Which of the following may be permissible for disposal down the sanitary sewer?

Disposing of small quantities of very dilute methanol down the sanitary sewer may be permissible due to its low concentration and the fact that methanol is biodegradable. Sanitary sewers are designed to handle certain types of waste, particularly those that are non-toxic and in low concentrations, allowing for dilution and treatment by wastewater treatment facilities.

In contrast, concentrated acids, heavy metals, and organic solvents generally pose significant risks to public health and the environment, as they can be hazardous, toxic, or harmful when released into the sewage system. These substances may not only disrupt the biological processes at wastewater treatment plants but can also contaminate local water supplies and ecosystems. Therefore, the proper disposal methods for these materials often require specific protocols, such as hazardous waste disposal, rather than routine sewer disposal.