Oxygen Uptake Rate Measurements Research Articles

Italian Canyoning Guides: Physiological Profile and Cardiometabolic Demand during Rope Activities.

Canyoning activities require physical effort, highlighting the importance of maintaining a proper physical fitness. Canyoning guides emerge as key figures, not only to ensure safety during the experience but also to handle unforeseen situations promptly. This study aims to assess the physiological profile of canyoning guides and the cardiorespiratory demands experienced during rope activities by means of oxygen uptake and heart rate measurements. Seventeen canyoning guides (42.6 y ± 10.78; BMI of 24.0 kg/m2 ± 2.95) carried out coordinative and conditional tests. The participants showed good values in strength tests (27.3 cm ± 5.97 and 23.3 rep ± 8.06 in SJ and PUp tests, respectively), while the flexibility of males and females was below and well above the average, respectively. A noteworthy result was observed in the reaction test, in which a better performance was recorded with the non-dominant hand (168.1 ms vs. 202.0 ms). All subjects exhibited a low aerobic capacity by means of an RD test (10.6 ua ± 6.62). During rope activities and emergency/support simulations, metabolic and cardiovascular data indicated that a moderate/high effort was exerted, confirmed by an oxidative stress analysis. In conclusion, this study demonstrated how canyoning guides face significant physical requirements, but their physiological profile regarding aerobic power was not appropriate. Therefore, these findings could offer valuable insights into the development of specific training to ensure an appropriate aerobic fitness to perform canyoning safely.

Assessment of hybrid fixed and moving bed biofilm applications for wastewater treatment capacity increase – In situ tests in El-Gouna WWTP, Egypt

This paper provides a procedure for comparing the performance of different biofilm carrier medias and their surrounding suspended biomass through oxygen uptake rate (OUR) tests. For in situ (oxygen uptake rate (OUR) measurements, three identical lab scale biofilm reactors were set up at the El Gouna wastewater treatment plant (WWTP). In this setup, two options of media for moving-bed biofilm reactors (MBBR) and one media for fixed-bed biofilm reactors (FBBR) were compared. The WWTP also used the same carrier in a real scale hybrid application to analyze how the interactions between the carrier type and the suspended biomass influences the overall performance. The in situ OUR approach is recommended to measure the contribution of the biofilm fixed biomass under site specific conditions. Specifically, settleability and diffusion limitations are the two opposite poles that cannot be predicted adequately for mild climate conditions based on the literature. A biofilm carrier application can add but actually can also reduce the capacity in a hybrid activated sludge system: The added MBBR-media was able to grind down the sludge flocs forming a poorly settleable suspended biomass. The added FBBR-media can lead to extracellular polymeric substances (EPS) rich biofilms that contribute very little as substrate and oxygen are unavailable for the microorganisms present in the biofilm. In this application of the comparison procedure, Kaldnes K1 like MBBR media was compared with a recycling MBBR carrier option (poly propylene bottle caps) and Jäger Envirotech “BioCurlz™” FBBR media. The study showed higher average rates for the MBBR but decreased settleability. The FBBR showed higher peak rates when flushed to break up the biofilm and well settleable sludge. The determination of OUR per g of volatile solids (SOUR) showed comparable results for all the carriers and in warm conditions, only the capacity to accommodate biomass determines the contribution of the carrier.

COD removal from actual industrial wastewater using a three‐dimensional electrochemical apparatus

AbstractChemical oxygen demand (COD) removal was investigated using a three‐dimensional electrochemical system. The effects of electrode position, pH value, initial temperature, circulation flow, aeration, and addition of hydrogen peroxide on the removal efficiency of the pollutant were studied. The fillers used in the experiment were centimetre‐sized and electrolyte was obtained from an industrial factory with a concentration of COD as high as 25 000–27 500 mg L−1, which was rare in other studies of the past. The degradation of organics was affected by pH and circulation flow, and a decrease in the initial pH value led to the increase in removal efficiency, while a trend of increasing at first and then decreasing was observed with the extension of circulation flow. Aeration and hydrogen peroxide served as enhanced processes for a higher removal rate. Both ultrasound and ultraviolet had effects on the electrolysis system. Oxygen uptake rate measurement and bio‐treatment experiments demonstrated a significant increase in biodegradability with this three‐dimensional electrochemical system. In addition, a pilot scale test in a pharmaceutical factory showed an economic benefit on energy consumption, which was as low as 10 kWh kg−1 COD.

