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International Conference on Ecological, Environmental and Biological Sciences (ICEEBS'2012) Jan. 7-8, 2012 Dubai
Degradation of Nitrophenol in Water By
Sequential Anaerobic-Aerobic Treatment
Basavaraju Manu and Mohammed Yaseen
Nitrophenols must be treated to get rid of them before their
safe disposal. In general biological treatment techniques are
economical and efficient for degrading various kinds of
organic compounds. The mineralization of recalcitrant
pollutants has been possible by using the integrated or
sequential anaerobic-aerobic treatment [2]. Some toxic
compounds that are difficult to remove in an anaerobic or
aerobic environment, can be biotransformed coupling both the
anaerobic process to the aerobic one [3]. Sequential anaerobic
and aerobic treatment are the most efficient methods of waste
water because of its advantage like high quality effluent at
varying loads, reduction in space, few mechanical parts and
power savings due to lower oxygen requirements while its
limitation is its batch operation mode, requiring on and off of
influent feed, aeration and effluent decanting controls.
An enzymatic approach has attracted much interest in the
remediation/degradation of various organic pollutants present
in the wastewater coming out of industries. The treatment of
several pollutants sometimes causes problems due to the
recalcitrant nature of the compounds. However, these
recalcitrant compounds were degraded/transformed by
enzymes in the presence of certain redox mediators. These
redox mediators enhanced the range of substrates and
efficiency of degradation of the recalcitrant compounds by
severalfold. Use of the enzyme-redox mediator system
certainly will enhance the chances of remediation of a wide
spectrum of aromatic compounds present in various industrial
effluents. Hence in the present study sequential anaerobicaerobic treatment of nitrophenol containing solution has been
carried out.
Abstract— In the present study, sequential anaerobic-aerobic
degradation of nitrophenol in simulated wastewater has been
evaluated. Nitrophenol are used as intermediates in the manufacture
of pesticides, dyes, etc. Nitrophenols are reported to have ill-effects
on aquatic flora and fauna when discharged untreated. Hence
wastewater containing Nitrophenols must be treated to get rid of
them before their safe disposal. In general biological treatment
techniques are economical and efficient for degrading various kinds
of organic compounds. Three identical anaerobic and two identical
aerobic reactors were operated at 24 hours hydraulic retention time
(HRT) for a period of more than 180 days to study the nitrophenol
degradation efficiencies. Simulated wastewater containing 2Nitrophenol (2-NP) and 2,4-Dinitrophenol (2,4-DNP) concentrations
varying from 0-40 mg/L was fed to the anaerobic reactors and the
treated effluent was fed to the aerobic reactors for the sequential
aerobic step. The performance of the reactors was assessed by
monitoring COD, pH, ORP and nitrophenol concentration in both
influent and effluent. Nitrophenol degradation efficiencies of upto
100% were observed under the experimental employed in the present
study.
Keywords— Aerobic, Anaerobic, Nitrophenol, Sequential
treatment
I. INTRODUCTION
Phenolic compounds have been listed as priority pollutants
by the Ministry of environment and Forests, Government
of India and EPA, United States of America (USA). Phenolic
compounds are the major organic constituents found in
effluents of coal conversion processes, coke ovens, petroleum
refineries, phenolic resin manufacturing, herbicide
manufacturing, fiber glass manufacturing and petrochemicals.
Phenol compounds are toxic, carcinogenic, mutagenic, and
teratogenic. Industrial use of phenol and its derivatives over
the past decades has led to severe environmental pollution. In
Andhra Pradesh (South India) a total of 6884 tonnes of waste
is generated per month, of which 190.3 tonnes constitute
phenolic wastes disposed by petrochemicals, pharmaceuticals
and polymer industries [1]. Hence wastewater containing
II. MATERIALS AND METHODS
A. Materials
The experiments were performed using five bench-scale
SBR reactors (R1, R2 R3, R4 and R5) having a working
volume of 3 litres for anaerobic phase and 1.5 litres volume
for aerobic phase respectively o study the nitrophenol as well
as organic substrate removal. Microbial inoculum (seed
sludge) used was cowdung in slurry form is used as the
seeding material for developing nitrophenol removal
organisms.
