Process Biochemistry 39 (2003) 279 /286
www.elsevier.com/locate/procbio
Sequential (anaerobic/aerobic) biological treatment of malt whisky
wastewater
Niğmet Uzal, Celal F. Gökçay, Göksel N. Demirer *
Department of Environmental Engineering, Middle East Technical University, Ankara 06531, Turkey
Received 11 February 2002; received in revised form 6 February 2003; accepted 6 February 2003
Abstract
The anaerobic treatability of malt whisky distillery wastewater was investigated. Biochemical methane potential (BMP)
experiments were conducted both with and without basal medium (BM) to observe the effect of nutrient supplementation. For batch
reactors containing no nutrients but only NaHCO3, net total gas production at the end of 29 days were observed as 0.019 m3 gas/kg
COD removed. With nutrient supplemented reactors the net total gas production was 0.020 m3 gas/kg COD. Continuous reactor
experiments were carried out in two stage upflow anaerobic sludge blanket (UASB) reactors. These experiments indicated that the
two stage UASB reactor configuration is an efficient system for malt whisky wastewater treatment until up to 33 866 mg/l influent
COD concentration. Following the UASB experiments aerobic experiments in batch reactors were also conducted and further COD
and BOD removal of up to 55 and 70%, respectively, were achieved.
# 2003 Elsevier Science Ltd. All rights reserved.
Keywords: Sequential (anaerobic/aerobic) treatment; Distillery wastewater; Whisky; UASB
1. Introduction
Anaerobic digestion is undoubtedly the most suitable
option for the treatment of high strength effluents. The
presence of biodegradable components in the effluents
coupled with the advantages of anaerobic processes over
other treatment methods makes it an attractive option
[1]. The BOD content of many high strength effluents
from food, fermentation, beverage and pulp and paper
industries can successfully be reduced by anaerobic
digestion.
Whisky is prepared from fermented cereals and is
normally matured in oak barrels. Corn (maize), rye,
barley and wheat are the typical cereals used for whisky
manufacturing. The processes of whisky production
involves malting, mashing, fermentation, distillation
and maturation [2]; frequently producing wastes, very
strong in character. COD and suspended solids concentrations range between 10/60 and 10 g/l, respectively.
* Corresponding author. Present address: Department of Biological
Systems Engineering, Washington State University, PO Box 646120,
Pullman, WA, USA. Tel.: /1-509-335-3826; fax: /1-509-335-2722.
E-mail address: [email protected] (G.N. Demirer).
These wastewaters have previously been treated aerobically after dilution with other wash waters. However,
aerobic treatment has always been difficult because of
the acidity of the waste, its high temperature and high
oxygen demand. Thus, distillery wastes were considered
most suitable for anaerobic treatment [3].
Harada et al. [4] studied the anaerobic treatment of an
alcohol distillery wastewater using an upflow anaerobic
sludge blanket (UASB) reactor for a period of 430 days.
A 28 kg COD/m3 day organic loading rate (OLR) was
applied while reducing the hydraulic retention time
(HRT) at a fixed influent concentration of 10 g COD/
l. COD removals during the entire experimental period
were relatively low, between 39 and 67%, while BOD
removals were more satisfactory, namely more than
80%. In the period between 50 and 160 days, COD
removal tended to worsen as the loading increased from
4.1 to 28 kg COD/m3 day.
Akunna and Clark [5] have studied the performance
of a granular bed anaerobic baffled reactor (GRABR) in
the treatment of a whisky distillery wastewater. The
COD and BOD concentrations of the whisky distillery
wastewater were 16 600/58 000 and 8900/30 000 mg/l,
respectively. The anaerobic baffled reactor (ABR) was
0032-9592/03/$ - see front matter # 2003 Elsevier Science Ltd. All rights reserved.
doi:10.1016/S0032-9592(03)00071-2
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N. Uzal et al. / Process Biochemistry 39 (2003) 279 /286
fed with diluted whisky distillery wastewater containing
9500 mg/l COD at 10, 7, 4 and 2 days hydraulic
retention (HRT) values; corresponding to OLRs of
0.99, 1.33, 2.37 and 4.75 kg COD/m3 day, respectively.
