Intermittently Aerated Sequencing Batch Reactor Research Articles

Start-up and optimization of a one-stage partial nitrification-anammox (PN-A) process treating low ammonium concentration wastewater: experimental results and modeling investigation.

Although the partial nitrification-anammox process (PN-A) has achieved great success in nitrogen removal for the high ammonium concentration wastewater, its application is still limited in low ammonium concentration wastewater treatment due to its instability and low nitrogen removal efficiency. In this study, a sequencing batch reactor (SBR) with continuous aeration was employed to enrich ammonia oxidation bacteria (AOB) and suppress nitrite oxidation bacteria (NOB) first; then, the SBR was operated intermittently aerated SBR (IASBR), to which the anammox granular sludge (AMX) was added to achieve complete autotrophic nitrogen removal under low influent ammonium concentration of 100mg/L. A mathematical model was used to optimize the IASBR aeration strategy to achieve sub-optimal nitrogen removal. The experimental results showed that high nitrite accumulation efficiency (above 80%) in the SBR and a fast start-up within 100days and a stable TN (total nitrogen) removal efficiency of 70% were achieved in the IASBR. Meanwhile, the simulation results indicated that keeping aeration duration at 4h, kLa (oxygen transfer coefficient) at 50day-1, or aeration duration at 2.5h, kLa at 80day-1 could obtain a higher total nitrogen removal efficiency (TNR) (TNR > 80%), and the TN removal could also be improved by increasing hydraulic retention time (HRT) under the optimal oxygen supply rate.

Start up of partial nitritation-anammox process using intermittently aerated sequencing batch reactor: Performance and microbial community dynamics

This study investigated the performance and microbial community dynamics of a start-up method for the partial nitritation-anammox (PN-A) process: start-up from return sludge in an intermittently aerated sequencing batch reactor (IASBR). The robustness of this PN-A IASBR system in achieving long-term efficient nitrogen removal was also investigated. Stable partial nitritation with nitrite accumulation ratio of about 80% was firstly achieved in the IASBR. Then, PN-A process with total nitrogen removal of up to 81.5% was established due to the thriving of anammox bacteria Candidatus Kuenenia resulting from the reduction of the aeration rate. Molecular analysis showed that both bacterial and archaeal communities shifted greatly throughout the start-up stage and the PN-A stage. Besides bacterial genus Nitrosomonas, ammonium-oxidizing archaea (AOA) Candidatus Nitrososphaera with a high abundance of 3.44% also contributed to partial nitritation. Nitrospira was effectively restrained (abundance <1.6%) while methanogens co-existed with the aerobic and anaerobic nitrogen-conversion microorganisms. This study showed that IASBR configuration was efficient in starting up the PN-A process from return sludge, maintaining long-term efficient nitrogen removal and triggering the thrive of AOA.

Efficient treatment of dairy processing wastewater in a laboratory scale Intermittently Aerated Sequencing Batch Reactor (IASBR).

This Research Communication describes an investigation into the viability of an Intermittently Aerated Sequencing Batch Reactor (IASBR) for the treatment of dairy processing wastewater at laboratory-scale. A number of operational parameters have been varied and the effect has been monitored in order to determine optimal conditions for maximising removal efficiencies. These operational parameters include Hydraulic Retention Time (HRT), Solids Retention Time (SRT), aeration rate and cycle length. Real dairy processing wastewater and synthetic wastewater have been treated using three laboratory-scale IASBR units in a temperature controlled room. When the operational conditions were established, the units were seeded using sludge from a municipal wastewater treatment plant for the first experiment, and sludge from a dairy processing factory for the second and third experiment. In experiment three, the reactors were fed on real wastewater from the wastewater treatment plant at this dairy processing factory. These laboratory-scale systems will be used to demonstrate over time that the IASBR system is a consistent, viable option for treatment of dairy processing wastewater in this sector. In this study, the capacity of a biological system to remove both nitrogen and phosphorus within one reactor will be demonstrated. The initial operational parameters for a pilot-scale IASBR system will be derived from the results of the study.

Dominance of the genus Polaromonas in the microbial ecology of an Intermittently Aerated Sequencing Batch Reactor (IASBR) treating dairy processing wastewater under varying aeration rates.

