Sequencing Batch Reactor Reactor Research Articles

Sequencing batch reactor enhances bacterial hydrolysis of starch promoting continuous bio-hydrogen production from starch feedstock

Bio-hydrogen production from starch was carried out using a two-stage process combining thermophillic starch hydrolysis and dark H 2 fermentation. In the first stage, starch was hydrolyzed by Caldimonas taiwanensis On1 using sequencing batch reactor (SBR). In the second stage, Clostridium butyricum CGS2 was used to produce H 2 from hydrolyzed starch via continuous dark hydrogen fermentation. Starch hydrolysis with C. taiwanensis On1 was operated in SBR under pH 7.0 and 55 °C. With a 90% discharge volume, the reducing sugar (RS) production from SBR reactor reached 13.94 g RS/L, while the reducing sugar production rate and starch hydrolysis rate was 0.92 g RS/h/L and 1.86 g starch/h/L, respectively, which are higher than using other discharge volumes. For continuous H 2 production with the starch hydrolysate, the highest H 2 production rate and yield was 0.52 L/h/L and 13.2 mmol H 2/g total sugar, respectively, under a hydraulic retention time (HRT) of 12 h. The best feeding nitrogen source (NH 4HCO 3) concentration was 2.62 g/L, attaining a good H 2 production efficiency along with a low residual ammonia concentration (0.14 g/L), which would be favorable to follow-up photo H 2 fermentation while using dark fermentation effluents as the substrate.

축산폐수의 후처리공정으로서 SBR 적용시 운전인자에 따른 질소와 인의 제거특성에 관한 연구

This study examined the removal efficiency of the nitrogen and phosphorus in order to compensate for the combined process of ATAD(Autothermal Thermophilic Aaerobic Digestion) and EGSB(Expended Granular Sludge Bed), which are treatment methods for livestock wastewater, by introducing SBR(Sequencing Batch Reactor) as post-treatment process. The analysis on the treatment efficiency of each operation mode showed that, in the case of T-N, the treatment efficiency were 67.1% and 74.2% for Run-1 and Run-2, respectively, and in the case of T-P, the values were 71.2 and 74.1, respectively, which are indicating that the treatment efficacy is higher in the condition of Run-1, in which the time period of Anoxic and Aerobic segments were increased. In addition, the result of analyzing removal characteristics of nitrogen and phosphorus by Influx load showed that removal efficiency of nitrogen was better in the case of high influx load than in the case of low influx load. Regardless of Influx load, phosphorus showed constant influx concentration, so that removal efficiency of phosphorus was influenced littler by Influx load than that of nitrogen. This study also fed methanol as an external carbon source and performed experiment to induce denitrification under anoxic condition by using nitrate among nitrogen compounds of SBR reactor, and the results showed that intermittent feeding was more effective in Nitrogen Removal than composite feeding.

Optimizing sequencing batch reactor (SBR) reactor operation for treatment of dairy wastewater with aerobic granular sludge

The biological wastewater treatment using aerobic granular sludge is a new and very promising method, which is predominantly used in SBR reactors which have higher volumetric conversion rates than methods with flocculent sludge. With suitable reactor operation, flocculent biomass will accumulate into globular aggregates, due to the creation of increased substrate gradients and high shearing power degrees. In the research project described in this paper dairy wastewater with a high particle load was treated with aerobic granular sludge in an SBR reactor. A dynamic mathematical model was developed describing COD and nitrogen removal as well as typical biofilm processes such as diffusion or substrate limitation in greater detail. The calibrated model was excellently able to reproduce the measuring data despite of strongly varying wastewater composition. In this paper scenario calculations with a calibrated biokinetic model were executed to evaluate the effect of different operation strategies for the granular SBR. Modeling results showed that the granules with an average diameter of 2.5 mm had an aerobic layer in between 65-95 microm. Density of the granules was 40 kgVSS/m3. Results revealed amongst others optimal operation conditions for nitrogen removal with oxygen concentrations below 5 gO2/m3. Lower oxygen concentrations led to thinner aerobic but thicker anoxic granular layers with higher nitrate removal efficiencies. Total SBR-cycle times should be in between 360-480 minutes. Reduction of the cycle time from 480 to 360 minutes with a 50% higher throughput resulted in an increase of peak nitrogen effluent concentrations by 40%. Considering biochemical processes the volumetric loading rate for dairy wastewater should be higher than 4.5 kgCOD/(m3*d). Higher COD input load with a COD-based volumetric loading rate of 9.0 kgCOD/(m3*d) nearly led to complete nitrogen removal. Under different operational conditions average nitrification rates up to 5 gNH/(m3*h) and denitrification rates up to 3.7 gNO/(m3*h) were achieved.

