Activated Sludge Coagulation for COD Removal
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Solution Overview
Problem
Conventional wastewater treatment in the pulp and paper industry generates high volumes of inorganic sludge during tertiary treatment, leading to costly disposal issues and ash formation upon incineration, while also requiring significant investment in tertiary treatment facilities.
Innovation Solution
A method involving the addition of Al and/or Fe-based inorganic metal coagulants at a dosage of at least 10 moles per mole of soluble phosphate ion in the activated sludge process, combined with cationic polymer coagulants, to achieve simultaneous COD removal without the need for tertiary treatment, reducing sludge volume and ash content.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional coagulation-flocculation process with inorganic metal salts is used in tertiary treatment, then residual COD removal is achieved, but high amounts of inorganic sludge are generated requiring costly disposal
Solution Approach 1:
The invention combines the tertiary treatment coagulation step with the existing secondary clarification step by adding inorganic metal coagulant to the activated sludge process. This merging eliminates the need for separate tertiary treatment facilities and reduces sludge disposal requirements while maintaining COD removal efficiency.
Solution Approach 2:
The activated sludge process is made multi-functional by enabling it to perform both biological treatment and coagulation-flocculation functions simultaneously. The inorganic metal coagulant adds coagulation capability to the biological treatment system, allowing one process to achieve multiple treatment objectives.
2Quantity of substance
If sludge incineration is used to reduce sludge volume, then disposal space is reduced, but high amounts of ash formation occur requiring landfilling
Solution Approach 1:
The invention extracts the organic matter removal function from the sludge stream by enhancing COD removal in the liquid phase during activated sludge treatment. This extraction reduces the organic content in sludge before incineration, thereby reducing ash formation while maintaining volume reduction benefits.
3Reliability
If tertiary treatment facilities are constructed for hard COD removal, then effluent quality is improved, but high investments and large working areas are required
Solution Approach 1:
The invention merges the tertiary treatment function into the existing secondary clarification facility by adding coagulant dosage to the activated sludge process. This eliminates the need for separate tertiary treatment buildings and equipment, reducing capital investment and workspace requirements while achieving hard COD removal.
Solution Approach 2:
The existing secondary clarifier is made multi-functional to perform both activated sludge separation and coagulation-flocculation for hard COD removal. This universal use of existing infrastructure avoids the need for additional treatment facilities and reduces overall system complexity.
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 saves investment costs by eliminating the need for tertiary treatment facilities, efficiently removes biologically recalcitrant soluble organic compounds, and reduces sludge ash formation, while maintaining stable pH levels and effective COD removal.
Implementation Method 1
adding at least one Al and/or Fe based inorganic metal coagulant to the wastewater in the activated sludge process and/or prior to conveying wastewater to the activated sludge process
Implementation Method 2
the dosage of Al and/or Fe based inorganic metal coagulant is at least 10 moles of said metal ions per 1 mole of soluble phosphate ion in wastewater
Implementation Method 3
combined with cationic polymer coagulants, to achieve simultaneous COD removal
Implementation Method 4
combined with cationic polymer coagulants, to achieve simultaneous COD removal without the need for tertiary treatment
Implementation Method 5
The biological treatment is typically performed by using an aerobic biological process, whereby aerobic micro-organisms digest organic matter in wastewater, also called as an activated sludge process
Implementation Method 6
separating the activated sludge and the precipitated organic compounds from wastewater in the solid-liquid separation unit
Data Source
AI summary
A method for removing biologically recalcitrant soluble organic compounds from wastewater simultaneously in an activated sludge process comprising an aeration tank and a solid-liquid separation unit, in which method at least one Al and/or Fe based inorganic metal coagulant is added to the wastewater in the activated sludge process and/or prior to conveying wastewater to an activated sludge process.