WATER POLLUTION CONTROL RESEARCH SERIES  12O4O EZZ O4/7O
  Dilute Spent  Kraft Liquor Filtration
    through Wood Chips
13.S DEPARTMENT OF THE INTERIOR  FEDERAL WATER POLLUTION CONTROL ADMINISTRATION

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     DILUTE SR&rf^**ABTRER)UOR FILTRATION

              THROUGH WOOD CHIPS
FEDERAL WATER POLLUTION CONTROL ADMINISTRATION

          DEPARTMENT OF THE INTERIOR
                      By
     Department of Wood and Paper Science
          School of Forest Resources
        North Carolina State University
                   Box 5*88
         Raleigh, North Carolina 27607
              Program #120^0 EUG
             Grant #WPRD 115-01-68
                  April 1970

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         FWPCA Review Notice
This report has been reviewed by the
Federal Water Pollution Control Admin-
istration and approved for publication,
Approval does not signify that the
contents necessarily reflect the views
and policies of the Federal  Water Pol-
lution Control Administration.

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                                ABSTRACT


The principal objective of this project was to determine if contact
between effluent from a Kraft pulp mill and pine chips  would reduce
the water pollution characteristics of the waste liquor.

The experimental work was divided into two phases:   1)  a small  scale
laboratory investigation of contacting dilute waste liquor with chips;
2) a pilot-scale investigation of filtering waste liquor through a
column and a pile of chips.
It was found that contact of alkaline waste liquor,  or even distilled
water, with pine chips extracted organic matter from the chips  which
had a considerable BOD^.   This extract corresponded  to a pollution load
of about 3~11  Ibs. 6005 per ton of dry wood.   Alkalinity, pH,  and inten-
sity of color of the waste liquor were somewhat reduced by the contact.
These reductions are, however, too small to have any practical  appli-
cation in  effluent treatment.  It can, in general,  be concluded that
contact of alkaline waste liquor, or water, with wood chips extracts
soluble organics and adds pollutional materials to the effluent stream.

This report was submitted in fulfillment of Grant No. 115-01-68 between
the Federal Water Pollution Control Administration and the Department
of Wood and Paper Science, School of Forest Resources, North Carolina
State University at Raleigh, North Carolina.
Key Words:  Water pollution, waste water, BOD-extraction, Kraft pulp
            mi 11, wood ch ips.
                                 i i i

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                        TABLE OF CONTENTS

                                                                Page No.

Abstract	      i i i

List of Figures	      vi i

List of Tables	       ix

   I.   CONCLUSION	        ]

  II.   RECOMMENDATION	        3

 III.   INTRODUCTION	        5

  IV.   EXPERIMENTAL	        7

       A.   Analytical Procedures 	        7
       B.   Laboratory Experiments	        7
       C.   Pilot-Scale Experiments at Mill Site	        8
   V.  DISCUSSION OF RESULTS
       A.  Laboratory Experiments  Treatment of Diluted Spent
             Kraft Pulping Liquor from the Decker Effluent
             by Contact with Pine Chips	      11
       B.  Pilot-Scale Treatment of Diluted Spent Kraft Pulping
             Liquor (Effluent) by Contacting It with Pine Chips.     16
       C.  Practical Aspects 	      20

Acknowledgment 	      29

References	      31

Appendix	      33

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                              FIGURES
Figure
                                             Page No.
        Change in  biochemical  oxygen  demand  (BOD) of  a waste
          Kraft pulping liquor of pH  10,  resulting  from
          filtering the liquor through  a  column  of  pine
          chips	

        Change in  biochemical  oxygen  demand  (BOD) of  a waste
          Kraft pulping liquor of pH  10.5 resulting from
          filtering the liquor through  a  column  of  pine
          chips	
                                                21
        Reduction
          initial
          through

        Reduct ion
          initial
          through
in pH of a waste Kraft pulping liquor of
pH 10, resulting from filtering the liquor
a column of pine chips 	
                                                22
23
in pH of a waste Kraft pulping liquor of
pH 10.5 resulting from filtering the liquor
a column of pine chips 	
                                 VI I

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                              TABLES

Table                                                          Page  No.

  1.   Properties of a waste liquor from a Kraft pulp mill
         after stirring contact at 25C with different amounts
         of pine chips	     12

  2.   Properties of waste liquors from a Kraft  pulp  mill
         after stirring contact at 25C with different amounts
         of pine chips	     13

  3-   Analytical data for waste Kraft pulping liquor and  dis-
         tilled water after stirring separately  with  pine  chips
         for 1 hour at 25C	     \k

  k.   Analytical data for waste Kraft pulping liquor and  dis-
         tilled water after stirring contact separately with
         pine chips for 1  hour at 75C	     15

  5-   Analytical data for waste Kraft pulping liquor stirring
         treatments for 1  hour at 25C with original  pine  chips,
         and with the previously treated chips	     17

  6.   Properties of waste Kraft-pulping liquor  resulting  from
         recycling of the  liquor through pine chips in an  open
         column  (laboratory experiments) 	     18

  7.   Properties of waste Kraft pulping liquor  before and after
         gravity flow of the liquor through a column  of pine
         chips (preliminary mill pilot-scale experiments).  ...   19

  8.  Change in biochemical oxygen demand of waste Kraft pulping
         liquor of pH 10-10.5 resulting from filtering the
         liquor through a  column of the pine chips	25

