Comparison of enumeration techniques for the investigation of bacterial pollution in the Berg River, Western Cape, South Africa

An Paulse,W Khan,Va Jackson

doi:10.4314/wsa.v33i2.49055

Abstract

The study was aimed at assessing techniques, which would provide an accurate indication of the planktonic bacterial pollution load in the Berg River, Western Cape, South Africa. Sampling of sites started in June 2004 and continued for a period of 1 year until June 2005. The most probable number (MPN) technique was used to determine the level of faecal coliforms and E. coli, while the heterotrophic plate count method was used to determine the amount of culturable micro-organisms in planktonic samples. The flow cytometry (FCM) and direct acridine orange count (DAOC) (epifluorescence microscopy) techniques were employed to evaluate total bacterial counts in planktonic (water) samples. The highest MPN and heterotrophic plate counts were recorded in Week 37 at site B2 at 1.7 x 107 micro-organisms/100 m. and 1.04 x 106micro- organisms/m., respectively. In comparison, the viable FCM counts, were significantly higher (p < 0.05) for that period at 1.7 x 107 micro-organisms/m.. The highest total FCM count of 3.7 x 107 micro-organisms/m. was recorded in Week 41 at Site B2. In comparison the highest DAOC of 8.3 x 106 micro-organisms/m. was obtained in Week 29 at Site B2. Results showed that on average the heterotrophic plate count represented a fraction (< 3.65%) of the total FCM counts. The total DAOC count also represented a fraction (< 43.08%) of the total FCM count for most of the sampling period. Results therefore showed that the FCM proved to be more effective in evaluating microbial pollution in water samples.

Highlights

Water scarcity is becoming a major problem in South Africa, as dams serving communities with drinking water and water for daily household use, have been less than 30% full in recent years (Department of Water Affairs and Forestry (DWAF), 2005)
On average, the most probable number (MPN) counts notably exceeded the maximum limit of 2 000 micro-organisms/100 ml (South African Bureau of Standards, 1984) for river water
The highest overall counts for MPN, heterotrophic counts, direct acridine orange count (DAOC) and flow cytometry (FCM) were observed at Site B2 which is the site where stormwater drainage pipes from the informal settlement discharge into the river

Summary

Introduction

Water scarcity is becoming a major problem in South Africa, as dams serving communities with drinking water and water for daily household use, have been less than 30% full in recent years (Department of Water Affairs and Forestry (DWAF), 2005). In combination with groundwater, is considered a suitable alternative as a utilisable and potable water source. In South Africa, rivers are steadily becoming more contaminated and in some cases even toxic, due in large part, to urbanisation. Communities located in rural and some semiurban areas lack adequate domestic water supplies and wastewater treatment facilities. In many instances sullage and excreta from these informal settlements are discharged into stormwater drainage pipes, which directly flow into nearby rivers. The contaminated river water affects the farms downstream from the pollution source that utilises the water as a means of irrigation

Objectives

Results

Conclusion