TECHNOLOGY FOCUS - BIOLOGY - Preferred Components: The phototactic heterotrophic microorganism is one of a phototactic protist or a phototactic alga exhibiting negative phototaxis, preferably a euglenoid.    TECHNOLOGY FOCUS - ENVIRONMENT - Preferred Method: The method of treating wastewater and cultivating biomass further comprises: diverting a first portion of the high-solids effluent to the bioreactor, and at least one of dewatering and drying a second portion of the high-solids effluent to provide the concentrated biomass paste; hydrolyzing the biomass paste and converting the hydrolyzed paste into ethanol; or adjusting pH of the bioreactor effluent to favor growth of the population over growth of competitor microorganisms. The step of dewatering the high-solids effluent includes centrifuging, belt pressing or heated screw pressing the high-solids effluent. The wastewater influent: includes a biological oxygen demand (BOD), a concentration of nitrogen and a concentration of phosphorus sufficient to grow the population; or is supplemented with a secondary carbon source including at least one of glycerin or a biodiesel by-product. The biomass paste is fractionated by at least one of acid fractionation, base fractionation, high pressure fractionation or mechanical fractionation to form a paramylon fraction and a non-paramylon fraction, which includes a wax-ester fraction. The phototactic heterotrophic microorganism is exposed to another source of light while in the aerated bioreactor, where the other light source has at least one of an intensity and a wavelength sufficient to promote growth of the population. The method of cultivating the biomass further comprises at least one of dewatering and drying the high-solids effluent to form a concentrated biomass paste.    TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The source of light has a wavelength of 400-550 nm.    TECHNOLOGY FOCUS - INSTRUMENTATION AND TESTING - Preferred Components: The system for cultivating biomass further comprises: a light clarifier in fluid communication with the aerated bioreactor, where the light clarifier is configured to receive the bioreactor effluent and expose the population to the source of light; a pH controller (in fluid communication with the aerated bioreactor), which is configured to modulate pH of the bioreactor effluent, where the modulated pH is conducive to growth of the population and militates against growth of competitor microorganisms; and a biomass concentrating subsystem including at least one of a lysing subsystem, a flocculation subsystem, a membrane filtration subsystem or a dissolved air flotation subsystem to separate solids including the population and liquid from the bioreactor effluent. The source of light includes an artificial lighting system disposed adjacent the light clarifier, where the lighting system provides a light having the intensity and wavelength to cause the population to self concentrate. The system for cultivating biomass further includes another artificial lighting system (disposed adjacent the aerated bioreactor), which provides another light having at least one of an intensity and a wavelength sufficient to promote growth of the population and not cause the population to self concentrate in the aerated bioreactor. EXAMPLE - No suitable example given.