  9.   Changes in properties of waste Kraft pulping liquor by
         contacting the liquor with pine chips through spraying
         the liquor over a small chip pile (pilot-scale experi-
         ments) 	     26
                                  i x

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           Dilute Spent Kraft Liquor F i 1 ^ration

                    Th rough Wood Ch i ps
CONCLUSION

Contact between pine chips and dilute alkaline effluent from a Kraft
pulp mill extracted a considerable amount of biochemical  oxygen de-
manding matter from the chips.  The pH,  electrical  conductivity, as
well as the alkalinity of the waste liquor were somewhat reduced by
contact with the chips.  The  intensity of color of the waste liquor
diminished.  It is believed that the change in color is caused
mainly by the reduction in pH.  The pine chips acted as a good filter-
media for the waste liquor.  Fibers present in the waste liquor were
almost quantitatively removed by filtering the liquor through a
chip column or chip-pile.  However, the fibers retained on the sur-
face of the chip-column, or pile, hindered penetration of the liquor
through the chips.

It can, in general, be concluded that contact of waste liquor from
a Kraft pulp mill  with wood chips would extract enough BOD from the
chips to increase the pollution load of the effluent.  Even water
extracted a considerable amount of BOD from wood chips.  This means
that liquid drainage from a mill's chip storage area should be con-
sidered as a pollutional waste.  The change in pH, alkalinity, and
the color reduction obtained by contacting waste liquor with wood
chips were too small to achieve practical benefits through industrial
application of the system.

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I I.   RECOMMENDATION

     It  is  recommended  that  contact  between  pulp  and  paper  mill  alkaline
     effluent  and wood  chips  should  be  avoided  and  that  drainage,  result-
     ing from  rainfall  and other water  sources,  from  a wood chip storage
     area should  be  considered  a pollutional waste.

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III.   INTRODUCTION
      The  prime objective of  this  project was  to  determine  if contact
      between waste  liquor  from  a  Kraft  pulp mill,  that produces un-
      bleached pulps  from southern  pine, and the  wood  chips  from which
      the  pulp is  subsequently made,  reduces the  water polluting pro-
      perties of  the  waste  liquor.  The  suggestion  was based  in the
      fact that wood  sawdust, or chips,  will absorb alkali  from water
      to reduce  its  pH,  and that wood  and cellulose are good  adsorbents
      for  phenols  and tannins.   The experimental  work  was divided  into
      two  phases.  The first  of  these  was a  laboratory investigation
      to determine changes  in  the  water  polluting characteristics  of
      the  waste  liquor after  contact with pine  chips.  The  second  phase
      involved pilot-scale  investigations by filtering waste  Kraft
      pulping  liquor through  pine  chips  at  the  plant site of  the co-
      operating  company, Albemarle Paper Corporation at Roanoke Rapids,
      North Carolina.

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IV.   EXPERIMENTAL

     A.   Analytical  Procedures

         Standard analytical procedures  (1) were used for  testing  the  pol-
         lution  characteristics of the liquors.  These were  applied  in  the
         laboratory  and pilot-scale experiments.

           jp_H_was measured with a calibrated Beckman pH meter.

           Bjochemjca I_oxy3_en_ demarid_(j3prjr)_ was determined  according  to  the
           "me~thl>d described in the 12th edition of "Standard Methods  for
           the Examination of Water and Waste Water"  (1).   The  seeding  used
           was domestic sewage taken from  Raleigh City sewage treatment
           plant.  The dissolved oxygen content was measured with  polaro-
           graphic DO-Analyzer (Wes ton and Stack, Inc., Model  300) after
           calibrating the  instrument with solutions which  had  been  analyzed
           according to the Winkler-Method (1).

           Tp.La.L Alj
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    or any other evidence of degradation.  The waste liquor used for
    the experiments was effluent from the mill's decker-operation,
    which increases the consistency of the pulp after the low consis-
    tency screening operation.  In this mill  the decker-operation also
    acts as a final washing stage.  It was found that if the waste
    liquor was kept in closed polyethylene carboys of 5 gallons at
    ^C, it could be stored for one to two months without any change
    in pH or BOD.  In the laboratory tests BOD analyses were completed
    in the test waste liquor, prior to use, after storage periods not
    exceeding 3 weeks.

    Small scale experiments were performed by the mechanical stirring
    of 100 to AOO grams of wet chips,  with a moisture content of 50%,
    in a three liter beaker containing one liter of waste liquor or
    water.   The tests were made at room temperature (about 25) and
    at an elevated temperature of 75C.  In the control  experiments
    no chips were added.   Samples  of the liquors were taken before
    and after the treatments.  The pollutional  characteristics of
    the samples were determined following filtration of the sampled
    liquors through filter paper.   The experiment was designed to
    reflect realistic ratios of chips  used to waste liquor discharged
    by a mill.  The total  waste liquor from a Kraft mill  amounts to
    about 1-2 gallons per pound of dry chips  used.   In the metric
    system this would be  60-120 grams  of dry  chips  per liter.

