Membrane Bioreactor Infiltration Control via Gravity Settling
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Solution Overview
Problem
Membrane bioreactors face challenges in handling large and variable wastewater flows, particularly during peak events like storms, as they are not adequately designed to manage sudden increases in influent without compromising treatment efficiency.
Innovation Solution
The system incorporates multiple treatment zones with membrane modules and a gravity settling device, allowing for the return of concentrated mixed liquor and controlled flow management to handle peak flows, maintaining optimal conditions for biomass growth and treatment efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If membrane bioreactor is designed for average flow, then treatment efficiency is maintained, but peak flow handling capability deteriorates
Solution Approach 1:
The system dynamically adjusts the return activated sludge (RAS) flow rate based on influent flow conditions. During peak flows, the RAS flow is increased to maintain appropriate food-to-microorganism ratios and prevent membrane overload, while during average flows, the RAS flow is reduced to maintain optimal treatment efficiency. This dynamic adjustment allows the system to adapt to varying flow conditions without compromising treatment performance.
Solution Approach 2:
The system changes operational parameters (specifically RAS flow rate and mixed liquor suspended solids concentration) in response to different flow conditions. By adjusting these parameters dynamically, the system maintains optimal biological activity and membrane performance during both average and peak flow conditions, resolving the contradiction between maintaining treatment efficiency and handling peak flows.
2Adaptability or versatility
If return activated sludge flow is increased to handle peak flows, then peak flow capacity improves, but food to micro-organism ratio deteriorates
Solution Approach 1:
The system dynamically adjusts the RAS flow rate as a controllable parameter in response to changing influent flow conditions. During peak flows, RAS flow is increased to maintain system capacity, and the corresponding change in F/M ratio is managed through coordinated control of other parameters to maintain biological performance.
Solution Approach 2:
The system uses feedback control mechanisms to monitor flow conditions and adjust RAS flow accordingly. By continuously monitoring influent flow and system response, the control system optimizes RAS flow to maintain appropriate F/M ratios while handling varying flow conditions, preventing both overload and underutilization of the biological system.
3Adaptability or versatility
If membrane area is increased to handle peak flows, then peak flow handling improves, but system complexity and cost deteriorate
Solution Approach 1:
Instead of increasing membrane area statically, the system uses dynamic control of RAS flow to adjust system capacity in real-time. This dynamic approach allows the same membrane area to effectively handle both average and peak flows by modulating the biological system's processing capacity, avoiding the need for additional membrane infrastructure.
Solution Approach 2:
The system uses the existing biological treatment capacity and membrane infrastructure more efficiently by optimizing operational parameters. The controlled adjustment of RAS flow enables the existing system to self-adjust its capacity to handle varying flows, eliminating the need for additional membrane area and reducing system complexity.
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 enables efficient handling of both average and peak wastewater flows, ensuring continuous treatment performance without compromising the membrane bioreactor's operation, even during high inflow conditions, by utilizing multiple treatment zones and a gravity settling device to manage flow and maintain optimal conditions for biomass growth.
Implementation Method 1
flowing a portion of the returned mixed liquor to a gravity settling device and clarifying the mixed liquor within the gravity settling device
Implementation Method 2
passed through a filter membrane to produce a concentrated mixed liquor and a filtrate
Data Source
AI summary
A wastewater treatment system comprising: a first treatment zone (11) fluidly connected to one or more further treatment zones (12-14), a membrane module (16) comprising a filter membrane is positioned in or fluidly connected to the further treatment zone; and a gravity settling device (15) fluidly connected to the first treatment zone (11) to receive overflow therefrom. A method of treating wastewater comprising flowing wastewater through one or more treatment zones (11-14) to produce a fluid product which is passed through a filter membrane (16) to produce a concentrated mixed liquor and a filtrate; returning at least a portion of the concentrated mixed liquor to at least one of the treatment zones (11); when the flow of wastewater water exceeds a predetermined level, flowing a portion of the returned mixed liquor to a gravity settling device (15) and clarifying the mixed liquor within the gravity settling device (15).