Little time? At the end of the text there is a summary.
We encounter chemicals everywhere in everyday life. In the morning with the body care, when we reach for the toothpaste or put us with shampoo and soap in the shower. When using cosmetics, detergents, detergents or medicines.
The residues of all these remedies and therefore thousands of chemical compounds enter the sewer system via the drain or toilet. For this purpose, rainwater flushes residues of pesticides or the abrasion of car tires in the Gullis. The chemical cocktail reaches the sewage treatment plant at the end of the sewage system.
But so far the wastewater technology in Germany is not designed to remove such so-called trace or micro-pollutants from the water. And so a large part ends up in rivers and lakes and potentially also in the human food chain. Or could seep into groundwater in some regions.
Trace substances: danger to the ecosystems
What are trace substances?
So-called anthropogenic micropollutants, sometimes called micropollutants , often get into the water through the use of everyday objects. Through the body, which eliminates drug residues, but also through the sink and sink into which chemicals from the household or cosmetics are introduced. Trace sources include, for example, hormones, food additives, disinfectants, preservatives or biocides .
Thousands of substances are among the potentially environmentally relevant micropollutants, not all of which have been detected and new ones are constantly being added. The fact that the tiny concentrations in the water can be detected today is also due to an improved analysis technique in recent years. Nevertheless, experts are assuming an increase in trace substances. But they do not just get into the environment with the wastewater. Other sources include industrial plants but also agricultural land , where chemicals such as pesticides or fertilizers or animal medicines are used and are flushed by rain into canals and bodies of water. In this way, they also get into the water from building materials, facades and tire wear on asphalt.
What do trace substances do?
Not all trace substances and degradation products are dangerous, some can be broken down by natural processes. A direct danger to humans has so far not been proven . But with the entry into the waters, the substances also enter the food chain. In addition, some damage the ecosystems.
The consequences may be inhibition of growth, decreased numbers of offspring, behavioral changes and metabolic disorders . The lowest concentrations are found in algae and other plants. The higher an animal is in the food chain, the higher is its pollutant load as a rule.
In what quantities do they get into the water?
Trace substances enter the rivers in large quantities every day. There are hardly any exact figures - just because of the amount of individual substances. Especially medications result in significant entries. Consumption of the analgesic diclofenac in 2012 was around 80 tonnes per year in Germany. Studies for orally taken drugs show excretion rates of drugs between 30 and 70 percent. An evaluation of the Federal Environment Agency from the years 2009 to 2011 shows that a total of 27 different active pharmaceutical ingredients in concentrations of more than 0.1 micrograms per liter in German surface waters were measured.
How could trace substances be avoided?
The entry into the waters can never be completely avoided. But by meaningful behavior , every citizen can contribute , writes the Bavarian State Office for the Environment:
Although it has not yet been conclusively explored, which damage such substances cause in the ecosystem. However, there are sufficient indications from various studies that at least some of the substances should not get into the water. Substances with a hormone-like effect may be a danger to fishermen.
Fish, for example, changed their behavior in studies and became much more daring when they came in contact with these substances.
So what to do to reduce the chemical load in the water?
Scientists, sewage treatment plant operators, environmentalists and politicians have been discussing this for a long time. In the background there is a dispute over the construction of a new sewage treatment plant, which has been available for years, but has so far only been voluntarily installed by a few sewage treatment plant operators.
This is how a wastewater treatment plant works (click on the numbers):
1
The waste water first passes through a rake, which holds back coarse debris (paper, bottles, branches, cans, etc.) and removed with an automatic scraper .
2
In the sand trap , the drainage channel widens , which reduces the speed of the further flowing wastewater and deposits coarse materials such as gravel and sand, which are heavier than water, at the bottom.
3
In the primary clarifier, the water is held back for about two hours. In this large, rectangular or round basin, the fine suspended matter can settle on the ground as mud. This raw sludge is sucked off, thickened (10.) and transported into a digester (11.) . So-called lightweight materials, which are distended to the water surface (fats, mineral oils, etc.) are drained into a special container.
