Study On Cr(?) Removal From Industrial Wastewater By Heterotrophic Microalgae

Microalgae is a prominent means of wastewater treatment.Both living and dead microalgal biomass has been described worldwide following their potency to remove toxic heavy metals from wastewater.Among these toxic heavy metals,Cr(?)is a serious threat for human health as well as water systems when it crosses the standard limit.Considering the importance of removing toxic Cr(?)from practical wastewater containing complex pollutants,this study presented for the first time the use of live heterotrophic microalgae(Botryocossuss sp.NJD-1)in presence of different organics(sodium acetate,ethanol,methanol)and assessed its capacity for bioremoval of Cr(?)along with growth.Besides,the concurrent removal of TOC,N-NO3 and P-PO4 was examined through comprehensive experiments.The results showed that the Cr(?)removal efficiency descended in the culture with sodium acetate,ethanol and methanol,sequentially.The best removal efficiencies were achieved in the culture with 5 mg L-1 of initial Cr(VI)and sodium acetate of equivalent to 2.92 g L-1 initial carbon concentration,i.e.,93.22%,98.23%,66.89%and 99.21%for Cr(VI),TOC,NO3-N and PO4-P,respectively.Combing the mass balance calculation and characterization,the fate of Cr(VI)and Cr(?)was tracked and quantified in the culture system,which indicates that 87.17%of initial Cr(?)converted into Cr(?)and settled in algal biomass for the best removal experiment.Different patterns of Cr(VI)removal and conversion efficiency from different carbon source cultures indicates the biological correlation between assimilation process of Cr(?)and intracellular metabolic activity influenced by these carbon sources.Consequently,the mechanism demonstrating the correlation between the removal pr.ocess of Cr(?)and the microbial activity influenced by organics was proposed.Based on reasonable performance and in-depth analysis,this study thereby affirms that heterotrophic microalgae is a promising way for advanced biological treatment of Cr(?)in organics co-contaminated industrial wastewater.