Press Release

The enormous demand for brown cardboard and paperboard driven by the increase in sales figures in online trade requires especially coordinated methods and equipment for wastewater treatment. The raw material used to produce brown cardboard and paperboard is the highest possible percentage of recycled waste paper. The fibers recovered during the recycling process attribute to a high input of limescale, fillers and binding agents. Large quantities of organic compounds are discharged with the wastewater from production. A major portion of these organic compounds are already degraded in an anaerobic (without oxygen) process step. Nonetheless, yet another aerobic process step is needed to lower the pollutant loads in the wastewater to a level that allows the treated wastewater to be discharged back into the receiving waters and thus into the environment.

Challenges of aerobic treatment

In the aerobic process step, oxygen is transferred to the bacteria by an aeration system, reliably degrading the organic pollutant load. The challenge to overcome in the aerobic step is not only to realize an energy efficient oxygen transfer, but also how to deal with the difficult boundary conditions that arise in the wastewater of a paper mill in particular.

• As soon as calcareous (“hard”) water is exposed to ambient air, what occurs is a shift in the lime / carbonic acid equilibrium. Extensive lime deposits and sedimentation of lime particles occur in the entire basin (walls, pipelines, etc.). The sediments are loose and, due to their high density, are deposited on the basin floor if they cannot be sufficiently stirred up by a mixing device.
• The sediment lime is deposited in the sludge flakes, and as such, in addition to the oxygen injection, the agitation rate must also be sufficiently high in order to distribute this heavy sludge homogeneously throughout the basin, optimally run the aerobic process and prevent deposits.
• Boundary conditions such as high temperatures, large injection depths and lime sediments cause damage, bringing about an interruption in the oxygen supply in many aeration systems. The particles can cause the aerators to close up and be clogged (major increase in the pressure loss) and reduce transfer performance. Ultimately, the aerobic process step is no longer able to achieve the planned degradation performance, causing the effluent values of the wastewater treatment plant to exceed the approved target values. This impacts the maximum possible production capacity.

The HYPERCLASSIC^®-Mixing and Aeration System – the energy-efficient, reliable and low-maintenance solution

The HYPERCLASSIC^®-Mixing and Aeration System is a mechanical aeration system, which has been in use in industrial wastewater treatment plants for over 20 years. With a unique combination of mixing and aeration system, INVENT provides the solution for the demanding tasks of aerobic wastewater treatment. Especially in the wastewater resulting from paper production, because of the specific characteristics of the components, all of the problems in the aerobic process step are successfully avoided:

• Oxygen is transferred through a ring sparger, which is installed leak-tight above the basin floor. This design ensures a high injection depth and long dwell time of the air bubbles. In addition, the large injection openings ensure many years of aeration operation with no blockages, loss of pressure or efficiency.
• The high injection efficiency or rather the ability to generate fine air bubbles is the result of stainless steel ribs on the bottom of the mixer-body. During aeration operation, the mixer-body rotates continuously, producing very fine bubbles in the trail of the stainless steel ribs. They are transferred and distributed laterally, radially into the basin with the mixer flow.

The HYPERCLASSIC^®-Mixing and Aeration System also exhibits its high degree of flexibility when integrated into a wastewater treatment plant.

• All that is needed to operate each unit is an air and power connection. Each unit can feed an entire basin with up to 2,000 Nm³/h air.
• The HYPERCLASSIC^®-Mixing and Aeration System can be delivered in a stainless steel cage, thus making it easy to lift when needed without having to empty the aeration tank. Because of its own weight, it is safely positioned at the installation site.

These unique characteristics have made the HYPERCLASSIC^®-Mixing and Aeration System the industry standard in the field of aerobic treatment of paper wastewater over the recent decades. No matter whether the largest paper machine in Europe, the most state-of-the-art production plant in Europe or specialist manufacturers, each of them rely on the efficient, reliable and low-maintenance system from INVENT.

In 2020, a total of twelve HYPERCLASSIC^®-Mixing and Aeration System were installed in the Palm GmbH & Co.KG paper mill in Aalen, Germany. Each system distributes up to 1,800 Nm³/h at an injection depth of up to 11.5 m. The overall specification and the selection of materials meet the highest standard for use in the wastewater of a paper factory.