    A few experiments were made utilizing a glass column  packed with
    chips.   The dimension of the column was 1.5 inches in diameter
    and about 36 inches in length.   The column contained  500 grams
    of chips with a moisture content of about 50%.   This  quantity of
    chips filled the column to a depth of about 30 inches.   In each
    test 1500 ml of the waste liquor was recirculated through the
    column  by a constant  volume pump delivering about 500 ml/min.
    The time of treatment was varied.   Liquor samples were taken at
    different time intervals and analyzed for pH, BOD,, and suspended
    solids.                                           '

C.   Pilot-Scale Experiments at Mill  Site

    Preliminary experiments were made  by filtering  effluents from
    the mill's decker operation through a pine chip column.   This
    was contained in  a 55 gallon steel  drum.   The weight  of the chips
    was 1^*3 Ibs.  on a wet weight-basis, or about 70 Ibs.  as  oven-
    dried chips.   The effluent  was  distributed over the  top of the
    chip column by utilizing four  paper machine headbox showers which
    distributed the effluent in a  relatively  uniform manner.  The

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four overlapping sprays covered 90% of the area on the  top of
the column.  The flow rate of the effluent was  kept at  5 and
3 gal/min.  Samples of the effluent, before and after contact
with the chips, were taken at different time intervals.

Additional experiments employing a longer column were completed.
This column was constructed from 55 gallon drums which  were
welded together endwise.   For one experiment a  10 ft. depth of
chips was employed using  575 Ibs. of chips.  For the second
experiment a 6 ft. depth  of chips was used employing 3^0 Ibs.
of chips.  The chip moisture content in both instances  approxi-
mated 50%.  The flow rate of the decker effluent through the
column was kept at 1.5 and 2 gal/min. and the liquor was dis-
tributed on the top of the column by the four overlapping sprays.
A piece of Fourdrinier wire was placed over the top of the col-
umn in order to filter out the fibers present in the waste liquor
and to prevent plugging of the chip column with fibers.  Samples
of the liquor were taken  before and after contact with  the chips
at different time intervals and analyzed for pH and BOD_.

A small experimental chip pile was also constructed which was
12 feet  in diameter at the base, 4 feet in diameter at the top
and 6 feet high.  The pile contained about A.5 tons of wet pine
chips (kkOO Ibs. of oven-dried chips).  The chip pile was placed
on a 3 mil. polyethylene  sheet and arranged  in such a way that
all the effluent would drain to one point for sampling of the
liquor.   Effluent from the mill's decker operation was sprayed
on the top of  the pile, utilizing the same spray arrangement as
for the column experiments.  The flow rate was  12 gal/min.  The
first chip pile constructed was essentially washed away after
one week.  A second pile  equal to the first one was therefore
constructed with  the base of the pile restrained by a foundation
of 1" x 5" boards.  Samples of liquor were taken at various time
intervals before  and after contact with the chips and analyzed
for pH and BOD_.

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V.   DISCUSSION OF RESULTS

    A.   Laboratory Experiments  Treatment  of  Diluted  Spent  Kraft
        Pulping Liquor from the Decker  Effluent  by  Contact  with Pine
        Chips

        a)  Stirring tests  in beaker.  Table  1  shows  the  results of
        the tests.  As the  liquor  changed  on  exposure to  air,  the
        analysis of a liquor, which was  stirred  without  chip  contact
        for the same period of time as  the other test liquors,  are
        included.  The most notable changes  in the  characteristics
        of the waste liquor by contact  with  the  chips were  a  decrease
        in pH, an increase  in the  content  of  the volatile matter
        (organics), and an  increase  in  the biochemical oxygen  demand
        (6005).  The amount of inorganic matter  was  not  significantly
        changed.  The electrical  conductivity decreased,  as expected
        from the pH-reduction,  as  a  result of the treatment.   Contact
        of liquor with the  chips  reduced the  intensity of the color
        of the waste liquor but increased  its colloidal  nature.  The
        change in color could be caused by the change in  pH.   It  is
        well  known that the color  of  spent Kraft pulping  liquor is
        highly dependent on pH. Although  a  noticeable color  change
        of the effluent occurred,  it  was not  possible to  quantitatively
        measure the degree  of change  because  the residual color was
        still too intense  to measure  accurately.

        Analytical data for stirring  experiments at 25C  performed
        on 100 and 200 grams of wet chips, with  two new  samples of
        decker effluent, are given in Table  2.  The results verified
        the findings of the former experiments.   Organic  matter was
        extracted from the chips  by  the waste liquor. The  BOD-
        demand of  the liquor was  thereby considerably increased and
        the pH and the alkalinity  of  the liquor  was significantly
        reduced.  This was  obviously  a  result of neutralization of
        the liquor by the extracted wood-acids.   The data showed
        also that the BOD of the waste  liquor was reduced by  contact
        with the air.  This was probably caused  by  air-oxidation
        of sulfides in the waste liquor to their respective oxidation
        products.

        Tables 3 and 4 show the results obtained by contacting pine
        chips with waste liquor and with distilled  water by stirring
        at about 25C and at 75C.

