Influences of drugs on the oxygen uptake rate and biosorption of activated sludge.

To prevent pollution of the water environment by drugs, we evaluated factors affecting the elimination of drugs by inducing reactions between the pharmaceutical chemicals originating from the drugs and activated sludge (AS) in test tubes. Of 30 pharmaceutical chemicals examined, ibuprofen (IBP) as an anti-inflammatory drug most markedly inhibited the oxygen uptake rate (OUR) of AS, and its IC50 was 172 mg/l. The IBP elimination from the wastewater was due to the significant biosorption by AS and was based on the time-response and dose-response relationships. In the pharmaceutical chemical group (1) (diclofenac Na, ketoprofen, indomethacin, salicylic acid, mefenamic acid, phenylbutazone, chlorpromazine.HCl, furosemide, tolbutamide and warfarin K) showing a relatively significant OUR inhibition (IC50, 200-500 mg/l), protein binding (75-99.7%), and the biosorption by AS also tended to be significant. In group (2) (acetaminophen, kanamycin.H2SO4, antipyrine, ethenzamide, gentamicin.H2SO4, cyclophosphamide.HCl, aminophylline, procainamide.HCl and cimetidine) showing a negligible OUR inhibition (IC50 > or =2000 mg/l), the protein binding was slight (0-74%), and biosorption by AS was also negligible. For the IBP and group (1), AS was pretreated with a certain excessive amount of each pharmaceutical chemical, and the qualitative OUR curves of the AS-synthetic sewage-II after washing showed a significant OUR inhibition immediately after the start of the reaction. Group (2), as well as the control group showed no OUR inhibition. These results suggest that the degree of OUR inhibition of AS by pharmaceutical chemicals is affected by the protein binding and the degree of biosorption. This suggests that pharmaceutical chemicals with a significant protein binding possibility can be eliminated from the wastewater by binding to AS.