What characterizes primary treatment in wastewater management?

Primary treatment in wastewater management is characterized by the process of separating settleable and floatable substances from wastewater. This stage primarily focuses on physical processes to remove larger solids and particulate matter before the wastewater moves on to secondary treatment. During primary treatment, wastewater typically undergoes screening to remove large debris, followed by sedimentation, where heavier solids settle to the bottom of a treatment tank while lighter materials, such as fats and oils, float to the surface. This process effectively reduces the overall volume of solids and helps to clear the water, making it less polluted for subsequent treatment stages.

The other options reference processes or concepts not associated with primary treatment. For instance, chemical reactions, advanced filtration technologies, and referring to a last treatment step all pertain to later stages or different methods of wastewater treatment rather than the initial removal of solids characteristic of primary treatment.