A vessel configured to float on a body of seawater has a wastewater treatment system having a wastewater intake port for intaking wastewater onto the vessel, a wastewater treatment component for treating the wastewater to produce treated wastewater and sludge, and a treated wastewater conduit for transporting the treated wastewater away from the wastewater treatment component, a desalination system has a seawater intake for intaking seawater from the body of seawater onto the vessel, a desalination component for desalinating the seawater to produce concentrate and desalinated water, and a desalinated water discharge port for transferring the desalinated water from the vessel, a mixing system has a mixing tank for mixing the treated wastewater from the wastewater treatment system with the concentrate from the desalination system, and a wastewater discharge system for discharging the treated wastewater and concentrate mixture into the body of seawater.