Intermittent Aeration Process Research Articles

Effects of Aeration Strategy on Denitrifying Performance of Activated Sludge Processes in Treating Low-Carbon-Source Municipal Wastewater

In this study, the effects of aeration strategy on nitrogen removal performance of activated sludge processes in treating low-carbon-source municipal wastewater were investigated. Two aeration strategies (continuous aeration (CA) and intermittent aeration (IA)) were evaluated, and the long-term performance of activated sludge processes employing these strategies in treating wastewater with C/N=3 were analyzed. The results demonstrated that the total nitrogen removal efficiency in CA was 17.92% higher than that in the IA process. Meanwhile, the carbon source utilized in nitrogen removal in CA was 44.29% higher compared with the IA process. Furthermore, the results of 16S rRNA sequencing showed that relative abundances of denitrifying bacteria in CA and IA were 5.86% and 2.06%, respectively, suggesting that the CA process has better denitrification ability when treating low-carbon-source wastewater. In addition, 16S rRNA sequencing gene prediction was utilized to analyze the in-depth mechanisms. The results demonstrated that genes involved in membrane transport, carbohydrate metabolism, and cell composition were more highly expressed in CA. The enhancement of metabolic activity under continuous aeration strengthened microbial carbon source utilization. Therefore, the activated sludge process under continuous aeration was more efficient in treating low-carbon-source municipal wastewater. This study provides ideas for low-carbon-source municipal wastewater treatment.

Research on in situ continuous off-line chemical cleaning in full-scale membrane bioreactors

An in situ continuous off-line chemical cleaning system for membrane bioreactors was developed, and a related engineering test was carried out. The cleaning method achieved the same effect as traditional off-line chemical cleaning of the MBR (membrane bioreactor) but reduced the cleaning time by 60%. There was a linear relationship between sodium hypochlorite/citric acid and pH. The proposed sodium hypochlorite soaking time was 15–24 h, and the citric acid soaking time was 8–20 h. An intermittent aeration process was used to blow sludge particles off of the surface of membrane to improve the cleaning efficiency when the aeration intensity was 25 Nm3/m2·h. This system and method did not affect the effluent production and had the same effect as traditional off-line chemical cleaning methods while saving space and reducing capital. This system was successfully used in a full-scale municipal wastewater treatment plant and is an important complement to traditional chemical cleaning of MBRs.

Application of real-time nitrogen measurement for intermittent aeration implementation in a biological nitrogen removal system: performances and efficiencies

ABSTRACTSeveral automatic strategies for aeration control have been investigated so far to favor a significant decrement of energy consumptions in biological processes in wastewater treatment plants (WWTPs). Above all, the intermittent aeration process has demonstrated to have several advantages. This work reports the results of a case study made in a small municipal WWTP where an intermittent aeration control strategy based on the online measurement of real-time nitrogen forms has been implemented to optimize the nitrogen removal and the energy consumption in an activated process. High organic removal efficiency was achieved during the whole experimental period. Results indicated that nitrogen removal efficiency has been improved, especially during winter months, by the control strategy adopted that helped to determine the perfect length for the nitrification and denitrification phases. The intermittent aeration process increased the activity of the biomass, further selecting phosphate-accumulating bacteria and improving the growth of bacteria able to internally store carbon source. Excellent effects were achieved on energy and chemical consumption, with a reduction of about 15% and 23%, respectively. Finally, a 12% reduction of sludge production was also detected.

Enhanced biological nitrogen removal and N2O emission characteristics of the intermittent aeration activated sludge process

Enhanced biological nitrogen removal processes are necessarily required to cope with more stringent wastewater discharging regulations, especially for wastewater with low level of organic carbon to nitrogen ratios. The intermittent aeration activated sludge process has been received comprehensive attention over the past decades, due to its excellent performance in nitrogen removal and remarkable reduction of energy consumption. Recent advances for this technology was reviewed from aspects of characteristics of system, factors affecting nitrogen removal, nitrous oxide (N2O) emission and its control, and application of the technology and its operation control. Finally, future development was proposed. In the intermittent aeration activated sludge process, aeration duration should be controlled for adequate nitrification and non-aeration duration should be adequate for complete denitrification, and these would benefit both nitrogen removal and N2O mitigation. The step feed strategy could be applied to enhance the better utilization of influent organic carbon for nitrogen removal. Dissolved oxygen (DO) and aerobic duration both affected nitrogen removal in particular that via nitrite in the intermittent aeration process. Nitrite should be removed efficiently to avoid a high N2O emission under both anoxic and aerobic conditions. Intermittent aeration activated sludge process has been applied in the treatment of various wastewaters, such as municipal wastewater, swine wastewater, anaerobic effluents and landfill leachate. For practical application, DO, pH and oxidation–reduction potential could be used as indices for controlling nitrogen removal and N2O mitigation. Microbial ecology in the intermittent aeration activated sludge process should be specifically focused in future studies.

