Underdrain Gas-Liquid Distribution for Filter Media
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Solution Overview
Problem
Lateral-style filter underdrains fail to distribute air evenly across the filter area at low gas scour rates, necessitating a method for even and efficient gas distribution at both low and traditional rates during the filtration and backwashing processes.
Innovation Solution
A method involving the positioning of underdrain blocks with a gas inlet and liquid inlet, where gas is distributed at rates of less than 2 scfm/ft², accompanied by liquid at specific flow rates, allowing for gradual increase and decrease of liquid flow to ensure even gas distribution across the filter area, including during backwashing and upflow filtration processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If gas is distributed through lateral-style filter underdrains at low scour rates, then energy consumption is reduced, but gas distribution uniformity deteriorates
Solution Approach 1:
A liquid intermediary (water) is introduced into the underdrain system to facilitate gas distribution. The liquid flows through the underdrain blocks and laterals, creating pathways that guide gas flow and ensure uniform distribution across the filter area even at low gas rates. This intermediary fluid resolves the contradiction by providing a mechanical medium that enhances gas distribution uniformity without requiring high gas flow rates.
Solution Approach 2:
The system changes the operational parameters by introducing liquid flow rate as a controlling variable alongside gas flow rate. By adjusting the liquid flow parameter, the system can maintain uniform gas distribution at lower gas rates. The interaction between liquid and gas flow parameters creates optimal distribution conditions that neither parameter could achieve alone.
2Manufacturing precision
If gas distribution rate is increased to traditional rates, then gas distribution uniformity improves, but energy consumption increases
Solution Approach 1:
The liquid intermediary serves as a flow guide that enables uniform gas distribution at reduced gas rates. By providing structured pathways through the underdrain system, the liquid mediator allows the gas to follow efficient flow patterns that maintain uniformity without requiring high energy input.
Solution Approach 2:
The system optimizes the gas-to-liquid flow rate ratio to achieve uniform distribution at lower energy consumption. By carefully controlling the liquid flow parameter, the system creates conditions where gas distributes uniformly at rates below traditional requirements, thus reducing energy usage while maintaining distribution quality.
3Manufacturing precision
If liquid is distributed concurrently with gas at low rates, then gas distribution uniformity improves, but system complexity increases
Solution Approach 1:
The underdrain system is designed to perform multiple functions: it distributes both liquid and gas phases, collects filtrate, and provides structural support. The same underdrain blocks and laterals that traditionally handled only liquid collection now serve as dual-phase distribution media, eliminating the need for separate gas distribution infrastructure and thus not significantly increasing system complexity.
Solution Approach 2:
The gas distribution function is merged with the existing liquid distribution system. Gas and liquid share the same physical pathways (underdrain blocks and laterals), combining two distribution functions into one integrated system. This merging approach avoids adding separate complex gas distribution components while achieving uniform gas distribution.
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
Enables even gas distribution at low scour rates while maintaining the ability to distribute gas at traditional rates, effectively cleaning the filter media and improving filtration efficiency by ensuring all areas are cleaned during backwashing.
Implementation Method 1
distributing gas sufficiently evenly through the underdrain system at a rate of less than 2 scfm/ft2 by distributing a liquid at a rate of less than 2 gpm/ft2 concurrently with the gas
Data Source
AI summary
A method of distributing gas and liquid through an underdrain system includes: a) positioning an underdrain system on a filter floor, the underdrain system comprising at least one underdrain block and filter media positioned on top of the underdrain block; b) distributing gas sufficiently evenly through the underdrain system at a rate of less than 2 scfm/ft2 by distributing a liquid at a rate of less than 2 gpm/ft2 concurrently with the gas; c) increasing the distribution rate of the liquid, or increasing the distribution rate of the liquid and the distribution rate of the gas; d) stopping the distribution of gas; e) further increasing the distribution rate of the liquid; and f) decreasing the distribution rate of the liquid. A method of distributing gas and liquid during an upflow filtration mode is also included.