Characteristics of nitrogen and phosphorus removal in SBR and SBBR with different ammonium loading rates

Laboratory scale experiments were conducted to study the deterioration of enhanced biological phosphorus removal (EBPR) due to influent ammonium concentration, and to compare the performance of two types of sequencing batch reactor (SBR) systems, a conventional SBR and sequencing batch biofilm reactor (SBBR). Both in SBR and SBBR, the total nitrogen removal efficiency decreased from 100% to 53% and from 87.5% to 54.4%, respectively, with the increase of influent ammonium concentration from 20 mg/l to 80 mg/l. When the influent ammonium concentration was as low as 20 mg/l (C: N: P=200: 20: 15), denitrifying glycogen-accumulating organisms (DGAOs) were successfully grown and activated by using glucose as a sole carbon source in a lab-scale anaerobic-oxic-anoxic (A2O) SBR. In the SBR, due to the effect of incomplete denitrification and pH drop, the nitrogen and phosphorus removal efficiency decreased from 77% to 33.3% when the influent ammonium concentration increased from 20 mg/l to 80 mg/l. However, in the SBBR, simultaneous nitrification/denitrification (SND) occurred, and the nitrification rate in the aerobic phase did not change remarkably in spite of the increase in influent ammonium concentration. Phosphorus removal was not affected by the increase of influent ammonium concentration.

Biodegradation of phenolic mixtures in a sequencing batch reactor

In this study, attention was focused on substituted phenols because of their widespread presence in industrial effluents originating from many different sources: they are major constituents of wastewater from coal conversion processes, coke ovens, petroleum refineries and petrochemical industries, resin and fibreglass manufacturing and herbicide production. Moreover, for their characteristics of toxicity to humans and aquatic life (1 mgl(-1) is enough to detect the effects), they are included in the USEPA list of priority pollutants. Toxicity is higher in substituted phenols and is dependent on the nature and numbers of substituent groups. Objective of the present paper is to give a contribution to the modelling of phenolic mixture biodegradation by kinetic studies in which the different compounds are followed separately: this can be easily attained with an experimental apparatus such as the Sequencing Batch Reactor (SBR). Two substituted phenols, 4-nitrophenol (4NP) and 3,4-dimethylphenol (3,4DMP), were utilized as substrates and their degradation kinetics were investigated to evaluate the process parameters both in single compound and in mixture tests. Single compound and mixture kinetic tests have been carried out during the reaction phase of the working cycle of the SBR reactor. The single substrates and their mixture were utilized as sole carbon and energy sources. Moreover, in order to verify data reproducibility, all kinetic tests have been carried out in at least two replicates under the same operating conditions. Kinetic data showed the presence of substrate inhibition, to model this experimental evidence the Haldane equation, that is usually employed for substrate inhibited kinetics, was rearranged in a different form with parameters which have a precise meaning in relation to the process kinetics and, at the same time, make the integration procedure easier. The derivation of the equation is shown in an Appendix at the end of the paper. Kinetic parameters obtained are suitable for application. It was observed that the 4-nitrophenol removal rate in single compound tests is significantly higher than the 3,4-dimethylphenol removal rate in the whole range of investigated concentrations (up to 80 mg COD l(-1)). A faster 4-nitrophenol biodegradation was also observed in mixture tests. Moreover, it is worth noting that the two compounds were simultaneously degraded and no diauxic growth was observed. The comparison between single compound and mixture degradation kinetics showed that the 4-nitrophenol degradation rate was comparable in the two cases while a significantly beneficial effect (by increase by about 80% of the maximum removal rate) was detected for 3,4-dimethylphenol degradation in the mixture. Results of this study showed that the biodegradation kinetics of substituted phenols in mixture can be significantly different from that observed in single compound tests: in fact, the presence of a faster degradable compound (the 4NP) seems to exert a positive effect on the removal of a slower degradable compound (the 3,4DMP). The higher removal rate detected for 4NP, both in single compound and mixture tests, confirmed the key role of the biomass acclimatization in determining the biodegradation kinetics of xenobiotic compounds. The experimental approach and the original method applied for data analysis are of general validity and can be extended to the investigation of different classes of compounds. A relevant aspect related to the process applicability is the demonstrated possibility of easily adapting an enriched culture grown on a specific xenobiotic (in our case the 4NP) for the removal of similar single compounds or in mixtures. When biological process are considered for xenobiotic removal, this suggests a possible strategy of developing enriched cultures on target compounds that can be efficiently utilized on more complex matrices with reduced start up and acclimatization periods.

