On‐line biodegradation monitoring of nitrogen‐containing compounds by membrane inlet mass spectrometry

Membrane inlet mass spectrometry (MIMS) has been developed for the on‐line monitoring of compounds in a continuous stirred tank bioreactor (CSTB) used to simulate a wastewater treatment plant (WWTP). A mixture of four industrially relevant nitrogen‐containing volatile and semi‐volatile compounds was fed to a 3 dm³ CSTB with a hydraulic retention time (HRT) of 24 h. In‐membrane preconcentration/thermal desorption was used for the on‐line monitoring of semi‐volatile compounds (n‐methylpyrrolidinone and tetramethylethylenediamine), while volatile organic compounds (3‐bromopyridine and 2‐chloro‐5‐trifluoromethylaniline) were determined by continuous infusion through the membrane. Quantification of the four compounds was achieved by MS. The CSTB was run for 160 h and, after reaching steady state, n‐methylpyrrolidinone showed removal to levels below the limit of detection, while there was partial biodegradation of 2‐chloro‐5‐trifluoromethylaniline and 3‐bromopyridine. There was no evidence of significant biodegradation for tetramethylethylenediamine. Intermediates in the metabolite pathways of 2‐chloro‐5‐trifluoromethylaniline and 3‐bromopyridine were identified by MIMS, gas chromatography/mass spectrometry (GC/MS) or liquid chromatography/mass spectrometry (LC/MS). COD was measured off line, and results agreed well with MIMS, although COD data did not provide information on the removal of the individual compounds. Copyright © 2003 Society of Chemical Industry     

In‐process rheological monitoring of extrusion‐based polymer processes

Since rheology is very sensitive to the structure and macromolecular conformation of polymer systems, rheological measurements performed in situ during extrusion are attractive for monitoring the process. After introducing the concepts of in‐process monitoring during extrusion operations, the benefits of rheology for assessing filler dispersion in polymer composites, morphology development in polymer blends or the extent of chemical reaction in reactive extrusion are briefly reviewed. Then, in‐process rheological tools are reviewed. For each device, the information conveyed is detailed. © 2020 Society of Industrial Chemistry     

Monitoring wastewater BOD using a non‐specific sensor array

An electronic nose incorporating a non‐specific sensor array of 12 conducting polymers was evaluated for its ability to monitor wastewater samples. Sewage samples collected from the inlet works, settlement tank and final effluent outlet over 5 months (January–May) were used to correlate the sensor responses of these samples with their corresponding 5‐day biochemical oxygen demand (BOD) values. Canonical correlation analysis (a linear reduction technique) showed that the relationship between the sensor responses and BOD over the 5 months was non‐linear. However, the separate analyses of subsets of these samples for shorter time periods showed that a linear relationship is apparent for time periods of 4 weeks or less, suggesting a correlation window occurs between the sensor responses and BOD. Preliminary neural network analysis supported these observations and using a three‐layer back‐propagation network showed that it is possible to predict BOD values from electronic nose analysis of a wastewater sample. The findings suggest that electronic nose technology could be used for the non‐invasive monitoring and/or control of a wastewater treatment process. © 1999 Society of Chemical Industry     

In‐line and in situ monitoring of semi‐batch emulsion copolymerizations using near‐infrared spectroscopy

This article shows that near‐infrared spectroscopy (NIRS) can be used efficiently for the simultaneous in‐line and in situ monitoring of monomer (methyl methacrylate, MMA, and butyl acrylate, BuA) and polymer concentrations in the reaction medium during seeded semibatch emulsion copolymerizations. A series of actual reaction experiments was planned to allow the proper obtainment and selection of calibrating samples. Partial least squares (PLS) was used to build three independent calibration equations in the range of 1100–1900 nm, which were used to successfully monitor some disturbed reactions in‐line. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2670–2682, 2002     

On‐line control of crystal properties in nonisothermal antisolvent crystallization

The issues regarding the design and implementation of on‐line optimal control strategies of crystal properties in nonisothermal antisolvent crystallization processes to control particles’ mean size and standard deviation are dealt. The one‐dimensional Fokker–Planck equation is used to represent the dynamic characteristics of the crystal growth and generate iso‐mean and iso‐standard deviation curves. Using controllability tools it is demonstrated that the system is ill conditioned in the whole operational range, posing limitations on the achievable control performance. To circumvent the problem, a control strategy is formulated by pairing crystals’ mean size with antisolvent feed rate and manipulating temperature to control the standard deviation. A novel digital image‐texturing analysis approach is discussed and implemented to track crystals’ size distribution along the experiment and providing the on‐line information for further feedback control action. Subsequently, alternative control strategies are implemented and tested to achieve a desired crystal size distribution. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2188–2201, 2015     