For awhile, the term microplastics has been one the public has become familiar with and has focused on more frequently. Even though the breadth of the problem may be hard to grasp, studies have shown that microplastics represents a danger to humankind and the environment. State-of-the-art wastewater treatment plants equipped with the relevant filter technology are already able to filter out microplastics from the wastewater, thereby drastically reducing the release into the environment. The research project “Removal of Microplastics from the Water Cycle (OEMP)” conducted by the German Federal Ministry of Education and Research employed the iFILT^®-Diamond Filter for two years in an effort to retain microplastics – and the results were impressive.

Based on the current definition, microplastic particles are smaller than 5 mm. They are broken down into two groups: primary microplastics, as a component found in numerous products such as cosmetics and care products as well as in cleaning products, and secondary microplastics, produced by physical, biological and chemical degradation processes from large plastic parts, e.g. granulated plastic bottles. Microplastics can be released into the environment either directly or indirectly. They can be released through water bodies and by land (wind, rain). Just like paper, fibers and particles from clothing and cosmetics, microplastics are flushed into all types of water through household drains, sewers and wastewater treatment plants. Our knowledge about the amounts released into the environment and the potential retention is as of yet still limited. The German Federal Ministry of Education and Research dedicated the research project “Removal of Microplastics from the Water Cycle (OEMP)” to precisely these questions.

As part of this research, the iFILT^®-Diamond Filter was tested in the removal of microplastics in the area of wastewater treatment plant discharge and mixed water overflow. The novel Diamond Filter is based on a revolutionary fluid mechanics general concept. The basic idea is to combine an optimized fluid mechanics design with the cross-flow filtration process engineering approach. This allows a high hydraulic performance to be achieved despite minimum space requirements, yet with an optimum of separation efficiency. The continuous rotation of the filter wheels, the effect of tangential-dynamic filtration that it initiates and the sharp separation limit of the stainless steel high performance weave mesh utilized provide for guaranteed high separation efficiency.

During the course of the research project, GKD-Gebr. Kufferath developed a novel stainless steel high performance weave mesh, which was then tested using the iFILT^®-Diamond Filter. The weave mesh that was developed feature extremely small opening widths of 6 and 8 µm. They are the absolute pore size that guarantee that no spherical particles any larger than the opening widths can make their way through the discharge of the filter. The filter media primarily used up until now have featured an absolute separation limit in the range of 15 μm. The slot-like pore geometry of the weave mesh ensures excellent retention of particles. The openings in the mesh are larger than on the mesh surface, ensuring good regenerability.

The tests of the wastewater treatment plant discharge were carried out at the wwtp Berlin-Ruhleben, Germany, with wastewater equivalent to up to 1.6 million inhabitants. The daily treatment performance was 247,500 m3, which increased to up to 600,000 m3 wastewater during rainy weather. The biological treatment method included an activated sludge process with denitrification and biological phosphorus elimination. In order to create valid comparison values, the Diamond Filter was first equipped with a standard 20 μm weave mesh. This step already reduced the dirt load of filterable substances (AFS) from 5 mg/l in the inflow to below 3 mg/l in the discharge.

After retrofitting to the new weave mesh with a separation limit of 6 μm, the discharge concentration was then further reduced from 3 to 2 mg/l. In addition to increasing the separation performance, due to the novel weave mesh and the revolutionary Diamond Filter concept, yet an even higher throughput capacity was achieved. With a filter wheel, throughput rates of 110m³/h could still be achieved when using the 6 μm mesh. In relation to the installed filter area, this equates to a specific hydraulic capacity of 22 m³/(m²xh), which is an absolute peak value in the field of gravity filtration.

The measurements for microplastics showed that the total plastic masses were subject to considerable fluctuations even within one day. It was not possible to determine any system in the values. While traces of plastic were found in the wastewater treatment plant discharge, they were hardly detectable in the discharge of the Diamond Filter. The tests confirmed that significant traces of plastic even in the lower μm range were removed from the water.