Elimination of oxacillin, its toxicity and antibacterial activity by using ionizing radiation

The chemical changes caused by electron beam and γ irradiations and the biochemical characteristics of degradation products of a frequently used antibiotic oxacillin were investigated and compared with those of cloxacillin by applying pulse radiolysis, chemical and biochemical oxygen demand, total organic carbon content, oxygen uptake rate, toxicity and antibacterial activity measurements. Oxacillin was found to be non-toxic, but poorly biodegradable by the mixed microbial population of the activated sludge of a wastewater treatment plant. Therefore, it can significantly contribute to the spread of β-lactam antibiotic resistant bacteria. However, the products formed by γ-irradiation were more easily biodegradable as they were utilized as nutrient source by the microbes of the activated sludge and the products did not show antibacterial activity. During irradiation treatment of aerated aqueous solutions mainly hydroxyl radicals induce the elimination of antimicrobial activity by making alterations at the bicyclic β-lactam part of these antibiotics. Since the β-lactam part is the same in oxacillin and cloxacillin, the biochemical characteristics of products of the two antibiotics are similar. The attack of hydrated electron takes place on the carbonyl groups. When the irradiation is made under anoxic conditions these reactions may also contribute considerably to alterations at the β-lactam part and thereby to the loss of antibacterial activity.

Real-time biomonitoring of oxygen uptake rate and biochemical oxygen demand using a novel optical biogas respirometric system

In response to the ever-increasing need for monitoring-based process control of wastewater treatment plants, an online applicable respirometer shows great promise for real-time measurement of oxygen uptake rate (OUR) and biochemical oxygen demand (BOD) measurements as a surrogate of the biodegradability of wastewater. Here, we have developed a photosensor-assisted real-time respirometric system equipped with bubble counting sensors for accurate measurement of microbial oxygen consumption in a bottle. This system can measure OUR and BOD in a bottle equipped with a tube containing NaOH solution to absorb carbon dioxide and supplied with continuous atmospheric oxygen to the bottle, which reliably supplies non-limiting dissolved oxygen (DO) for aerobic biodegradation even at high organic loads. These technical improvements allow a sensitive and rapid analytical tool offering real-time profiles of oxygen uptake rate as well as BOD measurements with an extended measurable range (0–420 mg O2/L), enabling significant reduction or elimination of dilution steps. The respirometric system was used to elucidate the biodegradable kinetics of domestic and swine wastewaters as a function of the type and concentration of organic matters, depending on source characteristics including rapidly or slowly oxidizable organic substances by bacteria. Compared with conventional and manometric BOD methods, our method is reliable and accurate.

Active biomass estimation based on ASM1 and on-line OUR measurements for partial nitrification processes in sequencing batch reactors

The main challenge for partial nitrification is to reach stable nitrite accumulation, which strongly depends on the nitrite-oxidizing bacteria (NOB) growth in the reactor. The on-line estimation of active biomass may enhance the decision-making process to maintain a high nitrite accumulation in the reactor. In this work, we propose an active biomass estimator based on ASM1 and on-line oxygen uptake rate measurements (OUR-E) in a sequencing batch reactor. In order to validate the OUR-E, two operating scenarios were applied during 200 days of operation: unfavorable (sludge retention time (SRT) = 40 d, pH = 7.6, dissolved oxygen (DO) = 2 mg/L) and favorable for partial nitrification (SRT = 10 d, pH = 8.5, DO = 2 mg/L). Furthermore, a second estimation method based on off-line measurements of N-species concentrations (Nsp-E) was implemented to evaluate the performance of the OUR-E. The OUR-E was able to predict a reduction in the NOB active fraction from 10.3% to 1.6% with nitrite accumulation over 80% when we shifted the operating scenario. Although both estimators predicted similar results, the OUR-E showed a better prediction quality than the Nsp-E, according to Theil’s coefficient of inequality.