In this Research Communication we investigate potential correlations between key bacterial groups and nutrient removal efficiency in an Intermittently Aerated Sequencing Batch Reactor (IASBR) treating synthetic dairy processing wastewater. Reactor aeration rates of 0·6 and 0·4 litre per minute (LPM) were applied to an 8 l laboratory scale system and the relative impacts on IASBR microbial community structure and orthophosphate (PO4-P) and ammonium (NH4-N) removal efficiencies compared. Aeration at 0·6 LPM over several sludge retention times (SRTs) resulted in approximately 92% removal efficiencies for both PO4-P and NH4-N. Biomass samples subjected to next-generation sequencing (NGS), 16S rRNA profiling revealed a concomitant enrichment of Polaromonas under 0·6 LPM conditions, up to ~50% relative abundance within the reactor biomass. The subsequent shift in reactor aeration to 0·4 LPM, over a period of 3 SRTs, resulted in markedly reduced nutrient removal efficiencies for PO4-P (50%) and NH4-N (45%). An 85·7% reduction in the genus level relative abundance of Polaromonas was observed under 0·4 LPM aeration conditions over the same period.

Efficient treatment of dairy processing wastewater in a pilot scale Intermittently Aerated Sequencing Batch Reactor (IASBR)

This Research Communication describes the initial operation of a pilot-scale intermittently aerated sequencing batch reactor system, which is located at an Irish dairy processing factory. Laboratory-scale research has facilitated the design specifications and operational parameters necessary for the construction and running of a pilot-scale. Laboratory scale research was necessary prior to the pilot scale system to ensure high quality treatment and nutrient removal efficiencies. The pilot system operates with a hydraulic retention time of 4 d, a solids retention time of 16 d and a cycle length of 12 hours. There are 4 non-aeration and aeration phases within the system's react phase. This system has a 3000 l working volume, treating 375 l of wastewater per cycle, 750 l daily. The system was seeded from an aeration tank at the dairy processing factory where the unit is located. The system is operating with the goal to remove both nitrogen and phosphorus from the wastewater biologically, reducing the need for chemical treatment. Currently, the system is performing with high efficiency, treating the wastewater to an acceptable level according to the Irish Environmental Protection Agency for discharge into surrounding water bodies. Therefore, the initial removal results demonstrate this technology's suitability for the treatment of high strength dairy wastewaters.

Performance of Denitrifying Phosphate Removal via Nitrite from Slaughterhouse Wastewater Treatment at Low Temperature

This study aims to investigate the effects of the organic loading rate (OLR) and the aeration rate on denitrifying phosphate removal (DPR) from slaughterhouse wastewater treated at a temperature of 11 °C. Three laboratory-scale intermittently aerated sequencing batch reactors (IASBRs) were set up and three OLRs and five aeration rates were employed in the study. The results indicated that efficient removals of nitrogen (N) and phosphorus (P) from DPR were achieved. Furthermore, the intermittent aeration pattern benefitted both the phosphorus-accumulating organisms (PAOs) and the denitrifying phosphorus-accumulating organisms (DPAOs) that accumulated at 11 °C. The ratio of P uptake in the aeration periods/P release in the non-aeration periods was in the range of 0.94–1.10 in the three stages. The relationship between the specific poly-β-hydroxybutyrate (PHB) degradation rate (z), the specific P removal rate (x), and the specific total oxidized nitrogen(TON) reduction rate (y) can be fitted approximately as a plane ( z = 1.3626 x + 0.2882 y − 0.6722 , R2 = 0.83).

Advantages of intermittently aerated SBR over conventional SBR on nitrogen removal for the treatment of digested piggery wastewater

An intermittently aerated sequencing batch reactor (IASBR) and a traditional sequencing batch reactor (SBR) were parallelly constructed to treat digested piggery wastewater, which was in high NH 4 + -N concentration but in a low COD/TN ratio. Their pollutant removal performance was compared under COD/TN ratios of 1.6–3.4 d and hydraulic retention times of 5–3 d. The results showed that the IASBR removed TN, NH 4 + -N and TOC more efficiently than the SBR. The average removal rates of TN, NH 4 + -N and TOC were 83.1%, 96.5%, and 89.0%, respectively, in the IASBR, significantly higher than the corresponding values of 74.8%, 82.0%, and 86.2% in the SBR. Mass balance of organic carbon revealed that the higher TN removal in the IASBR might be attributed to its efficient utilization of the organic carbon for denitrification, since that 48.7%–52.2% of COD was used for denitrification in the IASBR, higher than the corresponding proportion of 43.1%–47.4% in the SBR. A pre-anoxic process in the IASBR would enhance the ammonium oxidation while restrict the nitrite oxidation. Anoxic duration of 40–80 min should be beneficial for achieving stable nitritation.

