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Trace substance elimination & microplastic removal

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Trace substance elimination

What is that?



The ARA Weißenburg in detail



How do you remove that?

Trace substance elimination

Various methods are available for the elimination of organic pollutants, micro-pollutants, drug residues and anthropogenic trace substances. These can be divided into four groups: "Oxidative" with ozone or AOP, "Adsorptive" with PAH in the activation, before a flake filter or as a PAH stage consisting of a contact reactor, sedimentation after secondary clarification with internal recycling of the coal, "Adsorptive" with GAK in our DynaSand carbon filter and "Physical", where the DynaSand protects the downstream technology. 

AichTwoOh 💦 WasserScout | Stephan Jakobs | wegweiser spurenstoffe - Spurenstoffelimination & Mikroplastikentfernung

The German Association for Water Management, Wastewater and Waste e. V. (DWA) publishes a new leaflet series DWA-M 285 "Trace substance elimination in municipal sewage treatment plants". As part of research projects and the implementation of pilot plants in operation, numerous cleaning systems for the elimination of trace substances have now been implemented in Germany. In the meantime, processes with ozone and/or activated carbon are already being operated at more than 20 sewage treatment plants in German-speaking countries, so that in the meantime there is experience with the planning, construction and operation of some processes. Ozonation and activated carbon adsorption are currently considered to be suitable processes for the elimination of trace substances in municipal sewage treatment plants. According to the current status, taking into account the results of the stakeholder dialogue of the Federal Environment Ministry on the "Federal Strategy for Trace Substances", it can be assumed that in the coming years further sewage treatment plants will have to be expanded to include processes for the targeted elimination of trace substances. Until now, the processes have been dimensioned on the basis of characteristic values derived from semi-industrial and large-scale tests. At present, there is no document in the DWA set of rules for the interpretation of these procedures or a decision-making aid when selecting the procedure. With the creation of the new leaflet series, these gaps should be closed. The first three parts of the series are: Part 1: Criteria for process selection with selected examples Part 2: Use of activated carbon - process principles and dimensioning Part 3: Ozonation - process principles and dimensioning.

Project Weißenburg / Bavaria | Elimination of anthropogenic trace substances in municipal sewage treatment plants (pilot project 4th cleaning stage in Weißenburg)

AichTwoOh 💦 WasserScout | Stephan Jakobs | weissenburg - Spurenstoffelimination & Mikroplastikentfernung


The treated wastewater from conventional municipal sewage treatment plants contains a residual load of organic compounds of artificial origin. Such "anthropogenic trace substances" can then be detected in very low concentrations in water bodies. They come, for example, from the use of household and industrial chemicals, detergents and cleaning agents, or the use of pharmaceuticals and pesticides. Because of their stability, they are only partially broken down in sewage treatment plants. Some of these substances can affect aquatic organisms or drinking water production. This gave rise to the consideration of retrofitting, for precautionary reasons, especially larger sewage treatment plants with water-sensitive discharge conditions with a 4th cleaning stage to eliminate trace substances.

short description

The city of Weißenburg in Bavaria has set up a 4th cleaning stage on its sewage treatment plant. A two-stage process combination of ozonation and filtration was implemented. The Free State of Bavaria funded the pilot project with 75 percent of the eligible costs. The Weissenburg sewage treatment plant discharges into the low-flow Swabian Rezat. Due to this sensitive water management situation, the sewage treatment plant was selected as the location for a Bavarian pilot project. The following goals were pursued:

  • Gaining knowledge about the operation, performance and costs of a 4th cleaning stage
  • Improving the water quality of the Swabian Rezat
  • Elimination rate of 80% for selected indicator substances
  • Success control through extensive monitoring (before and after comparison)
  • Positioning as an environmental and technology location
  • Passing on gained experience to other operators and planners
AichTwoOh 💦 WasserScout | Stephan Jakobs | ara weissenburg 1024x768 - Spurenstoffelimination & Mikroplastikentfernung

From the start of planning until about a year after commissioning, the construction of the 4th cleaning stage was accompanied scientifically and technically as part of the project "Elimination of anthropogenic trace substances in municipal sewage treatment plants". Furthermore, an extensive measurement program was carried out. After a project period of around five years, commissioning was completed in spring 2019 and the knowledge gained was summarized in a final report.

