Conventional Sequencing Batch Reactor Research Articles

Comparison of an anaerobic feed and split anaerobic–aerobic feed on granular sludge development, performance and ecology

The retrofitting of existing wastewater sequencing batch reactors (SBRs) to select for rapid-settling aerobic granular sludge (AGS) over floc-based conventional activated sludge (CAS), could be a viable option to decrease reactor cycle time and increase hydraulic capacity. Successful CAS-to-AGS conversion has previously been shown to be highly dependent on having a dedicated anaerobic feed, which presents additional engineering challenges when retrofitting SBRs. In this study we compared the performance of a split anaerobic–aerobic (An–Aer) feed with that of a traditional dedicated anaerobic feed regarding AGS formation and stability, nitrogen removal performance and microbial ecology. Using pilot trials, we showed that AGS could be established and maintained when using a split An–Aer feed at low organic loading rates analogous to that of a parallel full-scale conventional SBR. Additionally, we showed that AGS start-up time and nitrogen removal performance were comparable under a split An–Aer feed and dedicated anaerobic feed. Microbial ecology characterisations based on whole-of-community 16S rRNA profiles and targeted analysis of functional genes specific for nitrifying and denitrifying microorganisms, showed that the two different feed strategies had only subtle impacts on both the overall community composition and functional ecology. A much greater divergence in microbial ecology was seen when comparing AGS with CAS. Data presented here will be of value to those planning to retrofit existing CAS-based SBRs to operate with AGS and demonstrates the viability of using a more cost-effective split An–Aer feed configuration over a dedicated anaerobic feed.

Study the effect of recycled pressurized air on oxygen transfer design parameters in sequencing batch reactor technology

AbstractAeration process consumes more than 60% of the total energy required for wastewater treatment. The present study aims to save power consumption within wastewater treatment aeration process through recycling of the air flow. A new technique of aeration is used to increase oxygen transfer efficiency via exploiting recycled pressurized air. A pilot plant has been constructed to study the effect of using recycled pressurized air within sequencing batch reactor (SBR) model. The results showed that the new technique comparing with the conventional SBR model improved Standard oxygen transfer rate (SORT), Standard oxygen transfer efficiency (SOTE) and Standard aeration efficiency (SAE). In particular, the new technique enhanced (SAE) with 10 and 4% at gauge pressure values 0.5 atm. and 2 atm. respectively. On the other hand, intermittent aeration enhanced (SAE) with 15 and 5% at gauge pressure values 0.5 atm. and 2 atm. respectively.

Performance of integrated anaerobic/aerobic sequencing batch reactor treating poultry slaughterhouse wastewater

The present study investigates the performance of a new configuration laboratory-scale bioreactor comprising of two regimes (anaerobic & aerobic) in one reactor with physical separation and it is known as integrated anaerobic/aerobic sequencing batch reactor (IAASBR). The IAASBR is designed for treating high-strength wastewater such as poultry slaughterhouse wastewater (PSW) along with the simultaneous removal of organic carbon and ammoniacal nitrogen (NH3-N). The IAASBR exhibits that the average removal efficiency of total COD (TCOD), soluble COD (SCOD), NH3-N, fat, oil & grease (FOG), and total suspended solids (TSS) were (97%±2%), (95%±3%), (98%±1.3%), (90%±11%), and (96%±3%) respectively. The laboratory comparison test revealed that IAASBR configuration has enhanced the sludge settle-ability for aerobic SBR more than the conventional SBR or settling tank. Furthermore, IAASBR could tolerate the shock loading occurrence, handle organic loading rate (OLR) up to 4.5kg(TCOD)m−3d−1 and produce a high-quality effluent complying with Malaysian standards of industrial’s effluents.

