Optimisation of Aeration Efficiency: A Design Procedure for Secondary Treatment Using a Hybrid Aeration System

1989 ◽  
Vol 21 (10-11) ◽  
pp. 1403-1419 ◽  
Author(s):  
V. K. Thomas ◽  
B. Chambers ◽  
W. Dunn
Keyword(s):  
Plug Flow ◽  
Design Procedure ◽  
Aeration Tank ◽  
Surface Aeration ◽  
Aeration System ◽  
Fine Bubble ◽  
Oxygen Transfer Efficiency ◽  
Aeration Efficiency ◽  
Attractive Option ◽  
Activated Sludge Systems

The fine-bubble diffused air (FBDA) system of aeration is most efficiently operated in low rate activated sludge systems. The aeration technique is, however, subject to poor oxygen transfer efficiency and diffuser clogging under increased loading conditions such as are experienced close to the tank inlet in plug-flow systems. Mechanical, surface aeration systems, though apparently less efficient, do not suffer from these disadvantages. The ideal aeration tank configuration, for optimum aeration efficiency is therefore:–inlet anoxic zone–completely mixed surface aerated zone–plug-flow, fine-bubble diffused air zone with tapered aeration–clarification tanks. An overall aeration efficiency of 1.5-2.0 kg/kwh is predicted for nitrifying systems, together with an increased diffuser lifetime compared to a conventional FBDA tank. The design procedure is illustrated using parameters for a large UK works. Despite greater civil costs, the reduced running costs and NPC of the hybrid system make it an attractive option when compared to a plug-flow FBDA system or a conventional surface aeration plant.

Comparison of the efficiency of large-scale ceramic and membrane aeration systems with the dynamic off-gas method

2002 ◽  
Vol 46 (4-5) ◽  
pp. 317-324 ◽  
Author(s):  
J.A. Libra ◽  
A. Schuchardt ◽  
C. Sahlmann ◽  
J. Handschag ◽  
U. Wiesmann ◽  
...  
Keyword(s):  
Large Scale ◽  
Operating Conditions ◽  
Air Distribution ◽  
Energy Costs ◽  
Dissolved Oxygen Concentration ◽  
Membrane Aeration ◽  
Aeration System ◽  
Oxygen Transfer Efficiency ◽  
Aeration Efficiency ◽  
Period Measurement

The aeration systems of two full-scale activated sludge basins were compared over 2.5 years under the same operating conditions using dynamic off-gas testing. Only the material of the diffuser was different, membrane vs. ceramic tube diffusers. The experimental design took the complexity and dynamics of the system into consideration. The investigation has shown that, although the membrane diffusers have higher initial standard oxygen transfer efficiency (SOTE) and standard aeration efficiency (SAE), these decreased over time, while the SAE of the ceramic diffusers started lower, but increased slightly over the whole period. Measurement of air distribution in the basins along with dissolved oxygen concentration profiles have provided important information on improving process control and reducing energy costs. The results show that dynamic off-gas testing can effectively be used for monitoring the aeration system and to check design assumptions under operating conditions. The information can be used to improve the design of new aeration systems or in retro-fitting existing basins.

Evaluation of the Efficiency of a New Aeration System at Henriksdal Sewage Treatment Plant

1988 ◽  
Vol 20 (4-5) ◽  
pp. 85-92 ◽  
Author(s):  
L.-G. Reinius ◽  
J. Hultgren
Keyword(s):  
Air Flow ◽  
Sewage Treatment ◽  
Sewage Treatment Plant ◽  
Treatment Plant ◽  
Design Flow ◽  
The Other ◽  
Aeration Tank ◽  
Aeration System ◽  
Term Change ◽  
Fine Bubble

Henriksdal sewage treatment plant is the largest plant in Stockholm with a design flow of 370 000 m3/d. In one aeration tank of eleven a new fine-bubble aeration system has been in operation since August 1985. The tank is divided into 6 equal parts. The first part is an anoxic zone and the other five are aeration zones with tapered diffusers. Several instruments are installed in the block including separate air flow monitors in each of the five zones and D.O.-probes in the inlet and outlet of the zones. Equipment for flow measurement of settled sewage and return sludge is also installed. Every instrument is connected to a computer for data acquisition. To evaluate the efficiency of the aeration system the oxygenation transfer capacity has been calculated from the oxygen massbalance equation for each zone as a function of air flow. To solve this equation the respiration has to be known and this is done by a simple respirometer for samples of the MLSS in each zone. When the KLa-values are known as functions of the air flow the mass balance equation can be used to calculate the respiration rate in each zone. The computer has been logging data for 2 2 months, and it is possible to calculate the respiration rates in the different zones every hour during this period. It is very important to know the respiration along the tank and how it varies to get the optimal tapering of the diffusers when it is time to change the aeration system in the other 10 tanks. The calculations show a different pattern in the respiration over the year depending on the rate of nitrification. Another use of the calculation of the oxygenation transfer efficiency is to recognize if any long-term change occurs due to clogging of the diffusers.

scholarly journals The Changing and Distribution Laws of Oxygen Transfer Efficiency in the Full-Scale IFAS Process

