Drugs in water: incomplete removal by wastewater treatment plants
Drugs in water: incomplete removal by wastewater treatment plants
This post was originally published on the Veterinary Prescriber website in 2013
A proportion of the drugs used in human and veterinary medicine ends up in the environment. Drugs used by humans are excreted in urine or faeces and end up in wastewater in their original active form or as active or inactive metabolites. Unused drugs can also enter the aquatic environment when flushed down the toilet, poured down the drain or thrown away with household waste that is then deposited in landfills etc.
How effective are wastewater treatment plants at removing the various pollutants? A French study investigated micropollutants in effluents from wastewater treatment plants between 2006 and 2009. The concentrations of the pharmaceuticals studied were measured in raw wastewater entering treatment plants and in wastewater treated by a succession of different processes:
Primary treatment: after a first step to remove coarse solids and fats, solid particles in the wastewater are left to settle to the bottom
Secondary treatment involves an “activated sludge” process, followed by a second settling out of solids
A tertiary treatment, such as sand filtration or ultraviolet or ozone disinfection, is applied in plants equipped with these types of facilities
The programme studied 127 substances, 32 of which were drugs (beta blockers, antibacterials, antidepressants, nonsteroidal anti-inflammatory drugs, a lipid lowering drug and bronchodilators); it studied domestic wastewater treatment plants in rural and urban areas of France and Spain that were representative of the different processes used for elimination of pollutants.
The study (which only looked at a limited number of wastewater treatment plants, water samples and drugs) found that treatment plants do not completely remove the drugs present in wastewater. The effectiveness of drug removal varies depending on the drug and treatment processes. However, many drugs (acebutolol, atenolol, sotalol, roxithromycin, sulfamethxazole, diclofenac, theophylline) were still detected after tertiary water treatment.
European regulations define environmental quality standards for 33 “priority substances” (including mercury, polyaromatic hydrocarbons) in surface water. As of late 2012, the list did not include any pharmaceuticals. A proposed amendment to the directives that govern water policy would add 15 more substances to the list: industrial chemicals, dioxin and dioxin-like compounds, substances used in biocides, plant protection products and, for the first time, three drugs (17-alpha-ethinylestradiol, 17-beta-estradiol and diclofenac).
The presence of drugs in wastewater and their persistence after water treatment are good reasons to avoid the overconsumption of drugs and to encourage people to dispose of unused medicines through organised take-back schemes.
This is a summary of a report published in the independent medical publication Prescrire International.Drugs in water: incomplete removal by wastewater treatment plants. Prescrire International 2013; 135: 52–4.
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