Inactivation Coefficient Research Articles

Modelling of E. coli Inactivation from Solutions using GInaFiT via Hybrid Electrode Connected Electro-Disinfection Process

E. coli (Escherichia coli) is a bacterium found in human and animal intestines. These bacteria, which can enter the bloodstream through as anyway as the environment or food, can cause many diseases such as diarrhea, respiratory problems, and blood/urinary tract infections especially in human. Therefore, these bacteria have to be removed from drinking water sources by some inactivation methods. Conventional methods as chlorination, ozonation and UV inactivation methods are effective but the development of techniques that do not require the transportation and storage of chemicals and do not produce negative by-products and cost-effective is the basis of environmental engineering studies. In this study, the inactivation effectiveness of hybrid electrode connected electrochemical process as a new approach on E. coli was investigated. The connection system was experienced with Al/SS/SS as Anode/Cathode/Anode electrode. Simultaneously electrocoagulation (EC) and electrooxidation (EO) mechanism works together in this electrode connection system. The inactivation coefficients were determined by the GInaFiT (Geeraerd and Van Impe Inactivation Model Fitting Tool) modeling tool, which is a Microsoft Excel add-on and the model was statistically well fitted with Double-Weibull. 4D degradation of E. coli was achieved as 21 minutes at a current density of 0.3 A and an optical density (O.D.) of 0.21. It has been determined that hybrid electrode connected electro-disinfection process is an effective approach for the E.coli inactivation.

Analysis of changes in the serotonin inactivation coefficient in brain structures with simultaneous modeling of chronic neurogenic pain and malignant neoplasia

Introduction. Chronic pain syndrome in the development of malignant neoplasms has a complex polyethological character. The study of the pathogenetic mechanisms of pain during the growth of the transplanted tumor in the experiment can open up broad perspectives for the creation of new domestic analgesic drugs for use in oncology.Aim: To study the serotonin inactivation coefficient (SIC), the ratio of serotonin (S) and its main metabolite 5-hydroxyindolacetic acid (S-OH) in brain areas (cortex, hypothalamus) with simultaneous modeling of chronic neurogenic pain and malignant neoplasia.Material and Methods. The study involved white mongrel rats (males). To create a model of chronic pain (CP), ligation of the sciatic nerve was performed according to the method of V.V. Kravtsova in modification. Rat sarcoma M-1 was used to simulate malignant neoplasia. At the main stage of the study, the animals were divided into 4 groups: control, two comparison groups (model of chronic pain, standard M-1 sarcoma grafting) and experimental (combined modeling of CP and oncological process). Animals of the second, third and fourth groups were euthanized sequentially at the 2nd and 3rd weeks of the development of the tumor process.Results. Chronic pain syndrome disrupts the process of serotonin metabolism: the decrease in SIC in the cerebral cortex of experimental animals was more significant by 48% (day 14) and 72% (day 21). The development of the oncological process in comparison groups (groups 3a and 3b) is accompanied by a decrease in the level of SIC, more significant at the 21th day of M-1 sarcoma development: by 37% in the hypothalamus, by 41% in the cerebral cortex. With simultaneous modeling of chronic neurogenic pain and malignant neoplasia, the lowest values of the studied indicator were noted, the decrease was 75% in the cerebral cortex (group 4a) and 87% (group 4b).Discussion. Chronic neurogenic pain and M-1 sarcoma development in isolated modeling variants cause a significant decrease in SIC in hypothalamus and cerebral cortex due to disorders of serotonin formation. A more significant disruption of the serotonin mediator system was noted in cerebral cortex which leads to a decrease in the body’s adaptive capabilities to pain and a disruption of the regulatory mechanisms of metabolism.Conclusion. Modification of serotonin metabolism can be considered as a potential therapeutic target for the treatment of chronic pain syndrome in oncology.

