Institute for Sanitary Engineering, Water Quality and Solid Waste ...

Urban Drainage SE
Karl-Imhoff-Prize
In 2009, Ulrich Dittmer from the Chair for Sanitary
Engineering and Water Recycling was
awarded the Karl-Imhoff-Prize of the DWA (German
Water Association). After Professor Krauth
(1971) and Professor Thomanetz (1984) he is
the third scientist from ISWA to receive this renowned
award.
The Karl-Imhoff-Prize was established in 1965 in recognition
of the outstanding merits of Karl Imhoff. The
prize has been handed over at the national DWA-convention
in Augsburg on the 27th and 28th of October
2009.
Ulrich Dittmer was awarded the prize for his PhDthesis
on “Retention and Transformation Processes of
Carbon and Nitrogen Compounds in Retention Soil Filters
for CSO Treatment”. Retention Soil Filters (RSF)
are applied if the condition of the receiving water requires
an enhanced treatment of discharges from CSO
structures. In previous field studies, RSF had shown a
generally high purification capacity. However, reliable
prediction of the performance of RSF as well as further
optimization of design and operation required a
deeper knowledge of the internal processes. The PhDthesis
addressed open questions on these processes,
focussing on retention and transformation of organic
carbonates and nitrogen compounds.
The results showed that the elimination of ammonia is
based on a two-step process: during infiltration ammonia
is absorbed by biofilms within the filter layer.
Concentrations are reduced to a background level. Nitrification
of the retained nitrogen takes place during
the following dry period. Nitrification activity is highest
immediately after the draining of the filter layer. Long
term loading and high ammonia loads can lead to a
breakthrough of the inflow concentration. In a mathematical
model ammonia elimination can be represented
by a storage unit that is filled during infiltration
due to absorption and emptied in the dry periods by
nitrification.
Organic carbonates – represented by COD – show a
different behaviour. The particulate fraction is retained
at the surface of the filter layer and oxidized during dry
periods. For soluble COD compounds the filter shows
an almost constant removal rate. Oxygen consumption
during infiltration indicates immediate degradation.
Ammonification during dry periods shows that there is
also delayed degradation of organic substances that
have previously been retained by absorption.
The Karl-Imhoff-Prize is handed over by DWA-president
Otto Schaaf (left)
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