International Research Journal of Environment Sciences__________________________________ ISSN 2319–1414Vol. 4(12), 8-16, December (2015) Int. Res. J. Environment Sci. International Science Congress Association 8 Tracing Carbon Footprint in the Wastewater Treatment Plant Hasan M. Hamouda Department of Civil Engineering, Faculty of Applied Engineering and Urban Planning, University of Palestine, 1075, PALESTINE Available online at: www.isca.in, www.isca.me Received 25th May 2015, revised 4th November 2015, accepted 13th December 2015 AbstractThe greenhouse gases, carbon dioxide (CO), methane (CH) and nitrous oxide (NO) can all be produced in wastewater treatment operations. Major progress has been encountered for estimating (NO) and (CH) emissions from wastewater treatment plants, yet, limited number of studies considered CO. One problem with the mass balance technique in the Activated Sludge lies in satisfactorily measuring waste activated sludge volumes and in obtaining representative samples for analysis. A traditional mass balance approach for analyzing the performance of the activated sludge secondary clarifier does not account for variations in sludge depth and suspended solids concentrations within different layers. In turn, a gap in knowledge is present in closing the Carbon mass balance within the Activated Sludge system. In this essence, the main focus of this research is to quantify the carbon dioxide emissions from the Aeration Tank in the biological treatment. This will be achieved by generating a full-scale of accurate measures to precisely simulate the SC behavior aiming at determining the fate of the CO through the Activated Sludge system. Results from this research attained a reasonable carbon balance closure of 95%. Keywords: Activated sludge, carbon dioxide, mass balance, wastewater treatment plant. Introduction Global warming, caused by the atmospheric build-up of Green House Gas (GHG) emissions, influences many aspects of daily life including human health, agriculture, water resources and energy use. Alongside construction, transportation and power generation, Wastewater Treatment Plants (WWTP) plays a significant role in GHG production; including CO, NO and CH. With diverse challenges facing the surrounding environment, air pollution management is a matter of grave concern. Therefore, the generation of GHGs emissions from wastewater treatment plants must be estimated before any mitigation and reduction strategy can be implemented. A typical Wastewater Treatment Plant (WWTP) consists of a set of unit processes including primary, secondary and territory treatment. Although, a significant portion of these emissions come from electricity consumption, Carbon Dioxide (CO) emissions are also associated with the Aerobic Digestion in the biological treatment. However, this amount of CO is always neglected from the WWTP’s GHG account. Activated Sludge (AS) is the most popular biological systems used in wastewater treatment plants.Conducting mass balances across the interconnected components of such system allow tracking key operating parameters from one unit of operation to a downstream one ensuring overall stability. Despite this fact, the absence of accurate measurements makes it difficult to achieve a complete mass balance closure across the system. A review of literature made in this area indicates that mass balance showed reasonable closure for most of the elements such as N and P, but not for the Carbon Dioxide (CO). Thus, previous studies were developed under the assumption of Secondary Clarifier (SC) operating at steady state; neglecting for the variation in sludge depth and suspended solids within different layers. In practice, the determination of sludge depth is not accurate as it is predicted based on the visible depth measurements rather than exact sludge depth measurements. To that end, the main aim of this study is related to a more reliable predication of the carbon fate in Wastewater treatment plant; to accurately formulate carbon mass balance and to better understand the real contribution of CO2 to GHG emissions. In this essence, this research allows in-depth studyof the activated sludge treatment process through the development of a Bench scale plant. In which, the process will be adjusted continuously in order to establish sound measures under broad scale of conditions and settings. Particular