Hydrocarbon production from secondarily treated piggery wastewater by the green alga Botryococcus braunii

Abstract

A laboratory study was conducted on the removal of nitrogen and phosphorus from piggery wastewater during growth of Botryococcus braunii UTEX 572, together with measurements of hydrocarbon formation by the alga. The influence was tested of the initial nitrogen and phosphorus concentration on the optimum concentration range for a culture in secondarily treated piggery wastewater. A high cell density (> 7 g L⁻¹ d. wt) was obtained with 510 mg L⁻¹ NO₃-N. Growth increased with nitrogen concentration at the basal phosphorus concentration (14 mg P L⁻¹). The growth rate was nearly independent (μ = 0.027 ∼ 0.030 h⁻¹) of the initial phosphate concentration, except under conditions of phosphate deficiency (μ = 0.019 h⁻¹). B. braunii grew well in piggery wastewater pretreated by a membrane bioreactor (MBR) with acidogenic fermentation. A dry cell weight of 8.5 mgL⁻¹ and hydrocarbon level of 0.95 gL⁻¹ were obtained, and nitrate was removed at a rate of 620 mg NL⁻¹. These results indicate that pretreated piggery wastewater provides a good culture medium for the growth and hydrocarbon production by B. braunii.