Tracer studies on the removal of water endangering substances from municipal waste water

The presentation deals with the behaviour of selected water endangering compounds and with possibilities of their holdback or elimination in water treatment plants. The investigations were carried out by use of 82Br-bromoxynil and sodium-32P-hydrogenphosphate in a pilot plant for the biological clarification of municipal waste waters. It is shown that only < 5% of an input concentration of 5 ppm of the herbicide bromoxynil (3,5-dibrom-4-hydroxybenzonitril), as a selected example for a water endangering substance, is degradated during the passage of the aqueous phase through the plant. The degradation of bromoxynil includes the debromation of the compound. A notable adsorptive fixation of the active substance takes place at the biosludge. The extent of elimination of phosphate (initial concentration cP > 10 mg P/l) from municipal waste water it was found that the phosphate concentration of the biologically cleaned water leaving the pilot plant is < 2 mg P/l. The pilot plant and details of the tracer experiments are described. (author)