A method for collecting effluent from an engine comprising: providing a portable trailer having a plurality of sides in a retracted and non-operational configuration forming an internal compartment and at least one droplet separator panel; and moving at least two of said sides from said retracted and non-operational configuration to an open position and an operational configuration wherein said two sides create a path for channeling an effluent/air mixture containing engine wash water from said engine to said at least one droplet separator panel; and separating said engine wash water from said air with said at least one droplet separator panel.