DIG-L: sewage sludge digestion

["AHHM Schomaker" <ts@HASKONING.nl>]

Sewage sludge digestion in The Netherlands is still based on 
CSTR-technology from the early nineteenseventies: mesophilic 
digestion at 32 °C with gas-mixing and external heat-exchange.
Most digesters suffer from, amongst others, problems with floating 
layers resulting in high maintenance costs, in particular for labor.
Although at 60% of the installed sewage treatment capacity in 
Holland sludge digestion is applied, it is not very popular compared 
to aerobic sludge stabilisation, needed for bio-P and bio-N removal 
in the waterline. 

Since renewable energy production also is a grow market in 
Holland, I want to start a discussion on the latest developments in 
the technical/technological aspects of sludge digestion. Main 
issues for my part are the increase of gasproduction, reduction of 
mixing energy, optimal heating of the digesters and easy removal 
of floating layers. Please feel free to add new issues.

Please also reply directly to my email-adress below, so I can make 
a list of contributors to this discussion !

Ton Schomaker

+------- HASKONING  Consulting Engineers and Architects -------+
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|  AHHM Schomaker                     E-mail: ts@HASKONING.nl  |
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