Drug residues in drinking water cannot be adequately filtered out by normal treatment of the water in the wastewater treatment plant. What are the consequences? We explain what companies and consumers can do.
Wastewater treatment: how is water purified?
Conventional wastewater treatment plants cannot adequately filter pharmaceutical residues. In the second stage, the mostly mechanically pretreated wastewater is purified with the help of microorganisms – i.e. bacteria. In this process, mainly organic substances are broken down, for example from food residues and feces.
In the more advanced wastewater treatment stage, chemicals are used to precipitate and flocculate other substances such as phosphates and heavy metals and remove them from the water. What remains is bulking sludge, which must be stabilized. The solid residues are used for agricultural purposes, deposited in landfills or incinerated.
Degradation of pharmaceuticals
How the degradation of pharmaceuticals occurs and which degradation products are formed is only clarified in individual cases. It is likely that drugs are not only converted to carbon dioxide and bacterial mass during biological, oxidative degradation. Degradation products are probably also formed, which cannot be detected with today’s analytical methods.
Dr. Manfred Hilp, a pharmacist and graduate chemist, writes in the Pharmaceutical Journal that ibuprofen, for example, shows “poor environmental behavior”. It was detected in drinking water, while in the case of acetylsalicylic acid (ASA), salicylic acid was found only in traces in flowing waters, despite its much higher consumption.
The painkiller paracetamol is also considered to be quite degradable. In contrast, diclofenac is a cause for concern because it harms birds and fish. Hormone residues from the birth control pill can affect animal reproduction.
Modern methods called for
Scientists and the Federal Environment Agency are calling for drug residues and other chemicals to be completely eliminated from wastewater. To achieve this, they say, wastewater treatment must be technologically upgraded as part of a fourth treatment stage – nano- or microfiltration or activated carbon processes are in demand, for example: Chemical micropollutants could be efficiently filtered out of wastewater via oxidation with ozone and/or adsorption on activated carbon filters.
Pharmaceutical companies and consumers are also in demand
However, science and environmental authorities are calling for more than just an additional treatment stage. It is just as important that as few pharmaceuticals as possible find their way into wastewater. For example, pharmaceutical companies could disclose the environmental data of new drugs in the approval process.
Consumers should also dispose of their medicines in residual waste instead of down the sink or toilet. Alternatively, expired or no longer needed medicines can be taken to the pharmacy for disposal.
(Still) no harmful effect on human health
There is still no reason to give up tap water. But as life expectancy increases and more and more medicines become available without prescription, the amount of medicines taken – and later excreted – will also increase.
Certainly, there is a need for action in filtering drug residues in water, but the concentrations detected of drug residues in water are very low and, according to current knowledge, harmless to humans. Moreover, findings of drug residues in drinking water are the exception; there is no detectable effect of these extremely low concentrations, which are far less than therapeutic doses.
