sludge
in each vessel is listed in Table 4l0  Those vessels which have sloping
sides resulted in a solids content of about 7 percent.  Those which
have perpendicular sides and relatively flat bottoms resulted in a
solids content of from 3 to 4 percent, the polyethylene bottle being
the single exception.
                                  101

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                TABLE 1*1.  EFFECT OF SHAPE OF VESSEL ON
                       SOLIDS CONTENT OF SLUDGE
Experiment
  Number

 11-02-95-8
1*02-95-8

1*02-95-8


1*02-95-8


1*02-95-8


1*02-95-8

1*02-95-8
              Experimental
               Conditions*
                 2A-1N(S)
                 2A-1N(S)
                 2A-1N(S)

                 2A-1N(S)
Solids Content,
Percent, 2k hr

     7-3
     3-1

     3.6


     3.9


     6.6




     7.1*
     Shape and
   Size of Vessel

Round bottom flask,
2000 ml

Beaker, 2000 ml

Erlenmeyer flask,
2000 ml

Graduated Cylinder,
1000 ml

Polyethylene Bottle,
round, 2 gal

Imhoff cone, 1000 ml

Imhoff cone,
1000 ml, to
check reproducibility
    *See Table 31 for labeling system
                                  102

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                               SECTION VII

              EVALUATION OF BCR LIMESTONE TREATMENT PROCESS


The following discussion of the projected full-scale operation of the
BCR limestone treatment process is based on the laboratory studies
described in the previous section.  The discussion of the application
of this process centers only on the limestone treatment of coal mine
drainage containing ferrous iron since most of the laboratory studies
have been conducted using synthetic coal mine water, which is essen-
tially a solution of ferrous sulfate, and also with the South Greensburg
discharge, an actual coal mine drainage containing iron principally in
the ferrous state.

The laboratory studies have (a) demonstrated the feasibility of this
treatment process using laboratory-scale pilot-plant apparatus,
(b) delineated the individual operations and sequence of operations
necessary for adequate treatment, and (c) established basic infor-
mation pertinent to engineering design of full-scale treatment plants.
Based on the results of these studies, a report was prepared (10)
relating experimental results to engineering design of full-scale
treatment plants.  For these engineering evaluations, flows of 0.1,
1.0, and 7.0 million gallons per day (mgd) were chosen and data devel-
oped for construction and operation of plants to treat discharges
having these flows.  The sponsors of this project then chose WQO, EPA
Class I mine drainage as the quality of mine water to be used in the
evaluations, since that type of mine drainage would present the
greatest problems in treatment.  The Class I mine drainage has the
following range in quality:


              pH                                2 - 4.5

              Acidity, mg/1 (as CaC03)      1,000 - 15,000

              Ferrous iron, mg/1              500 - 10,000

              Ferric iron, mg/1                 0

              Aluminum, mg/1                    0 -  2,000

              Sulfate, mg/1                 1,000 - 20,000


In addition to the Class I mine drainage, the South Greensburg dis-
charge used in the laboratory studies and having an estimated flow
                                   103

-------
of ^.0 mgd was also considered for this  evaluation.   This water has
the following average quality:


                Acidity,  mg/1 (as CaC03)            190

                Ferrous iron, mg/1                   90

                Ferric iron,  mg/1                     0

                Aluminum, mg/1                        8

                Sulfate,  mg/1                     1,200


Further experimentation will be necessary to determine the  optimum ratio
of sludge (concentrated solids) to raw mine water for this  process.
In the laboratory studies described in the previous  sections,  slurry
(sludge plus treated water) rather than  sludge,  was  recirculated due
to the nature of the pilot plant.  In this section which attempts to
project the results of the laboratory studies to full scale treatment
plants, the more familiar term "sludge"  will be  used for the recircu-
lated material.  Process materials balances based on the laboratory
studies will, therefore,  include the additional  water carried along
with the sludge.  Recognition is given to the necessity of  concentrating
the solids to be recirculated in an actual system.  The need for further
study in this area will be apparent.

               Description of Individual Treatment Units

The essential treatment units for the BCR limestone  treatment process
for a full-scale plant are, in flow-through sequence:  holding lagoon,
reactor tank, aeration tank,  settling basin, and sludge dewatering
basin.  Major equipment components of the process include a mixer,
mechanical aerators, limestone storage facilities and feeder,  and
sludge pumps.  A summary discussion of the design parameters and pro-
cess units employed by the proposed limestone treatment method follows.

A holding or equalization lagoon is the  first operation unit.   It
should be designed to provide a detention period of  12 hours for the
flow of mine water.  The principal function of this  unit is to level
out fluctuations in the flow of mine water and thus  provide a con-
tinuous supply of water to be treated during periods of intermittent
pumping from the mine.  Incidentally, this lagoon also serves to
level out fluctuations in raw water quality and  thus produce a narrow
range of acidity in the mine water supplied to the reactor  tank.
Based on the laboratory studies, the rate of limestone feed to the
process should be adjusted to provide a limestone to acidity ratio of
2:1.  Flow metering of the holding lagoon effluent in conjunction with
grab sample analyses for acidity is necessary for setting the rate of

-------
limestone feed.  The frequency of sampling required will depend upon
the degree of variation in mine water quality for each particular in-
stallation.

Provision for bulk storage of limestone at the treatment plant site is
recommended with a minimum of k days storage capacity.  It was assumed
for this evaluation that an acceptable grade of pulverized limestone,
comparable to the quality determined from past studies (l) to be
effective for treatment, can be supplied to the plant site.  The cost
advantage or disadvantage of pulverizing limestone on-site must be
determined for each particular installation and involves economic con-
siderations beyond the scope of this study.  Necessary provisions
should be made to reduce the dust problem associated with unloading
bulk trucks.  Vibratory-type feeders are recommended for controlling
the rate of limestone feed to the process.  "Live" bins are also
recommended.

The second treatment unit is the reactor tank, where pulverized lime-
stone and recirculated sludge are mixed with the coal mine drainage
for a period of 60 minutes based on the total combined flow of raw
water and recirculated sludge.  Laboratory studies have shown that opti-
mum treatment efficiencies are obtained when the mine water and lime-
stone feed are mixed with an equal volume of previously formed sludge
in the reactor tank.  This unit must be equipped with a mixer capable
of maintaining a complete mix of the tank contents.  Intimate contact
of the limestone and recirculated sludge with mine water constituents
is essential to initiate the neutralization reaction.  While the
volume of the reactor tank is fixed by the required detention period,
the dimensional design must be coordinated with the sizing of the
mixer to ensure adequate mixing.

An aeration tank sized to provide a 60-minute detention period is
recommended.  In the laboratory studies, diffused air was used to
successfully oxidize ferrous iron.  A diffused air system, however,
is probably not practical for a plant-scale aeration tank, and floating
mechanical aerators are recommended for the actual process application.
Aeration equipment and tank configuration must complement each other
to function as an efficient unit for providing complete mixing and
sufficient transfer of oxygen from the atmosphere to the water.  In
addition, adequate sparging action must be produced to cause the
release of carbon dioxide and, therefore, an increase in pH.  The
aeration tank effluent should be provided with a continuous pH moni-
toring system to indicate the completeness of the neutralization
reaction.

Settling basins with a 12-hour detention period are recommended.  The
design of these basins should include an influent trough which will re-
duce the influent approach velocity and distribute the flow across the
width of the basin.  Provisions should also be made in these basins to
reduce the possibility of short-circuiting, which would result in un-
settled sludge spilling into the receiving stream.
                                  105

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The sludge removal system must be capable of removing the settled solids
with a minimum of turbulence, so that the effective volume and retention
time of the settling basin is not reduced.  Sludge from the settling
basin will be pumped to a sludge recirculation well.  From this point,
it will be recycled to the reactor tank or wasted to sludge dewatering
ponds.  Dewatering ponds should be located in proximity to the treat-
ment facilities to further concentrate the waste solids prior to dis-
posal.  Ultimate disposal of the concentrated solids will be accomplished
by removal from the site by tank truck.  The supernatant from the
dewatering ponds will be decanted to the receiving stream.

          Flow Schematics, Unit Designs, and Material Balances

The plant flow schematics and unit designs presented in Figures 25
through 27 inclusive and material balances presented in Figures 30
through 38 inclusive are based on limestone treatment of Class I coal
mine drainage by the BCR process at 0.1, 1.0, and 7.0 mgd flow rates.