Analysis of changes in the serotonin inactivation coefficient in brain structures with simultaneous modeling of chronic neurogenic pain and malignant neoplasia

Introduction. Chronic pain syndrome in the development of malignant neoplasms has a complex polyethological character. The study of the pathogenetic mechanisms of pain during the growth of the transplanted tumor in the experiment can open up broad perspectives for the creation of new domestic analgesic drugs for use in oncology.Aim. To study the serotonin inactivation coefficient (SIC), the ratio of serotonin (S) and its main metabolite 5-hydroxyindolacetic acid (S-OH) in brain areas (cortex, hypothalamus) with simultaneous modeling of chronic neurogenic pain and malignant neoplasia.Material and Methods. The study involved white mongrel rats (males). To create a model of chronic pain (CP), ligation of the sciatic nerve was performed according to the method of V.V. Kravtsova in modification. Rat sarcoma M-1 was used to simulate malignant neoplasia. At the main stage of the study, the animals were divided into 4 groups: control, two comparison groups (model of chronic pain, standard M-1 sarcoma grafting) and experimental (combined modeling of CP and oncological process). Animals of the second, third and fourth groups were euthanized sequentially at the 2nd and 3rd weeks of the development of the tumor process.Results. Chronic pain syndrome disrupts the process of serotonin metabolism: the decrease in SIC in the cerebral cortex of experimental animals was more significant by 48% (day 14) and 72% (day 21). The development of the oncological process in comparison groups (groups 3a and 3b) is accompanied by a decrease in the level of SIC, more significant at the 21th day of M-1 sarcoma development: by 37% in the hypothalamus, by 41% in the cerebral cortex. With simultaneous modeling of chronic neurogenic pain and malignant neoplasia, the lowest values of the studied indicator were noted, the decrease was 75% in the cerebral cortex (group 4a) and 87% (group 4b).Discussion. Chronic neurogenic pain and M-1 sarcoma development in isolated modeling variants cause a significant decrease in SIC in hypothalamus and cerebral cortex due to disorders of serotonin formation. A more significant disruption of the serotonin mediator system was noted in cerebral cortex which leads to a decrease in the body's adaptive capabilities to pain and a disruption of the regulatory mechanisms of metabolism.Conclusion. Modification of serotonin metabolism can be considered as a potential therapeutic target for the treatment of chronic pain syndrome in oncology.

Use of bacteriophage to inactivate pathogenic bacteria from wastewater

The aim of this study was to enhance the rhizobacterium potential in horizontal subsurface flow constructed wetland (CW) system planted by Phragmites australis using specific and lytic phages. The bioinoculation of specific bacteriophage for target bacteria; Salmonella typhi, and the monitoring of bacterial inactivation under different conditions showed the effectiveness of this methodology to enhance bacteria reduction and consequentially ameliorate purification performance of this studied biological treatment system. The injection of the phage at a concentration equal to 103 UFP/mL within the rhizosphere of the inoculated filter (F) was allowed 1 U-Log10 of improvement of bacterial inactivation compared to the control filter (T) nearly 1 logarithmic unit thus, a 90% improvement of bacteria reduction. When we increased the phage titer (105 UFP/mL), the bacterial reduction equal to 2.75 U-Log10 (N/N0) was registered that corresponds to a decrease of nearly 99.9%. According to the first-order model, the inactivation coefficient is equal to 2.29 min−1 (0.88 min−1 for the first experiment) and the bacterial reduction rate is 5 times higher than that determined for the control filter. This results show the positive impact of the phage in the bacterial inactivation and the improvement of water treatment of the biofilter C.

Effect of turbidity on ultraviolet disinfection of domestic wastewater for agricultural reuse

Water treatment and reuse are fundamental because of the increasing demand for freshwater, especially in agriculture. Accordingly, this study evaluated the effects of turbidity of wastewater processed at the Effluent Treatment Station (ETE) of the UFSCar/Araras and of UV dose on microbial inactivation. The ETE treats up to 2000 L of wastewater daily from toilets and a university restaurant and has five components (grease box, septic tank, microalgae tank, upflow anaerobic filter, and wetlands). Pretreated effluents were used in the experiments, and sampling sites consisted of inspection boxes located after the wetlands. Sample collection, inspection, preservation, and analyses were performed according to standard methods. Sample turbidity was adjusted to 5, 50, 100, 200, and 300 nephelometric turbidity units (NTU), and UV doses of 7.2–28.8 mWs cm-2 were used. A 5 x 5 factorial design (five turbidity levels and five radiation doses) was used, totaling 25 treatments. Each treatment was performed in triplicate. The data were submitted to analysis of variance and Tukey’s test. The results showed that the increase in turbidity significantly decreased disinfection efficiency in samples with turbidity levels higher than 50 NTU. The microbial inactivation coefficients obtained here can be extrapolated to disinfection of wastewater with turbidity up to 300 NTU to eliminate thermotolerant coliforms. The UV sterilizer is feasible for wastewater treatment and its reuse in agriculture.
 Keywords: domestic effluent, sustainability, ultraviolet radiation, water reuse.

