Visible light is a potential innovative method for developing the activated sludge (AS) system. AS is consisted of a complex community of diverse microbes that respond differently to light based on wavelength, intensity, and exposure time. The present study examined the possibility of stimulating activated sludge using visible light radiation. Five light wavelengths (white, solar, red, blue, and green lights) are provided with three intensity levels. Mixed liquid suspended solid (MLSS) and mixed liquid volatile suspended solid (MLVSS) were used as indicators to evaluate activated sludge performance. From the experimental results, 15 – 20 days achieved high biomass productivity for all wavelengths. There was a direct relationship between AS biomass and intensity, except white light, the proportion was inverse. Green, blue, and red light achieved maximum stimulation of MLSS reached (48.57, 48.29, and 33.57%) relative to control at (130±3.41, 100±2.9, and 40±4.89 W m-2). Besides, the highest stimulation of MLVSS under green, white, and solar light was (84.54, 55.01, 39.33%) relative to control at (115±3.17, 24±3.72, 40±3.1 W m-2). The maximum growth rate (μ) of MLSS and MLVSS achieved under white and green lights reached (0.096235, and 0.115377 d-1) at (24±3.72, 115±3.17 W m-2), during 5 days, respectively. Van and the developed models could predict a high correlation exceeding (r = 0.98) with white and solar light.