Comparative study on microbial community in intermittently aerated sequencing batch reactors (SBR) and a traditional SBR treating digested piggery wastewater

A traditional sequencing batch reactor (SBR) and two intermittently aerated sequencing batch reactors (IASBRs) were parallelly operated for treating digested piggery wastewater. Their microbial communities were analyzed, and the nitrogen removal performance was compared during the long–term run. IASBRs demonstrated higher removal rates of total nitrogen (TN) and ammonium nitrogen (NH4 +-N) than the SBR, and also demonstrated higher resistance against TN shock load. It was found that the more switch times between aerobic/anoxic in an IASBR, the higher the removal rates of TN and NH4 +–N. All the reactors were predominated by Thauera, Nitrosomonas and Nitrobacter, which were considered to be species of denitrifiers, ammonium oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB), respectively. However, the abundance and diversity was of great difference. Compared with SBR, IASBRs achieved higher abundance of denitrification–related bacteria. IASBR 1# with four aerobic/anoxic switch times was detected with 25.63% of Thauera, higher than that in IASBR 2# with two aerobic/anoxic switch times (11.57% of Thauera), and much higher than that in the SBR (only 6.19%of Thauera). IASBR 2# had the highest percentage of AOB, while IASBR 1# had the lowest percentage. The denitrifiers abundance was significantly positive correlated with the TN removal rate. However, the NH4 +–N removal rate showed no significant correlation with the AOB abundance, but might relate to the AOB activity which was influenced by the average free ammonium (FA) concentration. Nitrobacter was the only NOB genus detectable in all reactors, and were less than 0.03%.

Removal of veterinary antibiotics from anaerobically digested swine wastewater using an intermittently aerated sequencing batch reactor

A lab-scale intermittently aerated sequencing batch reactor (IASBR) was applied to treat anaerobically digested swine wastewater (ADSW) to explore the removal characteristics of veterinary antibiotics. The removal rates of 11 veterinary antibiotics in the reactor were investigated under different chemical organic demand (COD) volumetric loadings, solid retention times (SRT) and ratios of COD to total nitrogen (TN) or COD/TN. Both sludge sorption and biodegradation were found to be the major contributors to the removal of veterinary antibiotics. Mass balance analysis revealed that greater than 60% of antibiotics in the influent were biodegraded in the IASBR, whereas averagely 24% were adsorbed by sludge under the condition that sludge sorption gradually reached its equilibrium. Results showed that the removal of antibiotics was greatly influenced by chemical oxygen demand (COD) volumetric loadings, which could achieve up to 85.1%±1.4% at 0.17±0.041kgCOD/m-3/day, while dropped to 75.9%±1.3% and 49.3%±12.1% when COD volumetric loading increased to 0.65±0.032 and 1.07±0.073kgCOD/m-3/day, respectively. Tetracyclines, the dominant antibiotics in ADSW, were removed by 87.9% in total at the lowest COD loading, of which 30.4% were contributed by sludge sorption and 57.5% by biodegradation, respectively. In contrast, sulfonamides were removed about 96.2%, almost by biodegradation. Long SRT seemed to have little obvious impact on antibiotics removal, while a shorter SRT of 30–40day could reduce the accumulated amount of antibiotics and the balanced antibiotics sorption capacity of sludge. Influent COD/TN ratio was found not a key impact factor for veterinary antibiotics removal in this work.

