Strange objects sometimes arrive in German sewage treatment plants with wastewater. Technicians and engineers have already found jewelry, smartphones or even folding knives. Many sewage treatment plants have a small collection in which they keep the strangest finds. There are then also ancient toothbrushes or artificial dentures. A look at the pieces is sometimes like looking into the bathroom of the Germans.
To remove such rubbish with rakes and sieves is simple. But substances also reach the plants, which can neither be fished with the tools for coarse from the stinking sewer broth, nor with the remaining two purification stages. Not with the biological, in which high bacterial concentrations decompose organic matter. And not with the chemical that brings the algae nutrient phosphate out of the water.
The persistent substances that remain in the water include, for example, drug residues: painkillers as well as antibiotics. But also of cosmetics, detergents or other household chemicals. And also substances from industry, veterinary medicine or agriculture.
They all get into the wastewater daily and in different ways: as excretions from the body via the toilet. But also because people dispose of their old medicines or other home poisons in the toilet. In addition comes with pesticides contaminated rainwater, which also ends up in the sewer system. A whole cocktail of such substances reaches the sewage treatment plants - experts speak of so-called trace or micropollutants.
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:
So far, the cleaning processes that take place in a sewage treatment plant, are not designed to eliminate such substances. Although some are at least decimated. But in the end, a large part ends up in the rivers and lakes into which the purified water is introduced. Thus, the substances get into the organism of living things and thus into the food chain of humans. Or they get into groundwater, from which drinking water is extracted.
Even the consequences for the ecosystems are unpleasant: So fishes fish by so-called endocrine disruptors, substances with a hormone-like effect. And probably also by traces of the hormone estrogen from birth control pills, which is excreted in the urine. Researchers had already found in a study years ago that in Austria two-thirds of all fish in the running waters were female.
In a study from Sweden, the behavior of perch had been changed, which were exposed to psychotropic drug residues. The animals were more active and daring - and thus easier prey. Not all effects that cause trace substances have long been known. Nevertheless, many experts believe that it would be better if at least some of them did not get into the environment or into the food chain.
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 and in 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 rot 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
In fact, this requirement could be fulfilled much better than it has been up to now. With a new technology, trace substances could be contained, another station for sewage cleaning has been available for several years. But so far only a few sewage treatment plants have decided to build the so-called fourth purification stage.
Sewage specialist Christian Hiller can only partially understand this. The engineer from Baden-Württemberg has been working with the new process on the Steinhäule sewage treatment plant in Ulm for several years - it is located just a few kilometers from the historic city center on the Danube.
Hiller points to a huge auger pump that carries jet-black water to some basins. Ironically, here at the first station of the new plant, the dark broth looks even dirtier than before. But in the end, the cleanest sewage of the Republic will flow into the Danube.
"Ulmer procedure" inspires experts
"We work with activated carbon," Hiller explains the black water. The process was initially developed in the sewage treatment plant over many years on a small experimental scale. Since 2015, the fourth cleaning stage has been in operation.
Not only the trade association DWA (German Association for Water, Wastewater and Waste) speaks of a flagship facility. The "Ulmer procedure" has become the established concept. Hiller has already explained the principle to experts from China or Japan, soon a group from India, he says.
Basically, it is quite simple: The water is added after the third purification stage powdered activated carbon. In some large basins, the contact reactors, then the decisive step happens. The activated carbon with its porous and brittle structure has a huge inner surface. "Physically speaking, a teaspoon of activated carbon powder has as much of a surface as a football field," says Hiller.
On this surface, the trace substances have plenty of space to accumulate. If the activated carbon has absorbed it in the contact reactor, it is necessary to separate the black powder from the water again. This happens in the next step in the sedimentation basin, where the coal sinks to the bottom. In a further step, the water is sent through a filtration system of quartz sand. Here, a so-called precipitant increases the yield, which makes again mechanically herausfiltrierbare particles from dissolved in liquid components.
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 usually 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.
The activated carbon is then returned to the sewage sludge for biological purification. In the end, this is dried and burned - this happens on most sewage treatment plants anyway. In the meantime, the heat gained is used as an energy source. Coal can even increase electricity production. However, more climate-damaging CO2 will be emitted.
"Before the water is channeled into the Danube, its activated carbon content is close to the detection limit," says Hiller. Even more important: According to measurements, the process removes a total of 80 percent of the drug residues and also some X-ray contrast media from the wastewater - previously it was only 30 percent of the detected trace substances.
Alternative ozone
The hormonal effects on fish stocks also decreased significantly. The feminization of rainbow trout that floated in Ulm waste water could be stopped according to tests, says Hiller.
The procedure of the Ulmer sounds perfect. Nevertheless, only a few of the 10,000 or so German sewage treatment plants have a fourth purification stage, and some are in the planning stage. Most plants also use activated carbon, but there are also more energy-intensive processes that use ozone.
This works similar to the bath water treatment. The ozone used to fumigate the wastewater destroys the trace substance compounds. However, new harmful substances can arise.