Chlorine inactivation of Escherichia coli O157:H7 in fresh produce wash process: Effectiveness and modeling

Inactivation rate constant or inactivation coefficient (specific lethality) quantifies the rate at which a chemical sanitizer inactivates a microorganism. This study presents a modified disinfection kinetics model to evaluate the potential effect of organic content on the chlorine inactivation coefficient of Escherichia coli O157:H7 in fresh produce wash processes. Results show a significant decrease in the bactericidal efficacy of free chlorine (FC) in the presence of organic load compared to its absence. While the chlorine inactivation coefficient of Escherichia coli O157:H7 is 70.39 ± 3.19 L/mg/min in the absence of organic content, it drops by 73% for a chemical oxygen demand (COD) level of 600–800 mg/L. Results also indicate that the initial chlorine concentration and bacterial load have no effect on the chlorine inactivation coefficient. A second-order chemical reaction model for FC decay, which utilizes a proportion of COD as an indicator of organic content in fresh produce wash was employed, yielding an apparent reaction rate of (9.45 ± 0.22) × 10−4 /μM/min. This model was validated by predicting FC concentration in multi-run continuous wash cycles with periodic replenishment of chlorine.

Uncertainty Analysis and Identification of Key Parameters Controlling Bacteria Transport Within a Riverbank Filtration Scenario

AbstractManaged aquifer recharge through bank filtration is an important method to produce sustainable drinking water. Yet, water quality related to transport of pathogens (bacteria and viruses) into groundwater systems from surface waters can be a matter of concern, especially in urbanized regions. Based on a 1‐year monitoring campaign, a reactive transport model was developed for bacteria transport at a riverbank filtration site located in Germany. The model allows simulating advective‐dispersive transport and relies on the colloid filtration theory to mimic attachment and detachment of bacteria to and from the sediment in addition to inactivation, straining and blocking of bacteria. Due to the complexity of the investigated processes, the reactive transport model is characterized by a high level of parametrization, encompassing parameters driving flow as well as solute and colloid transport. A global sensitivity analysis has been applied to identify the most relevant model parameters with respect to piezometric pressure heads, groundwater temperature, and concentrations of chloride, oxygen, coliforms, and Escherichia coli. The model has been calibrated within a stochastic framework, to provide model parameter estimates and to quantify their uncertainty. Our results suggest that bacteria transport models are highly sensitive to inactivation coefficients, straining coefficients, and bacteria size. Permeability of the colmation layer at the riverbank is a key factor for bacteria transport through its influence on residence times. Seasonal variability of boundary conditions, especially anoxic aquifer conditions in the summer and high groundwater flow velocities during flooding periods, resulted in a reduction of inactivation and increased bacteria concentrations at observation wells.

Predicting fecal coliform inactivation in a mixotrophic algal wastewater treatment system

Our previous reports have detailed the development of a pilot-scale algal wastewater treatment system (A-WWTS) utilizing a mixotrophic strain, Galdieria sulphuraria. This A-WWTS has consistently achieved discharge standards for organics and nutrients in a single step, concurrently reducing coliform bacteria to undetectable levels. Here, we present an approach to predict i) the fate of fecal coliform in this A-WWTS; and, ii) the fed-batch processing time required for a desired inactivation level. Specifically, a process model was developed to predict fecal coliform reduction under the synergistic effect of temperature, pH, and sunlight in terms of their individual first order inactivation rates. First-order temperature dependent inactivation rate at 20°C (k20) was established as 0.05h−1 with a temperature coefficient (θ) of 1.08. Inactivation coefficient due to the combined effects of sunlight was established as 0.647m2/MJ. The proposed approach was validated with experimental data from five scenarios; the quality of predictions of log removals spanning over five orders of magnitude (r2=0.947; n=12) was comparable to or better than those reported previously in inactivation studies. Utility value of this approach in forecasting fed-batch processing time under field conditions is illustrated.

