Sludge Sequencing Batch Reactor Research Articles

Rapid start-up of partial nitritation in aerobic granular sludge bioreactor and the analysis of bacterial community dynamics.

The rapid start-up of the partial nitritation process in a laboratory-scale aerobic granular sludge-sequencing batch reactor was successful by controlling low dissolved oxygen and gradually increasing the influent ammonia levels. The microbial community dynamics were analyzed by high-throughput sequencing and quantitative polymerase chain reaction. The microbial communities were significantlyaffected by the different influent NH4+-N concentrations (77.84, 119.42, 170.31, and 252.21mg/L) in Phases I, II, III, and IV. The sludge Shannon index in Phases I, II, III, and IV was 3.9, 4.39, 3.47, and 2.13, respectively, which was higher than that of the inoculated sludge (1.62). The dominant class transformed from Alphaproteobacteria and Gammaproteobacteria in Phase I to Betaproteobacteria in Phase IV. Furthermore, Sphingobacteria and Clostridia were the dominant bacteria in Phases III and IV. The quantitative polymerase chain reaction (qPCR) results suggested that Nitrosomonadaceae_uncultured belonging to ammonia-oxidizing bacterium was the dominant species, but the relative abundance of nitrite-oxidizing bacteria (mainly Nitrospira and Nitrobacter) was extremely rare in Phase IV. Furthermore, Thauera, Denitratisoma, and Planctomycetacia were the dominant functional nitrogen removal microbes in Phases III and IV. Some nitrogen removal pathways such as partial nitritation, denitrification, and anaerobic ammonium oxidation co-existed in the partial nitritation process.

Parametric optimization of domestic wastewater treatment in an activated sludge sequencing batch reactor using response surface methodology

In this work, the parametric optimization of real domestic wastewater treated in an activated sludge sequencing batch reactor (SBR) was performed by means of the response surface methodology (RSM). The influences of influent organic matter concentration as chemical oxygen demand (CODinf), biomass concentration (Xs) and aeration time (t) on the COD, organic matter removal efficiency as COD (η) and sludge volume index (SVI) were determined to evaluate the performance of activated sludge SBR. The results showed that organic matter efficiency and maximum SVI were obtained at a t of 12 h, 300 mg L−1 of CODinf and 2000 mg L−1 of Xs. The SBR-activated sludge exhibited a η of 73% and an SVI of 119 mL g−1. Both values indicated a very good performance. Furthermore, the COD of the effluent under these conditions complied with Mexican regulations for wastewater discharged into water bodies.

Diversity evolution of functional bacteria and resistance genes (CzcA) in aerobic activated sludge under Cd(II) stress

An activated sludge sequencing batch reactor (SBR) was used to treat divalent cadmium (Cd(II)) wastewater for 60 d to investigate the overall treatment performance, evolution of the bacterial community, and abundance of the Cd(II) resistance gene CzcA and shifts in its potential host bacteria. During stable operation with a Cd(II) concentration of 20 mg/L, the average removal efficiencies of Cd(II) and chemical oxygen demand (COD) were more than 85% and that of total phosphorus was greater than 70%, while the total nitrogen (TN) was only about 45%. The protein (PN) content in the extracellular polymeric substances (EPS) increased significantly after Cd(II) addition, while polysaccharides displayed a decreasing trend (p < 0.05), indicating that EPS prefer to release PN to adsorb Cd(II) and protect bacteria from damage. Three-dimensional fluorescence spectral analysis showed that fulvic acid-like substances were the most abundant chemical components of EPS. The addition of Cd(II) adversely affected most denitrifying bacteria (p < 0.05), which is consistent with the low TN removal. In addition, quantitative polymerase chain reaction analysis revealed that CzcA gene abundance decreased as the Cd(II) concentration increased, possibly because expression of the CzcA gene was inhibited by Cd(II) stress. The majority of CzcA gene sequences were carried by Pseudomonas, making it the dominant genus among Cd(II)-resistant bacteria.

