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Floccules are another major form of microbial aggregates in aerobic granular sludge systems. Previous studies mainly attributed the persistence of floccules to their relatively faster nutrient uptake and higher growth rate over aerobic granules; however, they failed to unravel the underlying mechanism of the long‐term coexistence of these two aggregates. In this work, the existence and function of the floccules in an aerobic granule‐dominated sequencing batch reactor were investigated from the view of quorum sensing (QS) and quorum quenching (QQ). The results showed that though the floccules were closely associated with the granules in terms of similar community structures (including the QS‐ and QQ‐related ones), they exhibited a relatively higher QQ‐related activity but a lower QS‐related activity. A compatible proportion of floccules might be helpful to maintain the QS‐related activity and keep the granules stable. In addition, the structure difference was demonstrated to diversify the QS‐ and QQ‐related activities of the floccules and the aerobic granules. These findings could broaden our understanding of the interactions between the coexistent floccules and granules in aerobic granule‐dominated systems and would be instructive for the development of the aerobic granular sludge process. [ABSTRACT FROM AUTHOR]

In this work, the performance of a sequencing batch reactor (SBR) was studied for treating sanitary wastewater of Yazd power plant, Iran. For this purpose, at the first, a pilot system was designed, installed, and started up. Then the effects of retention time, pH, temperature, influent chemical oxygen demand (COD) concentration, and air flow rate were investigated on the effluent concentration of COD. In SBR reactor used in the Yazd power plant, the microalga was not used for the wastewater treatment. In this case, the COD effluent output was, at the best conditions, approximately 92 mg/L. In the studied SBR system, we used the Chlorella vulgaris microalgae and microorganisms, simultaneously. In this case, the COD level reached 34 mg/L. An artificial neural network (ANN) was developed by applying Levenberg‐Marquardt training algorithm to predict the effluent concentration of COD. The optimum conditions were obtained at pH = 8, temperature of 30°C, influent COD concentration of 600 mg/L, and air flow rate of 50 L/min. ANN predicted results were in good agreement with the experimental data with a validation coefficient of determination (R2) and validation mean square error of 0.962 and 0.0015, respectively. [ABSTRACT FROM AUTHOR]

An anaerobic/aerobic sequencing batch reactor was used to test enhanced biological phosphorus removal (EBPR) in wastewater. In the present study, after 6 weeks of operation, the phosphorous and TOC removal efficiency reached to 97.8 and 97.5%, respectively. Our results suggest that phosphate‐accumulating organisms (PAOs) play a key role in the phosphorus removal in the EBPR system. Qualitative and quantitative measurements indicate the appear and changing trend of characteristic particles in activated sludge, which further illustrates the metabolic activity and mechanism of PAOs. Fluorescence in situ hybridization (FISH) images showed that PAOs gradually became the predominant bacteria in the EBPR system, aligning with the results of phosphorus removal rate. PCR‐DGGE profile demonstrated that with the operation of EBPR process, the composition of microorganisms became more and more abundant in the EBPR system over time. Further sequencing analysis indicated that these microbial populations belonged to α‐Proteobacteria, β‐Proteobacteria, γ‐proteobacteria, Rhodococcus sp. and Pseudomonas sp. [ABSTRACT FROM AUTHOR]

