Wastewater pioneer Located in Essen since 1937 History

Hans Dahlem senior in the year 1950 Cross-section through the aeration tank of the Essen-Relinghausen sewage
treatment plant
Wastewater pioneer
Located in Essen
since 1937
History
Following his studies Hans Dahlem, as a member of the Ruhr Association,
plans various wastewater engineering plants in the period from 1926 to
1936. Under the direction of the well-known wastewater pioneer, Karl
Imhoff, the first biological sewage treatment plant in Europe, based on
the activated sludge process, as well as projects using biogas to drive the
aeration blowers in which Hans Dahlem had already collaborated as young
engineer, is established. In 1929 Hans Dahlem is involved substantially in
the foundation of the wastewater association for the catchment area of the
“Weißen Elster” in Prussia, Saxony and Thüringen.
At the age of 32 Hans Dahlem founds the Dahlem Engineer Office in Essen
for residential and industrial water management as well as the construction
of long distance pipelines. Further areas of responsibility such as hydraulic
engineering, water and solid waste management as well as structural design,
surveying and roads are added in quick succession. Here Dahlem delivers
comprehensive and complete engineering services to the client through the
employment of engineers from all specialist disciplines involved. To this day
the company headquarters has remained in Essen whereby the team of staff
has moved several times as a result of the expansion of the office, - 1996 for
the first time into their premises in the office block “Bonsiepen 7” in Essen-
Bergerhausen. Today more than 80 members of staff work here.

Sewage treatment plant Boras 1954 Metallurgical plant Lübeck
Cooling tower for the blast furnace gas and wash
water with settling tanks below (cyclic tower)
Modern and flexible In its early years the office, together with Karl Imhoff, plans sewage treat-
ment plants in Berlin, Danzig and Rostock; first Europe-wide projects are
processed, inter alia in Sweden and Austria. Already at this time a sewage
treatment plant design is created with which nitrogen can also be eliminated
via nitrification and denitrification. Even then the bases for today’s modern
process engineering for the treatment of wastewater, general drainage plans
and sewer network planning
are produced for municipal
and industrial concerns.
The sphere of activities of
the engineering company is
expanded to cover long dis-
tance pipelines for gas, water
and various chemical gases.
With our current large projects
we profit from the many years
of experience in this area.
Within the scope of prima-
ry water management tasks
the Dahlem office produces
wastewater loading plans for
the Rhine, Weser, Elbe and
Danube rivers; today we are
substantially involved in the
redesign of the Emscher river.
History
Process diagram of the Berlin-Osdorf sewage treatment
plant from the 1942 design

1981 – Award of the “Commandeur de l’Ordre
du Merite” to Hans Dahlem by the Environment
Minister Josy Bartel
Dahlem and Luxembourg
Dr Hans-W. Dahlem
takes the helm
Stamp with the Luxembourg-Bessen sewage treatment plant
The development of the Dahlem Engineering Company is closely linked
with the development of the water industry in Luxembourg. Hans Dahlem
starts his consulting activities for the Grand Duchy as early as 1940. The
Dahlem office plans sewage treatment plants for the whole of Luxembourg,
develops plans for the country’s surface waters up to and including advice
for the establishment of wastewater associations and elaborates plans for
industry. In 1966 the office “Dahlem, Schroeder et Associés” is established
in Luxembourg. Right up to today joint projects in all areas of the water
industry, both national and international, are processed there. In 1981 Hans
Dahlem is honoured with the award of “Commandeur de l’Ordre de Merite”
by Grand Duke Jean of Luxembourg for his services to the Grand Duchy. The
subject of the only postage stamp in the world showing a sewage treatment
plant is the main wastewater treatment plant of the City of Luxembourg. In
1987 Hans Dahlem receives the Bundesverdientskreuz for services to the
environment.
In 1978 Dr Hans-W. Dahlem becomes joint owner of the office. Following
studies at the Technical University in Karlsruhe, Assessor Exams and work in
municipal authorities and with the Ruhr Association, he is awarded his doc-
torate at the Technical University in Darmstadt and works there as university
lecturer. Further experience is gained in the firm. In 1978, for his scientific
activities, he receives the Karl-Imhoff Prize at the International Wastewater
Symposium in München.
History
Under his leadership the office expands further. Keeping faithfully to the
motto “we are there where our projects are” the partner office “Dahlem and
Peil” is founded in Düren and the offices in Darmstadt, Gütersloh, Gronau and
Weimar are established. Finally the office in Regensburg is opened in order to
process our projects in southern Germany. At this point the number of staff,

Water supply in the Yemen Al Bireh sewage treatment plant, Palestine
Closing cycles
Dahlem international
including the associated companies, has grown to 250. Since then Dahlem
has expanded its range of activities also to tasks of project development and
general technical and economical controlling.
In the municipal sector hundreds of projects for the supply of drinking water,
wastewater discharge and treatment, landfill technology and infrastructure
techniques are processed. Development measures in various dimensions
belong equally to the spectrum of services as do projects for the storage,
treatment and percolation of stormwater.
In the industrial area activities are expanded to the field of industrial water
treatment and processing. Biological wastewater treatment plants are pro-
duced for coking plants, artificial resin operations and the petro-chemical
industry as well as for textile and foodstuff concerns. Well-known firms in
the iron and steel industry and in coal mining are converted to the saving of
water and protection of the environment and to internal recycling. Advice
to industrial concerns and the planning of projects for industrial water
management to this day form a part of the Dahlem engineering services.
Since the early 70’s Dahlem has been working intensively abroad. Early pro-
jects in Africa and Latin America on behalf of the Wold Health Organisation
and World bank are currently continued in projects of the Corporation for
Technical Collaboration, the Reconstruction Loan Corporation and the
European Commission. Dahlem is operating in Estonia, Poland, Slovakia,
Serbia, Kosovo, Bulgaria, the Yemen, Palestine and China. In 2001 the Al-
Bireh wastewater treatment plant – the first modern biological wastewa-
ter treatment plant in Palestine – is officially opened by Federal German
President Rau.
History

Tradition
Development
Future
For over 65 years Dahlem has been a leader for development in the fields of
water – wastewater – surface waters – solid waste – infrastructure. Research
and development and the employment of the knowledge derived from these
are the basis of our projects. The office infrastructure is always in step with the
state of the art - modern project processing is always guaranteed.
Members of the office staff publish numerous technical-scientific papers on
various subjects. They are active in committees, assessment groups, advisory
boards and boards of management in various technical organisations and, in
specialist presentations, have for many years reported on developments and
experience.
History
Dahlem is always available to its clients as reliable partner.