Determination of alcohols and volatile organic acids in anaerobic bioreactors for H 2 production by near infrared spectroscopy

Abstract

In recent years, near infrared (NIR) spectroscopy has been investigated as a tool for monitoring anaerobic digesters, but several adversities in its application have been reported. This study proposes the application of NIR for the determination of alcohols and volatile organic acids from H 2 production bioreactors and evaluates different approaches to optimize the prediction models. Partial least squad (PLS) models were developed using samples from anaerobic batch reactors fed with crude glycerol for wastewater treatment. The analytes predicted were: methanol, ethanol, 1-butanol, acetic, propanoic, butyric, isocaproic and total volatile organic acids (VFA). The optimization of the predictive capacity of the models was achieved through the orthogonal signal correction (OSC) preprocessing and the selection of variables performed by the genetic algorithm (GA). The application of the proposed models were based on the following figures of merit: accuracy, precision, linearity, limits of detection and quantitation, measurement interval, sensitivity, selectivity, signal-to-noise ratio and bias. Despite the low selectivity (maximum of 0.12%), the models presented high sensitivity [g À1 ¼ 0.19 (mg L À1) À1 ], low LOQ (1 mg L À1) and correlation between reference and predicted values (r) at least 0.93, except for propanoic acid (r pred ¼ 0.85). The F-test revealed that the selection of variables by GA significantly improved the accuracy and linearity of the prediction models for methanol, acetic acid, isocaproic acid and VFA. NIR spectroscopy has proved to be a powerful tool for monitoring H 2 production bioreactors since provides fast, low cost and multicomponent information.

Phase Separation in Anaerobic Digestion: A Potential for Easier Process Combination?

“…An adequate amount of the effluent from the acidogenesis needs to be transferred to the second (or third) stage in order to prevent starvation in the methanogenic stage without the risk of its acidification. SCCAs can be monitored on-and off line with near or mid-wavelength infrared spectroscopy sensors (Falk et al, 2015;Nespeca et al, 2017). Infrared spectroscopy (Nespeca et al, 2017) or gas chromatography for the detection of volatile compounds (Zheng et al, 2020) has proven to be a suitable strategy for identifying concentration changes of acids in a short time scale (Björnsson et al, 2001), however this is rarely applied in practice so far.…”

Biossistemas integrados na codigestão do glicerol bruto em resíduos agroindustriais para a geração de H2 e CH4

“…A temperatura do forno foi programa inicialmente a 45 °C por 1 minuto seguido de uma rampa de 50 °C min -1 até a temperatura final de 250 °C, mantidos por 3 minutos. Os compostos foram quantificados pelo método de calibração externa [40].…”

Environmentally-friendly technology for rapid identification and quantification of emerging pollutants from wastewater using infrared spectroscopy

“…Nowadays, FTIR techniques are becoming widespread in monitoring wastewater treatment processes. Several parameters can be measured with this technique as alcohols and volatile organic acids (Nespeca et al, 2017), biogas production (Stockl and Lichti, 2018), biochemical oxygen demand, chemical oxygen demand (COD), turbidity, total organic carbon (TOC) and volatile fatty acids (VFA), among others (Mesquita et al, 2017). On the other hand, the quantification of pharmaceuticals, and other emerging pollutants, in wastewaters by FTIR and chemometrics is just starting to have the attention of the scientific community (Quintelas et al, 2019).…”