Comparative study of emerging micropollutants removal by aerobic activated sludge of large laboratory-scale membrane bioreactors and sequencing batch reactors under low-temperature conditions

Four emerging micropollutants ibuprofen, diclofenac, estrone (E1) and 17α-ethinylestradiol (EE2) were studied in large laboratory-scale wastewater treatment plants (WWTPs) with high nitrifying activity. Activated sludge (AS) with sludge retention times (SRTs) of 12days and 14days in sequencing batch reactors (SBRs) and 30days, 60days and 90days in membrane bioreactors (MBRs) were examined at 8°C and 12°C. Concentrations of pharmaceuticals and their main metabolites were analysed in liquid phase and solid phase of AS by liquid chromatography–tandem mass spectrometry (LC–MS/MS). A remarkable amount of contaminants were detected in solids of AS, meaning the accumulation of micropollutants in bacterial cells. The biodegradation rate constants (Kbiol) were affected by SRT and temperature. MBR with a 90-day SRT showed the best results of removal. Conventional SBR process was inefficient at 8°C showing Kbiol values lower than 0.5lgSS−1d−1 for studied micropollutants.

Time-Domain Shooting and Bouncing Rays Method Based on Beam Tracing Technique

An efficient time-domain shooting and bouncing ray (TD-SBR) method is developed to analyze the transient scattering responses from large perfectly conducting objects illuminated by a pulsed plane wave. Differing from the conventional TD-SBR method, a beam tracing (BT) technique, instead of the ray tracing (RT), is first employed in the TD-SBR method, which provides much simpler procedure to avoid the divergence problem in the conventional SBR that happens when ray tubes intersecting discontinuous parts of the object. Applying a strategy of equivalent incident reference plane, alternative closed-form formulas are derived in the transient electromagnetic (EM) computations. Based on the closed-form representations, the characteristics of transition function and scattered fields are further investigated to show the physical phenomenon of scattering mechanisms. Due to the causality of transient fields, the proposed formulas are more efficient in EM calculations than the conventional frequency-domain formulas. Numerical examples illustrate that the BT technique can greatly improve the accuracy of the TD-SBR method, and the computational efficiency is enhanced significantly by using the direct TD formulas.

Specific oxygen uptake rate gradient – Another possible cause of excess sludge reduction in oxic-settling-anaerobic (OSA) process

Oxic-settling-anaerobic process (OSA) has established that anaerobic followed by aerobic process in a cyclic reaction reduces the biological sludge growth. However, the mechanism behind the process of reduction is still undefined. The recirculation of aerobic sludge from a sequencing batch reactor (SBR) to an anaerobic side reactor at the rate of 3.8–9.8gVSSrecycled/gVSS resulted in sludge reduction from 3% to 51% (Average=14.6–39.8%) in comparison to absence of OSA process in conventional SBR. The observed sludge reduction was in proportion to specific oxygen uptake rate (SOUR) gradient between sludge recycle and no recycle condition. The SOUR gradient is the ratio of its difference between fasting when sludge came out of anaerobic reactor and feasting conditions during aeration, in comparison to SOUR difference between aeration and termination of settling in the absence of any sludge recycle. SOUR kept on increasing with increasing sludge recycle during feasting (in aeration) in comparison to fasting (in anaerobic). This gradient resulted from high substrate oxidation during aeration (feasting), which may be induced by increased energy uptake stimulated by prolonged fasting. Increased cell maintenance also validated the effect of SOUR gradient in direct proportion.

Improving oxygen dissolution and distribution in a bioreactor with enhanced simultaneous COD and nitrogen removal by simply introducing micro-pressure and swirl.