Development of a 2-sludge, 3-stage system for nitrogen and phosphorous removal from nutrient-rich wastewater using granular sludge and biofilms

A novel 2-sludge 3-stage process using a combination of granular sludge and biofilm was developed to achieve biological removal of nitrogen and phosphorus from nutrient-rich wastewater. The system consists of a granular sequencing batch reactor (SBR) working under alternating anaerobic/anoxic conditions supplemented with a short aerobic phase and an aerobic biofilm SBR. The wastewater is first fed to the granular SBR reactor, where easily biodegradable carbon sources are taken up primarily by polyphosphate accumulating organisms (PAOs). The supernatant resulting from quick settling of the granular sludge is then fed to the biofilm SBR for nitrification, which produces oxidized nitrogen that is returned to the granular reactor for simultaneous denitrification and phosphorus removal. While maximizing the utilization of organic substrates and reducing operational costs, as do other 2-sludge processes previously reported in literature, the proposed system solves the bottleneck problem of traditional 2-sludge systems, namely high effluent ammonia concentration, due to its high-volume exchange ratios. An ammonia oxidation rate of 32 mg N/L h was achieved in the biofilm SBR, which produced nitrite as the final product. This nitrite stream was found to cause major inhibition on the anoxic P uptake and also to result in the accumulation of N 2O. These problems were solved by feeding the nitrite-containing stream continuously to the granular reactor in the anoxic phase. With a nitrogen and phosphorus removal efficiency of 81% and 94%, respectively, the system produces an effluent that is suitable for land irrigation from a wastewater stream containing 270 mg N/L of total nitrogen and 40 mg P/L of total phosphorus.

Nitrification–denitrification via nitrite in SBR using real-time control strategy when treating domestic wastewater

A lab-scale sequencing batch reactor (SBR) was employed to treat low C/N ratio municipal wastewater to investigate the stability of nitrification–denitrification via nitrite using a real-time control strategy to switch aeration on and off. Three parameters, pH, DO and ORP, were selected as control parameters in the SBR reactor operation. Nitrite accumulation was observed under real-time control conditions (NO 2 −-N/NO x −-N > 0.8), implying that nitrification–denitrification mainly via nitrite was achieved by the process control strategy applied. The nitrite concentration in the SBR decreased sharply when the SBR system was operated using a fixed time aeration control strategy for 7 days. Ammonia nitrogen concentration (NH 4 +-N) and temperature also affect nitrite accumulation. Ammonia shock loads limited nitrification due to alkalinity limitations, but the system recovered quickly from short-time high ammonia shock loads when the real-time control strategy was applied. Temperature was observed to affect nitrite accumulation rate when the real-time control strategy was used in the SBR reactor, with higher nitrite accumulation at 28 ± 0.5 °C (NO 2 −-N/NO x −-N = 0.84), compared to the accumulation at the ambient average temperature of 20 °C (NO 2 −-N/NO x −-N > 0.61).

