Physical Address
304 North Cardinal St.
Dorchester Center, MA 02124
D4201-96 – Standard Test Method Technical Guide
The ASTM D4201-96 standard specifies a test method for the determination of coliphages infective for E. coli C in water. This method is simple, inexpensive, and provides rapid water quality data with a sensitivity of 5 coliphages per 100 mL of sample. It is applicable to natural fresh water samples.
🔬 Scope and Terminology
This test method covers the determination of coliphages in natural fresh water. A coliphage is defined as a bacterial virus capable of replication using E. coli C as a host. A bacterial lawn refers to confluent growth of bacteria. For comprehensive definitions, refer to Terminology D1129.
⚙️ Test Method Summary and Apparatus
The test procedure involves adding a measured water sample to melted modified nutrient agar, inoculating with E. coli C host culture, mixing, and pouring into a petri dish. Incubation at 35°C allows coliphages to lyse bacteria and form plaques, which are counted to determine the number of coliphages in the sample.
Required apparatus includes a water bath at 44.5 ± 0.2°C, an incubator at 35 ± 0.5°C, sterile petri dishes (100 x 15 mm), and sterile pipets (1-mL and 5-mL).
| 🟦 Equipment | 📏 Specification |
|---|---|
| Water Bath | 44.5 ± 0.2°C |
| Incubator | 35 ± 0.5°C |
| Petri Dishes | 100 x 15 mm, sterile |
| Pipets | 1-mL and 5-mL, sterile |
| 📐 Parameter | 🎯 Requirement |
|---|---|
| Sample Volume | Measured water sample |
| Agar Medium | Modified nutrient agar |
| Host Culture | E. coli C |
| Incubation Temperature | 35°C |
| Detection Limit | 5 coliphages per 100 mL |
📊 Significance and Interpretation
Coliphages serve as indicators of fecal pollution. Their presence in water without a disinfectant suggests fecal contamination, but the exact relationship with coliform numbers is not conclusive. The test can detect coliphages in 4 to 6 hours, providing same-day information on sanitary quality.
Interferences include high salt concentrations from saline or brackish waters, which inhibit plaque formation. In disinfected waters, the relationship between coliphages and coliforms differs due to varying survival rates; coliphages may be more resistant to chlorine.
⚠️ High salt concentrations, such as those in saline or brackish water, can interfere with plaque formation and should be avoided.
💡 This test provides rapid results in 4 to 6 hours, enabling same-day water quality assessment.
❓ Frequently Asked Questions
🔍 What is a coliphage?
A coliphage is a bacterial virus that uses E. coli C as a host and serves as an indicator of fecal pollution.
💡 How does the coliphage test work?
A water sample is mixed with melted agar and E. coli C, incubated, and plaques formed are counted to quantify coliphages.
⚡ What is the detection limit?
The test can detect as few as 5 coliphages per 100 mL of water sample.
📌 What samples are suitable for this test?
Natural fresh water samples are suitable, but saline or brackish waters may cause interference.