abstract
Microalgae grown in swine wastewater were used as a promising strategy to produce renewable energy
by coupling wastewater bioremediation and biomass revalorization. The efficiency of a microalgae
consortium treating swine slurry at different temperature (15 and 23 C) and illumination periods (11
and 14 h) was assessed for biomass growth and nutrient removal at two NH4
þ initial concentrations (80
and 250 mg L1 NH4
þ). Favourable culture conditions (23 C and 14 h of illumination) and high ammonium
loads resulted in higher biomass production and greater nutrients removal rates. The initial NeNH4
þ
load determined the removal mechanism, thus ammonia stripping and nitrogen uptake accounted
similarly in the case of high NH4
þ load, while nitrogen uptake prevailed at low NH4
þ load. Under
favourable conditions, nitrogen availability in the media determined the composition of the biomass. In
this context, carbohydrate-rich biomass was obtained in batch mode while semi-continuous operation
resulted in protein-rich biomass. The revalorization of the resultant biomass was evaluated for biogas
production. Methane yields in the range of 106e146 and 171 ml CH4 g COD1 were obtained for the
biomasses grown in batch and semi-continuous mode, respectively. Biomass grown under favourable
conditions resulted in higher methane yields and closer to the theoretically achievable.