Rotating Disc Wastewater Treatment with Variable Speed Biofilm Control
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Solution Overview
Problem
Existing biological disc treatment systems for urban and industrial wastewater face inefficiencies in oxygenation, biofilm thickness control, and nitrogen treatment due to limited oxygenation capacity and difficulty in maintaining a thin biofilm, which restricts their use in initial and tertiary treatment stages.
Innovation Solution
The system features vertically mounted, horizontally rotated discs with undulating linings that increase surface area towards the outside, allowing better oxygenation and biofilm distribution, along with a speed variator to modulate rotation speeds for optimized biofilm thickness and treatment stages, enhancing nitrogen removal through nitrification and denitrification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the discs rotate at high speed to improve oxygenation, then oxygen transfer to biomass is enhanced, but the biofilm becomes too thin and is eroded excessively
Solution Approach 1:
The system alternates between high rotation speeds for oxygenation and low rotation speeds for biofilm maintenance and denitrification. The control unit modulates the rotation speed periodically, switching between high speed (for oxygen transfer) and low speed (for biofilm stability and anoxic conditions), thereby resolving the contradiction between oxygenation efficiency and biofilm stability
Solution Approach 2:
The control unit dynamically adjusts the rotation speed parameter based on treatment stage requirements. By changing the rotation speed from high to low values, the system optimizes both oxygenation during high-speed phases and biofilm stability during low-speed phases, resolving the technical contradiction
2Quantity of substance
If the rotation speed is kept low to maintain thick biofilm, then biomass quantity is preserved, but oxygenation capacity is insufficient
Solution Approach 1:
The system implements periodic alternation between low rotation speeds (for biomass preservation) and high rotation speeds (for oxygenation). During low-speed phases, biomass accumulates and stabilizes; during high-speed phases, oxygen transfer is maximized. This periodic cycling resolves the contradiction between biomass quantity and oxygenation capacity
3Productivity
If the discs rotate continuously at high speed for carbon treatment, then oxygenation is maximized, but nitrogen removal through denitrification is prevented
Solution Approach 1:
The control unit implements periodic alternation between high rotation speeds (for carbon treatment and oxygenation) and low rotation speeds (for denitrification). During high-speed phases, carbon pollution is treated efficiently; during low-speed phases, anoxic conditions enable nitrogen removal. This resolves the contradiction between carbon treatment productivity and nitrogen treatment capability
Solution Approach 2:
The system dynamically changes the rotation speed parameter to switch between carbon treatment mode (high speed) and nitrogen removal mode (low speed). This parameter modulation enables the system to perform both carbon and nitrogen treatment effectively, resolving the contradiction between productivity and adaptability
4Ease of manufacture
If the lining has uniform surface area distribution, then manufacturing is simplified, but treatment efficiency is reduced due to poor oxygenation at the center
Solution Approach 1:
The lining is designed with non-uniform surface area distribution, where the surface area per unit radius increases with distance from the rotation axis. This local variation in surface area ensures that outer regions (which experience higher linear speeds and better oxygenation) have greater surface area, optimizing the overall treatment efficiency while maintaining a relatively simple manufacturing process
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 improves oxygenation and biofilm control, enabling effective carbon and nitrogen treatment, particularly by maintaining a thin biofilm for aerobic conditions and adjusting speeds for efficient denitrification, thus optimizing treatment performance across different stages.
Implementation Method 1
rotated so that the biomass which develops on the surface of the lining of the discs is alternately brought into contact with the water to be treated and the oxygen in the air by trickling effect
Implementation Method 2
the configuration of the lining of the discs being chosen so that the developed surface of the lining in a zone of the disc increases with the distance of this zone from the axis of rotation
Implementation Method 3
A faster speed accelerates runoff and erosion and therefore reduces the thickness of the biofilm
Implementation Method 4
enhancing nitrogen removal through nitrification and denitrification
Implementation Method 5
A slower speed reduces runoff and erosion and therefore maintains a greater thickness of the biofilm. This reduction in speed over a relatively long time (several tens of minutes) will lead, to a certain extent, to a significant reduction in the oxygenation of the medium while maintaining contact between the biomass and the substrate. This results in an anoxic period which ensures elimination of nitrate nitrogen by biological denitrification
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
Installation for the treatment of municipal and/or industrial wastewaters comprising a basin that receives the water to be treated and a series of discs (4) having a packing (G) that are parallel and vertical, mounted on a horizontal shaft (5), partially submerged in the water to be treated, and rotated so that the biomass which grows on the surface of the packing of the discs is alternately brought into contact with the water to be treated and oxygen from the air. The configuration of the packing (G) of the discs (4) is chosen so that the developed surface area of the packing in one zone of the disc increases with the distance from this zone to the axis of rotation (X‑X).