All Chemicals were obtained from MERCK Chemicals of
analytical grade. Chemical structures of 2-Nitrophenol (2-NP)
and 2,4-Dinitrophenol (2,4-DNP) are given in Fig 1.
Basavaraju Manu is with the National Institute of Technology Karnataka,
Surathkal, 575025 India (corresponding author to provide phone: +91-8249342036198;fax:+91-824-2474033;e-mail:[email protected]).
Mohammed Yaseen, was with NITK, Surathkal Karnataka, India 575025
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International Conference on Ecological, Environmental and Biological Sciences (ICEEBS'2012) Jan. 7-8, 2012 Dubai
of 280 nm and 2, 4 DNP was analyzed for 400 nm
III. RESULTS AND DISCUSSION
2-NP
Quasi-steady state conditions were achieved in the
anaerobic reactors in 45 days during the start-up phase where
COD removal efficiencies were 65%. For 5 consecutive
feedings. On 46th day onwards nitrophenols were fed to the
reactors with 5 mg/L during initial stage. 2-NP and 2,4 DNP
removal efficiencies observed during the study period are
summarized in Table 1 and Table 2. From the Tables 1 and 2,
it can seen that the nitrophenol removal for 5 mg/l of 2NP was
80% for 2,4 DNP it was 75%,for 10 mg/l of 2 NP it was
80%,for 2,4 DNP it was 78%,for 20 mg/l of 2NP it was
70%,for 2,4 DNP it was 65%,for 40 mg/l of 2NP it was 64%
for 2,4 DNP it was 62%.
2,4-DNP
Fig.1 Chemical structures of 2-NP and 2,4-DNP used in the
present study
B. Experimental Methodology
A bench scale SBR with working volume of 3 litres for
anaerobic phase was seeded with 1.5 litres of cowdung in the
beginning glucose, sodium bicarbonate and other nutrients 2
to 3 ml/l was feed with one litre influent water daily.
Simultaneously aerobic phase of reactors in also seeded with
0.5 litre of cowdung slurry and feed with same influent as
above till the start up of reactors which was 45 days for
anaerobic phase and 25 days for aerobic phase respectively.
Trace metals solution was prepared in distilled water by
dissolving 5 g MgSO4.7H2O, 6 g FeCl2.4H2O, 0.88 g
CoCl2.4H2O, 0.1 g H3BO3, 0.1 g ZnSO4 .7H2O, 0.05 g
CuSO4. 5H2O, 1 g NiSO4.8H2O, 5 g MnCl2. 4H2O and 0.64
g (NH4)6Mo7o24 . 4H2O in 1 L distilled water [4]. After the
start up nitrophenols are loaded in the increasing
concentrations from 5 mg/l to 40 mg/l monitoring each
concentration for 15 days. The SBR used during the study was
operated started for 24 hrs HRT and SRT of 900 days through
sequences of fill, react settle and draw (decant).
In the next step 2 aerobic reactors are started up using the
same seed as cow dung of 0.5 litre volume along with 1 gm of
glucose and 1 gm of sodium bicarbonate solution daily till the
start up which took 25 days.
In the next step the performance of reactor was monitored
under 4 different nitrophenol loadings of 5, 10 20 and 40 mg/l
and each concentration is monitored for 15 days with
nitrophenol and COD removal efficiencies.
Table 1 QUASI STEADY-STATE 2-NP REMOVAL EFFICIENCIES
OBSERVED DURING THE STUDY PERIOD
Initial Nitrophenol
Concentration (mg/L)
2- Nitrophenol Removal Efficiencies
(%)
After
After Aerobic
Anaerobic
Treatment
Treatment
80
80
70
64
5
10
20
40
100
100
100
70
Table 2 QUASI STEADY-STATE 2,4-DNP REMOVAL EFFICIENCIES
OBSERVED DURING THE STUDY PERIOD
Initial Nitrophenol
Concentration (mg/L)
5
10
20
40
C. Analytical Procedure
I The samples were collected for the analysis of various
parameters at the end of anaerobic and aerobic phases of the
SBR as well as influent and effluent of the batch Reactor.
