Anaerobic Digester and Dissolved Air Flotation for Wastewater BOD Removal
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Solution Overview
Problem
Conventional wastewater treatment systems face inefficiencies in removing suspended solids and biological oxygen demand (BOD) without the need for extensive aeration, leading to increased capital and operational costs, and the generation of excessive waste sludge.
Innovation Solution
The integration of a dissolved air flotation (DAF) system that recycles solids back to the contact tank, combined with an anaerobic digester for sludge treatment, reduces the load on biological treatment units and enhances BOD removal, while utilizing anaerobic digestion to produce biogas for energy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional wastewater treatment systems use extensive aeration to remove suspended solids and BOD, then treatment effectiveness is improved, but capital and operational costs increase
Solution Approach 1:
The system segments the wastewater treatment process into distinct zones: an anaerobic digestion zone for initial BOD removal and a subsequent aerobic biological treatment zone. This segmentation allows each zone to operate optimally for its specific function, reducing the need for extensive aeration throughout the entire system while maintaining treatment effectiveness.
Solution Approach 2:
The anaerobic digestion process performs preliminary BOD removal before the wastewater enters the biological treatment unit. By pre-treating the wastewater to reduce BOD levels through anaerobic digestion, the subsequent aerobic treatment requires less energy-intensive aeration, thereby reducing operational costs while maintaining effective treatment.
2Reliability
If conventional systems treat all solids through aerobic biological treatment, then BOD removal is achieved, but waste sludge production increases
Solution Approach 1:
The treatment system is divided into an anaerobic digestion stage and an aerobic biological treatment stage. The anaerobic digestion stage handles a portion of the solids and BOD removal, producing less sludge compared to conventional aerobic treatment alone. This segmentation reduces overall waste sludge production while maintaining effective BOD removal through the combined action of both stages.
Solution Approach 2:
The system changes the operational parameters by implementing anaerobic conditions in the digestion zone, altering the biological treatment pathway. This parameter change from purely aerobic to anaerobic-aerobic combination reduces the biomass production associated with aerobic treatment, thereby decreasing waste sludge generation while achieving the same BOD removal objective.
3Reliability
If the system integrates anaerobic digestion with contact tank and DAF, then BOD removal efficiency is improved, but system complexity increases
Solution Approach 1:
The system merges the anaerobic digestion process with the conventional contact tank and dissolved air flotation (DAF) system. By integrating these processes, the system achieves enhanced BOD removal efficiency as the anaerobic digestion pre-treats the wastewater, reducing the load on subsequent treatment stages. The merging of functions allows for improved overall performance despite the increased number of process stages.
Solution Approach 2:
The biological treatment unit serves multiple functions: it completes BOD removal for wastewater that has undergone anaerobic digestion and also treats the effluent from the DAF system. This multi-functionality allows a single unit to handle multiple treatment objectives, improving BOD removal efficiency across different streams without requiring entirely separate treatment systems for each function.
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 reduces the size and operational costs of biological treatment units, decreases waste sludge production, and increases biogas production for energy, resulting in a more efficient and cost-effective wastewater treatment process.
Implementation Method 1
an anaerobic digester that digests or converts at least a portion of the solids or sludge from the sorption system
Implementation Method 2
treating water by a dissolved air flotation operation performed upon a portion of a mixed liquor output from a contact tank
Data Source
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AI summary
A wastewater treatment system includes a contact tank having a first inlet configured to receive wastewater to be treated, a second inlet configured to receive activated sludge, and an outlet, a dissolved air flotation unit having an inlet in fluid communication with the outlet of the contact tank, a biological treatment unit having a first inlet in fluid communication with an effluent outlet of the dissolved air flotation unit and an outlet, an anaerobic digester having an inlet and an outlet, a floated solids conduit providing fluid communication between the solids outlet of the dissolved air flotation unit and the inlet of the anaerobic digester, and a thickener having an inlet in fluid communication with the outlet of the anaerobic digester, a first outlet in fluid communication with the inlet of the anaerobic digester, and a second outlet.