Chemical composition of extracellular polymeric substances and evolution of microbial community in activated sludge exposed to ibuprofen

Ibuprofen (IBU) containing wastewater with a concentration of 1-5 mg/L was treated in an activated sludge sequencing batch reactor (SBR), for 60 days, in order to investigate the overall performance of the SBR, the parameter variations during a typical cycle, the chemical composition and content of extracellular polymeric substances (EPS) and the evolution of microbial community. The average removal efficiencies of COD, NH4+-N and TN were >85%, while >40% of the IBU was removed and the removal efficiencies of TP fluctuated around ~ 75%. The EPS content increased significantly with IBU addition (p < 0.01). Fulvic acid-like substances in the chemical composition of EPS increased during the stable operation phase. Proteobacteria associated with nitrogen removal was the dominant phylum, which can also resist IBU stress. For the denitrifying bacteria, the OTUs of both Rhodobacter and Pseudomonas increased from day 1-30 and reduced on day 60 (p < 0.01), which was opposite to the results observed for Rhodocyclaceae (phosphorus-accumulating bacteria). The OTUs of Acidovorax showed an increasing trend (p < 0.01), whereas the OTUs for Nitrospira (nitrite oxidizers) and Nitrosomonas (ammonia oxidizers) decreased significantly (p < 0.05).

Importance of controlling phosphate concentration in nitritation–anammox reactor operation

The effect of phosphate on anaerobic ammonium oxidation (anammox) was investigated in an integrated fixed film activated sludge-sequencing batch reactor (IFAS-SBR) treating raw digester sludge thickening lagoon supernatants before and after Ostara® treatment (for phosphorus recovery).

Elucidating performance failures in use of granular sludge for nutrient removal from domestic wastewater in a warm coastal climate region

ABSTRACTThe effects of domestic wastewater and a coastal warm climate on granular sludge and biological nutrient removal were evaluated using a pilot-scale sequencing batch reactor (SBR). The reactor operation employed two different operational strategies (OS) based on up-flow feeding regimes, defined as fast (OS1, flow rate = 18.0 L min−1 and flow velocity = 22.0 m h−1) and slow (OS2, flow rate = 3.5 L min−1 and flow velocity = 4.3 m h−1). Under slow feeding, larger (OS1: 290 µm; OS2: 450 µm) and faster settling granules were obtained (OS1: 109; OS2: 74 mL g−1 TSS). The slow feeding regime was also advantageous for the hydrolysis of particulate organic matter (OS1: 1.3; OS2: 3.1 g CODtot g−1 VSS d−1) and for phosphorus removal (OS1: <33%; OS2: >97.5%). Neither strategy resulted in substantial biomass accumulation in the reactor (OS1: 0.7; OS2: 1.5 g VSS L−1), and high concentrations of nitrite were observed in the effluent (9–27 mg L−1). Ordinary heterotrophic organisms dominated the granular sludge developed under both feeding regimes (OS1: 30% of Thauera; OS2: 56% of Comamonas), while polyphosphate-accumulating organisms (PAOs) were only detected during OS2 (2.3–3.4% of total bacteria). A successful granular sludge process should be able to cope with high fluctuations in wastewater loads caused by rain events (82–182 mm month−1 in Florianopolis, Brazil). In order to achieve higher water quality, strategies identified for an efficient granular sludge SBR operation included (i) management of an anaerobic phase for PAO selection, and (ii) aeration control for successful nitrification/denitrification.

Role of adding dried sludge micropowder in aerobic granular sludge reactor with extended filamentous bacteria

This work investigated the extended filamentous bacteria and role of sludge micropowder (prepared from dried municipal wastewater sludge) addition in an aerobic granular sludge-sequencing batch reactor (AGS-SBR). Type 021N strain is one of the dominant extended filaments and remarkably diminished after micropowder addition. Then, sludge volume index (SVI5) value decreased from 172 to 44 mL/g. Micropowder supplemented in the SBR created physical collisions with granules containing extended filaments, improved sludge settleability, and induced microorganisms to secrete more extracellular polymeric substances (EPS), which favored the internal growth of extended filaments and enhanced sludge granulation. Furthermore, pollution removal efficiencies increased and maintained at about 85%. The dosage of sludge micropowder had a positive impact on granulation and reactor operation even at the short-term adding stage.

Pengaruh Laju Pembebanan Organik terhadap Reduksi Padatan pada Proses Anaerobic Co-Digestion Sampah Sayuran dengan Lumpur SBR

