Effects of tri-valent (Cr(III)) and hexa-valent (Cr(VI)) chromium on the growth of activated sludge.
The effects of Cr(VI) and Cr(III) species on the activated sludge growth rate have been assessed for a batch growth system, for a range of chromium concentration between 0 and 320 mg l(-1). Cr(VI) was found to stimulate microbial growth for concentrations up to about 25 mg l(-1), exhibiting maximum growth stimulation at 10 mg l(-1), whilst the lethal dose was found to be between 80 and 160 mg l(-1). On the other hand, Cr(III) was also found to stimulate microbial growth for concentrations up to about 15 mg l(-1), (with a maximum stimulation concentration at 10 mg l(-1)), whilst the lethal dose was found to lie between 160 and 320 mg l(-1). The results indicate that Cr(VI) is more toxic to biomass at relatively high concentrations (higher than 70 mg l(-1)) whilst it has a more pronounced growth stimulation effect at relatively smaller concentrations (less than 25 mg l(-1)), compared with Cr(III).
Gikas
Petros
P
Ministry of Environmental Planning and Public Works, General Secretariat of Public Works, Special Service of Public Works for Greater Athens Sewerage and Sewage Treatment, Athens, Greece. petrosgikas@yahoo.gr
Romanos
Pavlos
P
D002857:Chromium / Q000737:chemistry* / Q000494:pharmacology*; D012722:Sewage / Q000382:microbiology*
D012722:Sewage; D002857:Chromium