Impact of pH on the efficacy of Galdieria sulphuraria ACUF 427 in urban wastewater treatment: Effects on contaminant removal, biomass, and phycocyanin production

Environmental pollution, driven by increasing human population and urbanization, generates significant waste. Utilizing microalgae to treat urban wastewater is a promising solution to current water pollution challenges. This research investigates the treatment of primary-settled urban wastewater at initial pH levels of two and four using the thermo-acidophilic microalga Galdieria sulphuraria ACUF 427. Our results demonstrated that G. sulphuraria effectively reduced chemical oxygen demand (COD), ammonium nitrogen (N-NH4+), ammonia nitrogen (N-NH3), phosphate phosphorus (P-PO43-), and five-day biochemical oxygen demand (BOD5) showing removal rates of 72.41 mg L-1 day-1, 4.907 mg L-1 day-1, 3.812 mg L-1 day-1, 0.864 mg L-1 day-1, and 42.6 mg L-1, respectively, at pH 4. The reduction in COD was significantly greater (P = 0.0009) in urban wastewater at pH 4 compared to pH 2. However, there was no statistically significant difference in algal biomass (dry weight) (p = 0.580) or phycocyanin production (p = 0.266) between the two pH levels. Notably, algal biomass and phycocyanin levels were higher in urban wastewater compared to the standard Allen Medium at both pH levels. Additionally, Escherichia coli levels were reduced to undetectable levels (0 CFU100 mL-1) within four days in both media. Overall, G. sulphuraria demonstrates significant potential for contaminant removal and biomass and phycocyanin production from urban wastewater, positioning it as a promising solution to contemporary aquatic environmental pollution.