How to determine the concentration of coliform bacteria in water? This requires the use of the WECT-900 Online Coliform Analyzer to analyze coliform bacteria in water, thereby quantifying their abundance. What are the procedures involved in the entire monitoring process? This chapter provides a brief overview. Due to the unique characteristics of bacteria, coliform monitoring differs from the detection of other pollutants. The specific operation involves the following steps:
1.Sampling and Dilution
For sample preparation, aseptic techniques are employed to transfer the test sample into a sterile water Erlenmeyer flask or a sterilized mortar. Thorough shaking or grinding is then performed to prepare a 1:10 dilution. For solid samples, a sterile homogenizer and centrifugation at a specified speed are used to obtain the 1:10 dilution. Next, a 1:10 dilution aliquot is drawn with a sterile pipette and transferred to a 9 mL sterile water test tube; after shaking to mix uniformly, a 1:100 dilution is prepared. Serial dilutions are continued using the same method to generate a series of multi-fold dilutions.
2.Preliminary Lactose Fermentation Test (Presumptive Test)
This test aims to detect the presence of bacteria capable of fermenting lactose to produce gas. The procedure involves inoculating the test sample into lactose bile salt fermentation tubes: for inoculum volumes exceeding 1 mL, double-strength lactose bile salt fermentation tubes are used; for volumes ≤ 1 mL, single-strength tubes are employed. During incubation, if no gas production is observed in all lactose bile salt fermentation tubes, the coliform result is reported as negative. If gas is produced, subsequent steps are required.
3.Isolation and Cultivation
Following the above steps, gas-producing fermentation tubes are streaked onto Eosin Methylene Blue (EMB) agar plates, which are then incubated at a specified temperature. After incubation, colony morphology is observed, followed by Gram staining, microscopic examination, and a re-fermentation test.
4.Lactose Re-Fermentation Test
This test verifies whether Gram-negative, non-spore-forming bacilli isolated from tubes positive in the preliminary fermentation test can ferment lactose to produce gas. Specifically, if lactose fermentation yields gas and Gram staining is negative (for non-spore-forming bacilli), the coliform result is reported as positive. Conversely, if no gas is produced during lactose fermentation or Gram staining is positive, the result is negative.
The WECT-900 Online Coliform Analyzer mentioned herein is primarily applied in medical wastewater monitoring, but it may also be used in other industries depending on specific water quality conditions.
