Rotating Screen for Selective Solids Retention in Activated Sludge
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Solution Overview
Problem
Current wastewater treatment methods are inadequate in selectively retaining and enhancing biological solids for improved activated sludge performance, as they lack efficient mechanisms for physical separation and retention based on particle size, coagulation, flocculation, filtration, and shear resistance.
Innovation Solution
A device such as a screen is used to selectively retain particulate constituents based on physical factors like particle size, diffusion, coagulation, flocculation, filtration, shear, viscosity, gravimetry, or compressibility, applying shear and tangential stress to coagulate, flocculate, or filter solids, and varying parameters like rotating speed or vibration to control retention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional wastewater screening methods are used to remove large solids, then debris removal is achieved, but selective retention of biological solids for enhanced activated sludge performance is not achieved
Solution Approach 1:
The screen is divided into multiple zones with different aperture sizes to selectively retain different fractions of solids. The screen surface is segmented into zones that capture inert material, biological solids, and fine particles separately, allowing differential retention based on particle characteristics rather than a single uniform filtration approach.
Solution Approach 2:
Different regions of the screen possess different local properties - varying aperture sizes, orientations, and retention characteristics are created in different zones of the screen surface. This allows each local area to perform a specific function in the solids separation process, such as capturing coarse debris in one zone while retaining fine biological solids in another zone.
2Loss of time
If screens are used to retain solids based on particle size, then solid-liquid separation is improved, but uncoupling of solids residence time for retained and non-retained fractions is not achieved
Solution Approach 1:
The screen is designed to rotate or move dynamically through different process zones, allowing retained solids to be selectively removed at different times and locations. This dynamic operation enables independent control of residence time for different solid fractions - inert material can be retained longer while biological solids are returned to the bioreactor promptly, optimizing both separation efficiency and time management.
3Manufacturing precision
If physical separation based on multiple physical forces is implemented, then selective retention of solids is achieved, but device complexity and operational parameters increase
Solution Approach 1:
A single screen device performs multiple separation functions simultaneously by incorporating zones with different aperture characteristics. The same screen structure utilizes gravity, filtration, and shear forces across different zones to achieve particle size-based separation, coagulation, and flocculation in an integrated manner, avoiding the need for multiple separate separation devices.
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 enhances activated sludge performance by uncoupling solids residence time, allowing for additional reaction time and improving flocculation and filtration efficiency, which can be applied to various water treatment processes beyond wastewater, including agricultural runoff and hazardous waste treatment.
Implementation Method 1
Physical forces (shear/tangential stress and/or normal stress) are used to coagulate, flocculate or filter solids, where these coagulated, flocculated and filtered materials are retained
Implementation Method 2
Physical forces (shear/tangential stress and/or normal stress) are used to coagulate, flocculate or filter solids, where these coagulated, flocculated and filtered materials are retained
Implementation Method 3
Physical forces (shear/tangential stress and/or normal stress) are used to coagulate, flocculate or filter solids, where these coagulated, flocculated and filtered materials are retained
Implementation Method 4
Physical separation to allow for selection of two fractions based on physical forces is a key aspect of this application. The separation can occur based on physical factors such as particle size, diffusion, coagulation, flocculation, filtration, shear, viscosity, gravimetry, floatation, or compressibility
Implementation Method 5
The separation can occur based on physical factors such as particle size, diffusion, coagulation, flocculation, filtration, shear, viscosity, gravimetry, floatation, or compressibility
Data Source
AI summary
An apparatus and method for selecting, retaining or bioaugmenting solids in an activated sludge process for improving wastewater treatment using a screen device. If desired, the screen device may include a drum, and the rotating speed of the drum may be used to control the solids retained. Effluent including waste biomass may exit the screen device. No other discharge unit from the screen device may be required.