Phycoremediation of cashew nut processing wastewater and production of biodiesel using Planktochlorella nurekis and Chlamydomonas reinhardtii

Abstract

The present study examined the biomass enrichment of two microalgal strains, Planktochlorella nurekis and Chlamydomonas reinhardtii in cashew nut processing wastewater (CNPW) along with the simultaneous production of biofuel as well as wastewater treatment. The strains were initially grown in Bold's Basal Medium (BBM) before being introduced into CNPW under experimental conditions. The physico-chemical parameters, heavy metal concentration and biomass content were analyzed periodically. The produced biomass was used for the production of biodiesel and the Fatty acid methyl esters (FAME) of the biodiesel were estimated along with its quality. The results of the study revealed a significant improvement in the quality of CNPW within 13 days. P. nurekis (1.914 ± 0.02 g/L) showed higher biomass production than C. reinhardtii (1.503 ± 0.069 g/L). The physico-chemical analysis showed that P. nurekis and C. reinhardtii could significantly reduce nitrate, phosphate and COD from CNPW. The percentage reduction of heavy metals such as Cd, Cr, Ni, Cu and As were 93.2 %, 99.7 %, 98.7 %, 99 % and 90.6 %, respectively when treated with P. nurekis. Similarly, the percentage reduction of the aforesaid heavy metals by C. reinhardtii were 75.7 %, 65.9 %, 72.5 %, 78.5 % and 87.4 % respectively. The FTIR analysis revealed the presence of the functional groups such as amines, alkenes, carboxylic acid, phenol, nitro compound, amide and alcohols in both strains. The FAME profile of both strains showed a moderate concentration of C16–C18 fatty acids content. The quality analysis of biodiesel produced by both species revealed that all the physical properties were within the permissible limits as per ASTM D6751–02 and EN 14214. Comparatively, P.nurekis exhibited notable phycoremediation capacity as well as lipid production potential than C. reinhardtii. The present study has shown that both species are the promising candidates for wastewater treatment.