High Aeration Rate Research Articles

Nitrous oxide (N2O) emissions from a pilot-scale oxidation ditch under different COD/N ratios, aeration rates and two shock-load conditions

Nitrous oxide (N2O) generated from wastewater treatment plants (WWTPs) has drawn attention due to its high emission load and significant greenhouse effect. In the present study, N2O emissions from a pilot-scale Carrousel oxidation ditch under various chemical oxygen demand (COD) to nitrogen ratio (COD/N) and aeration rates were systematically investigated. The highest N2O emission factor was 0.142 ± 0.013%, at COD/N of 5 and aeration rate of 1.8 m3 h−1, which was much lower than the majority of previous studies. The results could be attributed to the high internal recycle ratio of the oxidation ditch process which lightened the burden of influent load to the system. The profiles of N2O emissions and dissolved N2O concentration along the channels showed a distinct spatial variation that N2O emissions primarily occurred in the aeration zones due to the air stripping effect. However, both the aeration and anoxic zones contributed to N2O generation due to autotrophic nitrification (AN), which was considered to be the main N2O generation process. In addition, two simulated shock-load conditions, ammonia overload shock and aeration failure shock, were carried out to explore the response of the biological nitrogen removal (BNR) system. The results indicated that both shock-loads lead to excessive N2O emissions, especially at higher aeration rates, which could be explained by the improved N2O generation by AN process during the shock-load period. This study offered new insights into the role of operational parameters to N2O emission and the alternative approach for N2O mitigation during both the steady-state operation and shock-load conditions in the oxidation ditch process.

The net energy ratio of microalgae biofuels production based on correlated cultivation parameters in flat plate photobioreactors

The net energy ratio (NER) of microalgae biofuels depends fundamentally on assumptions of operational energy demand and biomass yield. However, for the NER calculation, it has not previously been considered that these parameters are related. This study derives a correlation between these values from published experimental data on flat plate photobioreactors and uses it to calculate the NER. The found correlation is adapted to outdoor conditions, and the energy demand throughout the life cycle for cultivation and biogas production is added. Results show that an asymptotic correlation between the aeration rate and the photosynthetic efficiency hampers net energy output. Maximising the biomass output requires a disproportionately high aeration rate, and thus operational energy demand. Best NER is obtained at low aeration rates, however the biomethane yield at these rates cannot compensate for the total energy demand throughout the life cycle. A NER of 3.6 is calculated. Sensitivity analysis on further technological improvements, such as more efficient energy supply, reduces the NER to 1.8. A comparison of assumptions from seven previous life cycle analyses demonstrates that NER below one results from incomplete system boundaries, or unrelated parameters for operational energy demand and biomass yield. Our findings help to explain contradictory results in previous studies, and will improve the quality of future NER analyses.

ВЛИЯНИЕ ЗАГРЯЗНЕНИЙ СТОЧНЫХ ВОД НА БИОЦЕНОЗ АКТИВНОГО ИЛА

Wastewater from agro-industrial complexes is rich in organic components. Biological method is considered to be the most universal for their purification. It provides a high rate of biodegradation of pollution. But due to the high concentration of incoming pollutants, activated sludge microbiome can reduce its cleaning ability. High aeration rate is required for the effective decomposition of such compounds, since aerobic microorganisms predominate in the activated sludge. Under real conditions, the time for the oxidation of these substances by microbial communities is often insufficient. This imbalance between incoming organic matter and oxidized activated sludge microbiota leads to the growth of filamentous bacteria, which is one of the reasons of activated sludge swelling. The influence of high concentrations of pollutants in wastewater on a consortium of microorganisms of activated sludge was investigated to eliminate this negative factor. Physical and chemical composition of the wastewater was carried out according to standard methods. The composition of the activated sludge bacteriocenosis and pig intestine microbiome were determined by standard methods of inoculation in liquid and solid nutrient media. A correlation between the decrease in the concentration of pollutants and regeneration of activated sludge biocenosis has been established. A 59.8% decrease in the overall level of COD contamination of source effluents led to an increase in the number of flocculating microorganisms by 41.7%. Deep destruction of amine nitrogen (99%) and phosphorus (71.4%) was observed due to the activation of heterotrophic microorganisms.

Effects of carbon-based additives and ventilation rate on nitrogen loss and microbial community during chicken manure composting.