The removal of total BOD and COD from the wastewater were 80 /92 and 90 /96%, respectively. The best
performance was observed with a HRT of 4 days and at
a loading rate of 2.37 kg COD/m3 day. When the HRT
was decreased to 2 days, the efficiency of the GRABR
dropped, but removal rates remained relatively good.
Tokuda et al. [6] performed a pilot scale anaerobic
treatment test for non-diluted pot ale effluents using an
upflow anaerobic filter (AF). The support medium was
a modular structure composed of multi layer plates. The
COD removal efficiency exceeded 76% at 20 kg COD/m3
day OLR. 80% or more of the organic nitrogen content
was converted into NH4-N, and 90% or more of the
organic phosphorus content were converted into soluble
PO43-P. Approximately 70% of the total nitrogen
content was removed by biological nitrification and
denitrification treatment.
The study of anaerobic digestion of distillery waste in
the two-stage reactor enabled the identification of two
main phases of the process */fermentative (acidogenic)
and acetogenic/methanogenic phase. The acidogenic
reactor performed satisfactorily in terms of conversion
of initial COD to volatile fatty acids (VFAs). VFAs
produced in the first stage were readily used as
substrates in the acetogenic/methanogenic stage [7].
Goodwin et al. [8] used two identical UASB reactors
operated in parallel as duplicates for the treatment of
malt whisky pot ale and achieved COD reductions of up
to 90% for influent concentrations of 3526 /52 126 mg/l.
This study was conducted for 327 days. When the OLRs
of 15 kg/m3 day and above were used, the COD removal
efficiency dropped to less than 20%, in one of the
duplicate reactors.
In another study, Goodwin et al. [9] stated that
digester failure occurred when undiluted pot ale was
fed into UASB reactors. Stable operation was observed
at OLRs of 5.46 kg COD/m3 day or less.
2. Materials and methods
2.1. Characterization of malt whisky wastewater
Malt whisky wastewater was obtained from Ankara
Tekel malt whisky distillery and was chemically characterized. For this purpose pH, COD, BOD, Total
Kjeldahl Nitrogen (TKN), total PO4 and PO4-P, were
measured in samples using Standard Methods [10], as
tabulated in Table 1.
Table 1
Characteristics of Ankara Tekel malt whisky distillery wastewater
Parameter
Concentration (mg/l)
COD
BOD
TKN
Total PO4
Total PO4-P
37 060 /50 700
15 600 /22 100
45.4 /71.7
222 /665
72.4 /216.7
2.2. Basal medium (BM)
The composition of BM used in all the experiments
was as follows (concentrations of the constituents are
given in parentheses as mg/l): NH4Cl (1200), MgSO4 ×/
7H2O (400), KCl (400), Na2S ×/9H2O (300), CaCl2 ×/2H2O
(50), (NH4)2HPO4 (80), FeCl2 ×/4H2O (40), CoCl2 ×/6H2O
(10), KI (10), MnCl2 ×/4H2O (0.5), CuCl2 ×/2H2O (0.5),
ZnCl2 (0.5), AlCl3 ×/6H2O (0.5), NaMoO4 ×/2H2O (0.5),
H3BO3 (0.5), NiCl2 ×/6H2O (0.5), NaWO4 ×/2H2O (0.5),
Na2SeO3 (0.5), cysteine (10), NaHCO3 (6000) [11].
2.3. Biochemical methane potential (BMP) experiments
Three types of culture were employed in the anaerobic
experiments: (1) mixed anaerobic culture (2) acetateenriched Methanosarcina culture and (3) mixed UASB
granules. Mixed anaerobic culture was obtained from
the anaerobic sludge digesters of the Greater Municipality of Ankara Domestic Wastewater Treatment
Plant. Digesters had retention times of 14 days. The
average sludge flow from primary thickeners to each of
the digesters was 805 m3/day. The pH inside the
digesters ranged from 7 to 7.7. The mixed anaerobic
culture was thoroughly homogenized and filtered
through a screen of 1 mm mesh size before being used
as inoculum. The acetate enriched Methanosarcina
culture was obtained from a pH-Stat continuous stirred
tank reactor (CSTR) operating for 89 days at a constant
pH of 6.89/0.2.