Influence of aeration cycles on mechanical characteristics of elastomeric diffusers in biological intermittent processes: Accelerated tests in real environment

The paper deals with the evaluation of the effect of on/off switching of diffuser membranes, in the intermittent aeration process of the urban wastewater treatments. Accelerated tests were done using two types of commercial EPDM diffusers, which were submitted to several consecutive cycles up to the simulation of more than 8 years of real working conditions. The effect of this switching on the mechanical characteristics of the membranes was evaluated in terms of pressure increment of the air operating at different flow rates (2, 3.5 and 6 m3/h/diff): during accelerated tests, such increment ranged from 2% to 18%. The intermittent phases emphasized the loss both of the original mechanical proprieties of the diffusers and of the initial pore shapes. The main cause of pressure increment was attributed to the fouling of the internal channels of the pores. Further analyses performed by scanning electron microscopy and by mechanical tests on EPDM membrane, using a traditional tensile test and a non destructive optical method, from which the Young's Modulus was obtained, supported previous conclusions. Any changes in terms of oxygen transfer parameters (KLa and SOTE%) were specifically founded by causing to the repeated on/off switching.

Study and Analysis of the Impacts and Mechanisms of Intermittent Aeration and Movement Degree of Membrane on the Permeate Flux in a Submerged Membrane System

This task studies the impacts and mechanisms of intermittent aeration and movement degree of membrane on the permeate flux in a submerged membrane system. The contents includes: Analysis of the effects of intermittent aeration on the membrane performance, modelling the experimental results and find out the mechanisms; Analysis of the effects of different movement degree of membrane on the permeate flux during the intermittent aeration process, modelling the experimental results and find out the mechanisms; Determination of the optimum membrane running conditions, including the most effective intensity of gas sparging, the most effective intermittent aeration cycle time and the most effective movement degree of membrane, etc. It shows that intermittent aerations between backwashing processes can significantly improve the membrane performance; the change of the movement degree (L/H),which means the ratio of the effective length and the effective vertical height) of membrane can affect the influences of intermittent aeration on the membrane performance significantly; the most effective intensity of gas sparging is 1.5L/h; the most effective intermittent aeration cycle time is 30min; the most effective movement degree of membrane is 1.07.The result of the research is good for the selection of operation condition and determination of running parameters of ultrafiltration membrane water supply process.

Comparative studies on the differently operated trains of the North-Budapest Wastewater Treatment Plant

In order to reduce the pollution load of the Danube, the North-Budapest Wastewater Treatment Plant has been upgraded to enhanced nitrogen removal by establishing a new activated sludge treatment line and modifying the existing unit for nitrification and denitrification. As both the influent flow rate and the influent chemical oxygen demand (COD), biological oxygen demand (BOD(5)) and total suspended solids (TSS) concentration levels remained far below the design values, setting one fourth of the reactor volume out of operation in the Old Line, and operating the nitrification reactor of the New Line with part-time aeration proved to be possible. Analytical data as well as simulation studies supported the advantage of the intermittent-aeration process in efficient N-removal. However, the lengths of the aerated periods have to be increased with decreasing temperature, and thereby effluent total nitrogen (TN) concentration can increase due to decreasing denitrification efficiency. Potential occurrence of low-dissolved oxygen (DO) bulking should be hindered through applying an efficient anoxic selector system.

Fuzzy Control of an Intermittent Aeration Process for Nutrients Removal

Fuzzy Control of an Intermittent Aeration Process for Nutrients Removal

Simultaneous removal of organic matter and nitrogen from milking parlor wastewater by a magnetic activated sludge (MAS) process

The magnetic activated sludge (MAS) process is a modification of the conventional activated sludge process to improve the solid–liquid separation characteristics. It was developed to reduce the production of excess sludge and the time required for the conventional activated sludge process. In this study, actual milking parlor wastewater was treated with a MAS process and no sludge was removed. The effectiveness of continuous aeration and intermittent aeration in removing organic matter and nitrogen were compared. Both processes were highly efficient at removing chemical oxygen demand (COD) (averaged 91% removal) and ammonium nitrogen (NH4-N) (averaged 99% removal). In marked contrast to the continuous aeration process, the 30-min aeration/90-min non-aeration cycle of the intermittent aeration process rapidly reduced the nitrate nitrogen (NO3-N) concentration to near-zero. This result indicates that NO3-N was almost completely denitrified via nitrite nitrogen (NO2-N) to nitrogen gas. Removal of organic material and nitrogen can be considered to have occurred simultaneously in the single tank of the MAS process.

