Wastewater Treatment with Coagulant-Enhanced Sludge Settleability
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Solution Overview
Problem
Conventional wastewater treatment methods using the activated sludge process face challenges such as high excess sludge generation, difficulty in sludge separation, and the need for large treatment tank volumes, leading to increased operational costs and inefficiencies.
Innovation Solution
A wastewater treatment method involving an aeration step with a microorganism-immobilized carrier, a total oxidization step with a coagulant addition to improve sludge settleability, and a sedimentation step, allowing for a balanced sludge growth and oxidation rate, thereby minimizing excess sludge generation and reducing tank sizes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the BOD volume load is increased to 2 to 5 kg/m³.day to compact the aeration tank, then the tank size is reduced, but the treatment becomes insufficient and sludge settleability decreases
Solution Approach 1:
The system divides the aeration process into two distinct segments: an aerobic aeration tank for BOD removal and a separate anaerobic digester for sludge stabilization. This segmentation allows each tank to operate under optimized conditions - the aeration tank can run at high loading rates while the digester handles sludge volume reduction, resolving the contradiction between compact size and stable operation.
Solution Approach 2:
The anaerobic digester acts as an intermediary component between the aeration tank and the effluent discharge. It receives excess sludge from the aeration tank, stabilizes it through anaerobic digestion, and returns the digested sludge to the aeration tank, thereby maintaining system stability while allowing high loading rates in the aeration tank.
2Loss of substance
If a totally oxidized condition is established to eliminate excess sludge generation, then sludge withdrawal is reduced, but MLSS increases considerably requiring a larger tank
Solution Approach 1:
The system changes the operational parameters by introducing an anaerobic environment in the digester, contrasting with the aerobic aeration tank. This parameter change allows sludge to be stabilized without complete oxidation, maintaining lower MLSS levels in the aeration tank while still reducing excess sludge generation through the anaerobic digestion process.
Solution Approach 2:
The system extracts the sludge stabilization function from the aeration tank by introducing a separate anaerobic digester. This extraction allows the aeration tank to focus on BOD removal at high loading rates while the digester handles sludge volume reduction, preventing the need to increase aeration tank size for total oxidation.
3Ease of operation
If a coagulant is added to the aeration tank to improve sludge sedimentation, then sludge separation is enhanced, but aeration efficiency decreases due to sludge sedimentation
Solution Approach 1:
The anaerobic digester serves as an intermediary that receives sludge from the aeration tank and performs stabilization without interfering with the aeration process. This allows coagulants to be added in the digester rather than the aeration tank, improving sludge separation without compromising aeration efficiency.
Solution Approach 2:
The system segments the sludge treatment process into aerobic treatment in the aeration tank and anaerobic stabilization in the digester. Coagulants are applied in the digester phase where they enhance sludge separation without interfering with the aerobic aeration process, thus maintaining aeration efficiency while improving sludge separation.
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 enables efficient wastewater treatment with reduced excess sludge withdrawal, compact tank designs, and lower operational costs by balancing sludge growth and oxidation rates, enhancing sludge separation and maintaining coagulant effectiveness over time.
Implementation Method 1
a coagulant is added to the total oxidization tank
Implementation Method 2
a sedimentation step of sedimenting the sludge within a sedimentation tank
Implementation Method 3
contacting wastewater with a microorganism-immobilized carrier under an aerobic condition within an aeration tank
Implementation Method 4
self-oxidizing a sludge under an aerobic condition within a total oxidization tank
Data Source
AI summary
A method of wastewater treatment that reduced equipment cost and running cost and realizes high efficiency implementation and further tank miniaturization, and that reduces excess sludge withdrawal. There is provided a method of wastewater treatment with excess sludge withdrawal reduced, characterized in that there are installed an aeration tank wherein wastewater is brought into contact with carrier particles under aerobic conditions, a total oxidization tank and a sedimentation tank, and that operation is made while maintaining the BOD sludge load in the total oxidization tank at 0.08 kg-BOD/Kg-MLSS*day or smaller, and that a coagulant is charged in the complete oxidization tank in order to improve the setting in the sedimentation tank.