In order to gain further insights into regular operation and to further optimize the energy use of the 4th cleaning stage, the follow-up project "4. Cleaning stage at the Weißenburg sewage treatment plant, experiences in normal operation”.

With the project for the sewage treatment plant in Weißenburg, an extensively examined "best practice" example is now available, which provides valuable knowledge for the conception and planning as well as for the operation of further plants for the elimination of trace substances.

project participants

  • City of Weißenburg i. bay (Construction and operation of the 4th cleaning stage)
  • Bavarian State Ministry for the Environment and Consumer Protection (project initiator, control)
  • Water Management Office Ansbach (state funding)
  • Engineering office Dr. Resch + Partner (planning)
  • University of the Federal Armed Forces Munich, Dr.-Ing. Steinle Ingenieurgesellschaft (scientific monitoring of the project "Elimination of anthropogenic trace substances in municipal sewage treatment plants")
  • Technical University of Munich, Weber-Ingenieure GmbH, engineering office Dr. Resch + Partner (scientific monitoring of the project "4th purification stage at the Weißenburg sewage treatment plant, experiences in regular operation")
  • Bavarian State Office for the Environment (coordination, accompanying investigation program, analytics)

Further information and results

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AichTwoOh 💦 WasserScout | Stephan Jakobs | Bayerisches Landesamt fuer Umwelt e1670171361621 - Spurenstoffelimination & Mikroplastikentfernung

Removal of microplastics

AichTwoOh 💦 WasserScout | Mikroplastik
  • When does plastic become microplastic? As soon as plastic particles with a size of less than 5 mm get into the environment (air - soil - water), a distinction is no longer made between 200 individual types or products of plastic. The large number of different polymers, including associated additives (e.g. plasticizers, PFAS) or other (poisonous) substances (e.g. heavy metals, pesticides, pharmaceuticals) are included under the term microplastics. However, microplastics only describe a fraction of the (synthetic) polymers found anthropogenically, namely solid particles. However, viscous polymers and soluble polymers must also be considered with regard to their environmental and health relevance.
  • What size is microplastic? Is there a definition? As of today, there is no uniform, internationally recognized definition of microplastics. For some years now, plastic particles and fibers have generally been referred to as microplastics if they are smaller than 5 mm and larger than 1 µm (smaller than 1 µm is referred to as nanoplastic). Sometimes a further subdivision into large (1 - 5 mm) and small microplastics (<1 mm) is made. From about 1 mm, the particles are usually no longer visible to the naked eye, especially from a size of less than 0.3 mm.
  • How much microplastic do we eat and drink? There are numerous reports about where microplastics have already been found everywhere. A large number of studies have been carried out in recent years in which microplastics have been detected in food. A common claim is that we eat, drink and breathe 5mg of microplastics every week - the weight of a credit card. Since microplastic research has so far mainly focused on the aquatic environment, most studies on food contamination can be found in fish and seafood. The microplastic accumulates mainly in the digestive tract. Therefore, the contamination of fish and seafood that is consumed with the digestive tract, such as mussels or smaller fish such as anchovies or sardines, is considered to be particularly problematic. The highest levels of microplastic contamination are found here in "filter feeders" such as mussels, which filter plankton from the water for food intake. To do this, they filter large amounts of water and cannot select between plankton and microplastics. Microplastics have also been found in other foods such as sea salt, honey, sugar, beer and mineral water. Note: These studies are based on different detection methods, the results vary greatly. In addition, most studies are always random samples, so it remains unknown whether the amounts are constant or whether there are fluctuations due to water treatment, machinery, processes, etc. or due to the analysis methods.

