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
Cationic
Cationic
Cationic
Cationic
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.