Simultaneous ammonium and nitrate removal by a modified intermittently aerated sequencing batch reactor (SBR) with multiple filling events

Abstract Optimized methods for simultaneous removal of nitrate, nitrite and ammonium are important features of nutrient removal. Nitrogen removal efficiency in an intermittently aerated sequencing batch reactor (IA-SBR) with multiple filling events was studied. No external carbon source was added and three filling events were considered. Oxidationreduction potential (ORP) and pH curve at solids retention time (SRT) of 20 d were analyzed. Effects of three organic loading rates (OLR), 0.67, 1.0 and 1.5 kgCOD/m3d, and three nitrogen loading rates (NLR), 0.054, 0.1 and 0.15 kgN/m3d, on nitrogen removal were studied. Nitrate Apex in pH curve and Nitrate Knee in ORP profile indicated that the end of denitrification would be achieved sooner. The kinetic coefficients of endogenous decay (kd) and yield (Y) were identified to evaluate heterotrophic specific denitrification rate (SDNRb). In period 2 at NLR of 0.054 kgN/m3d and considering 2 anoxic and 3 aerobic phases, nitrogen removal efficiency was 91.43%.

Effects of loading rate and aeration on nitrogen removal and N2O emissions in intermittently aerated sequencing batch reactors treating slaughterhouse wastewater at 11°C.

This study aimed to find optimal operation conditions for nitrogen removal from high strength slaughterhouse wastewater at 11°C using the intermittently aerated sequencing batch reactors (IASBRs) so as to provide an engineering control strategy for the IASBR technology. Two operational parameters were examined: (1) loading rates and (2) aeration rates. Both the two parameters affected variation of DO concentrations in the IASBR operation cycles. It was found that to achieve efficient nitrogen removal via partial nitrification-denitrification (PND), "DO elbow" point must appear at the end of the last aeration period. There was a correlation between the ammonium oxidizing bacteria (AOB)/nitrite oxidizing bacteria (NOB) ratio and the average DO concentrations in the last aeration periods; when the average DO concentrations in the last aeration periods were lower than 4.86mg/L, AOB became the dominant nitrifier population, which benefited nitrogen removal via PND. Both the nitrogen loading rate and the aeration rate influenced the population sizes of AOB and NOB. To accomplish efficient nitrogen removal via PND, the optimum aeration rate (A, Lair/min) applied can be predicted according to the average organic loading rates based on mathematical equations developed in this study. The research shows that the amount of N2O generation in the aeration period was reduced with increasing the aeration rate; however, the highest N2O generation in the non-aeration period was observed at the optimum aeration rates.

Characteristics of nitrous oxide (N2O) emission from intermittently aerated sequencing batch reactors (IASBRs) treating slaughterhouse wastewater at low temperature

This study investigated the characteristics of nitrous oxide (N2O) emission from intermittently aerated sequencing batch reactors (IASBRs) treating high strength slaughterhouse wastewater at 11°C, where partial nitrification followed by denitrification (PND) was achieved. N2O generation and emission was examined at three aeration rates of 0.4, 0.6, and 0.8Lair/min in three IASBRs (SBR1, SBR2, and SBR3, respectively). The slaughterhouse wastewater contained chemical oxygen demand (COD) of 6057±172.6mg/L, total nitrogen (TN) of 576±15.1mg/L, total phosphorus (TP) of 52±2.7mg/L and suspended solids (SS) of 1843±280.5g/L. In the pseudo-steady state, the amount of N2O emission was up to 5.7–11.0% of incoming TN. The aeration rate negatively affected N2O emission and the ratio of N2O emission to incoming TN was reduced by 48.2% when the aeration rate was increased from 0.4 to 0.8Lair/min. Results showed that more N2O was generated in non-aeration periods than in aeration periods. Lower DO concentrations enhanced N2O generation in the aeration periods (probably via nitrifier denitrification) while low DO concentrations (lower than 0.2mg/L) did not affect N2O generation in the non-aeration periods (probably via heterotrophic denitrification). When PHB was utilized as the organic substrate for denitrification, there was a high N2O generation potential. It was estimated that 1.8mgN2O-N was generated accompanying per mg PHB consumed.

