SEQUENCING BATCH REACTOR TECHNOLOGY
FOR THE TREATMENT OF COMPLEX CHEMICAL
PROCESS WASTEWATER
Synopsis of the Thesis Submitted to
NATIONAL INSTITUTE OF TECHNOLOGY
WARANGAL
For the award of the degree of
DOCTOR OF PHILOSOPHY
IN CHEMISTRY
BY
N. CHANDRASEKHARA RAO
Bioengineering and Environmental Center
Indian Institute of Chemical Technology
Hyderabad- 500 007, INDIA
NATIONAL INSTITUTE OF TECHNOLOGY
(DEEMED UNIVERSITY)
WARANGAL- 506 004, INDIA
February 2005
Synopsis
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Industrial wastewater originating from chemical industries normally contains toxic
organic compounds, solvents, inorganic chemicals, salts, etc. and the characteristics of
wastewater are highly variable and complex in nature [1-3]. The consumption of large
quantities of organic and inorganic chemicals in the process imparts low biodegradability
to the wastewater and the presence of recalcitrant organic molecules due to their nonbiodegradable nature inhibits the biological process. Excessive usage of inorganic salts in
the process results in high salt concentration in wastewater, thereby inhibiting the
biological treatment process due to plasmolysis and/or loss of biological activity. The
complexity of the wastewater is characterized by the presence of toxic/recalcitrant
organic compounds, solvents and inorganic chemicals [3]. Presently there are over 70,000
synthetic organic chemicals termed as refractory compounds, which are difficult to treat,
by conventional biological processes owing to the inhibition and toxicity of these
compounds when they serve as microbial substrates. The variability of the wastewater on
both flow and composition (change of manufacturing product, transitory operation of the
plant, washing, etc.) also influences the efficiency of the treatment [3]. Treatment of this
wastewater is of great concern to the scientists working in the field of environmental
pollution control and the existing stringent environmental regulations need effective
treatment methodologies for the wastewater to meet the regulatory norms.
The
biological treatment of complex chemical process wastewater is particularly challenging
due to their low biodegradable nature and transient flow conditions. Efficiency of the
biological process to treat wastewater containing toxic and recalcitrant compounds
depends on the presence of appropriate microorganisms, system acclimatization and
specific operational conditions of the bioreactor.
Continuous flow biological systems such as activated sludge process have serious
difficulties in treating this type of wastewater. Effective biological transformation of
complex industrial wastewater requires the activity of microbial communities with vast
metabolic ranges [4]. Complex synergistic and antagonistic relationships exist between
the various microbial species present and the microbial species forming the community
can differ greatly in growth rate and yield. This is especially evident when the organisms
are to be selected and enriched wherein their physiological states will be adjusted in an
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environment alternating between aerobic, anoxic and anaerobic conditions. The
maintenance of robust population capable of meeting the desired effluent limits is further
exacerbated when transient or shock load conditions occur.
Recently, considerable interest in the research fraternity is observed in the application of
alternative approaches like periodic discontinuous processes for wastewater treatment.
Periodic discontinuous process was developed on the basic scientific assumption that
periodic exposure of the microorganisms to defined process conditions is effectively
achieved in a fed batch system wherein exposure time, frequency of exposure and
amplitude of the concentration can be set independently of any inflow condition [4]. This
process is distinguished by the enforcement of controlled short-term unsteady state
conditions, leading in the long run to a stable steady state with respect to composition and
metabolic properties of the microbial population growing in the reactor leading to the
control of the distribution and physiological state of the microorganisms. Systems
submitted to conditions of feast and famine have higher specific growth rates and
saturation constants than systems with constant conditions. In biological processes,
intermittent process has been shown to produce higher specific growth rates of bacteria.
The concept of periodic discontinuous process using sequencing batch reactor (SBR)
operation was first reported in 1983. Application of this technology for domestic
wastewater treatment especially for the removal of nutrient was documented after 1994
onwards [4-10].
