Difference between PRI.art and secondary biological sewage treatments:

PRI.art (Primary Treatment):
- The primary treatment of sewage involves the physical removal of large solid particles and floating debris from the wastewater.
- It is the first step in the sewage treatment process and is also known as preliminary treatment.
- The main purpose of primary treatment is to reduce the amount of suspended solids and organic matter in the wastewater.
- Primary treatment methods include screening, grit removal, and sedimentation.
- Screening involves the use of screens to remove large objects such as sticks, rags, and plastics from the wastewater.
- Grit removal is done to remove heavy particles like sand and gravel by settling or using grit chambers.
- Sedimentation is the process of allowing the wastewater to settle in large tanks, where solid particles settle at the bottom and are removed as sludge.

Secondary Biological Sewage Treatment:
- Secondary treatment is the next step in the sewage treatment process after primary treatment.
- It involves the use of biological processes to further remove the dissolved and suspended organic matter from the wastewater.
- The main purpose of secondary treatment is to reduce the biochemical oxygen demand (BOD) of the wastewater, which is a measure of the amount of organic matter present.
- Secondary treatment methods include activated sludge process, trickling filter, and rotating biological contactor.
- In the activated sludge process, the wastewater is mixed with a culture of microorganisms (activated sludge) in aeration tanks. The microorganisms consume the organic matter and convert it into biomass and carbon dioxide.
- Trickling filter involves the use of a bed of rocks or plastic media, over which the wastewater is trickled. The microorganisms attached to the media break down the organic matter.
- Rotating biological contactor consists of a series of plastic discs that rotate in the wastewater. The microorganisms attached to these discs degrade the organic matter.
- Secondary treatment also helps in the removal of nutrients such as nitrogen and phosphorus from the wastewater.

In summary, the primary treatment of sewage focuses on the physical removal of large solid particles, while secondary biological treatment involves the use of microorganisms to further degrade the organic matter in the wastewater.

Primary sewage treatment is a physical process that removes large impurities while secondary sewage treatment is a biological process that removes organic matter of sewage through the action of microbes.