Peak Flow Management in Wastewater Using Direct Membrane Filtration
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Solution Overview
Problem
Submerged membrane bioreactors face challenges in handling peak hydraulic loads, leading to high operational and capital costs due to the need for large biosolids inventory and energy-intensive blower operation, and are cost-prohibitive for systems with significant transient peaking factors, especially during heavy rainfall or snowmelt events.
Innovation Solution
Implementing an offline ultrafiltration system combined with activated carbon and zeolite for treating short-term peak flows, which diverts excess wastewater for physical-chemical treatment, reducing the load on submerged membrane bioreactors and eliminating the need for air scouring, thereby reducing energy usage and capital expenses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If submerged membrane bioreactor capacity is increased to handle peak instantaneous flow, then hydraulic capacity is improved, but capital costs and operating costs increase
Solution Approach 1:
The system divides wastewater flow into two separate treatment paths: a first portion (normal flow) is treated by the submerged membrane bioreactor, while a second portion (excess peak flow) is treated by an independent filtration process. This segmentation allows each system to be sized appropriately for its specific function, avoiding the need to oversize the MBR for peak conditions.
Solution Approach 2:
The patent extracts the peak flow treatment function from the main MBR system by implementing a separate filtration process. This extracted subsystem handles only the excess portion of peak flow, allowing the MBR to operate at its optimal design capacity without the burden of handling transient hydraulic peaks.
2Productivity
If large inventory of biosolids is maintained to handle transient instantaneous flow, then hydraulic capacity is improved, but operating costs increase due to oxygen requirements
Solution Approach 1:
The system segments the treatment function so that the MBR maintains only the biosolids inventory necessary for its rated average capacity, while the separate filtration process handles peak flows without requiring large biosolids inventories or associated aeration energy.
Solution Approach 2:
The patent extracts the peak flow management function from the biological system, using a physical-chemical filtration process that does not require maintaining large inventories of living biosolids or the energy-intensive aeration needed to sustain them during low-flow periods.
3Productivity
If blower operation is sustained to maintain hydraulic capacity, then hydraulic capacity is improved, but electrical load increases
Solution Approach 1:
The system segments the hydraulic capacity function between the MBR (for average flow) and the separate filtration process (for peak flow). This allows blower operation to be optimized for the MBR's actual operating conditions rather than being sustained at high levels to handle rare peak events.
Solution Approach 2:
The patent extracts the peak flow handling capability from the biological system, using a filtration process that does not depend on sustained blower operation or large inventories of aerated biosolids, thereby reducing the electrical load required to maintain hydraulic capacity.
4Productivity
If MBR is designed to handle highest expected peak instantaneous flow, then hydraulic capacity is improved, but both capital costs and operating costs become prohibitive
Solution Approach 1:
The system segments the total flow into a first portion treated by the MBR and a second portion treated by the filtration process. The MBR is designed for rated average capacity rather than peak capacity, while the filtration process is sized to handle only the excess portion during peak events, making both systems economically viable.
Solution Approach 2:
The patent extracts the peak flow treatment function from the MBR system and implements it as a separate, smaller filtration system. This extracted subsystem handles only the transient peak flows, allowing the main MBR to be sized economically for average conditions while still providing adequate peak flow management.
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 efficiently manages short-term peak events while meeting stringent permit limits, significantly reducing energy consumption and capital costs by utilizing offline ultrafiltration and physical-chemical treatment, and allows for the reuse of retentate in the MBR system, enhancing phosphorus removal and filterability.
Implementation Method 1
adding a flocculating agent to the second portion entering filtration
Implementation Method 2
filtering the second portion, thereby producing retentive waste including flocculated material
Implementation Method 3
sending the retentive waste to the submerged membrane filter
Data Source
AI summary
A biological wastewater treatment system includes an equalization tank for sending a defined first portion of the wastewater to a submerged membrane filter. When the quantity of the received wastewater exceeds the defined first portion, a second portion of wastewater, formed from the wastewater that exceeds the defined first portion, is sent to a filtration process. The filtration process includes adding a flocculating agent to the second portion entering filtration, filtering the second portion, thereby producing retentive waste including flocculated material, and then sending the retentive waste to the submerged membrane filter.