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.

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 A contact angle study of different greywater sources with hydrophobic membranes

2020 ◽  
Vol 55 (3) ◽  
pp. 310-326
Author(s):  
Mohammad Ramezanianpour ◽  
Muttucumaru Sivakumar ◽  
Natalie Osborn ◽  
Ying Zhang ◽  
Hakim Kawa
Keyword(s):  
Surface Tension ◽  
Contact Angle ◽  
Pure Water ◽  
Membrane Distillation ◽  
Hydrophobic Membrane ◽  
Flat Sheet ◽  
Hydrophobic Membranes ◽  
Different Types ◽  
The Impact ◽  
Surface Tension Forces

Abstract The wetting phenomenon is a major problem in the membrane distillation (MD) process, and it is the main reason that limits MD being used in wastewater reclamation. Active surfactant in the detergents reduces the contact angle between the liquid and the hydrophobic membrane surface, which could result in wetting. Extensive laboratory research was conducted using commercial hydrophobic flat-sheet membranes to identify the impact of anionic surfactants and surface tension forces on these membranes. The aim of this paper is to find a suitable membrane for pure water production from greywater using MD, as well as to provide a relationship between surfactant concentration and the contact angle for different types of membrane. The absorbance of each sample was measured by a spectrophotometer prior to the contact angle test on four different types of hydrophobic membranes. It was concluded that the polypropylene membrane would be unsuitable for the treatment of greywater directly due to the loss of surface tension forces upon the addition of an anionic surfactant. However, the polytetrafluoroethylene membrane could be effective in this process while the concentration of surfactant in the feed source is kept constant. The results from the experimental tests proposed a relationship between the contact angle of a water droplet on the surface of a flat-sheet membrane and the concentration of surfactant in the solution.

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

1998 ◽  
Vol 38 (3) ◽  
pp. 35-42 ◽  
Author(s):  
G. Déronzier ◽  
Ph. Duchène ◽  
A. Héduit
Keyword(s):  
Water Flow ◽  
Flow Rate ◽  
Oxygen Transfer ◽  
Contact Time ◽  
Air Flow ◽  
Interfacial Area ◽  
Design Parameters ◽  
Air Bubbles ◽  
Air Flow Rate ◽  
Fine Bubble

The influence of design parameters on the transfer of oxygen was studied in different ring ditches equipped with fine bubble membrane air diffusers and separate mixing. The results produced evidence that the oxygen transfer efficiency (OTE) decreases when the air flow rate per diffuser increases. OTE increases asymptotically with the horizontal water flow (50% for velocity up to 0.5 m/sec). It increases also when the diffuser modules are brought closer together. Theoretical analysis enabled ranking of the impact of the design parameters on which the oxygen transfer is dependent, namely the interfacial area (a) and the oxygen transfer coefficient (Kl). The increase in the air flow rate per diffuser essentially reduces the interfacial area by an increase in the diameter of the initial air bubbles and by a reduction of the contact time due to an acceleration of the “spiral flows” (vertical rotation of water flow). The horizontal rotation of water increases the interfacial area most probably by decreasing the diameter of the initial air bubbles and by a lengthening of the contact time resulting from a reduction in the large spiral flows. Bringing the diffuser modules closer together makes longer the contact time by a reduction in the large spiral flows.

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.

Determining the effect of solid and liquid vectors on the gaseous interfacial area and oxygen transfer rates in two-phase partitioning bioreactors

2010 ◽  
Vol 175 (1-3) ◽  
pp. 1085-1089 ◽  
Author(s):  
Guillermo Quijano ◽  
José Rocha-Ríos ◽  
Maria Hernández ◽  
Santiago Villaverde ◽  
Sergio Revah ◽  
...  
Keyword(s):  
Oxygen Transfer ◽  
Interfacial Area ◽  
Two Phase ◽  
Transfer Rates ◽  
Phase Partitioning

Pure oxygen desorption method - a new and cost-effective method for the determination of oxygen transfer rates in clean water

1998 ◽  
Vol 38 (3) ◽  
pp. 103-109 ◽  
Author(s):  
Martin R. Wagner ◽  
H. Johannes Poöpel ◽  
Peter Kalte
Keyword(s):  
Oxygen Saturation ◽  
Oxygen Transfer ◽  
Sodium Sulphite ◽  
Pure Oxygen ◽  
Clean Water ◽  
Absorption Method ◽  
Transfer Rates ◽  
Oxygen Desorption ◽  
Saturation Concentration ◽  
Desorption Method

Many clean water tests with the well known absorption method using sodium sulphite for deoxynation have shown that there are problems connected with solving these chemicals. Because of this, a new test method was developed at the Darmstadt University of Technology to determine oxygen transfer rates fine bubble aeration systems without sodium sulphite and a cobalt catalyst. The new method is called “Pure oxygen desorption method”. Contrary to the absorption method, the oxygen concentration in the test tank is increased well above the normal oxygen saturation concentration. This high excess concentration is obtained by feeding pure oxygen into the main pipe of the fine bubble aeration system. After starting normal aeration, the oxygen concentration in the clean water decreases towards the oxygen saturation concentration by stripping of the excess oxygen. The desorption curve is used to calculate the parameter aeration coefficient kLa and oxygen saturation concentration under process conditions c∞*. In comparison to the absorption method with sodium sulphite, the pure oxygen desorption method is a simple and cost-effective method for determining oxygen transfer rates.

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.

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