The first three stations together form the first cleaning stage. Since the treatment of the waste water takes place here only in a mechanical way, it is called mechanical cleaning. Here it is possible to extract about 30 percent of the total amount of pollutants fed into the system.
4
In the second purification stage , also called biological purification, one makes use of a thoroughly natural process by creating favorable living conditions for microorganisms in an activated sludge basin by supplying oxygen, which are able to absorb dissolved organic wastewater in connection with atmospheric oxygen as food to build one's own organism. It also pollutants, such as heavy metals, are included.
5
Many microorganisms form colonies, which sink as visible sludge flocs in the following sedimentation tank to the soil and are either pumped back again into the aeration tank or transported to the primary clarifier (3) for the purpose of sludge disposal.
With the disposal of the sewage sludge from the wastewater so the biodegradable pollutants are removed. In smaller sewage treatment plants you will often find trickling filters, round concrete boilers, loosely filled with porous rocks. Here, the large surface is important on which bacteria settle and form a "biological lawn" (corresponding to the sludge flakes in the activated sludge process), when raining over wastewater. After passing the mechanical and biological purification stages, the wastewater is now about 90 percent cleaned.
6
From a precipitating metering station , a chemical solution is added to the wastewater at the same time with thorough mixing.
7
As an example in the display panel, phosphate-rich water from the secondary clarifier number 5 first reaches a flocculation basin
8th
This precipitant chemically reacts with the phosphates to form a water-insoluble compound. The residual dirt "flocculates" and can settle in a secondary clarifier as sludge, which - thickened - is fed to the digester.
9
The purified water can now be discharged into a natural body of water.
10
With the help of thickeners , this content is on
96 percent
lowered and thereby halved the volume.11
Now, the sludge is transported to a digester, where under exclusion of air putrefactive bacteria in a fermentation process at 35 degrees Celsius produce a digester gas, which consists to 2/3 of methane and 1/3 of carbon dioxide.
12
This gas is stored in a container and used for heating purposes.
13
After about 4 weeks, the sludge is rotted, odorless and can be dehydrated in dry beds.
Source: BMU
The opponents of this so-called 4th stage of purification consider them too expensive and not efficient enough. Even though the associated households would incur higher water costs (for example, between five and 25 euros per year), not all substances are removed or completely reduced. In addition, one must first of all try to reduce the input of chemical substances. Even information campaigns on the proper handling of household chemicals could prevent trace elements from even getting into the water, argue many wastewater treatment plant operators. For the entries are not only the consumers but also the chemical industry or agriculture jointly responsible, which would also have to make a contribution.
Such measures at the source are important, argue the proponents of technology. But that will not be enough to protect our waters everywhere, says the Federal Environment Agency. The new technology can not be dispensed with, at least near major cities or in sensitive water regions near drinking water catchment areas.
This is how the fourth cleaning stage works
The sewage treatment plant Ulm Steinhäule is one of the few plants in Germany that have a fourth purification stage. Thus, trace substances such as drug residues can be better removed from the water. The picture shows the newly built section. In Baden-Württemberg and also in North Rhine-Westphalia are already some facilities. But many operators are skeptical.
A wastewater treatment plant that processes municipal wastewater normally consists of three purification stages. In the mechanical coarse dirt is removed. In the biodegraded bacteria, organic material. And the chemical level restrains the algae nutrient phosphate. In the fourth stage, the engineers in Ulm use activated carbon powder - it turns the water black.
Here the activated carbon is metered. The plant consumes about 300 tons of powder per year.
About these screw pumps, the water is passed to the so-called contact reactor. One of the screws carries about 1500 liters of water per second.
Trace substances are absorbed by the activated carbon in the four-meter-deep contact reactor. The activated carbon with its porous and brittle structure has a huge inner surface. The water stays here for up to 75 minutes.
Subsequently, the activated carbon must again from the water. It gets into a sedimentation basin where the coal sinks to the bottom. To aid the process, a precipitant and a flocculant are added. The first substance causes solutes to solidify again. The flocculant ensures that the substances are stored together.
