Carbon dioxide capture and nutrients removal utilizing treated sewage by concentrated microalgae cultivation in a membrane photobioreactor

A highly efficient microalgae cultivation process was developed for carbon dioxide capture using nutrients from treated sewage. A submerged-membrane filtration system was installed in a photobioreactor to achieve high nutrient loading and to maintain a high concentration and production of microalgae. Chlorella vulgaris, Botryococcus braunii and Spirulina platensis were continuously cultivated with simulated treated sewage and 1%-CO2 gas. The optimum hydraulic retention time (HRT) and solids retention time (SRT) were explored to achieve the maximum CO2 capture rate, nutrient removal rate and microalgae biomass productivity. The carbon dioxide capture rate and volumetric microalgae productivity were high when the reactor was operated under 1-day (HRT) and 18-days (SRT) conditions. The independent control of HRT and SRT is effective for efficient microalgae cultivation and carbon dioxide capture using treated sewage.