Compartmentalized Selector Tank for Wastewater Reactor Cost Reduction
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Solution Overview
Problem
Current sequential biological reactors for wastewater treatment have high construction costs due to complex selector designs, which complicate installation and increase costs, especially for small and medium-sized installations, and face hydraulic constraints that require significant structural oversizing and thick walls.
Innovation Solution
The reactor features a compartmentalized selector tank with alternating high and low outlets between sectors, a cylindrical shape with vertical generatrices, and partitions that frame the top outlet, allowing for a reduced volume and minimizing dead zones, thus reducing the need for thick walls and simplifying the structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a complex selector design with multiple hydraulic constraints is used, then hydraulic efficiency is improved, but construction cost and structural complexity increase
Solution Approach 1:
The selector is divided into multiple compartments (typically three) separated by vertical baffles. Each compartment handles specific hydraulic functions: the first receives raw water, the second receives recirculated sludge, and the third is the overflow zone. This segmentation allows independent optimization of each zone while maintaining overall hydraulic efficiency, reducing the need for complex integrated structures.
Solution Approach 2:
The invention introduces a vertical dimension to the selector design by creating stacked compartments with controlled water levels. The recirculated sludge is introduced at a lower level than the raw water inlet, creating vertical stratification. This dimensional approach allows hydraulic functions to be separated in the vertical axis rather than requiring complex horizontal arrangements, reducing structural complexity.
2Strength
If thick walls and oversizing are used to meet hydraulic constraints, then structural strength is improved, but construction cost increases
Solution Approach 1:
By segmenting the selector into compartments with internal baffles, the structural loads are distributed across multiple smaller elements rather than requiring a single large thick-walled structure. Each baffle and compartment wall can be thinner and more easily manufactured, while the cumulative structural strength meets the hydraulic constraints.
Solution Approach 2:
The design applies structural reinforcement locally only where needed - at the bases of vertical baffles and at connection points for inlet/outlet structures. The majority of the selector walls can be thinner since they don't bear the full hydraulic load, reducing overall material consumption and construction cost while maintaining necessary strength at critical locations.
3Ease of manufacture
If a simplified selector design is used, then construction cost is reduced, but hydraulic efficiency and sludge control deteriorate
Solution Approach 1:
The compartmentalized design provides simple, modular construction with standardized baffles and walls, reducing manufacturing complexity and cost. Meanwhile, each compartment's specific function (mixing, settling, overflow) ensures that sludge settling performance is maintained through straightforward hydraulic separation rather than complex mechanical systems.
Solution Approach 2:
The selector design uses the incoming raw water flow itself to drive the hydraulic circulation and sludge separation processes. The recirculated sludge is introduced and mixed passively through the compartment geometry and water level differences, without requiring additional mechanical mixers or pumps. This self-service approach maintains reliable sludge control while minimizing mechanical complexity and construction cost.
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 design reduces construction costs by allowing for thinner walls and faster production, while maintaining hydraulic efficiency and preventing sludge resuspension during settling phases, resulting in improved water quality and reduced operational complexity.
Implementation Method 1
The effluent to be treated is brought into contact with the recirculated part 5a of the sludge coming from the basin 1a. The biological treatment of the effluent takes place mainly during the reaction phase: elimination of carbon and nitrification of ammoniacal nitrogen during the aeration period, denitrification during the possible anoxia period.
Implementation Method 2
Filling, aeration and/or mixing of the effluent in basin 1a are then stopped for a predetermined period. It is during this period that takes place, in purely static settling, the separation of the treated water from the sludge.
Data Source
Figure 1~2
Figure 3~6
AI summary
Sequential biological reactor (R), comprising: a tank (1) delimited by a base and peripheral walls (3); an inlet (11) equipped with a selector (S) that determines a baffled route with contacting of the effluent to be treated and a portion (5) of the recirculated sludges; a means (6) for discharging the treated water in the top part of the water surface of the tank, and an outlet (7) for discharging the excess sludges in the bottom of the tank. The selector (S) comprises a vessel (8) placed in the tank (1) at a distance from the peripheral walls (3); the vessel is compartmentalized into several sectors (8.1, 8.2, 8.3, 8.4), the outlet from one sector, which is also the inlet of the following sector, being alternately low and high, or vice versa, and a last step is defined by a chamber (13) formed by two partitions (14, 15) that extend between the wall of the vessel (8) and the peripheral walls (3) of the tank and that surround the top outlet (12) of the last sector of the vessel, the lower edge of the partitions being at a distance from the base and determining two low openings for passage of the effluent into the tank.