Utilization of chemical wastewater for CO2 emission reduction: Purified terephthalic acid (PTA) wastewater-mediated culture of microalgae for CO2 bio-capture

The present study aimed to prove the potential of chemical wastewater utilization for CO2 emission reduction. Purified terephthalic acid (PTA) wastewater was applied as the culture medium of green microalgae (Chlorella pyrenoidosa) for CO2 bio-capture. Algal biomass and chlorophyll a content were determined as algal physiological response, and the CO2 capture efficiency and photosynthetic rate were also evaluated. Due to low pH value (pH = 4.40), the alga was unable to grow in the raw PTA wastewater, while it preferred tolerance and adaptation in the pH adjusted wastewater (pH = 7.40) and the treated PTA wastewater, respectively. Generally, 75.55-90.25 g/d of the algal biomass (dry weight) was yielded of the PTA wastewater per ton. While both chlorophyll a content of unit algal density and CO2 capture rate with the treated wastewater were higher than those with the untreated PTA wastewater. Additionally, the algal ability to fix CO2 was evaluated when the concentration of CO2 was set at 2%, 5%, 10% and 15%, respectively. Our results showed that the CO2 capture rate and the photosynthetic rate of the algae when cultured with the treated wastewater were higher than these with the untreated PTA wastewater. The highest algal CO2 capture rate was obtained as 82.15% (2% CO2, with untreated wastewater) and 91.59% (10% CO2, with treated wastewater), respectively. It is the first time to report algal CO2-capture with chemical wastewater-mediated culture, and our study provided a trinity model to achieve water saving, CO2 emission reduction and energy regeneration in an integrated strategy.