Abstract: BACKGROUND: The influence of pH, sludge retention time (SRT) and organic loading rate (OLR) were evaluated in the fermentation of cheese whey to produce volatile fatty acids (VFA) in a sequencing batch reactor (SBR). The reactor performance was studied at SRT of 4, 6 and 10 days and the influence of pH (5, 5.5 and 6) was determined at each SRT. The OLR effect was also studied in the range 3 to 12 g COD L‐1 d‐1, while keeping the other parameters mentioned above constant. RESULTS: A more acidic pH , improved the degree of acidification at short SRT (4 and 6 days), reaching 76 and 84%, respectively, meanwhile at pH 6 the degree of acidification (DA) improved and reached 85% at longer SRT (10 d). Regarding the VFA profile, a pH shift from 5 to 6 stimulated the production of acetic and propionic acids, whereas the production of butyric and valeric acids decreased irrespective of the SRT applied. Moreover, the increase of SRT from 4 to 10 d boosted propionic and valeric acids production regardless of the pH applied. Lower OLR favoured the production of propionic and valeric acids, while higher OLR increased the production of butyric acid. Lactose degradation and VFA production followed the Michaelis–Menten model. CONCLUSION: A selective VFA distribution can be reached by modifying parameters such as pH, SRT and OLR in acidogenic reactors, therefore, they could be suitable for further valorisation purposes in the production of polyhydroxyalkanoates from such VFA. © 2017 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

BACKGROUND Brewery wastewater is a potential feedstock for polyhydroxyalkanoates ( PHA) production since it contains high concentrations of easily biodegradable organic matter. Activated sludge was submitted to aerobic dynamic feeding conditions in a sequencing batch reactor fed fermented brewery wastewater in order to select a microbial culture with high storage capacity. The effect of several operational parameters, such as substrate concentration (57, 79 and 109 Cmmol L−1), pH (7 and 9 and without pH control (8-9)) and temperature (15 and 30 °C and without T control (15-28 °C)) was investigated. RESULTS The concentration of PHA stored by the activated sludge increased with the substrate concentration, with 39% PHA content on a dry biomass basis obtained at 109 Cmmol L−1. The storage yield increased from 0.35 to 0.43 Cmmol HA Cmmol−1 VFA when the substrate concentration was raised from 57 to 79 Cmmol L−1. However, a further increase in substrate concentration to 109 Cmmol L−1 led to a storage yield decrease to 0.39 Cmmol HA Cmmol−1 VFA. Control of pH and temperature did not enhance PHA storage. CONCLUSIONS Brewery wastewater is a good feedstock for production of PHAs using mixed cultures enriched under feast and famine conditions. PHA production can be enhanced by manipulating the operational conditions. © 2016 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

ABSTRACT Although the enrichment of specialized microbial cultures for the production of polyhydroxyalkanoates (PHA) is generally performed in sequencing batch reactors (SBRs), the required feast-famine conditions can also be established using two or more continuous stirred-tank reactors (CSTRs) in series with partial biomass recirculation. The use of CSTRs offers several advantages, but will result in distributed residence times and a less strict separation between feast and famine conditions. The aim of this study was to investigate the impact of the reactor configuration, and various process and biomass-specific parameters, on the enrichment of PHA-producing bacteria. A set of mathematical models was developed to predict the growth of Plasticicumulans acidivorans-as a model PHA producer-in competition with a non-storing heterotroph. A macroscopic model considering lumped biomass and an agent-based model considering individual cells were created to study the effect of residence time distribution and the resulting distributed bacterial states. The simulations showed that in the 2-stage CSTR system the selective pressure for PHA-producing bacteria is significantly lower than in the SBR, and strongly affected by the chosen feast-famine ratio. This is the result of substrate competition based on both the maximum specific substrate uptake rate and substrate affinity. Although the macroscopic model overestimates the selective pressure in the 2-stage CSTR system, it provides a quick and fairly good impression of the reactor performance and the impact of process and biomass-specific parameters. Biotechnol. Bioeng. 2015;112: 2475-2484. © 2015 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Aerobic granulation is a promising process for wastewater treatment, but this granulation process is very complicated and is affected by many factors. Thus, a mathematical model to quantitatively describe such a granulation process is highly desired. In this work, by taking into account all of key steps including biomass growth, increase in particle size and density, detachment, breakage and sedimentation, an one-dimensional mathematic model was developed to simulate the granulation process of activated sludge in a sequencing batch reactor (SBR). Discretization methodology was applied by dividing operational time, sedimentation process, size fractions and slices into discretized calculation elements. Model verification and prediction for aerobic granulation process were conducted under four different conditions. Four parameters indicative of granulation progression, including mean radius, biomass discharge ratio, total number, and bioparticle size distribution, were predicted well with the model. An optimum controlling strategy, automatically adjusted of settling time, was also proposed based on this model. Moreover, aerobic granules with a density higher than 120 g VSS/L and radius in a range of 0.4-1.0 mm were predicted to have both high settling velocity and substrate utilization rate, and the corresponding optimum operating conditions were be determined. Experimental results demonstrate that the developed model is appropriate for simulating the formation of aerobic granules in SBRs. These results are useful for designing and optimizing the cultivation and operation of aerobic granule process. Biotechnol. Bioeng. 2013; 110: 1312-1322. © 2012 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

