Waste to Wealth: Phycoremediation of Saline Wastewater From the Food Processing Industry Using Dunaliella salina to Produce Beta-Carotene in High Rate Algal Ponds

Abstract

Rapid urbanization and industrialization have led to a significant increase in the discharge of saline wastewater containing valuable resources. Saline wastewater is generated by industries such as desalination plants, food processing, textile and dyeing, pharmaceuticals, and metal processing industries. Currently, these wastewaters are treated in plants where they are evaporated to generate salt wastes, incurring high transportation, handling, and process costs that burden industries and disrupt their profitability. Consequently, industries are seeking alternative, economically viable treatment methods. Dunaliella salina, a halophilic algae, presents a promising solution. It can reduce nutrient concentrations in wastewater and produce industrially relevant compounds such as carotenoids, lipids, and proteins. This transforms saline wastewater treatment into a financially sustainable and environmentally friendly process. This study utilized saline wastewater from the food processing industry to cultivate D. salina in high-rate algal ponds (HRAP) or raceway systems. The objective was to effectively remove nitrate, phosphate, sulfate, and chemical oxygen demand (COD) from the wastewater while simultaneously producing valuable products. D. salina was cultivated in 5000 L of wastewater using HRAP for 45 days, and operating parameters were monitored periodically. The results showed that the nitrate, phosphate, sulfate, and COD from the brine were effectively removed with removal efficiencies of 95.4%, 93.4%, 67.6%, and 80%, respectively. After harvesting, the wet biomass obtained showed a maximum beta-carotene concentration of 5.2%, and the concentration was reduced to 4.7%, with a 10% loss due to drying. D. salina was found to be a potent tool for treating brine wastewater, effectively removing nutrients and simultaneously circularly producing beta-carotene at an industrial scale.