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Anaerobic fixed film biotreatment of dairy wastewater
Article in Middle East Journal of Scientific Research · January 2011
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Middle-East Journal of Scientific Research 8 (3): 590-593, 2011
ISSN 1990-9233
© IDOSI Publications, 2011
Anaerobic Fixed Film Biotreatment of Dairy Wastewater
1
Javed Iqbal Qazi, 2Muhammad Nadeem, 3Shagufta S. Baig,
2
Shahjahan Baig and 2Quratulain Syed
1
Department of Zoology, University of the Punjab, Lahore-54590, Pakistan
2
Food and Biotechnology Research Centre, PCSIR Labs. Complex, Lahore-54600, Pakistan
3
Environment Protection Department, Punjab, Opposite LCCA Ground, Lahore, Pakistan
Abstract: A number of biofilm support media including foam cubes, bamboo rings, fire bricks, PVC rings and
gravels were employed to immobilize biomass for reduction in BOD5, COD and VSS of dairy wastewater in batch
and repeated batch cultivation systems. The efficiency of COD removal is associated with the nature and
properties of support material. Eventually, the maximum percentage removal of COD, BOD5 and VSS turned out
to be as 96 %, 93 % and 90 %, respectively, with the application of 21 Kg COD/m3/d loading in batch reactor
filled with gravels. Subsequently, the dynamics of repeated batch was evaluated in three cycles that indicated
that almost 89% reduction of volatile suspended solids (VSS) occurred after 12 d hydraulic retention time (HRT)
in each cycle. These results provide a suitable biotreatment process for high conversion of organic fraction to
combustible methane gas.
Key words: Waste water COD Waste water BOD5 methane production Volatile suspended solids
INTRODUCTION loading capacity of any biological wastewater treatment
system is essentially directed by the amount of active
Water management in dairy industry is well biomass retained in the reactor providing a sufficient
documented but suitable disposable of effluents in contact between active biomass and organic waste.
waste water remains a challenging issue for dairy Therefore, high rate anaerobic reactors are those which
industry. Anaerobic treatment of organic fractions of retain biomass for periods longer than the hydraulic
agro-industrial wastewater is an attractive process in retention time. In addition to lowering the capital cost of
sustainable approach [1-3]. Anaerobic treatability a waste treatment process, the generation of CH 4 gas as a
depends on the type of wastewater and the microbial by-product is a supplementary economic motivation for
consortium employed in the process which together the utilization of anaerobic digestion for wastewater
determine as to what extent it should be treated [4-6]. treatment [13]. This paper reported results of the effects of
The composition of dairy industrial wastewater dairy waste strength on the performance of batch and
corresponds to organic and inorganic constituents of repeated batch reactors with the application of different
milk. In ice-cream factories, spillage can be a major source packing media to facilitate high rate anaerobic digestion
of effluent strength because of the original organic in fixed film growth process.
concentration of ice-cream which includes milk fat,
vegetable oils, non-fat milk solids, sugars, fruits and MATERIALS AND METHODS
colorings [7,8]. Other components in dairy wastewater are
cleaners and sanitizers. These organic fractions, Inoculum Development: About 300 g fresh sewage sludge
persistent in dairy waste water, are efficiently degraded was collected from main outfall of Lahore city, Pakistan
into simple compounds by anaerobic bacteria [9]. and dried at 105°C in an oven. Approximately 100 g oven
The interest in anaerobic reactors has increased dried sewage was suspended in 300 mL distilled water in
rapidly with the realization that cost-effective anaerobic one liter saline bottle. The suspension was then sparged
treatment is generally not possible without some form of with a mixture of N2 and CO 2 gases (3:1) for 5 min to
biomass retention [10-12]. It is further added that the create anaerobic conditions at ambient temperature and
Corresponding Author: Muhammad Nadeem, Food and Biotechnology Research Center, PCSIR Labs. Complex,
Lahore-54600, Pakistan. Tel: +92-42-9230689.
590
Middle-East J. Sci. Res., 8 (3): 590-593, 2011
Table 1: Characteristics of dairy wastewater media employed in Support materials used for immobilization of bacterial
biotreatment.
population is given in Table 2. Each reactor material was
Parameters Characteristics/ values
sealed with rubber stopper facilitated with thermometer,
Color Turbid grey - Dark brown
gas measuring system, gas sampling port and Hg
Odor Sewage like
PH 7.2 - 7.5 manometer to measure gas pressure over the surface of
Total solids 8,000 - 10,000 mg/L the liquid. The bioreactor temperature was maintained at
Dissolved solids 72,000 - 80,000 mg/L 35±0.5°C by circulating thermostatically controlled water
Volatile suspended solids 800 - 1000 mg/L around the vessel through the jacket of rubber tubing,
COD 2,500 - 3,000 mg/L
thoroughly insulated with glass wool pads to minimize the
BOD5 1,300 -1,600 mg/L
heat loss. Each bioreactor was also covered with black
Fat and Oil 20 -70 mg/L
plastic sheet to protect it from the bacterial
Table 2: Dimensions of various packing media used in fixed film bioreactor photosynthesis and algal growth during cultivation
for the treatment of dairy waste water operation. A mixture of N2 and CO2 gases (3:1) was
Materials Diameter (mm) sparged in the culture vessel for 10 min to create
Bamboo rings 10.0 anaerobic conditions prior to inoculation with enriched
PVC rings 5.0 culture of mixed population of methanogenic bacteria. The
Foam cubes 15.0
samples of the treated effluent were taken from the bottom
Firebricks 15.0
Gravels 8.0
of the reactor through drain line.
