What are the main goals of primary treatment in sewage treatment, and what are
some common processes used to achieve these goals
The main goals of primary treatment in sewage treatment are to remove solid materials and reduce the biochemical oxygen demand (BOD) of the wastewater.
Some common processes used to achieve these goals include the following:
1. Screening: This process involves removing large debris such as sticks, leaves, and plastics from the wastewater using physical barriers.
2. Sedimentation: In this process, wastewater is allowed to sit in a tank so that solids can settle to the bottom (sludge) and oils and grease can rise to the top (scum). The settled solids are then removed from the bottom.
3. Filtration: Filtration involves passing wastewater through a filter medium to remove smaller particles and suspended solids that were not removed during screening and sedimentation.
4. Flotation: Flotation is a process in which air bubbles are introduced into the wastewater to float and remove suspended solids.
5. Skimming: Skimming involves removing oils and grease that have floated to the surface of the wastewater.
6. Grinding: Grinding is used to break down larger solid materials into smaller particles that can be more easily removed in subsequent treatment processes.
By achieving these goals through the above-mentioned processes, primary treatment helps to improve the quality of wastewater before it moves on to secondary treatment processes.