In a municipal wastewater treatment plant, the primary treatment step includes ________.

• A. biological degradation of organic matter by microorganisms
• B. chemical disinfection using chlorine or ozone
• C. physical removal of large solids by screening and sedimentation
• D. advanced nutrient removal through chemical precipitation

Answer: (C)

Verified step by step guidance

1. Understand the overall process of wastewater treatment, which typically includes primary, secondary, and tertiary treatment stages.
2. Identify the main goal of the primary treatment step, which is to remove large solids and suspended particles from the wastewater before biological or chemical processes.
3. Recognize that primary treatment primarily involves physical methods such as screening to remove large debris and sedimentation to allow solids to settle out of the water.
4. Differentiate primary treatment from secondary treatment, which involves biological degradation of organic matter by microorganisms.
5. Note that chemical disinfection and advanced nutrient removal are part of later treatment stages, not the primary treatment.