Project Report

Approximately 70% of the total energy demand of a water or wastewater treatment plant is consumed specifically for the mixing and aeration systems in the activated sludge process. In view of that it is becoming increasingly important to use systems that deal with resources in a responsible way.

HYPERCLASSIC^® -Mixer – the hyperboloid mixing technology

INVENT made significant contributions to the efficiency and effectiveness of such plants with the introducing of hyperboloid mixing technology in the early 1990s. Since this time, the hyperboloid mixing technology has been continuously developed. Many thousands of successfully operating installations world-wide impressively demonstrate that the HYPERCLASSIC^®-Mixer has become the industry standard in this field of application.

Example New York City

The tremendous potential for energy savings can be shown using the example of the large wastewater treatment plant Bowery Bay in New York City. At an equal purifying capacity the energy costs of the Hyperboloid-Mixers have shown to be as little as only a third as those of the replaced mixers. The slightly higher initial capital costs were compensated by reduced operational costs. In total, the savings mounted up to 3,500,000 US-Dollar over a period of 10 years. The New York experience demonstrates without doubt, that the selection of mixing equipment has a significant effect on the operating costs of large wastewater treatment plants.

Due to the achieved energy savings and high level of reliability of the INVENT equipment the City of New York also have converted Wards Island, Jamaica Bay, Coney Island, Rockaway Beach and Hunts Point plants to INVENT Mixers.

Product information

The HYPERCLASSIC^®-Mixer is the optimum mixer for all suspending and homogenization tasks required for water and wastewater treatment. The rotation of the hyperboloid-shaped mixer-body close to the bottom generates high-speed and turbulence at the bottom of the basin. This reliably prevents the settling of sludge particles. Eight transport ribs generate a three-dimensional main flow with a high circulation rate. This ensures excellent, uniform mixing. Because of the low speeds, the energy input is low in shear force. Sludge flocculation is thus subjected mechanically to minimal stress loads. Low speed at the water surface reliably prevents aerosol formation and oxygen transfer. The efficient design and the use of rugged materials minimize operating and maintenance costs.

One of our leading products ensures reliable mixing in the flocculation basins of a drinking water treatment plant in the Southeastern USA.

Drinking water treatment is one of the most important public tasks worldwide. Even where fresh water is available in sufficient quantities, the water must be clarified, filtered, and disinfected to make it safe for human consumption and for supplying to drinking water systems. There is also no shortage of available water in Georgetown County in the U.S. state of South Carolina, which lies directly on the Atlantic Ocean. A number of rivers together form an estuarine delta here, including expansive marshy areas.

The Georgetown County Water and Sewer District Public Water Utility has been operating since 1967. It is responsible for supplying more than 20,000 households and established industrial and commercial enterprises. Among other things, GCWSD operates a drinking water treatment plant, which recently required replacement of aging equipment. These updates included a replacement of their vertical inclined-blade flocculators, which had reached the end of their useful life.

In their search for a high-performance replacement that could solve the problems associated with the accumulation of solids in the flocculation basin, while still maintaining good floc formation, the managers found what they were looking for through our local representative, DXP|Premier Water of Charlotte, NC. They ultimately offered the INVENT HYPERCLASSIC^® Flocculation System, the world’s leading technical product for this application.

The HYPERCLASSIC^® Flocculation System utilizes a hyperboloid shape to effectively balance the amount of mixing energy required to prevent settling in the floc basins, while simultaneously minimizing floc shear. The hyperboloid shape allows for a gradual acceleration of the floc particles to gently transfer the mixing energy to the particles and prevent breakage.

After the first year of operation the plant staff inspected the new hyperboloid flocculators and found almost no settling or build-up in the flocculation basins, even when using lime for pH adjustment. This was a welcome change for maintenance staff from the previous equipment, which used to cause significant settling and sludge buildup.

INVENT is proud to be a part of improving local water treatment systems. Thank you to Georgetown County WSD, we appreciate their trust in our equipment.

Thanks to the mixing and aeration technology from Erlangen, Germany, a state-of-the-art wastewater treatment plant is now able to transform wastewater from a vacation resort into valuable hydration for an evergreen golf paradise.

There is plenty to discover in San Miguel de Allende, Mexico. Its fortified baroque downtown with featuring a number of striking church buildings has been a UNESCO World Heritage Site since 2008.

In the recent past, sophisticated weekend and vacation home developments have emerged around this gem. In keeping with the upscale construction quality, the builders of one of these resorts implemented an equally high-quality wastewater treatment plant fitted with technical equipment from INVENT.

The plant, which was built in 2017, is designed for a wastewater volume of 1,080 cubic meters per day and operates based on SBR treatment technology. A “Sequencing Batch Reactor” requires the construction of basins for pre-treatment, for the periodically repeated multi-phase sewage sludge treatment (filling, aeration, mixing, emptying) and for the clear water that in the end is the result of the process.

This is where the INVENT technology comes in with three rectangular tanks. In the SBR tank (dimensions length 22 m x width 10 m x depth 5 m), two HYPERCLASSIC^®-Mixing and Aeration Systems, each with a diameter of 2.5 m, along with an aeration system, ensure uniform mixing of the content. In a final step, the extracted water is discharged from the SBR basin via an iDEC^®-Decanting System with a pipe diameter of 20 cm.