Increasingly, environmental regulations are demanding more exacting chemical oxygen demand (COD) and nitrogen removal from wastewater, which come at a high economic cost. A very simple novel bioreactor, the micro-pressure swirl reactor (MPSR), can improve the dissolution and distribution of oxygen by the introduced micro-pressure swirl. Comparison with a conventional sequencing batch reactor (SBR) over 76 days of operation showed that this method can enhance simultaneous COD and nitrogen removal. By installing an aeration diffuser on one side of the two-dimensional MPSR, a swirl formed in the bioreactor that extended the retention time of the air bubbles. This unique flow regime, combined with the micro-pressure caused by the elevated water surface at the bubble outflow point, resulted in a higher level of dissolved oxygen (DO) in the MPSR. Aerobic and anaerobic zones that created appropriate conditions for simultaneous COD and nitrogen removal also formed in the MPSR. As the organic loading rate increased from 0.29 to 1.68 g COD/(L · day) over the test period, the COD removal efficiencies of the MPSR were generally 10-20 % greater than those of the SBR. In particular, the total nitrogen (TN) removal efficiencies of the MPSR and SBR were 40-50 and 20-35 %, respectively, whereas the TN concentrations in the MPSR effluent were always around 10 mg/L lower than those of the SBR. Further, because of the unique DO distribution, the bacterial species in the MPSR were more diverse and contributed to enhanced TN removal.

Effect of a Humus Soil Side-Stream Reactor (HSR) on the Bacterial Characteristics in Enhanced Biological Phosphorus Removal Process

Three enhanced phosphorus removal processes, each with a sequencing batch reactor (SBR), one with a humus soil side-stream reactor, one with an anaerobic side-stream reactor, and one without a side stream reactor (used as a conventional SBR process), designated as HS-SBR, A-SBR, and C-SBR, respectively, were operated and compared for the treatment of municipal sewage in laboratory scale. Compared with the total phosphorus (TP) removal efficiency of 68.3% obtained in the C-SBR, the TP removal efficiency in the A-SBR was only 53.2%, while in the HS-SBR, it increased to 85.6%. This observation suggested that the anaerobic side-stream reactor repressed TP removal in the system, while the humus soil side-stream reactor improved the TP removal. The detailed biochemical microbial analysis showed that the anaerobic side-stream reactor inhibited the TP removal activity through the repression of the polyphosphate kinase activity in the A-SBR, while the humus soil side-stream reactor improved the TP removal through improving the growth of polyphosphate-accumulating organisms and the activity of polyphosphate kinase, and inhibiting the growth of glycogen accumulating organisms in the HS-SBR. It was further speculated that humus soil in the humus soil side-stream reactor influenced the metabolism of PAOs and GAOs in the SBR.

Application of a New Type of Dispersed Particles-Stabilized Biomass in Aerobic Sequencing Batch Reactor (SBR) for Treating Starchy Wastewater

In this study, we present the advance in the performance of a sequencing batch reactor (SBR) by adding rubber particles to grow a new type of dispersed particles-stabilized biomass. The moving beds were tiny particles of casting rubber with density of 1.15 ± 0.03 g · cm−3. A conventional SBR was used as control, to compare the results between moving-bed SBR (MB-SBR) and SBR, hence received no moving bed. It was found that MB-SBR had acceptable resistance against the phenomena that caused rapid changes in settlement properties in comparison with SBR. The results showed that by decreasing the hydraulic retention time, the performance of MB-SBR was not influenced considerably in comparison with SBR. The performance of MB-SBR was approximately 26% and 88% higher than that of SBR for influent chemical oxygen demand of 1000 and 2000 mg · L−1, respectively. Improved resistant against organic loading shocks was observed in MB-SBR.

Cycle-time determination and process control of sequencing batch membrane bioreactors

In this paper a method to determine the cycle time for sequencing batch membrane bioreactors (SBMBRs) is introduced. One of the advantages of SBMBRs is the simplicity of adapting them to varying wastewater composition. The benefit of this flexibility can only be fully utilised if the cycle times are optimised for the specific inlet load conditions. This requires either proactive and ongoing operator adjustment or active predictive instrument-based control. Determination of the cycle times for conventional sequencing batch reactor (SBR) plants is usually based on experience. Due to the higher mixed liquor suspended solids concentrations in SBMBRs and the limited experience with their application, a new approach to calculate the cycle time had to be developed. Based on results from a semi-technical pilot plant, the paper presents an approach for calculating the cycle time in relation to the influent concentration according to the Activated Sludge Model No. 1 and the German HSG (Hochschulgruppe) Approach. The approach presented in this paper considers the increased solid contents in the reactor and the resultant shortened reaction times. This allows for an exact calculation of the nitrification and denitrification cycles with a tolerance of only a few minutes. Ultimately the same approach can be used for a predictive control strategy and for conventional SBR plants.

