Optimization of nutrients from wastewater using RSMfor augmentation of Chlorella pyrenoidosa with enhanced lipid productivity, FAME content, and its quality assessment using fuel quality index

This experimental study was framed with an objective to optimize the nutrients ((dairy industry wastewater (DIWW), nitrate (NO3-), and phosphate (PO4-3)) using response surface methodology (RSM) with Chlorella to investigate biomass and lipid with FAME content. Quality of obtained bio-oil was also indexed on scale of fuel quality parameters. Three variables were tested with 20 interactions between these variables, and their affects were statistically studied using central composite design. Biomass and lipid concentration with FAME content varied between 0.59 to 1.54 g L-1, 19.81 to 34.54%, and 69.32 to 82.78%, respectively, for different combinations of operating variables. Interactive effects of combined nutrients were also studied in combination, and the best biomass and lipid productivity was noticed with NO3-+PO4-3 in comparison to others, whereas the best FAME content (85.23%) was observed with DIWW+NO3. FTIR analysis showed variation in the spectra with different selected combinations with 1.7-fold increase in the lipid content in respect to control. Qualitative assessment of parameters ranges in between 0.74 and 1.01 mg KOH/g for acid value (AV), 152.34-187.24 mg KOH/g for saponification value (SV), 135.39-143.95-mg I-2/100 g oil for iodine value (IN), whereas cetane value (CN) was found in between 43.06 and 50.31 and higher heating values (HHVs)) almost 45 MJ kg(-1). Crude bio-oil's quality was compared with the fuel quality index (FQI), where S-4 quality sample (59.12) was found significantly compatible with the commercial biodiesel.