For the mixed water treatment tests, the Diamond Filter was set up in the mixed water overflow basin. The concentrations of filterable substances are significantly higher here as compared to the wastewater treatment plant discharge. Even for mixed water, the iFILT^®-Diamond Filter with the 6 μm weave mesh was able to achieve a separation performance of filterable substances in excess of 99%.

These results are extremely promising! The iFILT^®-Diamond Filter has been demonstrated to reduce the environmental pollution related to the release of microplastics into water. By expanding the wastewater treatment plants with the tertiary Diamond Filter and thereby almost completely removing microplastics, adverse consequences to the environment and humankind can be reduced.

INVENT Umwelt- und Verfahrenstechnik AG is celebrating its 25th anniversary this year. The company based in Erlangen, Germany offers its customers groundbreaking technology for the purification of water and wastewater and is on course for growth worldwide.

Erlangen, Germany.

Records show August 1, 1995 as the date that the company was established. However, the history of INVENT Umwelt- und Verfahrenstechnik GmbH & Co. KG as the company still went by at the time dates back about a decade further – as a project by scientists of the Department of Fluid Mechanics at the Friedrich-Alexander-University Erlangen-Nuremberg.

It started with the idea of developing sustainable, energy-efficient products for water purification and wastewater treatment viewed from an entirely different perspective, i.e. the fluid mechanics approach, and in doing so, setting new standards. With this idea, the experts revolving around Dr. Marcus Höfken – who at the start was the General Manager, and today is the CEO – took the step to venture into the economy, expanding with a clear purpose into the field of municipal and industrial water purification and wastewater treatment.

“Our huge commitment to manufacturing and utilizing high-performance products that contribute greatly to maintaining our water quality makes our company unique,” explains Dr. Marcus Höfken. He continues to explain that INVENT is the only company worldwide that offers a truly complete array of products – from agitators, mixing and aerating systems, membrane aeration systems, water filters, flow simulation systems to engineering services – for biological wastewater treatment and as such is able to offer its customers turnkey system solutions from a single source. Dr. Marcus Höfken proudly looks back at what has been achieved so far: “I am really pleased that we have managed to develop and build up a company that operates on an international scale on the basis of scientific research work, and that this company is today among the top 5 globally in its field”.

However, the engineers from the greater Nuremberg-Erlangen and surrounding area really had to struggle to gain acceptance for the new technology at the end of the 1990s: The reason: Wastewater treatment turned out to be a very conservative market, in which introducing new products is a difficult endeavor.

Four locations abroad

The first major project was realized early in the first year of establishment with the wastewater treatment plant for the Reudnitzer brewery in Leipzig. The contract included its design, engineering, production, delivery and installation. In the subsequent years, Invent equipped almost all of the wastewater plants in Switzerland with proprietary hypberboloid agitators, which were also installed in three large sewage treatment plants in Berlin.

After years of successful pioneering work, the limited liability company (GmbH) was converted into a stock corporation (AG) in 2003, allowing it to then expand further worldwide. As such, several subsidiaries were established one after another in the United States (2004), Australia (2009), Italy (2010) and subsequently in the United Arabic Emirates (2011). And in between (2008), the company moved into the newly erected company headquarters in the Eltersdorf district in Erlangen. In 2016, INVENT AG acquired Geppert Rührtechnik GmbH from Erzhausen, a community in Hessen. Today, INVENT AG is home to a staff of around 120 employees worldwide.

The international orientation of the company has long since paid off. In the meantime, numerous wastewater treatment plants overseas bear the made in Erlangen, Germany stamp. In addition to several contracts from New York and Washington plants, of particular importance was a major contract valuing $16 million, which comprised a Baltimore wastewater treatment plant and was ultimately completed in 2017, was particularly significant.

Given the COVID-19 pandemic, there are simply quite a few hurdles that have to be accepted at this time. In particular, the absence of trade shows, conventions and even the ability for technicians to travel to customers in risk areas pose real challenges. Nonetheless, the company’s capacities are currently being well utilized. At this time, the team from Erlangen is beginning its largest industrial project of its company’s history thus far, a complete wastewater treatment plant for several refineries in the Middle East. The sales volume for this is in the double-digit million range. In addition, Invent was awarded the contract for two additional major industrial projects in Thailand and one in China.

