Hydrolysis of 4-methylumbelliferyl-β-D-glucuronide in differing sample fractions of river waters and its implication for the detection of fecal pollution

The hydrolysis rate of 4-methylumbelliferyl-β-D-glucuronide (MUG-HR) was determined in unamended samples, filtered samples, and in corresponding buffer resuspended filter residues of various river waters of slight to excessive fecal pollution covering a four orders of magnitude range. Regression analysis of the log MUG-HR of the unamended water samples versus the log MUG-HR of the filter residues revealed a highly significant linear relationship (R²=0.94; p<0.001). The median of the MUG-HR of the filtrated water samples was about 10% the MUG-HR of the corresponding unamended water samples. If MUG-HR determinations were used as a surrogate for estimating fecal coliform contamination, both the MUG-HR of the unamended water samples and the MUG-HR of the filter residues would have been equally adequate techniques at river sites of higher fecal pollution levels. However, at river locations of decreased fecal pollution, MUG-HR determination of filter residues appeared to be the more sensitive technique in order to estimate fecal coliform concentrations.