Production of wild Chlorella sp. cultivated in digested and membrane-pretreated swine manure derived from a full-scale operation plant

A wild Chlorella sp.was isolated from amanure storage tank and then cultivated under semi-continuous production conditions on four substrates, including digested swine manure (DIG) and digestate-derived liquid fractions obtained by digestate centrifugation (CLF) and ultrafiltration (ULF) in a full-scale digestate treatment plant, in order to evaluate differences in growth and depuration capacities. The microalga was capable of fast growth on some of the substrates, comparable to that obtained with 3N-BBM synthetic medium, productivities being 0.21 g L-1 d-1 of biomass for ULF and 3N-BBM media, 0.17 g L-1 d-1 biomass for CLF media and 0.10 g L-1 d-1 biomass for DIG media. Algal growthwas affected, above all, by the chemical oxygen demand (COD) of the starting culture mediawhich directly affected turbidity and also light availability. Nutrient contents, i.e. N and P, did not seem to affect the process. Chlorella sp.was capable of reducing about 95%-98% of N-NH4 + and 61-73% of COD,while micronutrients were almost completely removed from the cultures. However, most of the ammonia nitrogen was lost to the atmosphere due to the stripping phenomena caused by aeration and high pH during algal growth, so that only 30% of the nitrogen was successfully incorporated in the microalgal biomass. The isolated Chlorella proved to be a strong strain, capable of reducing macro- and micronutrient contents in the digested liquid streams. The full-scale digestate membrane treatment proved to be a suitable process to integrate with microalgae cultivation, improving the growth medium performance in terms of final biomass productivity.