Integrated ecological modelling for decision support in river management: a lowland river case study (Cauca river in Colombia)

Several practical concepts and software systems have been recently developed in the issue of environmental decision support. However, the application of ecological modelling approaches that integrate hydrodynamic, physical-chemical, and biological components sub-models for predicting macroinvertebrates in rivers, is rather limited and hardly described in literature. The Cauca river is one of most severe cases of contamination for domestic and industrial wastewater discharges in Colombia. One of the most sensitive problems in the Cauca river is the decrease of dissolved oxygen with concentrations near to zero (0) mg/l in some monitoring stations especially during dry season (low flows). Low DO levels affect the ecosystem equilibrium and the functioning and survival of biological communities. In this research an integration of habitat suitability models with the hydrodynamic and physical-chemical water quality model MIKE11 was performed. Ecological models (statistical models) that allow predicting the occurrence and the abundance of macroinvertebrates (Ephemeroptera, Trichoptera and Haplotaxida) in this river under different conditions were built. The integrated ecological model allows to model and to assess the ecological impact of wastewater discharges into the Cauca river and can help to calculate the needed reductions in discharges of organic matter to meet biological quality criteria in this river

Selecting relevant predictors: impact of variable selection on model performance, uncertainty and applicability of models in environmental decision making

One of the crucial steps when developing models is the selection of appropriate variables. In this research we assessed the impact variable selection on the model performance and model applicability. Regression trees were built to understand the relationship between the ecological water quality and the physicalchemical and hydromorphological variables. Different model parameterizations and three combinations of explanatory variables were used for developing the trees. Once constructed, they were integrated with the water quality model (PEGASE) and used to simulate the future ecological water quality. These simulations were summarized per combination of explanatory variables and compared. Three key messages summarize our conclusions. First, it was confirmed that different parameterizations alter the statistical reliability of the trees produced. Secondly, it was found that statistical reliability of the models remained stable when different combinations of explanatory variables were implemented. The determination coefficient (R²) ranged from 0.68 to 0.86; Kappa statistic (K) ranged from 0.15 and 0.46; and the percentage of Correctly Classified Instances (CCI) from 33 to 59%. Thirdly, when applying the models on an independent dataset consisting of future physical-chemical water quality data, different conclusions may be taken, depending on the combination of variables used

Use of habitat suitability modeling in the integrated urban water system modeling of the Drava River (Varazdin, Croatia)

The development of practical tools for providing accurate ecological assessment of rivers and species conditions is necessary to preserve habitats and species, stop degradation and restore water quality. An understanding of the causal mechanisms and processes that affect the ecological water quality and shape macroinvertebrate communities at a local scale has important implications for conservation management and river restoration. This study used the integration of wastewater treatment, river water quality and ecological assessment models to study the effect of upgrading a wastewater treatment plant (WWTP) and their ecological effects for the receiving river. The WWTP and the water quality and quantity of the Drava river in Croatia were modelled in the software WEST. For the ecological modeling, the approach followed was to build habitat suitability and ecological assessment models based on classification trees. This technique allows predicting the biological water quality in terms of the occurrence of macroinvertebrates and the river status according to ecological water quality indices. The ecological models developed were satisfactory, and showed a good predictive performance and good discrimination capacity. Using the integrated ecological model for the Drava river, three scenarios were run and evaluated. The scenario assessment showed that it is necessary an integrated approach for the water management of the Drava river, which considers an upgrading of the WWTP with Nitrogen and Phosphorous removal and the treatment of other diffuse pollution and point sources (including the overflow of the WWTP). Additionally, if an increase in the minimum instream flow after the dams is considered, a higher dilution capacity and a higher self-cleaning capability could be obtained. The results proved that integrated models like the one presented here have an added value for decision support in water management. This kind of integrated approach is useful to get insight in aquatic ecosystems, for assessing investments in sanitation infrastructure of urban wastewater systems considering both, the fulfilling of legal physical chemical emission limits and the ecological state of the receiving waters

Comparison between Staphylococcus aureus, strains isolated from medical students in pre-clinical formation and clinical training