In the repeated batch process, 80% v/v treated waste
was replaced with fresh medium based on initial
concentration of volatile suspended solids (VSS).
However, each cycle of the repeated batch was terminated
after 12d hydraulic retention time (HRT). The
characteristics of wastewater and packing material used in
the treatment studies are shown in Tables 1 &2.
RESULTS AND DISCUSSION
The nature of wastewater discharged from dairy
industries varies throughout the working day. The
present study has been performed using batch and
repeated-batch test techniques which provide a quick and
easy assessment of attached active biomass.
Fig. 1: Schematic diagram of Anaerobic Bio-treatment
Fig. 2 compares the percentage reduction in COD in
System
batch-wise attached growth processes. In these
experiments, the organic load was kept constant at 2Kg
inoculated with 5% v/v culture broth prepared in low
COD/m3/d, while the HRT was progressively increased
phosphate buffer medium (LPBM), containing mixed
from 1 to 8 days. It can be seen that substantial amount of
population of methanogens isolated from cow dung, as
COD was reduced (72%) in reactor packed with fire bricks
described by Bryant [14]. The inoculated sewage sludge
after 6 days HRT. Similarly, foam cubes exhibited efficient
was incubated at 35±0.5°C for 7 days in an anaerobic jar.
removal (46%) of COD within 6 days. The percentage
The developed mixed methanogenic bacterial population
removal of oxidizable material was optimal at 6 day HRT,
was utilized (5% v/v) as an active inoculum in the
in the presence of fire bricks, foam cubes, PVC rings or
biotreatment studies.
gravels. In general an increase in HRT caused a
corresponding increase in COD reduction up to forth
Biotreatment Process: Dairy waste water (Table 1) was
sampling period. It is also apparent from these
anaerobically treated by batch and repeated batch
experiments that the efficiency of COD removal is
processes with the application of certain growth
associated with the nature and properties of support
supporting material individually in glass aspirator of 10 L
material involved in the attachment of biomass.
capacity used as bioreactor with working volume of 6L
It can be categorized as follow: fire bricks>gravels >foam
(Fig. 1).
591
Middle-East J. Sci. Res., 8 (3): 590-593, 2011
(a)
Fig. 2: Influence of hydraulic retention time on reduction
of dairy wastewater COD using different suport
media in batch reactors
(b)
Fig. 3a: Influence of organic laoding on reduction of
COD, BOD5 and VSS of dairy effluents using
fixed-film growth process in batch reactor packed
with fire bricks
(c)
Fig. 4: Repeated batch biotreatment of dairy waste
water
a: First cycle, b: Second cycle and c: Third cycle
Figure 3a shows the relationship between BOD5,
COD and VSS determined in the presence of
different organic loadings ranging between 12 to
27 Kg COD/m3/d. The computed values indicated
Fig. 3b: Influence of organic laoding on production of that biodegradation of organic matter in terms
methane and carbon dioxide gases using dairy of COD, BOD5 and VSS was progressed in
effluents in fixed film batch reactors packed with sufficient quantities. Despite these gradients,
fire bricks variation in gas yield was also proportionate of
degradation frequency (Figure 3b). It appears that
cubes>PVC rings>bamboo rings. In addition, the maximum percentage removals of COD, BOD and
performance of support material might be attributed to VSS achieved were around 90% levels, with the
chemical properties interlinked with its physical application of 21Kg COD/m/day loading in batch
properties. Eventually, fire bricks were utilized as an reactor. In addition, a substantial gas evolved
effective support material in subsequent studies constituting 67% methane incorporating 33%
conducted both in batch (Fig. 3a & b) and repeated batch CO2 with the expense of 0.35/m3/Kg of COD
reactors (Fig. 4). (Figure 3b).
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Middle-East J. Sci. Res., 8 (3): 590-593, 2011
Hydrodynamic of a semi-continuous fixed growth 7. Switzenbaum, M.S. and S.C. Danskin, 1982.
process was subsequently evaluated by repeated- Anaerobic expended bed treatment of whey.
batch system (Figure 4). In fact, the system was Agricultural Wastes, 4: 411-426.
based on three cycles; each cycle terminated after 8. Zellner, G., P. Vogel, H. Kneifel and J. Winter, 1987.
12day detention. The performance of first growth Anaerobic digestion of whey and whey permeate
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In conclusion material used for packing provided a digestion of high strength acidic whey in a pH-
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