Assessing the changing parameters of water quality at different points in the river–reservoir system can help prevent river pollution and implement remedial policies. It is also crucial in modeling water resources. Multivariate statistical analysis is useful for the analysis of changes in surface water quality. It helps to identify indicators that may be responsible for the eutrophication process of a reservoir. Additionally, the analysis of the water quality profile and the water quality index (WQI) is useful in assessing water pollution. These tools can support and verify the results of a multivariate statistical analysis. In this study, changes in water quality parameters of the Turawa reservoir (TR), and the Mała Panew river at the point below the Turawa reservoir (bTR) and above the Turawa reservoir (aTR), were analyzed. The analyzed period was from 2019 to 2020 (360 samples were analyzed). It was found that TN, NO₂-N, and NO₃-N decreased after passing through the Turawa reservoir. Nevertheless, principal component analysis (PCA) and redundancy analysis (RDA) showed that NO₂-N and NO₃-N contribute to the observed variability of the water quality in the river-reservoir system. PCA showed that pH and PO₄-P had a lower impact on the water quality in the reservoir than nitrogen compounds. Additionally, RDA proved that the values of the NO₃-N and NO₂-N indicators obtained the highest values at the aTR point, PO₄-P at the bTR, and pH at the TR. This allows the conclusion that the Turawa reservoir reduced the concentration of NO₂-N and NO₃-N in comparison with the concentration of these compounds flowing into the reservoir. PCA and RDA showed that both parameters (NO₂-N and NO₃-N) may be responsible for the eutrophication process of the Turawa reservoir. The analysis of short-term changes in water quality data may reveal additional sources of water pollution. High temperatures and alkaline reaction may cause the release of nitrogen and phosphorus compounds from sediments, which indicates an increased concentration of TP, PO4-P, and N_org in the waters at the TR point, and TP, PO₄-P, and NH₄-N concentrations at the bTR point. The water quality profile combined with PCA and RDA allows more effective monitoring for the needs of water management in the reservoir catchment area. The analyzed WQI for water below the reservoir (bTR) was lower than that of the reservoir water (TR), which indicates an improvement in water after passing through the reservoir.

The article presents the results of research aimed at determining the catchment areas that pose a risk of nitrogen pollution of the waters of the Mała Panew river. The research was carried out in 13 permanent monitoring points located on the Mała Panew. The location of the points ensured the representativeness of the water quality results for parts of the catchment area with a homogeneous type of land use. Concentrations of nitrate-nitrogen (NO3-N) and total nitrogen (TN) were determined in the samples taken. The content of (NO3-N) in the third quarter of the year and its relation to the value obtained for the first year quarter may be an indicator of the impact of agricultural activities on the quality of water in streams. In the case of agricultural catchments, the lowest concentrations of NO3-N and TN occur in the third quarter of the year and are significantly lower than in the first quarter of the year. The demonstrated seasonal variability of nitrate nitrogen concentrations in agriculturally used areas may be used to determine the type of pressure not allowing to achieve good water status in the surface water body. It was shown that the highest unit increments occurred in areas with a high proportion of forest.

The use of plants and natural processes for wastewater treatment is an issue that arouses interest among technologists and scientists around the world. The aim of the article was to analyze the influence of the air temperature and insolation on the removal of nitrate nitrogen from the wastewater treated in the hydroponic system, under greenhouse conditions. Samples of sewage for its quality tests were taken from a wastewater treatment plant (WWTP) located in the southwestern part of Poland. Data regarding daily sunshine duration and average daily air temperature values in selected periods of 2013–2016 come from a meteorological station located 30 km from WWTP. The conducted research and analyses of the results clearly indicate that under moderate climate conditions, the amount of solar radiation reaching the Earth’s surface is insufficient to ensure the year-round, effective wastewater treatment process in the hydroponic system. In the case of air temperature, no correlation was found between the tested parameters, which indicates the lack of temperature influence on the efficiency of NO₃ removal from the wastewater by macrophytes growing in the lagoon.

Treatment of wastewater produced in Service Areas (SA) located on expressways and highways is a worldwide problem because of increasing amount of roads and specific composition of those kinds of sewage. Insufficient removal of pollutants from wastewater discharged into surface water may cause serious environmental problems. In the present study efficiency of treatment of wastewater with high ammonium concentration in biological membrane system used on SA was investigated. Concentrations of ammonia nitrogen in wastewater flowing into bioreactor in none of the tested objects did not fall below 99.0 mg of N-NH₄·dm⁻³. Because of high ammonium content in sewage and high pH reaching value about 9, it is almost impossible to create favorable conditions for microorganisms that run purification processes resulting in low efficiency of phosphorus and nitrogen removal (reduction of biogenic compounds did not exceed 15%). Treatment of wastewater consisting mainly of urine with commonly used biological membrane technology has to be widely tested to perform suitable quality of discharged wastewater, to provide safety of surface water environment.

The latest research focused on the analysis of algal growth and the dynamics of their growth use the laser diffraction technique, enabling determination of the volume fraction of suspended particles with specific diameters in aqueous solution as well as their fractal dimensions. This study focuses on the possibility of using a laser granulometer to assess the growth dynamics of algae growing in treated wastewater in a hydroponic system, supported by artificial lighting with the use of light-emitting diodes (LEDs). On the basis of the measurements, the fractal dimension (Df) of algae was determined. An attempt was made to apply the modified Avrami equation describing the crystallization process for the analysis of algae growth dynamics in wastewater. Presented results show that the fractal dimension of suspended matter, largely created by algae, in the case of additional lighting of the hydroponic system at night, takes lower values (Df ~ 1.0) than in sewage without additional light source (Df ~ 2.0). In each measurement series, the fractal dimension of particles in the tank with lighting in the end of the experiment was about 33–43% lower than in the tank without LEDs. The analysis of changes in particle diameters calculated on the basis of Avrami equation largely corresponds with the stages of algae growth. During the measurement series with lower air temperatures, the growth of algae in the tank with additional light was faster than in the tank without LEDs. The obtained information can be the basis for determining the effective method of removing algae from wastewater treated in the hydroponic system, before they are discharged to the receiver in order to prevent the outflow of increased concentrations of total suspended solids.