A wastewater treatment system for use on marine vessels or land-based applications where wastewater is separated into two separate sources as graywater and raw sewage (blackwater). For blackwater, the treatment system incorporates five general phases (or zones): (1) screening, (2) clarifying, (3) filtering, (4) advanced oxidation, and (5) sludge reducing. For graywater, the treatment system incorporates three general phases (or zones): (1) screening (2) filtering, and (3) advanced oxidation. Each train of the treatment system (blackwater and graywater) can operate as a stand-alone system or can be assimilated into an integrated treatment train for both graywater and blackwater. This system is particularly useful in today's restrictive regulatory environment.