BACKGROUND: The adaptation/selection of mixed microbial cultures under feast/famine conditions is an essential step for polyhydroxyalkanoates (PHA) production. This study investigated the short-term adaptation of a mixed microbial culture (activated sludge) during the start up of a sequencing batch reactor (SBR). RESULTS: Four different SBR runs were performed starting from different inocula and operated at the same organic load rate (8.5 gCOD L−1 d−1) and hydraulic retention time (1 day). At 3-7 days from SBR start up, the selected biomass was able to store PHA at comparable rate and yield with those obtained after long-term acclimation. Independently from the time passed, a short feast phase was the key parameter to obtain PHA storage at high rate and yield in the following accumulation stage (244 mgCOD g−1CODnonPolym h−1 for specific storage rate and 48% COD COD−1 as PHA content in the biomass). The DGGE profiles showed that the good storage performance and the structure of the microbial community were not fully correlated. CONCLUSIONS: The results suggest a new strategy for operating the PHA accumulation stage directly in the SBR, after very short biomass adaptation, instead of using two separate reactors for biomass enrichment and PHA accumulation, respectively. © 2012 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

BACKGROUND: This study is focused on the application of intensified biological systems for the degradation of halogenated organic compounds. The single and combined effects of cometabolism and bioaugmentation with Pseudomonas putida on the aerobic degradation of 4-chlorophenol (4-CP) in sequencing batch reactors was studied. Phenol was added as growth substrate to enhance 4-CP biodegradation through cometabolic transformation. RESULTS: Adaptation of activated sludge by increasing 4-CP loads aimed at a progressive acclimation to that compound, which could be successfully degraded at loading rates below 55 mg g−1 VSS d−1. Using phenol as cosusbtrate allowed almost a threefold decrease of the time required for the exhaustion of 4-CP. The addition of phenol also reduced the toxic effect of 4-CP over P. putida. The bioaugmentation of the SBR with P. putida enhanced the 4-CP removal rate, allowing the SBR to deal with 4-CP loads up to 120 mg g−1 VSS d−1. CONCLUSION: Bioaugmentation of SBR with P. putida improves the capacity of this system to withstand high toxic shocks. Cometabolic degradation of 4-CP with phenol improves the removal rates achieved by the SBR at similar 4-CP loads. Both strategies are more convenient intensification techniques than acclimation for the biological treatment of 4-CP. Copyright © 2012 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

The article discusses a study which investigated a novel integration process of a microbial fuel cell (MFC) into a sequencing batch reactor (SBR) to determine the energy production and the removal of the chemical oxygen demand (COD) for energy-saving wastewater treatment. It provides an overview of the use of activated sludge process for biological wastewater treatment. The development of membrane-less MFC is described using non-woven cloth. Also determined is the generation of electricity of the biocathode MFC.

The article presents a study on the nitrification of bacterial communities in an aquaculture wastewater treatment system using gene cloning, fluorescence in situ hybridization (FISH), and phylogenetic analysis. Nitrogenous compounds found in shrimp farms in Thailand can cause eutrophication and toxicity to other animals. The study used the molecular method in studying the nitrifying bacteria or ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) inoculated from shrimp farms using the sequencing batch reactor (SBR).