Integrierte Vermeidung und Verminderung der Umweltverschmutzung

3.1.1.2.2 Composition of waste water
Chapter 3
FDM waste water is extremely variable in composition. It is, however, typically high in both
COD and BOD. Levels can be 10 – 100 times higher than those of domestic waste water.
The BOD5 content of the main FDM constituents and some products is shown in Table 3.3.
BOD5 content
0.65 kg/kg carbohydrate
0.89 kg/kg fat
1.03 kg/kg protein
0.07 – 0.10 kg/l milk
0.18 – 0.37 kg/kg meat
0.06 – 0.09 kg/kg fruit or vegetables
Table 3.3: BOD5 equivalent of general FDM constituents and some products
The SS concentration varies from negligible to as high as 120000 mg/l. Waste water from, e.g.
the meat and dairy sectors contain high concentrations of edible fats and oils.
Food processing waste waters vary from very acidic, i.e. pH 3.5, to very alkaline, i.e. pH 11.
Factors affecting waste water pH include:
• the natural pH of the raw material
• pH adjustment of fluming water to prevent raw material deterioration
• use of caustic or acid solutions in processing operations
• use of caustic or acid solutions in cleaning operations
• acidic waste streams, e.g. acid whey
• acid-forming reactions in the waste water, e.g. high yeast content waste water, lactic and
formic acids from degrading milk content
• nature of raw water source, either hard or soft.
Waste waters contain few compounds that individually have an adverse effect on WWTPs or
receiving waters. Possible exceptions include:
• salt where large amounts are used, e.g. pickling and cheesemaking
• pesticide residues not readily degraded during treatment
• residues and by-products from the use of chemical disinfection techniques
• some cleaning products.
The presence of pathogenic organisms in the waste water may be an issue, particularly where
meat or fish are being processed. The amount of plant nutrients may also be an issue. For the
biological waste water treatment of the waste water, the ideal BOD:N:P ratio is about 100:5:1.
At this level, FDM processing waste water would be too deficient in N and/or P to support
biological activity during treatment. Excessive levels of P can also occur, particularly where
large quantities of phosphoric acid are used in the process, e.g. vegetable oil de-gumming, or in
cleaning. If such waste water becomes anaerobic during treatment then there is a risk that
constituents containing phosphate could release phosphorus to the final discharge water. The
use of nitric acid in the process produces a similar effect, thereby increasing the levels of nitrate
in the waste water.
Some common sources of fugitive and unscheduled emissions, i.e. accidental releases, are:
• contaminated storm-waters
• storage tank leaks
• pipework leaks
• spillages
• bund drains
• leakages from flanges, pumps, seals and valve glands.
RHC/EIPPCB/FDM_BREF_FINAL January 2006 117