Granular Filter Backwashing With Flow Rate Fluctuation
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Solution Overview
Problem
Existing methods for backwashing fluidized granular filters, such as those used for sewage or contaminated water, are inefficient in removing contaminants quickly, leading to clogging, and do not effectively reduce water, energy, or time consumption, and often result in channeling issues within the filter material.
Innovation Solution
A method involving a fluctuating flow rate between a higher and lower flow rate during the backwashing cycle, which alternates cyclically, ensures efficient contaminant removal by fluidizing different fractions of the granular material, preventing channeling, and optimizing water, energy, and time usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a constant flow rate backwashing method is used, then the backwashing process is simple to operate, but contaminant removal is inefficient and channeling occurs
Solution Approach 1:
The backwashing process uses periodic fluctuation of flow rate between high and low values. The high flow rate phase fluidizes the granular material to dislodge and remove contaminants, while the low flow rate phase allows partial settling. This periodic action repeats multiple times during the backwashing cycle, significantly improving contaminant removal efficiency compared to constant flow rate methods.
2Loss of time
If a high flow rate is used throughout backwashing, then contaminant removal is fast, but water and energy consumption increase
Solution Approach 1:
Instead of maintaining high flow rate continuously, the method alternates between high flow rate (for rapid contaminant removal) and low flow rate (for energy conservation). The high flow rate is applied only during necessary fluidization phases, while low flow rate is used during settling phases, reducing overall water and energy consumption while maintaining effective backwashing time.
Solution Approach 2:
The flow rate parameter is dynamically changed during the backwashing process rather than remaining constant. The system adjusts flow rate between high and low values based on the operational phase (fluidization vs. settling), optimizing the balance between backwashing speed and resource consumption.
3Reliability
If a constant low flow rate is used at the end of backwashing, then channeling is prevented, but water consumption increases
Solution Approach 1:
During the final settling phase, the method uses periodic low flow rate pulses rather than continuous low flow rate. This periodic action maintains sufficient flow to prevent channeling and ensure proper settling, while allowing the system to consume less water overall compared to continuous low flow rate operation.
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 significantly reduces contaminant concentration within the filter to one-hundredth of the initial level, prevents channeling, and achieves water, energy, and time savings by effectively removing contaminants while maintaining filter efficacy.
Implementation Method 1
by means of injecting an injection flow rate fluctuating between two values: a higher flow rate and a lower flow rate... This flow rate fluctuation allows removing contaminants from the granular material more quickly... The mentioned higher cleaning flow rate provides a stream of clean liquid that is displaced through the granular material at a speed greater than the sedimentation rate of a top fraction of the grain size distribution forming the granular material of the filter, causing at least that fraction of the grain size distribution to enter a fluidization state
Implementation Method 2
The injected liquid will be discharged, after going through the entire thickness of the granular material, through backwashing outlets, entraining the contaminants therewith, as it is displaced by the new injected clean liquid
Implementation Method 3
The injected liquid will be discharged, after going through the entire thickness of the granular material, through backwashing outlets, entraining the contaminants therewith... At the same time said speed will be less than the upward entrainment rate of the bottom fraction of the grain size distribution forming the granular material of the filter to the backwashing outlet, thus preventing the granular material forming the filter from being entrained out of the filter during said backwashing cycle
Data Source
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AI summary
The present invention relates to a method for filter backwashing a filter for filtering liquids made up of a granular material by means of a backwashing cycle which comprises injecting a clean liquid through said filter in a direction opposite the filtering direction, distributing said liquid homogenously throughout the filter and discharging said liquid through a backwashing outlet; using a cleaning flow rate long enough to eliminate most of the contaminants retained in the filter and a terminal flow rate to displace a volume of residual liquid of the filter; characterized in that said cleaning flow rate fluctuates between at least two values, one of these values being a higher flow rate and the other being a lower flow rate, said fluctuation being repeated a plurality of times in each backwashing cycle.