Cultivation of Desmodesmus multivariabilis for the treatment of cosmetic wastewater

Abstract

The discharge of cosmetic wastewater into the wastewater treatment systems has become an environmental concern due to high concentrations of nutrients. The current study explored the phytoremediation potential of Desmodesmus multivariabilis, under mixotrophic growth, to remove total organic carbon (TOC), sulfur (TS), nitrogen (TN), and phosphorus (TP) from cosmetic wastewater (CWW). The CWW was prepared using samples supplied by a local cosmetic production company (two dyes, two hair relaxers, as well as two shampoos and conditioners). The bioremediation potential of D. multivariabilis was tested under four different conditions: raw CWW with 0% CO2 in the aeration stream (i.e., atmospheric air); pre-treated CWW with 0% CO2, 2.5% CO2, and 5% CO2. Control experiments were run in parallel. Under mixotrophic growth, the microalga performed best at 5% CO2 in the pre-treated CWW where TOC, TN, TP, and TS removal of >88%, >98%, >95%, and >90% were measured, respectively. The corresponding biomass (dry weight) was >203 mg/L. Relaxers promoted growth most prominently; however, it was observed that there was significant nutrient removal even in the absence of growth in all experiments. The growth followed Liebig’s Law, displaying three distinct phases (CO2 concentration, CO2 mass transfer, and nutrient limited growth). The results demonstrated the potential for the successful bioremediation of cosmetic wastewater by D. multivariabilis.