Final answer:
The correct choice for wastewater primary treatment is Floating fats, oils, and greases. Primary treatment involves the removal of solid waste and floating substances before the water proceeds to secondary treatment. The option (D) is correct.
Step-by-step explanation:
The wastewater primary treatment essentially involves the removal of solid waste materials and floating substances such as fats, oils, and greases from the sewage. During this phase, sewage is stored in a basin where the heavier solids can settle to the bottom as sludge, and lighter substances such as floating fats, oils, and greases rise to the top. These substances are then skimmed off, and the resulting semi-clarified liquid is moved on to the secondary treatment phase.
The options like Nitrogen or Phosphorus, and Activated Sludge are involved in other stages of the sewage treatment process such as secondary treatment or tertiary treatment for nutrient removal or biological matter decomposition, respectively. Corrugated plastic is not typically associated with any specific stage of sewage treatment and appears to be an irrelevant option in the context of this question. Therefore, option (D) is correct.