Development of Decay in Biofilms under Starvation Conditions—Rethinking of the Biomass Model

The study investigates the decay of heterotrophic biomass in biofilms under starvation conditions based on measurements of the oxygen uptake rate (OUR). Original incentive was to understand the preservation of active biomass in SBR-trickling filter systems (SBR-TFS), treating event-based occurring, organically polluted stormwater. In comparison with activated sludge systems, the analyzed biofilm carrier of SBR trickling filters showed an astonishing low decay rate of 0.025 d−1, that allows the biocenosis to withstand long periods of starvation. In activated sludge modeling, biomass decay is regarded as first order kinetics with a 10 times higher constant decay rate (0.17–0.24 d−1, depending on the model used). In lab-scale OUR measurements, the degradation of biofilm layers led to wavy sequence of biomass activity. After long starvation, the initial decay rate (comparable to activated sludge model (ASM) approaches) dropped by a factor of 10. This much lower decay rate is supported by experiments comparing the maximum OUR in pilot-scale biofilm systems before and after longer starvation periods. These findings require rethinking of the approach of single-stage decay rate approach usually used in conventional activated sludge modelling, at least for the investigated conditions: the actual decay rate is apparently much lower than assumed, but is overshadowed by degradation of either cell-internal substrate and/or the ability to tap “ultra-slow” degradable chemical oxygen demand (COD) fractions. For the intended stormwater treatment, this allows the application of technical biofilm systems, even for long term dynamics of wastewater generation.

Biocalorimetric monitoring of glycoengineered P. pastoris cultivation for the production of recombinant huIFNα2b: A quantitative study based on mixed feeding strategies.

Real-time monitoring of glycoengineered Pichia pastoris by employing process analytical technology (PAT) tools is vital for gaining deeper insights into the therapeutic protein production process. The present study focuses on influence of mixed feed carbon substrates during the induction phases of glycoengineered P. pastoris cultivation, for recombinant human interferon α2b (huIFNα2b) production by employing calorimetric (biological heat rate, q B ) and respirometric (oxygen uptake rate and carbon dioxide evolution rate) measurements. Mixed feed stream of carbon substrates (methanol + glycerol, methanol + sorbitol) at a predetermined "C-molar ratios" were added during the induction phases. Methanol- and sorbitol-based mixed feeding approach resulted in an improved huIFNα2b titer of 288 mg/L by channeling of methanol predominantly towards an optimal functioning of AOX expression system. A stand-off between biomass yield coefficient, degree of reduction of methanol and its cosubstrate (glycerol and sorbitol) determines the fraction of carbon energy channeled toward biomass and protein production, under strict aerobic conditions. Calorespirometric monitoring and assessment of thermal yields enables a reliable prediction of process variables, leading to futuristic efficient PAT-based feed rate control.

Online monitoring of the cell-specific oxygen uptake rate with an in situ combi-sensor.

In a biotechnological process, standard monitored process variables are pH, partial oxygen pressure (pO2), and temperature. These process variables are important, but they do not give any information about the metabolic activity of the cell. The ISICOM is an in situ combi-sensor that is measuring the cell-specific oxygen uptake rate (qOUR) online. This variable allows a qualitative judgement of metabolic cell activity. The measuring principle of the ISICOM is based on a volume element enclosed into a small measuring chamber. Inside the measuring chamber, the pO2 and the scattered light is measured. Within a defined measuring interval, the chamber closes, and the oxygen supply for the cells is interrupted. The decreasing oxygen concentration is recorded by the pO2 optode. This measuring principle, known as the dynamic method, determines the oxygen uptake rate (OUR). Together with the scattered light signal, the cell concentration is estimated and the qOUR is available online. The design of the ISICOM is focused on functionality, sterility, long-term stability, and response time behavior so the sensor can be used in bioprocesses. With the ISICOM, measurement of online and in situ measurement of the OUR is possible. The OUR and qOUR online measurement of an animal cell batch cultivation is demonstrated, with maximum values of OUR = 2.5 mmol L-1 h-1 and a qOUR = 9.5 pmol cell-1 day-1. Information about limitation of the primary and secondary substrate is derived by the monitoring of the metabolic cell activity of bacteria and yeast cultivation processes. This sensor contributes to a higher process understanding by offering an online view on to the cell behavior. In the sense of process analytical technology (PAT), this important information is needed for bioprocesses to realize a knowledge base process control.

