Dynamic Process Conditions Research Articles

Comprehensive characterization of recombinant Pichia pastoris using dynamic process conditions and process analytical technology

HRP_ FB I HRP_FB II HRP_B II Fig 3. Induction by methanol pulses in a batch culture. Cells were grown using D-glucose as C-source. When the substrate was exhausted, induction of protein expression was carried out by successive pulses of methanol: 1 adaptation pulse with 0,5 % methanol (in gray), successive pulses with 1 % methanol (in orange) and 1 pulse with 2 % methanol (not shown). The on-line calculated carbon dioxide evolution rate (CER) and the oxygen uptake rate (OUR) are shown. These calculations were performed by a metabolic balance analyzer implemented on-line. HRP activity was detected both in the absence and in the presence of D-Ala with slightly better results in the latter case, therefore D-Ala was added to the fed-batch cultures.

Effect of Dynamic Process Conditions on Nitrogen Oxides Emission from a Nitrifying Culture

Nitric oxide (NO) and nitrous oxide (N2O) emissions from nitrifying ecosystems are a serious threat to the environment. The factors influencing the emission and the responsible microorganisms and pathways were studied using a laboratory-scale nitrifying reactor system. The nitrifying culture was established at growth rates relevant to wastewater treatment plants (WWTPs). During stable ammonia oxidation, 0.03% of ammonium was emitted as NO and 2.8% was emitted as N2O. Although mixed cultures were used, clear responses in emission of ammonia oxidizing bacteria (AOB) could be detected and it was concluded that the denitrification pathway of AOB was the main source of the emissions. Emissions of nitrogen oxides in the system were strongly influenced by oxygen, nitrite, and ammonium concentrations. Steady state emission levels greatly underestimate the total emission, because changes in oxygen, nitrite, and ammonium concentrations induced a dramatic rise in NO and N2O emission. The data presented can be used as an indication for NO and N2O emission by AOB in plug-flow activated sludge systems, which is highly relevant because of the atmospheric impact and potential health risk of these compounds.

Evaluation of Oxygen Transfer Efficiency under Process Conditions using the Dynamic off-Gas Method

The off-gas method can be used to investigate standard oxygen transfer efficiencies under process conditions (αSOTE) over the operating life of an aeration system. A method to evaluate αSOTE is described in detail by US and German standards. The standards, however, do not describe how to evaluate dynamic changes in αSOTE over a day, which can be useful to uncover problems and unfavourable process conditions. Based on over three years experience gained in off-gas testing in Berlin wastewater treatment plants (WWTPs) under operating conditions, a method to evaluate and interpret the dynamic changes in oxygen transfer is presented. The application of the dynamic off-gas method brings important additional information, which can be used to increase operational efficiency of the aeration basin and to increase process reliability, with a relatively small increase in effort. This paper shows how to perform dynamic measurements under process conditions. Some results of such measurements under dynamic process conditions, performed in a Berlin WWTP, are discussed.

Detecting the Blockage of the Sensing Lines of a Differential-Pressure Flow Sensor in a Dynamic Process Using Wavelet Transform Techniques

The blockage of the sensing lines of a differentialpressure (DP) flow sensor has been found to be the main cause of a malfunction of a flow measurement system in many industrial applications. In this paper, the blockage of the sensing lines under dynamic process conditions is investigated using wavelet transform techniques. The results obtained show that the blockage in a fast changing process is only detectable when the severity of the blockage is over 90%. This outcome differs from that when the sensor operates under a slow varying process. The main reason resulting in the discrepancy between slow and fast varying processes is that a process with high flow rates produces more noise energy in the output of the sensor than a process with low flow rates does. This means that the noise energy generated by the blockage of the sensor under low flow-rate conditions is indistinguishable with that from the output of the sensor working under the sensor normal operating conditions but a process with high flow rates

Analysis of biological wastewater treatment processes using multicomponent gas phase mass balancing.

A reactor system using off-gas analysis was developed for analyzing wastewater treatment process reactions. Using a mass spectrometer for the gas analysis provides the ability to simultaneously measure several gas components (such as oxygen, nitrogen, carbon dioxide, and argon). One of the benefits of the reactor design was the precise control of the dissolved oxygen concentration, uncoupled from the system turbulence, which was controlled via a gas recycle loop. This feature allowed control of the turbulence within the reactor without any need for mechanical stirring. Using oxygen as the test gas, the reactor was shown to perform well in the measurement of oxygen uptake rate of nitrifying activated sludge. The oxygen uptake rate calculations were made using a simple calibration method developed for the reactor system. The reactor was able to provide precise and accurate results for this test case. Furthermore, the system was capable of measuring under dynamic process conditions, as well as when the process rates were constant (steady state).

On-line stoichiometry and identification of metabolic state under dynamic process conditions.

A method for the on-line calculation of conversion rates and yield coefficients under dynamic process conditions was developed. The method is based on cumulated mass balances using a moving average method. Elemental balances were used to test the measured cumulated quantities for gross errors and inappropriate stoichiometry definition followed by data reconciliation and estimation of non-measured conversion rates, using a bioprocess set-up including multiple on-line analysis techniques. The quantitative potential of the proposed method is demonstrated by executing transient experiments in aerobic cultures of Saccharomyces cerevisiae on glucose. Rates and yield coefficients could be consistently quantified in shift-up, shift-down, and accelerostat experiments. The method shows the capability to describe quantitatively transient changes in metabolism including uncoupling of catabolism and anabolism, also for the case when multiple components of metabolism are not measured. The validity of the experiment can be evaluated on-line. Additionally, the method detects with high sensitivity inappropriate stoichiometry definition, such as a change in state of metabolism. It was shown that concentration values can be misleading for the identification of the metabolic state. In contrast, the proposed method provides a clear picture of the metabolic state and new physiological regulations could be revealed. Hence, the novelty of the proposed method is the on-line availability of consistent stoichiometric coefficients allowing a significant speed up in strain characterization and bioprocess development using minimal knowledge of the metabolism. Additionally, it opens up the use of transient experiments for physiological studies.

Autonomous adaptive synchronous machine control

In this paper, we present a design of a new adaptive control system and demonstrate its performance in a computer simulation of nonlinear synchronous machine control. The new design utilizes self-organization and the predictive estimation capabilities of neural-net computing. Real-time adaptation is facilitated by the error-based on-line learning scheme implemented on a cluster-wise segmented associative memory system. It is demonstrated that the neural network system is capable of modelling highly nonlinear systems, detecting changes in the dynamic process conditions and stabilizing the system.

Simultaneous determination of oxygen uptake rate and oxygen transfer coefficient in activated sludge systems by an on-line method

A new on-line method for the measurement of oxygen uptake rate and oxygen transfer coefficient ( k L a eff) in activated sludge systems is introduced. Based on mass balance equations for dissolved oxygen in the aeration basin and a parallel flow-through measuring chamber the system offers a high time resolution and is therefore, especially under dynamic process conditions, of great advantage compared to conventional measurements. The method has been tested and verified at a laboratory plant with variable process conditions, changing activities of microorganisms and variations of loading using a microprocessor. The measurement allows advanced process control in activated sludge systems and may be used in a slightly modified form for a large number of further applications as far as the evaluation of kinetic process parameters or the operation with ion-selective electrodes.