Water and waste from the toilet go to either a local septic system or into the sewer system once they are flushed. Local septic systems break down solid waste and usually drain to the soil in a yard, while the sewer systems carry waste to a water treatment plant.
Homes and businesses that do not have a local septic system send material waste from the toilet to the local sewers. From there, the waste water flows to treatment plants. The sewage usually first passes through a headworks where large solid objects are filtered out. Material waste is turned into sludge and broken down by microbes at a later point in the treatment.