        The findings confirmed earlier results and  showed also, that
        even distilled water extracts biochemical oxygen  demanding
        materials from wood chips.  At room temperature  (about 25C)
                              11

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Table 1.  Properties of a waste liquor from a  Kraft  pulp mill  after  stirring contact at 25C with
          different amounts of pine chips
Chi p-Liquor
Ratio
(g. chips/
1 i ter 1 iquor)
0


50


100


200


Time
of
Sti rring
(hours)

1
k
0
1
k
0
1
k
0
1
4

pH
8.8
8.8
8.7
8.8
7.5
6.9
8.8
7.0
6.6
8.8
6.9
6.5

Electrical
Conduct i vi ty
(mho/cm')


450


410


370


350

Vo 1 a t i 1 e
Matter
(g/li ter)


0.36


0.56


0.99


1.14

1 norgani c
Matter
(g/li ter)


0.15


0.18


0.14


0.19
Five day
Biochemi cal
Oxygen Demand
(ppm)


225


315


330


310

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Table 2.   Properties of waste liquors from
          different amounts  of pine chips
a Kraft pulp mill  after  stirring  contact at 25C with


Waste
1 iquor
Sample
1

Sample
1 1



Chip-Liquor Ratio
(g. dry chips/
1 i ter of 1 iquor)
0
50
100
0
0
50
100
Time
of
St i rring
(hours)
4
k
k
0
k
k
k



PH
9-0
7.9
7.7
10.8
10. k
9.3
8.0

Alkal inity
(mg/1 i ter)
(CaC03)
456
381
374
717
700
600
535

Dissolved
sol ids
(g/liter)
0.7
	
0.9
1.4
1.3
1.5
1.7

1 norgan i c
Matter
(g/liter)
0.21
0.23
0.26
0.39
	
0.36
	

B iochemi cal
Oxygen Demand
(ppm)
90
255
315
435
355
540
750
Change in
6 iochemi cal
Oxygen Demand
(ppm)
...
+ 165
+225

-100
+ 185
+395

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Table 3.  Analytical  data for waste Kraft pulping liquor and  distilled  water  after  stirring separately
          with pine chips for 1  hour at 25C


Type
of
Liquid
Waste
1 i q uo r
Waste 1 iquor
centri f uged"
Waste 1 iquor
Waste 1 iquor
centri f uged"
Water
Water
centri f uged"

Ch ip-Li quor
Ratio
(g.dry chips/
liter) pH

0 9.7

0
50 7.7

50
50 5- ^

50


Dissolved
Solids
(g/li ter)

1.2

1.1
1.6

1.5
0.3

0.2


1 norgani c
Matter
(g/1 i ter)

0.4

...
0.4

0.4
0.05

-0.06

Biochemi cal
Oxygen
Demand
(ppm)

250

250
410

415
75

90
Change in
Biochemi cal
Oxygen
Demand
(ppm)

	

...
+ 160

+ 165
+ 75

+ 90
Extracted
BOD5
from the Chips
(ibs.BOD/Ton
of Dry Chips




6.4


3.0


     'llltra-centrifuging was  performed after the treatments.

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Table 4.   Analytical  data for waste  Kraft  pulping  liquor  and  distilled water after stirring contact
          separately  with pine chips  for  1  hour  at 75C


Type
of
Liquid
Waste
1 iquor
Was te 1 iquor
centri f uged"
Waste
1 iquor
Waste 1 i quo 
centri f uged
Water
Water
centri f uged'

Chip-Liquor
Ratio
(g.dry chips/
liter) pH

0 9.5

0

50 7-6

50
50 6.0

50


Di ssol ved
Solids
(g/1 iter)

1.4

1.1

1.7

1.4
0.5

0.3


1 norgan i c
Matter
(g/1 iter)

0.5

0.4

0.5

0.4
0.04

0.03
Change in Extracted
Biochemical Biochemical BODr
Oxygen Oxygen from the Chips
Demand Demand (ibs.BOD/Ton
(ppm) (ppm) of Dry Chips)

300

280

400 +100 4

380
105 4

95 +100
     'Ultra-centrifuging was performed after the treatments

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    the amount of the extracted BOD^ was, after 1  hour's treatment,
    about twice as high for the alkaline waste liquor (pH 9-7) as for
    distilled water.  The amounts of BOD,- extracted from the chips
    were, on the basis of 1  ton of dry cnips, about 6.4 Ibs. and
    about 3-0 Ibs., respectively.  A one-hour stirring treatment at
    75C showed no difference in the amount of extracted BODc between
    water and the alkaline waste-liquor.  It amounted to about k Ibs.
    of BODr per ton of dry chips.  Removal  of colloidal  matter from
    the liquors by ultra-centrifugation did not significantly change
    the BODc of the liquors.  Two successive treatments  of pine chips
    with the alkaline waste  liquor at room temperature (about 25C)
    extracted a total  amount of BOD^ equal  to about 11.2 Ibs. per ton
    dry chips.   This can be  seen from Table 5-

    b) Recycling tests through chip column.   Results from recycling
    of waste liquor in a small column of pine chips are  given in
    Table 6.  The data showed that this treatment  gave generally the
    same pH reduction  as did the stirring experiments.  The chip
    column was  a very  effective  filter as it removed almost all  the
    fiber and the other suspended solids present  in the  waste liquor.
    The effect  on BOD of filtering the waste liquor through the chip
    column was  less apparent than shown by  the  stirring  experiments.
    This can be explained  by a more extensive air  oxidation of the
    waste liquor during the  recirculation treatment.

