Issue 07-08/2023 (July-August)

The article presents the hydrogen goals and strategy of the European Union and Poland for 2021-2030. The methods of hydrogen production and storage were analyzed. Particular attention was paid to the possibilities of hydrogen distribution and problems related to this issue. The study also includes information on the impact of individual methods of hydrogen production on environmental aspects, with particular emphasis on carbon dioxide emissions. Projects related to the transport and production of hydrogen implemented by Polish companies are also described.

The article discusses the problem of water hammer in fluid networks (gas, water supply and in pipelines transporting twophase fluids. Mathematical models and selected computational algorithms are given .

The paper presents the complex stress state in a gas transmission pipeline caused by four factors: gas pressure, temperature changes, on-site bending and the soil gravity. The results of the analytical calculations are compared with the numerical model. The differences concern the hoop component of the thermal stress, which is lower obtained from the Finite Element Method than from the analytical method. The current design methods can be considered safe as long as there are no additional impacts along the entire length of the gas pipeline. In view of some uncertainty in the results, it is advisable to always verify the calculations with different methods.

Modeling intense rainfall of a given height and probability of occurrence is one of the greatest challenges of urban hydrology, and in particular safe drainage of areas, primarily due to the random nature of precipitation as meteorological elements. Access tometeorological data in Poland for many years was a significant obstacle in the process of updating knowledge and tools used in the design of systems for rational rainwater and snowmelt management. This paper presents a procedure for developing a simple precipitation model that enables the determination of the design characteristics of heavy rainfall with minimal access to measurement data. The method was presented on the basis of open meteorological data of the Institute of Meteorology and Water Management – National Research Institute, from the years 1986–2015, on the example of Szczecin. The presented method is universal and scalable for any locality, and its results have been compared with the solutions and methods available so far, such as the Błaszczyk model, the IMGW (Bogdanowicz-Stachy) model, the PANDa atlas or the results of the German DWD KOSTRA model available for Szczecin. As a result of the comparative analysis, it was noticed that the developed physical models give the best results among the tested solutions, for precipitation occurring most often at C = 1 and C = 2 years. For the remaining frequencies of C = 5, C = 10, and C = 30 years, the models developed using the original method could be outpaced only by the probabilistic models of the PANDa atlas.

The liquid fraction from the dewatering of digested municipal sewage sludge is a major technological challenge for sewage treatment plants. This fact justifies the need to search for effective methods of its neutralization. The aim of the study was to analyse the transformation of Chlorella sp. monoculture into granular microalgae-bacterial consortia (GKM-B) during the treatment of post-fermentation effluents in a hybrid photobioreactor (H-FBR). A stable taxonomic and morphological structure of GKM-B was obtained after 60 days of H-FBR exploitation. Its composition was dominated by Chlorella sp., Microthrix parvicella and filamentous bacteria type 1851 and type 1701.The development of the bacterial population had a significant impact on the increase in the GKM-B biomass concentration to the level of 4800±503 mgDM/dm3 and the increase in the efficiency of TOC and COD removal from the leachates to the level of 88.2±7.2% and 84.1±5.1%. The concentrations of N and P compounds were effectively reduced regardless of the composition and concentration of biomass in the system.

The article presents the characterization of one of the Communal Sewage Treatment Plants in the Masovian Voivodeship – the Communal Sewage Treatment Plant in Ciechanów. As part of the research section, qualitative measurements of raw and treated sewage were conducted to assess the content of biogens, including total phosphorus, total nitrogen, and organic matter expressed by indicators such as CODCr and BOD5. The evaluation of its effectiveness was analyzed, taking into account therelationship between the Equivalent Number of Inhabitants (ENI) and the quantity of generated municipal sewage sludge.

This article attempts to present biomethane as a green alternative to natural gas from the perspective of the European Green Deal supported by the Just Transition Fund. The financial viability of biomethane production was analysed based on market data. In order to anonymise the object used for analysis, the name Green Valley was adopted.