United States
Environmental Protection
Agency
Water Engineering
Research Laboratory
Cincinnati OH 45268
Research and Development
EPA/600/S2-86/002 Mar. 1986
Project Summary
Pilot Anaerobic Biological
Treatment of Pulp Mill Evaporator
Foul Condensate
Eugene Donovan, Jr.
Three pilot plants were built to com-
pare three types of anaerobic waste-
water treatment systems: the upflow
sludge bed, the anaerobic filter, and the
fluidized bed. Startup of the systems
was accomplished in 6 weeks by seed-
ing them with sewage plant digester
sludge acclimated to the waste. The
units removed 80% to 90% COD from
the neutralized foul condensate of a
paper mill at a loading of 6 to 7 kg
COD/m3 per day. At this loading, the
anaerobic filter and upflow-bed sludge
units performed at about the same
levels although effluent solids from the
upflow bed were higher. The fluidized-
bed system produced somewhat greater
removals of organics and had the
lowest effluent solids concentration.
Operation of the systems will be
continued for several additional months
for further comparisons of the units'
capacities and performances. Loadings
will be increased at a rate that will per-
mit the units to maintain reasonable
removal levels and effluent volatile
acids.
This Project Summary was devel-
oped by EPA's Water Engineering Re-
search Laboratory. Cincinnati. OH, to
announce key findings of the research
project that is fully documented in a
separate report of the same title (see
Project Report ordering information at
back).
Introduction
Three pilot plants were designed and
constructed to represent three relatively
innovative anaerobic processes for the
treatment of industrial wastes: the up-
flow sludge bed, the anaerobic filter, and
the fluidized bed. An initial, limited pro-
gram was conducted using the pilot
plants to gain operating experience and
to evaluate and demonstrate their per-
formance on a high-strength industrial
waste water.
Study objectives included:
1. development of operating and
treatment design parameters ap-
propriate to each process;
2. assessment of the applicability of
the processes to various industrial
wastewater classifications based
on existing information and study
results; and
3. development of final report to
present the results of the study.
Methods and Materials
Description of Pilot Plants
A fluidized-bed pilot plant was pur-
chased with a 3.65-m-high, 0.15-m-
diameter reactor containing 150 to 200
cm (fluidized depth) of quartz sand with
an average diameter of 0.4mm. The re-
cycle flow was pumped up through the
media to maintain the bed at about 30%
to 50% expansion. Waste was metered
into the recycle line, and effluent was
separated from the gas, which was
metered by a wet test meter before dis-
charge.
A design was developed for an
anaerobic filter and an upflow sludge bed
pilot plant. The flow schematics of the
two systems were essentially identical
except that the anaerobic filter contained
media and did not have the internal gas
separation and solids settling section.
The steel reactors were 3.65 m high and
0.76 m in diameter. The reaction zone in
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13.1
Nutrient Additions to Foul Condensate
plastic pal,ring media.
'^r ELs!, it-TV- -,-M-I. £_ -iSaiSlsiL™ sftj-, ..-..•u-BHUm.amn -a^r-a,,^
Ammonium chloride
Potassium phosphate
rovide additional clarification
Element
Concentration in Waste, mg/L
50
30
nickel chloride
ferfous chloride
-Selenious acid
Sodium tungstate
-Ammonium molybdate
chloride
jyianganese chloride _
l-ime
~Soric acfd ~~
"Th'iamine HCJ
'otheffic acfd
aaai§_was_i0.ffialjy neutralized with-both
,G.ay.slic and. lime to, avoid possible in-
.liitiJliQQ sLloxleity from, excessive con-
on. and storage
ical laborator"was 'constructed
Procedures
0.25
4.0
0.1
0.005
0.02
0.02
0.02
. O.02
- AC,,
20,
~ — ~"
illi'llfli
the studies for periods of several days at
relatively constant conditions.