For the purposes of this study, the following three cases of the Class I
mine drainage have been used to develop the flow schematics, unit designs,
and material balances:

          Case A:  Acidity, mg/1 (as CaC03)             1,000
                   Ferrous iron, mg/1                     500
                   Ferric iron, mg/1                        0
                   Aluminum, mg/1                           0
                   Sulfate, mg/1                        1,000

          Case B:  Acidity, mg/1 (as CaC03)             8,000
                   Ferrous iron, mg/1                   5,000
                   Ferric iron, mg/1                        0
                   Aluminum, mg/1                         500
                   Sulfate, mg/1                       10,000

          Case C:  Acidity, mg/1 (as CaC03)            15,000
                   Ferrous iron, mg/1                  10,000
                   Ferric iron, mg/1                        0
                   Aluminum, mg/1                       2,000
                   Sulfate, mg/1                       20,000

In addition to the data for the Class I coal mine drainage cases dis-
cussed above, a plant flow schematic and unit designs and a material
balance for treating South Greensburg coal mine drainage at a k.O mgd
flow rate have been presented in Figures 28 and 39.  A proposed plant
layout and hydraulic profile for the same discharge is shown in
Figure 29.  The average quality of the South Greensburg coal mine water
is shown on page 104.

The following assumptions were made for the purpose of completing the
plant design data and material balances:
                                  106

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     The limestone requirement is twice the stoichiometric amount
     based on acidity.

     A recirculated sludge to coal mine drainage feed ratio of 1:1 is
     required.  (Actually, a 1:1 ratio of slurry to coal mine drainage.
     See laboratory studies.)

     Twenty-five percent of the limestone feed remains unreacted in
     the sludge.

     All but 7 mg/1 of the initial iron present is precipitated in the
     sludge as ferric hydroxide.

     All of the initial aluminum is precipitated in the sludge as
     aluminum hydroxide.

     Calcium sulfate (gypsum) is not precipitated in the sludge.

     Sludge solids content is five percent.

     Sludge specific gravity is 1.05.

Most of the above were determined from the laboratory studies, with the
following exceptions:  The experimental data on treatment of the South
Greensburg water did not indicate the formation of gypsum.  However,
with treatment of Class I mine drainages, it is expected that the solu-
bility product of calcium sulfate will be exceeded and gypsum will, in
fact, be precipitated in the sludge.  Nevertheless, the formation of
gypsum was ignored, since it could not be determined from the labora-
tory studies where the gypsum would precipitate.  Also formation of
this material in the mixing and aeration tanks could result in coating
of equipment and loss of efficiency of that equipment--all considered
beyond the scope of this study.  Furthermore, it was apparent that the
recommended studies with waters resembling Class I discharges would be
necessary to obtain data which could be used for plant design and
material balances and which would include formation of gypsum.

              Summary Technical Evaluation of the Process

Based on the laboratory studies and on consideration of the individual
treatment units, flow schematics, unit designs, and material balances,
the following is a summary evaluation of the BCR limestone treatment
process as it applies to plant scale treatment of coal mine drainage.

     A holding lagoon capacity corresponding to twelve hours
     retention is necessary to ensure a constant quantity of
     mine water during periods of intermittent pumping from
     the mine and to level out raw water quality.
                                  10?

-------
                                                                  10
                                                                                              rx.   EFFUJEf
                                                                                             —W>	RECEIVE
r SLUDGE
SK
-<=1
1



C^

~xl 15^-
1
WASTE SLUDGE
BASIN
1 1
                                                                                              SLUDGE PUMP

                                                                                                 -SLUDGE T
         TABULATION OF PLANT FLOWS a UNIT DESIGN BASIS FOR 0,1 MGD TREATMENT PLANT
c
A
&












LINE LOCATION
TREATMENT PLANT
INFLUENT CONDITIONS
BOOTY I.OOO MS/
rCftflOUS WON 500MG/
ALUMINUM OMG/
SULFATE I.OOOMG/
•C1CMTY 8.0 00 MS/
FERROUS IRON 5.0 CO 1*3 /
ALUMINUM I.SOOMG/
SULFATC 10,000 MQ/
ACIDITY 15,000 1*3/
FERtnU3 MON IO.OOO MO/
ALUWNUW 2,000 MO/
SULFATE 20,000 MO/L
I
HOLDMG LKOOH
ZfQ






' '





2
LUiEJTOt*












3
"""FEED












4
PtiNT












5
ft£™C^*TED












6
^


























7
*aGOOH

50'LG<30'W
i 10'SWO



» 10'SWD


SO'LQj(3O' W
x 10'SWO

8
"f-flkH*H

IZ'LOilZ'w
i 8'SWO



xS'SWD


IZ'Lan 12' W
i 8' SWD

9
U^M

IZ'LQ.llZ'W
i 8'SWO


12' La x 12' W
i 8'SWD


I2'LG.»I2'W
*8'SWD

10
6ASJN

9S'LQ.«43'W
x 9'SWD



K9'SWD


lOS'LG, » 46'W
i 9' SWD

II
DCWTMNG

73' LQ.x 46'W
1 10'SWD



* 10'SWO


3OO'LG.»I5O'W
* C'SWD

12
UN

3



3
830 FT


670 FT3


LENGTH
WIDTH
SIDE WATER DEPTH
                                                                       Bituminous Coal Research, Inc. 2036G19

           Figure 25. Plant Flow Schematic, Plant Flows and  Unit Design Basis for

              0.1 mgd Limestone Treatment Plant for  Class I Coal Mine Drainage

-------
        COAL MINE OfiAlNAGE
                       HOLDING LAGOON
SETTLING BASIN
SLUDGE ,-"\
10 ~" J


SLUDGE

S\
r*

                                                                                                             -SLUDGE TO DISPOSAL
VQ
                   TABULATION  OF PLANT FLOWS 8 UNIT DESIGN BASIS FOR IOMGO TREATMENT PLANT
s
N
a

A


B


C

LINE LOCATION

*aanr 1,000 M»/L
ALUMINUM OUG/L
SULFATE 1,000 WL
ACIDITY 8,000 HG/L
FERROUS IRON S.OOOMG/L
SULFATE |O,OOOMG/L
ACWTY I5.OOOMG/L
fEUWOUS RON mOOOMG/L
ML FATE 2AOOOMQ/L
1


1,000.000


1,000,000


1,000,000

2
3Z,

16,700


133,000


250.0OO

3
LKOAT

8 3


8.3


8 3

4
"V-,1"1

973,000


715,000


383,000

5
%"S'

1,000,000


1,000,000


1,000,000

6
v;r

27,500


286,000


617,000












7
-^

< 10'SWD


I25'LG.«7O'W


I23'LG.«7O' W

8
»M

i M'SWD


4O'LG » 20 'W


4O'LG,»20' W

9
"-

x I2'SWD


30'LG»30'W


Wunww

10
e*»

I 9'SWD


243'LG « 99' W


264' LG t KWW

II
IAS; H

i 12'SWO


315 'LG «27oV


780-USK38SV.

12
";""'

1.1 10 FT3


8,900 FT3


16,600 FT3

       LG  - LENGTH
       W  - WIDTT1
       SWD - SIDE WATER DEPTH
                                                                                  Bituminous Coal Research, Inc. 2036G20

                    Figure 26. Plant Flow  Schematic, Plant Flows and  Unit Design Basis for

                        1.0 mgd Limestone Treatment Plant for Class  I Coal Mine Drainage

-------
SETTLING BASIN ^^^
SLUOGE f}
1 (~1 PUMP \ )
10 \S
WELL
1



'-i
P
f\ SUPE
| 	 |>«ECE
fSLU
AV
                                                                                                       EFFLUENT TO
                                                                                                  ,-SLUDGE PUMP
                                                                                                  •\Vj)~C>	S4.UOGE TO D
                                                                                           WASTE SLUDGE
                                                                                            OEWATERING
                                                                                             BASIN
            TABULATION  OF PLANT FLOWS a UNIT DESIGN BASIS FOR 70 MGD TREATMENT PLANT
c
A
S
a




Q


C

LINE LOCATION

ACIWTY I.OOO MO/
FERROUS IRON 9 00 HO/
ALUMINUM OMQ/
SULFATE I.OOO MO/
AClOITT 8,OOOU3/
ALUUINUH I.SOOMQ/
SULFATE 10,000 MS/
ACIDITT HOOO MG/
FERKOUS RON 10,000 HO/
SULFATE tO,OOOMQ/L

"'£%"