The pH-Stat CSTR consisted of a magnetically stirred
glass Erlenmeyer of 1.6 l effective volume with a
headspace of 400 ml (Fig. 1). The Erlenmeyer was
sealed with a rubber stopper and contained ports for
probing, feeding, sample withdrawal and gas venting.
The pH-Stat CSTR had no sludge recycle and a pH
controller and a pH probe were incorporated. The pH
increased when the substrate was consumed by the
microorganisms. When the pH of the culture exceeded
the pH set point of 6.8, the pH controller unit operated
the feed peristaltic pump for 1 s. Thus a fixed amount of
substrate was delivered to the reactor lowering the pH
for not more than 0.2 pH units. This way, the pH value
in the reactor was kept maintained at 6.89/0.2 [12].
N. Uzal et al. / Process Biochemistry 39 (2003) 279 /286
Fig. 1. Schematic diagram of a pH-Stat CSTR.
In order to observe the anaerobic treatability and the
effect of nutrient supplementation on the anaerobic
treatment of malt whisky wastewater, BMP experiments
were conducted both with and without BM. In the first
set only 6000 mg/l of NaHCO3 was delivered into the
serum bottles as the source of alkalinity and no other
nutrients were supplemented. A second set of serum
bottles contained BM. The mixed anaerobic culture and
the acetate enriched Methanosarcina culture were used
collectively as seed. The cultures were added to the
reactors at a volumetric ratio of 1:1. Experiments were
conducted in 110 ml serum bottles with 50 ml effective
volumes. After seeding and supplementing the necessary
nutrients, serum bottles were flushed with 25% CO2 and
75% N2 gas mixture and incubated in a temperaturecontrolled room at 359/2 8C. Gas production was
monitored daily for 30 days by a water displacement
device in each serum bottle. The serum bottles were
seeded at a volumetric ratio of 1:1 with the anaerobic
mixed culture, which had mixed liquor suspended solids
(MLSS) and mixed liquor volatile suspended solids
(MLVSS) concentrations of 589/0.7 and 18.69/0.4 g/l,
respectively, and the acetate enriched Methanosarcina
cultures which had MLSS and MLVSS concentrations
369/0.11 and 12.49/0.15 g/l, respectively. The initial
COD concentrations in anaerobic batch reactors were
5.07, 10.14, 15.21 g COD/l.
281
Each reactor was constructed of a cylindrical plexiglass column with a height and inner diameter of 50 and
2.5 cm, respectively. The volumes of each reactor were
245 ml and effective volumes were 113 ml. The two
reactors were connected in series. Wastewater was
continuously fed into the inlet of the first UASB reactor.
The effluent of the first stage UASB then passed to the
inlet of the second stage. Spiral shaped wires with a
length of 60 cm and a cross section of 1.5 mm2 were
placed into the reactors to avoid floating of the granular
sludge. The reactors were operated in a temperaturecontrolled room at 359/2 8C.
In the effluent of the reactors, pH, alkalinity (as
CaCO3) and VFA, COD, BOD, TKN, total phosphate,
phosphorus, MLSS and MLVSS were measured using
Standard Methods [10]. The sampling frequency for
COD, pH, alkalinity and VFA analyses which were
carried out in duplicates were two or three times a week.
The other parameters were measured upon increasing
the influent COD, again in duplicates.
2.5. Batch aerobic reactor experiments
This study was conducted to determine the aerobic
post-treatability of malt whisky wastewater following
anaerobic treatment, in order to meet discharge standards. Experiments were conducted in 500 ml volumetric flasks. Sample volumes were 100 ml. The batch
aerobic reactors were continuously shaken for 15 days in
a shaker at 380 rpm at 25 8C.
Aerobic cultures were obtained from a semi-continuously operated base-line reactor with 8 days sludge
retention time (SRT). Initial aerobic cultures to this tank
were obtained from aeration tanks of the activated
sludge units of the Ankara Municipal Wastewater
Treatment Plant, which was operating with a sludge
age and organic loading of 2.8 days and 16 500 kg
BOD5/day, respectively. In batch aerobic reactor experiments, the effluent of the anaerobic reactors was used as
the feed and BOD and COD values were measured at
days 0, 5, 10, 15.
