Measurement of the Glycerol Concentration during the Microbial Treatment of the Wastewater from the Biodiesel Fuel Production Plant Using near Infrared Spectroscopy

Abstract

Biodiesel fuel (BDF) made from edible oil or its waste is widely used as a renewable and environmentally friendly energy source. The crude BDF produced with alkali catalyst is washed with water to remove a by-product, glycerol. The BDF wastewater discharged from this washing process has to be appropriately treated. The microbial treatment of the BDF wastewater is promising because glycerol is difficult to separate from the BDF wastewater. The addition of some nutrients is essential for the efficient microbial treatment of the BDF wastewater. Measurement of the glycerol concentration in the microbial-treated BDF wastewater is very important because the amount of nutrients which should be added depends on the glycerol concentration. The prediction of the glycerol concentration in the BDF wastewater using near infrared (NIR) spectroscopy was investigated. Oil degradable yeast and some nutrients were added to the BDF wastewater. The microbial-treated wastewater was used as the source for calibration and validation set samples. Calibration equations relating the NIR spectral data to the glycerol concentration measured with the enzymatic method were obtained. The prediction of the glycerol concentration was successfully carried out using NIR spectroscopy regardless of the presence or absence of the microbial cells. A good result was observed for the calibration equation made with optical data in the presence of the microbial cells at the wavelengths of 2264 nm and 1052 nm. This result suggests that the glycerol concentration in the microbial-treated BDF wastewater can be predicted even in the presence of the microbial cells. The simple, rapid and on-line prediction of the glycerol concentration in the BDF wastewater using NIR spectroscopy will allow more efficient microbial treatment of the BDF wastewater.