The purpose of diploma thesis is assessment of the operation of the Waste Water Treatment Plant in Dunajská Streda by LCA analysis. The analysis is performed for operating condition before reconstruction in 2002, for current operating condition (2016) and for condition with the predicted increase of population. Finally, the analysis is compared. Diploma thesis is divided into several parts. In introduction the processes and objects of wastewater treatment plant and the legislative requirements for the quality of treated waste water are described. The second part deals with the theory of LCA analysis. Assessment phases and impact methods are explained and the operations, cleaning process and objects of WWTP Dunajská Streda – Kútniky are characterised in this part.The core of the diploma thesis is the LCA analysis of the WWTP itself, which is done using OpenLCA software. The results obtained with the program will be transferred and presented using charts and graphs. Finally, the results of the analysis will be evaluated and compared.