Waste water in the galvanic process contains high concentrations of heavy metals that pose a direct danger to humans and the environment. Conventional methods for their removal are quite expensive and generate a large amount of waste. The development of new and improvement of existing methods for the removal of heavy metals from galvanic wastewater are the subject of many studies. Compared to other purification methods, the adsorption is becoming an increasingly popular method of wastewater purification, especially if the adsorbent is cheap, easily available and does not require any other treatment before use. Therefore, the aim of the work was to investigate the possibility of using natural bentonite for the removal of heavy metal ions from multi-component water systems of the galvanic industry. For this purpose, the physico-chemical characterization of natural bentonite was performed, and then the influence of pH value, time and temperature on the adsorption efficiency was examined. The results of adsorption showed that natural bentonite can be used as an adsorbent for the removal of heavy metal ions from waste galvanic waters, and that at pH 5 it achieves the maximum removal efficiency for Cu(II):Cr(III):Ni(II) ions in the percentage ratio 100 : 99.990 : 99.998. The results showed that the highest removal efficiency for Cu (II) ions was achieved in the first 10 minutes, and 20 minutes for Cr (III) and Ni (II) ions. The maximum efficiency of Cu (II) removal was achieved at all temperatures, while for Cr (III) 99.99% and Ni (II) 100% maximum efficiency was achieved at 35°C, which indicates that the adsorption process is endothermic. The experimental results of the adsorption of Cu (II) metal ions are in good agreement with the Langmuir and Freundlich theoretical models, while for Cr (III) and Ni (II) ions they are in better agreement with the Langmuir adsorption model.

Water hardness and deposition of incrustation is a problem in households and industry. In this regard, several technologies have been developed with the purpose of water softening and preventing the deposition of incrustation. The ion exchange method is the most commonly used method and is considered a conventional method. However, due to the shortcomings of this method, there is a need to develop adequate alternative methods. The potential of the method using biosorbents such as moss Leucobryum glaucum and Spaghnum peat moss for the purpose of removing water hardness has recently become the subject of intensive research with growing interest. In this study, the method using Leucobryum glaucum as a biosorbent was tested and a comparison was made with the conventional method and previously conducted studies that used other biosorbents.

Benthic diatoms have gained prominence as environmental bioindicators since the beginning of the twentieth century. Epilithic diatom taxa are frequently used for ecological water-quality assessments of rivers. Diversity of these dominant group of protists in the benthic communities can be indicative of changes in the freshwater ecosystem. The aim of this study was to analyze the diversity and ecology of diatoms of the Spreča River on the locations affected by urban and industrial pollution. Field sampling of the epilithic diatoms was carried out in the period of May 2021 at two locations, first before and second after the Lukavac city, which is known as industrial city in Bosnia and Herzegovina. Taxonomic verification was carried out using light microscope on permanent slides and revealed in total 38 diatom taxa. The genera with the largest number of species were Diatoma, Navicula and Nitzshia. Identified taxa are widespread species that are known for tolerating  high levels of pollution. A slightly higher number of taxa was recorded at the first location, while at the second, a higher proportion of halophilic taxa was observed.

In this research, a physicochemical analysis of the industrial wastewater from a factory that produces maleic anhydride was performed. Based on the conducted analysis (pH, electrical conductivity, density of the liquid phase, boiling point of the waste suspension, chemical as well as biological oxygen demand, and dry matter), it can be concluded that the waste stream obtained at the outlet pipe from the plant resulting from the production of maleic anhydride requires appropriate treatments. Some of the parameters measured, e.g. pH (0.97±0.06), boiling point (106.8±1.3°C) and acidity, indicate the presence of organic acids such as fumaric and maleic acids, which are formed during the production of maleic anhydride. The possibility of extracting crystals by adding urea and thiourea followed by forced cooling in a heat exchanger was investigated. The most effective method was the addition of thiourea when the most significant amount of crystals was obtained, namely 17.29 wt%. The addition of thiourea in combination with forced cooling greatly facilitates the process of separating the solid and liquid phases of the waste suspension, which could later be adequately treated by physical, chemical or biological methods.

Sludge generated in wastewater treatment processes must be treated in an adequate manner, and therefore disposed of in an environmentally friendly manner. The biggest obstacle to the efficient use of sludge is the high water content, therefore the development of methods to accelerate the sludge dewatering process is particularly important. For the purposes of the research, the waste sludge created in the process of purifying ammoniaphenol wastewater in the GIKIL factory was used. Sludge conditioning was performed by adding a commercial flocculant (0.1 % solution) in combination with pyrophyllite, kaolin clay and shredded cardboard. According to earlier research, the volume of waste sludge with the addition of a suitable flocculant could be reduced by more than 5 times compared to the initial amount, leaving behind a large amount of separated water that can be returned to the process. The results show that the addition of commercial flocculant in the amount of 0.8 % gives the best results (reduction of sludge volume by 78.8 %). A lower percentage was found in samples with a mixture of flocculants with pyrophyllite (78 %) and kaolin (77.6 %), while the combination of flocculants with waste cardboard was ineffective (64.4 %). Addition of flocculant to waste sludge resulted in a decrease in specific filtration resistance (1.15x107 s2/g). A decrease in specific resistance was also observed in flocculant/kaolin clay (0.8x107 s2/g) and flocculant/cardboard (1.09x107 s2/g) samples. Sludge conditioning also resulted in a reduction of suspended solids in the neonate compared to settled raw sludge without additives.