Anaerobic digestion is to treat organic waste such as vegetable solid waste (VSW). Anaerobic co-digestion is the mixture of two or more different waste types with the aim to enhance the efficiency of the anaerobic digestion process. In this study, anaerobic digestion of vegetable solid waste (VSW) is compared to the anaerobic co-digestion of VSW and sequencing batch reactor (SBR) sludge. This investigation is focussed on the varying the organic loading rate (OLR) which is the mixing ratio of VSW to SBR sludge; and pH (6, 7 and 8) of the mixture. The mixtures were kept in serum bottles and placed in a shaker for 7 days at 150 rpm. Experiments with OLR 2:1, VSW composition of 1:2:1:1 and pH 6 produced the highest total biogas in anaerobic co-digestion. Thus, for anaerobic co-digestion, the optimum composition of VSW, OLR and pH are 1:2:1:1, 2:1 and 6 respectively. The range of % reduction in total solids (TS), total suspended solids (TSS) and total dissolve solids (TDS) in anaerobic co-digestion is 4-46, 0-43 and 0-64 respectively. In a comparison with single digestion, only 1 in 5 samples of co-digestion exceed that amount of biogas produced by single digestion and this shows that single anaerobic digestion resulted in higher biogas yield. The range of % reduction in TS, TSS and TDS in anaerobic digestion is 13-54, 15-66 and 9-58 respectively. Comparatively, single digestion performs better in solids removal than anaerobic co-digestion and thus, co-digestion method may not be suitable for all types of organic waste.

Influence of pH on short-cut denitrifying phosphorus removal

Through a series of experiments using denitrifying phosphorus-accumulating sludge in sequencing batch reactors (SBRs), the variations of the intracellular polymers during the anaerobic phosphorus release process at different pH values were compared, the probable reasons for different performances of phosphorus removal were examined, and system operations in a typical cycle were investigated. The results show that the phosphorus removal rate was positively correlated with pH values in a range of 6.5–8.5. When the pH value was 8.0, the anaerobic phosphorus release rate and anoxic phosphorus uptake rate of the activated sludge were 20.95 mg/(g∙h) and 23.29 mg/(g∙h), respectively; the mass fraction of poly-β-hydroxybutyrate (PHB) increased to 62.87 mg/g under anaerobic conditions; the mass fraction of polyphosphate was 92.67 mg/g under anoxic conditions; and the effluent concentration of total phosphorus (TP) was 1.47 mg/L. With the increase of pH, the mass fraction of acetic acid and PHB also increased, and the absorption rate of acetic acid was equal to the disintegration rate of polyphosphate. When the pH value was above 8.0, biological phosphorus removal was achieved by chemical phosphorus precipitation, and the phosphorus removal rate decreased.

How biomass growth mode affects ammonium oxidation start-up and NOB inhibition in the partial nitritation of cold and diluted reject water

ABSTRACTThe inhibition of undesirable nitrite oxidizing bacteria (NOB) and desirable ammonium oxidizing bacteria (AOB) by free ammonia (FA) and free nitrous acid (FNA) in partial nitritation (PN) is crucially affected by the biomass growth mode (suspended sludge, biofilm, encapsulation). But, the limitations of these modes towards less concentrated reject waters (≤600 mg-N L−1) are unclear. Therefore, this work compares the start-up and stability of three PN sequencing batch reactors (SBRs) with biomass grown in one of the three modes: suspended sludge, biofilm and biomass encapsulated in polyvinyl alcohol (PVA) pellets. The SBRs were operated at 15°C with influent total ammonium nitrogen (TAN) concentrations of 75–600 mg-TAN L−1. PN start-up was twice as fast in the biofilm and encapsulated biomass SBRs than in the suspended sludge SBR. After start-up, PN in the biofilm and suspended sludge SBRs was stable at 150–600 mg-TAN L−1. But, at 75 mg-TAN L−1, full nitrification gradually developed. In the encapsulated biomass SBR, full nitrification occurred even at 600 mg-TAN L−1, showing that NOB in this set-up can adapt even to 4.3 mg-FA L−1 and 0.27 mg-FNA L−1. Thus, PN in the biofilm was best for the treatment of an influent containing 150–600 mg-TAN L−1.

Treatment of old landfill leachate with high ammonium content using aerobic granular sludge

