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.