Low Acetate Concentrations Favor Polyphosphate-Accumulating Organisms over Glycogen-Accumulating Organisms in Enhanced Biological Phosphorus Removal from Wastewater

Glycogen-accumulating organisms (GAOs) are thought to compete with polyphosphate-accumulating organisms (PAOs) in enhanced biological phosphorus removal (EBPR) wastewater treatment systems. A laboratory sequencing batch reactor (SBR) was operated for one year to test the hypothesis that PAOs have a competitive advantage at low acetate concentrations, with a focus on low pH conditions previously shown to favor GAOs. PAOs dominated the system under conventional SBR operation with rapid acetate addition (producing high in-reactor concentrations) and pH values of 7.4-8.4. GAOs dominated when the pH was decreased (6.4-7.0). Decreasing the acetate addition rate led to very low reactor acetate concentrations, and PAOs recovered, supporting the study hypothesis. When the acetate feed rate was increased, EBPR failed again. Dominant PAOs and GAOs were Candidatus Accumulibacter phosphatis and Defluviicoccus Cluster 2, respectively, according to fluorescent in situ hybridization and 454 pyrosequencing. Surprisingly, GAOs were not the immediate causes of PAO failures, based on functional and population measurements. Pyrosequencing results suggested Dechloromonas and Tetrasphaera spp. may have also been PAOs, and additional potential GAOs were also identified. Full-scale systems typically have lower in-reactor acetate concentrations than laboratory SBRs, and so, previous laboratory studies may have overestimated the practical importance of GAOs as causes of EBPR failure.

Study on SBR Filled with Humus Soil for Domestic Sewage Treatment

The treatment efficiency of domestic sewage by the SBR filled with humus soil was investigated and compared with that by the conventional SBR. The results show that the removal rates of organic matters, NH4+-N and TP by the SBR filled with humus soil reach 85%, 83% and 72% respectively. Compared with the conventional SBR, the degradation rate of organic matters is improved, and the addition of humus soil contributes to occurrence of SND, thus the removal rate of NH4+-N is increased. The addition of humus soil shortens the oxidation time of organic matters and the nitrification time of NH4+-N, which can improve the treatment efficiency and reduce the operation cost.

Effect of sludge retention time and phosphorus to carbon ratio on biological phosphorus removal in HS-SBR process

Sludge retention time (SRT) and phosphorus to carbon ratio (P/C) in the feed are important control parameters in biological phosphorus removal. In this study, humus soil sequencing batch reactor (HS-SBR) process was operated with different SRTs (five, 10 and 15 days) and P/C feeding (0.0125 and 0.1) to evaluate their phosphorus removal efficiencies. The HS-SBR was composed of a humus soil reactor (HSR) and a conventional SBR (designated as hsSBR to differentiate from the conventional SBR used as a control). The results showed that the phosphorus removal efficiency was 82.7%, 97.3% and 97.3% at SRTs of five, 10 and 15 days respectively and acetate utilization efficiency for phosphorus release with SRTs of 10 and 15 days was much higher than that with an SRT of five days. In addition, a high P/C feeding (0.1) could promote the growth of the phosphate accumulating organisms in the hsSBR; however, the efficiency of phosphorus removal was lower than a low P/C feeding (0.0125) at an SRT of 15 days. All these observations suggested that a relatively long SRT and low P/C feeding exert a useful effect on the phosphorus removal in the hsSBR.

