Acclimatization of microalgae Arthrospira platensis for treatment of heavy metals in Yamuna River

Bioaccumulation and biosorption in microalgae are effective approaches for the removal of heavy metals(HMs)from river water.The objective of this study was to investigate the potential for use of acclimatized microalgae in the removal of HMs from the Yamuna River water as an acclimatizing medium.An active culture of Arthrospira platensis(A.platensis)was acclimatized to HMs up to a concentration of 100 mg/L.It was gradually exposed to increasing concentrations of HMs in five subsequent batches with a step increase of 20 mg/L to acclimatize live cells in the simulated Yamuna River water.The presence of high levels of HMs in the Yamuna River water caused growth inhibition.An empirical growth inhibition model was developed,and it predicted high threshold concentrations of HMs(210.7e424.5 mg/L),producing a positive specific growth rate of A.platensis.A.platensis also showed high average removal efficiencies of HMs,including 74.0%for Cu,77.0%for Cd,50.5%for Ni,76.0%for Cr,76.5%for Pb,and 63.5%for Co,from HMs-enriched Yamuna River water.The findings demonstrated that the maximum specific removal amounts of Cu,Cd,Ni,Cr,Pb,and Co were 54.0,58.0,39.0,62.8,58.9,and 45.3 mg/g,respectively.The maximum yields of the value-added products chlorophyll and phycocyanin were 2.5 mg/g(in a batch of 40 mg/L for Cd)and 1054 mg/g(in a batch of 20 mg/L for Cu),respectively.Therefore,acclimatized A.platensis was proven to be a potential microalga not only for sequestration of HMs but also for production of valuable pigments.