attention will be given to both, the fate of carbon in the activated sludge process as well as the performance of the secondary clarifier under dynamic conditions; a full scale dynamic data including the exact sludge depth and concentration measurements within different layers in the SC. Literature Review: Recently, global warming and climate change have become looming issues due to their effects on the environment. During wastewater treatment, the greenhouse gases; carbon dioxide (CO), methane (CH) and nitrous oxide (NO), can be transmitted to the atmosphere. The aim of wastewater treatment is to enable effluents to be safely disposed of without causing danger to human health and the surrounding International Research Journal of Environment Sciences Vol. 4(12), 8-16, December (2015) International Science Congress Association environment. Treatment of wastewater involves a sequence of physical, chemical and biological processes performance of the wastewater treatment plant can be controlled based on the characteristics of the sewage and the degree of treatment provided in each operation. ass balance is widely used approach for detecting the performance of wastewater treatment plant3,4 . Conducting solids mass balances across the interconnected components of the wastewater treatment plant allow tracking key operating parameters from one unit of operation to a downstream one ensuring overall stability. Despite this fact, the reliable measurements makes it difficult to achieve a perfect mass balance closure across the system. In particular, Secondary treatment biological treatment process releases carbon dioxide (CO ), which has always been neglected in the mass bala Reviewing literature showed a reasonable mass balance closure for most of the elements in the wastewater treatment plant; as N and P, but not for the Carbon Dioxide ( side, the SC was assumed to be operated under steady state condition ignoring the hydrodynamic state, i.e. the exact sludge level was not encountered in the mass balance, and hence the sludge accumulation term was omitted. From the other side, the Aeration Tank contribution of carbon was not considered when Environment Sciences __________________________________ ___________ Association Treatment of wastewater involves a sequence of physical, chemical and biological processes . In which, the performance of the wastewater treatment plant can be controlled based on the characteristics of the sewage and the degree of ass balance is widely used approach for detecting the . Conducting solids mass balances across the interconnected components of the wastewater treatment plant allow tracking key operating parameters from one unit of operation to a downstream one ensuring overall stability. Despite this fact, the absence of reliable measurements makes it difficult to achieve a perfect mass balance closure across the system. In particular, Secondary treatment biological treatment process releases carbon dioxide ), which has always been neglected in the mass bala nce. Reviewing literature showed a reasonable mass balance closure in the wastewater treatment plant; such as N and P, but not for the Carbon Dioxide ( CO5,6. From one side, the SC was assumed to be operated under steady state condition ignoring the hydrodynamic state, i.e. the exact sludge level was not encountered in the mass balance, and hence the From the other side, the Aeration Tank contribution of carbon was not considered when perfo rming carbon mass balance closure. Therefore, quantifying the accumulation is a necessity to close the carbon balance across the AS system and thus determining the exact amount of produced CO Methodology To accurately estimate the Carbon balance in th Treatment Plant, a bench scale unit was set up to simulate a number of conditions of the biological treatment Process. The methodology of the study in hand was broken down into the following sequential steps as shown in Bench Plant Design: The utilized bench model of the activated sludge process; as shown in figure Such model had the advantage of developing, at less costly, data on day-to-day- base of the wastewater characteristics as well as the overall eff iciency of the system, thereby providing a full representation of a full- scale plant. It mainly consisted of: i. a bioreactor, in which the microorganisms are kept in suspension; ii. a secondary settling