Effect of Aeration on Nitrous Oxide (N2O) Emission from Nitrogen-Removing Sequencing Batch Reactors

In this study, nitrous oxide (N(2)O) emission was compared between the operations of two different sequencing batch reactors, conventional sequencing batch reactor (CNVSBR) and simultaneous nitrification and denitrification sequencing batch reactor (SND-SBR), using synthetic wastewater. The CNV-SBR consisted of anoxic (denitrification) and aerobic phases, whereas the SND-SBR consisted of a microaerobic (low dissolved oxygen concentration) phase, which was achieved by intermittent aeration for simultaneous nitrification and denitrification. The CNV-SBR emitted 3.9 mg of N(2)O-N in the denitrification phase and 1.6 mg of N2O-N in the nitrification phase, resulting in a total emission of 5.5 mg from 432 mg of NH(4)(+)-N input. In contrast, the SND-SBR emitted 26.2 mg of N(2)O-N under the microaerobic condition, which was about 5 times higher than the emission obtained with the CNV-SBR at the same NH(4)(+)-N input. From the N(2)O yield based on NH(4)(+)-N input, the microaerobic condition produced the highest yield (6.1%), followed by the anoxic (0.9%) and aerobic (0.4%) conditions. It is thought that an appropriate dissolved oxygen level is critical for reducing N(2)O emission during nitrification and denitrification at wastewater treatment plants.

Research on Removal Effects of Pollutants by the (A/O)<sub>4</sub> SBR Process

The staged SBR is the process that divides aeration and sedimentation process of conventional SBR into several stages in time, and operates under the conditions of different stages of anaerobic/oxic/anoxic alternation. The experiment mainly discussed the five-stage SBR with useful volume of 12 L for nitrogen and phosphorous removal of synthetic municipal wastewater in the temperature ranges of 15~30°C. Tests revealed that under the condition of hydraulic retention time (HRT) is 8 hours and sludge retention time (SRT) is 15 day, the removal efficiency of COD, NH3-N, TN and TP can reach to 88.9%, 99.61%, 78.9% and 94.21%. The quality of effluent water is good, and don’t need to add Carbon Source through the experiment.

Phosphorus removal and simultaneous sludge reduction in humus soil sequencing batch reactor treating domestic wastewater

The potential for enhanced biological phosphorus removal (EBPR) and simultaneous sludge reduction in humus soil sequencing batch reactor (HS-SBR) was investigated. The HS-SBR was composed of a humus soil reactor (HSR) and a conventional SBR (designated as hsSBR to differentiate from the conventional SBR used as a control). The observed sludge yield in the HS-SBR process was estimated to be 0.18mg MLVSS (mixed liquor volatile suspended solid)/mg SCOD (soluble chemical oxygen demand), which represented a 24% reduction of solids production compared to a conventional SBR (cSBR) process. Meanwhile, the phosphorus removal in the HS-SBR remains unchanged compared with that in the cSBR. Intensive monitoring of SBR performance showed that polyhydroxy-alkanoates synthesis in the hsSBR was lower than in the cSBR. FISH analysis showed that the percentage of polyphosphate accumulating organisms (PAOs) in the hsSBR was much higher than that in the cSBR. These observations revealed the mechanism of phosphorus removal and simultaneous sludge reduction in the HS-SBR process. The role played by HSR in this process, especially on the reduction of glycogen-accumulating organisms (GAOs), was also explored and discussed.

Comparison of the Performance of Membrane and Conventional Sequencing Batch Reactors Degrading 4-Chlorophenol

The biomass characteristics, the process performance, and the microbial community for a sequencing batch reactor (SBR) and a submerged membrane SBR (MSBR) were evaluated. A synthetic wastewater containing only 4-chlorophenol (4CP) was used as the sole source of carbon and energy. Degradation efficiencies of 4CP were higher than 99% for both reactors, and no significant differences on the 4CP degradation rates were observed for the SBR (116.9 ± 0.9 mg 4CP g VSS−1 h−1) as well as for the MSBR (117.3 ± 0.5 mg 4CP g VSS−1 h−1). Despite the similar results obtained for the physicochemical parameters, it was found that the biomass characteristics were different considering the sludge volumetric index, settling velocity, protein content in the mixer liquor, and total suspended solids in the effluent. The settling velocity was three times higher in the SBR than in the MSBR; however, a better quality, considering suspended solids, was observed for the MSBR. The protein concentration in the mixed liquor was higher in the MSBR than in the SBR, generating foaming problems in the MSBR. A similarity analysis was made with the Ochiai–Barkman index. Even though the reactors were inoculated with the same biomass, significant differences in the composition and populations dynamics were observed.