BackgroundAerobic granular sludge has become an attractive alternative to the conventional activated sludge due to its high settling velocity, compact structure, and higher tolerance to toxic substances and adverse conditions. Aerobic granular sludge process has been studied intensively in the treatment of municipal and industrial wastewater. However, information on leachate treatment using aerobic granular sludge is very limited.MethodsThis study investigated the treatment performance of old landfill leachate with different levels of ammonium using two aerobic sequencing batch reactors (SBR): an activated sludge SBR (ASBR) and a granular sludge SBR (GSBR). Aerobic granules were successfully developed using old leachate with low ammonium concentration (136 mg L−1 NH4+-N).ResultsThe GSBR obtained a stable chemical oxygen demand (COD) removal of 70% after 15 days of operation; while the ASBR required a start-up of at least 30 days and obtained unstable COD removal varying from 38 to 70%. Ammonium concentration was gradually increased in both reactors. Increasing influent ammonium concentration to 225 mg L−1 N, the GSBR removed 73 ± 8% of COD; while COD removal of the ASBR was 59 ± 9%. The GSBR was also more efficient than the ASBR for nitrogen removal. The granular sludge could adapt to the increasing concentrations of ammonium, achieving 95 ± 7% removal efficiency at a maximum influent concentration of 465 mg L−1 N. Ammonium removal of 96 ± 5% was obtained by the ASBR when it was fed with a maximum of 217 mg L−1 NH4+-N. However, the ASBR was partially inhibited by free-ammonia and nitrite accumulation rate increased up to 85%. Free-nitrous acid and the low biodegradability of organic carbon were likely the main factors affecting phosphorus removal.ConclusionThe results from this research suggested that aerobic granular sludge have advantage over activated sludge in leachate treatment.

Effect of Two-Stage Aeration on Nitrogen Removal Performance of Aerobic Granular Sludge

Four mini experiments were conducted at different conditions. The heterotrophic microorganisms on the aerobic granular sludge surface consumed organic compounds at the initial stage of aeration. The denitrification rate and the efficiency of NO2--N and NO3--N removal were relatively low. Therefore, under the normal temperature conditions (20-23℃), aerobic granular sludge sequencing batch reactor (SBR) was operated in the two-stage aeration mode(first in low aeration then in high aeration mode). The low aeration time were carried out at 1, 2 and 3 hours stages respectively, and the characteristics of the granular sludge and its effects on microorganisms were analyzed by scanning electron microscopy (SEM) and fluorescence in situ hybridization (FISH) technique. The results show that the increase in the aerobic granular sludge (AGS) particle size improved the denitrification capacity; the denitrification rate of NO2--N was the highest at low aeration mode with 2 h and reached 9.66 mg·(g·h)-1. The accumulation rate of nitrite increased to 77.84% and the total nitrogen removal rate to 70%. The bacterial count inside the granular sludge increased and they were mainly cocci, bacillus, and ellipsoidal bacteria. Moreover, the proportion of ammonia-oxidizing bacteria in total bacterial count increased from 13.70% to 15.40%. Therefore, the two-stage aeration process achieved shortened simultaneous nitrification and denitrification processes and showed a good denitrification performance.

SBR treatment of tank truck cleaning wastewater: sludge characteristics, chemical and ecotoxicological effluent quality

ABSTRACTA lab-scale activated sludge sequencing batch reactor (SBR) was used to treat tank truck cleaning (TTC) wastewater with different operational strategies (identified as different stages). The first stage was an adaptation period for the seed sludge that originated from a continuous fed industrial plant treating TTC wastewater. The first stage was followed by a dynamic reactor operation based on the oxygen uptake rate (OUR). Thirdly, dynamic SBR control based on OUR treated a daily changing influent. Lastly, the reactor was operated with a gradually shortened fixed cycle. During operation, sludge settling evolved from nearly no settling to good settling sludge in 16 days. The sludge volume index improved from 200 to 70 mL gMLSS−1 in 16 days and remained stable during the whole reactor operation. The average soluble chemical oxygen demand (sCOD) removal varied from 87.0% to 91.3% in the different stages while significant differences in the food to mass ratio were observed, varying from 0.11 (stage I) to 0.37 kgCOD.(kgMLVSS day)−1 (stage III). Effluent toxicity measurements were performed with Aliivibrio fischeri, Daphnia magna and Pseudokirchneriella subcapitata. Low sensitivity of Aliivibrio was observed. A few samples were acutely toxic for Daphnia; 50% of the tested effluent samples showed an inhibition of 100% for Pseudokirchneriella.

Short-term Influence of Two Types of Drilling Fluids on Wastewater Treatment Rate and Eukaryotic Organisms of Activated Sludge in Sequencing Batch Reactors.