1




TpOOpOO

2
L£O«







1 ,750,000

3








5B

4








2,680,000

5



1




7,000,000

6
*H,™







4, 3 20000












7
L*COOK

SIO'LGHWO'W
x 10'SWD

3»'LGjtl60'W


3IO'LG ilGO'W

8
TAH.

na'Lc.n^w
* 13'SWD

II5'LQ.M46'W


ll5'LG«4e'W

9
""-

I30'LG.X45'W
X I4'SWD

!3O'LGi45'W


30'LGii4S'W

10
MSN

350'U3.K2001W
» 10' 3WD

39dU3.i2IO'W


650' LG K 230W

II
"vsr

4OO' LGji 2Q01*
» 12' 5WD

IZOO'LGiGCO'W


1760'LG n900'w

12
"°.""







le.yeorr^

LG - LENGTH
W - WIDTH
SWD - SIDE WATER DEPTH
                                                                           Bituminous Coal Research, Inc. 2036G21
                Figure 27.  Plant Flow Schematic, Plant Flows and Unit Design Basis  for
                   7.0 mgd Limestone Treatment Plant for Class I Coal Mine Drainage

-------
COAL MINE DRAINAGE
                MOLDING LAGOON
SETTLING

10


"""• (J
                                                                                                    |\   EFFLU
                                                                                                    (o> - RECEI
                                                                                                   SUPERNATANT TO
                                                                                                   RECEIVER; STREAM
                                                                                                        SLUDGE TO DISPOSAL
            TABULATION  OF PLANT FLOWS ft UNIT DESIGN BASIS FOR 40MGD  TREATMENT PLANT
LINE LOCATION
TREATMENT PLANT
INFLUENT COMOITtON*
•OOTT IBOMO/U
FZMQLM »WN 90MQ/L
fcLlMNUN BMa/L
•ULFATC L200UQ/L
I
MXM& LACOOK
4,000,000
2
..'•/«
12.700
3
1.1/OAT
334
4
•".«-
3,990,000
5
WCSLJOG[TC°
4,000,000
6
&TD
21,200


7
S£:
250'LH>I30'W
I K}' SWD
8
^TtHt"
70' LG • 35' W
> h
-------
         PROPERTY BOUNDARY^ _
    HOLOWG S EQUALIZATION LAGOON

    CAPACITY 2.000.000 GALLONS

    SIZE SO'LG . 130'W" 10' SWD
    WED ACCESS ROAD
  PROPERTY AREA REQUIRED

   93S'LG . 360'*
   7 TS ACRES (APPROX )
:LOW
METER1
•LUME,

REACTOR




„ ™N™

M'SWD




OL BL






*

ERATIO
TLB.SS






N TAN






1





f, 	 : 	 ft
i
SETTLING BASIN
SIZE 420' LG i 143'W i 10' SWD
CAPACITY 4,000,000 GALLONS


[ 1

-







24" DIA
OR AS RE
TO STRE




           PROPERTY BOUNOAf
                                       PLAN
                                     SCALE: i* • 4tf
                         /WS EL 9900     ^WS EL
                         ( _A  A   A ( A
_£GROUNOJ-I NE ,-«S EL fOO OO 	 ,
Z4'DIA PIPE/ A r~~~~
OftASREQ'D-^ \ HOLDING S EOUA LIZATWN LAGOON /



REACTOR AERATION
SECjiQ^
,-WS EL 9700^, -J4"
	 — /-V— - J i / \ 1 W
A- A

                                                                     Bituminous Coal Research, Inc. 2036G23
Figure 29. Plant Layout and Hydraulic Profile for 4.0 mgd Limestone

     Treatment Plant for South  Greensburg Coal Mine Drainage

-------
Coal mine Drainage
Flow, mgd
Acid, mg/l
Acid, Ibs
Fe, mg/l
Fe, Ibs
Al, mg/l
At, Ibs
SO4, mg/l
SO4, Ibs
V
Hold' L
ing agooi



0.1
1,000
834
500
417
0
0
1,000
834
Limestone
Storag e
Treated Water


N. Bin /

>v /
| Coagulant
0 Aid
^Y Storage
1,670 Ibs 0.8 Ibs
^ r


i k >
A;,

i

Recirculated Sludge








Flow, gal/day 97,300
Acid, mg/l
Acid, Ibs
Fe, mg/l
Fe, Ibs
Al, mg/l
Al, Ibs
SO4, mg/l
S04, Ibs







0
0
7
6
0
0
1,030
834
A



                                   f
                          Sludge to Dewatering Basin
Fe(OH)3, Ibs
Limestone, Ibs
AI(OH)3, Ibs
Coagulant Aid, Ibs
Sludge, Ibs
Sludge, gal
785
417
0
0.8
24,100
2,750
                                                        Bituminous Coal Research, Inc. 2036G24
Figure 30. Material Balance for Limestone Treatment of Class I, Case A
                 Coal Mine Drainage at 0.1 mgd Flow  Rate

-------
Coal /Wine Drainage
Flow, mgd
Acid, mg/l
Acid, Ibs
Fe,
Fe,
mg/l
Ibs
Al, mg/l
Al, Ibs
SO4, mg/l
SO4, Ibs



V
Holding Lag

8,
6,
5,
4
0.1
000
670
000
,170
500
417
10,000
8,




340
Limestone
Storage
\ Bin

\/


/


V
13,300 Ibs

Treated Water




















Coagulant
Aid
Storage
0.8
> t
Rea


t i
A;,
ator Tank
•
f
bs

^




w



Flow, gal/day 71,500
Acid, mg/l
Acid, Ibs
Fe,
Fe,
mg/l
Ibs
Al, mg/l
Al, Ibs
SO4, mg/l
S04, Ibs

Settlinc

Recirculated Sludge














0
0
7
4
0
0
14,000
8,340
A




                         Sludge to Dewatering Basin
Fe(OH)3, Ibs
Limestone, Ibs
AI(OH)3, Ibs
Coagulant Aid, Ibs
Sludge, Ibs
Sludge, gal
7,950
3,340
1,210
0.8
250,000
28,500
                                                      Bituminous Coal Research, Inc. 2036G25
Figure 31. Material Balance for Limestone Treatment of Class I, Case B
              Coal Mine Drainage at 0.1 mgd Flow Rate

-------

Coal Mine
Drainage
Flow, mgd
Acid, mg/l
Acid, Ibs
Fe,
Fe,
mg/l
Ibs
Al, mg/l
Al, Ibs
S04, mg/l
SO4, Ibs


) r
Holding Lag

15,
12,
10,
8,
2,
1,
20,
16,

0.1
000
500
000
340
000
670
000
700
Limestone
Storage
\ Bin
\ /




Treated Water


/

















| Coagulant
0 Aid
\S Storage
25,000 Ibs
0.8
> r
n n 1 1 W


Rea


> k
A:,
ator Tank
j
k
bs
>



r
w



Flow, gal/day 38,300
Acid, mg/l
Acid, Ibs
Fe,
Fe,
mg/l
Ibs
Al, mg/l
Al, Ibs
SO4, mg/l
S04, Ibs

Settlinc

Recirculated Sludge











0
0
7
2
0
0
52,200
16,700
A


                                   f
                         Sludge to  Dewatering  Basin
Fe(OH)3, Ibs
Limestone, Ibs
AI(OH)3, Ibs
Coagulant Aid, Ibs
Sludge, Ibs
Sludge, gal
15,900
6,260
4,820
0.8
540,000
61,700
                                                       Bituminous Coal Research, Inc. 2036G26
Figure 32. Material Balance for Limestone Treatment of Class I, Case C
               Coal /Wine Drainage at 0.1 mgd Flow Rate

-------
Coal Mine Drainage
Flow, mgd
Acid, mg/l
Acid, Ibs
Fe, mg/l
Fe, Ibs
Al, mg/l
Al, Ibs
$04, mg/l
S04, Ibs
> <
Holding Lagoor

1.0
1,000
8,340
500
4,170
0
0
1,000
8,340
Limestone
Storage
N. Bin /
\ /
x/
v
16,700 Ibs
Treated Water





Coagulant
Aid
Storage
8.3 Ibs
1 1
, | 	 ^ Rea


> k
A:,
t







Flow, gal/day 973,000
Acid, mg/l
Acid, Ibs
Fe, mg/l
Fe, Ibs
Al, mg/l
Al, Ibs
SO4, mg/l
S04, Ibs


p. g

0
0
7
57
0
0
1,030
8,340
i k


Recirculated Sludge






                                  f
                        Sludge to  Dewatering Basin
Fe(OH)3, Ibs
Limestone, Ibs
AI(OH)3, Ibs
Coagulant Aid, Ibs
Sludge, Ibs
Sludge, gal
7,850
4,170
0
8.3
241,000
27,500
                                                     Bituminous Coal Research, Inc. 2036G27
Figure 33. Material Balance for Limestone Treatment of Class I, Case A
              Coal Mine Drainage at 1.0 mgd Flow Rate

