The problem of sewage sludge disposal

Increasing industrialisation worldwide, the increased use of medicines and urbanisation have meant that agricultural application of sewage sludge to fields is increasingly problematic. In some countries, this is now prohibited or is to be prohibited in the future. 

The aim is to protect people and the environment from the introduction of pollutants. At the same time, it is important to preserve the phosphorus contained in the sewage sludge, as it is indispensable for agriculture – especially against the background of limited global phosphorus deposits. 


 

The complexity of sewage sludge

In practice, sewage sludge has very different properties. This refers not only to water content and chemical composition, but also to their drying behaviour. All the better that stela can rely on numerous drying tests and practical experience with the drying of sewage sludge. In addition to the treatment of the sludge by additives, the origin of the wastewater is particularly crucial:

• Industrial sludges from, for example:
  • Dairies, breweries
  • Large agricultural holdings
  • Food processing plants
  • Chemical industry
  • Metalworking industry / electroplating / coating
  • Other industrial sectors
     
• Municipal sewage sludge, influenced by:
  • Urban sewage
  • Rural sewage
  • Special soil conditions / sediment ingress
  • Special eating habits, fat content
  • Weather events, precipitation
  • Special events, major events

The high variability poses major challenges for plant operators – adaptable drying technology is needed here.

Drying technology that adapts to the sludge

To handle the complexity of the sludge, each sewage sludge drying plant from stela Laxhuber is designed exactly to the specific requirements. In addition, the sludge dryer can be adjusted comprehensively during operation. This applies, among other things, to the following parameters:

• Size and shape of sewage sludge granules
• Height of the sewage sludge granules
• Drying temperature
• Ventilation intensity
• Drying time

If necessary, an automatic controller for the final humidity takes over control to always achieve the desired target humidity.

Exhaust air treatment – avoid, reduce and clean

In the drying of sewage sludge, the exhaust air typically contains dust, odours and other emissions. Since belt dryers from stela Laxhuber work with low temperatures, it is advantageous to better comply with emission limits. Nevertheless, multi-stage exhaust air scrubbers, biofilters or other odour elimination devices are used as required. To keep the size and costs of these components low, stela relies on minimised quantities of exhaust air, supported by precisely designed recirculation technology. This allows the exhaust air treatment system to be made much smaller  
If cooling capacity is available, the drying system can be supplemented by condensers in the circulating air circuit. Experience with stela's patented RecuDry ® technology enables an almost exhaust-air-free drying process. 

The right sewage sludge dryer for your needs: stela type BTS

Sewage sludge, especially in combination with highly saturated air streams, places special demands on sewage sludge drying. That is why we at stela are specially focussed on:

• Corrosion-resistant stainless steels
• Specially developed process belts
• Explosion protection concepts
• Chemically resistant structural elements

Belt dryer BTS was developed for these special requirements – our specialist for the drying of wastewater sludge. 

downloads

more information:

• brochure belt dryer for sewage sludge1 MB
• reference list belt dryers for sewage slduge16 MB

Контакт

Референции

Belt dryer BTL for RDF
in Spain

Dryer type: BTL 1-3000-18
Dryer output capacity:
RDF: 3.7 t/h from 42% to 15%

Belt dryer BTL for dewatered (sewage) sludge
in Belgium

Dryer type: BTLU 1-3000-18
Dryer output capacity:
dewatered (sewage) sludge: 0.1 t/h from 85% to 5%

Belt Dryer BTU for sewage sludge
in Romania

Dryer type: BTU 1-6200-18
Dryer output capacity:
sewage sludge: 1.2 t/h from 90% to 25%

Belt dryer BT for sewage sludge
in Germany

Dryer type: BTU 1-6200-36-4-4
Evaporation:
sewage sludge: 12.5 H₂O/h

To the references To the case studies

Контактное лицо

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Телефон: +49 8724 899-10
Эл. почта: sales[at]stela.de

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