Integrated Haematococcus pluvialis biomass production and nutrient removal using bioethanol plant waste effluent

Abstract

Abstract The integrated system of astaxanthin and microalgal biomass production, and wastewater treatment is a promising process. Haematococcus pluvialis is a suitable microalgae for this coupled system to achieve this dual purpose in a single approach. In this study, biomass production and nutrient removal from bioethanol plant wastewater by H. pluvialis were investigated. An air-lift photobioreactor was used to utilize the wastewater as well as a CO2-enriched gas supply. The maximum biomass density and maximum specific growth rate achieved were 4.37 ± 0.007 g/L and 0.317 day−1, respectively, by culturing H. pluvialis in an air-lift photobioreactor, supplemented with 5% CO2 in air. Removal of 91.7% total nitrogen and 100% total phosphorous from the wastewater was achieved. The residual microalgal biomass, obtained after astaxanthin extraction (1.109 ± 0.009 mg/g DW), was characterized as a potential bioenergy feedstock due to its elevated higher heating value 15.6 ± 0.01 MJ/kg. Hence, integrating H. pluvialis cultivation with bioethanol effluent serves the combined purpose of wastewater treatment, CO2 utilization, and simultaneous production of astaxanthin, which has a potential market value of over USD 2000 per kg, and carbohydrate rich microalgal biomass, which can be applied to bioenergy production.