EPA
TECHNOLOGY
TRANSFER
                                     COLOR
                                     REMOVAL FROM
                                     KRAFT PULPING
                                     EFFLUENT BY
                                     LIME ADDITION
U.S. ENVIRONMENTAL
PROTECTION AGENCY
INDUSTRIAL
DEMONSTRATION
GRANT WITH
INTERSTATE PAPER CORP.


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EPA
TECHNOLOGY
TRANSFER
                                     COLOR
                                     REMOVAL FROM
                                     KRAFT PULPING
                                     EFFLUENT BY
                                     LIME ADDITION
U.S. ENVIRONMENTAL
PROTECTION AGENCY
INDUSTRIAL
DEMONSTRATION
GRANT WITH
INTERSTATE PAPER CORP.

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                                               ,
Aeria/ Vieui o/Aeration Basin during Discharge.

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            mm
  Kraft pulp today represents the principal
type of chemical pulp produced in the United
States, accounting for 30 million tons, or
83 percent of the 36 million tons of chemical
pulp produced in 1971. There are
approximately 120 mills with a median
capacity of 1000 tons per day manufacturing
Kraft Pulp, concentrated in a broad arc of
southern states ranging from Virginia to Texas,
and in the Pacific Northwest, with lesser
concentrations in the upper Great Lakes and
New England states.
  Discharge of a reddish brown colored
effluent is invariably associated with its
manufacture. While  no national color pollution
standards have as yet been developed to guide
the development and application of kraft
effluent decolorization technology, there are a
growing number of locations where
decolorization efforts have been requested by
state or local regulatory authorities.
  It has been known for twenty years that lime
addition was capable of decolorizing kraft
effluent, but intensified laboratory study in the
last ten years has indicated that several alternate
lime addition procedures are adaptable to
colored effluents from either the pulping or
bleaching stages of the kraft pulp production
process. The use of lime is made more
attractive by the existing major role occupied
by lime in the kraft process pulping chemical
recovery system, since it is already used in the
recausticizing stage.  This provides a dual
opportunity for (1) recovery of lime used for
decolorization and (2) destruction of removed
color by conventional thermal oxidation
processes.
  The reaction mechanisms governing lime
decolorization have been identified as
precipitation of calcium salts of weak organic
acids produced by chemical separation and
fragmentation of wood-derived lignin during
both pulping and bleaching.
  In this EPA Demonstration Grant to
Interstate Paper Corporation a full scale
process for lime decolorization of kraft pulping
total mill effluent was operated. Slaked lime
addition was followed by primary
sedimentation for removal of the mixed
fibrous and lime decolorization sludges. The
clarified effluent subsequently  underwent
biochemical stabilization in a quiescent storage
basin. Neutralization of excessive lime
alkalinity was achieved in  this basin by
absorption of atmospheric carbon dioxide. The
grant also supported  a pilotrscale study of
recarbonation for enhanced lime separation
and more rapid effluent neutralization prior to
biochemical stabilization.    ,
  While 83 of the 120 kraft mills produce
bleached kraft pulp whose effluent contains
substantially more color per ton  of product
than that from the pulping process alone, the
demonstration at the Interstate unbleached
kraft mill has the following significance: (1) It
demonstrated an effective decolorization ',
process applicable to the  37 mills producing
only unbleached pulp, (2) It provided a  '
calcium-rich decolorized effluent for
subsequent pilot-plant recarbonation
investigations applicable to all effluents from
lime decolorization processes, (3) it raised the
possibility of bleached kraft  total mill
effluent decolorization by a  similar lime
treatment process, and (4) it laid the basis for
additional studies of  decolorization lime
recovery in  conjunction with primary sludge
disposal.