Enrichment and granulation of Anammox biomass started up with methanogenic granular sludge

A sequencing batch reactor (SBR) seeded with methanogenic granular sludge was started up to enrich Anammox (Anaerobic Ammonium Oxidation) bacteria and to investigate the feasibility of granulation of Anammox biomass. Research results showed that hydraulic retention time (HRT) was an important factor to enrich Anammox bacteria. When the HRT was controlled at 30 days during the initial cultivation, the SBR reactor presented Anammox activity at t = 58 days. Simultaneously, the methanogenic granular sludge changed gradually from dust black to brown colour and its diameter became smaller. At t = 90 days, the Anammox activity was further improved. NH4+-N and NO2−N were removed simultaneously with higher speed and the maximum removal rates reached 14.6 g NH4+-N /(m3reactor·day) and 6.67 g NO2−-N /(m3reactor·day), respectively. Between t = 110 days and t = 161 days, the nitrogen load was increased to a HRT of 5 days (70 mg/l NH4+ and 70 mg/l NO2), the removal rates of ammonium and nitrite were 60.6% and 62.5% respectively. The sludge changed to red and formed Anammox granulation with high nitrogen removal activity.

Improving the performance of sequencing batch reactor (SBR) by the addition of zeolite powder

Two types of operation means “SBR reactor alone (control reactor)” and “adding zeolite powder into SBR reactor (test reactor)” were used to treat municipal wastewater. The test results revealed that zeolite powder addition could improve the activity of the activated sludge. It was investigated the specific oxygen utilization rate (SOUR) of the tested zeolite sludge were about double times that of the control activated sludge, and the nitrification rate and settling property of zeolite-activated sludge were both improved. Due to the combination of zeolite adsorption for NH 4 +-N and enhanced simultaneous nitrification and de-nitrification (SND), a higher nitrogen removal was observed in test reactor compared to the control reactor, and the addition of zeolite powder is helpful to inhabit sludge bulking. In addition, through long-term parallel shock load test, it was found that the zeolite powder addition could enhance the ability of activated sludge in resisting the shock load of organics and ammonium. Compared to the control activated sludge, zeolite powder added activated sludge could remove COD, NH 4 +-N, TN and TP significantly in a shorter cycle time. At the same operational time period, the test SBR could treat wastewater quantity 1.22 times that treated in control SBR.

Bioregeneration of powdered activated carbon in the treatment of alkyl-substituted phenolic compounds in simultaneous adsorption and biodegradation processes

The role of bioregeneration process in renewing the adsorbent surface for further adsorption of organics during simultaneous adsorption and biodegradation processes has been well recognized. The extent of bioregeneration of powdered activated carbon (PAC) as an adsorbent loaded with phenol, p-methylphenol, p-ethylphenol and p-isopropylphenol, respectively, in the simultaneous adsorption and biodegradation processes were quantitatively determined using oxygen uptake as a measure of substrate consumption. Bioregeneration phenomenon was also evaluated in the simultaneous adsorption and biodegradation processes under sequencing batch reactor (SBR) operation to treat synthetic wastewater containing 1200 mg l −1 phenol and p-methylphenol, respectively. The SBR systems were operated with FILL, REACT, SETTLE, DRAW and IDLE periods in the ratio of 4:6:1:0.75:0.25 for a cycle time of 12 h. The results show that the percentage of desorption from loaded PAC decreased in the order phenol > p-methylphenol > p-ethylphenol > p-isopropylphenol. For the treatment of phenol and p-methylphenol in the SBR reactors, respectively, the simultaneous adsorption and biodegradation processes were able to produce a consistent effluent quality of COD ⩽100 mg l −1 when the applied PAC dosage was 0.115 and 0.143 g PAC per cycle, respectively. When no further PAC was added, the treatment performance deteriorated to that of the case without PAC addition after 68 and 48 cycles of SBR operation, respectively, for phenol and p-methylphenol. This observation is consistent with the greater extent of bioregeneration for phenol-loaded PAC as compared to p-methylphenol-loaded PAC.

