Advances in the analysis of organic trace compounds revealed that many of the in high amounts prescribed pharmaceutical active components as well as diagnostic agents are not removed by conventional waste water treatment techniques and that some of them can accumulate in the aquatic environment. Because most of the compounds applied in medicine are excreted via urine the emission into the aquatic environment could be reduced if the urine is separated at the source and treated by a specific process. In the project PharmaTreat it was studied if the reductive treatment with zero-valent iron is a suitable, simple and low cost process for the treatment of urine. The results show that the selected antibiotics (Ciprofloxacine, Piperacillin, Cefuroxime), cytostatic drugs (Ifosfamide and Methotrexate) and iodinated X-ray contrast media (Iopromide and Diatrizoate) are transformed by the treatment with zero-valent iron. The reaction rate constant depends highly on the pH. Under acidic conditions the mechanism of the transformation is most probably the reaction with adsorbed atomic hydrogen which is produced on the iron surface. The increase of the pH-value from 3 to 7, which might happen if the solution is discharged into the waste water system, leads to the precipitation of the dissolved iron resulting in a strong removal of the transformation products out of the solution by co-precipitation. The toxicity of the remaining transformation products was determined using the growth inhibition test (DIN 38412-37). It could be demonstrated that the biological impact of the pharmaceuticals is reduced by the transformation with zero-valent iron. By using the Zahn-Wellens-Test (DIN EN ISO 9888) it could be shown that the transformation products are better biodegradable in contrast to the original compounds, except for the iodinated Xraycontrast media. The treatment of one cubic meter urine costs 9.88 Euro. The cost estimation is based on conditions with the lowest material consumption and not on the reaction time. According to the calculated price for on cubic meter the treatment of about 6,525 m3 urine (the amount of urine produced in all hospitals of Berlin) costs ca. 64,500 Euro/a. By accelerating the reaction the treatment time can be shorten but the specific material consumption is higher whereas the energy costs are lower. In dependence of the actual prices for iron, acid and electricity the costs can be optimized for the treatment.
Treatment of urine with zero-valent iron to minimize the aquatic pollution with compounds emitted by hospitals