A INVENT HYPERCLASSIC^®-Mixer featuring a diameter of 2 m is utilized in the 12 m x 5 m x 5 m equalization basin, and an iCBA^®-Aeration System with 18 aerators is utilized in the sewage sludge basin of the same size, to prevent, among other things, foul odor emissions.

With the water extracted from the wastewater treatment plant, the operators of a neighboring golf course cover their needs for the green areas and the artificial lake in between.

Now in its fifth year, the INVENT technology is running efficiently and contributing almost silently, yet effectively, to the comfort and recreational value of the residential and recreational complex.

Since 2014, quality INVENT products have provided reliable aeration of highly sensitive waste water in a petroleum refinery south of Oslo.

If our systems could talk, they’d have a lot to say. They’d tell how reliably and uncomplainingly they have performed their duties day in and day out in all seasons of the year.

Just look at Norway! On the western shore of the Oslo fjord — more specifically in Slagentangen, near the town of Tønsberg, energy conglomerate ExxonMobil has operated a large refinery for North Sea petroleum since 1961. About 6 million tons of oil are processed here every year.

Naturally, an operation like this has its own sewage treatment plant. In 2014, the operators had an outstanding idea — for purifying waste water, they ordered a TEX-FLEX^®-Aeration System consisting of 15 liftable modules, each with 12 aeration elements.

A liftable TEX-FLEX^®-Module consists of a TEX-FLEX^® aeration grid, complete with bracket and steel beam. The grid is made of pre-assembled rust-free premium stainless steel tubes, whose openings are equipped with fine-meshed membranes of insensitive textile fibers. Robust hoses feed the air in.

The 15 modules were installed in a ring-shaped waste water tank with an external diameter of 22.5 m and an internal diameter of 12.5 m. The tank’s capacity is about 1,575 cubic meters. The aeration is needed for chemical processes that treat organic compounds in the waste water, which arise from oil processing.

For almost eight years, the operators have been satisfied with their maintenance-free INVENT aeration system, and so are we!

Our HYPERCLASSIC^®-Mixing and Aeration System Float, the world’s first floating mixing and aeration system, showed impressive results in the test application.

Pond treatment plants offer the capability of natural wastewater treatment with little setup and maintenance effort. The drawback is the space requirement. This is why in contrast to many other countries with lower populations – such as Sweden – we find fewer pond treatment plants in Germany.

To date, there have been limited options available to owners of pond treatment plants for mixing and aeration: Surface aerators and floating membrane aerators. The main problem with surface aerators is that, as the name suggests, they only function on the surface and do not have the capacity to circulate the entire volume of the pond. The enhancement of our HYPERCLASSIC^®-Mixing and Aeration System as a floating version solves this problem, and now also enables efficient wastewater treatment here.

Because the HYPERCLASSIC^®-Mixing and Aeration Systems have proven themselves for many years in conventional wastewater treatment plants, our engineers looked for a solution for their use in pond treatment plants and ultimately designed a floating platform. Pulled to the right place and fixed there with taut tie ropes, the hyperboloid-shaped agitator effectively mixes the wastewater pond.

The second function of the HYPERCLASSIC^®-Mixing and Aeration System, aeration with oxygenated process air occurs directly through the hollow shaft to which the mixer body is attached. The air is distributed in fine bubbles within a radius of up to twenty meters thanks to the uniform rotary motion of the mixing element. This also makes the clarification process considerably more energy-efficient than before. For the owners of pond treatment plants, but also for our company, the Floating HYPERCLASSIC^®-Mixing and Aeration System signals a milestone.

System installation, including the platform, is extremely straightforward. The main components are mounted in the immediate vicinity of the corresponding pond treatment plant. Except for regular visual inspections and an annual oil change, the system requires no major operation effort or maintenance.

Swedish customers are delighted

Successful field tests at a wood processing plant in Iggesund (central Sweden) yielded 19 times the amount of aerated water as compared to the previous basin equipment with surface aerators. At the same time, the energy input of the HYPERCLASSIC^®-Mixing and Aeration System Float proved to be only marginally higher.

Consequently, the Swedish operating company ordered four HYPERCLASSIC^®-Mixing and Aeration Systems Float for the aerated zone and four HYPERCLASSIC^®-Mixing Systems Float (without aeration) for the anoxic (oxygen-free) zone at the inlet for Iggesund. They also purchased two iTURBO^®-Blowers for the air supply.

The owners of a similar plant in Lessebo in southern Sweden were also not happy with their surface aerators. They had tested several until they heard about the HYPERCLASSIC^®-Mixing and Aeration System Float. So, on the way back from Iggesund, the test system dropped in at Lessebo and won over management there as well. They initially ordered a HYPERCLASSIC^®-Mixing and Aeration System Float and an iTURBO^®-Blower.

We are pleased that we were able to convince these two customers with our pioneering, energy-efficient product.