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Lime Kiln and Slaker
  A calcium hydroxide dosage of 1000 ppm
derived from a calcium hydrate slurry at
1.04 sp.gr. produced in a conventional quick
lime slaker (S-l) is applied to a total mill
effluent of 1200 APHA color. Following a
35 minute flocculation period (T-l) gravity
clarification (C-l) at a rise rate  of .13 gpm per
square ft. clear rise area yields a decolorized
effluent of 125 APHA units, and 10 ppm
suspended solids. The clarifier  underflow
sludge contains 2 percent solids with
diminished dewatering characteristics, but can
be readily thickened to 6  percent solids. This
sludge is currently disposed of  by lagoon
storage (L-l).
  With natural recarbonation, the resultant
highly alkaline effluent (pH = 12.2)  containing
700 to 750 ppm lime (as Ca(OH)2) first
undergoes neutralization  by surface absorption
of atmospheric CO2 to pH 10.2, accompanied
by precipitation of nearly  all the remaining
calcium in the inlet section of the stabilization
basin (B-l). Biochemical oxidation results in
further neutralization and overall BOD and
COD reductions of 98 and 95 percent
respectively. Clarifier sludge load totals about
30 tons per day, of which thirty percent
represents added lime.

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Lime Mixing Tank and Primary Clarifier.
   The use of a recarbonation process instead
   of relying upon absorption of atmospheric
   was investigated on pilot scale to obtain
   preliminary design data. Figure 2 shows the
   pilot flow sheet. Decolorization clarifier (C-l)
   overflow enters a carbonator (R-l) providing
   16 to 20 minutes residence time, receiving
   scrubbed lime kiln  stack gas at 180F.
   Following clarification (C-2) at a rise rate of
   2.5 gal. per minute per sq.ft. residual calcium
   level is reduced to  1 Ib CaCO:! per 1000
   gallons. This can be further reduced by
   50 percent if the lime kiln gases are pretreated
   with mechanical cyclones alone and enter the
carbonator at 325F instead. Recarbonation at
this point adds approximately 10 tons of
sludge solids which would otherwise be
precipitated in the stabilization basin to the
30 tons obtained during decolorization and
improves overall dewatering characteristics.
The additional sludge is of high purity
however, and it could be introduced to the
lime recovery cycle. Reduction in pH by a
recarbonation process would probably extend
the effectiveness of the quiescent biochemical
oxidation lagoon since a portion of the capacity
is now required for neutralization by absorption
of atmospheric

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   MIXING TEE
                                                         LIME STORAGF. TANK
                                                           VARIABLE SPEED
                                                          SCREW CONVEYOR
                                                                                HJTUKE HECARBONATION
                                                                                UMI-: RKCOVKRY SYSTEM
I.HI.UENT LIFT PUMPS
                                                                       EMERGENCY

                                                                      DIVERSION BOX
                                                                         01
                                            HOLDING LAGOON
                                       FIGURE 1
                      FULL SCALE DECOLORIZATION SYSTEM
                                                                               FLOAT
                                                                            MOUNTED
                                                                             AERATOF
                                                                                         BIOCHEMICAL
                                                                                         THKATMENT IAKE

                                                                                         650 ACKES-900 MG
                                                                                         1181) DAYS REI'ENTIONI
                                                                                 HICEBORO CREEK

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                                  EXCESS GAS
                                                              REACTOR
                                                             THICKENER
                                                              CLARIFIER
 SIMULATED
  UME KILN
EXHAUST GAS
                                                                     FUTURE
                                                                      LIME
                                                                   RECOVERY
SLUDGE BLOW DOWN
                                                    FIGURE 2
                                    RECARBONATION PILOT PLANT FLOW SCHEME

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 TYPICAL EFFLUENT COMPOSITIONS AT INTERSTATE PAPER CORPORATION
                           RICEBORO, GEORGIA MILL

                  (All Data in Ibs. per ton Pulp/Board unless otherwise noted.)
Flow (Gal/Ton)
pH
Suspended Solids
BOD
COD
Color. APHA Units
Calcium as CaCO3

Sludge Solids
Estimated Overflow
from Primary Clarifier
without Lime Treatment
15000
8.5-9.5
5.0(40ppm)
41(330ppm)
121(970ppm)
1200
<650ppm)

