Continuous Wastewater Treatment Granular Sludge Selection
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Solution Overview
Problem
Current wastewater treatment processes are unable to maintain granular sludge formation in continuous operations, which is essential for efficient settling and reduced plant size, as granular sludge settles much faster than flocs, but existing methods do not effectively promote the growth of fast settling sludge in continuous processes.
Innovation Solution
A continuous wastewater treatment process involving an anaerobic step, an aerobic step, a sludge selection step, and a sludge removal step, where fast settling sludge is recycled back to the anaerobic zone and slow settling sludge is directed to the aerobic zone, allowing for the selective promotion of granular sludge growth and maintenance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If conventional continuous wastewater treatment processes are used, then continuous operation is achieved, but granular sludge formation cannot be maintained
Solution Approach 1:
The continuous process is segmented into distinct functional zones (anaerobic zone, aerobic zone, settling zone) with selective sludge recycling. Fast-settling granular sludge is specifically recycled to the anaerobic zone while slow-settling sludge is recycled to the aerobic zone, maintaining granular sludge stability in continuous operation
Solution Approach 2:
Different sludge types are directed to different zones based on their settling characteristics. Fast-settling granular sludge is concentrated and returned to the anaerobic zone where it performs best, while slow-settling sludge is returned to the aerobic zone, optimizing the local quality and function of each zone
2Reliability
If large settling tanks are used for sludge separation, then separation efficiency is improved, but plant area increases
Solution Approach 1:
The invention changes the key parameter of sludge settling velocity by promoting granular sludge formation, which settles much faster than conventional flocs. This parameter change allows for significantly reduced settling tank area while maintaining separation efficiency
3Productivity
If slow settling sludge is recycled to anaerobic zone, then continuous operation is maintained, but granular sludge growth is inhibited
Solution Approach 1:
The sludge recycling stream is segmented into two separate paths: fast-settling granular sludge is recycled to the anaerobic zone to promote granular sludge growth, while slow-settling sludge is recycled to the aerobic zone to maintain continuous operation without inhibiting granular sludge formation
Solution Approach 2:
Each sludge recycling path is optimized for its specific function: the anaerobic zone receives concentrated fast-settling granular sludge to maintain granular sludge stability, while the aerobic zone receives slow-settling sludge to ensure continuous 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 process enables the formation and maintenance of granular sludge, reducing the need for large settling tanks, allowing for faster upflow without compromising separation efficiency, and eliminating the requirement for an anoxic tank, resulting in a more simplified and effective wastewater treatment system.
Implementation Method 1
sludge is selected based on settling velocity
Data Source
AI summary
A process for the treatment of wastewater is disclosed, which comprises (a) contacting the wastewater with fast settling sludge from step (c) in an anaerobic zone, obtaining a mixture of wastewater and sludge; (b) subjecting the mixture from step (a) and slow settling sludge from step (c) to an aerobic zone, obtaining a water and sludge mixture; (c) subjecting a first part of the mixture from step (b) to a sludge selection step, wherein sludge is selected based on settling velocity and a first portion containing slow settling sludge and a second portion containing fast settling sludge are collected, wherein average settling velocity of the fast settling sludge is greater than that of the slow settling sludge, and wherein the first portion is returned to step (b) and the second portion is returned to step (a); and (d) separating sludge from a second part of the mixture from step (b).