Nitrogen removal from slaughterhouse wastewater through partial nitrification followed by denitrification in intermittently aerated sequencing batch reactors at 11°C

This study is aimed to examine the removal of nitrogen from high strength slaughterhouse wastewater at 11°C via partial nitrification followed by denitrification (PND), using the intermittently aerated sequencing batch reactor (IASBR) technology. The slaughterhouse wastewater contained chemical oxygen demand (COD) of 6068 mg/L, total nitrogen (TN) of 571 mg/L, total phosphorus (TP) of 51 mg/L and suspended solids of 1.8 g/L, on average. The laboratory-scale IASBR reactors had a working volume of 8 L and was operated at an average organic loading rate of 0.61 g COD/(L·d). At the cycle duration of 12 h, COD was efficiently removed under three aeration rates of 0.4, 0.6 and 0.8 L air/min. Among the three aeration rates, the optimum aeration rate was 0.6 L air/min with removals of COD, TN, and TP of 98%, 98%, and 96%, respectively. The treated wastewater met the Irish emission standards. The microbial community analysis by fluorescence in situ hybridization shows 12±0.4% of ammonium oxidizing bacteria, and 7.2±0.4% of nitrite oxidizing bacteria in the general bacteria (EUB) in the activated sludge at the aeration rate of 0.6 L air/min, leading to efficient partial nitrification. PND effectively removed nitrogen from slaughterhouse wastewater at 11°C, but PND efficiency was dependent on the aeration rate applied. PND efficiencies were up to 75.8%, 70.1% and only 25.4% at the aeration rates of 0.4, 0.6, and 0.8 L air/min.

Assessment of nitrogen and phosphorus removal in an intermittently aerated sequencing batch reactor (IASBR) and a sequencing batch reactor (SBR)

Biological nitrogen and phosphorus removal was investigated in an intermittently aerated sequencing batch reactor (IASBR) and a sequencing batch reactor (SBR). The removal efficiencies of ammonium-nitrogen (NH4(+)-N) were 100% in both reactors in steady operation state. The total nitrogen (TN) removal efficiencies were 90.4% in the IASBR and 79.3% in the SBR, while the total phosphorus (TP) removal efficiencies were 88.8% in the IASBR and 82.3% in the SBR. The efficiencies of simultaneous nitrification and denitrification (SND) were 90.4% in the IASBR and 79.3% in the SBR, indicating that the IASBR was more efficient than the SBR in SND. The sludge in the IASBR had a P release capability of 16.6 mg P/g VSS (volatile suspended solids) but only 7.5 mg P/g VSS in the SBR.

EFFECT OF AERATION RATE ON DOMESTIC WASTEWATER TREATMENT USING AN INTERMITTENTLY AERATED SEQUENCING BATCH REACTOR (IASBR) TECHNOLOGY

Effects of the aeration rate on nutrient removal from synthetic domestic wastewater using an intermittently aerated sequencing batch reactor (IASBR) were studied at ambient temperature. Two aeration rates, 0.8 and 1 L air/min, were studied. At the aeration rate of 0.8 L air/min, removals of COD, NH4+-N, total nitrogen (TN) and PO43--P were 84%, 96%, 75% and 99%, respectively. At the aeration rate of 1 L air/min, removals of COD, NH4+-N, TN and PO43--P were 90%, 99%, 70% and 66%, respectively. The increased DO concentrations resulted in improved nitrification, but interfered with denitrification and enhanced biological phosphorus removal (EBPR).

Characteristics of Nitrous Oxide (N2O) Emissions from Intermittently-Aerated Sequencing Batch Reactors Treating the Separated Liquid Fraction of Anaerobically Digested Pig Manure

In this study, the N2O emission from an intermittently aerated sequencing batch reactor (IASBR-1) treating the separated liquid fraction of anaerobically digested pig manure (SLAP) was investigated. The wastewater had chemical oxygen demand (COD) concentrations of 11,540 ± 860 mg l−1, 5-day biochemical oxygen demand (BOD5) concentrations of 2,900 ± 200 mg l−1and total nitrogen concentrations of 4,041 ± 59 mg l−1, with low COD:N ratios (2.9, on average) and BOD5:N ratios (0.72, on average). Synthetic wastewater, simulating the SLAP with similar COD and nitrogen concentrations but with higher BOD5 concentrations of up to 11,500 ± 100 mg l−1, was treated in another identical reactor (IASBR-2) to compare the effects of carbon source on nutrient removals and N2O emissions. In steady-state, soluble N2O accumulated in the non-aeration periods, with the highest N2O concentrations measured at the end of the non-aeration periods. There was a significant reduction in N2O concentrations during the aeration periods with reductions occurring immediately on commencement of aeration. The mean N2O emissions in an operational cycle were 253.6 and 205.3 mg for IASBR-1 and IASBR-2, respectively. During the non-aeration periods, only 8.3% and 8.4% of total N2O emissions occurred in IASBR-1 and IASBR-2, respectively; while during the aeration periods, 91.7% and 91.6% of N2O emissions took place in IASBR-1 and IASBR-2, respectively. The mean specific N2O generation rates were 0.010 and 0.005 mg (g VSS·min)−1 in the aeration periods, 0.024 and 0.021 mg (g VSS·min)−1 in the non-aeration periods for IASBR-1 and IABSR-2, respectively. Mean nitrogen removal via N2O emissions was 15.6% and 10.1% for IASBR-1 and IASBR-2, respectively. The IASBR-1 with low influent BOD5 concentrations emitted and generated more N2O.