Oxygen Uptake Rate Measurement Using Kalman Filter and PWM Control in Activated Sludge Systems

The availability of real-time information about the biological activity is a valuable matter in wastewater treatment employing activated sludge processes, and this is represented by the oxygen uptake rate (OUR). In these processes, OUR measurements have been used as a fast indicator of changes in waste load or influx of toxic organic compounds and for monitoring of the process efficiency. In this paper, we propose a method for OUR estimation by using Kalman filters and PWM control of the dissolved oxygen (DO) concentration in the activated sludge reactor. The proposed method presents a shorter response time than the standard online procedure and a lower measurement uncertainty compared to a previous feedback control method, which estimates the OUR from values of the applied control signal and the DO concentration measurements. Simulations are presented to illustrate the method and experiments are performed in a bench scale activated sludge reactor to show the applicability of the proposed estimator in a real system. The results confirm the fast response of the proposed method and its consistency with respect to the standard procedure for OUR computation.

New developments in online OUR monitoring and its application to animal cell cultures.

The increasing demand for biopharmaceuticals produced in mammalian cells has driven the industry to enhance the productivity of bioprocesses through intensification of culture process. Fed-batch and perfusion culturing strategies are considered the most attractive choices, but the application of these processes requires the availability of reliable online measuring systems for the estimation of cell density and metabolic activity. This manuscript reviews the methods (and the devices used) for monitoring of the oxygen consumption, also known as oxygen uptake rate (OUR), since it is a straightforward parameter to estimate viable cell density and the physiological state of cells. Furthermore, as oxygen plays an important role in the cell metabolism, OUR has also been very useful to estimate nutrient consumption, especially the carbon (glucose and glutamine) and nitrogen (glutamine) sources. Three different methods for the measurement of OUR have been developed up to date, being the dynamic method the golden standard, even though DO and pH perturbations generated in the culture during each measurement. For this, many efforts have been focused in developing non-invasive methods, such as global mass balance or stationary liquid mass balance. The low oxygen consumption rates by the cells and the high accuracy required for oxygen concentration measurement in the gas streams (inlet and outlet) have limited the applicability of the global mass balance methodology in mammalian cell cultures. In contrast, stationary liquid mass balance has successfully been implemented showing very similar OUR profiles compared with those obtained with the dynamic method. The huge amount of studies published in the last years evidence that OUR have become a reliable alternative for the monitoring and control of high cell density culturing strategies with very high productivities.

Aeration step method for kLa measurement under growth conditions in pneumatic bioreactors

AbstractBackgroundDetermination of the volumetric oxygen transfer coefficient (kLa) plays an important role in the design and characterization of bioreactors. Among all methods available, few techniques are suitable for the determination of kLa in pneumatic bioreactors during the course of cultivations. The present work proposes a new aeration step method for kLa evaluation in pneumatic bioreactors during biological consumption of oxygen.ResultsThe aeration step method consisted in promoting step changes in the specific air flow rate (Φair) to change the dissolved oxygen concentration during cultivations, allowing the measurement of both overall oxygen transfer coefficient (kLa) and specific oxygen uptake rate (QO2). These parameters were determined experimentally by employing two microorganisms, one a strict aerobe (Bacillus subtilis) and the other a facultative aerobe (Saccharomyces cerevisiae), for Φair values ranging from 2.0 to 5.0 vvm. For the purpose of comparison, kLa was also determined in experiments using water as the liquid phase, employing a dynamic gassing‐out method. The kLa values during the cultivations ranged from 0.0137 to 0.0545 s−1, while QO2 varied from 0.44 to 10.06 mol kg−1 h−1. The results obtained are shown to be reliable, exhibited excellent reproducibility and are in agreement with other values reported in the literature by different methodologies.ConclusionThe new aeration step method proved to be reliable as an alternative technique for the determination of kLa and QO2 during microbial cultivation in pneumatic bioreactors. © 2019 Society of Chemical Industry

High nitrite concentration accelerates nitrite oxidising organism's death.

