Table 1: The characteristics of the investigated dye effluents.

Effluent from dyeing process of Dyeing technology Abbreviation in text Azo dyes in effluents Other substances in effluents pH COD (mg ) Max of absorbance ( ) in raw effluents Comments
C.I. nameChemical character

Polyacrylic fibresContinuous processWPacBasic Yellow 28
Basic Red 22
Basic Blue 41
Basic Black
Thickener (Prisulon),
Auxiliary agents (Roksol PAN 3K),
Glutaric acids
4.4 ± 0.114400.262 (340 nm)
0.159 (430 nm)
0.166 (540 nm)
0.199 (610 nm)
Biologically stablea

Acid Red 88Anionic
LeatherBatch processWLeatAcid Blue 193Anionic<10% of tannery wastes7.0 ± 0.14600.365 (510 nm)
0.075 (620 nm)
Biologically unstablec
Other dyesbAnionic

Flax fabricBatch processWFlaxUnknownAnionicUnknown6.9 ± 0.19100.965 (350 nm)dBiologically stablea

Cotton fabricBatch processWCotDirect Black 22AnionicUnknown8.2 ± 0.2893040.05 (480 nm)Biologically stablea

aThe biological stability of dyeing effluent was estimated based on changes in their appearance (changes in UV-VIS spectrum, precipitation of sediments) and their digestion during the storage period of 28 days (at 20°C under anaerobic conditions).
bOnly in trace amounts.
cEffluents were digested during short-time storage (about few hours) but their absorbance at 510 nm did not undergo significant changes.
dAbsorption band without any clear maximum.