Optimization of Nitrogen Removal for Alternating Intermittent Aeration-Type Activated Sludge System: A New Process Modification

A new activated sludge process modification was proposed for intermittent aeration process to achieve more stable nitrogen removal performance. A single completely mixed reactor was divided into two compartments in series and operated in intermittent aeration mode by using activated sludge simulation model. The new configuration provided competetive advantage on nitrification as well as denitrification capacity, compared to the intermittently aerated system with a single reactor. In addition, the dissolved oxygen set-point control during air-on periods was found to be an important parameter in terms of nitrogen removal.

Activated Sludge Model No. 1 calibration for piggery wastewater treatment using respirometry

To optimise the intermittent aeration process for piggery wastewater, the Activated Sludge Model No. 1 needs to be calibrated and adapted to this specific effluent. By combining aerobic and anoxic respirometric tests, biodegradation kinetics of organic fractions in piggery wastewater could be studied. Modeling of the respirometric curves proved that the simplified hydrolysis model was sufficient for piggery wastewater treatment simulation. The hydrolysis constant (K(H)) and heterotrophic sludge yield (Y(H)) were determined at temperature and pH in the ranges 10-40 degrees C and 7-9, respectively. The constants were slightly influenced by the temperature but not significantly affected by the pH, with average values of 3 d(-1) for K(H) and 0.60 for Y(H). The anoxic respirometric tests revealed that the experimental ASM1 anoxic correction factor (eta(g)) was higher than one. This could be explained by the fact that the anoxic and the aerobic heterotrophic sludge yields were probably different. By fixing a value of 0.8 for eta(g), the anoxic sludge yield (Y(HD)) could be calculated at 0.53. A modified version of ASM1 for substrate biodegradation in piggery wastewater intermittent aeration process was proposed, including the separation between the anoxic and the aerobic sludge yields and a simplified hydrolysis kinetic.

Innovative technologies for wastewater treatment in coastal tourist areas

The selection of appropriate wastewater treatment technologies for coastal tourist areas is important in the sense that they have to meet stringent effluent limits in a simple and easy to operate flow scheme. This paper outlines different effluent standards implemented in sensitive coastal areas and briefly discusses the merit of a number of innovative technologies, namely the sequencing batch reactor, the intermittent aeration process, the moving bed reactor and the biofim-filter-sequencing batch reactor system, either as a batch or continuous flow process applicable in these areas.

Real-time control of an immobilized-cell reactor for wastewater treatment using ORP

The performance of an immobilized-cell reactor for simultaneous carbon–nitrogen removal in synthetic wastewater with an intermittent aeration (IA) process under real-time control of oxygen supply was investigated. The oxidation–reduction potential (ORP) was monitored during operation. The ORP–time profile showed distinctive turning points, which directly correlated with the changes in the system chemistry and biological activity. The reactor was conducted by cyclic fixed-time aeration–nonaeration operation at the beginning, followed by real-time control technology using ORP setpoint. A moving window along the slope of the ORP curve was employed to search for the nitrate breakpoint of the aeration cycle. Once the breakpoint was found, the reactor was aerated for a fixed period. The treatment process could effectively avoid the anoxic fermentation state under the real-time control. The cycle time was reduced around 30%. The duration of aeration period was found to be optimum at 3 h under the consideration of the removal efficiencies of COD and total nitrogen. The real-time control system not only exhibited a better nitrogen removal efficiency than the fixed-time control operation, but it also showed a stable effluent quality during the change of HRT from 3 to 8 h. Good operation stability was demonstrated even when a very high disturbance of the influent loading occurred.

AP—Animal Production Technology: Some Intermittent Aeration Kinetics from a Laboratory Study with Pig Slurry

A 0·75 kW aeration system with a venturi air injector was used in this study to examine the properties of the oxygen uptake rate and overall oxygen transfer coefficient in pig slurry. Data showed that both parameters varied with the intermittent aeration process. The oxygen uptake rate increased from 0·46 mgl−1 min−1to about 1·8 mg l−1min−1, while the overall oxygen transfer coefficient decreased from 0·5 min−1to about 0·3 min−1over a total number of 31 tests. The system had a tendency to run continuously since the off-run time decreased from 10 min at the beginning of the test to 3 min at the end of the test. This may imply that an intermittent aeration system, if controlled by dissolved oxygen concentration, might not be able to run intermittently due to increased consumption of oxygen by the manure. The aeration system tested achieved an aeration efficiency of 3·20 kg [O2] kWh−1in this study.