B.   Pilot-Scale Treatment  of Diluted Spent  Kraft  Pulping Liquor
     Effluent by Contacting  It with Pine Chips

    The preliminary experiments  of passing  effluent from a pulp
    decker operation through a column of chips  on  the plant site
    of Albemarle Paper Company in Roanoke Rapids,  North  Carolina,
    were inconclusive  with respect to changes in  pH and  BOD of the
    waste liquor.   The reason  for this  was  that the chip column
    became plugged with  fiber  rather quickly, and  the experiments
    had to be discontinued after  a very  short period of  time.   The
    pH and BOD  changes  of  the  effluent  on contact  with the  chips
    tend to  show,  however,  the same trends  that were observed in
    the laboratory.  The results  from the mill  experiments  are
    shown  in Table 7-

    Further  mill  experiments on  filtering effluent through  a column
    of chips, were performed with  columns of the same  diameter as
    used in  the  first  test,  but with  2.k times  as  many chips.   In
    these  tests  to overcome  the  problem of  fibers  clogging  the
    column,  the  1 iquor was first  filtered.   The flow rate of waste-
    liquor through  the  column  was  also  reduced.  The exact  experi-
    mental conditions  and  analytical  data for a set of duplicating

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Table 5-  Analytical data for waste Kraft pulping liquor stirring treatments for 1  hour at 25C
          with original pine chips, and with the previously treated chips





Biochemical


Treatment
St i rri ng
Sti rring



Chip-Liquor Ratio
(g. dry chips/1 i ter)
0
50
(origi nal
pine chips)
Dissolved
Sol ids
pH (q/liter)
9.5 0.9
7.7 1-3


Inorgan i c
Matter
(q/liter)
0.3
0.3


Oxygen
Demand
(ppm)
400
580


Chanqe in
Biochemical
Oxygen
Demand
(ppm)
	
+ 180


Extracted
BODj-
from the Ch


ips
(ibs.BOD/Ton
of Dry Chi

7.2


ps)




Sti rring
      50
(Previous ly  stir
 treated  chips)
8.0
1 .1
0.3
500
+100
k.O

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     Table 6.  Properties of waste Kraft-pulping liquor resulting from recycling of the liquor through
               pine chips in an open column (lab experiments)
oo


Temp.
(0
20



20



75






Chip-Liquor Ratio
(g.dry chips/liter)
0
170
170
170
0
170
170
170
0
170
170
170
170
Time of
Liquor
Cycle,
(mi n . )
0
3
3
3
0
3
3
3
0
3
3
3
3

Time of
Treatment,
(mi n. )
0
10
30
70
0
30
180
330
0
5
10
15
20



pH
10.3
9-5
8.8
7.6
10.3
8.8
7.1
7.1
9-2
8.2
7-7
7.5
7.5

Suspended
Solids
(mg/1)
350
	
	
5




_ _ 




Biochemical
Oxygen
Demand
(ppm)
350
	
	
375
290
270
290
310
260

	
	
205

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Table 7-   Properties of waste Kraft pulping liquor before and after gravity flow of the liquor
          through a column of pine chips (preliminary mill pilot-scale experiments)
Temp.
(O

30

30

Flow
Rate
(Gal/lbs.
Dry Chips/Hr.)
4.3
4.3
2.6
2.6
2.6
E lapsed
Time of
Effluent
Flow,
(mi n)
10
45
5
45
130
Total Amount
of Liquor
Contacted by
the Chips
(Gal/lb.
Dry Chips)
0.7
3.2
0.2
1.9
5.5
PH
Before
Contact
10.0
9-6
9.6
9-6
9.6
pH
After
Contact
9.5
9.4
9.0
9.3
9-5
A pH
0.5
0.2
0.6
0.3
0.1
BOD5
Before
Contact
(ppm)
375
310
330
395
370
BODr
After
Contact
(ppm)
320
410
460
395
410
A 6005
(ppm)
- 55
+ 100
+ 130
0
+ 40

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    experiments are given in Appendix Table 1  and the results are
    demonstrated in Figures 1-**.  It can be seen that biochemical
    oxygen demanding materials were extracted  from the chips by
    the alkaline liquor.  The bulk of this material  was leached
    out of the chips when 3"^ gallons of waste liquor, per pound
    of dry chips, had passed through the column.  The BOD-results
    obtained at the end of the second experiment (Fig. 2)  can be
    explained by channeling of liquor through  the column.   The
    reduction of pH of the waste liquor followed in general  the
    BOD changes (Figs. 3 and k) :  decreasing with time of  effluent
    flow until the reduction became constant at about 0.2  -  0.3 pH
    units.  This constant reduction in pH was  probably due to the
    absorption of carbon dioxide from the atmosphere.

    Table 8 shows the approximate increases in biochemical oxygen
    demand of the waste liquor by filtering it through the chip
    column, after different amounts of liquor  had passed through.
    The magnitude of the BOD increase corresponds with the BOD in-
    creases found in the laboratory stirring-experiments,  when the
    effect of air-oxidation of the liquor is taken into consideration.

    In order to investigate what happens when  a stored chip-pile is
    sprayed with the decker effluent for a long period of  time, two
    small experimental piles were built.  The  results from these
    spraying experiments are given in Table 9.  The piles  acted as
    a good filter medium for fibers and other  suspended matter in
    the waste liquor.   This resulted however,  in a partial  plugging
    of the surface of the piles  and therefore  limited contact of
    waste liquor with  the chips.   It can be concluded from the
    experiment that, after the bulk of soluble organics were ex-
    tracted from the chips, the changes in BODc were not very clear
    and were in most cases i ns ign i fi cant.   A biological  slime did
    form on the pile surface with time.   It is likely that  the pile
    acted partially as a biological  trickling  filter towards the
    end of the second  experiment.  The pH  reduction  was somewhat
    higher than would  be expected from the results  of the  previous
    experiments.