There is a lot of plastic waste in the environment and in our waters: beverage bottles, plastic bags, packaging, straws and much more. Less recognizable with the naked eye, but not rarer, is so-called microplastic. This page provides information on what exactly microplastic is and what quantities occur in Swiss waters.


Plastic, also known as plastic, is a persistent organic material or POP (persistent organic pollutant). It will be through the polymerization from monomers manufactured, which are generated based on petroleum, coal, natural gas. Typical types of plastic are

  • PET (polyethylene terephthalate) e.g. B. for light bottles
  • PP (polypropylene) e.g. B. for hard food containers or plastic furniture
  • PE (polyethylene) e.g. B. for flexible packaging films
  • PVC (polyvinyl chloride) e.g. B. for buildings, electronics applications
  • PS (polystyrene) e.g. B. for plastic cutlery, coffee mugs

In addition, there are essentially two types of bioplastics.

  • "Bio-based" or "from renewable resources" that are produced from renewable raw materials (plants) but are not necessarily biodegradable.
  • «Biodegradable» or «compostable», which are completely broken down into water, carbon dioxide and biomass, but are not necessarily made from renewable raw materials, but from petroleum, for example.

Plastic usually contains additional chemicals such as bisphenol A or plasticizers to give the plastic special properties. 

In science, plastic particles are usually classified according to their size and origin.


Macroplastics: Plastic particles larger than 200 millimeters
Mesoplasty: plastic particles between 5 and 200 millimeters
Microplastics: plastic particles between 5 and 0.0001 millimeters (=100 nanometers)
Nanoplastic: Plastic particles smaller than 100 nanometers


Primary microplastics: Microplastic particles that are industrially produced in this size for a specific application, for example

  • Pellets as the basic material for plastic production
  • Granules for cosmetic products such as peeling, shampoo, shower gel
  • fibers for clothing
  • Drug carriers in medicine
  • Plastic substitute for sandblasting for machine cleaning

Secondary microplastics: Microplastic particles that are only formed through the decay or decomposition of larger plastic parts, for example

  • due to friction and solar radiation in the water bodies
  • by washing synthetic textiles
  • through the abrasion of car tires. Strictly speaking, this is micro-rubber. However, it is often counted as a microplastic.

There are large amounts of microplastics in street water. It comes from the abrasion of car and truck tires, from polymers and bitumen from the asphalt, from shoe soles and road markings. Especially when it rains heavily, the plastic particles are often washed off the road not only into the sewage system, but also onto fields and bodies of water. On roads with little traffic, there is also the fact that the street sewage does not always go through the sewage system into a Road sewage treatment plant SABA, but is fed unfiltered into the next body of water or seeps into the subsoil.

Empa researchers have taken a closer look at the abrasion of tires - the micro-rubber. They calculated that between 1988 and 2018 around 200,000 tons of micro-rubber could have accumulated in the environment in Switzerland. According to these calculations, about three quarters remain in a five meter wide strip on the right and left of the road, 5 percent end up in the soil on the other side of the strip and 20 percent in the water
(Source: "rubber in the environment», Empa, 2019).

In a study by the Fraunhofer Institute UMSICHT, the researchers identified tire abrasion as the biggest cause of microplastics in the environment in Germany. Abrasion from asphalt is third, shoe soles seventh and road markings ninth.
(Source: "Plastics in the environment: micro- and macroplastics», Fraunhofer Institute UMSICHT, 2018).

350 million tons of plastic are produced worldwide every year. This corresponds to an average of 50 kilograms of plastic per person per year. About half of this gets into the environment via various processes, i.e. around 20 to 30 kilograms per person and year. The main sources of microplastics - around 1 kilogram per person and year - are

  • road traffic, especially the abrasion of car tires, brakes and road markings
  • Industry sources, e.g. B. Sandblasting with microplastics as a sand substitute
  • Plastic particles from cosmetics
  • washing synthetic fabrics
  • building colors, e.g. B. for building facades
  • artificial grass
  • Improper waste disposal, throwing away plastic packaging, bottles, cigarette butts, etc.