-------
Coal Mine
Flow, mgd
Acid, mg/l
Acid, Ibs
Fe, mg/l
Fe, Ibs
Al, mg/l
Al, Ibs
S04, mg/l
S04, Ibs
V
Holding Lag



Drainage
1.0
8,000
66,700
5,000
41,700
500
4,170
10,000
83,400
Limestone
Storage
Treated Water


N. B i n /

N< y'
] Coagulant
n A,-
Y' Storage
133,000 Ibs 8.3 Ibs
V
^
oon ^ -^
A >
A'.,

k

Recirculated Sludge








Flow, gal/day 715,000
Acid, mg/l
Acid, Ibs
Fe, mg/l
Fe, Ibs
Al, mg/l
Al, Ibs
SO4, mg/l
S04, Ibs

r
^ 9




0
0
7
42
0
0
14,000
83,400
1 1





                                   f
                         Sludge to Dewatering Basin
Fe(OH)3, Ibs
Limestone, Ibs
AI(OH)3, Ibs
Coagulant Aid, Ibs
Sludge, Ibs
Sludge, gal
79,500
33,400
12,100
8.3
2,500,000
285,000
                                                       Bituminous Coal Research, Inc. 2036G28
Figure 34. Material  Balance for Limestone Treatment of  Class I, Case B
               Coal  Mine Drainage at 1.0 mgd Flow Rate

-------
00
Coal Mine Drainage
Flow, mgd
Acid, mg/l
Acid, Ibs
Fe,
Fe
mg/l
Ibs
Al, mg/l
Al, Ibs
$04, mg/l
S04, Ibs



1 r
Holding Lag

15,
125,
10,
83,
2,
16,
20,
167,

^


1.0
000
000
000
400
000
700
000
000
Limestone
Storage
\ Bin

\x


/


V
250,000 Ibs
Treated Water




















Coagulant
Aid
Storage
8.3 Ibs
> r
Rea
t T k -fc- A
"^
t k
A:,
ator Tank
-
\

^



^~


Flow, gal/day 383,000
Acid, mg/l
Acid, Ibs
Fe,
Fe,
mg/l
Ibs
Al, mg/l
Al, Ibs
SO4, mg/l
S04, Ibs

Settlinc

Recirculated Sludge














0
0
7
22
0
0
52,200
167,000
n




                                                               f
                                                     Sludge to Dewatering Basin
Fe(OH)3, Ibs
Limestone, Ibs
Al(OH>3, Ibs
Coagulant Aid, Ibs
Sludge, Ibs
Sludge, gal
159,000
62,600
48,200
8.3
5,400,000
617,000
                                                                                   Bituminous Coal Research, Inc. 2036G29
                            Figure 35.  Material Balance for Limestone Treatment of Class I, Case C
                                            Coal Mine Drainage at 1.0 mgd Flow Rate

-------

Coal Mine
Drainage
Flow, mgd
Acid, mg/l
Acid, Ibs
Fe,
Fe,
mg/l
Ibs
Al, mg/l
Al, Ibs
SO4, mg/l
S04, Ibs



•> r
Holding Lag


7.0
1,000
58,400

500
29,200
1,
58,




0
0
000
400
Limestone
Storage
\. Bin

\/



Treated Water


/

















Coagulant
0 A"
^Y Storage
117,000 Ibs
58
> r
Rea


t k
A;,
ator Tank
'
k
Ibs

^




w



Flow, gal/day 6,810,000
Acid, mg/l
Acid, Ibs
Fe,
Fe,
mg/l
Ibs
Al, mg/l
Al, Ibs
SO4, mg/l
S04, Ibs

Settlinc

Recirculated Sludge













0
0
7
397
0
0
1,030
58,400
A




                                  f
                         Sludge  to Dewatering Basin
Fe(OH)3, Ibs
Limestone, Ibs
AI(OH)3, Ibs
Coagulant Aid, Ibs
Sludge, Ibs
Sludge, gal
55,000
29,200
0
58
1,680,000
192,000
                                                       Bituminous Coal Research, Inc. 2036G30
Figure 36. Material Balance for Limestone Treatment Class I, Case A
                Coal Mine Drainage at 7.0 mgd Flow Rate

-------
H
rv>
o
Coal Mine Drainage
Flow, mgd
Acid, mg/l
Acid, Ibs
Fe, mg/l
Fe, Ibs
At, mg/l
Al, Ibs
SO4, mg/l
SO4, Ibs
V
Holding Lagoon



7.0
8,000
467,000
5,000
292,000
500
29,200
10,000
584,000
Limestone
Storage
\^ Bin /

N./'
Coagulant
U Aid
^r Storage
934,000 Ibs 58 Ibs
i r


I
Air ... ...J
Recirculated Sludge


1
Treated
Flow, gal/day
Acid, mg/l
Acid, Ibs
Fe, mg/l
Fe, Ibs
Al, mg/l
Al, Ibs
S04, mg/l
S04, Ibs
t
•• Settling Basin 1




Water
5,000,000
0
0
7
292
0
0
14,000
584,000
k




Sludge to Dewatering Basin












Fe(OH)3, Ibs 557,
Limestone, Ibs 234,
AI(OH)3, Ibs 84,
Coagulant Aid, Ibs
Sludge, Ibs 17,500,
Sludge, gal 2,000,
000
000
400
58
000
000






                                                                                  Bituminous Coal Research, Inc. 2036G31
                              Figure 37. Material Balance for Limestone Treatment of Class I, Case B


                                             Coal Mine Drainage at 7.0 mgd Flow Rate

-------
H
ro
H
Coal Mine
Flow, mgd
Acid, mg/l
Acid, Ibs
Fe, mg/l
Fe, Ibs
Al, mg/l
Al, Ibs
SO4, mg/l
SO4, Ibs
V
Holding Lag

Drainage
7.0
15,000
876,000
10,000
584,000
2,000
117,000
20,000
1,170,000
Limestone
Storage
\. Bin /
1 Coagulant
0 Ald
\S Storage
l,750,000lbs 58 Ibs
Treated Water
Flow, gal/day 2,680,000
Acid, mg/l 0
Acid, Ibs 0
Fe, mg/l 7
Fe, Ibs 157
Al, mg/l 0
Al, Ibs 0
SO4, mg/l 52,200
S04, Ibs 1,170,000
^r A
ir 	
oon P- P~ ^ g

M A
Air
Recirculated Sludge


1
Sludge to Dewatering Basin
Fe(OH)3, Ibs 1,110,000
Limestone, Ibs 438,000
Al(OH)3, Ibs 337,000
Coagulant Aid, Ibs 58
Sludge, Ibs 37,800,000
Sludge, gal 4,320,000
                                                                                  Bituminous Coal Research, lnc.2036G32
                             Figure 38. Material Balance for Limestone Treatment of Class I, Case C


                                           Coal Mine Drainage at 7.0 mgd Flow Rate

-------
ro
Coal Mine Drainage
Flow, mgd
Acid, mg/l
Acid, Ibs
Fe, mg/l
Fe, Ibs
Al, mg/l
Al, Ibs
SO4, mg/l
SO4, Ibs
V
H Id' L
o ing agoon


4.0
190
6,340
90
3,000
8
267
1,200
40,000
Limestone
Storage
Treated


N. Bin /

N. /
Coagulant
0 4rd
\/ Storage
12,700 Ibs 33.4 Ibs
Flow, gal/day
Acid, mg/l
Acid, Ibs
Fe, mg/l
Fe, Ibs
Al, mg/l
Al, Ibs
SO4, mg/l
S04, Ibs
>r *


1 1 >
A:,

i
Recirculated Sludge

Water
3,980,000
0
0
7
232
0
0
1,210
40,000
i


                                                              f
                                                     Sludge to Dewatering  Basin
Fe(OH)3, Ibs
Limestone, Ibs
AI(OH)3, Ibs
Coagulant Aid, Ibs
Sludge, Ibs
Sludge, gal
5,290
3,170
772
33.4
185,000
21,200
                                                                                  Bituminous Coal Research, Inc. 2036G33
                           Figure 39. Material Balance for Limestone Treatment of South Greensburg
                                           Coal Mine Drainage at 4.0 mgd Flow Rate

-------
     Manual control procedures for regulating the feed rate of
     limestone based on the acid loading of the raw water are
     required by the process.