Enhanced nitrogen removal using C/N load adjustment and real-time control strategy in sequencing batch reactors for swine wastewater treatment

The laboratory-scale sequencing batch reactor (SBR) was used to study the effectiveness of an integrated strategy of real time control with C/N ratio adjustment for practical swine wastewater treatment. Swine waste was used as the external carbon source for continuous treatment in the SBR reactors. Oxidation-reduction potential and pH were used as parameters to control the continuous denitrification and nitrification process, respectively. A constant effluent quality could be obtained, despite drastic variations in the characteristics of influent wastewater. Also, a relatively complete removal of nutrients was always ensured, since the optimum quantity of the external carbon source could be provided for complete denitrification, and a flexible hydraulic retention time was achieved by the successful real-time control strategy. The average removal efficiencies of total organic carbon and nitrogen were over 94% and 95%, respectively.

Treatment of phenolic wastewater using agricultural wastes as an adsorbent in a sequencing batch reactor

The objective of this study is to investigate the potential of the activated rice husk to be used as an alternative adsorbent to powdered activated carbon (PAC) in the simultaneous adsorption and biodegradation processes under sequencing batch reactor (SBR) operation to treat synthetic wastewater containing phenol, p-methylphenol, p-ethylphenol and p-isopropylphenol. The rice husk (PRH) was activated by pyrolysis at 600 degrees C for 5 hours in a nitrogen atmosphere. Using the Langmuir model, the limiting adsorption capacities of PRH for the phenols were found to vary from 0.015-0.05 of those of PAC. The SBR reactors with and without adsorbent addition were operated with fill, react, settle, draw and idle periods in the ratio of 4:6:1:0.76:0.25 for a cycle time of 12 hours. For phenolic wastewater containing, 1,200 mg/L phenol, 1,200 mg/L p-methylphenol, 800 mg/L p-ethylphenol and 660 mg/L p-isopropylphenol, it was found that the biodegradation process alone was unable to produce effluent of quality which would satisfy the discharge standards of COD < or = 100 mg/L and phenol concentration < or = 1 mg/L. The addition of PAC in the ratio of PAC/phenolic compound at 0.095 g/g for phenol, 0.119 g/g for p-methylpheol, 0.179 g/g for p-ethylphenol and 0.220 g/g for p-isopropylphenol, can improve the effluent quality to satisfy the discharge standards. Equivalent treatment performance was achieved with the use of PRH at dosages of 2-3 times higher than those of PAC for all the phenolic wastewater studied. The increased adsorption capacity of PRH shown in the treatment indicates bioregeneration of the adsorbed surface during the treatment process.

A new sequencing batch reactor for treatment of municipal sewage wastewater for agricultural reuse

Treatment of municipal sewage wastewater for possible agricultural reuse was investigated. The treatment method consisted of chemical coagulation and sequencing batch reactor (SBR) system. A new type of SBR reactor was designed which allows continuous wastewater inflow in contrast to intermittent wastewater feeding of the traditional one. Experimental tests were performed using both SBR treatment systems. The results show that both SBR treatment systems perform equally well. The influences of the various operating parameters on the water quality were determined for the new as well as for the traditional SBR reactors. The combined chemical coagulation and SBR treatment were found to be quite satisfactory to meet the agricultural irrigation standards for the discharged water.

Morphological characteristics of microbial sludge performing enhanced biological phosphorus removal in a sequencing batch reactor fed with glucose as sole carbon source