Partial nitrification of sludge reject water using suspended and granular biomass

AbstractBACKGROUND: Partial nitrification–Anammox is a combined promising advanced biological process for the removal of nitrogen from wastewater, which allows important savings in energy consumption, sludge production, and organic carbon. Granular biomass appears to be an interesting alternative to conventional activated sludge, mainly because of its better settling properties. This study deals with the experimental results of a comparison between a conventional and a granular sequencing batch reactor (SBR) for the partial nitrification of reject water.RESULTS: After some days of operation, 30 days in the conventional SBR (system A) and 100 days in the granular SBR (system B), partial nitrification was achieved. Granular sludge showed much better settling properties than suspended biomass, with values of sludge volumetric index (SVI10) of 130 mL g−1 in system A and 38 mL g−1 in system B. Consequently, the solids concentration within the granular reactor was three times higher than for the conventional system while the concentration of solids in the effluent was 10 times higher in the conventional SBR. Morphology, microstructure and microbial populations in both systems were also studied.CONCLUSION: A partial nitrification process was successfully achieved in both systems, obtaining an effluent with a NO2−‐N/NH4+‐N ratio near 1, suitable for a following Anammox process. Granular biomass, mostly formed by round particles, showed better settling properties, leading to better sludge–effluent separation as well as higher biomass retention in the reactor. The granulation process does not affect bacterial populations, since they were the same in both systems. Copyright © 2011 Society of Chemical Industry

Effects of the cometabolite/growth substrate ratio on the aerobic degradation of 4-monochlorophenol

Chlorinated phenolic compounds like 4-monochlorophenol (4CP) are characterized by high toxicity even at relatively low concentrations and by strong persistency in both water and soils. Since cometabolism was proved to enhance 4CP biological removal, a conventional Sequencing Batch Reactor (SBR) was used in this study for the cometabolic aerobic degradation of 4CP at different influent concentrations and volumetric organic loading rates (40-50 mg/L and 0.129-0.323 kgCOD-4CP/m3·d, respectively), with sodium acetate (NaAc) as the growth substrate. The effects of different 4CP/NaAc ratios on SBR performances were evaluated in terms of 4CP removal efficiencies and maximum specific removal rates in order to maximize reactor performances: a decrease in NaAc dosage as external growth substrate would lead to definitely lower operating costs. A positive correlation was observed between 4CP maximum specific removal rates and the applied 4CP/NaAc ratios, thus making further reduction in NaAc dosage possible.

Aerobic granule formation in a sequencing batch reactor treating newsprint effluent under low phosphate conditions

Pulp and paper mills are under increasing pressure to minimize the discharge of phosphate to receiving waters. We investigated the operation of two laboratory sequencing batch reactors (SBR) under low phosphate conditions over a period of eight months. Performance characteristics in terms of COD and TSS removal were similar to the full-scale mill activated sludge operation, but the floc density and structure was improved. Sludge yield as a result of phosphate limitation was routinely lower than 0.15 kg/kg of COD. Aerobic granule formation was established in one of the SBRs by reducing the settling time from 30 min to 2 min and by increasing stirring shear force. Once established, the brown granules which were 1-2 mm in diameter were stable over five months of operation. Extracellular polymeric substance (EPS) analysis of the granules indicated a higher galactose content and lower mannose content than in conventional flocs. The granules generated more quorum sensing compound (acyl homoserine lactone) than conventional flocs, suggesting that quorum sensing could play a role in granule formation. When compared to the conventional SBR, the aerobic granule SBR performed at a higher organic loading, at faster settling velocity, and without filamentous bulking.