Safe surface concept in vertical flow constructed wetland design to mitigate infection hazard

Decentralized wastewater management based on vertical flow constructed wetlands (VFCWs) can be an effective solution for minimizing sanitation problems also in urban landscapes, especially when considering rapidly expanding cities in developing countries. Yet, the mass implementation of VFCWs in urbanized areas first needs improvement of a few design drawbacks – among them, the control of infection hazard is of primary importance. Therefore, in this study, the possibility of mitigation of the VFCW-derived infection hazard was assessed, through analysis of bacteriostatic properties of top filtration layer materials, according to clinical experiences based on “safe” antimicrobial surfaces. The experiment was carried out on a daily operating VFCW. Coliform bacteria survival rates were measured for known VFCW construction materials such as Pinus bark, gravel, slag, charcoal and LECA. The calculated die-off rates expressed as 12-h first-order inactivation coefficients ranged between 6.91 h−1 (slag/summer) and 0.58 h−1 (Pinus bark/autumn). The obtained die-off curves showed charcoal, Pinus bark and LECA to have little bacteriostatic properties – even occasionally providing conditions promoting the growth of the coliform population. Meanwhile, slag and gravel were strictly inhibiting bacteria growth, reducing the population up to 99% within the first 3 h of contact time. The research showed that it is possible to significantly mitigate the infection hazard of VFCW by means of proper top-layer substrate material, similar or equal to slag or gravel.

Minimizing Virus Transport in Porous Media by Optimizing Solid Phase Inactivation.

The influence of virus type (PRD1 and ΦX174), temperature (flow at 4 and 20°C), a no-flow storage duration (0, 36, 46, and 70 d), and temperature cycling (flow at 20°C and storage at 4°C) on virus transport and fate were investigated in saturated sand-packed columns. The vast majority (84-99.5%) of viruses were irreversibly retained on the sand, even in the presence of deionized water and beef extract at pH = 11. The reversibly retained virus fraction () was small (1.6 × 10 to 0.047) but poses a risk of long-term virus contamination. The value of and associated transport risk was lower at a higher temperature and for increases in the no-flow storage period due to the temperature dependency of the solid phase inactivation. A model that considered advective-dispersive transport, attachment (), detachment (), solid phase inactivation (μ), and liquid phase inactivation (μ) coefficients, and a Langmuirian blocking function provided a good description of the early portion of the breakthrough curve. The removal parameters were found to be in the order of > μ >> μ. Furthermore, μ was an order of magnitude higher than μ for PRD1, whereas μ was two and three orders of magnitude higher than μ for ΦX174 at 4 and 20°C, respectively. Transport modeling with two retention, release, and inactivation sites demonstrated that a small fraction of viruses exhibited a much slower release and solid phase inactivation rate, presumably because variations in the sand and virus surface roughness caused differences in the strength of adhesion. These findings demonstrate the importance of solid phase inactivation, temperature, and storage periods in eliminating virus transport in porous media. This research has potential implications for managed aquifer recharge applications and guidelines to enhance the virus removal by controlling the temperature and aquifer residence time.

Modelling the influence of total suspended solids on E. coli removal in river water.

Following sewer overflows, fecal indicator bacteria enter surface waters and may experience different lysis or growth processes. A 1D mathematical model was developed to predict total suspended solids (TSS) and Escherichia coli concentrations based on field measurements in a large-scale flume system simulating a combined sewer overflow. The removal mechanisms of natural inactivation, UV inactivation, and sedimentation were modelled. For the sedimentation process, one, two or three particle size classes were incorporated separately into the model. Moreover, the UV sensitivity coefficient α and natural inactivation coefficient kd were both formulated as functions of TSS concentration. It was observed that the E. coli removal was predicted more accurately by incorporating two particle size classes. However, addition of a third particle size class only improved the model slightly. When α and kd were allowed to vary with the TSS concentration, the model was able to predict E. coli fate and transport at different TSS concentrations accurately and flexibly. A sensitivity analysis revealed that the mechanisms of UV and natural inactivation were more influential at low TSS concentrations, whereas the sedimentation process became more important at elevated TSS concentrations.

