Membrane Aerated Biofilm Reactor Draft Tube Mixing
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Solution Overview
Problem
Membrane aerated biofilm reactors (MABRs) face challenges in maintaining effective mixing and contact between pollutant-degrading biofilms and wastewater due to oxygen transfer limitations and high energy demands associated with conventional aeration methods, limiting their scalability beyond laboratory scale.
Innovation Solution
A draft tube system within the MABR housing creates a flow of liquid waste from the lower to the upper headspace, using a pressure differential generated by a propeller pump or gas introduction, allowing for settling of detached biofilm particles while maintaining fluid communication and reducing energy requirements for mixing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional bubble aerators or surface aerators are used for oxygen transfer in MABR, then oxygen supply to biofilm is improved, but energy consumption increases and mixing is limited in tanks with flow restrictions
Solution Approach 1:
The patent extracts the oxygen transfer function from conventional bubble aeration systems and implements it directly through the membrane structure. The membrane provides oxygen transfer without requiring separate aeration devices, eliminating the energy consumption associated with bubble generation while maintaining effective oxygen supply to the biofilm.
Solution Approach 2:
The membrane acts as an intermediary between the gas phase and liquid phase, enabling oxygen transfer without direct gas-liquid contact. This intermediary structure allows oxygen to diffuse through the membrane into the biofilm while avoiding the energy-intensive bubble formation process used in conventional aeration systems.
2Stability of the object's composition
If large submerged mixers or jet mixers are used for mixing in MABR, then biomass suspension is improved, but energy demand increases significantly
Solution Approach 1:
The patent implements self-service mixing where the upward flow of liquid waste through the draft tube automatically creates mixing action. The system uses its own operational flow (driven by the propeller pump or gas lift) to generate the mixing effect, eliminating the need for separate high-energy mixing devices while maintaining effective biomass suspension.
3Productivity
If MABR technology is scaled up from laboratory to full-scale applications, then treatment capacity is improved, but maintaining effective mixing and contact between biofilms and wastewater becomes difficult
Solution Approach 1:
The draft tube system serves multiple functions simultaneously: it provides liquid circulation, creates mixing action through upward flow, enables biomass suspension, and facilitates contact between biofilms and wastewater. This multi-functional design allows the system to maintain effective operation when scaled up, addressing multiple operational requirements with a single structural element.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables efficient mixing and contact between biofilms and wastewater, allowing for effective pollutant removal and biofilm settlement, reducing energy consumption and enabling long-term high-performance operation of MABRs in full-scale applications.
Implementation Method 1
using a pressure differential generated by a propeller pump or gas introduction
Implementation Method 2
gas introduction, allowing for settling of detached biofilm particles
Implementation Method 3
allowing for settling of detached biofilm particles while maintaining fluid communication
Implementation Method 4
Oxygen diffuses through the membrane into the biofilm where oxidation of pollutants
Implementation Method 5
oxidation of pollutants, supplied at the biofilm-liquid interface, takes place
Data Source
AI summary
A device for treating wastewater liquids, the device comprising a housing (4) incorporating a membrane supported biofilm reactor (MSBR) (2) of the type comprising a lumen containing a gas phase, a liquid phase, and a gas permeable membrane (20) providing an interface between the gas and liquid phases; and a means (6) for mixing the wastewater liquids in the device, wherein the means (6) for mixing the wastewater liquids is configured to create a mixing intensity sufficient to ensure that there is contact between the membrane (20) and the wastewater liquid to be treated.