Viewed worldwide, primary microplastics hardly contribute to the pollution of the environment with plastic. More than 99.95 percent of the microplastics in the environment are secondary microplastics, i.e. the smallest plastic particles that only arise through the decay or decomposition of larger plastic parts.

On behalf of the Federal Office for the Environment (FOEN), Empa used calculations to estimate how much plastic gets into the environment in Switzerland. The seven most commonly used plastics were recorded: polyethylene (LD-PE and HD-PE), polypropylene, polystyrene and expanded polystyrene, PVC and PET. It is estimated that around 5100 tons of plastic are released every year: 4500 tons of macroplastics and 615 tons of microplastics. Of this, around 600 tons of microplastics end up in the soil and almost 15 tons in the water. (Source: "More than 5000 tons of plastic released into the environment annually», Empa, 2019)

In the EU, only around 7 percent of the microplastics released flow into ARA wastewater treatment plants via domestic and commercial wastewater. There, between 80 and over 99 percent is removed and disposed of with the sewage sludge. There are still 1 to 5 micrograms of microplastics per liter in the treated wastewater.

In the Canton of Zurich, the Office for Waste, Water, Energy and Air (AWEL) examined 28 ARA wastewater treatment plants. They release about 18 billion microplastic particles, or 330g, into the environment every day. Extrapolated to all 64 Zurich WWTPs, this results in a quantity of 31 billion particles or 600 g entering Zurich's waters every day. No microplastics could be detected in groundwater or drinking water. (Source: Specialist article «Microplastics in waste water and bodies of water», Aqua&Gas No 7/8, 2016)

The main source of microplastics in the environment is discarded plastic waste. In order to protect surface water and the environment from microplastic pollution, it is particularly important to reduce plastic and microplastics at the source and to properly dispose of the remaining plastic waste.

Important measures

  • Dispose of plastic waste properly. See the information from the Federal Office for the Environment FOEN «plastics»
  • Do without superfluous disposable products such as plastic bottles, cups, plates and cutlery, drinking straws and plastic bags
  • Reduce plastic packaging
  • When it comes to clothing, make sure that it is of good quality and use clothing items for as long as possible
  • Replace microplastics with natural substances in cosmetic products
  • Install more efficient fiber retention filters in washing machines
  • Prevent the release of microplastics in industrial processes as far as possible.

If one counts microrubber among microplastics, tire abrasion becomes the main source of microplastics. (Source: "rubber in the environment», Empa, 2019)

In Switzerland, an average of 100 to 2,000 cubic meters of wastewater per person per year enter the ARA wastewater treatment plants. There, between 80 and 99 percent of the microplastics are removed from the wastewater. With additional sand and membrane filters, processes that are already well established in Central Europe, the rate can be increased to over 99 percent. The microplastics removed from the wastewater collect in the sewage sludge, which is usually incinerated in Switzerland. According to model calculations, only about 0.01 percent of the plastic entering the environment in Switzerland comes from the ARAs. 

However, in countries that do not yet have a functioning wastewater treatment system, WWTPs are a good starting point for using cleaning technologies to remove microplastics from wastewater.

Photos of dead seabirds and fish with a belly full of plastic are well known. The dangers of large pieces of plastic in the environment are obvious. When plastic parts are mistaken for food and eaten by animals, they enter the digestive tract and can lead to abrasions, ulcers and constipation, and eventually starvation and death.

But small plastic particles in Swiss lakes and rivers may also pose a risk to aquatic organisms. Little is known about this. However, it can be assumed that the effect of microplastics is very similar in smaller animals, which mistake microplastics for food. In larger animals such as fish, microplastics have already been detected in the stomach and intestines and also in the liver.

