A method for treating waste water containing ammonia comprising the steps of: i) passing the waste water as a feed solution through a first RO membrane (24) to produce a first permeate stream (30) and a first reject stream (32), ii) adjusting the pH of the first reject stream (32) to >9, iii) passing the first reject stream (32) through a second RO membrane (26) to produce a second permeate stream (36) containing ammonia and a second reject stream (38), and iv) passing at least a portion of the second permeate stream (36) to a cooling tower (12) to evaporate at least a portion of the ammonia.

A method and system used to purify water that removes or reduces volatile organic compounds, calcium carbonate, cyanuric acid, and sodium bicarbonate from water to acceptable levels.