Electron microscopic analysis was used to analyse the morphological characteristics of microbial sludge performing enhanced biological phosphorus removal (EBPR) in an anaerobic/aerobic sequencing batch reactor (SBR) fed with glucose as the sole carbon source. The amounts of phosphate release and uptake during the SBR cycle gradually increased with operation time and complete EBPR was achieved after about 90 days. Scanning electron microscopy (SEM) showed that the initial sludge inoculated into the SBR consisted of various microorganisms such as coccus-, rod- and bacillus-shaped bacteria, but after extended operation (more than 650 days) perpendicular cuboidal bacteria of eight coccus-shaped cells dominated the microbial sludge in the SBR reactor. The cell size of the cuboidal bacteria was about 0.7 μm in diameter. In the sludge, coccus- and rod-shaped bacteria also existed but at much lower frequency. Transmission electron microscopy (TEM) also revealed that the cuboidal bacteria dominated the sludge, but they did not contain polyphosphate granules or glycogen inclusions. The rod-shaped bacteria did not contain polyphosphate granules or glycogen inclusions either. Only coccus-shaped bacteria with a diameter of about 1.2 μm contained small black polyphosphate granules and a large white inclusion. Based on previously proposed metabolic pathways and electron microscopic results, it was inferred that the dominating cuboidal bacteria were lactic acid producing organisms (LPO) and the coccus-shaped bacteria were lactate-using phosphorus accumulating organisms (PAO).

Acidogenic Activity: Process of Carbon Source Generation for Biological Nutrient Removal

In this study, a sequencing batch reactor (SBR) connected with a two step anaerobic digestion system is proposed in order to investigate the possibility of simultaneous C, N and P removal from wastewater. The system was studied using synthetic wastewater. In this system, the effluent of nitrate from the SBR reactor is added to the acidogenic reactor influent. Nitrate elimination and VFA production are then achieved together in the acidogenic reactor. The performances of three lab-scale reactors, operated for C, N and P biological removal are analyzed. The removals of TOC, TN and TP-PO4 were greater than 96%, 75% and 86%, respectively. The results show that the combination of anaerobic digestion in two step-SBR treatment is effective for simultaneous C, N and P removal. The benefits from this process are the saving of carbon source for denitrification and phosphorus removal. Reactor arrangement made possible the existence of zones where the different bacterial populations involved could coexist. Complete denitrification occurs in acidogenic reactor and hence the methanogenic activity is not reduced nor inhibited by N-NO3 presence, allowing greater TOC removal. A stable P-release and P-uptake took place after coupling of the three reactors. Furthermore, a fast settling, compact sludge is generated in the SBR with the operational conditions applied.

Acidogenic activity: Process of carbon source generation for biological nutrient removal

In this study, a sequencing batch reactor (SBR) connected with a two step anaerobic digestion system is proposed in order to investigate the possibility of simultaneous C, N and P removal from wastewater. The system was studied using synthetic wastewater. In this system, the effluent of nitrate from the SBR reactor is added to the acidogenic reactor influent. Nitrate elimination and VFA production are then achieved together in the acidogenic reactor. The performances of three lab-scale reactors, operated for C, N and P biological removal are analyzed. The removals of TOC, TN and TP-PO 4 were greater than 96%, 75% and 86%, respectively. The results show that the combination of anaerobic digestion in two step-SBR treatment is effective for simultaneous C, N and P removal. The benefits from this process are the saving of carbon source for denitrification and phosphorus removal. Reactor arrangement made possible the existence of zones where the different bacterial populations involved could coexist. Complete denitrification occurs in acidogenic reactor and hence the methanogenic activity is not reduced nor inhibited by N-NO 3 presence, allowing greater TOC removal. A stable P-release and P-uptake took place after coupling of the three reactors. Furthermore, a fast settling, compact sludge is generated in the SBR with the operational conditions applied.

Simultaneous removal of carbon, nitrogen and phosphorus from wastewater by coupling two-step anaerobic digestion with a sequencing batch reactor