Zweckverband sewage treatment plant Steinhäule
Reduction of drug residues before and after the fourth purification step (blue)
Most of the modern plants with fourth clarification stage are located in Baden-Württemberg, for example in Sindelfingen, Karlsruhe or Mannheim. Together with North Rhine-Westphalia, where, for example, Aachen has opted for an ozonation plant, the state is at the forefront of technology. But: the opposite is still the vast majority of operators. They are skeptical and do not want to expand their investments.
One of the arguments: the cost. Ulm invested more than 40 million euros in their procedures. One part could be covered by subsidies. But in the end, the consumer will have to be asked to pay. About five euros more per year pays each connected to the system residents for clean wastewater. After all, a manageable amount.
But sewage is not the same as sewage, in the sewage treatment plants more and more is coming from industry and households. Each system therefore works a little differently and must also be able to react flexibly. With lower feed quality, the cost for consumers could be somewhat higher in some places. According to studies, a maximum of 16 euros per inhabitant per year.
At the same time, the process could at least save money here and there. Ulm had to pay close to one million euros a year earlier because they exceeded a reading when they first entered the Danube.
Wastewater treatment plants are obliged to pay attention mainly to three parameters: the so-called chemical oxygen demand (COD), nitrogen compounds (N total) and phosphorus compounds (P total). These are all nutrients that promote algae growth in the water. In the worst case, bodies of water will tip over and experts talk about eutrophication.
In Ulm, the COD was above the limit - a value that indicates how heavily the water is contaminated with organic compounds - including non-biodegradable. This was also the occasion to experiment with the new activated carbon process. Since it runs, the million is saved.
Skeptical operators argue that water conservation can not be the sole task of sewage treatment plants. Therefore, an approach at the end of the chain - experts speak of an end-of-pipe solution - does not make sense. For all polluters, the households, agriculture and industry, must be applied equally to reduce the input of trace substances. Finally, a lot of antibiotic residues also got into the water through livestock farming.
The Federal Environmental Agency (UBA) does not believe that only one measure alone solves the problem. Nevertheless, the experts have been recommending the construction of the fourth cleaning stage for at least some of the 240 largest plants that clean a total of 50 percent of German wastewater. Or in areas where it is entering sensitive water areas - for example, near drinking water catchment areas.
At the UBA one speaks in connection with the technology of an indispensable measure. "In the end, even the skeptics will have to admit that this is currently the most effective measure," says Frank Brauer from UBA.
Switzerland, too, relies on new technology
The individual federal states are responsible for sewage disposal and treatment in Germany. There is no obligation to expand the wastewater treatment plants even in the pioneer federal states. The Water Resources Act stipulates that wastewater pollutants must be reduced as much as the "state of the art" makes it possible.
In order to include the longest existing technology in the regulations and to achieve a uniform regulation, the Federal Ministry for the Environment (BMU) would have to change the waste water ordinance or the waste water tax law. But so far one does not follow the UBA recommendations there. "Legislative initiatives of the federal government to reduce the entry of trace substances are currently not intended," said the BMU on request of SPIEGEL.
Switzerland is already one step ahead. There is the new technology decided thing. It will be installed on one hundred of the 700 wastewater treatment plants over the next few years and funded through a nationwide sewage tax.
The hesitant attitude of the German legislator regarding a paradigm shift in wastewater management leaves many wastewater treatment plant operators at a loss. If they volunteer to do more than the legislature suggests, they may become legally vulnerable to a fee increase. Moreover, it is unclear to which trace substances and with which values you should interpret your plant extension at all? All this makes decisions more difficult.
Innovations are considered rather skeptical
After all, so that these important questions may eventually be answered and guidance exists, the BMU has set up a working group, the results of which one wants to wait. This process, which will be completed in the spring of 2019, involves stakeholders from industry and agriculture in addition to water boards. The BMU hopes for voluntary insight that it does not currently apply to regulatory measures. That it comes to an agreement in the end, which serves wholly the water protection, may therefore be doubted.
Until then, it depends on the operators, whether they themselves become active, as was the case in Ulm. If one looks around in the industry, one notices that some of them are rather skeptical about innovations and new technology. In the trade association DWA, in which the major operators set the tone, it is officially skeptical when assessing the technology. But internally, there are more and more followers of the process, it is heard.
Since the 1990s, when fighting against eutrophication in German rivers and lakes, not much new has happened on German sewage treatment plants. To be sure, more attention is currently being paid to energy optimization and the recovery of the valuable raw material phosphorus. But a part of the industry believes: It urgently needs an application and further development of the technology .
In Ulm, meanwhile, research is continuing on new systems on small plants. Currently, both ozone and tiny spaghetti membrane filters are being tested. At some point, this would make it easier to remove problematic microplastics - another challenge for the systems, as well as multidrug-resistant germs.
Even the current technology of the new cleaning stage reaches its limits here. Even if there are signs that slight reductions in germs and microplastics are achieved. If the new procedures will eventually work on a large scale, Hiller would probably have to spend more time with guides from all over the world.
Video: Battle over the water
MIRROR TV
