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Phosphorus is a major substance that is needed especially for agricultural production or for the industry. At the same time it is an important component of wastewater. At present, the waste management priority is recycling and this requirement is also transferred to wastewater treatment plants. Substances in wastewater can be recovered and utilized. In Europe (in Germany and Austria already legally binding), access to phosphorus-containing sewage treatment is changing. This paper dealt with the issue of phosphorus on the sewage treatment plant in Nitra. There are several industrial areas in Nitra where record major producers in phosphorus production in sewage. The new wastewater treatment plant is built as a mechanicalbiological wastewater treatment plant with simultaneous nitrification and denitrification, sludge regeneration, an anaerobic zone for biological phosphorus removal at the beginning of the process and chemical phosphorus precipitation. The sludge management is anaerobic sludge stabilization with heating and mechanical dewatering of stabilized sludge and gas management. The aim of the work was to document the phosphorus balance in all parts of the wastewater treatment plant - from the inflow of raw water to the outflow of purified water and the production of excess sludge. Balancing quantities in the wastewater treatment plant treatment processes provide information where efficient phosphorus recovery could be possible. The mean daily value of P tot is approximately 122.3 kg/day of these two sources. The mean daily value of P tot is approximately 122.3 kg/day of these two sources. There are also two outflows - drainage of cleaned water to the recipient - the river Nitra - 9.9 kg Ptot/day and Ptot content in sewage sludge - about 120.3 kg Ptot/day - total 130.2 kg Ptot/day.

Aim of the study: Water shortage in arid regions should be addressed strategically. The proposes a framework for determining and prioritizing sustainable water management strategies based on Sustainable Development Goal 6. Material and methods: In this research, the water resources management strategies in the Central Desert Basin of Iran were derived by using brainstorming technique and analyzing Strengths, Weaknesses, Opportunities, and Threats (SWOT). Then, these strategies were ranked using the Analytic Hierarchy Process based on the sustainable development criteria. Results and conclusions: As a result, 9 strategies were developed, and assessed by the sustainable development criteria including four categories, economic, social, environmental, and technical ones. The result of assessing strategies showed that the strategy of "constructing a wastewater collection and a treatment network and reusing wastewater in industry and agriculture” was ranked in the first place and the strategy of “transferring water from the adjacent basins” was placed in the last rank. The results of sensitivity analysis showed that the model is sensitive to all of the sustainable development criteria except to the "feasibility" criterion. Additionally, the model is more sensitive to the criterion of the "socio-cultural acceptance and participation of stakeholders” rather than the other criteria. Generally, the high-ranked strategies are grouped as the continuous and improvement strategies whereas the invasive strategies are ranked last. These results reveal the willingness of the professionals to meet the challenges of water scarcity in the long term and relying on the strengths of the region rather than solving the problem at once which causes damages to the environment and natural resources.

Aim of the study: This study presents an opportunity to determine a value of longitudinal dispersion and is focused on the comparison of seasonal variation of the longitudinal dispersion predetermined by natural conditions of the river aquatic zone. Material and methods: The dispersion of a pollutant tracer was simulated by HEC-RAS model and by one dimensional advection-diffusion equation. Determination of longitudinal dispersion coefficient was done on the base of tracer experiments (2 kg NaCl in 10 l H2O) carried out in March, August and October 2019. Both methods were applied to the Okna River localized in the Eastern Slovak Lowland Results and conclusions: Result showed, that model HEC-RAS very sensitive reacted to the changes of dispersion and vegetation in the river. Estimated longitudinal dispersion coefficient for Okna river by equation during the year, was in a range from 0.093 to 1.08 m2s-1 and by the HEC-RAS it was from 0.220 to 1.850 m2s-1. Results could represent different values of longitudinal dispersion simulated by the model or equation. Obtained coefficients have a wide application. A main use of these numbers is with simulation of the spread of accidental pollution in rivers. Also, it can be applied to streams with similar characteristics. Results showed important role of seasonal variation of longitudinal dispersion coefficient that must be assumed in simulation of pollution spreading in rivers.

Present state of air quality is determined according to emission and imission situation of basic pollutants. According to obtained information about the state of air quality the development of imission and emission has at the present time decreasing tendency caused especially by industrial production innovations in European countries, with slight rises renewable energy sources for electricity production, but especially the effort to improve the condition relates to the use of mandatory quotas and pollution charges in the European Union. The aim of the this article is the review of emission development in the year 1998 up to 2013 for Central European countries - Slovakia, Czech Republic and Poland and their comparison to the European average value of released emission. As pollutants were evaluated NOx and particulate matter PM10, PM2,5, which in the last few years contaminate the air and in particular the main environment.

The study presents variation of wastewater inflow and its components during a year. We considered a situation with and without precipitation. The two renovated wastewater treatment plants were selected to analyse the available parameters and relation between them. Both wastewater treatment plants served to treat domestic and industrial wastewater with similar characteristics. One of them is only for the town purposes; second one serves for the surrounding villages. The relation between the concentration of pollutants and a flow of wastewater is very low. The correlation and a coefficient of the determination between pollutants were over 0.5.

Water pricing and reducing the costs of the implementation and maintenance of irrigation systems have been a challenging topic for a long time. Water pricing issues combine two complex dimensions. The first dimension is the economy of the farm and its association with the broader economic system and farming practices. The second dimension is the hydrology and interconnection of the plot with the irrigation system, the river basin, and the underlying water policy framework. Accordingly, this study aimed to investigate how the institutionalization of water applied would affect water productivity through the implementation of a water-pricing policy. To this end, this study formulated a Positive Mathematical Programming (PMP) model with a gross margin maximizing objective function to assess the data collected from 213 farms in Hamadan-Bahar Plain, Iran. The results revealed that a water-pricing policy can change the cropping pattern and also irrigation system within the limitations of the case study. It can also be a driver to motivate farmers to use a modern and more efficient irrigation system. The potential environmental benefits from the improved on-farm irrigation efficiency depend on the government's ability to prevent the extension of the irrigated area. In absence of such controls, the aquifer depletion will be accelerated. Therefore, an appropriate water-pricing policy could improve water productivity and also reduce water applied.