Due to the natural energy sources used in constructed wetlands, minimal energy and chemicals are required for wastewater treatment. For the successful wastewater treatment via constructed wetlands, adequate pretreatment and a sufficient amount of oxygen are crucial. Constructed wetlands can be used to treat industrial wastewater, such as wastewater from the dairy industry, with prior degreasing. This study was conducted on a horizontal flow pilot constructed wetland located on a plot of land used by the Biotechnical Faculty in Bihać. The constructed wetland consisted of two fields planted with rushes (Typha latifolia) and reeds (Phragmites australis). The substrate and plants were not changed during the experimental period. We monitored the efficiency of industrial wastewater treatment (wastewater from the dairy industry) by season, varying the flow rate as well as the hydraulic retention time of the water in the device. The quality of the influent and effluent was monitored by determining analytical parameters. The constructed wetland showed the highest efficiency in the summer period, with a hydraulic retention time of 6 days, with removal efficiencies of 98.03% for ammonia, 98.19% for total nitrogen, 95.27% for total phosphorous, 94.50% for COD and 97.73% for BOD5. The organic substance removal efficiency across all four seasons was 94.68%.

The study determined antimicrobial activity using the Disc-diffusion method and extracts of three plants: garlic (Allium sativumL.), turmeric (Curcuma longaL.), and parsley (Petroselinum crispumL.) on Escherichia coli, Salmonella ssp. and Listeria monocytogenes. These pathogens have attracted the attention of numerous agencies and researchers,because of the negative impact on food and human health -and because of the impact of disease development on the economy. These studies are necessary and represent potential natural antimicrobial drugs, and due to the resistance of bacteria to known antibiotics, there is a constant increase in global consumer demand for natural ingredients. The tested plant extracts showed excellent antibacterial activity in all three replicates on Escherichia coliwith an average inhibition zone of 21,86 mm and were characterized as ***S -sensitive for the mentioned bacterium. With an average zone of inhibition of 19,052 mm, Curcuma longashowed the strongest effect on the tested bacterium Salmonella enteritidis, which tells us that this bacteria is very sensitive to the extract of the mentioned plant. The study identified zones of inhibition of very low values (˃ 8 mm) in all three tested extracts: Allium sativumL., Curcuma longaL. Petroselinum crispumL., and Listeria monocytogenes.KEYWORDS:Antimicrobial activity, extract, Disc-diffusion method

Rapid population growth requires more intense production of food industry, with two major consequences: significant amount of food processing residues and more sewage sludge originating from biological wastewater treatment plant. Sludge is a big concern for the disposal for wastewater treatment plant. The European Union makes an effort regarding the reduction of organic fractions disposed at a landfill. Composting is a cost-effective and ecological-friendly alternative for managing biodegradable organic fractions. Experiments of co-composting of sewage sludge, green waste and food waste, at carbon/nitrogen ratios 8.75, 18.00 and 24.90, were performed during three months by monitoring temperature, pH, moisture, carbon and nitrogen proportion, carbon/nitrogen ratio, and germination index. The results showed that co-composting of sewage sludge, green waste, and food waste is effective and results in the production of quality compost.

Heavy metal pollution is a significant environmental problem and has a negative impact on human health and agriculture. Phytoremediation has recently emerged as an efficient heavy metal remediation technology. To examine the phytoremediation potential, an experiment was conducted, where the influence of high and low concentrations of heavy metals, lead, cadmium and zinc (Pb, Cd and Zn) on the phenological characteristics of corn (Zea mays), as well as their accumulation in the underground and aboveground part was monitored. The experiment was carried out in outdoor conditions in pots in which corn was planted and the soil was contaminated with heavy metals in concentrations below and above the maximum allowable concentration prescribed by the Ordinance. The experiment lasted 45 days. By processing the results, statistically significant differences in plant development were determined.The highest concentration of Zn was recorded in the aboveground part of the plant, the stem in the amount of 24.443 mg/kg, and the lowest concentration in the leaf 0.216 mg/kg. The highest concentrations of Cd and Pb were recorded in the root, for lead 26.610 mg/kg and in the stem for cadmium 30.490 mg/kg, which is a statistically significantly higher established value compared to other parts of the plant.

