Effect of aromatic compounds,humic acids and lignins on growth of the earthworm eisenia foetida

Thirty eight low molecular weight aromatic compounds, two humic acids, and five lignins were tested for their effects on the growth and survival of the earthworm Eisenia foetida with activated sludge as food source. Benzenoid molecules with two methoxyl or methyl groups were generally more toxic than analogous molecules substituted with one or two hydroxyl groups instead. Placing a carboxyl group or groups on a molecule of relatively high toxicity tended to reduce its toxicity or to result in a totally innocuous substance. Tannins and molecules which could be easily polymerized to form tannin-like substances were generally non-inhibitory to growth, as were humic acids and lignins.