Primary Wastewater Treatment


Primary wastewater treatment, the second step in the wastewater treatment process beyond the preliminary treatment of a headworks, involves the physical separation of suspended solids from the wastewater flow using primary clarifiers. This separation reduces total suspended solids as well as the biological oxygen demand (BOD) levels and prepares the waste stream for the next step in the wastewater treatment process.

Primary Wastewater Treatment

Within the primary clarifiers, suspended solids are allowed to settle. A large amount, about 60%, of total suspended solids (TSS) are removed with the gravity separation that takes place. The biological oxygen demand (BOD) is also reduced by about 30% in this process.

After the primary treatment, the wastewater moves on to secondary treatment where a biological treatment process normally takes place.

Primary Treatment Technologies for Your Wastewater Applications:
Separation and Clarification

Primary Wastewater Treatment Case Study

Chain & Scraper: Los Angeles Hyperion Wastewater Treatment Plant

The City of Los Angeles’ Hyperion Wastewater Treatment Plant is one of the largest in the United States. It serves approximately 9 million people by treating 460 mgd of wastewater.

Built in 1949, the plant was designed to treat up to 450 mgd but was forced to reduce secondary treatment in the 1960’s to 120 mgd due to limited secondary capacity. The city faced numerous challenges.

With a governmental directive to cease ocean discharge of sludge by 1987 and provide secondary treatment to all wastewater by 1998, the city turned to Siemens to make the necessary changes.

Read Full Case Study

Primary Treatment Case Study

Primary Wastewater Treatment Products

Envirex® High Performance Clarifier
TowBro® Unitube Sludge Removal System
Envirex® Chain & Scraper 

Primary Wastewater Treatment Case Studies

Folded Flow® Dissolved Air Flotation System Improves Wastewater Treatment at Glatfelter

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