Mathematical modeling of colloid and virus cotransport in porous media: Application to experimental data

A conceptual mathematical model was developed to describe the simultaneous transport (cotransport) of viruses and colloids in three-dimensional, water saturated, homogeneous porous media with uniform flow. The model accounts for the migration of individual virus and colloid particles as well as viruses attached onto colloids. Viruses can be suspended in the aqueous phase, attached onto suspended colloids and the solid matrix, and attached onto colloids previously attached on the solid matrix. Colloids can be suspended in the aqueous phase or attached on the solid matrix. Viruses in all four phases (suspended in the aqueous phase, attached onto suspended colloid particles, attached on the solid matrix, and attached onto colloids previously attached on the solid matrix) may undergo inactivation with different inactivation coefficients. The governing coupled partial differential equations were solved numerically using finite difference methods, which were implemented explicitly or implicitly so that both stability and speed factors were satisfied. Furthermore, the experimental data collected by Syngouna and Chrysikopoulos [1] were satisfactorily fitted by the newly developed cotransport model.

Pathogen Transport in Groundwater—Estimation of Transport Parameters

The present study deals with the analysis of pathogen transport in groundwater and estimation of transport parameters. The parameter estimation is formulated as a least-squares minimisation problem in which the parameters are estimated by minimizing the deviations between the models predicted and experimentally observed pathogen concentrations. A parameter estimation procedure is developed by coupling an analytical model simulating one-dimensional pathogen transport with a genetic algorithm. Genetic algorithms are used to estimate the transport parameters, dispersion coefficient and inactivation coefficient. The uniqueness and stability of the inverse procedure is analysed. The performance of the optimisation algorithm is assessed by generating hypothetically generated pathogen concentration data. It is found that genetic algorithm optimisation technique converge to the true solution and hence can be used as a tool for the estimation of the pathogen transport parameters.

Parameter identification of virus transport in porous media using equilibrium and non-equilibrium models

In this study, virus transport parameters in porous media were estimated using a hybrid finite volume model coupled with a non-linear least square optimization algorithm. For the study, both non-equilibrium and equilibrium transport model were considered. For the case of estimating two or three unknown parameters with non-equilibrium transport model, presence of distribution coefficient, inactivation coefficients of liquid and sorbed phase results in a non-unique estimate. Similarly, in case of parameter estimation with non-linear equilibrium transport model, a priori estimate of one of the Freundlich isotherm parameter (i.e. n or kf) along with inactivation coefficients for liquid or sorbed phases is necessary. Finally, the model is applied to estimate the parameters from a column experiment involving virus transport and it was found that non-equilibrium models fit the observed data much better as compared to equilibrium model.

Hybrid-Optimization Approach for Estimating Parameters of a Virus Transport Process in Aquifer

AbstractSimulation of a virus transport process in a groundwater aquifer is necessary for predicting the movement of viruses in an aquifer. It is also necessary in implementing remedial measures to inactivate viruses present in groundwater. For simulating the virus transport process in a groundwater aquifer, the parameters responsible for movement of viruses in an aquifer have to be estimated. In the case of saturated porous media, the transport parameters are linear distribution coefficient, hydrodynamic dispersion coefficient, and inactivation coefficient for aqueous and sorbed viruses. These parameters can be estimated using an inverse optimization procedure that minimizes an error function represented by the difference between the experimentally observed and simulated virus concentration. Gradient-based classical optimization methods can be applied to minimize the error function for estimating the parameters of the transport process. It is reported that the error function is nonlinear and nonconvex in...

Applying the Membrane-Less Electrolyzed Water Spraying for Inactivating Bioaerosols

