Membrane Fouling Control via Post-Cleaning Air Diffusion
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Solution Overview
Problem
Conventional methods for resuming operation of membrane-separation activated sludge treatment devices after chemical cleaning fail to effectively determine optimal operating conditions, leading to rapid membrane clogging and increased chemical cleaning frequency, due to inadequate assessment of fouling potential and membrane recovery.
Innovation Solution
A method is introduced that involves interrupting filtration and injecting a chemical cleaning solution into the membrane module, followed by resuming operation based on specific conditions such as air diffusion resumption and preliminary filtration at reduced flux, using criteria like turbidity, membrane filtration resistance, and TOC concentration to assess fouling material characteristics and ensure membrane recovery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If filtration operation is resumed immediately after chemical cleaning at high flux, then productivity is improved, but membrane reliability deteriorates due to rapid clogging
Solution Approach 1:
The patent applies preliminary action by performing air diffusion for a predetermined period before resuming filtration operation. This preliminary air diffusion removes fouling materials from the membrane surface that were generated during chemical cleaning, thereby preventing rapid clogging when high-flux filtration is resumed. The air diffusion creates upward flow that physically cleans the membrane surface before the harmful filtration operation begins.
Solution Approach 2:
The patent implements periodic action by alternating between air diffusion mode and filtration mode. Instead of continuous filtration, the system periodically switches to air diffusion mode to clean the membrane surface, then returns to filtration mode. This periodic switching prevents accumulation of fouling materials and maintains membrane performance during extended operation after chemical cleaning.
2Manufacturing precision
If chemical cleaning is performed with high treatment strength, then manufacturing precision is improved (membrane water permeability restored), but object-generated harmful factors increase (activated sludge damage and fouling material generation)
Solution Approach 1:
The patent converts the harmful effect of chemical cleaning (which damages activated sludge and generates fouling materials) into a beneficial process. By performing air diffusion immediately after chemical cleaning, the system uses the upward airflow to remove the fouling materials that were generated during cleaning, transforming the harmful byproducts into removable debris. This allows the system to benefit from the thorough cleaning while mitigating the negative effects of sludge damage.
Solution Approach 2:
The patent introduces air diffusion as an intermediary process between chemical cleaning and filtration operation. This intermediary step serves as a buffer that removes fouling materials generated during chemical cleaning before they can be adsorbed onto the membrane during filtration. The air diffusion acts as a mediator that protects the membrane from the harmful effects of chemical cleaning by eliminating fouling materials in between the cleaning and filtration stages.
3Reliability
If air diffusion is performed for extended period after chemical cleaning, then membrane reliability is improved (fouling material removal), but loss of time increases
Solution Approach 1:
The patent applies feedback by monitoring the transmembrane pressure difference during and after air diffusion operation. When the pressure difference stabilizes or begins to decrease, indicating that fouling materials have been sufficiently removed, the system automatically transitions from air diffusion mode back to filtration mode. This feedback-based control prevents excessive air diffusion time while ensuring adequate fouling material removal, thereby optimizing the balance between membrane reliability and operational time loss.
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 minimizes membrane contamination, reduces transmembrane pressure increase, and extends the time between chemical cleanings, thereby prolonging membrane and module lifespan while maintaining stable filtration performance.
Implementation Method 1
air is diffused from a diffuser tube disposed below the membrane module, and filtration is performed so that the membrane surface is physically cleaned constantly by the generated upward flow
Implementation Method 2
air for aerating the membrane surface is supplied from below the membrane module for an appropriate time to peel off the membrane surface deposit
Implementation Method 3
the activated sludge is separated by solid-liquid separation using a membrane module immersed in a water tank, so that clear membrane-filtered water can be obtained as treated water
Implementation Method 4
an operation, or chemical cleaning, of chemically washing the membrane using a chemical solution to restore the water permeability of the membrane is performed
Data Source
AI summary
An object of the present invention is to provide a specific method for determining the fouling potential of an activated sludge solution on the basis of the characteristics of the activated sludge solution after chemical cleaning of a membrane, and to provide a suitable method for resuming operation in a rational manner after chemical cleaning of the membrane, while accurately determining the degree of recovery of the membrane filtration characteristics for the activated sludge solution. Moreover, an object of applying the present invention is to enable more effective suppression of an increase in a transmembrane pressure difference after chemical cleaning than in the prior art, leading to a reduction in the cleaning frequency of the membrane and a reduction in the used amount of cleaning chemicals and to extension of the life of the membrane.The present invention relates to a method for operating a membrane-separation activated sludge treatment device after chemical cleaning of a membrane, the method including, after the chemical cleaning of the membrane is completed, controlling an operating condition until a normal filtration operation is resumed on the basis of characteristics of an activated sludge solution.