Which of the following should not be used as they significantly increase suspended solids in sewage systems?

The use of garbage disposals in sewage systems is discouraged because they introduce a significant amount of food waste into the wastewater. This food waste contains high levels of organic materials, which can increase the concentration of suspended solids in the system. When these solids accumulate, they can lead to clogs and hinder the effective treatment processes in septic systems and other on-site sewage facilities.

In contrast, septic tanks are designed specifically to handle wastewater and separate solids from liquids, composting toilets are engineered to break down waste through aerobic processes, and washers and dryers are standard appliances that can be managed within a sewage system when used properly. These alternatives either minimize or are designed to handle waste effectively without significantly increasing suspended solids, making garbage disposals the outlier in this context.