Solutions for the process water treatment in the producing an manufacture of glass Water treatment in the glass industry

[Translate to Englisch:]

In der Glasindustrie wird an vielen Stellen Prozesswasser im Kreislauf gefahren. Ein häufiger Anwendungsfall ist das bei der Glasproduktion entstehende „Kratzerwasser“, welches neben feinen Glaspartikeln und Trübstoffen auch Öle und Fette enthalten kann. Die Schmutzstoffe im Wasserkreislauf verursachen u. a. Ablagerungen an Kühltürmen, Rohrleitungen oder Wärmetauschern und führen zu höherem Verschleiß in der Anlage, z.B. an Pumpen. Öle und Fette können eine ungleichmäßige Kühlung mit sich bringen. Durch die kontinuierliche Reinigung des Kühlwassers mit einem Schrägklärer werden die Feststoffe entfernt und Öle und Fette aufkonzentriert.

[Translate to Englisch:]

Die Feststoffe sammeln sich im Schlammtrichter und werden beispielsweise mit einem Vakuumbandfilter  nachentwässert. Aufschwimmende Öle können an der Wasseroberfläche abgepumpt und durch einen Koaleszenzabscheider separiert werden.

Eine weitere Anwendung ist die Reinigung von Glasschleifwasser. Bei der Aufbereitung und Kreislaufführung von Schleifwasser kommen neben dem Schrägklärer auch Schrägfilter, Endlos- und Vakuumbandfilter zum Einsatz. Gerne bieten wir Ihnen neben unseren Komponenten auch schlüsselfertige Anlagen inklusive Pumpstationen, Kühltürme, etc. an.

Pilot plants of Leiblein

Our products are available to rent for pilot tests. Due to our extensive rental park, we can put together complete test systems individually for your task.

Versatile applications References

Treatment of glass grinding water
The project

The products of a glass factory are cut and polished in the last process step. The processing machines are supplied with cooling water. The cooling water, containing glass particles, is collected in a pump pit. The water is to be clarified by a treatment system and led back to the processing machines.

Functional description

The contaminated water is pumped into a lamella separator, after small amounts of flocculant was added which helps to separate finest particles as well. The glass particles settle onto the lamellas and slide into the sludge funnel. A continuously running rabble rake prevents the sludge from caking. When a certain sludge level is reached, the sludge is exported and dewatered by an inclined filter. The clean water from the inclined filter flows into the clean tank and gets pumped to the processing machines as necessary.

Cooling water circuit in a glass factory
The project

Hot glass waste occurs during the production of glass which is exported via a scraper basin filled with circulating water. The circulating water is mainly polluted by oils, fats and small glass particles. The water is heated by the hot glass waste.For the clarification of the circulating water a lamella separator is preferably used.

Basic principle of the lamella separator

The water flows from bottom to top passing inclined lamellas. Solids settle onto the lamellas by sedimentation and slide into the sludge funnel at the bottom. The clarified water flows into the clean water channel at the top.

Advantages of clarifying the cooling water
  • Savings in freshwater and wastewater costs due to the circulation
  • Separate disposal of oil and glass sludge (particles)
  • Compliance with environmental constraints
  • Reduced environmental burden due to less water consumption
  • Solids (glass particles) are returned into the production cycle
Filtration of glass washing water
The project

In a factory for laminated glass, the products are cut into slices and the edges are bevelled. The glass sheets are washed with circulated demineralised water afterwards. To improve the washing results, decrease wear and reduce the water costs a filtration system for the washing water was to be upgraded.

Functional description

After the washing process the washing water flows onto an inclined filter. The particles (glass abrasion, foils, etc.) are held back by the filter fleece. The filtrate flows into the tank which is positioned underneath the filter.

The water is pumped back into the washing plant with a centrifugal pump. When the filter cake reaches a certain thickness, the flow resistance increases and the water dams up on top of the filter cake. A floating switch triggers the filter fleece feeding system.

