Enhancement of biomass productivity and nutrients removal from pretreated piggery wastewater by mixotrophic cultivation of Desmodesmus sp CHX1

Promoting biomass production of the involved strains simultaneously with efficient nutrients removal from wastewater is realistic significance to ensure successful application of microalgae-based process for wastewater treatment. Enhancement of biomass productivity and nutrients removal by mixotrophic cultivation of Desmodesmus sp.CHX1 was conducted in this study when treating aerated piggery wastewater. The results showed that air-stripping might be an effective option as a pre-treatment to remove ammonia nitrogen from piggery wastewater. Mixotrophic cultivation of microalga-bacteria system significantly promoted algal growth and nutrients removal efficiency with the maximal biomass and lipid productivity being 0.869gl(-1)d(-1) and 118.2mgl(-1)d(-1) (14.5% of the lipid content), respectively, which were superior to other reported values. Nutrients in the piggery wastewater were also removed efficiently, for example, the removal rates of total nitrogen, ammonia nitrogen and total phosphorus were 87.3%, over 95%, and 93.1%, respectively. This study suggested that mixotrophic cultivation of microalgae-bacteria system might be a practical alternative to efficiently enhance nutrients removal from piggery wastewater coupled with biomass production. A slight reduction of chemical oxygen demand (COD), however, indicate that it cannot replace the traditional biological treatment, and more researches are required to find the optimum balance between reduction in COD value and biomass production.