A high efficiency treatment system (system) wastewater treatment system including a tank with a multi-chamber tank system that is designed to remove pollutants from domestic wastewater. Embodiments of the system consist of a pretreatment chamber, which is in fluid communication with an anoxic chamber, which is in fluid communication with an aeration chamber, which is in fluid communication with a clarification chamber, and which is in fluid communication with a polishing chamber. The system can be applied to remove suspended solids, BOD, ammonia, nitrate and TKN from wastewater.