In addition to the microplastic itself, toxic ingredients such as plasticizers or chemicals that have been absorbed by the plastic particles can also cause damage. Little is known about the effects of these additives, especially when they occur in combination. Like other surfaces in water, the particles are also overgrown by microorganisms such as bacteria. A so-called biofilm forms. There are first indications that harmful microorganisms can be concentrated on plastics.

Unlike humans or aquatic animals, aquatic life is more exposed to polluted water. They spend 24 hours a day in the water. In addition, they absorb the pollutants not only when they eat, but also when they breathe through gills and the surface of their bodies.

Microplastics can basically cause three potential problems in humans:

  • Physical damage in the human body from the particles themselves
  • Chemical damage caused by additives such as plasticizers, hormone-active and carcinogenic substances
  • Damage caused by microorganisms adhering to the particles

There are currently hardly any studies on this in Switzerland. According to the World Health Organization WSHO, the physical risk is low because microplastics larger than 0.15 mm are unlikely to be absorbed by the human body. It can hardly pass through the intestinal mucosa and is excreted quite quickly. Smaller particles are likely to be picked up only to a limited extent. However, very small microplastic particles and nanoplastic particles are likely to be absorbed by the human body. However, the data is extremely limited.
(Source: WHO)

The WHO also classifies the risk from chemical additives or microorganisms as very low, since the amount of substances absorbed into the body is very small. The risk of microorganisms in the water pipes or contamination when the drinking water is filled is much greater. Starting with the latter is therefore much more effective. 
(Source: WHO)

Trace substance elimination and microplastic removal: challenges and advances

The increasing pollution of the environment by trace substances and microplastics poses a significant threat to ecosystems and human health. Trace substances include a wide range of chemical compounds, including pharmaceutical residues, pesticides, industrial chemicals and endocrine disruptors. Microplastics, small plastic particles less than 5 millimeters in size, are created by crushing large pieces of plastic or are used directly as microbeads in cosmetics. In this paper, the challenges and advances related to trace substance elimination and microplastic removal are discussed.

Challenges in the elimination of trace substances:
Removing trace elements from water is a complex task because many of these compounds are chemically stable and traditional water purification technologies cannot effectively remove them. In addition, trace substances are often present in very low concentrations, which makes their identification and removal difficult. The continuous release of new trace substances and the increasing number of chemicals pose an additional challenge. Innovative approaches and technologies are therefore required to achieve efficient trace substance elimination.

Advances in trace substance elimination:
Various advances in the elimination of trace substances have been made in recent years. Advanced oxidation processes such as ozonation and activated carbon filtration can enable effective removal of certain trace substances. The use of membrane filtration technologies such as reverse osmosis and nanofiltration has also been shown to be effective. In addition, new technologies such as the advanced oxidation reaction with UV or visible light, the use of ionic liquids and electrochemical oxidation are being explored. These approaches are showing promising results, but further research is needed to assess their efficiency, economics and environmental impact.

Challenges in microplastic removal:
The removal of microplastics from water bodies and other environments is a complex task as they come in different shapes and sizes and reside in different environmental matrices. Microplastic particles are often light and can be transported over long distances by wind and currents. In addition, existing methods for detecting and quantifying microplastics are still limited, making pollution monitoring and assessment difficult.

Advances in microplastic removal:
Various approaches to microplastic removal have been developed

developed, including physical methods such as sieving, sedimentation and filtration. More advanced technologies such as the use of nanomaterials, adsorption and electrostatic charging are showing promising results. In addition, biological approaches are being researched in which microorganisms are used to break down microplastics. However, many of these technologies are still in the development and testing phase, and their practical applicability and environmental compatibility need to be further investigated.

Trace substance elimination and microplastic removal are complex challenges that require a holistic approach. Advances in water purification technology and the development of new methods show promise to reduce the environmental and health impacts of micropollutants and microplastics. It is important that governments, industry and research institutions work together to develop and implement effective solutions to protect our water bodies and ecosystems from these harmful contaminants.