The fact that the HYPERMIX^®-Agitator has an excellent design was verified with the Red Dot Award 2021. More importantly, however, is just how well it works and how often it is used – as recently at a production facility of the renowned wine and juice producer García Carrión in Segorbe in eastern Spain.

The tradition of the innovative producer from Castellón province, where the Don Simón brand has become the best-selling Spanish wine in the world, is 130 years old. The producer’s line of products also includes juices, smoothies and soups, especially gazpacho. The Iberian Peninsula experiences increasing periods of water shortages from April to September, which particularly affects public utilities. All these years, García Carrión has also relied on a reliable supply of drinking water from the public network, until the volume of water it consumed exceeded the volume supplied. Nowadays, the producer needs three times more water in the summer months than the public supplier can deliver during that period.

To ensure the water supply for the production plant, García Carrión purchased two large tanks each with a holding capacity of 18,300 m³. In the meantime, five of the HYPERMIX^®-Agitators are in use in the tanks to prevent temperature stratification of the stored water and, consequently, post-germination and algae formation. In addition, continuous mixing ensures that a metered disinfectant is evenly distributed in the water.

Extensive simulations and test procedures before and after installation

After the last vintage was completed, the order from Spain arrived at our offices. Before the HYPERMIX^®-Agitators could be delivered ready for use, CFD (Computational Fluid Dynamics) simulations were first conducted to confirm the required quantity and positioning of the agitators given the complexity and size of the tanks. Because the tanks have the same volume but are shaped differently, three agitators proved to be optimal for one tank and only two for the other.

In a next step, they were assembled from the individual components (agitator, drive, lifting cables, connection cable including protective hose, frame and small parts) at INVENT in Erlangen and then tested. The frequency converters used to control the agitators were also configured. Prepared so well, the following spring, the customers in Spain were able to install the five HYPERMIX^®-Agitators in their tanks themselves. In mid-June, two of our employees set off for Segorbe to test the agitators in operation. Since then, the units have been working perfectly to everyone’s satisfaction.

The joint wastewater association Staufener Bucht, Germany, has placed its trust in the hyperboloid mixing technology of INVENT Umwelt- und Verfahrenstechnik AG. After 21 years in operation, the association has made the decision to replace the 15 HYPERCLASSIC^®-Mixers of the second generation with even more energy efficient mixers of the seventh generation.

A resolution was made in Bad Krozingen in 1967 to clean and treat the wastewater of 24 communities as a joint operation at a central location. This marked the launch of the powerful central wastewater treatment plant (wwtp) named Staufener Bucht. It has been in operation as a community wwtp since 1978. When the population number grew and the load limit was reached, the association expanded the wwtp in 1993. These days, it treats wastewater of a population that has since grown to 114,000, thus it is categorized under size class 5. By aerating and mixing in eight cascades in series, the plant achieves optimal environmental conditions for the activated sludge and the respective process.

Until the mid 1990s, the wastewater treatment focused primarily on carbon decomposition. Due to the Wastewater Ordinance amended at the time, the plant was designed and equipped in accordance with DWA-A 131 for nutrient elimination, in particular nitrogen and phosphorus. As a result of the more stringent requirements, the existing equipment of the wastewater treatment plant was no longer sufficient. For this reason, 15 second generation HYPERCLASSIC^®-Mixers of the same design were installed in the anoxic and optionally aerobic basins in 1996.

Because the hyperboloid mixer is positioned close to the ground, radially high sediment velocities are generated to efficiently suspend the activated sludge flocks. At the same time, the high pumping capacity of the mixer ensures a thorough mixing of large volumes. In this way, the content of the basin is quickly homogenized. Until 2017, the mixers were operated with minimum maintenance requirements, trouble-free and reliably.

Constant improvements in research and development in the laboratory and on large-scale test benches as well as simulations by the specialists of THINK Fluid Dynamix^®, the department for numeric techniques such as CFD and artificial intelligence, have over the years contributed to the improvement of the HYPERCLASSIC^®-Mixer benchmark product. Minor changes to the mixer body, the connection to the shaft and the drive technology had a major effect on the mixer’s efficiency. As such, the seventh generation proved to deliver huge energy savings as compared to the installed second generation.

In 2017, after 21 years in operation, all 15 of the Staufener Bucht wastewater treatment plant’s mixers were replaced with 15 of the latest generation HYPERCLASSIC^®-Mixers. This allows the association Staufener Bucht to save close to 54% electric output. The rated output was reduced from 1.5 kW to 0.75 KW, the output speed from 20.8 rpm to 15.8 rpm. Now, three years later, the energy savings can be confirmed.

“By replacing the existing mixers from 1996 with seventh generation mixers in 2017, by making a comparatively small adjustment to the inventory, we were able to reduce the total energy requirement of the wastewater treatment plant long-term and noticeably,” explains graduate engineer Michael Hacker, CEO of the joint wastewater association Staufener Bucht.

A large number of wastewater treatment plants that INVENT has equipped with the revolutionary hyperboloid technology since the mid-1990s when the company was established follow the example of the Staufener Bucht wastewater treatment plant and to this day still rely on the products supplied by the experts in water and wastewater treatment from Erlangen when upgrading their plants.