C.   Practical  Aspects

    Interest in spraying of stored chips with  water  or mill  effluent
    for wood preservation has  been growing since it  was  reported in
    the literature  (2)  that spraying of stored round-wood-piles with
    a  Kraft mill  effluent prevents  wood losses and  simultaneously
    reduces the BOD,- of the mill  effluent  60-65%.   Recently  pub-
    lished data (3)  shows, however,  that spraying of chips,  which
                             20

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300
                     150  200  250
                         TIME-min
                        i	i
300  350
400

	i
       0.55    1.25    1.95   2.65   3.35   4.05
            AMOUNT OF  LIQUOR CONTACTED BY
               THE CHIPS-gal/lb dry chips
            4.75
    Figure 1.  Change in biochemical oxygen demand (BOD) of a waste
            Kraft pulping liquor of pH 10,  resulting from filtering
            the liquor through a column of  pine chips
                       21

-------
           125
175 225 275  325
    TIME-min   ,
375  425 475
   0.55  1.25   1.95  2.65  3.35  4.05  4.75
     AMOUNT OF  LIQUOR CONTACTED  BY
         THE  CHIPS-gal/lb dry  chips
                           5.45
Figure 2.  Change  in biochemical oxygen demand (BOD)  of a waste
         Kraft pulping liquor of pH 10.5 resulting  from
         filtering the liquor through a column of pine
         ch i ps
                  22

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   1.2
o 0.8
I-
o
           ELAPSED
60             120
TIME OF  LIQUOR FLOW-min

 i                i
                                                    180
                    0.71             1.42            2.13
          AMOUNT OF LIQUOR  FILTERED  THROUGH
               THE CHIPS-gal/lb dry chips
      Figure J>.  Reduction in pH of a waste Kraft pulping liquor of
              initial pH 10, resulting from filtering the  liquor
              through a column of pine chips
                         23

-------
X
Q.
l.2r-
2 0.8
o
ID
  0.4
            	I	
                   60
            ELAPSED  TIME
            	I	
                         OF
  120
LIQUOR
	L_
        ISO
FLOW-mi n
	L_
                  0.71          1.42          2.13
         AMOUNT OF LIQUOR FILTERED  THROUGH
               THE  CHIPS-gal/lb dry chips
     Figure 4.  Reduction in pH of a waste Kraft pulping liquor
             of initial pH 10.5 resulting from filtering the
             liquor through a column of pine chips

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      Table 8.   Change In biochemical oxygen demand of waste Kraft pulping  liquor of pH  10-10.5  resulting
                from filtering the liquor through a column of the pine chips
vn
Elapsed Time
of
Experiment Effluent Flow
Number (Hours)
1
2
1 3
4
5
6.0
1
2
II 3
" 4
5
6
7
8
Total Amount of Liquor
Fi 1 tered Through
the Chips
(gal/lb. of dry chips)
0.71
1.42
2.13
2.84
3-55
4.25
0.71
1 .42
2.13
2.84
3-55
4.25
4.93
5.65
Increase in BODr
of the Total Waste Liquor
Passed Through the Chips,
(Ibs/ton dry chips)
2.4
3.7
4.5
5-0
5.4
5.6
2.0
2.8
3.2
3-5
3.8
4.20
4.80
5-50

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Table 9.  Changes in properties of waste Kraft pulping liquor by contacting the liquor with  pine
          chips through spraying the liquor over a small  chip pile (pilot-scale experiments)
Fow Rate
Temp.
(C)
30

IJ ;V
30*
1 1 !;
II ;';
II ...
11 .'.
(Gal
Dry Ch
0.
0.
0.
0.
0.
0.
0.
0.
/lb.
ips/Hr)
16
16
16
16
16
16
16
16
Elapsed Total Amount
Time of Liquor
of Contacted
Effluent by the Chips
Flow
(gal/lb.
(hrs) dry
0.
24
168
168
336
504
1176
1344
1

,one
Week)
/one
week)


(seven ,
weeks )
(eight 2
weeks)
ch i ps )
0.02
3-9
27-2
27.2
54.4
71.6
90.4
17.6
pH
Before
Contact
with the
Ch i ps
10.2
9.5
9.6
9-9
9.8
10.2
9-6

PH
After
Contact
wi th the
Chips
9-1
8.4
8.1
9-0
8.9
9.3
9-2



ApH
1.1
1.1
1.5
0.9
0.9
0.9
0.4

BOD5
Be f o re
Contact
with the
Ch ips
(ppm)
330
240
190
290
275
300
210
250
BOD5
After
Contact
with the
Chi ps
(ppm)
410
150
180
290
290
320
215
210
Changes
in
BOD5
(ppm)
+80
-90
-10
0
+ 15
+20
+ 5
-40
     "The chip pile surface became partially plugged with  fibers  and the flow of the liquor through
the chip pile was thereby considerably reduced.

-------
are stored for relative long periods  of time (1  year),  does  not
preserve the wood against degradation.   Spraying of chips  for  a
short time, j_.e_. , one month or less,  could,  according  to  the
literature source (3), offer an economic means  of wood  protection.
Our data show, however, that spraying of stored chips with  an
alkaline liquor may be a substantial  source  of  water pollution,
because organic materials with a 6005 of about  5~10 Ibs.  per
ton of dry chips  could be extracted from pine chips.  Even  water
extracted a considerable amount of biological oxygen-demanding
material from chips.  This means that liquor drainage  from a
chip storage area should be considered as a  pollutional waste,
and preferably should be treated in the mill's  waste treatment
plant.  The pH changes and color reduction of alkaline waste
liquor  by filtering  it through pine chips are too small  to
have any practical application in treatment  of waste water.
                         27

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                          ACKNOWLEDGMENT
We wish to thank Mr. F. W. Gladstone and his technical staff at
Albemarle Paper Company at Roanoke Rapids, North Carolina, for
supplying us with the pine chips and waste liquors and for providing
valuable technical assistance with the pilot-scale experiments.
                                 29

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                        REFERENCES
12th Edition of Standard Methods for the Examination of Water
     and Waste Water.  Publ.  by APHA, AWWA & WPCF (1965).