     No insurmountable problems are anticipated with the on-site
     handling of pulverized limestone.  Major considerations
     would include dust control during unloading, and pre-
     venting moisture contact with the stored material.
     Vibratory-type feeders can be utilized for limestone
     addition to the process.

     Deposition of solids, particularly calcium sulfate,
     occurring in either the reactor tank or the aeration tank
     would pose an operational problem detrimental to process
     efficiency.  The necessarily large tanks, due to the
     60-minute detention time and the high solids content,
     impose critical design conditions for mixing and aeration.
     With high flows such as 7 mgd and high acid loadings, such
     as Case B and Case C of Class I as described, it is very
     unlikely that efficient mixing could be attained in the
     necessarily large reaction and aeration tanks required.

     Settled sludge in earthen basins, as the result of any
     treatment process, does not present a condition conducive
     to its efficient removal on a continuous flow basis.
     Handling large volumes of sludge, as required by recycling
     in this limestone treatment process, increases the problem.

As a result of the technical evaluation of the process, it has been
demonstrated that treatment of coal mine drainages such as the South
Greensburg water or the lower acid limits of Class I discharge (such
as Case A as described) is not only technically feasible, (as has been
established by the laboratory studies), but can be accomplished with
practical systems.  Treatment of those waters having high flow rates
and high acid loadings (Case B and Case C) present particular problems
which have not been solved by this study.  However, those waters are
not typical of coal mine drainage and can be considered rare, particu-
larly considering the concentration of iron.  An examination of four
reports (11, 12, 13, l4), which included analyses of coal mine dis-
charges in an area covering greater than 1,700 square miles in Ohio
and Pennsylvania, revealed that none of the discharges reported
approached the levels of acidity and iron described by Case B and Case C
This was also true in another report (15) describing the quality of one
creek in West Virginia which contributed 25 percent of the acid loading
to a basin containing an area of 38^ square miles.  In only a few in-
stances were discharges having the quality of Case A, Class I described
in these reports.

One of the problems presented by using the BCR limestone treatment proc-
ess can be considered a result of the 60-minute detention time due to
the relative insolubility of the limestone and the resultant sluggish-
                                  123

-------
ness of the ferrous iron oxidation reaction.   Studies which should re-
sult in enhancing the rate of oxidation of ferrous iron by using an
activated carbon catalyst are already underway at BCR (EPA Project
Wo. 1^010 GYH titled "Oxidation of Ferrous Iron in Coal Mine Water with
Activated Carbon Catalysts").  These studies  should offer a practical
solution to reducing the detention time necessary for the oxidation of
ferrous iron, thereby allowing smaller tanks  to be used with correspond-
ing greater efficiency in mixing.

The BCR limestone process should be studied on a larger scale since the
bench scale studies have not sufficiently defined the following:

     (a) the mixing requirements in the reactor tank,

     (b) the effect on cost of grinding coarse limestone versus
     the use of pulverized limestone,

     (c) the effect of using mechancial aerators,

     (d) the sludge recirculation ratio in an equilibrium con-
     dition and the effect of sludge properties such as solids
     content, alkalinity, etc. on process efficiency.

     (e) the effect on the system of treating coal mine drainages
     having sulfate concentrations of up to 20,000 mg/1 with
     resultant precipitation of gypsum,

     (f) the effect of coagulant aids on settling properties and
     on recycled sludge, and

     (g) the effect of more concentrated coal mine drainage on
     sludge volume.

                    Cost Evaluation of the Process

The development of cost data for construction and operation of full-
scale mine drainage treatment plants to treat Class I coal mine drain-
age is difficult because of the wide range of flow and quality con-
ditions included in Class I.  Furthermore, treatment plant costs will
vary due to the availability of suitable land, soil conditions, and
topography of the site.  For the cost analysis, it has been assumed
that sufficient land is available to construct the treatment units,
the topography of the proposed plant site is relatively level, the
proposed site does not have a high water table, the depth to bedrock
at the proposed plant site is a minimum of 10 feet, and soil at the
proposed plant site contains a high clay content.  In addition, it has
been assumed that the proposed holding basin could be constructed with
a water surface elevation sufficient to produce a gravity flow condi-
tion through the plant complex; therefore, the only pumping require-
ments would be for recirculation and wasting of sludge.
                                  12k

-------
The treatment facility designed to treat coal mine drainage containing
ferrous iron, using limestone as the neutralizing agent, consists of
the following unit operations, in flow-through sequence:  (a) holding
or equalization lagoon; (b) reactor tank; (c) aeration tank; (d) settling
basin, and (e) sludge de-watering basin.

The cost evaluation has been based upon the sequence of treatment units
outlined above and the plant operation procedures and assumptions des-
cribed in the following text.  The coal mine drainage is conveyed to
an earthen holding lagoon providing a 12-hour retention of the coal
mine water.  The holding lagoon design is based upon a 2-foot freeboard
and 1:1 sidewall slope with riprap on the upper sidewalls.  To permit
monitoring and sampling of the holding basin overflow, an open concrete
flume connects between the holding basin and reactor tank.  The pul-
verized limestone and recirculated sludge is added in the reactor tank
and is mixed with the coal mine drainage for a period of 60 minutes.
Reinforced concrete reactor tanks eliminate the erosion problems of
earthen basins caused by mixing action.  The reactor tanks are built
with vertical walls and a ^-foot freeboard.

Effluent from the reactor tank flows to the aeration tank where mixing,
aeration and sparging of carbon dioxide are accomplished by mechanical
surface aerators.  The aeration tanks are sized for a 60-minute deten-
tion period, for the total flow rate to the unit.  The aeration tanks
are constructed of reinforced concrete.  The aerators are mechanical
surface aeration units which ensure continuous mixing.  The aerator
is secured with guy wires or supported by structural steel members
spanning the tank walls.

The aeration tank effluent flows into the settling basin, providing a
12-hour detention period based upon the flow rate to the settling
basin.  The settling basin is provided with an influent distribution
trough and weir and designed to minimize the possibility of short
circuiting.  The earthen basins are constructed of well-compacted clay-
type soil to reduce leakage.  In addition, the earthen settling basins
are constructed with a minimum of 2 feet freeboard, a minimum inside
wall slope of 2:1 and riprap on the upper sidewalls to prevent erosion
by the surface wave action.  An open channel as the treated water enters
the receiving stream, permits visual observation and continuous pH
monitoring of the effluent.  The sludge from the settling basins is
pumped from the settling basin to the sludge pump well.

The sludge removal system has been designed to use portable floating sur-
face pumps secured to the basin crest by guy wires.  Recirculated sludge
is pumped at a rate equal to the plant influent to the reactor tank.  The
remainder of the settled solids is pumped by the waste sludge pumps to
the earthen sludge dewatering basins for additional concentration and
disposal.  All pumping systems include a standby pumping unit to be used
during maintenance or breakdown of an operating pump.
                                  125

-------
The construction costs for the sludge de-watering facilities are based on
the assumption that the basins can be located adjacent to the treatment
complex and do not reflect the costs of pumping sludge through a long
pipeline.  The supernatant from the dewatering basin is discharged to
the receiving stream.  A concrete sump with pumps and appurtenances to
pump the concentrated sludge from the dewatering basin provides a means
for transfer of the sludge to tank trucks for ultimate disposal.  The
dewatering basins have the capacity to hold a 3-month sludge accumula-
tion.

The design of the limestone treatment process units is based on single
unit operation and does not reflect the capital costs if duplicate
units are required.

Bulk storage of pulverized limestone is provided at the plant site to
provide a minimum of h days storage.  It is assumed that the limestone
would be delivered to the plant site by pneumatic unloading trucks.
The limestone storage bins are equipped with level indicators, lime-
stone feeders, and dust collectors.  The limestone feeders are installed
in duplicate to reduce the possibility of plant shutdown due to mechan-
ical equipment failure and to permit routine maintenance on the equip-
ment.  This equipment should be located near the reactor tank to reduce
the distance required to convey the limestone.  A control building is
required at the plant site to house the plant services, administration
facilities, and chemical feed systems.  The plant services and adminis-
tration section of the control building should contain (a) an office
for the plant operator; (b) a central control panel from which the
treatment plant operations would be monitored; (c) laboratory facilities
for water quality analysis and chemical dosage controls; (d) main motor
control center, and (e) maintenance shop.  The chemical feed equipment
section of the control building contains the limestone and coagulant
aid feed equipment.

A paved access roadway should be constructed to the plant site to
ensure delivery of the chemicals to the plant during all weather
conditions.