tank and iii. a sludge recycling system for returnin g activated sludge back to the Bioreactor. The bench- scale system was designed for a flow range of 75 l/d. Figure-1 Methodology Framework Data Analysis (Sampling) Microorganism Stationary Phase Microorganism Adoptation Phase Microorganism added to the system Synthetic Perparation Set-Up Test(Test with water) Bench Assembly Units Fabrication ___________ ISSN 2319–1414 Int. Res. J. Environment Sci. 9 rming carbon mass balance closure. Therefore, quantifying the accumulation is a necessity to close the carbon balance across the AS system and thus determining To accurately estimate the Carbon balance in th e Wastewater Treatment Plant, a bench scale unit was set up to simulate a number of conditions of the biological treatment Process. The methodology of the study in hand was broken down into the following sequential steps as shown in figure-1. The utilized bench -scale plant is a small model of the activated sludge process; as shown in figure -2. Such model had the advantage of developing, at less costly, data base of the wastewater characteristics as well as iciency of the system, thereby providing a full scale plant. It mainly consisted of: i. a bioreactor, in which the microorganisms are kept in suspension; ii. a secondary settling tank and iii. a sludge recycling system g activated sludge back to the Bioreactor. The scale system was designed for a flow range of 75 l/d. International Research Journal of Environment Sciences ______________________________________________ISSN 2319–1414Vol. 4(12), 8-16, December (2015) Int. Res. J. Environment Sci. International Science Congress Association 10 Figure-2 Bench-Scale StructureComposition of the Synthetic Wastewater: Synthetic wastewater has been prepared in the laboratory as feed, keeping the chemical parameters within range of values presented in table-1. The use of synthetic waste in the study was mainly to apply better control on feed chemical concentrations of N, P. Meanwhile, a mixture of various carbon drinks will be used as a main source of required carbon. Table-1 Composition of the Synthetic WastewaterNutrient Molecular Formula Concentration (mg/l) Urea CO(NH 277 Magnesium Sulfate MgSO 7HO 100 Calcium Chloride CaCl 7.5 Potassium Dehydrogenate Phosphate KHPO 53 Di-Potassium Dehydrogenate Phosphate HPO 107 This Bioreactor was fed by a synthetic sewage stored in a feeding tank for no longer than a week time. Then, it has been aerated by a disc diffuser, to promote air distribution among the wastewater, and further mixed by a mixer with variable rotation speed (n= 100 rpm). One small tubing inlet and one small tubing outlet with threaded valves will be installed to control the flow of fluid through the bioreactor. The Bioreactor provided a location where biological degradation of the wastewater constituents takes place. Initially, microorganisms oxidize the carbon compounds in the wastewater to produce carbon dioxide, new cells and biomass. Likewise in the Nitrification, the ammonia (NH) is also oxidized to nitrate (NO) for which pumped oxygen is required. Then, under anoxic conditions, nitrate (NO) is further converted into nitrogen (N) and oxygen (O) through Denitrification. From the Bioreactor, the treated flows will be passed to the settling tank where a fraction of the settled biomass is recycled to the Bioreactor while, the reminder biomass (excessive sludge) will be pumped out of the tank to keep a constant concentration of Total Solids in Bioreactor. Operating the Bench Plant: Upon bench setting-up and the synthetic preparation phases, the plant was inoculated with an activated sludge from a municipal wastewater treatment plant. After an adaptation period of 8 weeks, the TS concentration was adjusted, in the activated sludge reactor, to TS 3.5g/l at a sludge load of (0.05 kg BOD/kg TS.d). The excess sludge was discharged from the plant once a week, in this case; the TS-increase was substantially represented by an increase in the sludge level in the secondary clarifier. Thus, the setting of a TS content of 3.5 g/l in the system was possible. By volume and measurements of TS in the return sludge (TS), the excess sludge (TSExcess) and drain (TSEff.) were detected. As the dry matter concentration in the plant effluent (TSEff.) was very low accompanied by high Effluent rate flow, samples were filtered to control