Influence of three microalgal‐based cultivation technologies on different domestic wastewater and biogas purification in photobioreactor

To investigate the effects of different microalgae and culture methods on the purification of domestic wastewater and biogas, Chlorella vulgaris and Scenedesmus obliquus were selected. Three different culture methods (monoculture, microalgal–fungi cocultivation, and microalgal‐activated sludge cocultivation) were used to remove nutrients from four different domestic wastewaters and remove CO2 from raw biogas in a photobioreactor. The results show that the effluent from the centrate of pretreated urban wastewater (WW4) achieved the highest nutrient and CO2 removal efficiency. Cocultivation of C. vulgaris and activated sludge achieved the highest COD, TP, and CO2 removal efficiencies of 79.27%, 81.25%, and 60.39% with WW4, respectively. Cocultivation of C. vulgaris and fungi achieved the highest TN removal efficiency of 78.46% with WW4. The contents of C, N, and P in the microalgal‐activated sludge symbiont after treatment exceeded 50%, 8%, and 0.8%, respectively. Highly economically efficient energy consumption was achieved with WW4 for both C. vulgaris and S. obliquus. Microalgal‐activated sludge cocultivation was identified as the optimal option for the simultaneous purification of wastewater and biogas based on its high pollution and CO2 removal efficiency. This provides a reference for the microalgal‐based purification of actual domestic wastewater and raw biogas. Practitioner points Nutrient and CO2 were efficiently removed by C. vulgaris with activated sludge. CO2 was removed up to 60.4% and was economically viable. Cocultivation of C. vulgaris and fungi could achieve the highest TN removal with WW4. Three microalgal‐based technologies (mono‐cultivation of microalgae, co‐cultivation of microalgae with fungi or activated sludge) were applied for simultaneously removing nutrient in different domestic wastewaters and CO2 in biogas. Among the three culture treatment in this work, co‐cultivation of microalgae (C. vulgaris) with activated sludge was the optimum.