2.4. UASB experiments
3. Results and discussion
Granular cultures were obtained from the UASB
reactors of the Wastewater Treatment Plant of İstanbul
Tekel Paşabahçe Liquor Factory. The OLRs of the
UASB reactors were 30 kg COD/m3 day. The pH of
UASB reactors ranged between 6 and 9. The reactors
were seeded with anaerobic granular sludge and resulted
in a sludge volume of 113 ml in each reactor. The
biomass inventory in each reactor was approximately
6.19/0.12 g. The wastewater, which was mixed with a
magnetic stirrer, was fed continuously into the inlet of
the first stage UASB reactor.
3.1. BMP experiments
BMP experiments were performed for three different
COD concentrations, namely 5070, 10 140, 15 210 mg/l.
Serum bottles for the three COD concentrations were
run in duplicate. Control serum bottles were also run in
parallel to determine the background gas production.
The average gas productions observed in each serum
bottles are presented in Fig. 2.
For the batch anaerobic reactors containing no
nutrients but only NaHCO3, the gas production in
282
N. Uzal et al. / Process Biochemistry 39 (2003) 279 /286
Fig. 3. Comparison of the theoretical and experimental gas production for BMP experiments.
mental errors in CH4 determination as well as the
refractory COD content of the wastewater.
For initial COD concentrations of 5.07 and 10.1 g/l
the total gas production for the nutrient supplemented
(98 and 214.1 ml) and not supplemented (98.7 and 220.8
ml) serum bottles were similar. However, net total gas
production for the COD concentration of 15.2 g COD/l
was 332.6 ml for the nutrient supplemented set while it
was 260.5 ml for the alkalinity only set.
3.2. UASB experiments
Fig. 2. BMP experiment results of BM with only NaHCO3 set-up (a),
and for with only BM set-up (b).
control sample was 12.8 ml as seen from Fig. 2(a). For
the COD concentrations of 5070 and 10 140 mg/l an
acclimation period of 10 days was observed for serum
bottles with no nutrient supplementation (Fig. 2). The
acclimation period needed was about 15 days for the
initial COD concentration of 15 210 mg/l. Following the
acclimation period, the gas production rates were
observed to increase significantly (Fig. 2a). The delay
in gas production observed in the no-nutrient bottles
(Fig. 2a) was not observed in the nutrient supplemented
set (Fig. 2b). Therefore, the delay in gas production in
the first set of reactors, which corresponds to the
acclimation phase, was thought to be due to lack of
nutrients.
The theoretical gas production which was calculated
using the stoichiometric CH4 production (1 g COD is
equivalent to 395 ml of methane) and CH4 content of
the biogas 779/5% was compared with the experimental
(observed) values (Fig. 3). The amount of gas produced
by the cultures with BM or without BM supplementation was similar but slightly off the range of theoretical
gas production. This may be explained by the experi-
The operational conditions including OLRs, HRTs
applied to the first stage UASB reactor system, influent/effluent COD concentrations, COD removal efficiencies, effluent MLSS and MLVSS concentrations,
influent /effluent BOD concentrations, BOD removal
efficiencies are presented in Fig. 4a/g, respectively.
Similarly, OLRs, HRTs applied to the second stage
UASB reactor and influent /effluent COD concentrations, along with COD removal efficiencies, influent /
effluent BOD concentrations and BOD removal efficiencies are presented in Fig. 5a/f, respectively. During
the entire operation of the reactors, HRT was reduced
gradually from about 10 to 5 h (Fig. 5a). On days 66, 67,
71, 73, 74, 82, and 83, uncontrolled increases in the HRT
were encountered due to operational problems.
OLRs of the two-stage UASB reactor system increased from 0.6 to 48.1 kg/m3 day in a stepwise manner
(Fig. 4b and Fig. 5b). Over this period, the influent
COD concentration was increased from 1000 to 33 866
mg/l in the first stage (Fig. 4c). Different influent COD
concentrations (1000, 3638, 3320, 12 060, 11 087, 20 920,
33 866 mg/l) were applied to the first stage of the system.
