Oil and grease must be removed from industrial wastewater to prevent what in sewers?

• A. Prevent plugging
• B. Prevent corrosion
• C. Improve odor control
• D. Increase BOD

Answer: (A)

Oil and grease in wastewater behave like sticky, floatable and solids-trapping materials in sewer lines. They rise to the surface or cling to pipe walls, trap solids, and can combine with other debris to form blockages or "fatbergs." By removing these greases before they enter the sewer, you prevent these obstructions and keep the flow open, reducing the risk of clogs and backups. That direct effect—prevention of sewer plugging—is the main reason for removing oil and grease in industrial wastewater pretreatment.

Other issues like odors or changes in BOD can be affected by grease, but they are not the primary reason for its removal in sewers, whereas plugging is.