Which of the following items may be discharged into a municipal sanitary wastewater collection system?

The correct answer is based on the understanding of municipal sanitary wastewater collection systems and the regulations surrounding the discharge of substances into these systems. Discharging a substance that results from the pretreatment of an industrial waste is permissible because these substances are often treated to ensure they meet specific regulatory standards for discharge into the municipal system. This pretreatment process typically removes harmful components, making the waste safe for disposal.

In contrast, not all substances that might seem harmless or common are suitable for discharge. While household waste can usually be discharged, it is essential to consider that not every household item is safe for municipal systems, given that some may introduce harmful chemicals or contribute to system inefficiencies. Consequently, substances that eliminate odors could either contain harmful chemicals or disrupt the biological processes in wastewater plants, making them suspect choices for direct disposal. Likewise, while non-toxic substances appear safe, they can still pose risks if they disrupt microbial activity or contribute to system blockages.

Therefore, the option about pretreatment signifies adherence to safety standards and is the most reliable choice for what may be discharged into a municipal system, reflecting the goals of protecting public health and the environment.