Using natural and modified Ca-bentonite as an adsorbent to observe a satisfactory trend in the removal of heavy metal ions As(V) and Hg(II) from simulated wastewaters. In this original scientific paper, Ca-bentonite was modified in two ways, thermally activated at a temperature of 300 °C for 3 hours and acid activated with HCl and H2SO4, molar concentrations 0,4 mol/L. Ca-bentonite used in this original scientific work was used from the Shipovo mine (Šipovo mine), Bosnia and Herzegovina and proved to be an excellent bioadsorbent for the removal of present ions from simulated wastewaters. Also this is eco-friendly adsorbent and low costed compared to other expensive adsorbents. Due to its chemical composition in which two oxides predominate, namely SiO2 (48.28 mass %) and Al2O3 (23.04 mass%), it can be concluded that Ca-bentonite from the Shipovo mine (Šipovo mine), Bosnia and Herzegovina belongs to the group of refractory materials. The highest removal efficiency of As(V) ions expressed in % was 75.11 at the initial concentration of 1.5 mg/L and was recorded using HCl acid-activated Ca-bentonite. The efficiency of Hg(II) ion removal was the highest using thermally activated Ca-bentonite and this value was 99.66% at an initial concentration of 1 mg/L.

In this paper a mathematical model for the soda ash drying process in a pneumatic dryer was presented. The model presents a macroscopic aspect of the drying process, for a two-phase, gas-solid system. The model is based on mass and heat transfer between the gas phase and the particle, movement of air and particles through the system, and geometric characteristics of the drying system (fan, air heater, pneumatic dryer, and cyclone). The effects of the process parameters, such as airflow, inlet air temperature, and relative humidity, temperature at the inlet of the dryer, etc., have been studied by solving the model. Also, the model was tested for different values of the capacity of wet soda and different values of the operating parameters of the heating medium. The model was implemented in MATLAB and solved with a nonlinear equations solver. Data obtained by the model were compared with industrial pneumatic dryer data for drying wet soda ash particles with good agreement.

The effect of the initial concentration of Cr, Co, Cu, Ni, and Pb metal ions from multicomponent solutions on the sorption capacity of natural and acid activated bentonite was examined in this paper. The acid activation was performed by using hydrochloric and sulfuric acid at different concentrations. The results of adsorption research have shown that bentonite can be effectively used as an adsorbent for the removal of metal ions from multicomponent solutions. Acid activation of bentonite changes the structure and content of individual oxides, increases the porosity and the number of available spots for the adsorption process. For this reason, the bentonite removal efficiency increased after acid activation for all heavy metals tested. With increased acid concentration, the degree of bentonite adsorption increased, and sulfuric acid rather than chloric acid showed better results in removal efficiency.

The effect of pH and initial concentration on the removal of Cu(II) and Ni(II) ions from their monocomponent and two-component aqueous solutions using Na2CO3 as a chemical precipitation agent was investigated in this paper. Monocomponent aqueous solutions  of Cu(II) and Ni(II)  ions with their initial concentrations of 50 and 500 mg/L and two-component aqueous solution with initial concentration of 500 mg/L were prepared. The precipitation was carried out by batch method at room temperature by stirring the solution at 300 rpm for 5 minutes, resulting in the formation of precipitates. The resulting precipitate was separated by filtration from the solution. The experiment proved that Na2CO3 is a good agent for removing Cu(II) and Ni(II) ions from their monocomponent water solutions of 50 and 500 mg/L concentration and two-component water solution with initial concentration of each metal 500 mg/L. The percentage of Cu(II) removal was higher at lower pH values compared to Ni(II) removal.

The development of industry, agriculture, transport and urbanization has resulted in excessive emissions of heavy metals into the environment, which due to their bioaccumulative properties express negative effects on the environment and living organisms as a whole. In this work the presence of heavy metals in the soil samples of the urban area of Lukavac and Kalesija municipality and their effect on the health of the population were studied. Soil samples were collected in October 2017 at five locations in the urban area of Lukavac municipality and two urban locations in Kalesija municipality. Concentrations of chromium (Cr) copper (Cu), cobalt (Co), nickel (Ni), cadmium (Cd), lead (Pb), manganese (Mn), iron (Fe) and zinc (Zn) in the soil samples were determined. The results indicated that in some locations the concentration of heavy metals exceeded the maximum permissible concentration (MPC). MPC value for chromium was exceeded at four locations in the urban area of Lukavac, whereas MPC value for nickel and cadmium was exceeded at all locations. In Kalesija, MPC value was exceeded for chromium and nickel at one location, while cadmium MPC was exceeded at both locations. The negative impact of heavy metals on the health of the population is the cause of many malignant diseases. Statistical analysis of the number of patients with malignant diseases in the area of the Lukavac and Kalesija revealed significantly higher prevalence of malignant diseases of the lungs, breast, skin and cervix in the Lukavac (p<0,05) in comparisson to Kalesija municipality.