Evaluation of E.coli losses in a tidal river network using a refined 1-D numerical model

Predicting the rate of Escherischia coli (E.coli) loss in a river network is one of the key conditions required in the management of bathing waters, with well verified numerical models being effective tools used to predict bathing water quality in regions with limited field data. In this study, a unique finite volume method (FVM) one-dimensional model is firstly developed to solve the mass transport process in river networks, with multiple moving stagnation points. The model is then applied to predict the concentration distribution of E.coli in the river Ribble network, UK, where the phenomena of multiple stagnation points and different flow directions appear extensively in a tidal sub-channel network. Validation of the model demonstrates that the proposed method gives reasonably accurate solution. The verification results show that the model predictions generally agree well with measured discharges, water levels and E.coli concentration values, with mass conservation of the solution reaching 99.0% within 12 days for the Ribble case. An analysis of 16 one-year scenario runs for the Ribble network shows that the main reduction in E.coli concentrations occurs in the riverine and estuarine regions due to the relatively large decay rate in the brackish riverine waters and the long retention time, due to the complex river discharge patterns and the tidal flows in the regions

Numerical Modeling Of The Fecal Bacteria Transport Processes In Sediment-Laden Flow

Many experiments, field measurements and few numerical tests shows the transport and fate of Faecal Bacteria have a tight relationship of the sediment transport including the absorbing, releasing and changing the radiation of sunshine especially in the fine cohesive particles and etc. The nonuniform distribution of 2-D and 3-D structures of hydrodynamic, salinity and suspended sediment (SS) in the riverine and estuary may make the solution of Faecal Bacteria to become more complex. With related measured data, the different coupling models based on modified EFDC 2D model are built to solve the dynamic processes of Faecal Bacteria and decouple the influences non-equilibrium transport of suspended and bed load sediment. The results in the Ribble river and estuary shows the sediment transport may have obvious influences on the Faecal Bacteria processes with ranged about maximum 10~30% variance in the shallow Ribble delta region. In addition, the sediment deposition and erosion driven by the different hydrodynamic condition may cause the accumulative impact on the Faecal Bacteria processes and cause a fluctuation at some degree on the dynamic distribution of FIO concentration

A Swarm-based Dynamic Evacuation Simulation Model Under the Background of Secondary Disasters

AbstractDue to the occurrence of secondary disasters in disaster relief, a swarm-based dynamic disaster evacuation simulation model is established to settle the practical difficulties of reducing efficiency in evacuation. And much better simulation results have been achieved than static plans or disorganized autonomous escape scheme. Simulation results show that “to changing the status quo” dynamic evacuation plan is much better than “maintaining the status quo,” the static and self-evacuation plan or autonomous escape behavior for emergency evacuation, especially those with secondary disasters

Integrated hydro-bacterial modelling for predicting bathing water quality

In recent years health risks associated with the non-compliance of bathing water quality have received increasing worldwide attention. However, it is particularly challenging to establish the source of any non-compliance, due to the complex nature of the source of faecal indicator organisms, and the fate and delivery processes and scarcity of field measured data in many catchments and estuaries. In the current study an integrated hydro-bacterial model, linking a catchment, 1-D model and 2-D model were integrated to simulate the adsorption-desorption processes of faecal bacteria to and from sediment particles in river, estuarine and coastal waters, respectively. The model was then validated using hydrodynamic, sediment and faecal bacteria concentration data, measured in 2012, in the Ribble river and estuary, and along the Fylde coast, UK. Particular emphasis has been placed on the mechanism of faecal bacteria transport and decay through the deposition and resuspension of suspended sediments. The results showed that by coupling the E.coli concentration with the sediment transport processes, the accuracy of the predicted E.coli levels was improved. A series of scenario runs were then carried out to investigate the impacts of different management scenarios on the E.coli concentration levels in the coastal bathing water sites around Liverpool Bay, UK. The model results show that the level of compliance with the new EU bathing water standards can be improved significantly by extending outfalls and/or reducing urban sources by typically 50%

Dynamic tracing of fecal bacteria processes from a river basin to an estuary using a 2D/3D model

In this study fecal bacteria processes have been investigated using the EFDC 2D/3D model, based on local refinements using an orthogonal curvilinear grid system and with the model being applied to Ribble river basin, through the estuary, and into the Fylde Coast. The input fluxes from numerous minor rivers and streams within the basin were solved using a grid-based distributed hydrological model (GDHM) and a river network 1D model (RNM1D), developed by the authors. The detailed measured hydrodynamic data, included tide levels and nearshore ADCP 3D velocity field data at four sites and with data being recorded over a 2-week period. During this period continuous monitoring using four types of tracers was also undertaken across the Ribble basin, which included sampling for E. coli (EC) and Intestinal Enterococci (IE) parameters. Monitoring devices, in the form of buoys, were also used and moved with currents, driven by upstream discharges, tides, waves and wind. The results showed: (i) the grid system gave a detailed topographical representation of the transition zones from the river system to the estuary and coast, with the hydrodynamic and related solute transport processes being well represented; and (ii) the model predicted results fit generally well with the water stage, 3D flow velocity profiles (with some errors in the bottom and surface layers), and E. coli concentrations. The tracer paths from the injection sites were simulated using a Lagrangian particle tracking method, which showed that the tracer from the north bank outfalls and the Ribble river could propagate to the highly popular bathing beaches at Blackpool, particularly under the action of South Westerly winds. More detailed solutions and refinements (e.g., wave driven by the wind and density flows caused by different salinities, temperatures, and suspended sediment concentrations) need to be considered in the next stage of this study

