NOVELTY - The wastewater purification system comprises a movable wastewater container incorporating a light-converting material including layers of upconverting luminescent materials and/or layers of downconverting luminescent materials, active and/or passive sun trackers incorporating rotatable and/or tilting screens positioned in the wastewater container and configured to serve as substrates for ingrowth of microorganisms and a rolling axis connected to the screens so that the screens rotate with the rolling axis, a fluid inlet and outlet pair, a gas inlet, and an inner light-reflecting surface.    USE - The system is useful for purifying wastewater such as sewage from municipal, agricultural and industrial sources, and to enhance photosynthesis of algae for the production of biogas, biofuel or other by-products.    ADVANTAGE - The system is capable of effectively purifying the wastewater thus providing the high quality water without unwanted inorganic compounds.    DETAILED DESCRIPTION - The wastewater purification system comprises a movable wastewater container incorporating a light-converting material including layers of upconverting luminescent materials and/or layers of downconverting luminescent materials, active and/or passive sun trackers incorporating rotatable and/or tilting screens positioned in the wastewater container and configured to serve as substrates for ingrowth of microorganisms and a rolling axis connected to the screens so that the screens rotate with the rolling axis, a fluid inlet and outlet pair, a gas inlet, an inner light-reflecting surface at a bottom of the container, a series of artificial light sources positioned opposite to the light-reflecting surface, a solar position sensor positioned outside to the container and connected to the rolling axis to sense the position of the sun such that the rolling axis is moved in accordance with the movement of the sun detected by the solar position sensor, and a controller that repositions the axis during the night in a position opposite to the direction of the sunset of the preceding day as measured by the solar position sensor. The fluid outlet is positioned at relatively higher level than the fluid inlet. The screens are covered with a layer of algae, which are microalgae or a mixture of macroalgae and microalgae. A wastewater settling pond with a cover is connected to the system for separating a fluid phase from a solid and/or sludge phase in received wastewater from a wastewater source (101). A processing unit is connected to the system to collect and process algae from the screens. The downconverting luminescent material of the light-converting device comprises quantum dots, where a core of each quantum dot comprises materials consisting of IIA-VIA, IIIA-VA, IVA-IVA and IVA-VIA semiconductors of 1-50 nm. A movement in accordance with the movement of the sun detected by the solar position sensor during daytime is according to the altitudinal angle of the sun, latitudinal offset of the sun and/or changes in azimuth angle. The active sun trackers comprise a microprocessor controller and/or an electro-optical controller. The passive sun trackers comprise a series of canisters having a low boiling point compressed gas fluid positioned within the canisters. An INDEPENDENT CLAIM is included for a method of treating wastewater.    DESCRIPTION OF DRAWING(S) - The diagram shows a flow chart of a wastewater algal purification system.    Wastewater source (101)    Sunlight (102)    Carbon dioxide emission source (103)    Wastewater algal purification system (120)    Algal processor. (130)