On‐line optimizing control of bulk polymerization of methyl methacrylate: Some experimental results for heater failure

An experimental unit has been assembled to carry out on‐line optimizing control of the bulk polymerization of methyl methacrylate (MMA). A rheometer‐reactor assembly is used. Temperature and viscosity measurements are used to describe the state of the system. The polymerization is carried out under an off‐line computed optimal temperature history, T_op(t). A planned disturbance (heating system failure) is introduced at time t₁. This disturbance leads to a fall in the temperature of the reaction mass. A new optimal temperature history, T_reop(t), is re‐computed on‐line and is implemented on the reaction mass at time t₂, when the heating is resumed. This procedure helps ‘save the batch’. A genetic algorithm is used to compute this reoptimized temperature history in a short period of ～2 min of real time. The feasibility of the on‐line optimizing control scheme has been demonstrated experimentally. Replicable results for the viscosity history, η(t), of the polymerizing mass under several non‐isothermal conditions have been obtained. These experimental results are quite trustworthy, even though the model predictions are only in approximate agreement with them, perhaps because of the extreme sensitivity of results to the values of the model parameters. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2350–2360, 2002     

Semi‐specific biosensors for measuring BOD in dairy wastewater

BACKGROUND: Semi‐specific microbial biochemical oxygen demand (BOD) biosensors were constructed using living cells of Escherichia coli R17.1.3 (E. coli) and Raoultella terrigena P74.3 (R. terrigena) immobilized in agarose gel matrix. The research involved comparison with the Pseudomonas fluorescens P75 (P. fluorescens) biosensor that had no specificity in decomposing lactose and milk derivates. The constructed BOD biosensors were calibrated with OECD synthetic wastewater and tested with different wastewater samples. RESULTS: The linear range of the calibration curve was 5–200 mg L^?1 BOD₇ for R. terrigena and P. fluorescens based biosensors and 150 mg L^?1 BOD₇ for the E. coli based biosensor. Service life was 60 days for E. coli and P. fluorescens based biosensors and 40 days for R. terrigena based biosensors. BOD values for dairy industry wastewater obtained with current semi‐specific biosensors considerably overestimate BOD₇, while universal biosensors underestimate BOD₇ obtained by the conventional 7‐day BOD test. CONCLUSION: In spite of extensive overestimation of BOD₇ the semi‐specific biosensors enabled better estimation of BOD in dairy industry wastewater than a reference P. fluorescens biosensor. The best result, in terms of service life, stability, sensitivity and reproducibility was accomplished with semi‐specific E.coli biosensor. Copyright © 2010 Society of Chemical Industry     

Studies on high‐speed melt spinning of noncircular cross‐section fibers. II. On‐line measurement of the spin line,including change in cross‐sectional shape

On‐line measurement was performed in the high‐speed spinning of flat, hollow, and circular fibers of poly(ethylene terephthalate), paying particular attention to the change in cross‐sectional shape along the spin line. The diameter profiles of hollow and circular fibers were essentially identical, whereas the deformation of flat fiber shifted to the region closer to the spinneret. The necklike deformation of hollow and circular fibers started at the takeup velocity of 5 km/min. In the case of flat fibers, presence of the necklike deformation was confirmed at 4 km/min, and extremely steep diameter attenuation was observed at 5 km/min. The spin‐line tension of the flat fiber was also larger than that of circular fibers. Combined measurements of fiber velocity and thickness enabled us to evaluate the aspect ratio of the flat fiber and hollow ratio of the hollow fiber in the spin line. These two factors were found to decrease steeply near the spinneret. Accordingly, the thinning of the spin line and the change in cross‐sectional shape appeared to proceed independently. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1582–1588, 2001     

Mid‐infrared spectroscopy as a tool for real‐time monitoring of ethanol absorption in glycols

