This rapid review report has identified the wastewater treatment plant (WWTP) options used in emergency settings, with decentralised wastewater treatment systems (DEWATS) and mobile wastewater treatment units performing most effectively and with minimal costs. Examples are taken from refugee camps and internally displaced people (IDP) settlements due to the Iraq war, the Israeli-Palestine conflict, and the civil wars in Syria and Sudan. WWTP options used in Finland, Haiti, Iraq, Jordan, Palestine, Sudan and Turkey are discussed. Lessons learned from China and suggestions for the Rohingya crisis are also included.