Nitrification/Denitrification in Intermittent Aeration Process for Swine Wastewater Treatment

A continuous-flow intermittent aeration (IA) process has been studied for nitrogen removal from anaerobically digested swine wastewater with high ammonium content. High nitrogen removal efficiency of average 91% total Kjeldahl nitrogen and 92% NH4-N was achieved in an IA system with an alteration of 1-h aeration and 1-h nonaeration. Nitrification and denitrification were found to be responsible for the nitrogen removal in the system. Nitrite and nitrate in the effluent were less than 1.0 mg/L and 8.0 mg/L, respectively. The specific nitrification and denitrification rates of the single-sludge IA culture were determined through batch experiments as 2.79–3.70 mgNO3-N/g volatile suspended solids-h and 0.59–1.03 mgNO3-N/g volatile suspended solids-h, respectively. In the IA process, the aeration period created favorable conditions for nitrifying bacteria (dissolved oxygen = 4–6 mg/L and oxidation-reduction potential = 80–100 mV), while the nonaeration period provided good environment for denitrifying bacteria...

Improvement of nitrogen-removal efficiency using immobilized microorganisms with oxidation-reduction potential monitoring

The use of an immobilized-cell reactor for simultaneous carbon–nitrogen removal in wastewater with the monitoring of oxidation–reduction potential (ORP) in an intermittent aeration (IA) process was investigated. Under alternating aerated and nonaerated conditions, the ORP-time profile showed distinctive turning points that directly correlated with changes in the system chemistry and biological activity. The aeration ratio, defined as aeration time/cycle time, was optimum at 50% for obtaining the maximum efficiency of denitrification accompanied by sufficient nitrification. High simultaneous carbon–nitrogen removal efficiency could be achieved using the immobilized-cell reactor by applying the IA process. More than 90% of COD-removal efficiency and over 80% of total-nitrogen-removal efficiency were obtained using three aerobic–anoxic cycles per day at an aeration ratio of 50% and with a hydraulic retention time of 10 h. Journal of Industrial Microbiology & Biotechnology (2000) 25, 229–234.

The Processing of Livestock Waste Through the Use of Activated Sludge - Treatment with Intermittent Aeration Process -

The Processing of Livestock Waste Through the Use of Activated Sludge - Treatment with Intermittent Aeration Process -

Application of ORP Control for Nitrogen Removal in Highly Concentrated Activated Sludge Process

A laboratory-scale experiment was carried out for fermentation wastewater treatment by intermittent aeration process using oxidation reduction potential (ORP) as a control parameter. A high concentration of activated sludge was retained in the reactor by ultrafiltration (UF) membrane during the experimental period. For simultaneous carbon and nitrogen removals, the lower and upper ORP limits should be −50 mV and +175 mV respectively. The lower total organic carbon (TOC) and total nitrogen (T-N) concentrations in the effluent was observed, which demonstrated that ORP control method was suitable for high strength fermentation wastewater treatment in a single bioreactor by intermittent aeration process.

Nitrification and denitrification in an intermittent aeration for nitrogen removal from swine wastewater

Nitrification and denitrification in an intermittent aeration for nitrogen removal from swine wastewaterNitrification and denitrification activities in an intermittent aeration (IA) process were investigated for nitrogen removal from anaerobically digested swine wastewater. Effluent from a mesophilic anaerobic digester treating raw swine wastewater was further treated continuously for nitrogen removal in a reactor with intermittent aeration. Efficiency of nitrogen removal in the continuous IA...Author(s)Bin LiuJiayang ChengSourceProceedings of the Water Environment FederationSubjectSession 19 - Research Symposium: Nitrogen RemovalDocument typeConference PaperPublisherWater Environment FederationPrint publication date Jan, 2000ISSN1938-6478SICI1938-6478(20000101)2000:13L.678;1-DOI10.2175/193864700784608126Volume / Issue2000 / 13Content sourceWEFTECFirst / last page(s)678 - 678Copyright2000Word count321

Controlling factors for simultaneous nitrification and denitrification in a two-stage intermittent aeration process treating domestic sewage

This bench-scale research investigated the controlling factors for simultaneous nitrification and denitrification (SND) in a 2-stage, intermittent aeration (IA) process, designed for nitrogen and phosphorus removal. The 2-stage process consisted of an anaerobic zone followed by an oxidation–reduction potential (ORP) controlled, intermittently aerated, completely mixed (IACM), tank. The three independent variables examined were the average ORP level, organic substrate (acetate and methanol) dosage and aeration cycle. The sewage used was completely of residential origin. Nitrogen balance clearly indicated that the nitrogen loss, due to SND in the aeration tank, contributed 10% to 50% of the influent TKN to the overall nitrogen removal. Significant differences in both nitrification and denitrification in the IACM tank were observed, when different average ORP levels were applied to the aeration control; this proved that absolute ORP can be used as a real-time control parameter for SND. Under low DO and intermittent aeration conditions, acetate and methanol additions improved nitrification over the entire dosage range and denitrification at relatively low dosages. Finally, a longer aeration cycle, with a zero-DO period, appeared to favor sequential nitrification and denitrification (SQND), not SND.