Optimization of oxygen transfer in clean water by fine bubble diffused air system and separate mixing in aeration ditches

1998 ◽  
Vol 38 (3) ◽  
Keyword(s):  
Oxygen Transfer ◽  
Clean Water ◽  
Fine Bubble ◽  
Air System

Surface active agents and their influence on oxygen transfer

1996 ◽  
Vol 34 (3-4) ◽  
pp. 249-256 ◽  
Author(s):  
Martin Wagner ◽  
H. Johannes Pöpel
Keyword(s):  
Surface Tension ◽  
Oxygen Transfer ◽  
Pure Water ◽  
Interfacial Area ◽  
Clean Water ◽  
Transfer Rates ◽  
Surface Active Agents ◽  
Fine Bubble ◽  
Different Types ◽  
New Guidelines

Oxygen transfer rates of fine bubble aeration systems in uniform arrangement are reduced down to 40% to 70% in wastewater compared to clean water conditions. Surfactants in wastewater are the main reason for the inferior and therefore uneconomic performance. The influence of different types of surfactants (anionic and nonionic) and of their concentration on oxygen transfer is investigated at various properties of pure water (content of electrolytes, hardness) by means of extensive experiments. The main results of the investigations are:in dependence of the type of surfactant, its concentration and the types of water:– the aeration coefficient kLa decreases (down to 55%)– the specific interfacial area (a) increases (up to 350%)– the oxygen transfer coefficient (kL) decreases (down to 20%)nonionic surfactants reduce the oxygen transfer more strongly than anionic surfactantsat the same surface tension, but different types of surfactant α-values can vary over a range of 0.12. Therefore α-values can not be calculated from surface tension measurementsα-values of approximately 0.55 should be taken for designing fine bubble aeration systemsIn new guidelines for the measurement of oxygen transfer rates, addition of 5 gm−3 of an arbitrary surfactant into clean water to simulate wastewater conditions must be abandoned.

Transfer number in fine bubble diffused aeration systems

2001 ◽  
Vol 43 (11) ◽  
pp. 145-152 ◽  
Author(s):  
S. Capela ◽  
M. Roustan ◽  
A. Héduit
Keyword(s):  
Oxygen Transfer ◽  
Full Scale ◽  
Clean Water ◽  
Transfer Number ◽  
Efficiency Criterion ◽  
Liquid Circulation ◽  
Fine Bubble ◽  
Nonsteady State ◽  
The Impact ◽  
Transfer Numbers

On the basis of full-scale data from 58 clean water tests performed in 26 activated sludge tanks equipped with fine bubble diffusers and of a theoretical approach, it can be stated that fine bubble aeration systems with total floor coverage arrangement provide higher kLa values and the lowest spiral liquid circulation. An efficiency criterion for oxygen transfer ( NT) was defined on the basis of the dimensional analysis. The transfer number NT allows us to take account of the impact of vertical liquid circulation movements on oxygen transfer. The values of NT calculated from the results of full scale nonsteady-state clean water tests vary from 5.3×10-5 to 9.1×10-5 and are directly dependent upon the arrangement of air diffusers. It has been shown that the highest transfer numbers corresponded to the total floor coverage arrangement and the average calculated NT values is 7.7×10-5, independently of the diffuser density and of the gas velocity, over the ranges studied. The lowest transfer numbers are obtained when the diffusers are located in separate grids, and the transfer number is reduced with increasing air flow rate.

scholarly journals Three decades of oxygen transfer tests in clean water in a pilot scale test tank with fine-bubble diffusers and the resulting conclusions for WWTP operation

2020 ◽  
Vol 15 (4) ◽  
pp. 910-920
Author(s):  
J. Behnisch ◽  
M. Schwarz ◽  
M. Wagner
Keyword(s):  
Oxygen Transfer ◽  
Cost Benefit Analysis ◽  
Cost Benefit ◽  
Pilot Scale ◽  
Transfer Efficiency ◽  
Clean Water ◽  
Test Tank ◽  
Fine Bubble ◽  
Oxygen Transfer Efficiency ◽  
Bubble Diffusers

Abstract We summarized the experience from three decades of oxygen transfer testing and aeration research at the Technical University of Darmstadt to validate the oxygen transfer efficiency of modern fine-bubble diffusers. A total of 306 oxygen transfer tests in clean water of 65 different fine-bubble diffusers, carried out in the same test tank under identical test conditions, were analysed and compared with previous results. As a result, we could show that the performance of fine-bubble aeration systems has increased by 17% over the last three decades. Therefore, modern well-designed and operated aeration systems can achieve specific standard oxygen transfer efficiency (SSOTE) values between 8.5 and 9.8% · m−1. Additionally, a comparison of various diffuser types and diffuser densities was done. Based on the new results, an exemplary cost/benefit analysis for a 100,000 PE WWTP shows the calculation of an optimized diffuser density with respect to investment and operating costs.

