Abstract: A solar thermal based water treatment system and a process for treating impure/industrial wastewater is disclosed. The solar thermal based water treatment system vaporizes impure/wastewater using incident solar radiations in a third unit with only air as a medium. The system has a fourth unit and a fifth unit for condensing water vapor and obtaining purified water in the form of condensate. The system also includes an eighth unit for drying the sludge or slurry using dry air for obtaining dry solid waste. The system also includes a ninth unit to remove the undesirable gases from exhaust air before releasing in the atmosphere.