The inactivating efficiency using membrane-less electrolyzed water (MLEW) spraying was evaluated against two airborne strains, Staphylococcus aureus and λ virus aerosols, in an indoor environment-simulated chamber. The air exchanged rate (ACH) of the chamber was controlled at 0.5 and 1.0 h–1. MLEW with a free available chlorine (FAC) concentrations of 50 and 100 ppm were pumped and sprayed into the chamber to treat microbial pre-contaminated air. Bioaerosols were collected and cultured from air before and after MLEW treatment. The first-order constant inactivation efficiency of the initial counts of 3 × 104 colony-forming units (CFU or PFU)/m3 for both microbial strains were observed. A higher FAC concentration of MLEW spraying resulted in greater inactivation efficiency. The inactivation coefficient under ACH 1.0 h–1 was 0.481 and 0.554 (min–1) for Staphylococcus aureus of FAC 50 and 100 ppm spraying. In addition, increasing the air exchange rate also improved the inactivation rate. The inactivation coefficient of FAC 100 ppm spraying for Staphylococcus aureus was 0.412 and 0.403 (min–1) under ACH 1.0 and 0.5 h–1. These results indicated that MLEW spraying is likely to be effective in minimizing microbial airborne contamination, especially for poorly ventilated spaces.

Special Issue on Toxics and Pathogens in the Environment

Special Issue on Toxics and Pathogens in the Environment

Investigation of the Dependence of Inactivation Coefficient on Pertinent Physical Quality Parameters to Low Doses Ionizing Radiation

Inactivation constant for V79 cells has been extracted from radiobiology experiments that utilize charged particles to irradiate mammal cells in vitro. Physical parameters such as effective charge, radiation mean free path and linear ionization which characterized protons and heluim-4 particles are determined using of standard values. The relationship between inactivation constant α and physical quality parameters have been determined, in this research, for protons and heluim-4 particles. This approach allows getting the characteristic biological response of inactivation of V79 cells in terms of each selected physical quality parameter. The best regression models are formulated for each obtained relationship.

Inactivation of plant infecting fungal and viral pathogens to achieve biological containment in drainage water using UV treatment

To explore whether ultraviolet (UV) light treatment within a closed circulating and filtered water drainage system can kill plant pathogenic species. Ultraviolet experiments at 254 nm were conducted to determine the inactivation coefficients for seven plant pathogenic species. At 200 mJ cm(-2), the individual species log reductions obtained for six Ascomycete fungi and a cereal virus were as follows: Leptosphaeria maculans (9·9-log), Leptosphaeria biglobosa (7·1-log), Barley stripe mosaic virus (BSMV) (4·1-log), Mycosphaerella graminicola (2·9-log), Fusarium culmorum (1·2-log), Fusarium graminearum (0·6-log) and Magnaporthe oryzae (0·3-log). Dilution experiments showed that BSMV was rendered noninfectious when diluted to >1/512. Follow-up large-scale experiments using up to 400 l of microbiologically contaminated waste water revealed that the filtration of drainage water followed by UV treatment could successfully be used to inactivate several plant pathogens. By combining sedimentation, filtration and UV irradiation within a closed system, plant pathogens can be successfully removed from collected drainage water. Ultraviolet irradiation is a relatively low cost, energy efficient and labour nonintensive method to decontaminate water arising from a suite of higher biological containment level laboratories and plant growth rooms where genetically modified and/or quarantine fungal and viral plant pathogenic organisms are being used for research purposes.

The impact of pond depth and environmental conditions on sunlight inactivation of Escherichia coli and enterococci in wastewater in a warm climate

Microcosm experiments were carried out under dark and real sunlight conditions in Ouagadougou (Burkina Faso) to investigate the survival of faecal indicators (Escherichia coli and enterococci) in secondary wastewater. Light damage was estimated by loss of bacterial culturability. The results clearly show that sunlight has a deleterious effect on the survival of both indicators. The mean dark inactivation coefficients for E. coli and enterococci were 0.045 and 0.047 h(-1), respectively, whereas inactivation coefficients in the shallowest microcosm (0.1 m) in illuminated conditions were 0.796 and 0.559 h(-1), respectively. No significant effect of pond depth (0.1-0.9 m) on the inactivation of both indicators was observed in the dark. However, the effect of depth was significant in the microcosms exposed to sunlight, probably because of attenuation. In illuminated conditions, enterococci were broadly inactivated more rapidly than E. coli (T90 = 26.81 h for E. coli and 15.67 h for enterococci in the 0.4 m microcosm). However, E. coli presented greater variability in the survival capabilities, suggesting difficulties in interpreting data using only E. coli as an indicator. Therefore, the use of both indicators together should be advisable for the assessment of effluent quality from waste stabilization ponds in the Sahelian region.