Feasibility of the Hybrid Use of Chlorella vulgaris Culture with the Conventional Biological Treatment in Urban Wastewater Treatment Plants

Abstract

Currently, most wastewater treatment plants do not meet the legal requirements, especially regarding phosphorus and nitrogen contents. In this work, real primary urban wastewater (P-UW) was used as culture medium for the growth of Chlorella vulgaris. Experiments were carried out in batch photobioreactors at laboratory scale. To determine the maximum nutrient removal levels and the optimal pH value for C. vulgaris growth, the following pH values were studied: 5, 6, 7, 8, 9, 10, and 11. Additionally, two control experiments were conducted using UW and tap water at the same conditions but without microalgae inoculation. The operational conditions were agitation rate = 200 rpm, T = 25 °C, aeration rate = 0.5 L/min, and continuous light with illumination intensity = 359 µE m−2 s−1. Significant higher growth was obtained at pH = 7. The direct use of C. vulgaris for P-UW treatment demonstrated high removal percentages of organic (COD and BOD5 removal = 63.4% and 92.3%, respectively) and inorganic compounds (inorganic carbon removal = 99.6%). The final biomass was characterized by an accumulation of high energetic compounds, mainly carbohydrates, which ranged between 63.3% (pH = 5) and 82.8% (pH = 11) and represent a source of biofuels. These new achievements open up the possibility of new horizons in urban wastewater treatment.

Impact of Various Visible Spectra on Attached Microalgal Growth on Palm Decanter Cake in Triggering Protein, Carbohydrate, and Lipid to Biodiesel Production

“…In this context, the microalgae favored lipid production and accumulation over growth, as shown by the lowest microalgal density and productivity being found under green light irradiation (Figure 1). This primarily stemmed from the green light being reflected the most, which subjected the microalgal cells to light limitation stress [26]. Accordingly, the microalgae received an inadequate level of photon fluxes for cell growth, thus, inducing the lipid to be stored instead of using them as energy for microalgal cell proliferation.…”

Special Issue on “Biodiesel Production Processes and Technology”

“…Within the field of the production of third-generation biodiesel, Belaiba et al studied the feasibility of using cultures of the green microalga Chlorella vulgaris (concentrations up to 3.5 g/dm 3 ) as a secondary treatment instead of, or in parallel with, the traditional aerobic biological reactor currently used in wastewater treatment plants [5]. At the end of the process, these authors obtained a biomass composed mainly of carbohydrates (63.3-82.8%) and proteins (8.1%-21.9%), which could be transformed into biofuels, including biodiesel.…”