Concentric Dual Drum Screen for Wastewater Filtration
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Solution Overview
Problem
Dual stage screening systems for membrane biological reactors (MBR) face challenges with high costs and large footprints due to separate screens and grit removal systems, and existing designs suffer from screenings sloughing off before collection, affecting performance and maintenance.
Innovation Solution
A concentric dual drum screen system is designed without a dividing wall, with the first screen nested within a larger, finer second screen, allowing screenings to collect on the inner surfaces and be efficiently conveyed to a collection hopper, reducing footprint and improving hydraulic performance by increasing the effective filtration area of the finer screen.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a dual stage screening system uses two separate screens with a dividing wall, then screening effectiveness is improved, but the footprint and device complexity increase
Solution Approach 1:
The patent applies nesting by placing the first drum screen inside the second drum screen, with the first screen having a smaller diameter and being positioned concentrically within the second screen. This nested configuration allows both screens to occupy the same spatial envelope, dramatically reducing the overall footprint while maintaining dual-stage screening functionality. The inner screen handles coarse screening while the outer screen provides fine screening, achieving reliable multi-stage filtration in a compact arrangement.
Solution Approach 2:
The patent merges two separate screening functions into a single integrated apparatus by eliminating the dividing wall and combining both drum screens within a common housing. The first and second screens operate simultaneously in a nested configuration, sharing the same support structure, drive mechanism, and collection system. This merging reduces device complexity and footprint while maintaining effective dual-stage screening.
2Measurement precision
If the second screen has smaller openings for finer filtration, then screening precision is improved, but hydraulic performance deteriorates due to restricted flow
Solution Approach 1:
The patent resolves the hydraulic restriction problem by transitioning from a single-plane screening approach to a three-dimensional nested arrangement. The first screen with larger openings is positioned inside the second screen with smaller openings, creating multiple filtration planes. This dimensional change allows the system to maintain fine filtration precision while compensating for hydraulic restrictions through the combined effective area of both screens operating in series.
Solution Approach 2:
The patent segments the filtration function into two distinct stages with different screen openings. The first screen provides coarse filtration with larger openings to handle high flow rates, while the second screen provides fine filtration with smaller openings. This segmentation allows each screen to be optimized for its specific function, maintaining both hydraulic performance and screening precision.
3Ease of operation
If screenings are collected on the outside surface of the second screen, then collection is simplified, but screenings slough off before reaching the collection hopper
Solution Approach 1:
The patent inverts the conventional collection approach by collecting screenings on the inside surfaces of both screens rather than on the outside. The first screen collects screenings on its inner surface, and the second screen collects screenings on its inner surface. This inversion prevents screenings from sloughing off during rotation, as they are contained against the inner screen surfaces and properly conveyed to collection hoppers located at the top of each drum.
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 configuration enhances the efficiency and maintenance of the dual screen system by reducing the overall footprint, improving hydraulic performance, and ensuring effective screening collection without sloughing, thus protecting the MBR system.
Implementation Method 1
a first drum screen and a second drum screen, each having a cylindrical shape and arranged concentrically with a common longitudinal axis, the first drum screen having a smaller diameter than the second drum screen
Implementation Method 2
Each drum has a lift mechanism that conveys the collected screenings upward along the drum
Implementation Method 3
spray wash systems that spray wash the outer surfaces of the drums to remove the screenings
Data Source
AI summary
A dual drum screen system for wastewater has a first, inner drum positioned within a second, outer drum. Wastewater is filtered first by a filter screen of the inner drum, then by a finer filter screen of the outer drum. Both drums rotate together on a central shaft with a common drive system.