SBR technology differs in various ways from conventional technologies used in
biological treatment of wastewater. The most obvious difference is that in SBR
technology, the reactor volume varies with time, where as it remains constant in the
traditional continuous flow system. The advantages of SBR technology include the
flexibility of operation (change of phase), feasibility of operation at low retention time,
control over microbial population and various reactor configurations. SBR process
consists of several time oriented periodic steps, characterized by a series of process
phases viz. fill, react, settle, decant and idle, each lasting for a defined period during
which wastewater is treated. The success of SBR technology depends on the great
potential provided by the possibilities of influencing the microbial system in the reactor.
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SBR processes are comparatively easy to operate and cost efficient and this process saves
more than 60% of the expenses when compared to conventional activated sludge process
[5].
Interest has been growing across the world both in scientific research and in practical
application of SBR technology. SBR with various reactor configurations for nutrient
removal has been studied extensively. One of the main advantages of SBR is the
enhanced phosphorus removal due to phosphate accumulation during the anaerobic
process and utilization in the subsequent aerobic process of the sequence. So far, SBR has
been successfully applied for the treatment of domestic wastewater, medium and lower
strength landfill leachates, specific pollutants and contaminated soils. Very few
applications of SBR for industrial wastewater treatment (dairy, tannery, swine, etc.) were
reported in the literature [11-23]. A thorough literature search revealed that SBR
technology has not been investigated with complex chemical wastewaters from
pharmaceutical, drug and chemical process units.
In this context, the research work in the thesis focused on the investigation of periodic
discontinuous process using sequencing batch reactor (SBR) application especially for
the treatment of complex chemical wastewater. The experiments conducted in this have
been selected, performed and analyzed with the ultimate goal of optimizing the SBR
process with respect to metabolic functions, sequence phase microenvironment and
reactor configuration. More specifically an depth attempt has been made to correlate the
various reactor performance parameters to arrive at the best possible configuration for
achieving process optimization.
The work was taken up with the following broad
objectives

To investigate the application of periodic discontinuous process using sequencing
batch reactor (SBR) technology for treating complex chemical wastewaters.

To enumerate the relative efficiency of various reactor configurations such as
suspended growth, biofilm, granular, immobilized and granular activated carbon
(GAC)

To elucidate the role of various metabolic functions (aerobic and anaerobic) on
the process performance
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
To investigate the influence of metabolic shift on the process performance

To elicit the multiphase microenvironment/redox condition variation on the
process performance during sequence phase operation.

To elucidate the application of Taguchi dynamic design of experimental (DOE)
methodology for optimization of anaerobic process

To explore the effect of bioaugmentation strategy to enhance the process
performance.
The thesis is divided into eight chapters. The schematic representation of the thesis with
respect to chapters is shown in Figure 1.
Chapter 1: Introduction
This chapter introduces the problem of complex wastewater treatment by biological
processes and stresses the need for the alternative biological methods for effective and
enhanced process performance. This chapter also presents the global scenario and
conceptual framework of the thesis topic. Literature on the chemical process industries
especially with process variations and wastewater generation along with the present state
of biological methods used for the treatment of such kind of wastes are discussed. The
concept of periodic discontinuous process operation and sequencing batch reactor
technology are critically reviewed. Description of the basic process with the theoretical
concepts of periodic discontinuous process along with operational steps involved and
process variations forms part of the chapter. Various process variations normally
observed
in
SBR
operation
such
as
metabolic
functions,
sequence
phase
microenvironment and reactor operating conditions are discussed in detail. The design
normally adopted for SBR process and critical factors to be considered during the design
are enumerated. Relative advantages of periodic discontinuous processes operation with
traditional/continuous processes are comparatively evaluated. Scope and flexibility of
SBR operation and its application for the treatment of wastewater such as domestic
sewage, landfill leachates, industrial wastewater and specific pollutants are reviewed.
Concepts of bio-nutrient removal, decolorisation of dye and soil decontamination by
slurry phase bioreactors with respect to SBR technology are also included in this chapter.
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Figure 1: Schematic diagram of the thesis presentation
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Chapter 2: Scope and objective of the study
This chapter outlines the scope and the objectives of the present work.
