Differences Between DAF & Slant Plate Clarifiers

DAF (Dissolved Air Flotation) and slant plate clarifiers are both types of water treatment equipment used for solid-liquid separation, but they operate on different principles and are suitable for different applications.

The 4 main topics of discussion in this blog revolve around the principle of operation, application, performance, and maintenance of each type of clarifier.  This blog is intended to help you decide which clarifier you need for your specific application, however, when in doubt, it is best to consult with a J Mark specialist. 

Principle of Operation

DAF is a flotation process that uses the principle of buoyancy to separate solids from water. In DAF, fine air bubbles are introduced into the water, and these bubbles attach to the suspended solids, causing them to float to the surface. The floating solids form a layer of sludge, that makes it easier to remove.  A skimming mechanism, typically a mechanical scraper or similar device, is used to gently remove this froth layer, which contains the floated particles.

A slant plate clarifier, also known as an inclined plate settler, relies on gravity settling to remove suspended solids. It consists of inclined plates or tubes where solids settle under the influence of gravity. The settled solids slide down the plates or tubes into a collection hopper.  The settled solids form a sludge which is drawn off the bottom of the sludge chamber and flows to the sludge thickener for further dewatering.

Applicability

DAF clarifiers are particularly effective for the removal of fine and colloidal particles, oil and grease, and certain organic and inorganic pollutants. They are commonly used in wastewater treatment plants, industrial processes, and water treatment applications where there is a need for efficient removal of small and lightweight particles.

Slant plate clarifiers are suitable for removing larger and heavier solids from water. They are commonly used as a preliminary treatment step before other treatment processes, such as filtration or disinfection. Slant plate clarifiers are often used in municipal water and wastewater treatment, stormwater treatment, and some industrial applications.

The footprint of a slant plate clarifier is generally smaller compared to traditional clarifiers because of the inclined plates that provide a larger effective settling area within a compact space. The inclined plates increase the effective gravity settling area and allow for more efficient separation of solids. In general, slant plate clarifiers are favored for their ability to achieve high efficiency in solid-liquid separation while minimizing the space required for installation, making them suitable for applications where space is limited.

Performance

DAF systems can achieve a high level of solids removal.  They can effectively remove particles that are difficult to settle by gravity alone. A DAF is particularly useful for applications with variable influent characteristics. DAF systems often require the addition of chemicals to aid in coagulation and flocculation, enhancing the removal of smaller particles.

Slant plate clarifiers are generally less efficient in terms of solids removal compared to DAF systems. They are better suited for larger and more settling-prone particles. Depending on the application, slant plate clarifiers may also require the addition of coagulants and flocculants for optimal performance.

Operation and Maintenance

DAF systems require more operator attention and maintenance compared to slant plate clarifiers due to the need to control the air-to-water ratio and ensure proper flotation of solids. It is also important to regularly inspect and clean the skimmer blades and weirs to ensure proper removal of floated solids.  Formation of too many solids can interfere with the flotation process. Monitor sludge blanket levels and adjust the removal frequency accordingly.  As with most wastewater systems, it is important to conduct routine visual inspections of the entire DAF system to identify any signs of wear, corrosion, or damage.

Slant plate clarifiers are relatively low-maintenance systems, as they do not require the use of air or complex controls. The main maintenance tasks are periodic cleaning of the plates or tubes.

With both types of clarifiers, it is important to ensure that operators are trained in the proper operation and maintenance procedures for the specific system in use and to adhere to the manufacturer's guidelines and recommendations for maintenance practices, including recommended intervals for specific tasks.

In summary, DAF and slant plate clarifiers are both effective solid-liquid separation processes, but they are used for different types of particles and different applications. DAF is more suitable for the removal of fine particles and contaminants, while slant plate clarifiers are better suited for larger and heavier particles. The selection of the appropriate system depends on the specific water treatment objectives and the characteristics of the solids to be removed.

Call J.Mark Systems Today

Are you looking into a high-quality slant plate clarifier for your wastewater treatment? Look no further. J.Mark Systems has precisely what you need. Our systems come with every specification we recommended in this blog, which comes from years of experience providing high-quality water filtration systems for your industrial water supply.

We’ll walk you through every step of the process and get you the perfect slant plate clarifier for your system, from performing a water optimization audit to installing and monitoring your system. Contact J.Mark Systems today to get started or for more information.