Complete removal of COD from potato processing wastewater by co-cultivation of <i>Haematococcus pluvialis</i> and <i>Gordonia terrae</i>

For efficient removal of COD from the potato processing wastewater, the green alga Haematococcus pluvialis and the bacterium Gordonia terrae were co-cultivated in sterilized wastewater. Results showed that co-cultivation of H. pluvialis and G. terrae enhanced COD removal by promoting cell growth, with the highest removal efficiency (88.9%) on day 12 and removal rate (305.3 mg·L-1·d-1) being achieved at the optimal inoculation ratio of 40:1, increasing 298.6%, 353%, and 159.9%, and 227.6% compared to those of the pure culture of H. pluvialis (22.3%, 67.4 mg·L-1·d-1) and G. terrae (34.2%, 93.2 mg·L-1·d-1), respectively. Supplementation of NaNO3 at the lowest concentration of 0.2 g·L-1 further promoted COD removal efficiency to 100% on day 10. Hence, co-cultivation of H. pluvialis and G. terrae provides an efficient way for complete removal of COD from wastewaters with the suitable COD/nitrogen ratio (C/N) of 8.08.