IFAS Deammonification Reactor Bypass for NOB Control
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Solution Overview
Problem
Mainstream deammonification processes face challenges in controlling nitrite oxidizing bacteria (NOB) growth, maintaining adequate residual ammonium levels, and addressing sludge bulking, which affects the efficiency and settling characteristics of sludge in wastewater treatment.
Innovation Solution
A mainstream deammonification process utilizing an Integrated Fixed Film Activated Sludge (IFAS) reactor with intermittent aeration, where carbon-rich primary effluent is bypassed into the reactor during air-off periods, and anoxic conditions promote the selection of non-filamentous organisms, maintaining nitrite availability for anammox bacteria and controlling NOB growth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional nitrification and denitrification processes are used to remove ammonium, then ammonium removal is achieved, but substantial energy is required for oxygen generation and external carbon sources are often needed
Solution Approach 1:
The process changes the chemical parameters by using deammonification instead of conventional nitrification-denitrification. This involves maintaining specific dissolved oxygen concentrations (0.2-0.8 mg/L) and controlling the C/N ratio (0.25-0.75) to enable anammox bacteria to convert ammonium and nitrite to nitrogen gas, significantly reducing energy consumption for aeration and eliminating the need for external carbon sources
Solution Approach 2:
The process replicates the natural deammonification pathway found in anaerobic sludge digester dewatering liquid treatment, applying it to mainstream wastewater treatment. By copying the successful sidestream deammonification approach and adapting it for mainstream application through controlled intermittent aeration and carbon supplementation, the system achieves energy-efficient ammonium removal
2Use of energy by moving object
If mainstream deammonification process is implemented to reduce energy consumption, then energy efficiency is improved, but controlling nitrite oxidizing bacteria growth and maintaining adequate residual ammonium becomes difficult
Solution Approach 1:
The process uses periodic intermittent aeration cycles alternating between aerobic and anoxic periods. During aerobic periods, AOB convert ammonium to nitrite while NOB are suppressed due to limited oxygen availability. During anoxic periods, anammox bacteria convert remaining ammonium and nitrite to nitrogen gas. This periodic action simplifies control by automatically creating the necessary conditions for each bacterial group without requiring continuous manual adjustment
Solution Approach 2:
The process incorporates feedback control through monitoring dissolved oxygen concentrations and adjusting aeration accordingly. Dissolved oxygen sensors provide real-time feedback to control the aeration system, maintaining DO within the optimal range (0.2-0.8 mg/L) that favors AOB while suppressing NOB. This feedback mechanism automates the control of residual ammonium levels and nitrite availability
3Use of energy by moving object
If deammonification process is used to improve energy efficiency, then energy consumption is reduced, but sludge bulking occurs affecting settling characteristics
Solution Approach 1:
The process creates different local conditions within the reactor by implementing spatial and temporal variation in aeration. Different zones experience different oxygen levels and carbon availability at different times, promoting the growth of floc-forming bacteria in specific locations while suppressing filamentous organisms. The localized supplementation of carbon-rich primary effluent during anoxic periods creates favorable conditions for non-filamentous organisms in specific reactor zones
Solution Approach 2:
The process changes operational parameters including dissolved oxygen concentration (maintained at 0.2-0.8 mg/L), C/N ratio (controlled at 0.25-0.75), and aeration timing to prevent sludge bulking. These parameter changes create an environment that favors the growth of floc-forming bacteria over filamentous organisms, improving sludge settling characteristics while maintaining energy efficiency
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 effectively suppresses NOB growth, improves sludge settling characteristics, and maintains adequate residual ammonium levels, enhancing the overall efficiency of ammonium removal and nitrogen reduction in wastewater treatment.
Implementation Method 1
In the nitritation step, aerobic oxidizing bacteria (AOB) oxidize a substantial portion of the ammonium in the waste stream to nitrite (N02)
Implementation Method 2
Then in the second step, the anammox bacteria or biomass converts the remaining ammonium and the nitrite to nitrogen gas (N2)
Implementation Method 3
the IFAS deammonification reactor with intermittent aeration
Implementation Method 4
carbon-rich primary effluent is bypassed into the reactor during air-off periods
Data Source
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AI summary
The present invention relates to a mainstream deammonification process for removing ammonium from wastewater that suppresses NOB growth and produces a sludge having good settling characteristics, the process comprising: clarifying the wastewater stream in a primary clarifier (12) and producing a primary effluent; directing a first portion of the primary effluent to a biological treatment reactor (14) and removing carbon to produce treated wastewater; directing treated wastewater into an integrated fixed film activated sludge (IFAS) deammonification reactor (16) integrating nitritation and anammox processes and that is provided with intermittent aeration; directing a second portion of the primary effluent to the IFAS deammonification reactor (16) by-passing the biological treatment reactor (14), and injecting this second portion only during periods of air off and refraining from injecting during periods of air on, directing the IFAS deammonification reactor (16) effluent to a secondary clarifier (18) and producing a secondary effluent and a clarifier underflow, and recycling at least a portion of the underflow to the IFAS deammonification reactor (16).