Fast, simple, accurate, and inexpensive methods for obtaining analyte concentration data are desirable in the industrial sector. In the present study, the use of Fourier transform mid‐infrared (FT‐MIR) spectroscopy, combined with partial least squares (PLS) regression, was investigated as a tool for real‐time monitoring of processes of ethanol absorption in glycols. Calibration was performed using simple synthetic samples containing ethanol, water, and monoethylene glycol (MEG) or diethylene glycol (DEG). The PLS models presented excellent performance, with correlation coefficients (R²) close to unity and root‐mean‐square errors of cross‐validation (RMSECV) and prediction (RMSEP) lower than 2% of the calibration data ranges for both analytes (ethanol and water) in both absorbents (MEG and DEG). The monitoring technique developed has potential to be applied in absorption processes and could also be used in other large‐scale unit operations, providing information in real time and enhancing process control.     

On‐line optimization of free radical bulk polymerization reactors in the presence of equipment failure

An on‐line optimizing control scheme has been developed for bulk polymerization of free radical systems. The effects of random errors, as well as one kind of a major disturbance (heating system failure), have been studied. A model‐based, inferential state estimation scheme was incorporated to estimate, on‐line, the parameters of the model (and thereby, the monomer conversion and molecular weight of the polymer) using experimental data on temperature and viscosity. A sequential quadratic programming technique was used for this purpose. A major disturbance, such as heating system failure, leads to a deteriorated final product unless an on‐line optimal temperature trajectory (history) is recomputed and implemented on the reactor. Genetic algorithm was used for this purpose. It has been found that, if the “sensing” of the major temperature deviation from the optimal value and rectification of the heating system is achieved well in advance of the onset of the Trommsdroff effect, use of a reoptimized temperature history is sufficient to produce the desired product without significantly altering reaction time. However, if such a disturbance occurs late, a single‐shot intermediate addition of an optimal amount of initiator needs to be used in addition to changing the temperature history to produce polymers having the desired properties in the minimum reaction time. Other types of failures can similarly be handled using the methodology developed. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 2101–2120, 1999     

On‐line determination of the conversion in a styrene bulk polymerization batch reactor using near‐infrared spectroscopy

A fast on‐line method for measuring the monomer conversion of a styrene batch polymerization reaction with near‐infrared spectroscopy (NIR) has been developed. Multivariate calibration was performed, using polymer samples having temperatures around the set point of the batch reactor (75–85°C) and monomer conversions up to 35%. The calibration model was built in such a way that the effect of the temperature on the predicted conversion of the sample was minimized. The method was validated in a number of batch runs. In these runs, the batch temperature and molar mass distributions of the polymer were varied. At‐line size‐exclusion chromatography was used as a reference method for measuring the monomer conversion. Results show that on‐line conversion monitoring with NIR offered overall an excellent accuracy (～ 0.32% conversion). For high and low monomer conversions a small bias in the predicted conversion is present. The method proved to be insensitive to both relative large changes (10°C) of the batch temperature and to considerable changes of the molar mass distribution of the polymer. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 90–98, 2002; DOI 10.1002/app.10241     

On‐line acoustic attenuation spectroscopy of emulsions stabilized by vinyl alcohol–vinyl acetate copolymers: a model system for the suspension polymerization of vinyl chloride

BACKGROUND: Poly[(vinyl alcohol)‐co‐(vinyl acetate)] (PVA) copolymers obtained by partial hydrolysis of poly(vinyl acetate) are currently used as industrial stabilizers in the suspension polymerization of vinyl chloride monomer (VCM). Their molecular characteristics, mainly the average degree of hydrolysis (DH ) and average degree of polymerization (DPw ), have a major influence on the monomer droplet size and the properties of the final poly(vinyl chloride) resin. RESULTS: The average droplet size and size distribution of chlorobutane/water emulsions, as a model system for VCM/water emulsions, were studied using acoustic attenuation spectroscopy on‐line with an agitated laboratory reactor. The emulsions were stabilized by PVA with DH values between 73 and 88 mol% and DPw values between 450 and 2500. The effects of agitation speed, stirring time and concentration of the PVA copolymers were investigated. An attempt was made to correlate the interfacial tension and the droplet size. CONCLUSION: On‐line acoustic spectroscopy appears to be a suitable technique for the real‐time control of the droplet size of monomer suspensions. The advantages and limitations of the technique are outlined. The validity and the application limits of the commonly cited correlation between the droplet size and the Weber number are established for polymeric surfactant‐stabilized emulsions. Copyright © 2009 Society of Chemical Industry     

