Refferences :

Oxygen

Sulfur Compounds

Organic Acids (Fatty Acids & Amino Acids)

Nitrate (NO3-)

Ammonium (NH4+) and

Ammonia (NH3)

Heavy Metals

Other InhibitingThresholds

Inhibition Compounds on Anaerobic digestion

1. Oxygen

• The exclusion of oxygen is not absolutely necessary for acidogens

• Avoiding the presence of oxygen more than 0.1 mg L − 1 O 2 for methanogens

2. Sulfur Compounds

• Sulphate ions inhibits to the process by following this reaction:

• Hidrogen sulphide inhibits the metabolic activity of anerobic bacteria.

• Sulphate is reduced to hydrogen sulfide by sulphate reducing bacteria (SRB)

• Hydrogen sulphide is formed by degradating of organic coumponds.

Monitoring sulphate/sulphide control:

• Increasing the pH (caustic soda addition)

• Addition precipitation chemicals (iron salt) and Physico-chemical techniques (stripping)

The process are coagulation, oxidation, precipitation (Oude Elferink et al., 1994; Song et al., 2001; Chen et al., 2008).

3. Organic Acids (Fatty Acids and Amino Acids

• Long chain fatty acids (LCFA’s) inhibit on methanogens.

Propionic acids performs most inhibitor (Dublein and Steinhauser, 2008)Lauric acids performs most inhibitor (Gerardi, 2003)

Volatile acids such as acetate, butyrate, and propionate causes a decreasing pH.

Nitrate (NO3- )

• The redox potential occure more negative• Gas quality have high portion of nitrogen

content

Ammonium (NH4+)

and Ammonia (NH3)

Nitrogen source-providing buffering capacity-

(Dublein and Steinhauser, 2008)

(Gerardi, 2003)

Controling the ammonia content• ANAStrip-process

Heavy Metals

• They are stimulator the activity of bacteria• But in higher concentration can be toxic• This groups incudes lead, mercury, cadmiun,

uranium, iron, zinc, copper, chromium, manganese, molybdenum, nickle, and selenium.

Other inhibiting thresholds

• Disenfectans• Chlorinated hydrocarbons• Benzene ring compounds• Cyanide• Recalcitrant (flavour compounds, essential oil)