Reduce High Turbidity in Water Treatment: DAF Systems vs. Disk Filters

Managing high turbidity in water treatment is a significant challenge. High levels of turbidity, caused by suspended particles, can negatively impact water quality and treatment processes. When dealing with influent turbidity of 100 NTU, choosing the right technology to reduce it effectively is crucial. Here’s a closer look at Dissolved Air Flotation (DAF) systems, disk filters, and other potential techniques.

Dissolved Air Flotation (DAF) Systems :

DAF systems are highly effective for treating water with high turbidity levels. The process involves dissolving air in water under pressure and then releasing it into a flotation tank at atmospheric pressure. This creates tiny bubbles that attach to suspended particles, causing them to rise to the surface for removal. DAF systems can handle very high turbidity levels, efficiently reducing them to below 10 NTU.

How DAF Systems Work:

1. Air Saturation Tank: Air is dissolved in water under high pressure.

2. Flotation Tank: The pressurized air is released, forming bubbles that lift particles to the surface.

3. Scraper Mechanism: Removes the floated sludge from the surface.

4. Recycle Flow Pump: Recirculates part of the treated water to optimize the flotation process.

5. Chemical Addition: Coagulants and flocculants enhance particle aggregation and flotation efficiency.

Applications of DAF Systems:

- Municipal Water Treatment: Ensuring clean, safe drinking water.

- Industrial Wastewater Treatment: Managing complex effluents.

- Food and Beverage Industry: Maintaining high hygiene standards.

- Oil and Gas Industry: Treating heavily contaminated water.

Advantages of DAF Systems:

- High Efficiency: Handles influent turbidity levels up to 1,000 NTU or more.

- Versatility: Suitable for a wide range of contaminants.

- Compact Design: Requires less space compared to other treatment methods.

- High Sludge Concentration: Produces sludge with a high solids concentration, reducing disposal costs.

Leading Companies in DAF Technology:

- Evoqua Water Technologies: Known for robust and versatile DAF systems.

- HydroFloTech: Offers modular units for easy installation.

- WesTech Engineering: Provides tailored solutions for municipal and industrial applications.

- KWI Group: Focuses on advanced and efficient DAF technology.

Disk Filters :

Disk filters are another effective solution for reducing turbidity, especially for secondary or tertiary treatment. They work by passing water through a series of stacked disks covered with fine filtration media. These disks trap particles, reducing turbidity. Disk filters are more suited for applications where the initial turbidity is lower, generally up to 50 NTU.

How Disk Filters Work:

1. Filter Disks: Stacked disks with fine filtration surfaces trap particles.

2. Backwash System: Periodically cleans the disks to maintain filtration efficiency.

3. Frame and Housing: Holds the disks in place and directs water flow.

4. Drive Mechanism: Rotates the disks for cleaning and operation.

5. Filtration Media: Varies in porosity to trap different sizes of particles.

Applications of Disk Filters:

- Tertiary Treatment in Municipal Wastewater: Ensuring final water quality.

- Industrial Process Water: Maintaining process integrity.

- Irrigation Systems: Preventing clogging and ensuring efficient water use.

- Cooling Towers: Keeping systems clean and efficient.

Advantages of Disk Filters:

- High Filtration Efficiency: Excellent for polishing and fine filtration.

- Low Maintenance: Easy to maintain with automated backwashing systems.

- Continuous Operation: Operates without significant flow interruption.

- Compact Design: Takes up less space.

- Scalability: Easily scalable to meet varying flow rates and treatment requirements.

Leading Companies in Disk Filter Technology:

- Amiad Water Systems: Known for reliable and durable disk filters.

- Arkal Filtration Systems (Amiad division): Specializes in agricultural and industrial applications.

- Eaton Filtration: Provides advanced solutions for industrial and municipal needs.

- Filternox: Offers self-cleaning disk filters for high efficiency.

Other Techniques for Turbidity Reduction :

In addition to DAF systems and disk filters, other methods can be considered for reducing turbidity:

1. Sand Filtration:

- Overview: Uses sand as a filter media to remove suspended solids.

- Advantages: Simple operation, cost-effective for moderate turbidity levels.

- Applications: Commonly used in drinking water treatment and as pre-treatment for other filtration systems.

2. Ultrafiltration (UF):

- Overview: Utilizes semi-permeable membranes to remove particles and pathogens.

- Advantages: High removal efficiency for turbidity, bacteria, and viruses.

- Applications: Drinking water treatment, industrial process water, and wastewater reclamation.

3. Microfiltration (MF):

- Overview: Similar to UF but with larger pore sizes, effective for turbidity and some pathogens.

- Advantages: High flow rates, effective for polishing and pre-treatment.

- Applications: Drinking water treatment, pre-treatment for reverse osmosis (RO) systems.

4. Coagulation and Flocculation:

- Overview: Chemical process that involves adding coagulants to aggregate particles into larger flocs, which can then be removed.

- Advantages: Effective for high turbidity and color removal, enhances downstream filtration processes.

- Applications: Municipal and industrial water treatment, pre-treatment for filtration systems.

Choosing the Right Solution :

When the goal is to reduce turbidity from 100 NTU to less than 10 NTU, DAF systems often stand out due to their ability to handle high initial turbidity levels efficiently. However, combining a DAF system with disk filters or other polishing filtration methods can further enhance water quality, ensuring the treated water meets the highest standards.

By understanding the strengths and applications of DAF systems, disk filters, and other available techniques, water treatment professionals can design and implement systems that ensure optimal performance and water quality.

In some cases, using a combination of these technologies can provide the best results. For example, a DAF system might be used initially to handle the bulk of the turbidity reduction, followed by a disk filter for fine polishing. This multi-stage approach can ensure that the water meets stringent quality standards efficiently and effectively.

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Ahmed Khaled

Water and Wastewater Treatment Engineer

Specialist in Reverse Osmosis and Advanced Filtration Technologies

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