Application of real treated wastewater to starch production by microalgae: Potential effect of nutrients and microbial contamination

Some starch-accumulating micmalgae are promising biomass resources for producing platform chemicals for biorefinery applications. The use of treated wastewater as the cultivation medium has been considered because real treated wastewater contains not only nutrients, but also bacteria from activated sludge. In this study, the potential feasibility of real treated wastewater for starch production by Chlorella-related microalgae was investigated by evaluating the effect of: 1) chemical constituents and 2) microbial contamination in real treated wastewater, and 3) disinfection of treated wastewater by chlorination. The use of real wastewater showed the highest microalgae/carbohydrate productivity than simulated wastewaters. For high carbohydrate content, a relatively low nitrogen concentration was important. Meanwhile, biological contamination originating from the treated wastewater showed inhibition on microalgal growth, demonstrating the necessity for contamination control (e.g. chlorination) during starch production using domestic treated wastewater as the growth medium. Then, three chlorination concentrations were compared, and chlorination at 2.0 mg Cl/L for 15 min was the most effective to maintain a high proportion of micmalgae/carbohydrate concentration (19.3 mg/L). The findings of this study provide direction for the application of real treated wastewater and scale-up of micmalgae biomass and intracellular starch production.

Automated summary

The study found that real treated wastewater is more promising for green microalgae starch production than simulated wastewater, emphasizing the importance of low nitrogen concentration for high carbohydrate content and the need to control microbial contamination. Chlorination at 2.0 mg Cl/L for 15 min was found to be the most effective for maintaining a high proportion of microalgae/carbohydrate concentration.