On day 29, HRT and OLR of the first and second
stage of the UASB reactor system were 5.2 h and 15.3
N. Uzal et al. / Process Biochemistry 39 (2003) 279 /286
283
Fig. 4. Operational conditions and results of the first stage UASB reactor; (a) HRT, (b) OLR, (c) COD concentrations, (d) COD removal efficiencies,
(e) effluent MLSS /MLVSS concentrations, (f) BOD concentrations, (g) BOD removal efficiencies.
kg/m3 day and 5.2 h and 3.7 kg/m3 day, respectively. The
COD removal rate of the first stage was 76% and COD
and BOD removal efficiencies of the second stage were
39 and 82% at 3320 and 795 mg/l influent COD
concentrations, respectively. On day 45, HRT and
OLR of the first and second stages were 9.7 h and
27.5 kg/m3 day and 9.7 h and 13.3 kg/m3 day,
respectively. The COD removal efficiency of the first
stage was then recorded as 52% and COD and BOD
removal efficiencies of the second stage were 47 and 50%
284
N. Uzal et al. / Process Biochemistry 39 (2003) 279 /286
Fig. 5. Operational conditions and results of the second stage UASB reactor; (a) HRT, (b) OLR, (c) COD concentrations, (d) COD removal
efficiencies, (e) BOD concentrations, (f) BOD removal efficiencies.
at 11 087 and 5363 mg/l influent COD concentrations,
respectively.
When a COD concentration of 20 920 mg/l was
maintained in the influent to the first stage, the effluent
quality of the first stage began to deteriorate. Furthermore, a significant color change was observed. The color
turned from black to brownish black and then to brown,
and this was thought to be due to reduced metabolic
activity owing to the toxic effect of the wastewater on
granular biomass, thus increasing oxidation/reduction
potential.
Higher loading rates and higher gas production rates
caused an increase in the MLSS and MLVSS concentration of the reactor effluent. Because of biomass in the
99.50
99.50
99.50
99.5
98.21
98.12
97.98
98.1
88.06
88.79
87.55
88.1
30
45
40
38.2
55
61
53
56
605
635.5
683.5
641.3
99
98
98
98.3
1332
1633.5
1461
1475.5
96
95
96
95.7
17 680
17 680
17 680
17 680
33 866
33 866
33 866
33 866
250
400
320
323.3
COD Rem%
Rem %
COD (mg/l)
BOD (mg/l)
COD (mg/l)
BOD (mg/l)
Rem %
COD (mg/l)
Rem %
BOD (mg/l)
Rem %
Overall system
After aerobic treatment (unacclimated culture)
After anaerobic treatment
Raw wastewater
Table 2
Operational results after anaerobic treatment and aerobic treatment
effluent, the effluent COD concentration was higher
than the influent COD concentration in the first stage of
the reactor. These observations indicated that the first
stage of the reactor was not operating properly. However, in the second stage no problem was observed. For
this purpose, the influent COD concentration was
increased up to 33 866 mg/l in the first stage of the
UASB reactor system. The previous dilutions of wastewater applied to the system were prepared with tap
water. However, for the 33 866 mg/l influent COD
concentration in the first stage of the UASB reactor
system a dilution was prepared with BM as a nutrient
support to the system due to deterioration of the
granular culture in the first stage.
In the second stage of the reactor no negative effect
was observed due to the increase in the influent COD
concentration of the first stage of the UASB reactor up
to 33 866 mg/l. On day 65, the HRT and OLR of the first
and second stage of the UASB reactor system were 13.8
h and 36.3 kg/m3 day and 13.8 h and 4.7 kg/m3 day,
respectively. The COD removal efficiencies of the first
stage and second stage of the UASB system were 87 and
70% for the 20 920 and 2693 mg/l influent COD
concentrations, respectively. On day 82, the HRT and
OLR of the first and second stage were 49.3 h and 10.2
kg/m3 day and 49.3 h and 11 kg/m3 day, respectively.
COD removal efficiencies of the first stage and second
stage of the UASB system were 34 and 91% for the
33 866 and 22 500 mg/l influent COD concentrations,
respectively. The influent pH values of the system were
between 6.2 and 7.86 and the effluent pH values were
between 5.25 and 9.38. Up to 11 087 mg/l influent COD
concentration in the first stage. The alkalinity added to
the influent was 1190 mg/l (as CaCO3) but when the
influent COD concentration increased up to 11 087 mg/l
alkalinity concentration was not sufficient and increased
to 3571 mg/l (as CaCO3). During the operational period
and in spite of some operational disorders no problem
was observed in the alkalinity and VFA concentrations
in the second stage of the system.