New products and ambitious growth targets

Given the growing environmental problems, the outlook for INVENT AG is quite promising. “Over the past few years, we developed numerous new projects, which we are now successively introducing to the market, which will give us a lot of fun things to do in the coming years and also generate more sales,” says Dr. Marcus Höfken optimistically.

In contrast, the Sales department and the organization as a whole is facing an increasing number of challenges. Plus, a new ERP system will be introduced next year.

Well equipped for new tasks, the CEO continues by formulating even more ambitious goals for the years to come. For example, the three of the youngest subsidiaries for high-speed turbo-blowers, for filtration and for industrial mixers are expected to contribute EUR 10 million each to Group sales in the near future.

Because of the COVID-19 situation, the company’s anniversary celebration was held in a smaller, company-internal setting on September 25, 2020.

INVENT developed the HYPERMIX^®-Agitator for efficient mixing in drinking water reservoirs.

Drinking water reservoirs play a central role in the implementation of safe access to drinking water in our cities and communities. The treatment and filtration processes to produce drinking water can be costly, and to ensure the final product to the consumers is of the highest standard, quality must be maintained within the storage facilities. Within the storage facilities the water can deteriorate through “stratification“ leading to undesirable odour and taste variations, as well as critical chemical concentration variations which can result on the delivered water being outside regulatory guidelines.

Stratification in drinking water reservoirs impacts water quality. During the stratification process, different water layers with different temperatures occur. There is no fluid exchange between these layers. This leads to longer dwell times for a part of the water and thus to algal formation, subsequent germination and/or uncontrolled chemical concentrations. All this can easily be prevented by the implementation of the HYPERMIX^®-Agitator. This mixing system helps to displace the water layers and to prevent them re-forming.

The construction and the design of the HYPERMIX^®-Agitator are based on the successful HYPERCLASSIC^®-Mixer that has now been adapted for the use in drinking water reservoirs. For this reason, all the essential parts as well as the mixer-body are made from stainless steel SS 316 as well as the drive that is situated below the water surface and are designed to meet hygienic design directives DIN EN 1672-2:2009-07.

The HYPERMIX^®-Agitator has been specifically engineered for quick and simple installation requiring no special tools or equipment. The agitator is lowered through any existing maintenance opening and rests under its own design weight on the tank floor. It is supplied with an external control system that is used for start stop and speed setting. The speed setting can be used for optimizing chemical dosing, allowing the HYPERMIX^®-Agitator to provide maximum fluid volume flow during the dosing process. This, in combination with the optional integrated dosing point within the high turbulent zone ensures complete micro mixing prior to distribution to the entire tank contents.

INVENT Umwelt- und Verfahrenstechnik AG is going to present two product novelties in the field of mixing at IFAT and confirms once again it’s position as the worldwide market leader in mixing systems.

The INVENT CYBERSLUDGE^®-Mixer is a mixing system that features a fluid mechanically optimized design and was designed for the mixing of the waste sludge in the digester. The design of the mixer relies on an explosion-proof drive train, which drives a solid stainless steel shaft with single or multiple INVENT CYBERSLUDGE^®-Mixing Elements. The mixing element was developed especially for the harsh environment in waste sludge with high solids concentration and viscosities. It features a fluid mechanically optimized 3-balded-design. The shape, inclination, camber, and the winglets are composed in such a way that a sufficient level of shear forces, a high pumping rating at low energy consumptions, and a jet-type flow pattern without the use of a draft tube could reliably be met. As a result, the INVENT CYBERSLUDGE^®-Mixer features a robust and performative design for mixing, circulation, and homogenization of the waste sludge in the digester.

The INVENT iBC-MIX^®-Tote Tank Mixer is designed for the continuous operation in steel caged IBC1, tote, or pallet tanks and liquids of different composition, viscosity, and rheology. It consists of an AC drive unit, a docking traverse, the shaft and an impeller of application depended design. The INVENT iBC-MIX^®-Tote Tank Mixer has a wide range of applications. It can be used, for instance, for the continuous mixing of chemicals, flocculants, coagulants or limestone. Other applications are the mixing of paint or the suspension of ingredients in the food and beverage industry. Put simply, the INVENT iBC-MIX^®-Tote Tank Mixer is an easy solution for container mixing.