High nitrite is a known operation parameter to inhibit the biological oxidation of nitrite to nitrate. The phenomenon is traditionally expressed using a Monod-type equation with non-competitive inhibition, in which the reaction associated with the biomass growth is reduced when high nitrite is present. On the other hand, very high nitrite is also known to slay nitrifiers. To clarify the difference between the growth inhibition and the poisoning, cell counting for living microorganisms in the nitrite oxidiser-enriched activated sludge was conducted in batch conditions under various nitrite concentrations together with measurements of biomass chemical oxygen demand (COD) concentration and oxygen uptake rate. The experiments demonstrated that these measureable parameters were all decayed when nitrite concentration exceeded 100-500 mgN/L at pH 7.0 in the system, indicating that nitrite poisoning took place. Biomass growth was recognised in lower range of nitrite which was expressed with growth inhibition only. Based on the response, a kinetic model for the biological nitrite oxidation was developed with a modification of IWA ASM1. The model was further utilised to calculate a possibility to wash out nitrite oxidiser in the aeration tank where a part of the return activated sludge was exposed to high nitrite liquor in a side-stream partial nitritation reactor.

Mycoplasma capricolum subsp. capripneumoniae, the cause of contagious caprine pleuropneumonia, comprises two distinct biochemical groups.

Mycoplasma capricolum subsp. capripneumoniae, the cause of the World Organisation of Animal Health- listed contagious caprine pleuropneumonia, is a member of the Mycoplasma mycoides cluster which comprises five pathogenic mycoplasmas of ruminants. These mycoplasmas are closely related immunologically and genetically which can lead to difficulties for differential diagnosis. The patterns of substrate metabolism of strains of M. c. capripneumoniae, gathered from diverse geographic regions, were studied by measurement of oxygen uptake rates. The strains fell into two major biochemical groups: one which only oxidised organic acids and glycerol and the other which could additionally metabolise sugars. Furthermore when DNA-DNA hybridisation tests were carried out these two groups of strains could be separated by their degree of DNA homology, the mean hybridisation value between members of the two groups was 86% well above the value of 70% normally used to indicate separate species. DNA-DNA hybridisation was also carried out between M. c. capripneumoniae strains and other members of the M. mycoides cluster. These experiments used labelled DNA from two representative subsp. capripneumoniae strains; these were 7/1a (organic acid-oxidising) and 4/2 LC (glucose-oxidising). The results showed a particularly close relationship of the glucose-oxidising strain to M leachii strains.

Methods for quantification of biosorption in high-rate activated sludge systems

The fundamental mechanism behind biosorption to recover carbon from wastewater through high-rate activated sludge (HRAS) system is insufficiently studied. The most accepted method of quantifying biosorption capacity of activated sludge depends on higher settling velocity solids. As HRAS had different settling characteristics and in addition, raw wastewater fed to the HRAS system contained approximately 55% settleable organics, the conventional biosorption capacity test was not capable of accurately defining biosorption. Thus, we studied ex-situ aerobic yield as an alternative approach for determination of biosorption in batch systems. However this approach similarly to biosorption capacity was not sensitive enough to quantify differences between HRAS types, potentially due to enhanced storage mechanisms under the feast-famine approach. A viable method to determine biosorption in the batch system was based on measurement of ex-situ oxygen uptake rate (OUR) of HRAS over 40h and the biosorption yield was considered as the area underneath the OUR curve normalized for solids concentration. In addition, in-situ based biosorption quantification was proposed in this study based on detailed measurement of carbon mass balances including contribution of extracellular polymeric substances. A clear relationship between biosorption yield and in-situ biosorption with carbon mass-balance, carbon redirection and solids retention time of HRAS systems was observed suggesting two viable methods for quantification of biosorption.

Calculation of the periodic steady state of sequencing batch reactors from oxygen uptake rate (OUR) measurements in batch tests

This paper investigates whether it is possible to calculate the periodic steady state of sequencing batch reactors (SBRs) using kinetic parameters obtained from batch tests. Two industrial wastewaters were treated in SBRs with measurement of the substrate removal and biomass production. Three batch tests at different initial substrate to biomass ratios (S0/X0) were carried out on each wastewater, with measurement of the oxygen uptake rate (OUR). The OUR profiles were used for the estimation of the kinetic parameters using a mathematical model consisting of substrate hydrolysis, biomass growth and endogenous metabolism. The estimated kinetic parameters were then used to calculate the substrate and biomass concentration at the periodic steady state of the SBRs and the obtained values were compared with the experimental data from the SBR runs. It was not possible for one set of kinetic parameters to describe different tests, even for the same wastewater. However, when each test was fitted individually, the model gave good description of the OUR profiles. When used to calculate the periodic steady state of the SBR, the estimated parameter values gave in all cases a complete or almost complete COD removal, in agreement with what observed in the SBR, but satisfactory predictions of biomass concentration for both wastewaters were only obtained with the parameters estimated in the low S0/X0 tests (highest discrepancy 37%).