the TS-measurement error (due to low dry mass low). In addition, the bench scale plant tests were operated at a temperature of 20°C, a constant pH of 7.0 and a dissolved oxygen concentration of 5 mg/l. These parameters were daily checked and adjusted as necessary. Sampling and Measurements: As, wastewater sampling at various points in the treatment process is useful in evaluating operation efficiency, samples has been collected from the storage tank, reactors, aeration tank, settling tank and excessive sludge a period of six months; as shown in figure-3 and table-2. In addition, the exact measurement of the sludge blanket level with respect to location, time of day has been exercised to establish the exact sludge volume and eventually performing the carbon mass balance. International Research Journal of Environment Sciences ______________________________________________ISSN 2319–1414Vol. 4(12), 8-16, December (2015) Int. Res. J. Environment Sci. International Science Congress Association 11 Figure-3 Sampling and Measurements PointsProcedure for Establishing the Carbon Balance: From Activated Sludge System mass balance; the solids entering the system will equal the solids leaving the system. ExcessSlugSTincreaseBiomassATcreasBiomaExhaustGasEffluentAirInfluent + = + sinWhere: TOC InfluentInfluentTOCRotameterair, RatioCoAirAirExhaustGasFor complete balancing of the carbon analysis of the sludge is necessary. The empirical formula for bacteria as indicated with C5H7O2N /HAR89/. The proportion of carbon in the biomass amounts to 53% thereafter. This corresponds to Schlegel /SCH85/, indicating 50% for single-celled organisms 0.271 4412RatioThe CO will be quantified from the Q Air Mass balances can be used to mathematically define the accumulation in the Aeration Tank/ Bioreactor as follows: ATATTSATincreaseBiomassBeginATEndATTSTSATTS - = D By monitoring the depth of the sludge blanket in the Settling Tank and the concentration within different layers, the accumulation in the settling tank is calculated as follows: STTSSTSTincreaseBiomassD×D×beginSTEndSTBeginSTEndSTTSTSATTS - = D And finally, the daily wasted excessive sludge mass: ExcessTSExcessExcess International Research Journal of Environment Sciences ______________________________________________ISSN 2319–1414Vol. 4(12), 8-16, December (2015) Int. Res. J. Environment Sci. International Science Congress Association 12 Table-2 Parameter MeasurementsParameter Measurements Standard/ Equipment Description/Significance Frequency TOC TOCOR 5000TOC measures the organic carbon concentration in the wastewater. Sample is introduced in the combustion tube, which is filled with an oxidation catalyst and heated to 680°C. In the samples, carbon is first converted to CO by the combustion furnace for TOC and TC analysis. (TOC = TC – TIC) Daily BOD DIN38409-H51Biochemical Oxygen Demand (BOD) is a test to measure the dissolved oxygen (DO) content , while being incubated under controlled conditions (20°C) for 5 days (hence BOD) and then the DO is measured again. The drop in DO is the measure of the BOD. Weekly Temperature OXI 91 In general, in warm temperatures, biological treatment activity accelerates and slows in cool temperatures. Meanwhile, the process can totally stop in extreme hot or cold atmosphere. Daily pH pH 91 The “pH” approximates the concentration of the hydrogen ion in the solution. pH is measured on a scale of 0 to 14, as lower values indicating high H+ (more acidic) and higher values indicating low H+ ion activity (less acidic). While, a pH of 7 is counted as neutral.Daily Flow Rate Flow meter Wastewater flow rates will be monitored and recorded for purposes of evaluating the Bench plant performance. Daily TSS concentration DIN38414-S2A well- mixed sample is filtered using a weighed standard glass-fiber filter. Under 105°C, the residue retained on the filter is dried to a constant weight. The increase in weight of the filter represents the total suspended solids. In case the suspended material clogs the filter and prolongs filtration. An estimate of the total suspended solids may be induced from the difference between the total solids and the total dissolved solids. Daily OXI 91Sufficient D.O. is required for the operation of many wastewater treatment processes. In essence, the D.O. is continuously monitored in the activated sludge tanks. A dissolved oxygen meter is