BIODEGRADABILITY OF DISSOLVED ORGANIC-CARBON IN GROUNDWATER FROM AN UNCONFINED AQUIFER

In a series of aerobic biodegradation studies it was demonstrated that up to 11% of dissolved organic carbon (DOC) of an unfractionated groundwater sample could be degraded microbiologically. After fractionation according to apparent molecular weight and polarity/pK(a), the degradability accumulated for all fractions increased to 21-22%. DOC of apparent low molecular weight and hydrophilic organics was more readily degraded, 27% and 28%, respectively. The degradability of high molecular weight organics and hydrophobic acids was 8.5% and 140/o, respectively. A considerable increase in viable bacterial counts (20-1300 times) was observed during degradation of the DOC. Bacterial activity, expressed by the ATP concentrations, was maintained even in periods of marginal turnover of groundwater DOC.