Acclimation and Startup
''jAnaerobically digesting sludge was
""obtainid""from i"""loca'f sewage freatrrient
plant and put into a reactor tank 2 months
Studies
treata'BTilty'
before pilot plant construction. The pall
ring media to_ be used in the anagrgbic
^jj______j_.__._,_, __ ^j^-
sarnpies of the neutralized foul conden-
,_,.. - '
tne waste_
"Dut"'tEat'
...... liejytra Ijzed^
jHcreasing
actor to accIFmat¥t!ie"^udaeT"Aiicircula-~
1.8-2.8
ie ^acclimation to the waste was ting pump was used for mixing.
necessary. The sludge was acclimated by The pall rings, coated with slime, were
^n^^asirrathecoricentrationof gut into the filter, 'and mpjst,,fl.f,tba.,ac-
'SSe""fed to the sludge wfine~also^e3- climated sludge was placed into tn"e_up-_
ing acetic aid Jo maintain the_sjudge _ flow bed pilotjjnrt Liqujd effluent^was^
"-ctrvity'TablellistsaveFageresultsfrom" ::=:i-.-?.. .-VT.--T —, -?----—-
^ ^
used~t6~fill the fIuidized-bed reactor
7,000-12J)00
8,000-16,000
,'BO-W.
Table 3
Unit
Summary of Screening Study Results*
•feear
Wo"
Detention Loading _jEffluent
!rfifffipm j-tfijj —
Effluent
Time
Days
A Gas
m-e
0.5
Batch
Condensate
•Wo /
75
0.0
irifflrs"*-! • «BII fflir mxv a
70
1.9
1625
465
829
560
30,4
977
057
IMffiEpJ,!.. ,Illli»,JMa3|S..,H§S,l£ISlBSl,ffid for t c_Batch
23_ „ , _ 0 t
bhoru's were"added in D- Con' Condensate:
No.2-14g/L 4.5
upf/ow No. 3-9.6g/L 5,3
tg erjsup Sj^
'
£,.-- Con- Condensate.
s
2.1 7.0 2023
520 _ 9.3 7_ . OJ5]_ -
n H i in mi HI in n i • in iii linn iiiiif
iiiiniiniii mi 11 in in mini n« n in
1278
2906
750
1712
1545
90.9
69.7"'
85.5
0:55
0.94
JL021 ._. 2O60
6815
!IISJS3£|fiiM^
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initial waste was made up consisting of
80% of a 14,000-mg/L acetic acid solu-
tion and 20% foul condensate. The waste
was neutralized to pH 6.8 with lime and
caustic, and nutrients were added. The
resulting COD was 12,500 mg/L, and
volatile acids were 11,700 mg/L. The
pilot units were filled with the waste, and
the effluent recycle was started. A small
flow of waste was fed to each unit from
day 8 to 20 to make up for sample and
minor system losses. Volatile acids in the
systems decreased to less than 1800
mg/L in 10 to 15 days.
Starting on day 21, waste flows to the
units were increased gradually over the
next 25 days. Effluents from the upflow
bed and filter were settled in small
clarifiers for 1 to 3 hr. Detention and
settled solids returned to the units. The
raw waste composition was increased to
40% foul condensate on day 14, 60% on
day 24, and 100% on day 31. Supple-
mental acetic acid was added to the foul
condensate to maintain influent COD at
about 15,000 mg/L until day 46. The
flows, loadings, and removals in the pilot
units are listed in Table 4 for day 52.
Results
All three units produced gas at about
0.5 L/g COD removed, at loadings in the
lower range used in design of full-scale
systems. A relatively constant load to the
units was maintained for several weeks
to observe performance at steady state as
several batches of waste were fed to the
units. The clarification of effluent and
return of solids wasdiscontinued. During
this period, the COD concentration in the
foul condensate batches varied and was
considerably lower than that obtained
during the laboratory screening and
startup period. As a result, the loadings
and flows to the units were somewhat
more, variable than desired during this
attempt at a steady-state loading.
Results of the anaerobic filter up to
day 70 were fairly consistent; however, a
60% increase in influent COD concentra-
tion resulted in an 85% load increase on
day 70 and produced an increase in
effluent volatile acids. At the same time,
a 30% decrease in gas production also
occurred. This decrease could not be di-
rectly attributed to any single factor, but it
might have been caused by a drop in pH
from 7.3 to 6.6, the higher volatile acid
concentrations, or a change in a waste
constituent. Loading was reduced to zero
on day 74, and a new waste batch was
put on line on day 75 at a loading of about
5 kg/m3 per day. Effluent volatile acid
levels dropped back to the 1000 to 1500
mg/L range through day 80. During this
6-day period, COD removal was 86.5%,
effluent volatile acids were 1200 mg/L,
and gas production was 0.52 L/g of COD
removed, indicating recovery of the unit.