A New Spatial Interpolation Method Based On Cross-Sections Sampling

The spatial interpolation results of the channel topography by the different methods have a very important effect on the topographic distribution of river channel. The study shows that the conventional interpolation methods such as TIN, Kriging and IDW methods can give good results with reasonable parameters when the sampling data is dense enough. However, the spatial distribution of source data sampled by the classical cross-section method in hydrological measurement may have large and small spaces along the longitudinal and transverse directions of river channel respectively, and then these interpolation methods above may give the unreasonable interpolation results. In this case, a new interpolation method named Linear Interpolation on the Fitted Curvilinear Grid of the river channel (LIFCG) is proposed, in which the river regime is considered by a set of curvilinear grids. The topography along the rows of grid dots which have same position with cross sections where the topography data is measured is firstly checked out and calculated by using linear interpolation method, then the topography at other grid nodes are interpolated along the longitudinal lines by using linear interpolation method. The application shows that the new method can give the more reasonable results than TIN, IDW and Kriging methods. In further, based on the new method, the river thalweg is firstly calculated and used to regenerate the channel fitted non-orthogonal curvilinear grid and then applied the grid to interpolate when there are complicated distribution and large spatial variation of channel topography and plane shape. The applications in the curved and braided natural channel’s interpolation show the interpolation by the new method with coupling of the river thalweg is more reasonable at some degree than the method without coupling of the river thalweg and other classical method when sparse cross-section measured sampling data is used

Optimization of water quality monitoring network in large river by combining measurements, a numerical model and matter-element analysis

A monitoring network that resolves the spatial and temporal variations of the water quality is essential in the sustainable management of water resources and pollution control. Due to cost concerns, it is important to optimize the monitoring locations so to use the least number of stations required to obtain the most comprehensive monitoring. The optimal design of monitoring networks is commonly based on the limited data available from existing measuring stations. The main contribution of this paper is the use of a numerical water quality model, calibrated with the available data. This model yields information on the water quality in any cross-section along the river, including the river reaches that are not monitored. Another contribution of the paper is the use of a matter-element analysis that allows for an objective division of the river in reaches that are homogeneous with respect to the water quality as assessed from multiple water quality parameters. The optimal monitoring network consists of one measuring station in each of these homogeneous reaches. The method has been applied to optimize the water quality monitoring network on the 1890 km long upper and middle reaches of the Heilongjiang River in Northeast China. The results suggest that the monitoring network improves considerably by relocating three stations, and not by adding extra stations

Cloud to coast: integrated assessment of environmental exposure, health impacts and risk perceptions of faecal organisms in coastal water

The proper recognition and calculation of polluted sources and the fate and transport of faecal organisms in catchments, river networks and coastal waters are very important to the assessment of environmental exposure, health impacts and risk perceptions of faecal indicator organisms (FIO) in coastal waters. The paper reviews the integrated modelling techniques for faecal processes from cloud to coast, including sediment and faecal bacteria interactions, and then presents a theoretical and case study in the numerical modelling for FIO levels in the river Ribble and Fylde Coast using the two-dimensional or three-dimensional environmental fluid dynamics code and the 1D Flow And Solute Transport in Estuaries and Rivers models, respectively. The related key parameters in the linked model are illustrated and analysed, together with validation of the hydrodynamic processes and the faecal bacteria concentration levels being undertaken using measured related data acquired in 1999. Using the model results, a quantitative microbial risk assessment is undertaken, where a moderate dose for swimming in faecal coliform-laden flows is accepted, as given by the European (EU) water quality standard requirements. The results show that some local regions of relatively high concentration exist near the outfalls and these values are not compliant with the mandatory and tighter microbial standards in the UK, as governed by the new EU Water Framework Directive. Finally, some new research and key challenges for the future are discussed in the paper

Prevalence, associated factors and outcomes of pressure injuries in adult intensive care unit patients: the DecubICUs study

Funder: European Society of Intensive Care Medicine; doi: http://dx.doi.org/10.13039/501100013347Funder: Flemish Society for Critical Care NursesAbstract: Purpose: Intensive care unit (ICU) patients are particularly susceptible to developing pressure injuries. Epidemiologic data is however unavailable. We aimed to provide an international picture of the extent of pressure injuries and factors associated with ICU-acquired pressure injuries in adult ICU patients. Methods: International 1-day point-prevalence study; follow-up for outcome assessment until hospital discharge (maximum 12 weeks). Factors associated with ICU-acquired pressure injury and hospital mortality were assessed by generalised linear mixed-effects regression analysis. Results: Data from 13,254 patients in 1117 ICUs (90 countries) revealed 6747 pressure injuries; 3997 (59.2%) were ICU-acquired. Overall prevalence was 26.6% (95% confidence interval [CI] 25.9–27.3). ICU-acquired prevalence was 16.2% (95% CI 15.6–16.8). Sacrum (37%) and heels (19.5%) were most affected. Factors independently associated with ICU-acquired pressure injuries were older age, male sex, being underweight, emergency surgery, higher Simplified Acute Physiology Score II, Braden score 3 days, comorbidities (chronic obstructive pulmonary disease, immunodeficiency), organ support (renal replacement, mechanical ventilation on ICU admission), and being in a low or lower-middle income-economy. Gradually increasing associations with mortality were identified for increasing severity of pressure injury: stage I (odds ratio [OR] 1.5; 95% CI 1.2–1.8), stage II (OR 1.6; 95% CI 1.4–1.9), and stage III or worse (OR 2.8; 95% CI 2.3–3.3). Conclusion: Pressure injuries are common in adult ICU patients. ICU-acquired pressure injuries are associated with mainly intrinsic factors and mortality. Optimal care standards, increased awareness, appropriate resource allocation, and further research into optimal prevention are pivotal to tackle this important patient safety threat

Correction to: Prevalence, associated factors and outcomes of pressure injuries in adult intensive care unit patients: the DecubICUs study

The original version of this article unfortunately contained a mistake