Phytoremediation has proven to be a suitable method for removing heavy metals from the soil with the help of plants. To examine the phytoremediation potential, the experimental study monitored the influence of high and low concentrations of heavy metals (Pb, Cd, and Zn) on Helianthus annuus L., as well as their accumulation in seeds, roots, stems and leaves. The experiment was carried out during one growing season in outdoor conditions, in pots with a volume of 5L in which Helianthus annuus L. was planted, and the soil was contaminated with these heavy metals in concentrations below and above the maximum allowable concentration prescribed by the Rulebook on Determining Permissible Quantities of Harmful and Dangerous Substances in Soil and Methods of Their Testing. After growth and development of the plant, the experimental research examined the accumulation potential of the plant, the growth of the plant itself and its ability to survive depending on different concentrations of heavy metals. By processing the obtained results, statistically significant differences of heavy metals were determined in individual parts of the plants, depending on the applied concentration. The highest concentration of Zn was recorded in the leaves of the plant in the amount of 18.21 mg/kg, and the lowest concentration in the stem, 3.92 mg/kg. The measured values of heavy metals Cd and Pb differ from the above because the lowest concentrations of these heavy metals were recorded in the seed, and were 12.02 mg/kg for Pb and 9.20 mg/kg for Cd, which is a statistically significantly lower determined value relative to other parts of the plant.

The biological performance of flocculent sludge in sequencing batch reactor for the treatment of fish canning wastewater was evaluated in terms of organic matter and nutrient removal by gradual increase of salt concentration in the nitritation-denitritation process. Salinity negatively affected the biological system performance in a way that reduced organic and nutrient removal. The removal efficiency of organic matter and nitrogen showed good performance below 20 g NaCl/L, while phosphate accumulating organisms activity was deteriorated and declined during whole experiment. Nitrogen removal occurred as ammonium oxidation with nitrite accumulation. Nitrite reduction was not affected by salt concentration.

Constructed wetlands, as an alternative to conventional methods, are systemsdesigned on the basis of the application of natural purification processes that take placein watery and swampy overgrown habitats, with certain microbiological groups. In thewastewater treatment process various types of constructed wetlands can be combinedto achieve a higher efficiency of the purification.In this study, the removal effectiveness of the organic substances from municipalwastewater was monitored, using a horizontal pilot - scale constructed wetlandutilizing Typha latifolia and Phragmites australis. In addition to the measurement oforganic substances content through COD, BOD and KMnO4 consumption, and totaldissolved substances (TDS) in influent and effluent, microbiological sample analysis wasperformed, monitored by total number of coliform bacteria.The aim of this study was to calculate the effectiveness of removing organicsubstances from municipal wastewater, depending on the season, as well as theeffectiveness of eliminating total coliform bacteria.The results of one-year research have shown that the removal effectiveness ofthe organic substances from municipal wastewater, expressed as the chemical oxygendemand (COD), was the highest in summer - 87.82% ± 2.83%, and the lowest in thewinter - 64.51% ± 5.89%. During the study, effectiveness of elimination of total coliformbacteria was 97.88 ± 0.80% and total dissolved substances 71.27% .

In this work was used activated sludge from the WWTP (wastewater treatment plant), in which with technique accumulation nitrificants and denitrificants, were prepared mixed bacterial cultures which showed the ability nitrification of ammonia- nitrogen to nitrate, as well as the ability of denitrification of nitrate nitrogen to gaseous nitrogen in municipal wastewater. As carbon source in the process of biological denitrification was used sodium acetate, in the ratio C/N=1 and C/N=2. Activity of mixed microbial cultures for removal components with nitrogen was determined by measuring the concentration of organic matter, expressed as COD, ammonia-nitrogen, nitrite, nitrate, pH, concentration dissolved oxygen, and the concentration of microbial biomass. Keywords: municipal water, activated sludge, nitrogen removal

: Ultrasonic flowmeter works on the principle of transmitting and returning ultrasonic waves that pass through the liquid, ie. fluid, and is used to measure the speed of fluid movement through a pipeline or some other structural form of fluid movement. By knowing the velocity of the fluid and the cross-sectional area of the pipeline or other system, the value of the volumetric or mass flow can be obtained indirectly. Fluid flow measuring device model OMNI TDI 200H owned by the laboratory of the Biotechnical Faculty was used for the first time to measure the flow of purified water at the outlet of the plant device of the training center "Grmeč", built as a pilot plant. The paper will describe the role and importance of flow measurement by the conventional method and present the results of the trial operation of an ultrasonic flow meter, model OMNI TDI 200H.