For the overall system of the two-stage UASB
reactors, on day 54, HRT and OLR of the system
were 29.2 h and 17.2 kg/m3 day, respectively. COD and
BOD removal rates were 92 and 98% for the influent
concentration of 20.92 g COD/l. On day 84, HRT and
OLR of the system were 25.8 h and 19.4 kg/m3 day,
respectively. COD and BOD removal rates were 96 and
99% for the influent concentration of 33.86 g COD/l.
Effluent TKN and phosphorus concentrations were
higher than influent TKN and phosphorus concentrations. High TKN and P values observed in the effluents
were evidently due to excessive column bleed at high
OLRs. On day 30 influent and effluent TKN and
phosphorus concentrations in the first stage of the
UASB reactor system were 6.4 and 25.3 mg/l and 19.9
and 49.8 mg/l and in the second stage of the UASB
285
BOD Rem%
N. Uzal et al. / Process Biochemistry 39 (2003) 279 /286
286
N. Uzal et al. / Process Biochemistry 39 (2003) 279 /286
reactor system were 25.3 and 61.4 mg/l and 49.8 and
72.3 mg/l, respectively.
The two stage UASB reactor experiments proved that
a two stage UASB reactor configuration was efficient
for malt whisky wastewater treatment. Up to 33 866 mg/
l influent COD concentration the first stage of the
UASB reactor was operated efficiently. When 33 866
mg/l COD concentration was applied the black color of
the granular culture of the first stage UASB reactor was
changed to a brownish color and the granular culture
deteriorated. This was most probably due to the
acidogenic culture taking over the first stage and
dominating over the methanogenic culture.
3.3. Batch aerobic experiments
The batch aerobic reactors were operated for 15 days.
Effluent COD was measured on days 0, 1, 6, 10, 15, and
BOD was measured on days 0, 10, 15.
On day 15, the effluent COD concentrations were 649
mg/l, as opposed to the influent 1476 mg/l. The BOD
effluent concentrations were 90 mg/l at this day versus
323 mg/l on day 1. The COD and BOD removal
efficiencies were 55 and 70%, respectively.
During anaerobic treatment COD and BOD removal
efficiencies for the influent COD concentrations of
33 866 mg/l were 96 and 98%, respectively (Table 2).
During aerobic treatment COD and BOD removal
efficiencies were 55 and 70%, respectively. The COD
and BOD concentrations, after aerobic treatment,
decreased to 641 and 38 mg/l, respectively. Therefore,
the overall COD and BOD removals in the anaerobic
and aerobic treatment stages collectively were 98 and
99.5%, respectively.
4. Conclusions
The results of the BMP experiments conducted both
in the presence and absence (only alkalinity addition) of
nutrient supplementation revealed that:
. Malt whisky wastewater with initial COD concentrations of 5.07, 10.14, 15.21 g COD/l could be treated
anaerobically.
. Net total gas production values in a nutrient supplemented set of anaerobic batch reactors were higher
than without supplementation, especially at the highest concentrations of 15 210 mg/l. The delay in gas
production observed for the no-nutrient set of
reactors was not observed for the nutrient supplemented set. The delay in gas production (or acclimation phase) for the first set of anaerobic batch
reactors was, therefore, thought to be due to lack of
nutrients.
The results of the continuous reactor experiments
performed in staged UASB reactors revealed that:
. A two-stage UASB reactor configuration was efficient for malt whisky wastewater treatment even at
OLRs as high as 39 kg/m3 day.
. A phase separation was observed beyond influent
COD concentrations of 20 920 mg/l.
. High TKN and P values were observed in the effluent
of the UASB system which were evidently due to
excessive column bleed at high OLRs in all continuous reactor experiments.
For the overall sequential system (anaerobic/aerobic)
treatment COD and BOD removal efficiencies were 99.5
and 98.1%, respectively, for the treatment of malt
whisky wastewater.
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