What You Need to Know About the Clarification Process in Water Treatment

September 21, 2021

Treating wastewater is a difficult job, requiring primary, secondary and ballasted clarification to remove suspended solids. Responsible wastewater companies follow this process to meet all treatment requirements and ensure the safe handling of wastewater. If you’re looking for the right clarification system for your treatment plant, here’s a closer look at what you need to know about the clarification process.

Primary vs. secondary clarification

All wastewater companies use primary and secondary clarifiers to treat wastewater. You’ll find primary clarifiers downstream of the plant’s screening and grit chambers, while secondary clarifiers are located downstream of the biological treatment or activated sludge facility.

While these two processes have similar design configuration and rely on gravity to do much of the work, they’re quite different. Here’s a closer look at both:

  • Primary clarification: This process is also known as sedimentation. It’s the first step in the treatment process which removes suspended solids, oil and grease. All solids and large particles in the water are removed during primary clarification, and sludge is allowed to settle to the bottom, where it’s collected by a rake and removed by a sludge removal system. All oil and grease floats to the surface, where it’s then skimmed off. Generally, you can expect a primary clarification system to remove 60 percent of suspended solids and between 30 and 40 percent of biological oxygen demand (BOD).
  • Secondary clarification: This part of the treatment process returns activated sludge. During this step, the biomass from microorganisms settles to the bottom of a tank as activated sludge and settles over a period of time. Then, the biomass is returned to the aeration tank and the process is repeated until the effluent is clean. At this point of the process, it’s ready to be sent for filtration and disinfection.

What clarification system options are available for your treatment plant?

There are three primary systems to consider when it comes to the clarification process in water treatment. They include:

  • Circular clarifiers: If a circular clarifier is right for your application and treatment goals, you’ll have to choose between segmented rake, spiral scraper or hydraulic removal models.
  • Rectangular chain and scraper clarifiers: Depending on basin length and solids loading specifications at your plant, a rectangular chain and scraper system may be right for your applications. They’re available in three-shaft and four-shaft configurations with a variety of chain types, including molded, filament wound and stainless steel.
  • Ballasted clarification: When it comes to effluent quality and lower life-cycle cost, ballasted clarification systems are best. The system will have either circular or rectangular clarifiers.

If you need help determining which clarification system is right for your treatment plant, reach out to professional wastewater companies in your area. They’ll be able to take into account application type, land footprint, performance goals and, most importantly, your budget when determining which type is best suited to your needs. Contact Enviro-Line Co., Inc. today to learn more about the wastewater treatment process and to discover which clarification system meets the needs of your operation.

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