Membrane Bioreactor Return Path Layout for Denitrification
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Solution Overview
Problem
Existing water treatment apparatuses using membrane bioreactors face issues with uneven fouling and clogging of membranes due to high dissolved oxygen concentrations and MLSS gradients, leading to inefficient denitrification treatment and increased operating costs.
Innovation Solution
The apparatus is configured with multiple rows of membrane separators, a return path extending below each row, and covered grooves or troughs to manage dissolved oxygen levels, ensuring efficient aerobic and anoxic treatments without hindering membrane cleaning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the dissolved oxygen concentration is adjusted to 1 to 2 mg/L in the membrane separation tank to suppress membrane fouling, then membrane fouling is reduced, but unnecessary dissolved oxygen is introduced into the anoxic tank through sludge return, reducing denitrification efficiency
Solution Approach 1:
The membrane separation tank is divided into multiple rows of membrane separators, with independent air diffusers for each row. This segmentation allows different dissolved oxygen concentrations to be maintained in different regions, enabling fouling suppression in the membrane region while maintaining anoxic conditions in the sludge return region.
Solution Approach 2:
Different dissolved oxygen concentrations are established in different locations within the membrane separation tank. The region near membrane separators maintains higher DO (1-2 mg/L) to suppress fouling, while the region where sludge is returned to the anoxic tank maintains lower DO levels to preserve denitrification efficiency.
2Productivity
If multiple rows of membrane separators are installed to increase treatment capacity, then productivity is improved, but device complexity and space requirements increase
Solution Approach 1:
Multiple rows of membrane separators are arranged side-by-side within a single membrane separation tank, merging multiple treatment functions into one integrated structure. This increases treatment capacity without proportionally increasing the number of separate tanks or complex interconnections.
Solution Approach 2:
The membrane separation tank serves multiple functions simultaneously: it performs membrane separation, provides aerobic treatment zones, enables sludge return, and facilitates denitrification in the anoxic tank. This multi-functionality increases productivity without requiring separate dedicated structures for each function.
3Reliability
If air diffusion is increased to clean membrane surfaces and prevent fouling, then membrane reliability is improved, but excessive oxygen is supplied to downstream regions, harming anoxic treatment
Solution Approach 1:
The harmful effect of excessive oxygen diffusion is eliminated by extracting or removing air diffusers from the downstream region of the membrane separation tank. Air diffusion is concentrated in upstream regions where it serves membrane cleaning purposes without interfering with anoxic treatment in the downstream sludge return zone.
Solution Approach 2:
Air diffusion is applied in advance in the upstream region to clean membrane surfaces before water flows to the downstream region. This preliminary cleaning action prevents fouling without causing excessive oxygen to reach the anoxic tank, as the diffusion is localized to where it is needed.
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 configuration reduces unnecessary oxygen introduction, promotes uniform treatment, and enhances the efficiency of denitrification, allowing for a compact design while minimizing membrane fouling and clogging.
Implementation Method 1
Air diffusers provided below the membrane separators to generate an upflow to clean the membrane surfaces
Implementation Method 2
multiple membrane separators immersed in a single-row arrangement along the longitudinal direction of the treatment tank
Implementation Method 3
aerobic treatment of the water to be treated as well as cleaning of the membrane surfaces is performed with oxygen supplied from the air diffuser
Implementation Method 4
denitrification treatment in the anoxic tank AX
Data Source
AI summary
A water treatment apparatus includes an anoxic tank configured to receive raw water, a treatment tank including a plurality of membrane separators immersed therein, an inflow path configured to supply water to be treated from the anoxic tank to the treatment tank, and a return path configured to return the water to be treated from the treatment tank to the anoxic tank. The membrane separators are arranged in a plurality of rows in the treatment tank. The return path extends directly below and along each row of the membrane separators. Portions of the return path corresponding to the respective membrane separators arranged in each row are covered, and openings to receive the water to be treated are provided in portions of the return path corresponding to respective gaps between the membrane separators.