Chlorella stigmatophorafor Urban Wastewater Nutrient Removal and CO2Abatement

Abstract

Batch experiments were performed to study biomass growth rate, nutrient removal and carbon dioxide bio-fixation of the marine microalgae Chlorella stigmatophora. Four different cultures at different salinities were tested: wastewater (WW), synthetic wastewater (SWW), seawater (SW) and diluted seawater (DSW). Experimental results showed that Chlorella stigmatophora grew satisfactorily in all culture media, except in SWW where inhibition occurred. In all cases, biomass experimental data were fitted to the Verlhust Logistic model (R² > 0.982, p ≤ 0.05). Maximum biomass productivity (P_bmax ) and CO₂ biofixation (P_vCO2) were reached in the WW medium, 1.146 g SS·L⁻¹·day⁻¹ and 2.324 g CO₂·L⁻¹·day⁻¹ respectively. The order of maximum specific growth rates (μ_max) was WW >DSW>SW. In order to compare nitrogen and phosphorous removal kinetics, an estimation of the time required to reach the most restrictive concentration of total N and P in effluents as defined in the Directive 98/1565/CE (10 mg ΣN·L⁻¹ (T_{10( N)}) and 1 mg ΣP·L⁻¹ (T_1(P) ) was performed. In the WW test T_{10( N)} and T_1(P) needed were of 45.15 and 32.27 hours respectively and at the end of the experimental the removal was in both 100%.