Mi ddlebrooks ,  E. J., e_t_ a\_. :  "Spraying of Stored Pulpwood with
     Waste Water," Tappi 5J_ (7) 93A  (1968).

Djerf, A. C. ,  and Volkman, D.  A.:  "Water Spray Wood Storage,"
     Paper Trade Journal 153 (10) 51 (March 1, 1969).
                               31

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                            APPENDIX


                                                             Page

Table 1.  Properties of waste Kraft pulping liquor before
            and after gravity flow of the liquor through
            a column of pine chips (pilot-scale experi-
            ments)	35
                                  33

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Appendix Table 1
Properties of waste Kraft pulping liquor before and after gravity
liquor through a column of pine chips (pilot-scale experiments)
flow of the
Temp.
(C) D
12
12
12
12
12
12
13
13
13
13
13
13
14
14
15
15
15
15
14
13
13
13
13
12

Flow
(Gal/
ry Chi
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.

Rate
Ib.
ps/Hr)
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7

El apsed
Time of
L i q uo r F 1 ow
(mi n . )
1
15
30
45
60
75
95
105
120
135
150
165
185
195
210
225
240
255
275
285
300
315
330
345

Total
of L
Fi Ite
rh rough
(Ga
Dry
_
0
0
0
0
0






2
2
2
2
2
3
3
3
3
3
3
4

Amount
quor
red
the Chip
1/Lb
Chips)
_ _ _
.18
.35
.53
.71
.89
.12
.23
.41
.59
.77
.94
.18
.30
.47
.65
.82
.00
.24
.35
.53
.70
.88
.06

s pH
Before
Contact
9-9
9-8
0.9
9-9
10.0
10.0
9-9
9-9
9-8
9-9
9-9
10.0
10.0
10.0
	
	
	
10.3
	
	
	
	
	
10.0

PH
After
Contac
9-0
9-2
9-3
9-5
9-5
0.3
9-5
9-4
9-5
9-5
9-4
9-5
9-7
9-7



10.0
	

	


9-8
(Conti
t ApH
0.9
0.6
0.5
0.4
0.5
0.7
0.4
0.5
0.3
0.4
0.5
0.5
0.3
0.3



0.3
	
	
	
	
	
	
nued)
Before
Contact
(ppm)
380
350
320
310
460
340
350
350
350
370
420
410
450
450
530
510
620
560
520
490
490
450
450
440

6005
After
Contact
(ppm)
670
600
520
480
330
520
460
440
430
470
440
430
580
492
510
600
680
540
530
560
500
480
470
450

. ABODr
(ppm)
+290
+250
+200
+ 170
+ 130
+ 180
+ 110
+ 90
+ 80
+ 100
+ 20
+ 20
+ 130
+ 40
- 20
+ 90
+ 60
- 20
+ 10
+ 70
+ 10
+ 30
+ 20
+ 10


-------
     Appendix Table 1  (continued)
UJ
ON
Flow Rate
Temp. (Gal/lb.
(C) Dry Chips/Hr)
10
10
10
10
10
10
11
11
11
11
120
12
13
13
]k
14
14
15
15
15
15
15
13
13
13
13
13
13
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
El apsed
T i me of
Liquor Flow
(mi n . )
1
15
30
45
75
90
105
120
135
150
165
180
195
210
225
240
255
270
285
300
330
360
375
390
405
420
438
450
Total Amount
of Liquor
Filtered
Through the Chips pH
(Gal/Lb Before
Dry Chips) Contact
_ _
0.
0.
0.
0.
1 .
1.
1.
1.
1.
1.
2.
2.
2.
2.
2.
3.
3.
3.
3.
3-
4.
4.
4.
4.
4.
5.
5.
_ _
18
35
53
89
06
23
41
59
77
94
12
30
47
65
82
00
18
35
53
88
23
41
49
77
95
13
30
10.5
10.5
10.4
10.5
10.5
10.5
10.4
10.4
10.3
	
10.4
	
10.4
	
10.4
	
10.4
	
10.4
	
10.4
	
10.4
	
	
	
	
10.4
PH
After
Contact
9-5
9-7
9-8
9-9
10.2
10.2
10.1
10.1
10.0
	
10.2
	
10.2
	
10.2
	
10.2
	
10.2
	
10.2
	
10.2
	
	
	
	
10.2
ApH
1.0
0.8
0.6
0.6
0.3
0.3
0.3
0.3
0.3

0.2
	
0.2
	
0.2
	
0.2
	
0.2
	
0.2
	
0.2
	
	
	
