Hybrid MABR Activated Sludge Ammonia Breakthrough Control
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Solution Overview
Problem
In hybrid MABR/AS systems, the concentration of ammonia-oxidizing bacteria (AOB) in aerobic mixed liquor is lower than in conventional AS systems, leading to potential ammonia breakthrough in system effluent, especially during fluctuations in ammonia loading, which can exceed discharge limits.
Innovation Solution
Modulating the supply of oxygen to the membrane aerated biofilm based on ammonia loading, reducing oxygen during periods of low loading to support AOB growth and increasing oxygen during high loading to enhance ammonia oxidation capacity, while maintaining a robust biofilm population.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If oxygen supply to membrane aerated biofilm is increased to enhance ammonia oxidation capacity, then ammonia removal efficiency is improved, but AOB population in aerobic mixed liquor decreases
Solution Approach 1:
The system dynamically adjusts oxygen supply to the membrane aerated biofilm based on real-time ammonia loading conditions. During high ammonia loading periods, oxygen supply is increased to maximize ammonia oxidation capacity. During low ammonia loading periods, oxygen supply is reduced to allow AOB population in aerobic mixed liquor to recover and grow, ensuring sufficient polishing capacity when loading increases again.
Solution Approach 2:
The system changes the oxygen supply parameter to the membrane aerated biofilm in response to varying ammonia loading conditions. By modulating this parameter between high and low levels, the system optimizes both ammonia oxidation capacity and AOB population maintenance, resolving the contradiction between productivity and biomass quantity.
2Quantity of substance
If oxygen supply to membrane aerated biofilm is reduced to support AOB growth in aerobic mixed liquor, then AOB population is improved, but ammonia oxidation capacity decreases
Solution Approach 1:
The system implements periodic modulation of oxygen supply to the membrane aerated biofilm. During periods of low ammonia loading, oxygen supply is reduced to support AOB growth in aerobic mixed liquor. During periods of high ammonia loading, oxygen supply is increased to maximize ammonia oxidation capacity. This periodic action allows the system to alternate between building biomass and utilizing biomass for high-rate ammonia removal.
3Stability of the object's composition
If constant oxygen supply is maintained to membrane aerated biofilm, then ammonia oxidation capacity is stable, but system cannot respond to rapid ammonia loading changes
Solution Approach 1:
The system employs feedback control by monitoring ammonia loading conditions and adjusting oxygen supply to the membrane aerated biofilm accordingly. When ammonia loading increases, the system responds by increasing oxygen supply to maximize oxidation capacity. When ammonia loading decreases, the system reduces oxygen supply to maintain AOB population. This feedback mechanism provides both stability through adequate oxidation capacity and adaptability to loading fluctuations.
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 approach maintains a sufficient population of AOB in both the membrane aerated biofilm and aerobic mixed liquor, effectively preventing ammonia breakthrough and ensuring compliance with effluent ammonia limits by optimizing oxygen supply in response to varying ammonia loading conditions.
Implementation Method 1
Air is supplied to the module and travels through a lumen of the gas transfer membrane. A membrane aerated biofilm forms attached to the outside of the cords and receives oxygen through the gas transfer membrane.
Implementation Method 2
receives oxygen through the gas transfer membrane
Implementation Method 3
oxidation (i.e. ammonia oxidation such as nitrification) can occur in the membrane aerated biofilm and in the suspended biomass of the mixed liquor
Data Source
AI summary
A hybrid membrane aerated biofilm reactor (MABR) and activated sludge (AS) system and process are described herein. At least a portion of the AS system includes aerobic mixed liquor, for example in an aerobic tank or zone downstream of a tank or zone containing membrane aerated biofilm modules. The flow of air to the membrane aerated biofilm is modulated considering the ammonia loading rate to the system or to the aerobic mixed liquor, for example according to a diurnal cycle. For example, air flow to the membrane supported biofilm can be below an average or initial air flow rate during a period of low ammonia loading. Air flow to the aerobic mixed liquor may remain essentially constants during the same period. Optionally, mixed liquor around the membrane aerated biofilm modules may be aerated during a period of high ammonia loading.