Purification of Wastes from a
German Yeast Plant
DIETER LONDONG, Manager
Civil Engineering Department
Emschergenossenschaft and Lippeverband
Essen, Western Germany
INTRODUCTION
The yeast plant, the waste purification of which is subject of my report, is
situated on the eastern border of the Rhenisch-Westphalian industrial district within
the area of the "Lippeverband". This is a public-legal association of all towns, villages
and larger industrial works in the western catchment area of the Lippe River, a tributary
to the Rhine River. The duty of this association is water-management especially the
purification of waste waters. By joining all parties causing wastes and benefiting from
water-engineering projects, the association is in a position to distribute the cost of such
projects to a great number of municipalities, villages and industrial undertakings, resulting in essential cost savings to the individual party in many cases. In the region
south of the "Lippeverband," i.e. in the catchment area of the Emscher River, the
"Emschergenossenschaft" carries out similar duties in personal union with "Lippeverband."
YEAST PRODUCTION AND YEAST WASTES FROM THE PLANT
The yeast plant processes beet-sugar molasses to compressed yeast and alcohol.
The alcohol is extracted only from the first production stage, where mother yeast is
produced. In the subsequent aerobic process free of alcohol, the mother yeast
continues to grow with a high rate of propagation. The final product is dewatered,
sold as so-called "compressed yeast" and is used mainly for baking.
For the cultivation of yeast, molasses are used as nutrient substrate. The nutrient salts missing for the production of protein by the cells, are added in the form
of ammonia and phosphoric acid (P2O5). The total water consumption including
cooling water amounts to 850,000 cu m/yr. 350,000 cu m of wastes are produced
annually. This gives, with five working days per week, 1350 cu m/working day.
Reports on the water consumption of compressed yeast works in Europe vary between 40 and 100 cu m/ton of molasses processed and between ten and 30 cu m of
wastewater produced per ton of molasses.
The wastes from the yeast plant are composed of: 1) Burnt slop from the
burners for alcohol distilling. (This slop is very highly loaded with alcoholic substances, weak acid is discharged rather evenly at temperatures of 190 F); 2) Wort from
the alcohol-poor production of yeast, in other words:  the consumed molasses widely
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