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

Abstract

Some starch-accumulating microalgae 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 microalgae/carbohydrate concentration (19.3 mg/L). The findings of this study provide direction for the application of real treated wastewater and scale-up of microalgae biomass and intracellular starch production.