Phosphodiesterase type V inhibitors: Occurrence and fate in wastewater and sewage sludge

The contamination of wastewater and sewage sludge has been examined for three phosphodiesterase type V inhibitors sildenafil, vardenafil and tadalafil, active agents of Viagra^®, Levitra^® and Cialis^®, respectively. Sensitive quantification methods based on solid-phase extraction (SPE) and pressurized liquid extraction (PLE) followed by high performance liquid chromatography - tandem mass spectrometry (HPLC-MS/MS) have been developed to analyse these compounds in wastewater and sewage sludge.Effluent water of nine sewage treatment plants (STPs) has been analysed to assess the impact of the phosphodiesterase type V inhibitors on the environment. One municipal STP (Tarragona, Spain) has been thoroughly studied over the year 2008 (i) with respect to the distribution of these compounds among influent and sewage sludge and (ii) the elimination efficiency.The developed methods allowed quantification at trace concentrations. Sildenafil was present in all investigated samples at the low ng/L and ng/g range, respectively. Tadalafil was not detected or below the limit of detection (LOQ) in effluent water taken in Spain but in sewage sludge (12 ng/g -  < LOQ). Vardenafil was present only in one sludge sample and between 5 ng/g and < LOQ in effluent water. The overall removal efficiency of the STP in Tarragona (Spain) is 68%, 69% and 80% for sildenafil, tadalafil and vardenafil, respectively. This study shows for the first time the determination of these compounds in wastewater and sewage sludge.