an electronic device that converts signals from a probe that is placed in the water into units of DO in milligrams per liter. The probe is filled with a salt solution and has a selectively permeable membrane that allows DO to pass from the stream water into the salt solution. The DO that has diffused into the salt solution changes the electric potential of the salt solution and this change is sent by electric cable to the meter, which converts the signal to milligrams per liter on a scale that can be read. Daily International Research Journal of Environment Sciences ______________________________________________ISSN 2319–1414Vol. 4(12), 8-16, December (2015) Int. Res. J. Environment Sci. International Science Congress Association 13 Results and Discussion Samples were collected from the bench scale plant over two different periods of 75 days each: summer (29.07.2014 to 15.10.2014) and (01.11.2014 to 15.01.2015), as shown in tables-3 and 4 respectively. Table-3 Collected Data for the First periodSample TOCInf. [g/l]TOCEff. [g/l]MLSSBR[g/l]MLSSExcess[g/l]MLSSEff.[g/l]CO2[%] 29-Jul. 346 25 3.42 3.68 23 0.5 2-Aug. 340 18 3.39 3.63 25 0.4 5-Aug. 351 24 3.45 3.71 19 0.5 12-Aug. 347 26 3.53 3.58 17 0.5 17-Aug. 344 19 3.65 3.54 20 0.5 19-Aug. 352 18 3.4 3.6 22 0.5 22-Aug. 346 20 3.46 3.57 20 0.6 27-Aug. 343 16 3.56 3.7 24 0.4 1-Sept. 349 17 3.5 3.8 20 0.5 6-Sept. 351 14 3.6 3.75 25 0.6 12-Sept. 349 18 3.56 3.69 21 0.5 15-Sept. 343 15 3.5 3.5 23 0.4 18 Sept. 332 14 3.5 3.61 20 0.5 21 Sept. 345 9 3.59 3.62 21 0.5 24 Sept. 323 7 3.64 3.7 20 0.4 28-Sept. 375 17 3.7 3.9 18 0.5 1-Oct. 368 17.5 3.41 3.4 19 0.4 5-Oct. 350 10 3.38 3.38 21 0.5 10-Oct. 345 13 3.45 3.35 20 0.5 15-Oct. 340 13 3.4 3.4 19 0.5 International Research Journal of Environment Sciences ______________________________________________ISSN 2319–1414Vol. 4(12), 8-16, December (2015) Int. Res. J. Environment Sci. International Science Congress Association 14 Table-4 Collected Data for the Second PeriodSample TOCInf. [g/l]TOCEff. [g/l]MLSSBR[g/l]MLSSExcess[g/l]MLSSEff.[g/l]CO2[%] 1-Nov. 348 13 3.61 3.8 20 0.4 5-Nov. 340 12 3.66 3.77 19 0.4 10-Nov. 325 13 3.71 3.9 20 0.4 11-Nov. 320 12 3.39 3.6 20 0.4 15-Nov. 324 13 3.43 3.7 20 0.5 18-Nov. 350 20 3.39 3.5 25 0.5 21-Nov. 343 23 3.4 3.52 23 0.5 25-Nov. 338 19 3.38 3.5 22 0.6 28-Nov. 330 25 3.41 3.56 24 0.4 2-Dec. 350 27 3.43 3.6 22 0.5 6-Dec. 342 29 3.5 3.66 23 0.5 10-Dec. 340 22 3.53 3.7 21 0.4 14-Dec. 335 25 3.55 3.7 25 0.5 18-Dec. 310 20 3.45 3.8 20 0.4 21-Dec. 350 25 3.38 3.7 23 0.5 25-Dec. 342 17 3.4 3.8 21 0.5 28-Dec. 340 19 3.4 3.9 20 0.4 3-Jan. 360 22 3.5 4 22 0.5 6-Jan. 350 18 3.65 4.2 20 0.5 9-Jan. 365 20 3.5 4.3 23 0.5 12-Jan. 360 24 3.6 4.2 22 0.6 15-Jan. 365 21 3.6 4.3 25 0.5 International Research Journal of Environment Sciences ______________________________________________ISSN 2319–1414Vol. 4(12), 8-16, December (2015) Int. Res. J. Environment Sci. International Science Congress Association 15 Carbon Balance for the First Period of Study: Carbon Mass Balance: Bench-Scale Plant 29.07.2014 - 15.10.2014 (75 Days) m Influent = 40 l/d TOC Influent = 0,35 g/l IC Influent = 0 g/l V Excess Sludge = 10 l/75 d MLSS Excess Sludge = 3,5 - 3,7 g/l MLSS - Increase Sedimentation Tank =0,2 g/l in 75 d V Sludge, Sedimentation Tank = 15 l m Effluent = 40 l/d TOC Effluent = 0,015 g/l IC Effluent = 0,005 g/l m Air = 0,2 m 3 /h r CO2 = 1,739 g/l 27,3 % C per Mol CO 2 Exhaust Gas, CO 2 = 0,5 Vol.% Car bon Content in Biomass: 0,5 g C/g MLSS MLSS Reactor = 3,5 - 3,6 g/l MLSS - Increase Reactor = 0,1 g/l in 75 d V Reactor = 70 l TOC Reaktor, 29.07.2014 = 0,03 g/l IC Reaktor, 29.07.2014 = 0,02 g/l TOC Reaktor, 15.10.2014 = 0,045 g/l IC Reaktor, 15.10.2014 = 0,02 g/l (TOC - and IC - increase in the reactor neglected) Mass Balance: Influent+mAir=mEffluent+ mExhaust Gas+mBiomass-Increase Reactor+ mBiomass-Increase Sedimentation Tank+ mExcess SludgeInfluent: mInfluent = 0,33 g TOC/l X 40 l/d = 13,2 g C/d Effluent:mEffluent = 0.02 g (TOC+IC)/l X 40 l/d = 0,8 g C/d Air: mAir = 0 g TC/mwhere,0 g C/d (assumption)Exhaust Gas: mExhaust Gas = 0,5 Vol.