Quantitative monitoring of an activated sludge reactor using on-line UV-visible and near infrared spectroscopy

The performance of an activated sludge reactor can be significantly enhanced through use of continuous and real-time process-state monitoring, which avoids the need to sample for off-line analysis and to use chemicals. Despite the complexity associated with wastewater treatment systems, spectroscopic methods coupled with chemometric tools have been shown to be powerful tools for bioprocess monitoring and control. Once implemented and optimized, these methods are fast, nondestructive, user friendly, and most importantly, they can be implemented in situ, permitting rapid inference of the process state at any moment. In this work, UV-visible and NIR spectroscopy were used to monitor an activated sludge reactor using in situ immersion probes connected to the respective analyzers by optical fibers. During the monitoring period, disturbances to the biological system were induced to test the ability of each spectroscopic method to detect the changes in the system. Calibration models based on partial least squares (PLS) regression were developed for three key process parameters, namely chemical oxygen demand (COD), nitrate concentration (N-NO3−), and total suspended solids (TSS). For NIR, the best results were achieved for TSS, with a relative error of 14.1% and a correlation coefficient of 0.91. The UV-visible technique gave similar results for the three parameters: an error of ~25% and correlation coefficients of ~0.82 for COD and TSS and 0.87 for N-NO3−. The results obtained demonstrate that both techniques are suitable for consideration as alternative methods for monitoring and controlling wastewater treatment processes, presenting clear advantages when compared with the reference methods for wastewater treatment process qualification.Fundação para a Ciência e Tecnologia (FCT) - PPCDT/AMB/60141/2004, bolsa de doutoramento SFRH/BD/32614/200

Application of Ultraviolet (UV) spectrophotometry in the assessment of membrane bioreactor performance for monitoring water and wastewater treatment

Ultraviolet (UV) spectroscopy has been widely used in monitoring water and wastewater treatment. In this study UV spectroscopy was used to investigate fouling development on the membrane surface of membrane bioreactors. The chemistry of mixed liquor present in the membrane bioreactor and the foulant deposited on the membrane surface was compared by analyzing the UV spectra. The mixed liquor showed different spectra than did the foulant. The foulant spectra showed a shift in absorbance peaks with operation time. The particle size distribution

Properties of natural microlayers on Australian freshwater storages and their potential to interact with artificial monolayers

Microlayers are natural surface films derived from hydrophobic organic compounds that form on most lakes and streams. Holoarctic brown water lakes have been most commonly studied, with Australian research limited to marine microlayers. Artificial monolayers based on long-chain fatty alcohols have been applied to freshwater storages to reduce evaporative loss. As a water conservation strategy, monolayer technology was not widely adopted due to variable field performance. However, the role of natural microlayers in reducing monolayer performance has not previously been investigated. In this study, microlayer and subsurface samples from six water storages in Queensland were characterized for water quality indices including biochemical oxygen demand, permanganate index and ultraviolet light absorbance. Microlayer enrichment in southeast Queensland is comparable to or higher than holoarctic lakes. Results indicate that microlayer compounds have the potential to disrupt monolayers in at least three ways: As substrates for microbes capable of degrading monolayer compounds, as chromophores accelerating photodegradation, and as impurities disrupting the molecular packing required to reduce evaporative loss. The knowledge gained from studying natural microlayers can also be used to benchmark novel monolayer compounds, to minimize their environmental impact on freshwater ecosystems

Comparison of marine and river water humic substances in a Patagonian environment (Argentina)

Structural aspects of humic substances (HSs) in marine waters of Engaño Bay (Atlantic Ocean) and water from the Chubut River (Patagonia, Argentina) were compared. The HSs were isolated, purified, and analyzed using a multiple-method approach for structural characterization: elemental analysis, nuclear magnetic resonance (13C and 1H NMR), infrared spectroscopy (FTIR), UV-visible absorption and fluorescence. Similarities between the marine and freshwater components were evaluated on the basis of N and O contents, H/C and C/N atomic ratios, infrared bands from nitrogen-containing and carboxylic groups, percentage of functional groups obtained from NMR spectra, spectral slope coefficient of absorption spectra, absorbance ratios at 250 and 365 nm (E2/E3), aromaticity, excitation–emission matrices and fluorescence quantum yield. Both the Engaño Bay and Chubut River waters have HSs that are mainly composed of fulvic acids (FAs); although they are very similar, they may be distinguished from one another. Similarities include the predominance of aliphatic carbon content (low aromatic content); however, the water bodies differed in their content of proteins and carboxylic acids. The Engaño Bay FAs have mainly an aquatic origin; although the Chubut River FAs suggest a similar aquagenic origin, there is also evidence of contributions from pedogenic FAs.Fil: Scapini, Maria del Carmen. Universidad Nacional de la Patagonia; ArgentinaFil: Conzonno, Victor Hugo. Universidad Nacional de la Plata. Facultad de Ciencias Naturales y Museo. Laboratorio de Investigacion en Sistemas Ecologicos y Ambientales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Balzaretti, Vilma Teresa. Universidad Nacional de la Patagonia; ArgentinaFil: Fernandez Cirelli, Alicia. Universidad de Buenos Aires. Facultad de Ciencias Veterinarias. Centro de Estudios Transdisciplinarios del Agua; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin