Nutrient Removal and Biodiesel Production by Integration of Freshwater Algae Cultivation With Piggery Wastewater Treatment
Microalgae cultivation in wastewater, with the advantage of a faster uptake of nutrients such as nitrogen and phosphorus, represents one of the preferable solutions to the reduction of excessive nutrients. Meanwhile, microalgae have also been considered as one of the most promising feedstock for biodiesel production, which will not threaten the food production. Hence, an integrated approach, which combined freshwater microalgae Chlorellazofingiensis cultivation with piggery wastewater treatment, was investigated in the present study. The characteristics of algal growth, lipid and biodiesel production, and nutrient removal were examined by using tubular bubble column photobioreactors to cultivateC. zofingiensisin piggery wastewater with six dilution concentrations of 3500, 2500, 1300, 800 and 400 mg L–1 COD. Within 10-day cultivation, the 3500, 2500, 1300, 800 and 400 mg L–1 COD piggery wastewater media could respectively remove COD at 74.29%, 78.18%, 79.84%, 76.46%, 65.81% and 67.25%; TN at 78.72%, 81.03%, 82.70%, 77.81%, 70.88% and 68.96%; and TP at 85.00%, 89.23%, 98.17%, 98.62%, 99.44% and 100%. The specific growth rate and biomass productivity ranged from 0.287 to 0.492 day–1 and from 106.28 to 296.16 mg L–1 day–1,respectively. The initial nutrient concentration could influence lipid accumulation which ranged from 33.91% (3500 mg L–1 COD medium) to 45.81% (400 mg L–1 COD medium). The lipid and biodiesel productivities ranged from 48.69 to 110.56 mg L–1 day–1 and from 11.85 to 30.14 mg L–1 day–1,respectively. It is worthy of note that the diluted piggery wastewater with 1900 mg L–1 COD provided an optimal nutrient concentration for C. zofingiensis cultivation, where the advantageous nutrient removal andhighest productivities of biomass, lipid and biodiesel were presented.
Keywords— Microalgae, Chlorella zofingiensis, Piggery wastewater, Nutrient removal, Biodiesel production