The objective of this study was to develop an integrated process for simultaneous removal of carbon, nitrogen and phosphorus from industrial wastewaters. The process consisted of a-two step anaerobic digestion reactor, for carbon removal, coupled with a sequencing batch reactor (SBR) for nutrient removal. In the proposed process, carbon is eliminated into biogas by anaerobic digestion: acidogenesis and methanogenesis. The volatile fatty acids (VFA) produced during the first step of anaerobic digestion can be used as electron donors for both dephosphatation and denitrification. In the third reactor (SBR) dephosphatation and nitrification are induced through the application of an anaerobic–aerobic cycle. This paper describes the first trials and experiments on the SBR and a period of 210 days during which the SBR was connected to the acidogenic and methanogenic reactors. It was shown that nitrification of ammonia took place in the SBR reactor, during the aerobic phase. Furthermore, denitrification and VFA production were achieved together in the acidogenic reactor, when the efflux of nitrates from the SBR reactor was added to the first reactor influx. The proposed process was fed with a synthetic industrial wastewater, the composition of which was: total organic carbon (TOC)=2200 mg dm−3, total Kjeldahl nitrogen (TKN)=86 mg dm−3, phosphorus under phosphate form (P-PO4)=20 mg dm−3. In these conditions, removals of carbon, nitrogen and phosphorus were 98%, 78% and 95% respectively. The results show that the combination of the two-step anaerobic digestion reactor and an SBR reactor is effective for simultaneous carbon, nitrogen and phosphorus removal. Reactor arrangements enabled zones of bacterial populations to exist. Complete denitrification occurred in the acidogenic reactor and hence the anaerobic activity was not reduced or inhibited by the presence of nitrate, thus allowing high TOC removal. Stable phosphorus release and phosphorus uptake took place in the SBR after coupling of the three reactors. A fast-settling compact sludge was generated in the SBR with the operational conditions applied, thus giving good separation of supernatant fluid. The benefits from this process are the saving of (i) an external carbon source for denitrification and phosphorus removal, (ii) a reactor for the denitrification step. © 1998 Society of Chemical Industry

Combined biodegradation of carbon, nitrogen and phosphorus from wastewaters

The objective of this study was to develop an integrated system for simultaneous removal of carbon, nitrogen and phosphorus from industrial wastewaters. The system consisted a two step anaerobic digestion reactor for carbon removal coupled with a sequencing batch reactor (SBR) for nutrient removal. In the proposed system, carbon is converted into biogaz by methanogenic activities. The volatile fatty acids (VFA) produced during the first step of anaerobic digestion were used as electron donors for biological dephosphatation in the SBR in which anaerobic and aerobic phases were cyclically applied. It was shown that nitrification of ammonia took place in the SBR reactor, during the aerobic phase. Furthermore, denitrification and VFA production were achieved together in the acidogenic reactor, when the efflux of nitrate from the SBR is added to the acidogenic influx. The proposed process was fed with a synthetic wastewater with composition characteristics: Total Organic Carbon (TOC)=2200 mg l −1; Total Kjedahl Nitrogen (TKN)=86 mg l −1; Phosphorus under phosphate form (P–PO 4)=20 mg l −1). In these conditions, the removal of carbon, nitrogen and phosphorus were 98%, 78% and 95%, respectively. The benefits from the system are the saving of (i) an external carbon source for denitrification and dephosphatation, (ii) a reactor for the denitrification step.

Emission of nitrous oxide from high-rate nitrification and denitrification by mixed liquor circulating process and sequencing batch reactor process

Laboratory scale models simulating a mixed liquor circulating (MLC) process and a sequencing batch reactor (SBR) process were operated with a high ammonium volumetric loading to study the possible nitrous oxide (N2O) emission from them. The N2O emission from the MLC process was found to depend on the DO level in the aerobic reactor. When the DO level was high, the emission was negligibly small. The SBR reactor emitted N2O in a quantity as high as 40 percent of the removed nitrogen. Most of the emission occurred during the low DO period in the aeration stage.

Emission of nitrous oxide from high-rate nitrification and denitrification by mixed liquor circulating process and sequencing batch reactor process

Laboratory scale models simulating a mixed liquor circulating (MLC) process and a sequencing batch reactor (SBR) process were operated with a high ammonium volumetric loading to study the possible nitrous oxide (N2O) emission from them. The N2O emission from the MLC process was found to depend on the DO level in the aerobic reactor. When the DO level was high, the emission was negligibly small. The SBR reactor emitted N2O in a quantity as high as 40 percent of the removed nitrogen. Most of the emission occurred during the low DO period in the aeration stage.