Chromium bioremediation from river Yamuna using cyanobacteria at white and red illumination wavelengths

Industrial waste from thermal power plants and tanneries discharged into natural water bodies contaminate water and limit its usage for drinking and irrigation purposes. Heavy metals present in the water are detrimental to health. Removal of such heavy metals is a necessity due to their non-biodegradability in the environment. Chromium (Cr) imparts high toxicity to water in two valence states -Cr (III) and Cr (VI). Microalgae possess a mechanism for uptake of both trivalent and hexavalent Cr and deposit them in the polymeric form of trivalent Cr. This work emphasizes on the process of bio enrichment of Cr (III) in microalgae Spirulina sp. NCIM5143. The first stage involves acclimatizing the strain to high concentrations of Cr (up to 80 mg/L) in the Yamuna River water and Zarrouk's medium used as cultivation media. This was achieved by a serial increase of Cr in the increment of 20 mg/L in each batch. A Cr (III) removal of 88.1% in the Yamuna medium and 87% in the Zarrouk's medium was obtained, whereas a Cr (VI) removal of 74% in the Yamuna medium and 83.1% in the Zarrouk's medium was obtained. A complete removal of 100% was observed when red LED was used along with the production of pigments chlorophyll and phycocyanin. Hence, Spirulina sp. proved to be an excellent scavenger of Cr (III) and Cr (VI) ions and for the production of value-added pigments. Also, Spirulina sp. assisted Cr (III) and Cr (VI) bio sequestration has no detrimental effects on environment.

Automated summary

This study focused on the bio-enrichment of chromium (III) in the microalgae Spirulina sp. NCIM5143, demonstrating its ability to remove both Cr (III) and Cr (VI) ions effectively while producing valuable pigments. The use of red LED lights led to a complete removal of the heavy metals, with the added benefit of pigment production, without detrimental effects on the environment.