The use of Chlorella vulgaris in reducing the organic load of poultry slaughterhouse wastewater: Modeling and optimization of influential factors in the process

Background: Wastewater from poultry slaughterhouses is a serious environmental threat if they are incompletely treated. Recently, the utilization of microalgal species has gained significant attention for treating such wastewater. Chlorella vulgaris is one of the most efficient microalgae for treating poultry slaughterhouse wastewater due to its exceptional capacity for N, P, and chemical oxygen demand (COD) removal. This study aimed to investigate the impact of initial total nitrogen concentration, total phosphorus, photoperiod, and cultivation time on reducing the organic load and enhancing the production of biomass in slaughterhouse wastewater. Methods: Samples were collected from the effluent of a poultry slaughterhouse and underwent qualitative analysis. C. vulgaris was cultivated in the BBM culture medium. Experiments were designed using the response surface method. The designed experiments were then carried out and the obtained data were subjected to analysis of variance (ANOVA), resulting in fitted models for the data on organic load removal and biomass production. Numerical optimization was performed to optimize COD removal and increase algal biomass. Finally, the models were validated. Results: The results demonstrated that the quadratic model has a good fit for COD removal and biomass increase data. In the optimal conditions, including TN = 600 mg/L, TP = 34 mg/L, culture duration = 15 d, and photoperiod = 12.6 hr, the COD removal efficiency and algal biomass production were 93.88% and 92.37%, respectively. Conclusion: Chlorella vulgaris exhibits significant potential for the removal of the organic load from poultry slaughterhouse effluent. Also, substantial algal biomass is generated, which can be used in various areas such as livestock feed and sanitary uses.