Chemical and Biochemical Mechanisms of Purple Bacteria in Wastewater Treatment: Optimization and Resource Recovery

Abstract

Given the environmental concerns arising from industrial wastewater pollution and the need for sustainable treatment solutions, this study investigates the performance of the purple bacterial strain Rhodobacter capsulatus Z08 in wastewater treatment and resource recovery through its chemical and biochemical reactions. The primary aim was to determine the effects of optimal conditions—including pH = 7.5, temperature of 30°C, and continuous illumination (500–1000 lux)—as well as various light conditions (natural light, darkness, and infrared) combined with different sulfate concentrations (0.1, 0.5, and 1 g S/L) on pollutant removal efficiency and biomass enhancement. The methodology involved conducting controlled experiments to measure the reduction in chemical oxygen demand (COD), changes in biomass, and heavy metal removal, alongside assessing the impact of sulfate-induced stress on the system’s performance. Results demonstrated that under optimal conditions, COD was reduced by up to 88%, biomass increased by 38%, and heavy metal removal reached 90%; additionally, natural light under microaerobic conditions yielded a 74% COD reduction, while dark aerobic conditions achieved a 62% reduction. In sulfate stress tests, a concentration of 0.1 g S/L resulted in nearly zero effluent COD, whereas increasing sulfate to 0.5 and 1 g S/L produced effluent COD values of 100–200 mg/L and approximately 600 mg/L, respectively. Furthermore, switching the light source to infrared led to complete COD removal (0 mg/L) and stabilization of ammonium levels between 10 and 15 mg N/L. Overall, these findings underscore that precise optimization of operational parameters, particularly light exposure and sulfate concentration, is essential for achieving higher efficiency in industrial wastewater treatment and effective biomass recovery, thereby advancing sustainable and economically viable technologies.