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Abstract

The aim of this study was to determine the impact of the temperature of wastewater in a biological reactor with activated sludge and the BOD5/N-NH4 ratio in the influent to the treatment plant on nitrification efficiency and the concentration of ammonium nitrogen in treated wastewater. Tests were carried out in a household wastewater treatment plant which collects and treats sewage from a school building and a teacher’s house. During the 3-year study, large fluctuations in the sewage temperature in bioreactor were noted which was closely related to the ambient temperature. There were also large fluctuations in the concentration of organic matter and the concentration of ammonium nitrogen in inflowing sewage. The influence of wastewater temperature in the bioreactor and the BOD5/N-NH4 ratio on the concentration of ammonium nitrogen in treated wastewater was determined using Pearson’s linear correlation. A statistical analysis showed that a 1°C decrease in the temperature of wastewater in the bioreactor increased the concentration of ammonium nitrogen in treated wastewater by 2.64 mgN-NH4·L-1. Moreover, it was found that nitrification depended on the ratio of BOD5 to the concentration of ammonium nitrogen in wastewater flowing into the bioreactor. An increase in the BOD5/N-NH4 ratio by 1 value led to a 5.41 mgN-NH4·L-1 decrease in the concentration of ammonium nitrogen.
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Abstract

This paper presents the use of multi-criteria analysis as a tool that helps choosing an adequate technology for a household wastewater treatment plant. In the process of selection the criteria of sustainable development were taken into account. Five municipal mechanical-biological treatment plants were chosen for the comparative multi-criteria analysis. Different treatment technologies, such as sand filter, activated sludge, trickling filter, a hybrid system - activated sludge/trickling filter and a hybrid constructed wetland system VF-HF type (vertical and horizontal fl ow) were taken into account. The plants’ capacities were 1 m3∙d-1 (PE=8) and they all meet the environmental regulations. Additionally, a solution with a drainage system was included into the analysis. On the basis of multi-criteria analysis it was found that the preferred wastewater treatment technologies, consistent with the principles of sustainable development, were a sand filter and a hybrid constructed wetland type VF-HF. A drainage system was chosen as the best solution due to the economic criteria, however, taking into consideration the primary (ecological) criterion, employment of such systems on a larger scale disagree with the principles of sustainable development. It was found that activated sludge is the least favourable technology. The analysis showed that this technology is not compatible with the principles of sustainable development, due to a lack of proper technological stability and low reliability.
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Abstract

One of the consequences of the dynamic technological development is the rapidly increasing amount of electro-waste (WEEE, e-waste). Because there are no uniform legal regulations regarding the ways of collecting such waste, the separate-collection systems used in various areas are not homogeneous, and they usually also differ in effectiveness. The aim of this study was to evaluate the electro-waste collection system implemented in Lublin (the largest city in Eastern Poland). Taking into account the fact that the reliability of a collection system depends on the degree of its adaptation to the functions it performs, the evaluation consisted in determining how big a problem improper electro-waste segregation was. The article presents the results of a study of the causes of citizens’ failure to properly manage e-waste and indicates what measures should be taken to amend the problem. During two research steps, 347 pieces of e-waste with a total weight of 77.218 kg were found in the analyzed waste samples (0.33% of all samples). This means that the mechanisms of selective e-waste collection still do not work correctly, despite the ten years of Poland’s membership in the EU and implementation of European legislation in this area. The fact that residents throw away electric waste into municipal mixed waste containers poses a serious problem for proper waste management – even if only a part of the e-waste is disposed in this illegal way. This indicates the necessity of improving waste collection (more frequent waste reception, convenient access to e-waste containers, raising public awareness, etc.).
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