At the beginning of the 21st century, awareness was raised about the need for wastewater treatment, irrespective of the drainage of wastewater from household, industry or emerging precipitation, and washing of agricultural and other surfaces. The construction of wastewater treatment plants is more and more common, and wastewater treatment prior to release into the environment becomes imperative. Koprivnica-Križevci County is the administrative and industrial center of Koprivnica. For the purpose of nature protection and the preservation of human health, a wastewater treatment plant was built for town Koprivnica. The wastewater treatment plant is processed by biological process and it's among the rare wastewater treatment processes in Croatia which possesses so-called "Third level" treats waste water, effectively removing nutrients from waste water. The beginnings of the construction of a public drainage system in Koprivnica arise in the early seventies of the last century. Until 1989 waste water was discharged without any purification, the Bistra stream, Koprivnica's primitive waste water, was therefore well cleansed and below the prescribed water quality categories. The Koprivnica public drainage system is predominantly a mixed type, meaning that faecal and precipitation waters are run by the same system. All wastewater collected is taken to the main collector, and after the renovation it is discharged in the back of the Moždanski jarak that leads to the Bistra stream and the river Drava. The task of this work is to describe Koprivnica wastewater treatment plant.