Nitrogen removal from landfill leachate by microalgae

Abstract

Landfill leachates result from the degradation of solid residues in sanitary landfills,thus presenting a high variability in terms of composition. Normally,these effluents are characterized by high ammoniacal-nitrogen (N–NH4+) concentrations,high chemical oxygen demands and low phosphorus concentrations. The development of effective treatment strategies becomes difficult,posing a serious problem to the environment. Phycoremediation appears to be a suitable alternative for the treatment of landfill leachates. In this study,the potential of Chlorella vulgaris for biomass production and nutrients (mainly nitrogen and phosphorus) removal from different compositions of a landfill leachate was evaluated. Since microalgae also require phosphorus for their growth,different loads of this nutrient were evaluated,giving the following N:P ratios: 12:1,23:1 and 35:1. The results have shown that C. vulgaris was able to grow in the different leachate compositions assessed. However,microalgal growth was higher in the cultures presenting the lowest N–NH4+ concentration. In terms of nutrients uptake,an effective removal of N–NH4+ and phosphorus was observed in all the experiments,especially in those supplied with phosphorus. Nevertheless,N–NO3 − removal was considered almost negligible. These promising results constitute important findings in the development of a bioremediation technology for the treatment of landfill leachates.