Aerobic composting is a sustainable method for chicken manure recycling, while its unsuitable porosity and carbon to nitrogen ratio (C/N) may result in high nitrogen loss and incomplete composting. With the aim to investigate the effects of carbon-based additives and two ventilation rates on chicken manure composting and microbial community, two series of treatments were set up for chicken manure composting, in order to investigate their effects on the biodegradation process, ammonia (NH3) emission, nitrogen loss, physiochemical properties and microbial community. The results showed that additives and ventilation rates set in the current study influenced the carbon dioxide (CO2) production from the 2nd week and also the physiochemical parameters during the entire process, while no inhibitory effect on the maturity were observed. With woody peat as additive, the NH3 emission amount and nitrogen loss rate were shown as 15.86 mg and 4.02%, less than those in other treatments, 31.08–80.13 mg and 24.26–34.24%, respectively. The high aeration rate increased the NH3 emission and nitrogen loss, which were varied when the additives were different. The terminal restriction fragment length polymorphism (T-RFLP) results showed that the additives and the ventilation rates changed the microbial community, while the prominent microbial clones belonged to the class of Bacilli and Clostridia (in the phylum of Firmicutes), and Alphaproteobacteria, Deltaproteobacteria and Gammaproteobacteria (in the phylum of Proteobacteria). Bacillus spp. was observed to be the most dominant bacteria in all the composting stages and treatments. It was concluded that woody peat could improve chicken manure composting more than other additives, especially on reducing nitrogen loss, meanwhile 0.18 L‧min-1‧kg-1 DM was suitable for various additives. Therefore, suitable additive and aeration rate could be used in practical application, which could significantly reduce nitrogen loss without influence on the compos maturity process.

Powdered ALLODUST/ALLOCHAR Augmented Single Batch Aerobic Reactor (SiBAR) for High Concentration Phosphorous Removal from Agricultural Wastewater

Phosphates enter the surface waters from agricultural sources has been regarded as an important cause of eutrophication. Excess of phosphate concentration can cause severe health problems such as kidney damage and osteoporosis. The adsorption is one of the most popular removal methods used for treating wastewaters containing agricultural nutrients. The challenge is the time that phosphorous concentration is very high in agricultural related industries and is higher than the adsorption capacity of the system. This research investigated the treatment of agricultural wastewater by developing and adding two novel media (ALLODUST, ALLOCHAR) to a Single Batch Aerobic Reactor (SiBAR). ALLODUST and ALLOCHAR consisted of allophanic soil mineral material sourced from either a Horotiu soil (Allophanic soil) or a Craigieburn soil (Allophanic Brown soil). Central Composite Design (CCD) and Response Surface Methodology (RSM) were hired to design the experiment and model the nature of the response surface of the novel media in the experimental design and to analyze the optimum operational conditions. The SiBAR design was optimized for three ranges of P contamination: 1-50 mg L-1 (low range); 51-175 (mid-range); and 176-300 (high range). The ALLODUST novel media demonstrated a higher P adsorption capacity compared to the ALLOCHAR media and Allophane compound itself. The ALLODUST adsorbent dosage of 3 g L-1 was the optimum: being able to remove 100% of P up to 50 mg L-1 in 30 minutes with the lowest aeration rate (1.5 L min-1) and remove 76% of P up to 300 mg L- 1 in 450 minutes with the highest aeration rate (7.5 L min-1).

Patterned Membrane in an Energy-Efficient Tilted Panel Filtration System for Fouling Control in Activated Sludge Filtration.

A membrane bioreactor enhances the overall biological performance of a conventional activated sludge system for wastewater treatment by producing high-quality effluent suitable for reuse. However, membrane fouling hinders the widespread application of membrane bioreactors by reducing the hydraulic performance, shortening membrane lifespan, and increasing the operational costs for membrane fouling management. This study assesses the combined effect of membrane surface corrugation and a tilted panel in enhancing the impact of air bubbling for membrane fouling control in activated sludge filtration, applicable for membrane bioreactors. The filterability performance of such a system was further tested under variable parameters: Filtration cycle, aeration rate, and intermittent aeration. Results show that a combination of surface corrugation and panel tilting enhances the impact of aeration and leads to 87% permeance increment. The results of the parametric study shows that the highest permeance was achieved under short filtration–relaxation cycle of 5 min, high aeration rate of 1.5 L/min, and short switching period of 2.5 min, to yield the permeances of 465 ± 18, 447 ± 2, and 369 ± 9 L/(m2h bar), respectively. The high permeances lead to higher operational flux that helps to lower the membrane area as well as energy consumption. Initial estimation of the fully aerated system yields the energy input of 0.152 kWh/m3, much lower than data from the full-scale references of <0.4 kWh/m3. Further energy savings and a lower system footprint can still be achieved by applying the two-sided panel with a switching system, which will be addressed in the future.

