Guide substances

At least 140 tons of drug residue ends up in the sewer via urine and feces every year. As a society, it is not possible to live without medicines. Unfortunately, using medicines, whether it is oral, cutaneous or intravenous, a (large) part eventually ends up in our wastewater. As a consequence, this wastewater is entering the Waste Water Treatment Plants (WWTPs), before the water is discharged into the surface waters.

The approach 'Medicine residues from Water' of the national government focuses on various sources, but also on the possibilities of an extra purification step at WWTPs to extensively remove micro-pollutants from urban waste water, including medicine residues,. Pilots with innovative purification techniques and demo installations at existing WWTPs have been and will be tested under Dutch practical conditions in the coming years. These include powdered carbon, ozone, granular activated carbon, sand filtration, membrane filtration, ion exchange, UV, H2O2 or combinations of them.

The effectiveness of these purification steps in the pilots/demos will be monitored on the basis of biological effect measurements and by measuring a few (guide) substances. By measuring the same guide substances in all pilots/demos, the effectiveness of the various techniques can be easily compared. Eleven guide substances are proposed by the Ministry of I&W, namely: carbamazepine, propanolol, trimethoprim, metoprolol, benzotriazole, a mixture of 4-methylbenzotriazole/5-methylbenzotriazole, hydrochlorothiazide, sulfamethoxazole, diclofenac, clarithromycin and sotalol. This list has now been expanded with eight other guide substances, namely; amisulpride, azithromycin, candesartan, citalopram, furosemide, gabapentin, ibersartan and venlafaxine.

The selection of these guide substances is only intended to unambiguously monitor the performance characteristics of the purification techniques; the guide substances itself give no indication of any environmental impact.

The Foundation for Applied Water Research (STOWA) and the Ministry of Infrastructure and Water have commissioned the water board laboratories to unite in the Integrated Laboratory Consultation on Water Quality Managers (ILOW) for the development of a robust and unambiguous sampling and analysis method for micro-pollutants in waste water.

Het Waterlaboratorium is working together with the ILOW labs, and a uniform method has now been developed for the pre-treatment and analysis of these nineteen guide substances. For analysis of all the guide substances, a LC-MS/MS method is used.