Optimisation of Scenedesmus almeriensis production using pig slurry as the sole nutrient source

Abstract

Pig slurry was used as the sole nutrient source to produce biomass of the microalga Scenedesmus almeriensis using laboratory-scale bubble column photobioreactors. No differences in terms of biomass productivity were observed between fresh and digested pig slurry. The optimum dilution rate to enable the processing of the largest amount of pig slurry per litre was 5%, which led to a biomass productivity rate of 0.68 g·L-1·day-1, comparable to that of the standard growth medium formulated using pure chemicals (0.70 g·L-1·day-1). The inlet N-NH4+ concentration was approximately 180 mg·L-1, with inhibitory effects being observed at concentrations higher than 200 mg·L-1. The N-NH4+, N-NO3-, P-PO43-, and chemical oxygen demand removal rates were 34.1, 0.5, 2.1, and 519.3 mg·L-1·day-1. The observed turbidity of the media did not affect microalgal growth at the studied dilutions. Ozonation effectively reduced the chemical oxygen demand concentration of the media, but no effect on microalgal growth was observed. Overall, pig slurry was an effective nutrient source for the mass production of S. almeriensis, and this strain was shown to be robust with a N-NH4+ tolerance up to 200 mg·L-1 and the potential use in the bioremediation of agro-industrial wastes.