Toxicity alleviation for microalgae cultivation by cationic starch addition and ammonia stripping and study on the cost assessment

Abstract

Aiming at promoting microalgae-based anaerobically digested swine manure (AD-SM) treatment, this work evaluated the feasibility of removing turbidity and ammonia in swine manure by cationic starch addition and air bubbling-driven ammonia stripping. It was observed that turbidity and ammonia toxicity were two main factors limiting algae growth. Addition of cationic starch effectively reduced turbidity of AD-SM by 77.10% in 40 min. 6 L min-1 air flow rate and 5 h stripping time were regarded as good conditions for ammonia stripping. An economic analysis was conducted to assess the feasibility of this pretreatment strategy in a pilot scale system and results indicated that unit energy input and freshwater consumption were 0.036 kW h g-1 dry biomass and 0.76 L g-1 dry biomass, respectively, much lower than those of a high dilution strategy. So it is a more promising and feasible way to pretreat AD-SM with low dilution by turbidity removal and ammonia stripping.