The operation and control of the proposed coal mine drainage treatment
complex is based upon the coal mine water flow rate and acidity con-
centration of the specific discharge to be treated.  The holding
basin effluent flow should be continuously and automatically metered.
Acidity concentration at this point in the process must be manually
sampled and analyzed to determine the quality of limestone feed.  In
addition, the pH should be continuously and automatically monitored
by pH probes located between the aeration tank and settling basin and
in the treated water discharge channel.  The recirculated sludge flow
should be automatically regulated by the plant influent flow rate at
the ratio of 1:1.

Tables lj-2 through ^5 inclusive are breakdowns of the capital costs for
construction of treatment plants for the flow rates and cases of water
                                  126

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                                                       TABLE  42
                                        ESTIMATE OF  CAPITAL COST FOR  LIMESTONE
                                               TREATMENT  PLANT TO  TREAT
                                    CLASS  I  COAL MINE DRAINAGE 0.1 MGD FLOW RATE

                                                       CASE A*             CASE B*              CASE C*

          1.   SITE  PREPARATION
               a.   Clearing & Grubbing               $     300.00         $    400.00          $     500.00
          2.   STRUCTURES
               a.   Holding Lagoon                      3,750.00            3,750.00             3,750.00
               b.   Reactor Tank                        3,300.00            3,300.00             3,300.00
               c.   Aeration Tank                       3,300.00            3,300.00             3,300.00
               d.   Settling Basin                      7,860.00            9,790.00            10,500,00
               e.   Sludge Dewatering Basin             8,400.00           38,850.00          105,000.00
               f.   Sludge Pump Well                    3,000.00            4,250.00             5,500.00
H         3-   CONTROL BUILDING                         30,000.00           30,000,00            30,000.00
1^         b.   MECHANICAL EQUIPMENT
               a.   Mixers                              2,625.00            2,625.00             2,625.00
               b.   Aerators                             3,750.00            3,750.00             7,500.00
               c.   Sludge Recirculation Pumps           3,900.00            3,900.00             3,900.00
               d.   Waste Sludge Pumps                  1,950.00            1,950.00             1,950.00
               e.   Settling Basin Sludge Pumps          4,550.00            4,550.00             4,550.00
          5.   CHEMICAL FEED EQUIPMENT                  3,500.00            6,000.00            10,900.00
          6.   MECHANICAL PIPING                        12,000.00           13,000.00            15,000„00
          7.   CONTROL EQUIPMENT                        5,000.00            5,000.00             5,000.00
          8.   ACCESS ROADWAY                            2,500.00            2,500.00             2,500.00
          9.   FINAL GRADING                             2,000.00            2,000.00             2,000.00
         10.   ELECTRICAL                               10,000.00           10,500.00            11,000.00
         11.   CONTINGENCIES                             11,090.00           l4,4l5,00            22,735.00
         12.   ENGINEERING                              7,500.00            9,420.00            15,060.00

              TOTAL CAPITAL COSTS                   $130,275-00         $173,250.00         $266,570.00


         * See page 106 for  description.

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                                             TABLE 43
                              ESTIMATE OF CAPITAL COST FOR LIMESTONE
                                     TREATMENT PLANT TO TREAT
                          CLASS I COAL mm DRAINAGE AT 1.0 MGD FLOW RATE





H
ro
00





3-
4.
b
c
d
e
f
CO!
ME(
 5.
 6.
 7.
 8.
 9-
10.
11.
12.
SITE PREPARATION
  a.  Clearing & Grubbing
STRUCTURES
  a.  Holding Lagoon
     Reactor Tank
     Aeration Tank
     Settling Basin
     Sludge Dewatering Basin
     Sludge Pump Well
CONTROL BUILDING
MECHANICAL EQUIPMENT
  a.  Mixers
     Aerators
     Sludge Recirculation Pumps
     Waste Sludge Pumps
     Settling Basin Sludge Pumps
CHEMICAL FEED EQUIPMENT
MECHANICAL PIPING
CONTROL EQUIPMENT
ACCESS ROADWAY
FINAL GRADING
ELECTRICAL
CONTINGENCIES
ENGINEERING

TOTAL CAPITAL COSTS
      b.
      c.
      d.
      e.
                                              CASE A*
$    750.00

  20,900.00
  16,500.00
  15,750.00
  45,250.00
  47,750.00
   5,500.00
  48,000.00

   9,750.00
  12,750.00
   4,250.00
   1,950.00
   4,850.00
  10,500.00
  25,000.00
  12,000.00
   2,500.00
   4,000.00
  15,000.00
  29,790.00
  19,260.00

$352,000.00
                                                             CASE B*
$    825.00

  20,900.00
  16,500.00
  15,750.00
  49,800.00
 380,000.00
   6,300.00
  48,000.00

   9,750.00
  15,750.00
   4,250.00
   2,550.00
   6,000.00
  26,000.00
  27,500.00
  12,000.00
   2,500.00
   4,000.00
  16,000.00
  60,395.00
  39,960.00

$764,730.00
                                           CASE C *
                                                                                           920.00

                                                                                        20,900.00
                                                                                        16,500.00
    _1_W • ^/\J\S •
    15,750.00
    57,000.00
   790,000.00
     7,500.00
    48,000.00

     9,750.00
    18,000.00
     4,250.00
     3,000.00
     6,850.00
    44,500.00
    29,000.00
    12,000.00
     2,500.00
     4,000.00
    17,000.00
    78,180.00
    52,560.00

$1,238,160.00
  See page 106 for description.

-------
                                                      TABLE 44
                                       ESTIMATE OP CAPITAL COST FOR LIMESTONE
                                              TREATMENT PLANT TO TREAT
                                   CLASS I COAL MINE DRAINAGE AT 7.0 MGD FLOW RATE
ro
 1.   SITE PREPARATION
      a.   Clearing & Grubbing
 2o   STRUCTURES
      a.   Holding Lagoon
      b.   Reactor Tank
      c.   Aeration Tank
      d.   Settling Basin
      e.   Sludge Dewatering Basin
      f.   Sludge Pump Well
 3.   CONTROL BUILDING
 4.   MECHANICAL EQUIPMENT
      a.   Mixers
      b.   Aerators
      c.   Sludge Recirculation Pumps
      d.   Waste Sludge Pumps
      e.   Settling Basin Sludge Pumps
 5.   CHEMICAL FEED EQUIPMENT
 6»   MECHANICAL PIPING
 7.   CONTROL EQUIPMENT
 8.   ACCESS ROADWAY
 9.   FINAL GRADING
10.   ELECTRICAL
11.   CONTINGENCIES
12.   ENGINEERING


     TOTAL CAPITAL COSTS
                                                       CASE A*
$    1,200.00

   115,500.00
    65,900.00
    87,900.00
   256,000.00
   230,000.00
    16,500.00
    64,000.00

    63,000.00
    59,000.00
    19,750.00
     3,900.00
    20,750.00
    25,500.00
    58,000.00
    35,000.00
     2,500.00
     9,250.00
    36,000.00
   115,350.00
    76.200.00

$1,361,200.00
                                                                     CASE B*
$    1,500.00

   115,500.00
    65,900.00
    87,900.00
   290,000.00
 2,260,000.00
    18,750.00
    64,000.00

    63,000.00
   150,000.00
    19,750.00
     8,250.00
    22,800.00
   132,500.00
    64,000.00
    35,000.00
     2,500.00
     9,500.00
    37,500.00
   269,900.00
   117.900.00

$3,896,150.00
                                               CASE C*
$    1,800.00

   115,500.00
    65,900.00
    87,900.00
   350,000.00
 5,250,000.00
    20,000.00
    64,000.00

    63,000.00
   225,000.00
    19,750.00
    13,900.00
    26,400.00
   24-7,500.00
    70,000.00
    35,000.00
     2,500.00
    10,000.00
    40,000.00
   452,710.00
   298,920.00

$7,459,780.00
          See page 106 for description.