% CO at 0,2 m³/h = 4,8 m³/d0,5/100 X 4,8 m/d = 0,024 m/d = 24 l CO2 /d mExhaust Gas=24 l CO/d X 1,739 g/l = 43,03 g CO/d X 27,3/100 g C/g CO = 11,4 g C/d Biomass - increase Reactor: Biomass Increase Reactor = 70l X 0,5 g C/g MLSS X 0,1 gMLSS/l 75d = 0,046 g C/d Biomass - increase Sedimentation Tank: Sedimentation Tank =15 l X 0,5 g C/g MLSS X 0,2 g MLSS/l 75d = 0,02 g C/d Excess Sludge: mExcess Sludge = 10l X 0,5 g C/g MLSS X 3,7 g/l / 75d = 0,246 g C/d Total: mEffluent+mExhaust Gas+mBiomass-Increase, Reactor+mBiomass-Increase, Sedimentation Tank+mExcess Sludge= (0,8+11,4+0,046+0,02+0,246) g C/d = 12,512 g C/d Closure of the Carbon Mass Balance: 100 % X 12,512 g C/d / 13,2 g C/d =94,7 % Carbon Balance for the Second Period of Study: Carbon Mass Balance: Bench-Scale Plant 01.11.2014 - 15.01.2015 (75 Days) m Influent = 40 l/d TOC Influent = 0,35 g/l I C Influent = 0 g/l V Excess Sludge = 10 l/75 d MLSS Excess Sludge = 3,81 g/l MLSS - Increase Sedimentation Tank =0,2 g/l in 75 d V Sludge, Sedimentation Tank = 15 l m Effluent = 40 l/d TOC Effluent = 0,015 g/l IC Effluent = 0,005 g/l m Air = 0,2 m 3 / h r CO2 = 1,739 g/l 27,3 % C per Mol CO 2 Exhaust Gas, CO 2 = 0,5 Vol.% Carbon Content in Biomass: 0,5 g C/g MLSS MLSS Reactor = 3,5 - 3,6 g/l MLSS - Increase Reactor = 0,1 g/l in 75 d V Reactor = 70 l TOC Reaktor, 01.11.2014 = 0,03 g/l IC Reaktor, 01 .11.2014 = 0,02 g/l TOC Reaktor, 15.01.2015 = 0,045 g/l IC Reaktor, 15.01.2015 = 0,02 g/l (TOC - and IC - increase in the reactor neglected) International Research Journal of Environment Sciences ______________________________________________ISSN 2319–1414Vol. 4(12), 8-16, December (2015) Int. Res. J. Environment Sci. International Science Congress Association 16 Mass Balance: Influent + mAir = mEffluent + mExhaust Gas +mBiomass-Increase Reactor + Biomass-Increase Sedimentation Tank+ mExcess SludgeInfluent: mInfluent = 0,33 g TOC/l X 40 l/d = 13,2 g C/d Effluent: mEffluent = 0.02 g (TOC+IC)/l X 40 l/d = 0,8 g C/d Air: mAir = 0 g TC/mwhere,0 g C/d (assumption)Exhaust Gas: mExhaust Gas = 0,5 Vol.% CO at 0,2 m³/h = 4,8 m³/d 0,5/100 X 4,8 m/d = 0,024 m/d = 24 l CO /d Exhaust Gas=24 l CO/d X 1,739 g/l = 43,03 g CO/d X 27,3/100 g C/g CO = 11,4 g C/d Biomass - increase Reactor: Biomass Increase Reactor = 70l X 0,5 g C/g MLSS X 0,15 gMLSS/l 75d = 0,07 g C/d Biomass - increase Sedimentation Tank: mSedimentation Tank =15 l X 0,5 g C/g MLSS X 0,2 g MLSS/l 75d = 0,02 g C/d Excess Sludge: mExcess Sludge = 10l X 0,5 g C/g MLSS X 3,81 g/l / 75d = 0,254 g C/d Total: mEffluent+mExhaust Gas+mBiomass-Increase, Reactor+mBiomass-Increase, Sedimentation Tank+mExcess Sludge= (0,8+11,4+0,046+0,02+0,254) g C/d = 12,544g C/d Closure of the Carbon Mass Balance: 100 % X 12,544 g C/d / 13,2 g C/d =95,03 % In order to close the carbon mass balance in the activated sludge system, adding the bioaccumulation term for the AT and the Sedimentation Tank is a necessity. Analysis of data collected for both periods under consideration revealed that, on average, a 95% carbon balance closure can be achieved. More specifically, a realistic result of 85% of the encountered carbon was found in the form of CO; which is caused by the oxidation reaction. Meanwhile, the missing 5% of carbon can be mainly attributed to activated sludge carbon adsorption and to errors in measurements of TS (pressure filtration) in AT and Sedimentation Tank. Although the accumulation term can be of noticeable effect when performing carbon mass balance over the two periods, it is of minor influence when considering long periods of study. Furthermore, the work reported in this research improves upon the existing carbon mass balance; as by comparing the data of Geissen , found there was 85% of carbon balance closure in bio-systems. Finally, the results from the bench-scale show that the suggested method can obtain the exact amounts of produced CO2 from the activated sludge process which, in turn, forms an addition to GHG. Conclusion The bench-scale bioreactor established in this study allowed in-depth research to be executed on the activated sludge process with a special focus on the fate of carbon across the system. In which, the fate and the mass balance of the carbon during the activated sludge process was investigated taken into account the accumulation in both the Aeration and Sedimentation Tanks. Results from this research achieved a 95% closure of carbon balance in the activated sludge. Moreover, in the light of the findings set out in this study based on the development of a bench scale unit, the amounts of CO2 generated from real life wastewater treatment plant can be estimated. 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