Contact-Stabilization Hybrid Wastewater Treatment with DAF
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Solution Overview
Problem
Conventional wastewater treatment systems face inefficiencies in removing suspended solids and biological oxygen demand (BOD), leading to increased capital and operational costs, and require significant aeration and sludge disposal.
Innovation Solution
Incorporating a dissolved air flotation (DAF) unit between the contact tank and biological treatment unit to remove suspended solids and BOD before biological treatment, reducing the size of the biological treatment system and utilizing anaerobic digestion to recycle sludge and produce biogas for energy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional wastewater treatment systems use traditional biological treatment methods, then they can remove suspended solids and BOD, but they require large system size, significant aeration, and extensive sludge disposal
Solution Approach 1:
The dissolved air flotation (DAF) unit performs preliminary removal of suspended solids and BOD before the wastewater enters the biological treatment system. By pre-treating the wastewater to reduce solids concentration, the subsequent biological treatment requires smaller system volume and less aeration time, directly resolving the contradiction between treatment efficiency and system size
2Productivity
If conventional systems perform complete biological treatment of all suspended solids, then they achieve high removal efficiency, but they generate large amounts of sludge requiring disposal
Solution Approach 1:
The DAF unit extracts and removes a significant portion of suspended solids and BOD from the wastewater before biological treatment. By taking out these solids in the preliminary DAF stage, the remaining biological treatment processes less material, thereby reducing sludge production while maintaining overall removal efficiency
Solution Approach 2:
The system discards removed solids through the DAF unit's waste biosolids outlet, preventing them from entering the biological treatment system where they would contribute to sludge accumulation. This selective discarding approach reduces the total sludge burden on the system
3Reliability
If conventional systems use large aeration systems for biological treatment, then they achieve sufficient oxygen supply for microorganisms, but they incur high operational costs
Solution Approach 1:
The DAF unit performs preliminary removal of organic matter and suspended solids before aeration in the biological treatment system. By reducing the biodegradable organic load in advance, the microorganisms have less substrate to decompose, thereby reducing the oxygen demand and aeration energy requirements while maintaining reliable biological treatment performance
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
The DAF unit reduces the biological treatment system's size and aeration needs, decreasing capital and operational costs, while anaerobic digestion minimizes sludge production and generates energy from biogas, enhancing the system's efficiency and environmental sustainability.
Implementation Method 1
a gas inlet configured to introduce gas into the dissolved air flotation unit to facilitate the flotation of suspended matter from the first mixed liquor and the removal of the suspended matter from the dissolved air flotation unit
Implementation Method 2
separating the aerobic mixed liquor in the clarifier to form a clarified effluent and a return activated sludge
Implementation Method 3
mixing the wastewater with activated sludge in the contact tank to form a mixed liquor
Implementation Method 4
biologically treating the anoxic mixed liquor and the dissolved air flotation tank effluent in the aerobic treatment tank
Implementation Method 5
biologically treating the second portion of the mixed liquor in the aerated anoxic treatment tank to form an anoxic mixed liquor
Data Source
AI summary
Systems and methods for treating wastewater including a dissolved air flotation operation performed upon a portion of a mixed liquor output from a contact tank prior to the mixed liquor entering a biological treatment tank.