The global reuse of water directly after it has been treated in a wastewater treatment plant is increasingly gaining in importance, be it for reasons of environmentalism or efficiency. This increases demands on the treatment of wastewater and requires additional treatment phases. A fundamental part of tertiary wastewater treatment is the added filtration. It is the basis for further steps of conditioning, such as a fourth treatment stage, separation of microplastics, retention of phosphorus, or disinfection.

INVENT Umwelt- und Verfahrenstechnik AG made use of their long-standing experience in the sector of water and wastewater treatment as well as their expertise in the fields of fluid mechanics, hydraulics and component design to develop the iFILT^®-Diamond Filter. It was constructed especially for the separation of solids from fluids as the next treatment phase after secondary sedimentation. It removes the smallest suspended solids that are still present in wastewater, for example activated sludge flakes, microplastics, precipitation flakes after phosphorus reduction or powdered activated carbon. It is extraordinarily energy- and resource-efficient and offers excellent separation performance using a minimum of space.

Industrial enterprises are also greatly interested in the energy-efficient and ecological use of their processing water. The iFILT^®-Diamond Filter can be applied in many areas, such as in the general reuse of processing water in the paper and textile industries, water treatment in fisheries or the treatment of flush water in the beverage industry.

Construction and mode of operation of the iFILT^®-Diamond Filter

The iFILT^®-Diamond Filter consists of one or more filter wheels, backwash unit, enclosure and tray. The filter discs are directly mechanically connected without the additional usage of a central pipe. They are equipped with high-quality, stainless steel, high-performance filter cloth with pore sizes varying between 10 and 100 µm.

The iFILT^®-Diamond Filter is charged directly into the rotor center via a fluid-mechanically optimized distributor, which eliminates the usage of a gasket in the feed area. This rules out any unnoticed leakages and filtrate contamination due to worn-out gaskets. Via the distributor wastewater runs through the filter wheels from the inside towards the outside. The increasing loads of solids on the filter material slowly leads to a rise of the hydraulic resistance, which eventually leads to a rise of the water level within the filter wheels. When a predetermined water level within the filter wheels has been reached a backwash of the filter cloth is triggered. The periodic backwash or removal of retained solids from the filter cloth is performed with the help of splash water, which is applied to the filter cloth from the outside. The splash water pump is charged with filtrate and thus does not require an external water supply. By way of rotor rotation and cleaning action of the spray nozzles the removed solids are flushed into an internal collecting flume and are drained off the machine separate to the filtrate. The solids are usually reintroduced to the wastewater treatment plant’s influent.

Enhanced hydraulic performance due to cross-flow-filtration

The iFILT^®-Diamond Filter uses a well-thought-out fluid-mechanical overall concept. Depending on the individual case this concept enhances hydraulic performance by up to 100 percent! This is achieved by using a holistic fluid-mechanical optimization approach that is based on the principle of cross-flow-filtration.

The continuous rotation of the disc, the very high rotational speed and the thus initiated effect of a tangential-dynamic filtration limit the built-up of a surface layer to a minimum and enable an optimal hydraulic discharge. A small number of rotating filter discs already achieve high throughputs. This means low spatial requirements: the iFILT^®-Diamond Filter can be put into operation even under restricted circumstances with regard to space.

Many advantages for the operating company

Apart from the hydraulic efficiency and the resulting high economic efficiency the iFILT^®-Diamond Filter offers additional advantages for the operator. The fact that no large-scale gasket neither in the rotor’s feed nor the discharge area is required makes the machine virtually maintenance-free. Leakage and therefore unnoticed deterioration of the filtrate’s quality will not happen. As the filter disc is in constant rotation the energy-intensive backwashing cycles are reduced to a minimum and the overall energy consumption of the filter is extremely low.