Partial nitrification and nutrient removal in intermittently aerated sequencing batch reactors treating separated digestate liquid after anaerobic digestion of pig manure

The performance of an intermittently aerated sequencing batch reactor (IASBR) technology was investigated in achieving partial nitrification, organic matter removal and nitrogen removal from separated digestate liquid after anaerobic digestion of pig manure. The wastewater had chemical oxygen demand (COD) concentrations of 11,540±860mg/L, 5-day biochemical oxygen demand (BOD(5)) concentrations of 2,900±200mg/L and total nitrogen (TN) concentrations of 4,041±59mg/L, with low COD:N ratios (2.9) and BOD(5):COD ratios (0.25). Synthetic wastewater, simulating the separated digestate liquid with similar COD and nitrogen concentrations but BOD(5) of 11,500±100mg/L, was also treated using the IASBR technology. At a mean organic loading rate of 1.15kgCOD/(m(3)d) and a nitrogen loading rate of 0.38kgN/(m(3)d), the COD removal efficiency was 89.8% in the IASBR (IASBR-1) treating digestate liquid and 99% in the IASBR (IASBR-2) treating synthetic wastewater. The IASBR-1 effluent COD was mainly due to inert organic matter and can be further reduced to less than 40mg/L through coagulation. The partial nitrification efficiency of 71-79% was achieved in the two IASBRs and one cause for the stable long-term partial nitrification was the intermittent aeration strategy. Nitrogen removal efficiencies were 76.5 and 97% in IASBR-1 and IASBR-2, respectively. The high nitrogen removal efficiencies show that the IASBR technology is a promising technology for nitrogen removal from low COD:N ratio wastewaters. The nitrogen balance analysis shows that 59.4 and 74.3% of nitrogen removed was via heterotrophic denitrification in the non-aeration periods in IASBR-1 and IASBR-2, respectively.

Long-term partial nitrification in an intermittently aerated sequencing batch reactor (SBR) treating ammonium-rich wastewater under controlled oxygen-limited conditions

In this study, a novel technology was developed to achieve efficient partial nitrification at moderately low temperature, which would save the aeration cost and have the capacity to treat a wide range of ammonium-rich wastewaters with low chemical oxygen demand-to-nitrogen (COD:N) ratios. At pH of 7.1–7.4 and a sludge retention time (SRT) of greater than 100 days, a laboratory-scale intermittently aerated sequencing batch reactor (IA-SBR) was operated at about 20 °C to treat synthetic wastewater containing readily biodegradable COD of 100–300 mg L −1 and ammonium–nitrogen (NH 4 +–N) of 300 mg L −1. During the aeration periods, DO concentrations were controlled at less than 0.2 mg L −1, and the aeration was terminated when on-line NH 4 +–N measurement reached 20 mg L −1. During 180 days of operation, the mass ratio of nitrite–N (NO 2 −–N) to the total oxidized nitrogen was over 90% in the effluent. Molecular analyses show that ammonium oxidizing bacteria (AOB) represented up to 10% of the total bacterial population in the sludge biomass, and the ratio of AOB to nitrite oxidizing bacteria (NOB) was generally over 100. The IA-SBR quickly recovered after non-operation for 47 days. The three main factors enabling long-term stable partial nitrification in this study were: enrichment of AOB in the start-up period; controlled oxygen-limited conditions and the intermittent aeration strategy.