During Continuous monitoring in a cycle, samples were
collected every 24 HRS and analyzed for the various
parameters
All the Samples were filtered before analysis and were
analyzed for pH, COD, Alkalinity, ORP, MLSS, MLVSS and
Nitrophenols in accordance with the Standard Methods [5].
pH was measured by glass electrode pH meter, COD by
Closed Reflux Colorimetric Method, Alkalinity by Titrimetric
Method, and ORP by Glass Electode-Calomel Electrode
Method.
Nitrophenols was analyzed by Cintral UV-VIS
Spectrophotometer. 2Nitrophenol was analyzed at wavelength
2,4-Di Nitrophenol Removal
Efficiencies (%)
After
After Aerobic
Anaerobic
Treatment
Treatment
75
78
65
62
100
100
100
65
AS the concentration of pollutant increases the removal
efficiency decreased gradually due to the toxic effect on the
biomass. for the Sequential Aerobic Reactors it can seen that
the NP Removal for 5 mg/l,10mg/l and 20 mg/l for both 2NP
and 2,4 DNP was 100%,but for 40 mg/l of 2NP it was 70%
and for 2,4 DNP it was 65%. Influent alkalinity was in the
range of 1000 mg/l to 1800 mg/l and Effluent alkalinity was in
the range of 500 mg/l to 2300 mg/l
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International Conference on Ecological, Environmental and Biological Sciences (ICEEBS'2012) Jan. 7-8, 2012 Dubai
containing water/wastewater.
70
COD Removal Efficiencies (%)
60
REFERENCES
[1]
D. Sreekanth, D. Sivaramakrishna, V. Himabindu, Y. Anjaneyulu,
Thermophilic degradation of phenolic compounds in lab scale hybrid up
flow anaerobic sludge blanket reactors, Journal of Hazardous Materials,
vol. 164 no. 2-3, pp 1532–1539, 2009.
[2] Zitomer D.H., Speece R.E.. Sequential environments for enhanced
biotransformation of aqueous contaminants. Environ. Sci. Technol. 27, pp
227–244, 1993.
[3] Field J.A., Stams A.J.M., Kato M. Schraa G. Enhanced biodegradation of
aromatic pollutants in cocultures of anaerobic and aerobic bacterial
consortia. Antoine Van Leeuwenhoek, 67, pp 47–77, 1995.
[4] B Manu, Sanjeev Chaudhari, Anaerobic decolorisation of simulated textile
wastewater containing azo dyes, Bioresource Technology, vol 82, no 3,
pp 225-231, 2002.
[5] APHA, Standard Methods for the Examination of Water and Wastewater,
17th ed. American Public Health Association, Washington, DC, 2005.
50
40
30
2-NP
20
2,4-DNP
10
0
0
5
10
15
20
25
30
35
40
45
Nitrophenol Conc. (m g/L)
Fig1. Quasi steady-state COD removal efficiencies observed in the
anaerobic treatment during the study period
From the Fig 1 it can be seen that in anaerobic Reactors
COD Removal with Reference to Control Reactor for 5 mg/l
for 2NP as well for 2, 4 DNP was 65%, for 10 mg/l it was
65% for 20 mg/l for 2NP, it was 65%, for 2, 4 DNP, was 60%
and for 40 mg/l for 2NP it was 55% and for 2, 4 DNP it was
50%.
100
COD Removal Efficiencies *%)
90
80
70
60
50
40
2-NP
30
2,4-DNP
20
10
0
0
10
20
30
40
50
Nitrophenol Conc. (m g/L)
Fig 2 Quasi steady-state COD removal efficiencies during
sequential aerobic treatment of the study period
Similarly from the fig 2 for the Sequential Aerobic reactor
COD Removal for 5 mg/l for 2NP it was 95% for 2,4DNP it
was 90 %, for 10 mg/l of NP it was 85 %, for 2, 4 DNP it was
80 %, for 20 mg/l for 2NP, it was 80%,for 2,4 DNP also it
was 80% and for 40 mg/l for 2NP it was 65% and for 2,4
DNP it was 60%. And it can be seen that as the concentration
of pollutant increases the removal efficiency decreased
gradually due to the toxic effect on the biomass.
IV. CONCLUSION
In the present study sequential anaerobic-aerobic treatment
of nitrophenol containing water has been carried out. Efficient
degradation of upto 100% of 2-NP and 2,4-DNP was
observed. Hence it seems that sequential anaerobic-aerobic
treatment may be sutiable for treatment of nitrophenol
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