[Effect of metal chelating agent on anaerobic digestion under different substrates]

Aided by GC analysis, the effect of metal chelating agent on anaerobic digestion under different substrates was investigated. The results showed that the addition of chelating agent A could greatly promote the methane production under different substrates and speed the conversion of organic acid to methane, especially for propionic acid. When the dosage of chelating agent A was 10 micromol/L, the methane production was, respectively, 19.8%, 133.0% and 45.2% for butyric acid, propionic acid and acetic acid. Also, the arrearage time of methane production was shortened and the production rate increased by 4-fold. During 4-8 d operation, the degradation rate of butyric acid reached 56%. The accumulation of acetic acid was not detected by GC analysis, which demonstrated acetic acid converted from butyric acid was quickly utilized by methane producing bacteria. The increase in methane production due to the addition of chelating agent A could be supported by enzymology. Taking acetic acid as an example, the content of coenzyme F420 in sludge increased to 1.52 micromol/g from 1.20 micromol/g due to the addition of 10 micromol/L chelating agent A.