OBJECTIVE: To establish the differences between Staphylococcus aureus isolates from medical students in pre-clinical and clinical training and identify the level of susceptibility to methicillin, vancomycin and alternative antibiotics. MATERIALS AND METHODS: A cross-sectional observational design with non-random sampling was used in medical students during pre-clinical and clinical training. Samples were taken from nasal swabs and cultured on blood agar. For beta-hemolytic gram-positive cocci, catalase and coagulase tests were performed and then cultured on mannitol salt agar. Susceptibility to cefoxitin, oxacillin, linezolid, clindamycin and trimethoprim sulfamethoxazole was assessed by using the Kirby-Bauer technique, and for vancomycin, an E-test was performed (Biomerieux®). RESULTS: 51 strains of S. aureus from nasal swabs were isolated from 112 medical students. 68.6% were identifi ed as methicillinsensitive (MSSA) and 31.4% as methicillin-resistant (MRSA). Four MRSA strains showed vancomycin intermediate (VISA 4-8 μg/mL) profile, 41% of MSSA isolates was resistant to clindamycin, 31% to linezolid and 23.5% to trimethoprim sulfamethoxazole. DISCUSSION: MSSA, MRSA and VISA strains are present in nostrils of our medical students, with MRSA showing high resistance levels (>50%) to clindamycin, TMP-SMX and linezolid, and MSSA levels up to 40%. These findings reiterate the need to accomplish good nasal and hands hygiene in order to minimize the spread of S. aureus in community and healthcare facilities

Modelling the ecological impact of discharged urban waters upon receiving aquatic ecosystems: a tropical lowland river case study: city Cali and the Cauca river in Colombia

The Cauca river is one of most severe cases of pollution for domestic and industrial wastewater discharges in Colombia, principally when it crosses the industrial cities of Cali and Yumbo. The rapid urbanization and major economic development in the Cauca river´s geographical valley has led to dramatic degradation of the environment and increased health risks due to inefficient processing of the increased pollutant load effluents and solid wastes. The city of Cali which is the main urbanization center, with more than two million inhabitants and limitations of the treatment of its wastewaters, discharged in the year 2005, 75 tons of BOD5 per day. These discharges of wastewater are producing an increasing deterioration of the water quality of the Cauca river. This pollution problem is critical after the river crosses the city of Cali, especially during dry season (low flows), when pollution can reach values of 7.5 mg/l of BOD5 and concentrations of Dissolved Oxygen (DO) near to zero (0) mg/l. Low DO levels affect the ecosystem equilibrium and the functioning and survival of biological communities. For this reason, the main objective of this research was to contribute to the integrated water quality management of the Cauca river, developing a mathematical model to investigate the ecological quality of this river under actual conditions as well as after different restoration actions. The approach followed was to build habitat suitability models (statistical models) that allow predicting the presence and the abundance of macroinvertebrates in this river under different conditions. An integration of these ecological models with the hydrodynamic and physical-chemical water quality model MIKE11 was performed. The integrated ecological model allows to model and assess the ecological impact of wastewater discharges into the Cauca river and to calculate the needed reductions in discharges of organic matter to meet biological quality criteria in this river

Integrated ecological modelling for decision support in the integrated urban water system modelling of the Drava river (Varazdin, Croatia)

Legal physical-chemical emission limits are traditionally used for assessing the effectiveness of urban sanitation infrastructure. However, the receiving water’s ecological aspects are disregarded with this conventional approach. European legislation (i.e. Water Framework Directive-WFD) now has an integrated approach of river management, which considers the concept of ecological status. Furthermore, the WFD urges the adoption of a combined analysis of emission limits values and physical-chemical and ecological aspects of the receiving waters and encourage the availability and use of decision support tools for water management such as simulation models. Croatia has signed agreements to join the European Union (EU) and thus taken up the obligation to coordinate its legislation with EU standards, such as the implementation of the WFD for its investments in the construction and upgrading of WWTPs. Thus, Croatia needs a simulation tool that allows assessing the impact of WWTPs discharges on the water quality of rivers, considering physical–chemical and ecological aspects. During the last decade the water quality of the Drava river in Croatia has been affected by an increased demand of electricity production and its misuse as receiving aquatic ecosystem of controlled and uncontrolled discharges of waste from agricultural, urban or industrial activities. This paper presents an integration of wastewater treatment, river water quality and quantity and ecological assessment models to study the effect of upgrading a WWTP in the city of Varazdin and its ecological effects for the receiving river, the Drava river. The paper explains the integrated modelling framework and provides some illustrations of its application. Three scenarios for pollution control in the study area were evaluated with the integrated model. The scenario assessment showed that the upgrading of the WWTP, with Nitrogen and Phosphorous removal, is not enough to reach good ecological water quality in this river, therefore, other point and diffuse pollution sources should be controlled in the area. The integrated modelling framework is flexible enough to be used in conjunction with different approaches/models and can be applied to any river basin. More data should be collected and more variables should be included in an optimization of these models