This work presents the results of studies on the impact of spent drilling fluids cotreated with municipal wastewater on the rate of the wastewater treatment process and the structure of the community of eukaryotic organisms inhabiting an activated sludge. The studies were conducted under laboratory conditions in sequencing batch reactors. The effect of added polymer-potassium drilling fluid (DF1) and polymer drilling fluid (DF2) at dosages of 1 and 3% of wastewater volume on the rate of removal of total suspended solids, turbidity, chemical oxygen demand, and the content of total and ammonium nitrogen were analyzed, taking into account the values of these parameters measured at the end of each operating cycle. In addition to the impacts on the aforementioned physicochemical indices, the influence of drilling fluid on the biomass of various groups of eukaryotes in activated sludge was analyzed. The impact of the drilling fluid was highly dependent on its type and dosage. A noticeable slowdown in the rate of the wastewater treatment process and a negative effect on the organisms were observed after the addition of DF2. This effect intensified after an increase in fluid dose. However, no statistically significant negative changes were observed after the introduction of DF1. Conversely, the removal rate of some of the analyzed pollutant increased.

Pollutant removal and microorganism evolution of activated sludge under ofloxacin selection pressure

An activated sludge sequencing batch reactor (SBR) was fed with synthetic wastewater containing ofloxacin (OFL) for 52days to study the overall performance of the SBR, the characteristics of extracellular polymeric substances (EPS) and the bacterial community shift. Removal efficiencies of chemical oxygen demand, ammonia nitrogen, phosphorus and OFL were maintained at 90%, 96%, 80% and 65%, respectively. The EPS contents increased with increasing OFL concentration because more EPS was secreted to protect cells from OFL damage. Moreover, the EPS compositions shifted. For denitrifying bacteria, the read number of Pseudomonas and Bacillus sharply decreased initially (p<0.05) and increased from Day 25 to Day 50, which agreed with the tendency of Nitrosomonadaceae (ammonia oxidizer), while Paracoccus significantly decreased (p<0.05). The read number of Rhodocyclaceae, a phosphorus-accumulating bacterium, increased. Other functional microbes such as Nitrospirales (nitrite oxidizer) and Planctomyces (anammox) sharply decreased under OFL pressure (p<0.05).

Production of poly-β-hydroxybutyrate by activated sludge in sequencing batch reactor under aerobic conditions

In order to improve poly-β-hydroxybutyrate (PHB) production in activated sludge, the anaerobic/aerobic alternative operating sequencing batch reactor (SBR) process was applied in this paper to accumulate PHB. Effects of nutritional conditions and carbon concentration on PHB accumulation were studied. Results indicated that PHB accumulation reached the highest level and accounted for 11.2 % under anaerobic condition for phosphate limitation and 20.84 % under aerobic condition for nitrogen and phosphate limitation of mixed liquor suspended solid (MLSS), respectively. In addition, 4 g/L was proved to be the optimum carbon concentration in both anaerobic and aerobic experiments, and the PHB accumulation reached 17.1 % (anaerobic, phosphorus limitation) and 60.4 % (aerobic, nitrogen and phosphorus limitation) of MLSS, respectively. PHB could be successfully extracted with sodium hypochlorite and chloroform method from the activated sludge. In addition, the infrared spectrum showed that the PHB sample extracted was of high purity.

Dynamic Modelling of Aerobic Granular Sludge Artificial Neural Networks

Aerobic Granular Sludge (AGS) technology is a promising development in the field of aerobic wastewater treatment system. Aerobic granulation usually happened in sequencing batch reactors (SBRs) system. Most available models for the system are structurally complex with the nonlinearity and uncertainty of the system makes it hard to predict. A reliable model of AGS is essential in order to provide a tool for predicting its performance. This paper proposes a dynamic neural network approach to predict the dynamic behavior of aerobic granular sludge SBRs. The developed model will be applied to predict the performance of AGS in terms of the removal of Chemical Oxygen Demand (COD). The simulation uses the experimental data obtained from the sequencing batch reactor under three different conditions of temperature (30˚C, 40˚C and 50˚C). The overall results indicated that the dynamic of aerobic granular sludge SBR can be successfully estimated using dynamic neural network model, particularly at high temperature.

Microbial Population Dynamics and Ecosystem Functions of Anoxic/Aerobic Granular Sludge in Sequencing Batch Reactors Operated at Different Organic Loading Rates.

