Bacteriological studies for Kranji catchment

A study investigating the bacterial concentrations in Kranji Catchment and the factors affecting the bacterial die-off rates was carried out. The scope of the study involved field water sampling as well as an attenuation study of E. coli. A first-order attenuation model was constructed to establish the effect of solar radiation on the inactivation of E. coli and determine if the bacteria die-off substantially before reaching Kranji Reservoir. Field sampling comprised comparison of the bacteriological levels in KC02 was done with reference to past studies conducted. IDEXX Colilert® Most-Probable-Number (MPN) method was used to quantify the bacterial levels for both total coliform and E. coli. Results from water sampling have shown that the water quality in KC02 has greatly improved since January and July 2009. Bacterial concentrations were generally lowered by 7 to 29 times. Results for the attenuation study were inconclusive however, due to external factors affecting the results, hence unable to verify the effect of solar radiation on bacterial mortality. However, it was noted that the final first-order decay constant of bacteria, k_f, of 22 per day, determined from the results of the attenuation study in the presence of light, appeared to be relatively high as compared to past study. One other significant finding was that coliforms were generally insensitive to light levels whereas the effect of light is more significant on E. coli. This was observed from the averages of E. coli and total coliform MPN. For the light condition, average E. coli MPN was found to be approximately twenty two folds of that for the dark condition, whereas the average total coliform MPN for the light condition is only approximately two and a half times that for the dark condition.Bachelor of Engineering (Environmental Engineering