NOVELTY - The system comprises a bioreactor assembly (107) including a bioreactor module (110), a dispersion device oriented above the growth surface, a cap assembly (105), and an effluent outlet to permit the flow of effluent out of the chamber. The bioreactor module comprises a housing including an inlet to receive effluent discharge by a source, a substrate fixed within the housing, and a cleansing device for dislodging biomass formed on the substrate. The substrate comprises: a screen defining an algal growth surface, which is oriented vertically within the housing; and apertures.    USE - The system is useful for treating an effluent from an effluent source such as geothermal fluid source (all claimed), agricultural source, industrial source, municipal source and other wastewater source.    ADVANTAGE - The highly efficient system reduces the cost of disposal, minimizes the environmental risk by eliminating the need to transport the contaminated effluent, enables a very high proportion of light energy captured to be transferred to chemical storage as added biomass, and has an ability to provide high volume waste treatment.    DETAILED DESCRIPTION - The system comprises a bioreactor assembly (107) including a bioreactor module (110), a dispersion device oriented above the growth surface, a cap assembly (105), and an effluent outlet to permit the flow of effluent out of the chamber. The bioreactor module comprises a housing including an inlet to receive effluent discharge by a source, a substrate fixed within the housing, and a cleansing device for dislodging biomass formed on the substrate. The substrate comprises: a screen defining an algal growth surface, which is oriented vertically within the housing; apertures formed into the screen for permitting passage of fluid through the substrate; and a light source operable to direct photons toward the algal growth surface. The effluent is directed onto the substrate such that it travels downstream from an upper portion of the growth surface to a lower portion of the growth surface. The effluent flows over the growth surface to generate an algal biomass. The apertures have a diameter of greater than or equal to 1.5 mm. The dispersion device comprises a trough including a wall defining a cavity to receive the effluent, and trough channels formed into an exterior surface of the wall. The trough channels direct the effluent within the cavity toward the substrate growth surface. The cap assembly: is in fluid communication with the inlet of the bioreactor module; is operable to receive effluent from the source and to direct the effluent downstream to the bioreactor module; and includes a cap (115) and a cap housing (122) disposed over the cap. The cap housing is capable of storing the effluent for a predetermined period of time before directing the effluent downstream toward the bioreactor module. The cleansing device is in fluid communication with a pressurized fluid source, and comprises nozzles configured to generate a stream of fluid toward the growth surface. The housing includes a chamber operable to hold a volume of effluent. The substrate is positioned within the housing such that the substrate is partially submerged in the volume of effluent. The effluent outlet is disposed at an intermediate vertical location along the housing. The growth surface defines a textured surface, which is defined by projections and cavities formed into the substrate. The apertures are defined by a raised rib protruding from a surface of the substrate. The rib is configured to direct a portion of the effluent around the aperture as the effluence flows down the substrate. The raised rib comprises a deflection ramp extending distally from the raised rib, and opposed inclined surfaces. The light source comprises a first LED array and a second LED array, where the LED arrays are disposed on opposite sides of the substrate and are configured to selectively generate light having a first wavelength of 440-490 nm and a second wavelength of 630-740 nm. An INDEPENDENT CLAIM is included for a method of treating contaminated liquid effluent from a source.    DESCRIPTION OF DRAWING(S) - The diagram shows a schematic view of a treatment system.    Cap assembly (105)    Bioreactor assembly (107)    Bioreactor modules (110)    Cap (115)    Cap housing. (122)