The sludge is stripped off and slides into a sludge container. The consumed fleece is rolled up and can either be disposed separately or recycled.

Technical details
Type of waterdemineralised water
Volume flow rate of the circuit200 l/min; 5,5 bar
Temperature60 °C
Filter area0,7 m2
Filter fleece

Polyester ca. 10-15 µm

Treatment of process water from glass fibres production
The project

A manufacturer of glass fibres for the production of high-quality products as for example filter fabric, wallpapers, refractory products, roofing membranes etc. operates several spinning mills. In the spinning machines glass granulate is melted and thinnest glass fibres are produced. Process water is needed for cooling and for transportation of glass fluffs.

The process water to be treated runs via chutes from the spinning machines into a special channel system. The channel system is fitted with flushing nozzles to prevent glass fibres from depositing in the channel. The water flows through the channel system into several rotation screens.

The rotation screen separates and screens suspended solids and fibres from process and wastewater. The effluent is impinged inside the drum and flows through the filter drum into the clear water tank. Solid particles are held back by the filter and are exported by a screw. The rotating drum is continuously cleaned by a brush roller and a spraying device.

The purified water flows to a pump system and gets pumped back to the spinning machines. The separated glass fibres material is exported onto a conveyor band and collected in a container.



Purification of grinding water using a vacuum belt filter
The project

The Franconian company Apollo-Optik GmbH& Co. KG in Schwabach, as a part of the Pearle group, has more than 700 branches in Germany. The company’s product range reaches from cutting-edge eyeglass frames and fashionable sunglasses to special glasses and high quality contact lenses.

One production step is the full and semi-automatic grinding of customer-specific spectacle lenses, which are sent, together with the frames, to the branches for the final assembly.

Preliminary remark

For the production of spectacle lenses, mineral materials (silicate glass) and synthetic glass is used, whereby especially polycarbonate becomes increasingly important. The lenses are made from a blank. A high proportion of the material is shaped by stock removal. To cool the lenses and to remove the chips, large amounts of grinding water is needed.


The water used for the lens processing has to be treated so that it can be recirculated. There are three common processing principles used to separate abrasive particles:

  • Sedimentation
  • Centrifugation
  • Filtration

A filtration process has been chosen, due to the small density difference between plastics material and water.


The effluent from the different processing stages is fed to a central grinding water tank. Coarse material as for example glass breakages is removed by a coarse filter-basket. The water is fed to the vacuum belt filter using special effluent pumps. All filterable particles are separated and the purified water flows into a clean water tank. Water losses can be compensated by adding fresh water into the tank. The clean water is then fed back to the manufacturing machines. Furthermore, controls a separate circuit the temperature in the clean water tank, ensuring a steady flow temperature, which is necessary to produce high quality lenses.

Filtration within smallest space:

The cleaning system could be realised within smallest space using the Leiblein vacuum belt filter. The external dimensions are only (l x w x h approx.) 2,6 x 2 x 2 m. A very dry abrasion is gained through the integrated vacuum unit.

Generous design

The plant was constructed for a throughput of approx. 15m³/h. The capacity of the effluent and clean water tank had been generously designed to compensate for fluctuations during production. Furthermore, high demands were placed on the operating reliability; therefore, several pumps were designed redundantly.

Future proof

The chosen concept allows to react efficiently to possible capacity enlargements. The system is modular expandable, which means that further filtration systems can easily be integrated parallel to double or rather multiply the throughput.

Satisfied customers

Due to the modular design and deliberated planning the whole system was installed within a few days. The plant with the required tanks and accessories were pre-assembled as far as possible and installed directly from the transport vehicle onto the prepared base. The integration into the existing system was straight-forward. Further adaption and change requests can be met spontaneously and without difficulty.

Apollo-Optik GmbH & Co. KG

Process water circuits in glass production Leiblein products for the glass industry