Chapter 3: Experimental Methodology
Chapter 3 describes in detail the materials used in the experiments along with the
experimental methodology adopted in the study for achieving the specified objectives of
the work. Details of wastewater used as feed for treatment and its characteristics, reactor
design and fabrication procedures adopted and analytical methods used for monitoring
the biological process are discussed in detail. The experimental details such as reactor
configurations, metabolic functions and sequence phase variations, reactor operation,
sampling protocols, etc are incorporated in this chapter. The feasibility of SBR
technology is investigated with three kinds of complex chemical wastewater i.e.
composite chemical wastewater (CCW), single process chemical wastewater (SPCW) and
simulated azo dye wastewater (SDW) for assessing the process efficiency. Reactor
configurations such as suspended growth, granular, biofilm, GAC biofilm, immobilized
and hybrid are investigated to understand their relative efficiency in treating the complex
wastewater in periodic discontinuous operation.
Chapter 4: Chemical Wastewater Treatment by Periodic Discontinuous Process
using Sequencing Batch Reactor (SBR) Technology: Reactor Configuration and
Metabolic Function Optimization
This chapter presents experimental data pertaining to complex chemical wastewater using
various configurations of SBRs using aerobic and anaerobic metabolic functions along
with detailed discussions. A total of eight reactor configurations with aerobic and
anaerobic metabolic functions were designed for carrying out detailed experiments for
the treatment of CCW. Further, the selected effective reactor configuration was studied
with two other types of chemical wastewater for assessing the reactor performance in
detail. The experimental data has been organized according to various experimental
phases that, in turn, approximately follow the chronological order in which they are
conducted. The discussion was mainly focused on the reactor performance with respect to
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substrate degradation rate (SDR) with the function of organic loading rates (OLRs)
studied and compared with corresponding continuous mode systems. The process
performance of individual reactor configuration was monitored and evaluated for every
reactor. The experiments revealed the process efficiency of periodic discontinuous
processes in treating complex chemical wastewater compared to continuous flow
systems. Significant enhancement in substrate degradation rate in a rapid retention time
(24 hours) is observed in SBR reactor operated with suspended growth mode (anoxicaerobic-anoxic) compared with continuous mode operated activated sludge process
(retention time-5 days). GAC configured aerobic SBR system showed enhanced
performance over corresponding suspended growth system.
Reactor operated with
immobilized (entrapped acclimatized aerobic mixed consortia) configuration in SBR
mode resulted in 70% of COD removal, which is comparatively on the higher side of the
corresponding suspended growth system. Overall, biofilm configured SBRs irrespective
of metabolic function exhibited effective performance over other configurations studied.
Also, bioflm systems resulted in high SDR, while suspended growth systems showed
inhibition to system operation after an organic loading rate of 3.5 Kg COD/cum-day.
Experimental data revealed that the efficiency of aerobic metabolic functions over the
corresponding anaerobic systems studied. This may be reasoned due to the fact that, the
SBR operated has relatively less retention time to accomplish anaerobic reaction treating
complex chemical wastewater. Other than suspended growth system, the remaining
configurations studied retained the substrate removal efficiency at higher OLRs.
However, hybrid configuration with biofilm integrated immobilized (anaerobic mixed
consortia) resulted in effective performance with respect to substrate degradation.
Sulphate reduction of about 10% was evidently observed in aerobic SBR operation,
which may be attributed to the prevailing anoxic conditions in the sequence/cycle phase
operation.
consistently.
In the case of anaerobic operation, 70% sulphate reduction is noticed
Overall, the SBR configurations studied for the treatment of CCW
exhibited the performance efficiency in the order of
Biofilm (aerobic) > Immobilized (aerobic) > GAC (aerobic) > Biofilm (anaerobic) >
Immobilized (anaerobic) > Granular/suspended (anaerobic) > Suspended (aerobic).
