[en] After the uranium mining and milling waste water was processed by lime milk, the uranium concentration can not often reach the environmental emissions requirements. Based on the study of relevant information and references, the influence of ferric iron for the reducing uranium concentration after the contained uranium effluent was processed by lime milk neutralizing treatment was carried out in the laboratory, the laboratory results was applied into industrial production. By experiment, the dosage of addition of amount of ferric iron is determined. The experimental results indicate that the addition of ferric iron in the uranium mining and milling waste water can reduce the uranium concentration, therefore, uranium concentration in the effluent can meet environmental emissions requirements after the process. (authors)