Anaerobic Toxicity
Methanogenic Inhibitors | ||
Compound | Anaerobic | Comments |
Polysaccharides & Simple sugars | ─ | |
Proteins & Aminoacids | ─ | |
Fats & Long chain fatty acids (LCFA) | + | IC50 for LCFA = 500-1.250 mg/l |
Simple alcohols | ─ | |
| Volatile fatty acids (VFA) | + | Non-toxic at pH 7.0-8.0 Toxicity is pH-dependent Non-ionized form is toxic (free VFA) Acetate and propionate: (IC50 = 6-16 mg free VFA/l) |
| Cyanide (CN-) | +++ | IC50= 1 mg/l (unadapted sludge) IC50= 25 mg/l (adapted sludge) |
| Formaldehyde | +++ | IC50= 100 mg/l (unadapted sludge) IC50= 400 mg/l (adapted sludge) |
Inorganic S compounds
| ++ | Toxicity is pH-dependent Non-ionized form is toxic (free H2S) IC50 = 250 mg free S-H2S//l |
| ─ | Only at the very high concentrations IC50 = 3.300 mg S-SO4-2/l |
| +++ | IC50 = 50 mg S-SO3-2/l |
| Ammonia | ++ | Toxicity is pH-dependent Non-ionized form is toxic (free NH3) IC50 = 50 mg free N-NH3/l |
| Heavy metals | +++/++ | Some heavy metals are very toxic Soluble form is toxic. Some metal are very toxic (eg. IC 50= 10-75 mg soluble Cu+2/l) In anaerobic systems, heavy metals are often detoxified by precipitation with carbonates and sulfides. |
| Salts (eg. Na+, K+, Ca2+) | + | Only at high concentrations IC50 = 4.700-7.600 mg/l |
Aromatic compounds | ||
| + | eg. IC50 benzene = 1970 mg/l IC50 ethylbenzene = 340 mg/l |
| + | IC50= 1300 mg/l |
| ─ | IC50>> 4.250 mg/l |
| + | |
| +++ | IC50 pentachlorophenol = 1 mg/l |
| +++ | |
| + | eg. IC50 nitrobenzene = 10 mg/l |
| ++ | eg. IC50 aniline = 900 mg/l |
Aliphatic compounds | ||
| +++ | eg. chloroform IC50= 0.5 mg/l (unadapted sludge) IC50= 45 mg/l (adapted sludge) |
Surfactants | ||
| ++ | IC50 = 20-50 mg/l |
Azo dyes | ─/+ | Highly variable |
Phytochemicals | ||
| ─ | High molecular lignin is non-toxic |
| +/++ | eg. IC50 guaiacol = 2.200 mg/l IC50 isoeugenol = 264 mg/l |
| +++ | eg. IC50 pinene = 180 mg/l |
| +++ | eg. IC50 abietane = 140 mg/l |
| ++ | eg. IC50 bark tannins = 350 mg/l High molecular weight tannins are non-toxic |
To make readers understand well, author should give simple description of IC50, and symbols of “+++, ++, +, and –“.
