How does polymer help settle solids? Using either coagulants or flocculants
A polymer, often referred to as a flocculant, aids in settling solids in a lamella clarifier by enhancing the aggregation of fine particles into larger flocs. When added to the influent, the polymer's long-chain molecules interact with suspended particles, causing them to bind together. This flocculation process creates larger, heavier aggregates that settle more rapidly due to gravity. In a lamella clarifier, which features inclined plates or tubes to increase the effective settling area, these larger flocs settle onto the surfaces of the plates and slide down into a collection zone. The use of polymers thus improves the efficiency of the clarifier by speeding up the settling process and enhancing the clarity of the treated water.
What Chemicals Are Used To Settle Solids in a Lamella Clarif
In the context of wastewater treatment, flocculants, polymers, and coagulants play crucial roles in the process of removing suspended solids and other impurities. Here are the key differences between them:
Coagulants
Definition: Coagulants are chemicals that are used to destabilize suspended particles in water, causing them to aggregate and form larger particles called flocs.
Mechanism: Coagulants neutralize the negative charges on the particles, reducing the repulsive forces between them. This allows the particles to come closer and form larger aggregates.
Common Types:
- Inorganic Coagulants: These include aluminum sulfate (alum), ferric chloride, and ferric sulfate.
- Organic Coagulants: These include polyamines and polyDADMACs.
Applications: Used in the initial stages of water and wastewater treatment to prepare the water for further treatment processes like sedimentation and filtration.
Flocculants
Definition: Flocculants are chemicals that promote the aggregation of already coagulated particles into larger flocs, which can then be more easily removed from the water.
Mechanism: Flocculants work by bridging the gaps between particles, helping them to clump together into larger masses that settle out of suspension.
Common Types:
- Natural Flocculants: Such as starches and polysaccharides.
- Synthetic Flocculants: Such as polyacrylamides.
Applications: Used after coagulation to further aggregate particles into larger flocs, enhancing the efficiency of sedimentation and filtration processes.
Polymers
Definition: Polymers are large molecules composed of repeating structural units. In water treatment, the term "polymer" typically refers to synthetic flocculants or coagulants.
Mechanism: Polymers can act as either coagulants or flocculants depending on their charge and molecular structure. They can help neutralize charges on particles (as coagulants) or link particles together to form larger aggregates (as flocculants).
Common Types:
- Cationic Polymers: Positively charged and often used as coagulants.
- Anionic Polymers: Negatively charged and often used as flocculants.
- Can be a liquid polymer or dry polymer
- Nonionic Polymers: Neutral charge and used in various applications depending on the specific needs of the treatment process.
Applications: Used throughout the water treatment process for both coagulation and flocculation, providing flexibility in treatment strategies. This includes industrial waste water treatment and lamella clarifiers.
Summary
- Coagulants: Used to destabilize particles and neutralize charges to initiate aggregation.
- Flocculants: Used to aggregate coagulated particles into larger flocs for easier removal.
- Polymers: Can act as either coagulants or flocculants, depending on their specific properties and applications.
Understanding these differences helps in selecting the appropriate chemical treatment strategy for effective water and wastewater treatment.
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