Water ◽  
2021 ◽  
Vol 13 (14) ◽  
pp. 1933
Author(s):  
Xuyang Liu ◽  
Xuejun Bi ◽  
Qing Huang ◽  
Xiaodong Wang ◽  
Ruihuan Gu ◽  
...  
Keyword(s):  
Oxygen Transfer ◽  
Wastewater Treatment Plants ◽  
Plug Flow ◽  
Full Scale ◽  
Transfer Efficiency ◽  
Factors Affecting ◽  
Fine Bubble ◽  
Oxygen Transfer Efficiency ◽  
Distribution Laws ◽  
Two Sides

The integrated fixed-film activated sludge (IFAS) process has been widely used in the upgrading of wastewater treatment plants (WWTPs). The oxygen transfer efficiency (αOTE) is of great significance to the design and operation of the IFAS process. The carrier filling ratio (CFR) and aeration type are two critical factors affecting αOTE and standard oxygen transfer efficiency (αSOTE). However, the distribution and changing laws of αOTE and αSOTE in the full-scale IFAS process areunclear. To optimize the operation of a WWTP and to improve the αOTE of the aeration systems, several off-gas tests were conducted under different aeration types and different CFRs. The results show that for the aerobic tank investigated (the ratio of length and width was 8:1), the αOTE and the αSOTE of the middle of the aeration systems were higher than those of the other two sides. However, the reason for the low αOTE at the beginning and the end of the tank may be different. Coarse-bubble aeration systems had a lower αOTE and almost the same oxygenation capacity (αSOTE) as the fine-bubble aeration systems under constant CFR (43%). The average αSOTE (18.7–28.9%) of the hybrid aeration systems increased with increasing CFR (7.7–57.7%), and different locations exhibited different degrees of change. The results reveal the distribution and changing law of the αOTE of aeration systems in the IFAS process, and attention should be paid to the improvement of the OTE of the plug-flow IFAS process.

Applying fine bubble aeration to small aeration tanks

2001 ◽  
Vol 44 (2-3) ◽  
pp. 203-210 ◽  
Author(s):  
Ph. Duchène; ◽  
E. Cotteux ◽  
S. Capela
Keyword(s):  
Oxygen Transfer ◽  
Wastewater Treatment Plants ◽  
Open Channels ◽  
Aeration System ◽  
Fine Bubble ◽  
Aeration Efficiency ◽  
Practical Guidelines ◽  
High Investment ◽  
Cylindrical Tanks ◽  
Grid Layout

Because the aeration system in an activated sludge plant typically represents a large part of the total energy requirements, designers and operators need accurate oxygen transfer information to make the aeration system as energy efficient as possible. This paper presents clean water tests performed at 38 wastewater treatment plants. The Specific Aeration Efficiency results (SAE, kgO2/kWh) are reported for: (1) large open channels (volume higher than 1000 m3), (2) small open channels, (3) total floor coverage cylindrical tanks, and (4) cylindrical tanks with a grid arrangement. Some practical guidelines can be drawn, some of them being: (1) high SAE can be achieved at small aeration tanks (<1000m3), applying cylindrical tanks with a total floor coverage arrangement of diffusers, volumetric blowers, and moderate air flow rates per diffuser area; (2) the high investment cost of this configuration can be justified with respect to a grid layout characterized by spiral liquid circulation which affects the oxygen transfer; (3) small open channels can meet sufficient SAE values but fail to meet in this range of tank volumes those of total floor coverage cylindrical tanks.

Energy, cost and design aspects of coarse- and fine-bubble aeration systems in the MBBR IFAS process

2016 ◽  
Vol 75 (4) ◽  
pp. 890-897 ◽  
Author(s):  
S. Sander ◽  
J. Behnisch ◽  
M. Wagner
Keyword(s):  
Cost Effective ◽  
Biofilm Reactor ◽  
Moving Bed Biofilm Reactor ◽  
Filling Rate ◽  
Aeration System ◽  
Fine Bubble ◽  
Oxygen Transfer Efficiency ◽  
Fixed Film ◽  
Reactor Geometry ◽  
Cost Effective Alternative

With the MBBR IFAS (moving bed biofilm reactor integrated fixed-film activated sludge) process, the biomass required for biological wastewater treatment is either suspended or fixed on free-moving plastic carriers in the reactor. Coarse- or fine-bubble aeration systems are used in the MBBR IFAS process. In this study, the oxygen transfer efficiency (OTE) of a coarse-bubble aeration system was improved significantly by the addition of the investigated carriers, even in-process (∼1% per vol-% of added carrier material). In a fine-bubble aeration system, the carriers had little or no effect on OTE. The effect of carriers on OTE strongly depends on the properties of the aeration system, the volumetric filling rate of the carriers, the properties of the carrier media, and the reactor geometry. This study shows that the effect of carriers on OTE is less pronounced in-process compared to clean water conditions. When designing new carriers in order to improve their effect on OTE further, suppliers should take this into account. Although the energy efficiency and cost effectiveness of coarse-bubble aeration systems can be improved significantly by the addition of carriers, fine-bubble aeration systems remain the more efficient and cost-effective alternative for aeration when applying the investigated MBBR IFAS process.

