Microbiological Assessment of River Water Quality in Samoa

The microbiological quality of two rivers in Samoa was examined over eight months to provide some baseline data on the composition of these water resources. Total coliform (TC) and faecal coliform (FC) were quantified using the membrane filtration technique while pH, dissolved oxygen (DO) and biological oxygen demand (BOD5) were determined using standard methods. Samples were collected monthly from a total of five sites from Gasegase and Loimata o Apaula (LoA) rivers to also identify seasonal and spatial variations of these parameters. All sites exceeded the threshold for TC and FC as stipulated in the Samoa Drinking Water Standards for open waters. DO ranged from 8.21 8.29 and 7.92 8.85 mg/L for Gasegase and LoA respectively while BOD ranged from 4.28 5.61 mg/L for Gasegase and 4.45 5.15 mg/L for LoA. There was no significant difference in the spatial distribution of all parameters across the two rivers and between the sites in each river. Dissolved oxygen concentrations were generally higher during the dry season but for pH and BOD5, concentrations were higher in the wet season along with the concentration of coliform bacteria. However, the seasonal variation was not significant as supported by statistical testing. Bacteria in water could be linked to faecal wastes, decomposition of organic matter in the rivers, weathering and soil runoff into rivers and leaching of untreated wastewater.