Christian Hiller is one of the engineers in Ulm who supervise the plant. Since 2015, the fourth cleaning stage has been in operation.
For visitors, there are billboards throughout the entire complex that explain the individual steps.
After the sedimentation basin, the water is filtered. There are two filter lines with ten chambers each. The two-layer filter consists of one layer of anthracite coal and one of quartz sand.
The filter must be backwashed regularly to remove dirt. The direction of the water is reversed for a short time. For these pumps are responsible.
The individual sections of the fourth purification stage are all accessible underground and connected by long tunnels.
Engineers are currently testing other processes on a small scale that could further improve plant performance. In addition to ozone, this system is being tested with a spaghetti membrane filter - this is the elongated tube on the right in the picture.
In Ulm, citizens pay five euros more a year for the new technology. On other systems, however, the costs could be slightly higher.
A settlement of the dispute was hoped for by all participants of the Federal Government. The Federal Ministry for the Environment (BMU) had set up a working group, where all interest groups were struggling for solutions. Companies, environmentalists, water management and politics were in discussion for three years in the so-called trace substance dialogue.
In Berlin, after long negotiations, the results were recently presented, from which one hopes for cleaner waters. Concrete decisions were not made. Instead, different strategies are to be tested in a one-year test phase :
- Since many substances are still insufficiently investigated, those that are particularly relevant for water conservation should first be better investigated.
- In addition, according to BMU, manufacturers of chemical products want to examine how the use of chemicals can already be reduced during production.
- A big problem so far is that many people dispose of old medicines in the toilet. Information campaigns at community colleges are intended to sensitize citizens.
- X-ray contrast media for medical diagnoses are extremely durable in the environment. Pilot projects are currently underway to reduce their entry. In hospitals, the use of separate toilets is checked so that contaminated faeces do not get into the sewage.
- With a checklist, sewage treatment plants can check whether another cleaning stage on their plant is economically and ecologically worthwhile, or that preventive measures may also be sufficient to improve water protection in their region. Since the wastewater organization is a matter for the Länder, there were no uniform evaluation criteria.
What is worth to you clean water?
The water industry welcomes the measures. A spokesman for the Association of Municipal Enterprises (VKU), which also includes drinking water suppliers, warned that prevention is better and cheaper than aftercare: "The problem must be tackled at the root, so the cause of the entries."
Environmental organizations and politicians, on the other hand, were disappointed. "After around three years of dialogue, the report does not contain a single concrete measure to protect our water from micropollutant pollution, and new information campaigns alone will not keep our water clean," said Greens environmental spokeswoman Bettina Hoffmann.
In an application that the Greens want to make in the Bundestag in the spring, they also called for an industrial fund for clean water, so that rising costs for water purification are not left to the consumer alone. Such funds should include pharmaceutical companies, manufacturers of detergents and cosmetics as well as industrial farmers.
Role model Switzerland
In addition, a prohibition list of hazardous substances should be set up. Such water-polluting substances should then no longer be used for pharmaceuticals, pesticides, as well as detergents and cleaners. In addition, the Greens hope for additional substances to label the products in order to create more transparency for consumers.
The expansion of wastewater treatment plants could also be financed from the industry fund. Because the new technology is not cheap. For example, Germany would incur costs of 470 million euros annually if the 240 largest plants were retrofitted, the Federal Environment Agency had calculated.
Incidentally, one step further in terms of wastewater treatment is already in Switzerland. There the fourth cleaning stage is already decided thing. It will be installed on a hundred of the 700 wastewater treatment plants over the next few years and funded by a nationwide waste water tax.
In summary: In order to reduce the entry of chemical residues into German waters , the Federal Government has presented a new strategy. Accordingly, the entry of chemicals should already be reduced at the source. In addition, wastewater treatment plant operators should receive guidance as to whether it would be worthwhile to install a new but expensive technology. Environmentalists and Greens criticize the strategy as inadequate and call for the establishment of an industrial fund for financing.