Activated sludge process monitoring through in situ near-infrared spectral analysis

Abstract

The application of near infrared (NIR) spectroscopy for industrial process monitoring is achieving increasing importance over the last twenty years. In fact, the real time monitoring capacity of NIR spectroscopy is a very important feature for process monitoring, prediction and control as it allows a fast evaluation of the state of the process. However, the application of NIR spectroscopy in wastewater treatment processes is still to be explored. Although some applications of the technique for wastewater monitoring have been reported in the literature, there is still a need for more investigation related with applications, limitations and advantages of the technique when compared with other methods. An activated sludge reactor for aerobic treatment of a complex medium was monitored in situ with a NIR transflectance probe and traditional chemical parameters analysed off-line. NIR spectrophotometric data measured at the feed, reactor and settler were coupled to principal component analysis (PCA) to infer about the ability of this monitoring system to detect changes in the feed influent. The analysis of the score plots resulting from PCA permitted to identify the moments at which the perturbations occurred and to follow the consequent instability induced in the reactor till the day where the system is recuperated. The promising results obtained, suggest the interest in more detailed studies on the feasibility of NIR spectroscopy as an alternative method for monitoring and control of wastewater treatment processes.

Near infrared spectroscopy as a rapid non-invasive tool for agricultural and industrial process management with special reference to avocado and sandalwood industries

“…NIRS has been shown to successfully measure oil, urea, methanol and glycerol concentrations and solids content of the waste water discharge from biodiesel fuel production processes [20,21]. Preliminary work by Dias et al [19] supports the use of NIRS as an on-line quality monitoring tool for activated sludge reactors to detect changes in the feed influent. These are only a few of the many potential applications of NIRS as a tool in agriculture, waste water and environmental management.…”

“…The real-time monitoring capacity of NIRS is a very important feature for the application to industrial process and waste water monitoring, prediction and control as it would allow fast evaluation of the state of the process [19]. NIRS has been shown to successfully measure oil, urea, methanol and glycerol concentrations and solids content of the waste water discharge from biodiesel fuel production processes [20,21].…”

Estimation of effluent quality parameters from an activated sludge system using quantitative image analysis

“…Partial least squares (PLS) is a widely used statistical technique able to model a given predicted variable and detect deviations [19]. Furthermore, PLS models have been recently used for the estimation of COD, nitrate (NO 3 À ), total organic carbon (TOC), and mixed liquor suspended solids (MLSS) using ultraviolet-visible and near-infrared spectroscopy on wastewater treatment systems [20][21][22]. Despite the prior use of image analysis data, coupled to PLS models, to estimate sludge volume index (SVI) and MLSS [11,12,15], QIA has not yet been applied, to our knowledge, neither to estimate the COD removal ability nor nitrification/denitrification occurrence.…”

On-Line Measurement of the Chemical Oxygen Demand in Wastewater in a Pulp and Paper Mill Using Near Infrared Spectroscopy

“…The studies found represent quite diverse applications, for instance, quantitative measurements of oil, urea and solids [5], glycerol [6], and methanol and glycerol simultaneously [7] in wastewater from a biodiesel fuel production plant. As another example, in one of the few in-situ applications found [8], principal component analysis (PCA) was used instead of quantitative modelling to monitor an activated sludge plant.…”