Computational study on microscale behavior of bubble generated by aeration in a plug-flow aeration tank

2009 ◽  
Vol 59 (10) ◽  
pp. 2065-2072 ◽  
Author(s):  
Huanran Wang ◽  
Yanpeng Li ◽  
Zhixin Zhao
Keyword(s):  
Oxygen Transfer ◽  
Generation Time ◽  
Treatment Process ◽  
Plug Flow ◽  
Cross Flow ◽  
Aeration Tank ◽  
Governing Equations ◽  
Wastewater Treatment Process ◽  
Bubble Generation ◽  
Oxygen Transfer Efficiency

The microscale hydrodynamics of bubbles generated by aeration is directly related to the oxygen transfer efficiency and the overall performance of the activated sludge wastewater treatment process. To gain a deeper insight on the microscale phenomena of dispersed bubble occurring in this process, a three-dimensional direct simulation method is developed to study the effects of the liquid cross-flow on microscale behavior of bubble generation in a plug-flow aeration tank. The numerical simulations are performed using the level set method coupling with the governing equations of a single fluid with variable properties. The governing equations are solved using the finite-volume technique. The simulation results are validated through comparison with experimental observations. The study indicates that the liquid cross-flow has a strong impact on the bubble generation. Compared to that generated under quiescent liquid conditions, the bubble under liquid cross-flow conditions grows downstream along the tilted axis. The bubble generation time tends to decrease noticeably and the bubble at detachment has significantly smaller size. The bubble size and generation time also increase with the increase of gas velocity. The relation of such results to the oxygen transfer efficiency of the wastewater treatment process is also discussed.

Energy savings potential of new aeration system: Full scale trials

2012 ◽  
Vol 7 (4) ◽  
Author(s):  
A. Lazić ◽  
V. Larsson ◽  
Å. Nordenborg
Keyword(s):  
Control System ◽  
Energy Consumption ◽  
Total Energy ◽  
Energy Savings ◽  
Treatment Plant ◽  
Full Scale ◽  
Total Energy Consumption ◽  
Aeration System ◽  
Fine Bubble ◽  
Aeration Control

The objective of this work is to decrease energy consumption of the aeration system at a mid-size conventional wastewater treatment plant in the south of Sweden where aeration consumes 44% of the total energy consumption of the plant. By designing an energy optimised aeration system (with aeration grids, blowers, controlling valves) and then operating it with a new aeration control system (dissolved oxygen cascade control and most open valve logic) one can save energy. The concept has been tested in full scale by comparing two treatment lines: a reference line (consisting of old fine bubble tube diffusers, old lobe blowers, simple DO control) with a test line (consisting of new Sanitaire Silver Series Low Pressure fine bubble diffusers, a new screw blower and the Flygt aeration control system). Energy savings with the new aeration system measured as Aeration Efficiency was 65%. Furthermore, 13% of the total energy consumption of the whole plant, or 21 000 €/year, could be saved when the tested line was operated with the new aeration system.

Power Generation and Oxygen Transfer Analyses for Micro Hydro-Turbine Installed in Wastewater Treatment Aeration Tank

2021 ◽  
pp. 1-16
Author(s):  
Abdel Rahman Salem ◽  
Alaa Hasan ◽  
Ahmad Abdelhadi ◽  
Saif Al Hamad ◽  
Mohammad Qandil ◽  
...  
Keyword(s):  
Wastewater Treatment ◽  
Oxygen Transfer ◽  
Power Loss ◽  
Wastewater Treatment Plants ◽  
Aeration Tank ◽  
Hydro Turbine ◽  
Oxygen Transfer Efficiency ◽  
Aeration Process ◽  
The U.S ◽  
Water Height

Abstract This study targets one of the major energy consumers in the U.S. It suggests a new mechanical system that can recover a portion of the energy in Wastewater Treatment Plants (WWTPs). The proposed system entails a hydro-turbine installed above the air diffuser in the aeration tank to extract the water-bubble current's kinetic energy and converts it to electricity. Observing the optimum location of the turbine required multiple experiments where turbine height varies between 35% and 95% (water height percentages above the diffuser), while varying the airflow between 1.42 L/s (3 CFM) and 2.12 L/s (4.5 CFM) with a 0.24 L/s (0.5 CFM) increment. Additionally, three water heights of 38.1 cm (15”), 53.4 cm (21”), and 68.6 cm (27”) were considered to study the influence of the water height. It was noticed that the presence of the system has an adverse effect on the Standard Oxygen Transfer Efficiency (SOTE). Therefore, a small dual-blade propeller was installed right above the diffuser to directly mix the water in the bottom of the tank with the incoming air to enhance the SOTE. The results showed that the maximum reclaimed power was obtained where the hydro-turbine is installed at 65% - 80% above the diffuser. A reduction of up to 7.32% in SOTE was observed when the setup was placed inside the tank compared to the tank alone. The addition of the dual-blade propeller showed an increase in SOTE of 7.27% with a power loss of 6.21%, ensuring the aeration process was at its standards.

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