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Among the metabolic functions studied, aerobic systems showed effective performance
over the corresponding anaerobic systems in case of CCW and SPCW wastewater. In
case of SDW, anaerobic processes are more favored and yield maximum substrate
removal compared to the corresponding aerobic system. This may be attributed to the fact
that azo dye initial breakdown needs anaerobic environment. The results obtained with
CCW indicated that the biofilm configured SBR showed effective performance compared
to other configurations studied and subsequently experiments with SPCW and SDW were
carried out with biofilm systems operated in SBR mode. Experiments with SPCW are
investigated at higher organic loading rates (up to 14.76 Kg COD/cum-day) with 24
hours of retention time. At higher organic loading rate, biofilm configured system
resulted in 60% of COD removal along with 88% of BOD removal without any system
inhibition. In the case of SDW, complete removal of dye color is observed for all the
SBR variations studied. However, combination of anaerobic and aerobic metabolic
functions resulted in effective performance.
Chapter 5: Influence of Metabolic Shift and Multiphase Microenvironment/
Redox Conditions on the Process Performance
Chapter 5 presents experimental results related to metabolic shift and multiphase
microenvironment/redox conditions variation studies performed on biofilm configured
SBRs using all the three kinds of wastewaters. Experiments were carried out with the
combination of metabolic shifts (aerobic to anaerobic and anaerobic to aerobic) with the
function of wastewater type, OLR and HRT to assess the relative advantages of the shifts
on the process performance. The metabolic shift revealed to have significant influence on
the overall process efficiency of the periodic discontinuous process. The performance
efficiency was found to be governed by the type of wastewater being treated, placement
of the metabolic function in integration and HRT.
Anaerobic to aerobic shift showed
higher performance efficiency over the aerobic-anaerobic shift of the metabolic
functions. In case of SDW also, anaerobic to aerobic metabolic shift resulted in effective
performance. Twenty experiments varying sequence phase microenvironment in biofilm
configured aerobic systems were carried out. Experimental results with multiphase
microenvironment studies revealed the influence of redox conditions in the reaction
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phase of the sequence phase operation and has significant influence on the overall
process efficiency of periodic discontinuous operation.
Inclusion of anoxic
microenvironment in reaction phase of aerobic SBR has showed positive influence on the
process efficiency. Multiphase placement of anoxic microenvironment in reaction phase
of sequence operation has positive influence on the overall performance of the SBR.
Prolonged anoxic microenvironment provision without multiple shifts in reaction phase
of
the
cycle
operation
showed
retarded
performance
efficiency.
Anaerobic
microenvironment showed more efficiency compared to prolonged placement of anoxic
redox condition in the reaction phase in SBR operation. The extent of HRT showed to
have positive influence an overall process performance. Altering sequence phase
microenvironment with anoxic and aerobic phase (each for 2 hours) resulted in enhanced
performance compared to other combinations studied. Inclusion of anoxic phase in
sequence phase operation for extended/longer periods showed process inhibition
(substrate removal) over repeated altering of anoxic and aerobic phase for short periods.
Chapter 6:
Optimization of anaerobic process treating complex chemical
wastewater in sequencing batch biofilm reactor (AnSBBR) by Taguchi Dynamic
DOE Methodology
Chapter 6 presents results pertaining to the studies performed for the optimization of
anaerobic process (series of biological processes manifested by complex multi-species
reactions) of wastewater treatment using design of experimental methodology (DOE)
using dynamic approach. The methodology designed in this study by adopting Taguchi
DOE procedure using dynamic approach for optimization of anaerobic processes was
first time reported. The study demonstrated the applicability of robust/dynamic design
with
Taguchi
methodology was
possible
by taking
into
consideration
the
uncontrollable/noise factors for process optimization and to understand the role of factors
involved in the dynamic anaerobic processes operation for treating the complex chemical
wastewater. This approach helped to identify the influence/contribution of individual
factors, to arrive at the relationship between variables and operational conditions and
finally, to establish the performance at the optimum levels, using a few well defined
experimental sets. The Taguchi method has provided a systematic and efficient
mathematical approach to understand complex multi-species manifested in anaerobic
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process for the optimization of the near optimum design parameters, only with a few well
defined experimental sets.