Effect of aeration rates on enzymatic activity and bacterial community succession during cattle manure composting

In order to explore changes in microbial enzyme activity and bacterial community, a 60-day composting experiment was conducted using cattle manure and straw under aeration rates of 0.45, 0.68, and 0.90 L min−1 kg−1 fresh weight. High aeration rate increased the cellulase, urease, alkaline and acid phosphatase activities, but decreased that of invertase and catalase. Cellulase, alkaline phosphatase and catalase were the main enzymes that affected the composting process. Microbial analysis showed that high aeration rate increased the uniformity of bacterial community in thermophilic phase, but decreased that in mature phase. Different aeration rate affected the bacterial community structure and further influenced the relationship between enzyme and functional bacteria. Regulating the temperature, moisture content and EC in specific phases to affect bacterial community succession could provide guidance for improving maturity of composting.

Investigation of antifouling properties of polypropylene/TiO2 nanocomposite membrane under different aeration rate in membrane bioreactor system

This paper presents the results of aeration rate effect on antifouling properties of polypropylene (PP)/TiO2 nanocomposite membrane in membrane bioreactor (MBR) system in order to oil refinery wastewater treatment. For this purpose, three levels of aeration rate with specific aeration demand per membrane area (SADm) of 0.5, 1, and 1.5 m3/m2h was used. According to the obtained results, PP nanocomposite membrane showed high hydrophilicity, porosity, and high flux compared to neat PP membrane. Also, either low or high aeration rate had a negative influence on permeability and antifouling properties of neat PP and nanocomposite membranes. The analysis of fouling mechanism for both membranes based on Hermia’s model revealed that the cake formation is dominant mechanism for lower aeration rate while by increasing aeration rate, all models couldn’t predict experimental data. Meanwhile, by increasing aeration rate, chemical oxygen demand (COD) removal for activated sludge and both membranes decreased and increased, respectively.

Effect of aeration rate on the anti-biofouling properties of cellulose acetate nanocomposite membranes in a membrane bioreactor system for the treatment of pharmaceutical wastewater

In this study, the effect of aeration rate in terms of specific aeration demand per membrane area (SADm) on the anti-biofouling properties of cellulose acetate (CA) nanocomposite membranes (CA/ND-NH2) in a membrane bioreactor system was investigated. The amount of EPS and soluble EPS under high aeration rate conditions was observed to be higher than under low aeration rate conditions. The results obtained showed that either lower or higher aeration rates had a negative impact on membrane permeability. The high aeration rate resulted in a severe breakage of sludge flocs, and promoted the release of soluble EPS from the microbial flocs to the bioreactor tank. By increasing the aeration rate, the COD removal increased and decreased respectively for the membranes and the activated sludge. It was finally concluded that higher anti-biofouling properties of neat CA and nanocomposite membranes were obtained under optimal aeration rate conditions (SADm = 1 m3 m−2 h−1).

Biofilm reactors as a promising method for vitamin K (menaquinone-7) production.

Menaquinone-7 (MK-7) is the most potent subtype of vitamin K with extraordinarily high half-life in the circulatory system. Therefore, MK-7 plays a critical role in promoting human wellbeing today. Studies on MK-7 every year show more and more magnificent benefits of it in preventing cardiovascular diseases and osteoporosis to battling cancer cells, Alzheimer's and Parkinson's diseases. Thus, it needs to be supplemented to daily diet for accumulative and long-term benefits. Chemical synthesis of MK-7 produces a significant cis-isomer form of it, which has no biological activity. Fortunately, due to its key role in electron transfer in bacteria, trans-MK-7 is biosynthesized by especially Gram-positive strains mainly Bacillus genus. Concordantly, MK-7 could be produced via solid or liquid state fermentation strategies. In either regime, when static fermentation is applied in the absence of agitation and aeration, operational issues arise such as heat and mass transfer inefficiencies. Thus, scaling up the process becomes a challenge. On the other hand, studies have indicated that biofilm and pellicle formation that occur in static fermentations are key characteristics for extracellular MK-7 secretion. Therefore, this review covers the most recent discoveries of the therapeutic properties of MK-7 and optimization attempts at increasing its biosynthesis in different media compositions and effective growth parameters as well as the cutting-edge use of biofilm reactors where B. subtilis cells have the infrastructures to form mature biofilm formations on plastic composite supports. Biofilm reactors therefore can provide robust extracellular MK-7 secretion while simultaneously enduring high agitation and aeration rates, which then address the scale-up and operational issues associated with static fermentation strategies.