All components of the iFILT^®-Diamond Filter are made of high-quality stainless steel, therefore by far exceeding all requirements of modern wastewater treatment with regard to durability and longevity. The applied material meets the highest demands on robustness and mechanical stability even under the most adverse conditions. Additionally, being an INVENT complete solution, the diamond filter is particularly easy to install. During assembly it will be attached to the supply and drainage pipes and electrically connected – that’s it!

The iFILT^®-Diamond Filter is available in a container version or a concrete tank version, which makes it easy to adjust it to any given conditions.

Overview of the iFILT^®-Diamond Filter’s advantages

Conclusion on the iFILT^®-Diamond Filter

Up to now the processing steps of filtration or micro-sieving have been connected with high investment costs, a fact that has a deterring effect on many municipalities and industrial enterprises. However, public pressure to tackle this subject in order to protect the environment is mounting. The newly developed and fluid-mechanically optimized iFILT^®-Diamond Filter meets all demands on continuative treatment steps in communal and industrial water treatment. INVENT therefore makes sure that tertiary treatment steps can be realized in a more economic and large-scale way.

Wastewater coming from breweries is biologically and chemically heavily contaminated, the most important parameters being the biochemical oxygen requirement and sulfides that, when inadequately areated, can lead to olfactory problems (hydrogen sulfide). The federal government’s central wastewater processing agency stipulates strict maximum permissible values for the direct discharge of a brewery’s wastewater. Indirect discharge facilities are subject of different permissible values, varying partly depending on the specific communities. In any case, compliance with the permissible values is highly relevant for wastewater treatment plant operators in the vicinity of a brewery.

Many restrictions are to be observed with regard to treating a brewery’s wastewater. It has a high concentration of easily degradable organic compounds (BSB5), disinfectants are being used and the pH value is very fluctuant, as acidic and alkaline cleaning agents are alternated during the CIP (Cleaning In Place) processes. The occurring loads of harmful substances are diluted in the mixing and equalization tanks and leveled out with regard to the pH value. The water level in the compensating tanks fluctuates greatly and wastewater from a brewery tends to develop odors due to its high temperature (> 35 °C) and easily degradable components. Detergents (surfactants) from the CIP processes are often the reason for a reduced and insufficient oxygen transfer to the wastewater as a result of very low oxygen transfer factors (alpha values). These alpha values very much depend on the choice of aeration system that is applied. Additionally, wastewater from a brewery often contains diatomaceous earth, which is carried over from the filtration process and is very fine-grained and highly abrasive. It causes great wear and tear of the current mechanical equipment in the activated sludge tank, clogs pores of aeration membranes and causes abrasion of mechanical aerators.

The INVENT HYPERCLASSIC^®-Mixer is an optimal choice for use in mixing and equalization tanks due to its suspension and homogenization characteristics. Because of the installation of the mixer close to the bottom of the tank its operating performance is not influenced by fluctuating water levels. Sedimentary deposits, e.g. of diatomaceous earth, are reliably eliminated in the mixing and equalization tanks, so that odors cannot occur. The  HYPERCLASSIC^®-Mixer excels in energy-efficient operation as well as high operational safety. Due to its robust construction the amount of maintenance and operational costs are both low.

An optimal solution for the oxygen transfer to activation tanks of a brewery is the INVENT iCBA^®-Aeration System, a nonwearing stainless steel aerator. The arrangement and number of air outlet ports is optimized with the help of modern CFD (Computational Fluid Dynamics) methods. Detailed knowledge of fluid mechanical ratios in aerated tanks as well as targeted planning of the aerators’ arrangement allows for consistent aeration. This results in high oxygen transfer efficiency and energy-efficient and reliable operation.

When compared to other surface, submerged or membrane aerators, which struggle with corrosion and rotor damage as well as a too low oxygen transfer, the iCBA^®-Aeration System offers energy conservation of up to 30% and a significantly higher operational safety. It is possible to successively exchange current systems with the iCBA^®-Aeration System.

Abb.1: Activated sludge tank of TECATE Heineken wastewater treatment plant equipped with INVENT INVENT iCBA^®-Aeration Systems. On the left, in front, the now inoperative surface aerator (Source: Cuauhtémoc Heineken Mexico)
Abb. 2: INVENT iCBA^®aerator installed in activated sludge tank (Source: INVENT)