The invention is an improved controlled natural purification system for an advanced wastewater treatment and protein conversion and recovery. The system provides for treating municipal wastewater and associated organic industrial discharges anaerobically and aerobically. The system consists of such treatments in a tank complex where the waste organics are reduced to inorganic forms available for microalgae culture in tanks uniquely designed for rapid growth. The system includes a recovery mechanism to recover the algae for food purposes. Utilizing organic wastewater as the renewable resource, the system has the potential to develop from a wastewater treatment process that removes excess nutrients, producing reusable water and a commercially valuable algal by-product, to large scale algae farming cost-effectively producing millions of tons per year of sterile, stable, high protein algal foodstuff.