Biological drying of municipal solid waste from landfill

The aim of this work was to investigate the process of biodrying of municipal solid waste from the old landfill to preparing it for pyrolysis or gasification. New aspect of this research is biodrying of waste from old landfill. Biodrying of wastes was carried out at different aeration rates (7, 35, and 175 dm3/kg dry matter/d) at two temperatures (23 and 50 °C). The research was carried out in the laboratory bioreactors of special design (lysimeters), which simulated the conditions prevailing in the landfill. The optimal conditions for reduction of moisture in waste (63.2%) has been attained for the highest aeration rate (175 dm3/kg dry matter/d) and temperature equal to 50 °C. The final moisture content of the obtained biodried product was 23% w/w. In the bioreactor, in which the greatest reduction of moisture was obtained, the total amount of produced CO2 was 44.9 gC/kg dry matter, and the biodrying efficiency was equal to 0.89. During biodrying of wastes in optimal conditions, higher heating value of waste increased from 4.3 to 11.0 MJ/kg. As a result of the performed pyrolysis of biodried waste at 900 °C, char, oil, and gas were obtained the respective yields of 47, 32, and 21% w/w. The gas emerging in the gasification process was characterized by higher heating value equal to 11.3 MJ/m3.

Influence of aeration rate and reactor shape on the composting of poultry manure and sawdust

ABSTRACTTo achieve successful composting, all the biological, chemical, and physical characteristics need to be considered. The investigation of our study was based on various physicochemical properties, i.e., temperature, ammonia concentration, carbon dioxide concentration, pH, electrical conductivity (EC), carbon/nitrogen (C/N) ratio, organic matter (OM) content, moisture content, bacterial population, and seed germination index (GI), during the composting of poultry manure and sawdust for different aeration rates and reactor shapes. Three cylindrical-shaped and three rectangular-shaped pilot-scale 60-L composting reactors were used in this study, with aeration rates of 0.3 (low), 0.6 (medium), and 0.9 (high) L min−1 kg−1 DM (dry matter). All parameters were monitored over 21 days of composting. Results showed that the low aeration rate (0.3 L min−1 kg−1 DM) corresponded to a higher and longer thermophilic phase than did the high aeration rate (0.9 L min−1 kg−1 DM). Ammonia and carbon dioxide volatilization were directly related to the temperature profile of the substrate, with significant differences between the low and high aeration rates during weeks 2 and 3 of composting but no significant difference observed during week 1. At the end of our study, the final values of pH, EC, moisture content, C/N ratio, and organic matter in all compost reactors were lower than those at the start. The growth rates of mesophilic and thermophilic bacteria were directly correlated with mesophilic and thermophilic conditions of the compost. The final GI of the cylindrical reactor with an airflow rate of 0.3 L min−1 kg−1 DM was 82.3%, whereas the GIs of the other compost reactors were below 80%. In this study, compost of a cylindrical reactor with a low aeration rate (0.3 L min−1 kg−1 DM) was more stable and mature than the other reactors.Implications: The poultry industry is growing in South Korea, but there are problems associated with the management of poultry manure, and composting is one solution that could be valuable for crops and forage if managed properly. For high-quality composting, the aeration rate in different reactor shapes must be considered. The objective of this study was to investigate various physicochemical properties with different aeration rates and rector shapes. Results showed that aeration rate of 0.3 L min−1 kg−1 DM in a cylindrical reactor provides better condition for maturation of compost.

Immobilization of Glucose Oxidase on Eupergit C: Impact of Aeration, Kinetic and Operational Stability Studies of Free and Immobilized Enzyme

The effect of aeration on the stability of glucose oxidase in the reaction of glucose oxidation to gluconic acid was investigated by determining the operational stability decay rate constant in the process conditions. Eupergit C as a porous carrier was chosen for the enzyme immobilization. To evaluate glucose oxidase operational stability during process conditions, experiments of glucose oxidation were carried out in the repetitive batch reactor with and without continuous aeration at different aeration levels. It was found that the decay rate of the free enzyme linearly depended on the air flow rate. Immobilization of glucose oxidase on Eupergit C significantly enhanced enzyme stability at higher aeration rates. Kinetics of the free and immobilized enzyme was also determined. The mathematical model of glucose oxidation catalysed by free and immobilized glucose oxidase in the batch reactor was developed.