The granular sludge process is an effective, low-footprint alternative to conventional activated sludge wastewater treatment. The architecture of the microbial granules allows the co-existence of different functional groups, e.g., nitrifying and denitrifying communities, which permits compact reactor design. However, little is known about the factors influencing community assembly in granular sludge, such as the effects of reactor operation strategies and influent wastewater composition. Here, we analyze the development of the microbiomes in parallel laboratory-scale anoxic/aerobic granular sludge reactors operated at low (0.9 kg m-3d-1), moderate (1.9 kg m-3d-1) and high (3.7 kg m-3d-1) organic loading rates (OLRs) and the same ammonium loading rate (0.2 kg NH4-N m-3d-1) for 84 days. Complete removal of organic carbon and ammonium was achieved in all three reactors after start-up, while the nitrogen removal (denitrification) efficiency increased with the OLR: 0% at low, 38% at moderate, and 66% at high loading rate. The bacterial communities at different loading rates diverged rapidly after start-up and showed less than 50% similarity after 6 days, and below 40% similarity after 84 days. The three reactor microbiomes were dominated by different genera (mainly Meganema, Thauera, Paracoccus, and Zoogloea), but these genera have similar ecosystem functions of EPS production, denitrification and polyhydroxyalkanoate (PHA) storage. Many less abundant but persistent taxa were also detected within these functional groups. The bacterial communities were functionally redundant irrespective of the loading rate applied. At steady-state reactor operation, the identity of the core community members was rather stable, but their relative abundances changed considerably over time. Furthermore, nitrifying bacteria were low in relative abundance and diversity in all reactors, despite their large contribution to nitrogen turnover. The results suggest that the OLR has considerable impact on the composition of the granular sludge communities, but also that the granule communities can be dynamic even at steady-state reactor operation due to high functional redundancy of several key guilds. Knowledge about microbial diversity with specific functional guilds under different operating conditions can be important for engineers to predict the stability of reactor functions during the start-up and continued reactor operation.

Short-term Influence of Drilling Fluid on Ciliates from Activated Sludge in Sequencing Batch Reactors.

Spent drilling muds are the liquid residues of rock drilling operations. Due to a high concentration of suspended solids and potentially detrimental chemical properties, they can negatively affect microorganisms participating in wastewater treatment processes. We evaluated the addition of a potassium-polymer drilling fluid (DF) to activated sludge in laboratory sequencing batch reactors (SBRs) for municipal wastewater treatment. Ciliate assemblage, the most dynamic component of eukaryotes in activated sludge, and which is highly sensitive to changes in the system, was evaluated. The average ciliate abundance dropped by about 51% (SBR 2; 1% DF added) and 33% (SBR 3; 3% DF added) in comparison to the control (SBR 1; wastewater only). A decrease in the total number of ciliate species during the experiment was observed, from 25 to 24 in SBR 2 and from 17 to 13 in SBR 3. Moreover, a drop in the number of dominant (>100 individuals mL) ciliate species was observed during the experiment-from eight in the control to five in SBR 2 and four in SBR 3-signaling noticeable changes in the quantitative structure of ciliate species. The species analyzed showed different responses to DF addition. The most sensitive was , which is bacteriovorus. In contrast, two predators, and , showed no reaction to DF addition. Our results indicate that addition of potassium-polymer DF, in doses of 1 to 3% of the treated wastewater volume, had no toxic effects on ciliates, but qualitative and quantitative changes in their community were observed.

Carbon Footprint Analyses of Wastewater Treatment Systems in Puducherry

Carbon footprint analysis is a method to quantify the life cycle Greenhouse Gases (GHGs) emissions and identify the measure to reduce climate change impacts. The Intergovernmental Panel on Climate Change (IPCC) has identified that the global warming and climate change which is one of the most important issues in the domain of environment are caused by the excessive emission of Greenhouse Gases (GHG) mainly constituting Carbon dioxide (CO2), Methane (CH4) and Nitrous oxide (N2O). The municipal wastewater treatment plant receives wastewater for treatment and finally discharges the treated effluent. The emissions of GHG during the treatment of wastewater as well as during the treatment process of sludge and also for energy generation are known to be on-site GHG emissions. Off-site GHG emissions are generated due to transportation and disposal of sludge, off-site energy and chemical production. In Puducherry, the municipal wastewater is being treated using oxidation ponds, Upflow Anaerobic Sludge Blanket (UASB) and Sequencing Batch Reactor (SBR). Wastewater treatment using Sequencing Batch Reactor (SBR) technology is one of the state-of-the art wastewater management systems. In this technology equalization, biological treatment and secondary clarification are performed in a single reactor in a time control sequence. The emissions of GHG from the Oxidation ponds of 12.5 MLD, UASB reactor of 2.5 MLD and SBR of 17 MLD were assessed based on the IPCC guidelines and the total emissions of GHG in terms of equivalent of CO2 were compared. The performance of the SBR is more efficient and the emissions of GHG are less than the emissions in the UASB as well as in oxidation ponds. The emission of GHG in SBR is about 60% of the existing treatment systems of oxidation ponds and UASB thus a reduction of 40% GHG emission could be achieved.