Integrierte Vermeidung und Verminderung der Umweltverschmutzung

Chapter 3
While the overall water used is about 15 m 3 /t sugar beet processed, the consumption of fresh
water is 0.25 – 0.4 m 3 /t sugar beet processed, or even less in modern sugar factories. Water
consumption depends on the activities of each installation, e.g. more water is consumed in an
installation that extracts and refines sugar beet, than one that does only one of those activities.
In Austria, the consumption of water is of 1.5 m³/t of sugar beet processed, equivalent to
9 m³/t produced sugar, was reported [152, Austria, 2002]. Table 3.69 shows the water
consumption in Danish sugar factories.
Parameter Specific value
per tonne of beet processed
Specific value
per tonne of sugar produced
Average Range Average Range
Water (m 3 ) 0.37 0.23 a – 0.50 b 2.39 1.56 a – 3.21 b
a Excluding cooling water (two factories)
b Including cooling water (two factories)
Table 3.68: Water consumption in Danish sugar factories
[139, Nielsen E.H. Lehmann, 2002]
3.3.8.1.2 Waste water
Sugar beet is 75 % water, and the extraction process, by definiton, aims to release a high
proportion of water contained in the beets. Approximately half of this water is lost due to
evaporation or inclusion in various product streams. The remainder is, after usage for washing
and fluming, a source of high strength waste water.
The beets are floated through the cleaning stage where stones, weeds and other gross
contaminants are removed. The transport water pumped off with the soil sludge can be up to
70 % of the beet. It has a high organic contamination due to the soil and sugar from damaged
beets. Its COD is 5000 – 20000 mg/l.
The beets then enter the installation, where they are washed before being sliced into cossettes to
maximise the surface area for the extraction process. The condensate from the evaporation and
crystallisation stages is partly used as process water in several process stages, including beet
washing. Process waste water is deemed to be the excess condensate from the concentration and
crystallisation stages. This surplus condensate is high in ammonia and relatively low in COD
content. Waste water with high BOD levels is produced in large volumes [13, Environment
Agency of England and Wales, 2000] and is cleaned in a WWTP.
3.3.8.1.3 Solid output
During the reception and fluming of the sugar beet, soil, stones, sand and vegetable matter, e.g.
seeds, beet tails and leaves, are removed. The amount of the earth adhering to the beet may vary
greatly depending on, e.g. the weather conditions during harvesting and the design and
operation of the harvester. In the annual processing of 500000 tonnes of beets, an average of
60000 tonnes of soil accumulates [87, Ullmann, 2001]. The soil arriving at the installation is
removed in settling ponds. The sediment may be re-applied to arable land or may be used for
other purposes, such as horticulture or civil engineering works. The vegetable matter is
separated from the fluming water for sale as animal feed or fertiliser.
The sugar content of the beets does not vary greatly, e.g. 18.4 % in Austria and 13.9 % in
Greece [87, Ullmann, 2001]. The efficiency of sugar extraction is about 90 %. There are other
substances either in the wastes or by-products, such as beet pulp. After sugar is taken out, the
extracted beet pulp is pressed. The wet pulp may then be dried. Beet pulp is normally sold as
sweet feed for cattle. Another by-product is carbonatation lime. Juice purification is done using
lime. It may be pressed and sold to de-acidify or balance the pH of soil.
198 January 2006 RHC/EIPPCB/FDM_BREF_FINAL