Bioprocess Integration of Candida ethanolica and Chlorella vulgaris for Sustainable Treatment of Organic Effluents in the Honey Industry

Honey processing is closely linked to water pollution due to the lack of a specific wastewater treatment. This work presents a sustainable and innovative solution based on two sequential bioprocesses using a real effluent from an Argentine honey-exporting facility. In the first stage, the honey wastewater was enriched with a non-Saccharomyces yeast (Candida ethanolica), isolated and identified from the same effluent. Yeast treatment was carried out in a bioreactor, achieving nearly double the efficiency in total sugar removal compared to the control (native flora). Subsequent clarification with diatomaceous earth reduced optical density (91.6%) and COD (30.9%). In the second stage, secondary sewage effluent, was added to the clarified effluent and inoculated with Chlorella vulgaris under different culture conditions. The best microalgae performance was observed under high light intensity and high inoculum concentration, reaching a fivefold increase in cell density, a specific growth rate of 0.752 d⁻¹, and a doubling time of 0.921 d. Total sugar removal in this stage was under 28%, while cumulative COD removal reached 90% in nine days under both lighting conditions. The synergistic use of complementary microorganisms and different effluents enhances microalgal growth and supports to the overall sustainability of an integrated approach to managing all wastewater streams from honey production.