Aim of the study:
The aim of the work is to assess the impact of pollution discharge limitation after the modernization of the ŁAM sewage treatment plant for pollutant loads in the middle and lower reaches of the Ner River.

Material and methods:
The source of data were information obtained from wastewater treatment plants regarding the basic indicators of pollution discharged to the river, flows and concentrations of pollutants in the cross sections of Ner and Warta. As an indicator, the share of introduced pollutants into the Warta river was assumed by the Ner river in the pollution load of the Warta River in the first measurement section on the Warta below the mouth of the Ner.

Results and conclusions:
In the first period, the average annual flow of Ner was about 10% of the average annual flow of Warta at the point below the mouth Ner and in the second period the similar level of 13.8%, whereas the load of pollution brought in by Ner average 27% nitrogen, 37% total phosphorus, 39% BOD5 and 28% total suspended solids in Warta water and in the second period similarly 27.9%, 42.6%, 19.8% and 19.6%. As in the first period, the lack of adequate response to the decrease in the phosphorus charge discharged by the waste water treatment plant for its content in the Ner's waters was found, and the increase of this indicator, while the BOD5 and total suspension ratio was reduced.