Exploitation of Urban Landfill Leachate as Nutrient Source for Microalgal Biomass Production

Abstract

Increasing concern over climate change and the impact of greenhouse gas emissions as well as diminishing global oil reserves has pushed research into alternative energy sources. Among these options, reducing the cost of microalgae cultivation, a promising source for renewable energy, is a key step in commercializing biodiesel production. Microalgae also have a two-fold advantage thanks to the capability to treat waste streams by reducing contaminants via bioremediation. In this work, the possibility of exploiting nutrients from landfill leachate was tested. Some microalgal species are able to grow in the leachate as a substrate, but the chemical composition of this waste stream often leads to growth inhibition. Thus, using strain directly isolated from the target environment could avoid problems of inhibition, in order to obtain higher biomass productivity and nutrient, i.e. pollutant, removal. Acutodesmus obliquus is a microalgal species isolated from a pond containing pretreated leachate from an urban landfill located in Lazio (Italy). This strain was cultivated in leachate from a landfill located in Istrana (TV), Italy. The leachate was diluted with distilled water and the growth of the species was measured. Several dilution ratios were tested and the maximum growth rate was obtained with 10 % of leachate in water, even though an acceptable growth was also observed with 1:2 dilution. Lipid content of about 38 – 48 % dry weight was measured. Nutrients uptake in the form of ammonia from the various leachate dilutions ranged from 30 - 97 % and, generally, it was >90 % in the case of phosphorus, which was assessed as the limiting nutrient for growth. The outcome of this work has established the real potential of utilizing ammonia-N enriched leachate as the nutrient source for yielding high lipid content algal biomass, by using native strains. Based on experimental results, preliminary calculations on photobioreactor design to treat leachate from urban landfill were carried out.