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TABLE k5.  ESTIMATE OF CAPITAL COST FOR LIMESTONE TREATMENT PLANT
             TO TREAT SOUTH GREENSBURG COAL MINE DRAINAGE
                      AT U.O MGD FLOW RATE
 1.  SITE PREPARATION
     a.  Clearing & Grubbing

 2.  STRUCTURES
     a.  Holding Lagoon
     b.  Reactor Tank
     c.  Aeration Tank
     d.  Settling Basin
     e.  Sludge Dewatering Basin
     f.  Sludge Pump Well

 3.  CONTROL BUILDING

 U.  MECHANICAL EQUIPMENT
     a.  Mixers
     b.  Aerators
     c.  Sludge Recirculation Pumps
     d.  Waste Sludge Pumps
     e.  Settling Basin Sludge Pumps

 5.  CHEMICAL FEED EQUIPMENT
 6.  MECHANICAL PIPING
 7.  CONTROL EQUIPMENT
 8.  ACCESS ROADWAY
 9.  FINAL GRADING
10.  ELECTRICAL
11.  CONTINGENCIES
12.  ENGINEERING
                                                        500.00
                                                     76,000.00
                                                     U3,200.00
                                                     1+3,200.00
                                                    118,500.00
                                                     35,000.00
                                                     12,000.00

                                                     ^8,000.00
                                                     25,500.00
                                                     31,000.00
                                                     11,250.00
                                                      1,950.00
                                                     11,250.00

                                                      6,000.00
                                                     Uo,ooo.oo
                                                     2*1,000.00
                                                      2,500.00
                                                      6,000.00
                                                     30,000.00
                                                     56,150.00
                                                     36,960.00
                               TOTAL CAPITAL COSTS  658,960.00
                              130

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        TABLE k6.  BASIS  FOR ESTIMATED COSTS OF LIMESTONE  TREATMENT
                 OF GOAL MINE DRAINAGE PRESENTED  IN TABLE k2,
                        TABLE 43,  TABLE 1+U, AND TABLE ^5


1.   CAPITAL COSTS
     The capital costs  are amortized for twenty (20) years at six (6) percent interest

2.   LABOR
       a.   0.1 MOD Treatment ELant:
              1 Operator          «i $ 7,500             =             $ 7,500.00
              1 Part Time Laborer  © $ 3,000             =               3,000.00
                                                                      $10,500.00
       b.   1.0 MGD Treatment Plant:
              1 Operator          ra $ 8,000             =             $ 8,000.00
              1 Laborer           
-------
H
U)
                        TABLE  47.   ESTIMATED COSTS OF LIMESTONE TREATMENT OF WQO, EPA CLASS I
                                CASE A COAL MINE DRAINAGE.* ALL COSTS  REPORTED AS CENTS
                                          PER 1,000 GALLONS OF WATER TREATED

       Plant     Capital   Lator   Limestone   Coagulant   Power   Mainte-   Contin-   Sludge    Total   Accumulation
      Capacity    Cost                           Aid             nance &   gencies  Disposal   Costs   Of Sludge In
       (MGD)     	   	   	   	   	   Repairs   	    Cost     	  1 Yr.-Acre-Fb.
0.1
1.0
7.0
* See page

31.1
8.4
4.6
106 for

28.8
3.8
1.0
description,
TABLE 48.
CASE
5.8
5.8
5.0

1.7
1.7
1.7

6.9
1-9
2.0

8.0
1.4
0.3

3.6
1.0
0.5

11.4
11.3
11.4

97.3
35.3
26.5

1.3
12.8
89.7

ESTIMATED COSTS OF LIMESTONE TREATMENT OF WOjO, EPA CLASS I
B COAL MINE DRAINAGE.* ALL COSTS REPORTED AS CENTS
PER 1,000 GALLONS
Plant
Capacity
(MOD)
0.1
1.0
7.0
Capital
Cost
41.4
18.3
13.3
Labor Limestone
28.8
3.8
1.0
43.8
40.5
40.0
Coagulant
Aid
1.7
1.7
1.7
Power
6.9
2.9
2.7
OF WATER TREATED
Mainte-
nance &
Repairs
8.0
1.4
0.3
Contin-
gencies
4.7
2.0
1.5
Sludge
Disposal
Cost
118.7
118.9
118.5
Total
Costs
254.0
189.5
179.0
Accumulation
Of Sludge In
1 Yr.-Acre-Ft.
13.3
133.1
929.4
      '•• See page 106 for description.

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UJ
oo
                        TABLE k$.  ESTIMATED COSTS, OF LIMESTONE TREATMENT OF WQO, EPA CLASS I
                               CASE C COAL MINE DRAINAGE.*  ALL COSTS REPORTED  AS CENTS
                                           PER 1,000 GALLONS  OF WATER TREATED
Plant
Capacity
(MJD)
0.1
1.0
7.0
Capital
Cost
63.9"
29.6
25. U
Labor
28.8
3.8
1.0
Limestone
81.0
75.0
75.0
Coagulant
Aid
1.7
1.7
1.7
Power
8.1
3.8
3.6
Mainte-
nance &
Repairs
8.0
l.k
0.3
Contin-
gencies
7.3
3*
2.9
Sludge
Disposal
Cost
256.8
256.8
257.3
Total
Costs
^55.6
375-5
367.2
Accumulation
of Sludge In
1 Yr. -Acre -Ft.
28.7
287.8
2,011.9
      * See page 106 for description.
                        TABLE  50.   ESTIMATED COSTS OF LIMESTONE TREATMENT OF SOUTH GREENSBURG
                                   COAL MINE DRAINAGE.  ALL COSTS REPORTED AS CENTS
                                           PER 1,000 GALLONS OF WATER TREATED
       Plant    Capital
      Capacity   Cost
       (MGD)    	
      Labor   Limestone
                 Coagulant
                   Aid
                   Power   Mainte-
                          nance &
                   	   Repairs
                         Contin-   Sludge    Total    Accumulation
                         gencies  Disposal   Costs    of Sludge In
                         	     Cost            1 Yr.-Acre-Ft.
        U.O
3.9
1.2
1.1
1.7
2.3
0.5
2.5
13.6
                                                                            11.1

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                             TABLE 51.   COMPARISON OF COSTS FOR  TREATING  COAL MINE DRAINAGE
H
U)
 _ Source _
 This report:
    Case A, 0.1 mgd
            1.0  "
            7.0  "
    Case B, 0.1 mgd
            1.0  "
            7.0  "
    Case C, 0.1 mgd
            1.0  "
            7.0  "
    South Greensburg
            if-.O mgd
 Corsaro, et al (Ref. No.  l6)
            0.9 mgd
            2.7 mgd

 Calhoun (Ref. No. 17)
      ~ 200 gal/day
Wilmoth et al (Ref. No. 18)
            7.5 cfs
Johns -Manvllle (Ref. No.  19)
            1.5 mgd
Acidity,
mg/1
1,000
11
It
8,000
It
tf
15,000
II
II
190
1,^00
650
Chemical
Costs
Cents per
Cents per mg/1 acidity
1,000 gal 1,000,000 gal
5.8
5.8
5.0
IK). 5
Uo.o
25^.0
189.5
179-5
1.1
11.5
5.5
5.8
5.8
5.0
5.5
5.1
5.0
5.0
5.0
5.8
8.2
8.5
Total Costs,
Cents per
1,000 gal
97.3
35.3
26.5
189^5
179.0
^55.6
375-5
367.2
13.6
33.0
19.95
                                                    360
~ I
2.8
                                                                                     1.0
                                                    367
1.2
~ 6*
                               Not reported
                       15
                   * Includes only chemical cost, power, maintenance,  and labor.

-------
quality previously described.  A summary of the procedures used to
determine the plant operating costs presented in Tables k"J through 50
inclusive are listed in Table k6.

The costs presented in Tables U? through 50 have been summarized and
compared to other published costs (l6, 17, 18, 19) in Table 51.  As
indicated previously, waters of the quality of Case B and Case C of
the Class I discharge are the exception, and the high costs for treat-
ing these waters may not, in fact, have much meaning.

Corsaro et al (l6) treated a mine water containing approximately
1,^00 mg/1 of acidity and having a flow of 0.9 mgd with lime for a
total treatment cost of 33.0 cents per 1,000 gal.  This can be com-
pared with treatment of Case A  (1,000 rag/1) at 1.0 mgd with limestone,
for which the total cost for treatment was 35-3 cents per 1,000 gal
(See Table Vf).  These costs include 1.7 cents per 1,000 gal for coag-
ulant aid, and it is noted that no coagulant aid was used in the lime
treatment study.  In the same study (l6), chemical costs were higher
for treatment with lime than with limestone and ranged from 7-5 "to
9.k cents per mg/1 of acidity per 1,000,000 gallons for lime treatment
compared to 5-0 to 5-8 for limestone treatment from this study.

Calhoun (17) and Wilmoth and Hill (18) reported cost of limestone for
treating mine waters containing ferric iron of 2.8 and 1.0 cents per
mg/1 acidity per 1,000,000 gallons, respectively, as compared to 5.0
to 5.8 from this study.  Neither reported complete total costs.

