Membrane Bioreactor Return Path Layout for Denitrification
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Solution Overview
Problem
Existing water treatment apparatuses using membrane bioreactors face inefficiencies due to the introduction of unnecessary dissolved oxygen into the anoxic tank, leading to uneven fouling and clogging of membranes, and require additional pumps for sludge return, increasing operating costs.
Innovation Solution
A water treatment apparatus with multiple rows of membrane separators and a return path installed below each row, covered by lids with openings at gaps, ensures efficient denitrification by minimizing dissolved oxygen introduction and maintaining aerobic treatment uniformity, eliminating the need for additional pumps.
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 fouling, then membrane fouling is suppressed, but unnecessary dissolved oxygen is brought into the anoxic tank through sludge return, reducing denitrification efficiency
Solution Approach 1:
The membrane separation tank is divided into multiple treatment sections with different dissolved oxygen concentration zones. The upstream region maintains DO at 1-2 mg/L for membrane protection, while the downstream region allows higher DO levels, preventing oxygen-rich sludge from returning to the anoxic tank and maintaining denitrification efficiency.
Solution Approach 2:
Different regions of the membrane separation tank are assigned different dissolved oxygen concentrations according to their functional requirements. The upstream region near membranes has controlled low DO to prevent fouling, while the downstream region has higher DO to ensure complete aerobic treatment, creating local quality variations that solve both problems.
2Device complexity
If membrane separators are arranged in a single-row arrangement, then the treatment tank structure is simple, but the apparatus occupies large space and has uneven fouling distribution
Solution Approach 1:
The membrane separators are rearranged from a single-row linear arrangement to a multi-row grid arrangement. This dimensional reconfiguration increases the membrane surface area within the same footprint, improves flow distribution uniformity, and reduces fouling concentration in any single region.
3Reliability
If air diffusion amount is increased toward the downstream side to prevent clogging, then clogging risk is reduced, but energy consumption increases
Solution Approach 1:
The air diffusion system is configured with location-specific air amounts matched to local requirements. The downstream region receives higher air diffusion to prevent clogging where MLSS concentration is highest, while the upstream region receives lower air amounts, optimizing energy consumption according to actual needs.
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
The apparatus achieves compact installation and efficient denitrification by reducing unnecessary oxygen introduction, preventing membrane fouling, and optimizing sludge return, thus enhancing treatment efficiency and reducing operational costs.
Implementation Method 1
a plurality of membrane separators (7) arranged in a multiple-row configuration... to perform solid-liquid separation
Implementation Method 2
an air diffuser provided below each membrane separator (7)... cleaning of the membrane surfaces is performed with oxygen supplied from the air diffuser
Implementation Method 3
aerobic treatment of the water to be treated... proceeds in the membrane separation tank (3)
Implementation Method 4
denitrification treatment in the anoxic tank (4)
Data Source
Figure 1
Figure 2A~2C
Figure 3A~3B
AI summary
Provided is a water treatment apparatus 1 including: an anoxic tank 4 configured to receive raw water; a treatment tank 3 having a plurality of membrane separators 7 immersed therein; an inflow path 5 configured to supply water to be treated from the anoxic tank 4 to the treatment tank 3; and a return path 6 configured to return the water to be treated from the treatment tank 3 to the anoxic tank 4. The membrane separators 7 are installed in a plurality of rows in the treatment tank 3. The return path 6 is installed so as to extend directly below and along each row of the membrane separators 7. Portions of the return path 6 corresponding to the respective membrane separators 7 arranged in each row are covered, and openings to receive the water to be treated are formed in portions of the return path 6 corresponding to respective gaps between the membrane separators 7.