Surface water pollution by herbicides from effluents of waste water treatment plants

Herbicide loads of urban and rural waste water treatment plant effluents were calculated over a one-year period by measuring the herbicide concentrations in 14-day mixed samples. More than three quarters of the total herbicide load of the effluent of the rural waste water treatment plant consists of isoproturon. Particularly large amounts of this substance contribute to the total herbicide load during the main application in spring and in early autumn. The measured loads of atrazine and the increased ratio between atrazine and desethylatrazine in spring indicate that atrazine is still applied in Germany. More than 80% of the total herbicide load of the effluent of the urban waste water treatment plant consists of diuron which is mainly used in urban weed control. The results show that also effluents of urban waste water treatment plants contribute to a great extent to herbicide pollution of surface water.