Macrofiltration Membrane Bioreactor for Wastewater Treatment
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Solution Overview
Problem
Conventional membrane bioreactors face challenges with high energy consumption and operational costs due to biofouling, limited permeate flux, and excessive sludge production, requiring frequent maintenance and larger footprints for wastewater treatment.
Innovation Solution
A wastewater treatment process utilizing a macrofiltration membrane module with pore sizes between 5 μm to 150 μm, an oxygen-surplus aeration zone, and an anaerobic zone for sulfate reduction, which minimizes sludge production and reduces biofouling by recycling mixed liquids and using sulfur compounds as electron acceptors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional microfiltration membranes with pore size of 0.1 μm to 1 μm are used in MBR process, then sludge separation is achieved, but permeate flux is limited to below 1 m3 per m2 of membrane per day
Solution Approach 1:
The patent changes the fundamental parameter of membrane pore size from conventional 0.1-1 μm to 5-150 μm macrofiltration range. This parameter change enables permeate flux to increase from below 1 m3/m2/day to above 10 m3/m2/day while maintaining effective sludge separation through the larger pore structure that allows higher flow rates without clogging
Solution Approach 2:
The patent segments the membrane filtration function into two stages: macrofiltration (5-150 μm pores) for bulk sludge separation and high flux, with fine filtration occurring naturally in the anaerobic zone through sulfate reduction. This segmentation allows each zone to optimize for its specific function rather than requiring the membrane to perform both fine filtration and high flux simultaneously
2Reliability
If frequent backwashing and chemical cleaning are performed to prevent biofouling, then membrane function is maintained, but energy consumption and operation cost increase
Solution Approach 1:
The patent applies preliminary action by pre-treating the wastewater through primary sedimentation and fine-screening before it enters the aeration tank, removing bulk solids and debris that would cause fouling. This preliminary removal reduces the burden on the membrane and anaerobic zone, decreasing the frequency and intensity of required cleaning operations
Solution Approach 2:
The anaerobic zone performs self-cleaning function through sulfate reduction, where sulfate-reducing bacteria consume organic matter and produce sulfide that precipitates with metals and inhibits fouling. This biological self-service mechanism reduces the need for external chemical cleaning and mechanical backwashing operations
3Productivity
If conventional activated sludge process is used, then organic carbon oxidation is achieved, but sludge production is excessive
Solution Approach 1:
The patent changes the electron acceptor parameter from oxygen (aerobic) to sulfate (anaerobic) in the second zone. This parameter change fundamentally alters the biological process: sulfate reduction produces sulfide instead of requiring oxygen consumption, resulting in significantly lower sludge production while maintaining organic matter removal efficiency
Solution Approach 2:
The patent merges the aeration zone (for organic oxidation and nitrification) with the anaerobic zone (for sulfate reduction and sludge minimization) into an integrated system. The mixed liquid flows from aeration to anaerobic zone, combining both processes to achieve both organic matter removal and sludge production minimization simultaneously
4Loss of substance
If OSA process with anaerobic sludge tank is added to reduce sludge production, then sludge production is minimized, but real estate footprint increases
Solution Approach 1:
The patent merges the anaerobic sludge tank function directly into the existing MBR structure by positioning the anaerobic zone adjacent to the aeration zone and using the same membrane system for both zones. This integration eliminates the need for separate anaerobic treatment facilities and reduces overall real estate footprint while maintaining sludge production minimization benefits
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 achieves a higher permeate flux, lower membrane fouling frequency, and reduced sludge production, resulting in a more efficient, compact, and cost-effective wastewater treatment system suitable for areas with limited land resources.
Implementation Method 1
uses a new category of membrane bioreactor... makes use of microfiltration membranes with typical pore size of 0.1 μm to 1 μm to separate the sludge from the mixed liquid
Implementation Method 2
using a suspended growth of biological floc, also known as sludge, composed of bacteria and protozoa processes to oxidize organic carbon in the wastewater
Implementation Method 3
sulfate reduction is used in an anaerobic zone to reduce excess sludge production
Data Source
AI summary
Wastewater influent is supplied to an aeration zone having a membrane module. Activated sludge is established in the aeration zone and an oxygen surplus is maintained by controlling a rate of oxygen supplied to the aeration zone. Wastewater influent is mixed with the activated sludge to form a first mixed liquid. A portion of the first mixed liquid is filtered to form a filtrate and unfiltered activated sludge. The unfiltered activated sludge is mixed with the activated sludge in the aeration zone to form the first mixed liquid. A portion of the first mixed liquid is transferred from the aeration zone to an anaerobic zone, and a second portion of first mixed liquid is mixed with activated sludge in the anaerobic zone to form a second mixed liquid. The second mixed liquid is recycled to the aerobic zone.