Environment and resources / Water Systems

Clean removal process

Sludge digestion

A sewage treatment plant produces considerable quantities of sludge. Regardless of the downstream sludge disposal or recycling process, it is not only advisable but also necessary to stabilize the sludge first.

We offer various complete solutions here by having the on-site sludge stabilization process required run aerobically, anaerobically or chemically.

An anaerobic sludge stabilization takes place in the so-called intensified anaerobic alkaline sludge digestion process, a fermentation process specially developed for this by our partners. We thus offer the most cost-effective sludge stabilization technology for municipal sludge in wastewater treatment plants.

The co-fermentation of sewage sludge with organic biomass from external sources also makes this technology economic even for much smaller plants.

Scope of services

In this field the Grossmann Group in close collaboration with highly qualified and experienced specialist partners – global market leaders – offers comprehensive services: from the initiation of project and analysis, proposed solutions, process design up to and including the complete construction of a sludge digestion system.

The processes support environmental protection and recovery of biogas with high energy content. The biogas from organic material when used in cogeneration plants is converted as renewable energy into power and heat.

This means that wastewater plant rehabilitation projects running in parallel can rapidly pay for themselves.

Digestion – that is, the anaerobic decomposition of organic matter – occurs in a sequence of individual decomposition processes, running side by side in an anaerobic digester tank. These successive bio-reactions are:

  1. Hydrolysis = dissolution and decomposition of organic solids
  2. Acidification = formation of organic acids
  3. Acetogenesis = formation of acetates
  4. Methanogenesis = generation of methane and carbon dioxide

In project analysis we inform our customers that since the process temperature generally affects the rate of decomposition in the digestion process, the highest digester gas yields are achieved in the mesophilic or thermophilic temperature ranges.