Chapter 7: Bioaugmentation of anaerobic sequencing batch biofilm reactor
(AnSBBR) for the treatment of sulfate bearing chemical wastewater
This chapter presents experimental data related to the investigation carried out on the
application of bioaugmentation strategy to enhance the process efficiency of anaerobic
sequencing batch biofilm reactor (AnSBBR) treating the sulfate bearing chemical
wastewater by augmentation with enriched SRB consortia in an entrapped matrix. The
results demonstrated the successful application of bioaugmentation strategy by means of
enriched SRB consortia in an entrapped form to enhance the overall performance of the
reactor for the treatment of chemical wastewater with high sulfate content operated in
sequencing batch mode. Significant enhancement in the overall process performance of
the reactor was observed after the augmentation. COD removal efficiency was found to
increase from 35 to 70% with concomitant increase in biogas yield. Further, sulfate
reduction had increased significantly from 27% to 80%.
Chapter 8: Summary and Conclusions
This chapter summarizes the work presented in the thesis and presents the important
conclusions drawn from this study. The experimental data obtained from this
investigation demonstrated the efficiency of periodic discontinuous process over the
continuous operation in treating the complex wastewater. The maximum substrate
degradation rate was evidenced at less HRT compared to continuous systems. The SBR
systems showed to sustain their performance at higher OLRs studied. Moreover, the
ancillary unit operations such as settling, aeration chamber, etc are all integrated in the
single reactor leading to economic operation with less reactor volume.
It can be
concluded from the compilation of experimental data that the aerobic biofilm configured
system operated in periodic discontinuous process operation designed with multiphase
anoxic microenvironment rapidly altering between aerobic redox condition (by
optimizing the placements and time period of anoxic microenvironment) will yield
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effective performance with respect to substrate removal efficiency for chemical
wastewater. Optimization of HRT, anoxic phase placement and time period, OLR, etc
will result in the best performance of periodic discontinuous operation. Flexibility of
sequence phase microenvironment variation and prevailing substrate gradient during
sequence phase operation facilitated robustness to the system with respect to microflora
leading to the effective and stable process performance. Time varying individual
components of incoming wastewater places microorganism under nutritional shift
(oscillating between feast and famine conditions). This results in maintenance of wide
variety and distribution of microbial population in the reactor. Periodic operations with
altering feast and famine conditions also resulted in higher uptake of substrate with
effective settling of the biomass. Organic loading (shock loads) rates have shown
relatively less effect on the performance and at higher loads the stabilization of the
reactor is also rapid. The periodic discontinuous operation showed higher flexibility to
operate the system under varying metabolic function, reactor configuration and sequence
phase operation. Enforced short term unsteady state conditions coupled with periodic
exposure of the microorganisms to defined process conditions by controlling their
physiological state (incorporating required metabolic conditions) in SBR showed a
comparatively efficient performance over the continuous systems in treating complex
chemical wastewater.
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References
1. Venkata Mohan S, Prakasham RS, Satyavathi B, Annapurna J, Ramakrishna
SV.2001. Biotreatability studies of pharmaceutical wastewaters using an
anaerobic suspended film contact reactor. Water Sci Technol, 43(2), 271-276.
2. Venkata Mohan S, Krishna Prasad K, Prakasham RS, Sharma PN.2002.
Enzymatic
pretreatment to enhance the biodegradability of industrial
wastewaters. Chemical Weekly, 23, 163-168.
3. Venkata Mohan S, Sharma PN. 2002. Pharmaceutical wastewater and treatment
technologies. Pharma Bio World, 2(1), 93-100.
4. Wilderer PA. 1994.Sequencing Batch Biofilm Reactor technology. In
harnessing biotechnology for the 21st century, (Edt. Lodisch MR and Bose A),
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5. Chang HN, Moon RK, Park BG, Lim S, Choi DW, Lee WG, Song SL, Ahn
YH.2000. Simulation of SBR operation for simultaneous removal of nitrogen
and phosphorus. Bioproc Engn., 23, 513-521.
6. Dassanyakee CY, Irvine RL.2001. An enhanced biological phosphorus removal
(EBPR) control strategies for SBR’s. Water Sci Technol ., 43(3), 183-190.