Oxygen transfer in gravity flow sewers

1995 ◽  
Vol 31 (7) ◽  
pp. 127-135 ◽  
Author(s):  
P. Balmér ◽  
M. Tagizadeh-Nasser
Keyword(s):  
Energy Dissipation ◽  
Oxygen Transfer ◽  
Laboratory Tests ◽  
Field Studies ◽  
Gravity Flow ◽  
Clean Water

Oxygen transfer to water in gravity flow pipes has been studied in a 24 m long, 0.225 m diameter sewer. Laboratory tests were conducted where the slope and flow in the sewer could be varied independently. The clean water reaeration test was used to determine the oxygen transfer. The KL value for the oxygen transfer was found to be a function of energy dissipation and mean hydraulic depth. The results are discussed in relation to oxygen transfer determinations in flumes and field studies of oxygen transfer in sewers.

Fine Bubble Aeration Using a High Density Diffuser System

1992 ◽  
Vol 26 (9-11) ◽  
pp. 2437-2440 ◽  
Author(s):  
K. Thatcher
Keyword(s):  
Activated Sludge ◽  
Oxygen Transfer ◽  
Oxygen Demand ◽  
High Density ◽  
Plant Performance ◽  
Energy Usage ◽  
High Quality ◽  
Transfer Rates ◽  
Fine Bubble ◽  
Activated Sludge Processes

Current developments with the activated sludge processes with highly concentrated effluents highlight the requirement to (a) reduce energy usage (b) promote the production of high quality effluent. Having observed the efforts being made to improve plant performance we became aware that current methods had to be improved. It was also noted that a period of stagnation had occurred in the development of effective aeration systems. Improved aeration methods are needed which would allow for oxygen transfer efficiencies to be greater than 2kg/kWh. Such oxygen transfer rates should be continually variable in line with the oxygen demand prevailing at any given time. In our study of activated sludge plants we found that operational and electrical/mechanical maintenance was proving to be time consuming and very costly. With these problems in mind we have designed and developed the Fine Bubble High Density Diffuser System.

scholarly journals Improving aeration systems in saline water (part II): effect of different salts and diffuser type on oxygen transfer of fine-bubble aeration systems

2021 ◽  
Author(s):  
J. Behnisch ◽  
M. Schwarz ◽  
J. Trippel ◽  
M. Engelhart ◽  
M. Wagner
Keyword(s):  
Oxygen Transfer ◽  
Large Scale ◽  
Saline Water ◽  
Tap Water ◽  
Pilot Scale ◽  
Mixed Salt ◽  
Water Oxygen ◽  
Aeration System ◽  
Fine Bubble ◽  
Scale Test

Abstract The objective of the present study is to investigate the different effects on the oxygen transfer of fine-bubble aeration systems in saline water. Compared to tap water, oxygen transfer increases due to the inhibition of bubble coalescence. In Part I of the present study, we investigated in lab-scale experiments the effect of design of diffuser membrane. The objective of Part II is the assessment of effects of different salts, diffuser type and diffuser density. We measured the concentration of various salts (MgCl2; CaCl2; Na2SO4; NaCl; KCl) above which coalescence is fully inhibited and oxygen transfer reaches its maximum (referred to as the critical coalescence concentration; CCC). For this purpose, we developed a new analytical approach, which enables to investigate the coalescence behaviour of any aeration system and (mixed) salt solution quickly and easily by evaluating the results of oxygen transfer tests. To investigate the transferability to large scale and the effect of diffuser type and density, we repeated lab-scale experiments in a 17,100 L pilot scale test tank and carried out additional tests with tube and plate diffusers at different diffuser densities. The results show, that despite the higher pressure drop, diffusers with dense slit density and smaller slits are to be recommended in order to improve efficiency of aeration systems in saline water.

Alpha correction factors for static aerators and fine bubble diffusers used in municipal facultative aerated lagoons

1998 ◽  
Vol 38 (3) ◽  
pp. 79-85 ◽  
Author(s):  
C. Asselin ◽  
Y. Comeau ◽  
Q. A. Ton-That
Keyword(s):  
Mass Transfer ◽  
Correction Factor ◽  
Process Water ◽  
Oxygen Mass Transfer ◽  
Clean Water ◽  
Correction Factors ◽  
Mixed Liquor ◽  
Fine Bubble ◽  
Steel Tank ◽  
Bubble Diffusers

The alpha correction factor (KLa process water/KLa clean water; where KLa is the volumetric oxygen mass transfer coefficient) was evaluated for 4 kinds of static aerators and 2 kinds of fine bubble diffusers used in municipal facultative aerated lagoons. For this purpose, a 40 m3 steel tank was filled (3.1 m side water depth) with clean or process water. The process water consisted of “mixed liquor” from a municipal facultative aerated lagoon divided into a cascade of four identical basins that were 3.5 m deep. Results showed that in the last three basins, the alpha correction factors were relatively high, being between 0.85 to 0.95 for any type of aeration device. In the first lagoon, however, the alpha correction factors were between 0.70 and 0.90 for static aerators and about 0.70 for fine bubble diffusers. Furthermore, at the inlet of the first basin, the alpha factor was as low as 0.59 for a static aerator and 0.26 for a fine bubble diffuser, due to the composition of the “mixed liquor”. It was shown that the alpha correction factor that should be used for the design of aeration systems for facultative aerated lagoons should be lower in the first basin of a series of basins and could be higher than 0.85 for the downstream basins.

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