Indicators of Groundwater Potential for Nitrate Transformation in a Reductive Environment.

Increasing nitrate concentration in many shallow aquifers has become a global environmental problem. In order to determine anoxic aquifer sensitivity to nitrate pollution and potential for nitrogen conservation, we have qualified potential nitrate transformation pathways, by conducting field tests, tracer study, physicochemical and microbiological analysis of the groundwater. Combination of in situ measuring and laboratory analysis of physicochemical properties and selected biological activity reactivity tests (BARTTM), has enabled estimation of different pathways of NO3- reduction. During five days of nitrate enrichment experiment there was no observed increase in NO3- concentration, nor any observed decrease of TN (total nitrogen) in the groundwater, while NH4+ production rates increased (with the peak concentrations of 4.97 mg N/L) on the first day of the experiment. We assume that inhibited respiratory denitrification and enhanced DNRA (dissimilatory reduction of nitrate to ammonium) may preserve available nitrogen in a bioavailable form of ammonium.

Meat industry wastewater: microbiological quality and antimicrobial susceptibility of E. coli and Salmonella sp. isolates, case study in Vojvodina, Serbia.

Wastewater from meat processing industries is a fusion of compounds with a high load of organic matter, and pathogen microorganisms like Escherichia coli, and Salmonella sp. The aim of this research was to determine microbiological characteristics of the wastewater discharged from the meat processing industry in order to get a more detailed insight into meat industry wastewater pollution, and to evaluate the resistance of bacterial strains E. coli and Salmonella sp. to antibiotics. The evaluation of the antimicrobial susceptibility was performed on 37 strains of E. coli and eight strains of Salmonella sp. to nine different antibiotics. The number of faecal pollution indicators was very high in all samples. From a total of 37 strains of E. coli, a moderate degree of resistance was shown to tetracycline (37.83%); a low degree of resistance to ampicillin (21.62%), streptomycin (24.32%), trimethoprim-sulfamethoxazol (18.92%) and nalidixic acid (16.22%); and very low to: chloramphenicol (13.51%), ciprofloxacin (2.7%), gentamicin and cefotaxime (0.0%). The results for eight strains of Salmonella sp. show that all eight isolates had some degree of susceptibility to nine tested antimicrobial agents and six strains were fully susceptible to all tested antibiotics.

Tracer test analysis using flow and transport simulation code and new analytical transport model 27 April 2019.

A convergent flow field tracer test, in two phases, with injection of sodium chloride solution, was conducted on a pumping well and neighboring piezometers belonging to the Kovin-Dubovac area drainage system, on the Serbian sector of the Danube River. The initial goal was to determine the values of hydrogeological parameters in order to analyze the results of the subsequent experiments involving injection of the selected solutes. SEAWAT code (through the Visual Modflow™ 2011 interface), as well as the newly developed analytical model for multilayer setting (1D transport solution for tracer injected as a Dirac impulse in a radial convergent flow field), was used to develop and calibrate a model of the studied portion of the aquifer. The new analytical model demonstrated a very good match to the measured values and to the results of numerical simulation, which indicates that it can be of great utility in characterizing transport conditions. PRACTITIONER POINTS: Results confirm the conclusions of research papers on tracer tests that 10-m scale tests regularly point to heterogeneous aquifer. New analytical 1D radial transport model for multilayer setting demonstrated a very good match with numerical simulation and experimental data. Developed analytical model is usable for characterizing transport conditions in a radial convergent multilayer flow field or other settings.

Mobility and sorption assessment of selected pesticides in alluvial aquifer.

The objective of the paper was to use transport model of selected pesticides (carbendazim, acetamiprid and imidacloprid) in determination of linear sorption coefficients in alluvial aquifer. For constructing transport model, results of a field experiment at the location of Kovin-Dubovac drainage system in Serbia were used in order to set hydraulic parameters (hydraulic conductivity, aquifer layer thickness of the observed area, effective porosity etc.). The field experiment consisted of a tracer test during which concentrations of non-reactive tracer (Cl-) and selected pesticides (carbendazim, acetamiprid and imidacloprid) were monitored. For better characterization of hydraulic parameters, a pumping test was conducted at the observed well and results were used in designing transport model. Simulation model was constructed with Lizza groundwater flow software and W.O.D.A. (Well Outline and Design Aid) solver. Obtained linear sorption coefficients in the sand and gravel water-bearing layer were 0.14 mL g-1 for carbendazim and 0.11 mL g-1 for acetamiprid and imidacloprid. Results from this study are a unique insight into mobility of observed pesticides in the alluvial groundwater in natural conditions and can be used in contamination assessment for drinking water wells.

Occurrence and behavior of selected pharmaceuticals during riverbank filtration in The Republic of Serbia.

The objectives of the research are to determine the occurrence of pharmaceuticals in surface water and groundwater in the Republic of Serbia and to identify significant effects of river-water purification through riverbank filtration, concerning oxic conditions and hydrogeological conditions of alluvial aquifers in Serbia. Between 2009 and 2015, a total of 19 studied pharmaceuticals and metabolites were analyzed in 184 samples, 10 were detected in surface water, and 8 in groundwater. Carbamazepine and metamizole metabolites N-acetyl-4-amino-antipyrine (4-AAA) and N-formyl-4-amino-antipyrine (4-FAA) have the highest frequency of occurrence in surface water (57.3-68.8 %) and in groundwater (19.5-43.9 %), respectively. Highest detected concentrations were for 4-AAA (520 ng/L) and 4-FAA (248 ng/L) in surface water as well as in groundwater (4-AAA 128 ng/L and 4-FAA 150 ng/L). Results showed that riverbank filtration sites with different hydrogeological and oxic conditions could significantly remove investigated pharmaceuticals. Percentage of removal during riverbank filtration was determined for carbamazepine (65.4 %), trimethoprim (100 %), 4-AAA (91.2 %), and 4-FAA (70 %) for all investigated locations. Based on the available data for three specific locations (Danube River alluvion, Sava River alluvion, and Velika Morava River alluvion), results showed that besides oxic conditions, residence time of groundwater in alluvial aquifer and ratio of infiltrated water from river to the well play very important role in the quality of groundwater. These results are extremely important for better understanding of self-purification potential of alluvial aquifers and protection from potential impacts of anthropogenic pollution to the groundwater sources in the Republic of Serbia.

Sorption of selected pharmaceuticals and pesticides on different river sediments.

In the present work, the sorption ability of 17 pharmaceutical compounds, two metabolites, and 15 pesticides (34 target compounds in total) onto four different river sediments was investigated separately. Selected compounds present the most frequently prescribed pharmaceuticals in human and animal medicine and the most frequently used pesticides in agriculture. Their presence into the surface, ground, and waste waters was confirmed into the numerous papers in literature, as well as their presence into the river sediments (for some of them). However, investigations of their sorption onto the river sediments, as major natural protection from potential pollution of ground water by them is missing. Sorption in this study was investigated onto river sediments taken from rivers in the Republic of Serbia, where only less than 10 % of total generated waste water passes through mainly basic treatment processes. Experiments were based on batch equilibrium procedures and obtained solutions were analyzed by previously developed and validated sensitive high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) analytical methods. All results were modeled by Freundlich isotherms. Obtained results have shown that Kf coefficient values are in correlation with organic carbon content. Kd sorption coefficient values were relatively low and ranged in wide ranges for almost all compounds and sediments. That implicates on the conclusion that capacities of the investigated sorbents are not large for those compounds.