In‐line near‐infrared spectroscopy: A tool to monitor the preparation of polymer‐clay nanocomposites in extruders

In‐line diffuse reflectance and on‐line transmission near‐infrared spectroscopy (NIR) measurements are performed at the same location of the barrel of a twin screw extruder during the preparation of a polypropylene/clay nanocomposite. Their performance is evaluated by means of a 7‐parameter chemometric model using off‐line rheological and structural (FTIR) data obtained from samples prepared under different screw speed, compatibilizer content and clay loading, as well as a process‐related thermomechanical index. Despite the higher variability of the diffuse reflectance signal, the two models present analogous high quality indices. The aptness of the reflectance measurements is thus validated, which has direct practical advantages, as this probe can be fixed in any typical melt pressure transducer port. The probe is then used for the real‐time in‐line monitoring of the production of the same nanocomposite but now using different throughputs, and the chemometric‐based predictions are compared with experimental off‐line characterization data. The nonlinear effect of throughput is correctly anticipated. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Two‐dimensional fluorescence as a fingerprinting tool for monitoring wastewater treatment systems

BACKGROUND: The use of two‐dimensional (2D) fluorescence for monitoring complex biological systems requires careful assessment of the effect of chemical species present, which may be fluorescent and/or may interfere with the fluorescence response of target fluorophores. Given the complexity of fluorescence data (excitation emission matrices—EEMs), the challenge is how to recover the information embedded into those EEMs that can be related quantitatively with the observed performance of the biological processes under study. RESULTS: This work shows clearly that interference effects (such as quenching and inner filter effects) occur due to the presence of multiple species in complex biological media, such as natural water matrices, wastewaters and activated sludge. A statistical multivariate analysis is proposed to recover quantitative information from 2D fluorescence data, correlating EEMs with the observed performance. A selected case study is discussed, where 2D fluorescence spectra obtained from the effluent of a membrane bioreactor were compressed using PARAFAC and successfully correlated with the effluent chemical oxygen demand, using projection to latent structures modelling. CONCLUSION: This study demonstrates the potential of using 2D fluorescence spectroscopy as a status fingerprint. Additionally, it is shown how statistical multivariate data analysis can be used to correlate EEMs with selected performance parameters for monitoring of biological systems. Copyright © 2011 Society of Chemical Industry     

Treatment of coking wastewater by a UBF‐BAF combined process

BACKGROUND: Coking wastewater is a major pollutant, produced in large quantities in many countries worldwide. This study investigates the performance of a combined system for treating coking wastewater. The system is based on an upflow blanket filter (UBF) with a biological aerated filter (BAF). Efficiency is assessed according to organic pollutants and nitrogen removal. RESULTS: It was found that hydraulic retention time (HRT) had a greater influence on the removal efficiency of NH₃‐N than chemical oxygen demand (COD). The BAF facilitated simultaneous carbonaceous removal and nitrification, depending on the reactor height. The system removed 81.5% of COD and 96.4% of NH₃‐N when the total HRT was 46.7 h (15.4 h for UBF and 31.3 h for BAF). Gas chromatography/mass spectrometry analysis indicated that the main components of the coking wastewater were phenols and nitrogenous heterocyclic compounds. Certain refractory compounds decomposed in the anaerobic section, resulting in the production of intermediates. Although most organics present in the influent were absent from the final effluent, a few residual contaminants could not be fully eliminated by the system. CONCLUSION: The experimental results show that the present system is feasible for the treatment of coking wastewater. Copyright © 2007 Society of Chemical Industry     

Monitoring of an industrial wastewater plant employing finite‐time convergence observer

In this paper, the estimation of non measured variables (bioreactor biomass and settler biomass concentrations) is addressed. The plant is subjected to sudden step disturbances on the inlet oxygen flow, such that an observer with finite‐time convergence is required, to maintain adequate estimation performance. The observer structure contains a fractional power of the estimation error which is proposed to ensure the convergence properties needed. Under the assumptions considered, a mathematical analysis is performed to demonstrate the convergence of the estimation error and the convergence time is also calculated. The performance of the observer is illustrated with numerical experiments and compared with standard nonlinear Luenberger observer. Copyright © 2006 Society of Chemical Industry