Recycling of landfill leachate nutrients from microalgae and potential applications for biomass valorization

Abstract

Microalgae have a high potential for the bioremediation of landfill leachate, mainly via nutrients removal, with the possibility of using the biomass for different purposes, depending on its characteristics. The present work aimed to evaluate the effect of hydraulic retention time (HRT) on the growth of microalgae in landfill leachate and on the composition of the biomass. Three photobioreactors (PBRs) with HRTs of 3, 6, and 10 days were used (PBRs 1, 2, and 3, respectively). Temperature, pH, ammonia nitrogen, total phosphorus, chemical oxygen demand, volatile suspended solids (VSS), and chlorophyll a (chl a) were monitored. The biochemical characterization of the biomass was carried out for lipids, carbohydrates, proteins, and ash. Chl a concentrations were 15.1 mg.L-1, 13.3 mg.L-1, and 4.9 mg.L-1 for PBRs 1, 2, and 3, respectively. For VSS, the concentrations were 130.4 mg.L-1 in PBR1, 149.1 mg.L-1 in PBR2, and 124.2 mg.L-1 in PBR3. The highest proportion of the biomass of the three reactors was protein, reaching 51.1% in PBR2. This result is justified by the high nitrogen concentration in the landfill leachate. The highest lipid accumulation occurred in PBR3, reaching 16.6%, due to the greater nutritional limitation imposed by the higher HRT. The results of this study provide important information for the use of HRT as an operational parameter for the production of algal biomass in landfill leachate, both in terms of productivity and biomass composition.