A system and method for evaporative treatment or wastewater which minimizes scaling and system maintenance is disclosed. The apparatus can include an evaporation vessel with a heating source to evaporate water from a solution under treatment and a drain valve for draining the solution after treatment. The apparatus can also include one or more sensors configured to measure parameters of a solution under treatment and a user programmable controller to control the treatment process based on such measurements. A user can configure the controller to define the detection of a solution's critical state where contaminant concentrations are maximized yet scaling is minimized. When a critical state of the solution is reached a portion of the treated solution can be removed and the vessel refill with new wastewater thereby lowering the concentration of the remaining solution the repealing the evaporation and drain cycle until all wastewater has been treated.