7. Daims H, Pursehold U, Bjerrum L, Arnold E, Wilderer PA, Wagner M.2001.
Nitrification in sequencing biofilm batch reactor. Water Sci Technol., 43(3):, 918.
8. Efferel T, Wilderer PA.2001.Generation and properties of aerobic granular
sludge. Water Sci Technol., 43(3), 19-26.
9. Gieseke A, Arnz P, Amann R, Schramm A. 2002. Simultaneous P and N
removal in SBBR: insights from reactor- and microscale investigations. Water
Res., 36, 501-509.
10. Venkata Mohan S., R Sirisha, P N Sarma and S J Reddy. 2004.Degradation of
hlorpyrifos contaminated soil by bioslurry reactor operated in sequencial batch
mode: Bioprocess monitoring. J Hazardous Materials (in Press).
11. Wei-Chi Y, Bonk RR, Lloyd, V J., Sojka, S A.1986. Biological treatment of a
landfill leachates in sequencing batch reactor. Environ Prog., 5(1), 41-50.
12. Wilderer PA, Irvine RL, Goronszy MC.2001. Sequencing batch reactor
technology. Scientific and Technical Report. IWA Publishing, No 10.
13. Richard O, Mines JR, Dean Milton G.1998. Bionutrient removal with SBR.
Water Air Soil Poll., 107, 81-89.
14. Pochana, L, Kellen, J, Lant, P.1999. Model development for simultaneous
nitrification and denitrification. Wat Sci Tech.., 39(1), 235-243
15. Rajaguru P, Kalaiselvi K, Palanivel M, Subburam V.2000.Biodegradation of
azo dyes in sequencing anaerobic-aerobic systems. Appl Microbiol Biotech., 54,
268-273.
16. Buitron G, Soto G, Vite G, Morena J.2001. Strategies to enhance the
biodegradation of toxic compounds using discontinuous process. Water Sci
Technol ., 43(3), 283-290.
17. Fu L, Wen X, Lu Q, Quain Y.2001. Treatment of dyeing wastewater in two
SBR systems. Proc Biochem , 36, 1111-1118.
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18. Giraja S, Wilderer PA.2001. Characterization and treatment of the liquid
effluents from an aerobic digestion of biogenic solid waste. Water Sci Technol .,
43(3), 265-274.
19. Irvine, RL Moe, W M. 2001.Periodic biofilter operation for enhance
performance during unsteady state loading condition, Wat Sci Tech., 45 (3),
231-239.
20. Juneson C, Ward OP, Sing A.2001.Biodegradation bis(2-ehthyl hexyl) pthalate
in soil slurry-sequencing batch reactor. Proc Biochem, 37, 305-313.
21. Yalmaz G, Oztusk I.2001.Biological ammonia removal from an aerobically
pretreated leachates in sequencing batch reactors. Water Sci Technol., 43(3),
307-314.
22. Venkata Mohan S, Nancharaiah YV, Falkentoft C, Wattiau P, Wuertz S,
Wilderer PA, Hausner M.2002. Monitoring the conjugal transfer of plasmid
pWWO from Pseudomonas putida in a Sequential Batch Biofilm Reactor, Proc
VAAM Conference, Göttingen.
23. Nacharaya YV, Wattiau P, Werertz S, Bathe S, Venkata Mohan S, Wilderer
PA, Hausner M.2003. Dual labelling of Pseudomonas Putida with fluorescent
proteins for in situ monitoring of conjugal transfer of TOL plasmid. Applied
Envir. Microbiol., 69(8), 4846-4852.
