Human: What is a septic system, and what are some of the pros and cons of septic systems? Assistant: 
A septic tank is an underground storage tank that contains wastewater from a home’s plumbing system. The tank has two compartments separated by a membrane. The first compartment holds the solid waste, while the second compartment holds the liquid waste. When the tank is full, it is emptied into a leach field, which is a shallow trench or bed of gravel that absorbs the waste. The liquid waste then flows through the soil into the groundwater below. This process helps to filter out harmful substances before they reach the groundwater.