Which of the following is a type of wastewater generated from papermaking processes?

Spent sulfite liquid is a byproduct of the sulfite process used in papermaking. During this process, wood chips are treated with a mixture containing sulfurous acid and other chemicals to separate the lignin from cellulose fibers used to create paper. The resulting spent sulfite liquid contains various dissolved organic compounds, chemicals, and other contaminants that can be detrimental to the environment if not properly managed.

This makes it a specific type of wastewater generated directly from the papermaking industry, highlighting its relevance in discussions about wastewater treatment and management practices. In comparison, while waste oil and acidic waste are also types of wastewater, they are not specifically associated with the papermaking process. Chemical sludge refers to the solid waste generated during the wastewater treatment process itself, rather than being a direct byproduct of paper manufacturing. Thus, spent sulfite liquid is the most accurate choice in this context.