The results with the upflow bed unit
were similar to these for the anaerobic
filter. Flow and loading were maintained
relatively uniformly through day 75 ex-
cept for two days. Scale buildup and
debris from the initial sludge seed oc-
casionally clogged the recycle lines, re-
sulting in flow blockages and variations.
The scale formed by precipitated calcium
compounds also caused problems in the
heaters on both the filter and upflow bed.
Starting with day 76, only caustic was
used for neutralization, with about 20
mg/L calcium added as nutrient to the
raw waste. On day 66, a new waste load
was introduced, and effluent volatile
acids increased. The load was decreased,
and volatile acid level decreased. On day
70, a new waste batch was brought on
line at much higher condentration, re-
sulting in 100% increase in loading. Gas
production dropped markedly, but it re-
covered on the following day. The unit
operated well until pump problems de-
veloped around day 78 and influent flow
had to be reduced.
Flow and loading to the fluidized bed
was fairly constant for the initial 15 days,
and effluent volatile acids were low. A
power outage resulted in a low flow on
day 64. On day 70, when the new high-
strength waste was brought on line, load-
ing increased 100%. However, effluent
volatile acids did not increase, and gas
production increased 35% over the next 2
to 3 days. This experience contrasts with
those of the two large pilot plants during
the same time period: they experienced
increases in volatile acids and gas reduc-
tion for 1 or 2 days. From day 70 to 78, the
loading was about the same as during the
first 15 days. During this period, the
system performance improved, as indi-
cated by the lower effluent volatile acids.
Conclusions
Table 5 compares average results for
the three systems over a 23-day period
ending on day 69. Loading and detention
times were similar for all three units. The
effluent parameters for the anaerobic
filter and upflow bed were practically the
same. The fluidized bed produced greater
organic removals and lower effluent con-
centrations. Gas production on the basis
of waste volume, COD removal, and
methane content was essentially the
same for all three units. Effluent sus-
pended solids were fairly high in the
three systems, but effluent solids de-
creased markedly in the filter and
fluidized bed toward the end of this study
period. The upflow bed experienced high
solids losses during this same period,
indicating the potential need for external
clarification, at least under these condi-
tions.
Table 4.
Day 52 Flows, Loadings, and Removals*
Flow,
Unit L/day
Fluidized-bed 12
Anaerobic filter 850
Upflow unit 710
COD
Loading,
kg/m3
per day
5.07
7.14
7.18
Volatile
Acids, mg/L
1200
846
1031
COD,
mg/L
1990
1599
2025
%CODR
83.2
86.5
82.9
Gas,
L/day
66
4392
3456
influent COD. 11.844 mg/L.
-------
X^ WW; Pi n mm
_ _ :,:,:;,|i,,i j&ciiwat. ,..,,..,
fapje^ .§_•,, , fAversge Results for_ the Three Anaerobic Systems for Days 46 through 49
W-AjWeiobic, „
upflow
Fluiaized
iiilffcii ,,
, .i1?:,!: , i? ...... :!! 3; slill1 :ii !s .i!
l1 :ii !s .i! I:1,1 1 H,!1:" J 'i
7. /
i BOD removal
WMS'WlWt 'I'fl'itiS''? HI*! li,:".:
,,' :,i : I?1':1!!' ii gin i,:!!, :,i; „„: iii i1!1!"; • "i iff. , 7'iiiiiiiiiii '•'.. piiw; liiiii;,' :i' i,i,:iiir iiift1:; 'Hi J IlsTiiiiiti,1 ,il
production, L/L ^ | , ,iii 5.4
" S3
Eugene J. Donovan. Jr. is with HydroQual, Inc., Mahwah, NJ 07430.
• T. David;_,Ferguson_ is the_ EPA^ Project^ Officer_ (see below).
—,,--—— ..... ,-——-———-— ..... ,___i .....
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w::n;]tjmMam^'wa'as:M\\mmK\'A
TB578,
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f?od
282
1278
127
Evaporator Foul Condensate," (Order No. PB 86-143 633/AS; Cost: ' $f(>.9~5,
subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, V A 221 61
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Water Engineering Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
Lllkliif I I !• / |,|l."'-:;
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