Final answer:
Septic tanks decrease burden on sewer systems, reduce energy usage, and act as a wildlife habitat.
Step-by-step explanation:
Septic tanks are environmentally responsible systems because they decrease the burden on combined sewer systems, reduce the energy used to mechanically treat and move water in municipal systems, and act as a habitat for wildlife. A septic tank system is an individual sewage treatment system for homes in typically rural settings. It includes a sewer line from the house, a septic tank where sludge settles and microorganisms decompose the solids, and a drain field where the clarified water seeps into the soil and is further purified.