Abstract
Microalga Ochromonas danica is able to accumulate high quantities of lipids by ingesting microbial cells through phagotrophy as well as taking up dissolved organics through osmotrophy. In this study, waste activated sludge (WAS) was pretreated with high intensity alkali, and then fed to O. danica for growth. Results show that, with WAS pretreated at pH 12 for 24 h, about 56.4% of WAS organics were released out of floc particles either as microbial cells or dissolved organics. O. danica was able to consume 84.6% of the released microbial cells and 61.0% of the released dissolved organics. By growing O. danica with the alkali-pretreated WAS, 28.6% of WAS organics were converted into algal biomass. The produced algal biomass was rich in lipids, 42.3% of its dry matter. Furthermore, WAS organics reduction rate was significantly accelerated. Around 53.0% WAS organics were reduced with 1 day of alkali pretreatment and 5 days of O. danica’s growth. Whereas, only 37.1% of WAS organics were reduced in total time of 40 days through conventional anaerobic digestion.