The impact of light intensity and wavelength on the performance of algal-bacterial culture treating domestic wastewater

Abstract

Light is the main energy source for microalgae, and the intensity and wavelength of light influence cell metabolism and biomass composition, which, in turn, affects wastewater treatment. The objective of this study is to examine how different light intensities and light wavelengths affect the growth of mixed algal-bacterial culture while treating sewage. Three different light intensities (100, 200, and 300 μmol/m2-s) of four different light wavelengths (blue, red, white, and yellow) were selected for this study. The dissolved organic carbon (DOC), dissolved nitrogen (DN), and dissolved phosphorus (DP) in influent and effluent samples were measured, along with chlorophyll content in the biomass. The highest chlorophyll concentration of 3.5 mg/L was observed at 100 μmol/m2-s intensity of red light. The concentration of chlorophyll decreased as light intensity increased, with exception of white light. The highest DOC removal of 84% was observed at 300 μmol/m2-s intensity of blue light whereas the highest DN (51%) and DP (80%) removal was observed with a red light intensity of 100 μmol/m2-s. Overall, blue light with an intensity of 300 μmol/m2-s and red light with an intensity of 100 μmol/m2-s were found to be the most efficient at removing carbon and nutrients. The results suggested that the color and intensity of light influence algal-bacterial growth and wastewater treatment efficiency.

Quantifying Microalgae Growth by the Optical Detection of Glucose in the NIR Waveband

“…Although there are reports on the detection of starch at the region around 980 nm [56,57], it is highly possible that the authors were actually referring to the detection of glucose, as glucose monomers combine to make starch [58,59] (see Figure 2). It is well established that green microalgae undergo photosynthesis to produce glucose [40,41], which is then converted into other carbohydrate components such as starch (used for energy storage in plants) [42,43], cell wall polysaccharides (such as cellulose, hemicellulose, and pectin) [44][45][46], and glycolipids [47]. Since the absorbance at 940-960 nm is observed as early as day 0 and consistently increases until day 23, this wavelength could be highly indicative of the glucose content in the culture, as glucose is the precursor of the other complex compounds (see Figure 2) [48][49][50].…”

“…It is well established that green microalgae undergo photosynthesis to produce glucose [ 40 , 41 ], which is then converted into other carbohydrate components such as starch (used for energy storage in plants) [ 42 , 43 ], cell wall polysaccharides (such as cellulose, hemicellulose, and pectin) [ 44 , 45 , 46 ], and glycolipids [ 47 ]. Since the absorbance at 940–960 nm is observed as early as day 0 and consistently increases until day 23, this wavelength could be highly indicative of the glucose content in the culture, as glucose is the precursor of the other complex compounds (see Figure 2 ) [ 48 , 49 , 50 ].…”

Biofertilizante a partir de Chlorella vulgaris

“…Durante el período de cultivo se mantuvieron condiciones controladas de luz y agitación. Se usó luz roja con una intensidad de 144 luxes en un ciclo de 12:12 horas (Chu et al, 2021;Katam et al, 2022). Se proporcionó agitación constante a los fotobiorreactores mediante una bomba con motor de aire, y la temperatura ambiente promedio durante el cultivo se mantuvo entre 14 y 20 °C, rango adecuado para el crecimiento de la microalga Chlorella vulgaris (Collahuazo y Araujo, 2019), monitoreado cada tres días.…”

Hydrobiological studies of freshwater resources from Kerala, India

“…The optimal light intensity that algae require is approximately 8700 lux, the higher the light intensity, the higher the algal growth rate. But high levels of light intensity up to saturation point may lead to photo-inhibition (Xu et al, 2016, Metsoviti et al, 2019, Katam et al, 2022. pH is one of the most important limiting factors that influence the chemical and biological processes of water.…”