A recent Johns-Manville study  (19) reports the lowest total cost for
treating mine water with limestone as 15 cents compared to 13-6 cents
reported here for treating the  South Greensburg water.

In summary, chemical costs and  total costs for the BCR limestone proc-
ess for treatment of coal mine  drainage, particularly the more-
difficult- to- treat drainages containing ferrous iron, compare favorably
to costs of treatment using  other neutralization processes.
                                   135

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                             SECTION VIII

                            ACKNOWLEDGMENTS
Work on this project was supervised by C. T. Ford, Project Scientist,
both R. K. Young and J. F. Boyer, Jr., who functioned as Principal
Investigator at different times, and R. A. Glenn, Project Director.

Technicians involved in the conduct of the experimental  work were
J. R. Allender, D. A. Bowser, D. R. Wolber, and A. C. Rupert.

The assistance of Project Scientists R. C. Streeter in the continuous
flow studies, and R. R. Care in the spectrographic analyses, is  acknowl-
edged.

The helpful suggestions and comments from R. D. Hill, EPA Project Officer,
and Dr. D. R. Maneval, Director of Planning and Coal  Research for the
Department of Environmental Resources, Commonwealth of Pennsylvania, were
sincerely appreciated.
A significant objective of this project was to investigate practical  means
of abating mine drainage pollution.  Such research projects, intended to
assist in the prevention of water pollution by industry, are required by
Section 6b of the Water Pollution Control Act, as amended.  This project  of
EPA was conducted under the direction of the Pollution Control  Analysis
Section, Ernst P. Hall, Chief, Dr. James M. Shackelford, Project Manager,
Ronald D. Hill, Project Officer.

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                                SECTION IX

                                REFERENCES
 1.  Bituminous Coal Research, Inc., "Studies on limestone treatment of
     acid mine drainage" Water Pollution Control Res. Series DAST-33,
     1^010 EIZ, 01/70 Water Quality Office, Environmental Protection
     Agency, Washington, D. C. (1970).

 2.  "Acid mine drainage in Appalachia," Appalachian Regional Comm.,
     Washington, D. C.  (1969).

 3.  Maneval, D. R., "Mine drainage pollution abatement—theory and
     practice," Coal Mining Inst. Am. 8^th Annual Meet., Pittsburgh, Pa.,
     Dec. 10, 1970.  5 PP.

 k.  Hill, R. D. and Wilmoth, R. C., "Limestone treatment of acid mine
     drainage," SME Fall Meeting, St. Louis, Mo., Oct. 21-23, 1970.
     23 pp.

 5.  Mihok, E. A., Deul, M., Chamberlain, C. E., and Selmeczi, J. G.,
     "Mine water research:  the limestone neutralization process,"
     U.S. Bur- Mines, Rept. Invest. 7191 (1968).

 6.  Holland, C. T., "An experimental investigation of the treatment of
     acid mine water containing high concentration of ferrous iron with
     limestone," 3rd. Symp. Coal Mine Drainage Res. Preprint, Pittsburgh,
     Pa., 1970.  pp. 52-65.

 7-  Stumm, W. and Lee, G. F., "Oxygenation of ferrous iron," Ind. Eng.
     Chem. 53 (2), 1*6-6 (I96l).

 8.  Ford, C. T.,  "Selection of limestones as neutralizing agents for
     coal mine water,"  3rd Symp. Coal Mine Drainage Res. Preprints,
     Pittsburgh, Pa., 1970.  pp. 27-51.

 9.  Gill, J. M. and Tao, F. T., "Quantitation and gas chromotography,"
     in  "Disc," Bull. 2o4, Disc Instruments, Inc., Calif., 1968.  p. 7.

10.  "Technical evaluation, material balances, and cost evaluation of
     the limestone treatment of coal mine drainage containing ferrous
     iron," Gwin, Dobson & Foreman, Inc., Altoona, Pennsylvania pre-
     pared for Bituminous Coal Research, Inc., 1971-  33 PP-

11.  "Sewickley Creek area, Pennsylvania:  Monongahela River mine
     drainage remedial project," U.S. Dept. Interior, FWQA, June 1966.

12.  "Extent of coal mine drainage pollution, McMahon Creek watershed,
     Ohio," U.S. Dept. Interior, FWQA Ohio Basin Region, Work Document
     No. 3^5 June 1970.
                                    139

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13.  "Slippery Bock Creek mine drainage pollution statement project,
     Gwin Engineers, Inc., Kept, to Pa. Dept. Mines Miner. Ind.,
     Project No. SL-110 (1970).  163 pp.

1^.  "Chartiers Creek mine drainage pollution abatement project,"
     Ackenheil &Assoc., Inc., Phase III Rept. to Pa. Dept. Mines
     Miner. Ind. (l9?0).  272 pp.

15.  Halliburton Company, "Investigative mine survey of a small
     watershed," Water Pollution Control Res. Series, I^JOIO DM0,
     03/70-A, U.S. Dept. Interior, Federal Water Quality Adminis-
     tration, Washington, D. C. (1970).

16.  Corsaro, J. L., Holland, C. T., and Ladish, D. J., "Factors in
     the design of an acid mine drainage treatment plant," 2nd Symp.
     Coal Mine Drainage Res. Preprints, Pittsburgh, Pa., 1968.
     pp. 27^-290.

17.  Calhoun, F. P., "Treatment of mine drainage with limestone,"
     2nd Symp. Coal Mine Drainage Res. Preprints, Pittsburgh, Pa.,
     1968.  pp. 386-391.

18.  Wilmoth, R. C. and Hill, R. D., "Neutralization of high ferric
     iron acid mine drainage," Water Pollution Control Res. Series,
     11*010 ETV, 08/70, U.S. Dept. Interior, Federal Water Quality
     Administration, Washington, D. C. (1970).

19.  Johns-Manville Products Corp., "Rotary precoat filtration of
     sludge from acid mine drainage neutralization," Water Pollution
     Control Res. Series, lij-010 DII, 05/71, Environmental Protection
     Agency, Water Quality Office, Washington, D. C. (1971).

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1
Access/on Number
w
5
« Subject Field & Group
05D
SELECTED WATER RESOURCES ABSTRACTS
INPUT TRANSACTION FORM
Organization
                Bituminous Coal Research,  Inc.   (Contractor)
     Title
                Studies on Limestone Treatment  of Acid Mine  Drainage.   Part II
 10
    Authoifs)

      Ford, C. T.
      Boyer, J. F.
      Glenn, R. A.
 I f. I Project Designation

	'       EPA Grant No. lUOlO EIZ
                                     2]  Note
 22
     Citation
                Water Pollution Control Research  Series
                Publication Wo. 1^010 EIZ  10/71
                Environmental Protection Agency,  Office  of Research and Monitoring
 23
     Descriptors (Starred First)
                *Acid Mine Water, ^Neutralization,  ^Limestones,  *Water Pollution Treatment,
                Iron Compounds, Oxidation,  Sludge
 25
     Identifiers (Starred First)
                *Iron Removal, Slurry Recirculation,  Sludge  Properties
 27
     Abstract
            Laboratory  studies  were conducted with limestone as the neutralizing agent
     for coal mine water.   Batch tests were used to determine the properties of limestone
necessary for effective neutralization.  Continuous flow tests were used to determine
conditions required  for an effective neutralization process.

     The following variables are of importance for limestone to be an effective neutraliz-
ing agent:  (a) particle size,  (b)  Ca and Mg content, and (c) surface area.  Limestones
having the smallest  particle size commercially available were tested and found to be
effective if criteria for variables other than particle size were met.

     Data obtained with a small laboratory continuous flow test apparatus were used in
determining operating conditions for a continuous treatment process for neutralizing mine
water with limestone.   An evaluation of this process indicated technical feasibility,
advantages and disadvantages, and need for further study of certain aspects of this
process.

     The cost of treating coal  mine water with the BCR limestone treatment process compares
favorably with the published costs  of treating mine water by other processes.
(Ford - Bituminous Coal Research, Inc.)
Abstractor
          C. T. Ford
                               IriNtitution
                                       Bituminous Coal Research,  Inc.
 WR:1D2 (REV. JUUY 1969)
 WRSI C
                             SEND. WITH COPY OF DOCUMEN1
                                                    TO: WATER RESOURCES SCIENTIFIC INFORMATION CENTER
                                                       U.S. DEPARTMENT OF THE INTERIOR
                                                       WASHINGT ON, D. C. 20240
                                                                              GPO: 1970 - 407 -891

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