Aeration Control Using FIFO Delay Compensation
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Solution Overview
Problem
Current methods for controlling aeration in wastewater treatment plants struggle to precisely adjust air supply to match varying loads of nitrogen compounds and organic substances, leading to inefficient energy consumption and potential exceedance of outlet threshold values.
Innovation Solution
A method using a control unit that determines a reference variable by sequentially saving values of a measurand in a FIFO memory, allowing only the n oldest values to be used, thereby simulating the transport of liquid volume units and providing a nominal value for air mass flow adjustment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If air supply is increased to match varying loads of nitrogen compounds and organic substances, then treatment effectiveness is improved, but energy consumption increases
Solution Approach 1:
The control unit calculates future air mass flow requirements in advance based on measured liquid flow rates and nitrogen compound loads, storing these calculated values in a memory buffer. This preliminary calculation allows the system to prepare appropriate air supply levels before the actual treatment need arises, matching aeration to varying loads efficiently without excessive energy consumption.
Solution Approach 2:
The system continuously measures liquid flow rates and nitrogen compound loads, feeds this information back to the control unit, which then adjusts air mass flow calculations accordingly. This closed-loop feedback mechanism ensures treatment effectiveness is maintained while avoiding unnecessary aeration and energy waste.
2Use of energy by moving object
If air supply is decreased to reduce energy consumption, then energy efficiency is improved, but outlet threshold values may be exceeded
Solution Approach 1:
The control unit performs preliminary calculations of required air mass flow based on measured parameters and stores calculated values in a memory buffer with a defined retention time. This advance preparation ensures that when treatment needs arise, the appropriate air supply is already calculated and ready, preventing threshold exceedances while maintaining energy efficiency.
Solution Approach 2:
The system dynamically adjusts air mass flow calculations based on varying liquid flow rates and nitrogen compound loads. The control unit modifies the calculated air requirements in real-time according to actual process conditions, ensuring outlet threshold compliance while optimizing energy consumption through adaptive rather than static control.
3Reliability
If continuous aeration is applied to ensure sufficient oxygen supply, then degradation of nitrogen compounds is improved, but energy waste occurs during low load periods
Solution Approach 1:
Instead of continuous aeration, the system applies periodic or variable aeration based on calculated air mass flow requirements. The control unit determines when aeration is actually needed based on measured nitrogen compound loads and liquid flow rates, activating aeration only during periods when degradation is required rather than operating continuously, thus eliminating energy waste during low load periods.
Solution Approach 2:
The system changes aeration parameters (air mass flow rate, timing) based on process conditions. The control unit adjusts aeration intensity and duration according to varying nitrogen compound loads and liquid flow rates, transitioning from fixed continuous aeration to variable parameter control that matches actual treatment needs and reduces energy waste.
4Measurement precision
If aeration is adjusted based on real-time nitrogen compound measurements, then control precision is improved, but response delay occurs due to liquid transport time
Solution Approach 1:
The control unit performs preliminary calculations of air mass flow requirements based on currently measured nitrogen compound loads and liquid flow rates. By calculating future aeration needs in advance and storing these values in a memory buffer, the system compensates for liquid transport time delays, ensuring that aeration adjustments are already prepared when the treated liquid reaches the outlet.
Solution Approach 2:
The system dynamically adjusts the timing and magnitude of aeration based on measured parameters and calculated requirements. The control unit modifies aeration commands in real-time according to varying process conditions, maintaining control precision despite transport delays through adaptive rather than fixed timing adjustments.
Data Source
AI summary
A method to control a process variable in a process using a control unit includes sequential determination of values of a reference variable to be supplied to the control unit based on values of a first measurand, and sequential determination of values of a regulating variable using values for the reference variable and sequentially determined values for the process variable. A current value for the reference variable is determined by sequentially saving values of the first measurand in a first FIFO memory having a number K of memory locations for saving one value respectively, and by using only the n oldest values saved in the first FIFO memory to determine the current value for the reference variable, with n being a number of values that is smaller than the number K of the values saved in the memory locations of the first FIFO memory and greater or equal 1.