Enhanced photocatalytic inactivation of E. coli by natural pyrite in presence of citrate and EDTA as effective chelating agents: Experimental evaluation and kinetic and ANN models

The effect of chelating agents (citrate and EDTA) on the visible light photocatalytic activity of natural pyrite for the inactivation of Escherichia coli ATCC 25922 (E. coli) was investigated. The influence of various parameters, such as chelating agent and H2O2 concentration, light intensity and aeration rate, was evaluated experimentally and through kinetic models. The presence of a chelating agent enhanced the photocatalytic activity of natural pyrite, and citrate was more effective than EDTA, considerably improving bacteria inactivation in natural pH and reducing the drawbacks of the photocatalytic inactivation system. For both citrate-pyrite and EDTA-pyrite, the inactivation rate went through a maximum for a concentration of the chelating agent of 0.5 mM. The increase of the light intensity (10–60 mW cm−2), H2O2 concentration (10–25 mg L-1) and aeration rate (2-8 L min-1) improved the radical generation, resulting in a high inactivation effect. The low effect of H2O2 on the catalytic activity of pyrite in the presence of EDTA was likely due to the inhibition of the hydrogen peroxide-to-hydroxyl radical conversion by EDTA. On the other hand, degradation of citrate at high aeration rate occurred, decreasing the catalytic activity of the citrate-pyrite system. Scavenging tests indicated that the bulk hydroxyl radicals are the most reactive radical species in the bacterial inactivation, closely followed by valence band holes, while conduction band electrons play a less important role. In addition, in order to generate predictions and to better understand the process, artificial neural networks were used as models for the considered process: the obtained performance indexes indicated a good correlation between experimental and predicted values.

Investigating composting progress of kitchen wastes using rate of change and cross-correlation approaches

Kitchen wastes usually require addition of some bulking agent for proper composting. In this study, mixtures of kitchen and pruning of elm trees were composted under three treatments of natural, low and high aeration rates. Temperature, ammonia, carbon monoxide, pH and volatile organic matter were monitored and analysed. The results indicated with increase in aeration rate, temperature of the treatments increased. The pH values of the treatments decreased initially to a minimum of 5.0 and then increased continuously. The emitted ammonia and CO initially rose but then continually decreased. The rate of change graphs showed two distinct phases of: 1) active; 2) constant rate for all measured factors. A correlation analysis on the five considered factors indicated the reduction in volatile organic matter and emitted CO and ammonia were highly negatively correlated with pH of the pile (r = −0.72), but their correlations with temperature were low.

Influence of Sparger Type and Regime of Fluid on Biomass and Lipid Productivity of Chlorella vulgaris Culture in a Pilot Airlift Photobioreactor

The effect of different types of spargers and the influence of the air flow rate on biomass and lipids production by Chlorella vulgaris was evaluated. These data allowed correlation of the hydrodynamic behavior of the photobioreactor with the byproducts production. The hydrodynamic characterization was developed by determining the mixing time (tM), hold-up, and total volumetric mass transfer coefficient of CO2, kLa(CO2)T, at increasing air flow rates for three different spargers: star-shaped, cross-shaped and porous glass surface sparger. The hydrodynamic characterization showed that the tM decreased, while the hold-up values and the kLa(CO2)T increased as a result of the increment in the volumetric air flow rate between 5 to 17 L min–1. The highest biomass and lipid concentrations were determined at the higher aeration rate (20 L min–1), which was correlated with the lower tM, the higher hold-up and kLa(CO2)T values. Biomass and lipid production showed an inverse correlation. The highest biomass concentration (750 mg L–1) and the lowest lipid concentration (10 mg L–1) were measured with the star sparger. In contrast, when the lowest biomass concentration was obtained (240 mg L–1), the highest lipid concentration of 196 mg L–1 was measured with the glass sparger. The maximum biomass productivity values were determined at the lower aeration rate and the star sparger, with the minimum power per unit of volume, which could be useful for a cost-effective process.