A concept development of an early warning system for toxic sewage detection

The article presents a concept of an EWS (early warning system) for toxic sewage detection upstream from Wroclaw Wastewater Treatment Plant. It includes design and construction of three toxicity warning stations, situated in municipal sewage system. Early detection of toxic contaminants provides time for corrective actions. Wastewater toxicity level is based on activated sludge OUR (Oxygen Uptake Rate) measurement. The database of normal level of activated sludge OUR is collected during the measurement initial phase. Hence, if toxic event occurs, device will measure decreased OUR value and WWTP operators will be alarmed. Additionally, flow measurement is carried out. It allows to estimate the volume of a toxic stream. Development of the early warning system requires solving minimum six different scientific and technical issues and is a subject for a complex research project.

Retracted:Tusk shells in trouble? Physiology and behavior in response to changing temperature in a scaphopod (Mollusca: Scaphopoda: Dentaliida)

AbstractScaphopods (tusk shells) are infaunal marine predators that occur at locally high densities in coastal and deep‐sea mud habitats, and as consumers of foraminifera they are important in carbon cycling. We investigated oxygen metabolism and burying behavior of the scaphopodRhabdus rectiusand its responses to altered temperatures. These are the first measurements of oxygen uptake rates for any member of this taxonomic class. In response to elevated temperatures, oxygen uptake rates increased, but the ability of animals to bury themselves in sediment was compromised. Female scaphopods were significantly larger than males and, when corrected for body mass, oxygen uptake rates were consistently higher for female individuals than for males. This is consistent with previous anecdotal observations of females in other scaphopod species being larger and potentially more active. In conditions of declining oxygen availability, individuals ofRhabdus rectiusshowed strong oxyregulatory ability by maintaining the same oxygen uptake rate displayed in normoxic conditions. The ability to maintain normal metabolic functioning even in conditions of oxygen limitation would benefit a species living in a benthic environment that may be prone to temporary or transient anoxic events. Yet the decrease in normal escape response in moderately elevated temperatures indicates these animals may be at risk from rising sea temperatures.

Controlling the feed rate of propanol to optimize erythromycin fermentation by on-line capacitance and oxygen uptake rate measurement.

The aim of the present study was to optimize the feeding proportion of glucose and propanol for erythromycin biosynthesis by real-time monitoring and exploring its limited ratio by the on-line multi-frequency permittivity measurement. It was found that the capacitance values were sensitive to the variation of biomass concentration and microbial morphology as well as the true state of cell growth. It was most favorable to both cell growth and secondary metabolism to keep the ratio of glucose to propanol at 4.3 (g/g). The specific growth rate calculated by the capacitance measurement correctly and accurately reflected the cell physiological state. An appropriate feed rate of propanol was crucial for cell growth and secondary metabolism, as well as to improve the quality of erythromycin-A. In addition, the erythromycin production titer (10,950 U/mL) was further enhanced by 4 % when the propanol feed was regulated by step-down strategy based on both OUR (oxygen uptake rate) and the on-line monitoring capacitance.

Design and setup of intermittent-flow respirometry system for aquatic organisms.

Intermittent-flow respirometry is an experimental protocol for measuring oxygen consumption in aquatic organisms that utilizes the best features of closed (stop-flow) and flow-through respirometry while eliminating (or at least reducing) some of their inherent problems. By interspersing short periods of closed-chamber oxygen consumption measurements with regular flush periods, accurate oxygen uptake rate measurements can be made without the accumulation of waste products, particularly carbon dioxide, which may confound results. Automating the procedure with easily available hardware and software further reduces error by allowing many measurements to be made over long periods thereby minimizing animal stress due to acclimation issues. This paper describes some of the fundamental principles that need to be considered when designing and carrying out automated intermittent-flow respirometry (e.g. chamber size, flush rate, flush time, chamber mixing, measurement periods and temperature control). Finally, recent advances in oxygen probe technology and open source automation software will be discussed in the context of assembling relatively low cost and reliable measurement systems.