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How much suspended material and biochemical oxygen demand does primary treatment remove?
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wastewater treatment
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In the context of wastewater treatment, primary treatment is a physical process designed to remove material that floats or settles by gravity, such as debris and grit.1
Regarding the removal efficiency of this stage:
- Suspended Solids: Primary treatment typically removes approximately 60 percent of total suspended solids.2
- Biochemical Oxygen Demand (BOD): It removes about 35 percent of biochemical oxygen demand.2
It is important to note that primary treatment does not remove dissolved impurities. Because these removal rates are generally insufficient to meet modern environmental standards for protecting public health and water quality, primary treatment is typically utilized as a preliminary step before secondary treatment, which is capable of removing more than 85 percent of both suspended solids and BOD.2