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Patent and Publications of the Author
Patent from the thesis
S Venkata Mohan, PN Sarma, N Chandrasekhara Rao, K Krishna Prasad, and KV
Raghavan.(2004).Development of sequential batch reactor technology with biofilm configuration for
the treatment of complex chemical and pharmaceutical effluents. (PCT. No. WO 2004/087583 A1)
Publication from the thesis
Published
1. S Venkata Mohan, N Chandrasekhara Rao, K Krishna Prasad, P Murali Krishna, R
Sreenivasa Rao and P N Sarma. 2005. Anaerobic Treatment of Complex Chemical Wastewater
in a Sequencing Batch Biofilm Reactor: Process Optimization and Evaluation of Factor
Interactions Using the Taguchi Dynamic DOE Methodology. Biotechnology and
Bioengineering (Galley Proof)
2. S Venkata Mohan, N Chandrasekhara Rao, K Krishna Prasad and PN Sarma. (2005).
Bioaugmentation of anaerobic sequencing batch biofilm reactor (ASBBR) with immobilized
sulphate reducing bacteria (SRB) for treating sulfate bearing chemical wastewater. Process
Biochemistry. 40(8), 2849-2857.
3. S Venkata Mohan, N Chandrasekhara Rao, K Krishna Prasad, BTV Madhavi and PN Sarma.
(2005). Treatment of complex chemical effluents by sequencing batch reactor (SBR) with
aerobic suspended growth configuration. Process Biochemistry, 40(5), 1501-1508.
4. N Chandrasekhara Rao, S Venkata Mohan and PN Sarma. (2005). Treatment of composite
chemical wastewater by GAC-Biofilm configured sequencing batch reactor (SBGR) operated in
aerobic environment. J Hazardous Materials (Accepted and in press).
5. S Venkata Mohan, N Chandrasekhara Rao and PN Sarma. (2005). Influence of sequencing
phase microenvironment on periodic discontinuous process treating complex chemical
wastewater, Water Intelligent Online (accepted).
6. S Venkata Mohan, N Chandrasekhara Rao and PN Sarma. (2005). Simulated acid azo dye
wastewater treatment in aerobic suspended growth configured sequencing batch reactor (SBR).
Indian Journal of Biotechnology (accepted).
Communicated
7. S Venkata Mohan, N Chandrasekhara Rao, K Laxma Reddy and PN Sarma. (2005).
Influence of self immobilized GAC configuration in the treatment of complex chemical
wastewater in periodic discontinuous operation. Chemosphere (communicated).
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Other Publications
1. S Venkata Mohan, K Krishna Prasad, N Chandrasekhara Rao, and PN Sarma. (2005).
Enzyme mediated degradation of acid azo dye in aqueous phase. Chemosphere, 58, 10971105.
2. S Venkata Mohan, R Sirisha, N Chandrasekhara Rao, PN Sarma and SJ Reddy. (2004).
Degradation of chlorpyrifos contaminated soil by bioslurry reactor operated in sequencing
batch mode: Bioprocess monitoring. J Hazardous Materials, B116, 39-48.
3. AG Rao, N Chandrasekhara Rao, KK Prasad. GV Naidu, S. Venkata Mohan, Annapoorna
Jetty and PN Sarma. (2004). Anaerobic treatment of pharamaceutical wastewater in fixed film
reactor. Bioresource Technology, 93, 241-247.
4. AG Rao, KK Prasad. GV Naidu, N Chandrasekhara Rao and PN Sarma. (2004). Removal of
sulfide in integrated anaerobic-aerobic wastewater tratment system. Clean Tech Environ
Policy, 6, 66- 71.
5. MP Reddy, N Chandrasekhara Rao, K Krishna Prasad, S. Venkata Mohan, PN Sarma, VD
Kumari and M Subrahmanyam. (2002). Photocatalytic treatment of common industrial
wastewater. Indian J Environ Proct., 22, 1253-1256.
6. S Venkata Mohan, N Chandrasekhara Rao and K Krishna Prasad. (2002). Treatment of
simulated Reactive Yellow 22 (azo) dye effluents using Spirogyra Sp. Waste Management, 22,
575-582.
7. S Venkata Mohan, N Chandrasekhara Rao and K Krishna Prasad. (2002). Biological
decolorization of simulated basic dye effluents by algal spirogyra species. Asian J Microbiol
Biotech Environ Sci., 4(1), 107-111.
8. S Venkata Mohan, N Chandrasekhar Rao and J Karthikeyan (2002).Adsorption removal of
direct azo dye from aqueous phase onto coal based sorbents: kinetic and mechanistic study. J
Hazardous Materials, 90(2), 189-204.
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