Resumen
Chemical fertilizer is the most common nutrient source in cultivating microalgae. However, its usage is very expensive and could lead to environmental problems. This led to the recent development of compost derived from animal manure as the alternative nutrient source for the growth of microalgae. It is rich in nitrogen & phosphorus, low cost and environmentally friendly. However, one limitation of compost is its naturally present dark brown colour which limits the light intensity penetrate through the medium, reduced the light uptake by microalgae and eventually retards the growth and biomass productivity of microalgae. Hence, UV irradiation and ozonation were used in present work to decolorize the compost so that the medium is suitable for the growth of microalgae. After experiment, it was determined that the optimum operating condition for decolorization was at pH 12, ozone flowrate of 3 L/min and ozone concentration of 30 mg/L. At optimum condition, decolorization efficiency of 16.52 % and 40.88% were attained after ozonation time of 8 hours and 24 hours, respectively. After decolorization, it was observed that the growth rate of Chlorella vulgaris was higher in decolorized compost, with specific growth rate and biomass productivity of 0.191 day-1 and 0.066 gL-1day-1, respectively compared to those of untreated compost with specific growth rate and biomass productivity of 0.137 day-1 and 0.040 gL-1day-1, respectively. The lipid content extracted from Chlorella vulgaris grown in decolorized compost was also higher than those grown in untreated compost, at 20 wt. % and 15 wt. %, respectively. For kinetic growth study, Richard Model was determined as the best model in estimating the growth kinetics of Chlorella vulgaris in decolorized compost as this model has highest R2 value, lowest RMSD and its residual plots was least scattered among all the three models.