Efficacy analysis of a field scale IFAS reactor under different aeration strategies applied at high aeration rates: A statistical comparative analysis for practical feasibility

In the present research study, a field-scale integrated fixed-film activated sludge reactor treating municipal wastewater was examined under three cyclic aeration on/off periods (also known as intermittent aeration), applied at a aeration rate of 110 m3/h (capable to maintain bulk dissolved oxygen in the range of 4.5–5.0 mg/L). The whole experimental campaign was divided into four operational phases (continuous aeration followed by three aeration on/off cycles, expressed in terms of ratio of aeration on/off time, Period I: 150/30 min, Period II: 120/60 min, Period III: 90/60 min). Each experimental run was studied at a hydraulic retention time of 11.1 h and mixed liquor suspended solids concentrations as 2 ± 0.2 g/L. The treatment performance results showed that high rate assisted in achieving the desired performance under applied intermittent aeration conditions. Except nitrogen removal, other performance parameters such as chemical oxygen demand, biological oxygen demand, total suspended solids, ammonia nitrogen, and phosphorus were found to be least affected by on/off control applied in Period I and could cope up with Indian discharge standards. Whereas, Period II and III were not found to be appropriate with respect to desired performance. With respect to nutrient parameters, nitrogen and phosphorus removal rates were significantly deteriorated with increasing aeration off times. A statistical comparison of different operational phases, using analysis of variance and Turkey Post Hoc test, was also done to check the similarity/dissimilarity of applied strategies. The results revealed that period I and continuous aeration phase were quite similar in terms of all performance parameters.

Influence of operations on leachate characteristics in the Aerobic-Anaerobic Landfill Method

Landfill aeration is an effective technique for the controlled and sustainable conversion of conventional anaerobic landfills into a biologically stabilized state associated with a significantly lowered or the near elimination of the landfill gas emission potential. For in-situ leachate treatment recycling back the generated leachate in the bioreactor is also a promising technique for reducing pollutants and cost of ex-situ treatment as well. This research has been conducted to ascertain the in-situ treatment of leachate in Aerobic Anaerobic Landfill Method (AALM) compared with aerobic landfill and evaluated the impacts of various leachate recirculation regimes on MSW degradation and to provide data for successful operation in landfill sites. The experiment was conducted using six Plexiglass® landfill simulation reactors with a height of 100 cm and a diameter of 15 cm. Air was injected at the rates of 1.6 l/kg DM/h (Low aeration rate) for reactors R-LA, R-LAA (recirculatory) and LAA (non-recirculatory) and 4.8 l/kg DM/h (High aeration rate) in R-HA, R-HAA (recirculatory), and HAA (non-recirculatory) until day 242. It has been evaluated that R-HAA at high aeration rate achieved higher leachate quantity reduction (36.9%) than low aeration rate reactor R-LAA (19.6%) and AALM provides a better solution to control the temperature within the landfill body. The final NH4+-N concentration in R-HA (214.5 mg/l) was eight times lower than in the R-LA (1741.0 mg/l) reactor, and R-HAA (842.5 mg/l) was about three times lower than R-LAA (2315.4 mg/l) reactor on day 242. The change in leachate recirculation amount at varying moisture content positively affected the stabilization process and in-situ leachate treatment efficiency. The combination of both technologies (intermittent aeration and leachate recirculation) is a feasible way for in-situ leachate treatment, decrease the cost of further ex-situ leachate treatment as well as a viable and cost-saving alternative to continuous aeration.

Simultaneous nitrification, denitrification and phosphorus removal in an aerobic granular sludge sequencing batch reactor with high dissolved oxygen: Effects of carbon to nitrogen ratios

Simultaneous nitrification, denitrification and phosphorus removal (SNDPR) using aerobic granules is a promising approach in water treatment. The present work investigated the effects of influent carbon to nitrogen (N) ratios (20, 10, and 4) on the SNDPR performance in aerobic granular sequencing batch reactors (AGSBR) under high aeration rate. Results revealed that granules remained long-term stability when the DO concentration was 7–8 mg/L. With the decline of COD/N ratios, the denitrification efficiency was reduced due to the accumulation of nitrate, although the removal of COD and TP remained stable with good efficiency. Rising concentration of ammonia N led to the increase of PN/PS ratio of EPS as well as the protein types according to the results of 3D-EEM fluorescence spectroscopy. MiSeq pyrosequencing technology indicated that the decreasing ratio of COD/N under high DO concentration contributed to accumulation of GAOs and DNPAOs rather than PAOs.

Asymmetric Blade Disc Turbine for High Aeration Rate in a Fermenter

Asymmetric Blade Disc Turbine for High Aeration Rate in a Fermenter