Waste water includes high concentrate of polluting materials. The process of its purification is done in sewage treatment plants. It is defined as technological process. The diploma thesis is divided into three parts. Theoretical part describes the process of sewage treatment with special emphasis on new approaches – technologies supporting the effective use of sewage treatment and experiences with it in Slovakia and abroad. Experimental part was done on samples from sewage treatment plant Veľký Slavkov where the trial polygon of EKOSERVIS SLOVENSKO s.r.o. is found. In that place, new innovative technologies of microfiltration and ultrafiltration are performed on tertiary level. Experimental part of the work includes the consideration of microfiltration and ultrafiltration on the basis of comparison with the usual sewage treatment plant. We have considered the following issues: samples of ground in tributary after mechanical purification, outflow after microfiltration and outflow of ultrafiltration. The effectiveness of sewage treatment was taken into consideration with respect to selected biotests: the test of acute toxicity on cladocera (Daphnia magna), the test of inhibition in the process of root growing of higher useful plants (Sinapis alba), the test of inhibition (simulation) of tadpole growing (Lemna minor). The results of biotests lead us to the conclusion that there is a strong decrease of inhibitive influence in purified water after microfiltration and ultrafiltration with comparison of usual sewage treatment plant.