105
Overflow from Primary
Clarifier with 1000 ppm
CaCO, Lime Dosage
15000
12.2
1.25 (10 ppm)
28 (220 ppm)
66 (525 ppm)
125
125 (1000 ppm)

150
Final Effluent at Interstate
Paper after Lime Treatment
plus Natural Recarbonation
and Biological Treatment
in Stabilization Basin
15000
7.5-8.5
1.25 (10 ppm)
.6 (5 ppm)
6 (50 ppm)
125
4 (35 ppm)

255:
'Includes estimated Sludge deposited in Stabilization Basin during Natural Recarbonation

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  Construction costs for the decolorization
portion of the treatment facilities totalled
$481,600 including land. These costs covered
site development, lime slaking, storage and
feed control facilities, flocculation, a portion of
the clarification unit and sludge storage
facilities costs, project engineering, and
construction supervision. First year operating
costs for chemicals, power, labor, and plant
overhead totalled $289,000 with lime costs
estimated at $15.35 per ton lime (as 90 percent
CaO).  First year special study costs including
administration,  contingencies, system revisions
and post-construction studies and reports
totalled $133,100. These special study costs
are not included in the economics presented.
(2) A major portion of the operating costs is
accounted for by the non-recovered lime,
including that separable by treated effluent
recarbonation, as well as the lime present in
the settled sludge.
  The  grant at Interstate did not include
testing these modifications. The potential for
raw material savings by recovery of the lime
used is valued at approximately $78,000
annually as lime rock or $0.56 per ton of
pulp/board. Lime recovery would increase
fixed maintenance, labor, and power costs and
decrease chemical and long term sludge
disposal costs.
                                   Aerial View of Sludge Lagoons and Effluent entry
                                   into Oxidation Pond.

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140,000 NOMINAL TONS/YR (197,000 TONS/YR ACTUAL)
OF
UNBLEACHED KRAFT PULP
TOTAL INVESTMENT
(including engineering, excluding land)                                          $455,000
operating costs (all cost in $/Yr)
 I  Wages (operator/shift plus allotted supervision and technical assistance)               71,000
 II  Electric Power (288 hp, including lift station, at 8 mils)                             14,000
III  Maintenance                                                              30,000
IV  Laboratory (included in Technical Assistance)
 V  General Plant Overhead                                                    45,000
VI  Raw Materials Lime ($15/Ton)                                              129,000
                                         TOTAL OPERATING  COSTS        289,000

FIXED CHARGES
    Depreciation @ 10  years                                                   45,000
    Interest on Loan @ 9%                                                    41,000
    Taxes, Insurance                                                          9,000
                                        TOTAL FIXED CHARGES            95,000
                                        NET YEARLY COST TOTAL         384,000
                                        OPERATING  COST = $1.47/ton pulp
                                        TOTAL COSTS=$1.95/ton pulp

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  The process as described, and with the
potential for adding features for lime recovery,
believed directly applicable to  unbleached
kraft mills. This process with lime recovery is
currently being applied to the  Continental  Can
unbleached kraft mill at Hodge, Louisiana.
  The process might also find application at
bleached kraft mills where use of lime
precipitation techniques on the heavily colored
caustic extraction stage effluent prove
inadequate to accomplish the desired degree
of decolorization. It might also find application
in treating the mixed color-containing mill
effluents from a bleached kraft pulp mill,
particularly where acidic effluent neutralization
is required prior to biological treatment.
                Aerial View of Aeration Basin at Outfall into
                Receiving Stream.

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FOR FURTHER INFORMATION:

DETAILED INFORMATION ON THIS PROJECT,           TECHNOLOGY TRANSFER
INCLUDING EQUIPMENT LIST, IS AVAILABLE           U.S. ENVIRONMENTAL
FROM THE SUPERINTENDENT OF           OR WRITE PROTECTION AGENCY
DOCUMENTS AS EPA REPORT 12040 ENC              WASHINGTON, D.C.
"COLOR REMOVAL FROM KRAFT PULPING             20460
EFFLUENT BY LIME ADDITION"

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