A method and portable system is disclosed for treating waste water received at a first location while in-transit to a second location. Waste water received by a portable treatment system is used to treat waste water while stationary at a first location and then the portable waste water system continues to treat the waste water while the portable treatment system is in-transit between the first location and a second location. This allows the transit time of the portable treatment system to be utilized to improve the quality of the waste water in the portable treatment system. Untreated waste water can be received by the system at a first location and during transport the waste water is treated by the portable treatment system, improving the quality of the effluent discharged from the portable treatment system when it arrives at the second location.