Abstract
On-line monitoring of wastewater parameters is a major scientific and technical challenge because of the great variability of wastewater characteristics and the extreme physical-chemical conditions that endure the sensors. Wastewater treatment plant managers require fast and reliable information about the input sewage and the operation of the different treatment stages. There is a great need for the development of sensors for the continuous monitoring of wastewater parameters. In this sense, several optical systems have been evaluated. This article presents an experimental laboratory-based approach to quantify commonly employed urban wastewater parameters, namely biochemical oxygen demand in five days (BOD5), chemical oxygen demand (COD), total suspended solids (TSS), and the ratio BOD5:COD, with a visible and short wave near infrared (V/SW-NIR) spectrometer (400–1000 nm). Partial least square regression (PLSR) models were developed in order to quantify the wastewater parameters with the recorded spectra. PLSR models were developed for the full spectral range and also for the visible and near infrared spectral ranges separately. Good PLSR models were obtained with the visible spectral range for BOD5 (RER = 9.64), COD (RER = 10.88), and with the full spectral range for the TSS (RER = 9.67). The results of this study show that V/SW-NIR spectroscopy is a suitable technique for on-line monitoring of wastewater parameters.
Highlights
In recent decades, a large number of wastewater treatment plants (WWTP) has been constructed in response to environmental demands by the societies and the legislation [1]
This study focused on the use of visible and short wave near infrared (V/SW-NIR) spectroscopy to quantify wastewater quality parameters (i.e., BOD5, chemical oxygen demand (COD), and total suspended solids (TSS)) in samples from an urban WWTP, collected at different treatment stages
Chemical oxygen demand was determined with a closed reflux, colorimetric method, and total suspended solids were determined by gravimetry of the increase of weight by the residue retained on a filter dried to a constant weight at 103–105 °C [18]
Summary
A large number of wastewater treatment plants (WWTP) has been constructed in response to environmental demands by the societies and the legislation [1]. The complex succession of unitary operations needs to be sharply operated in order to achieve an effective reduction of pollution In this sense, the most challenging issue is the great variability of wastewater volume and contamination level of the incoming sewage. The operation of a WWTP needs the continuous monitoring of contamination level of incoming wastewater and the effective pollution reduction along each stage of the treatment process. Some traditional wastewater quality parameters include the Biochemical Oxygen Demand within five days (BOD5), Chemical Oxygen Demand (COD) and Total Suspended Solids (TSS). The quantification of these parameters is time consuming and implies a notable continuum cost. A fast, accurate and cost-effective system to continuously monitor wastewater parameters through the treatment process may allow operators to optimize the hydraulic retention times (and associated electrical energy cost) and the doses of reactants for some of the stages (e.g., coagulant-flocculent)
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