	
0.2
BOD5
Before
Contact
(ppm)
330
560
380
410
420
400
400
430
440
470
460
410
480
430
550
490
580
550
560
600
590
420
430
450
420
400
440
420
BOD5
After
Contact
(ppm)
660
680
550
580
520
400
470
470
450
430
480
460
510
500
460
490
600
540
620
630
610
470
500
490
490
470
490
480
ABODr
(ppm)
+ 340
+ 120
+ 170
+ 170
+ 100
+ 60
+ 70
+ 40
+ 10
- 40
+ 20
+ 50
+ 30
+ 70
- 90
0
+ 20
- 10
+ 60
+ 30
+ 20
+ 50
+ 70
+ 40
+ 70
+ 70
+ 50
+ 60

-------
BIBLIOGRAPHIC:

  School of Forest Resources, North Carolina State University,
Dilute Spent Kraft Liquor  Filtration Through Wood Chips,  Final
Report FyPCA Grant No.  WPRD 115-01-68,  April, 1970
ABSTRACT

  The principal objective  of  this project was to determine  if
contact between effluent  from a Kraft pulp milt and pine chips
would reduce  the water pollution characteristics of the waste
I iquor.

  The experimental work was divided into two phases:  1) a
small scale  laboratory investigation of contacting dilute
waste liquor with chips;  2) a pilot-scale  investigation of
filtering waste liquor through a column and a pile of chips.

  It was found that contact of alkaline waste liquor, or even
distilled water, with pine chips extracted organic matter from
the chips which had a considerable 8005.  This extract corre-
sponded to  a  pollution load of about 3-11  Ibs. BODj per ton
of dry wood.  Alkalinity,  pH, and intensity of color of the
ACCESSION NO.
   KEY WORDS:

Water Pollution
Waste Water
BOD-extraction
Kraft  Pulp Mill
Wood  Chips
BIBLIOGRAPHIC:

  School  of Forest Resources,  North Carolina State University,
Dilute Spent Kraft Liquor Filtration Through Wood Chips, Final
Report FWPCA Grant No. VIPRD 115-01-68, April, 1970
ABSTRACT

  The principal objective of this  project was to determine if
contact between effluent from a Kraft pulp mil)  and  pine chips
would reduce the water pollution characteristics of  the waste
Iiquor.

  The experimental work was divided  into two phases:   1) a
small scale laboratory investigation of contacting dilute
waste liquor with  chips; 2) a pilot-scale investigation of
filtering waste liquor through a column and a pile of  chips.

  It was found that contact of alkaline waste liquor,  or even
distilled water, with pine chips extracted organic matter from
the chips which had a considerable BOD;.  This extract corre-
sponded to a pollution load of about 3-11 Ibs. BODj  per ton
of dry wood.  Alkalinity, pH, and  intensity of color of the
 ACCESSION  NO.
   KEY WORDS:

 Water Pollution
 Waste Water
 BOD-extraction
 Kraft Pulp Mill
 Wood Chips
 BIBLIOGRAPHIC:

   School of Forest Resources, North  Carolina State University,
 Dilute Spent Kraft Liquor Filtration Through Wood Chips, Final
 Report FWPCA Grant No. WPRB 115-01-fcB, April, 1970


 ABSTRACT

   The principal  objective of this  project was to determine if
 contact between  effluent from a Kraft pulp mill  and pine chips
 would reduce the water pollution characteristics of the waste
 I iquor.

   The experimental  work was divided  into two phases:   1) a
 small scale laboratory investigation of contacting dilute
 waste liquor with chips; 2) a pilot-scale investigation of
 filtering waste  liquor through a column and a pile of chips.

   It was found that contact of alkaline waste Uquor, or even
 distilled water, with  pine chips extracted organic matter  from
 the  chips which  had a  considerable BOD;.  This extract corre-
 sponded to a pollution load of about 3-11 Ibs. BODJ per ton
 of dry wood.  Alkalinity, pH, and intensity of color of the
 ACCESSION NO.
    KEY WORDS:

 Water Pollution
 Waste Water
 BOD-extraction
 Kraft  Pulp Mill
 Wood  Chips

-------
waste liquor were somewhat reduced by the contact.  These
reductions are, however, too small to have any practical  ap-
plication in effluent treatment.  It can, in general,  be
concluded that contact of alkaline waste liquor, or water,
with wood chips extracts soluble organics and adds poMotional
materials to the effluent stream.

  This report was submitted in fulfillment of Grant No. WPRD
115-01-68 between the Federal  Water Pollution Control  Admin-
istration and the Department of Wood and Paper Science,
School of Forest Resources, North Carolina State University
at Raleigh,  North Carolina.
waste liquor were somewhat reduced by the contact.   These
reductions are, however, too smalt to have any practical  ap-
plication in effluent treatment.  It can, in general,  be
concluded that contact of alkaline waste liquor, or water,
with wood chips extracts soluble organics and adds  pollutional
materials to the effluent stream.

  This report was submitted in fulfillment of Grant No. WPRD
115-01-68 between the Federal  Water Pollution Control  Admin-
istration and the Department of Wood and Paper Science,
School of Forest Resources, North Carolina State University
at Raleigh, North Carolina.
waste liquor were somewhat reduced by the contact.  These
reductions are, however, too small to have any practical ap-
plication in effluent treatment.  It can, in general,  be
concluded that contact of alkaline waste liquor, or water,
with wood chips extracts soluble organics and adds pollutional
materials to the effluent stream.

  This report was submitted In fulfillment of Grant No.  WPRD
115-01-68 between the Federal  Water Pollution Control  Admin-
istration and the Department of Wood and Paper Science,
School of Forest Resources, North Carolina State University
at Raleigh,  North Carolina.

-------