Laboratory testing is the gold standard for ensuring drinking water safety, providing precise analysis of contaminants that portable kits cannot detect. This guide explores the essential parameters tested in labs, compliant methods (ISO, EPA), and technologies to meet regulatory requirements for public health protection.
1. Microbial Contaminants
- Parameters:
- E. coli, Total Coliforms (ISO 9308-1).
- Legionella (ISO 11731).
- Methods:
- Membrane Filtration (EPA Method 1603).
- PCR (Polymerase Chain Reaction) for rapid pathogen detection.
2. Heavy Metals
- Key Metals:
- Lead (Pb): EPA MCL = 15 ppb.
- Arsenic (As): WHO limit = 10 ppb.
- Mercury (Hg): EPA MCL = 2 ppb.
- Methods:
- ICP-MS (ISO 17294-2 for trace metals).
- Graphite Furnace AAS (EPA Method 200.9).
3. Disinfection Byproducts (DBPs)
- Parameters:
- Trihalomethanes (THMs): EPA MCL = 80 ppb.
- Haloacetic Acids (HAAs): EPA MCL = 60 ppb.
- Methods:
- GC-ECD (EPA Method 551.1).
- Purge-and-Trap GC-MS (EPA Method 524.2).
4. Nitrates and Nitrites
- Health Risk: Methemoglobinemia in infants.
- Regulatory Limits:
- Nitrates (NO₃⁻): 10 mg/L (EPA/WHO).
- Nitrites (NO₂⁻): 1 mg/L (EPA).
- Methods:
- Ion Chromatography (ISO 10304-1).
- Cadmium Reduction (EPA Method 353.2).
5. Organic Chemicals
- Parameters:
- Pesticides (Atrazine, Glyphosate): EPA MCL = 0.003–0.7 mg/L.
- PFAS (Perfluorinated Compounds): EPA Health Advisory = 0.004–0.02 ppt.
- Methods:
- LC-MS/MS (EPA Method 537.1 for PFAS).
- HPLC (EPA Method 531.1 for carbamates).
6. Physical-Chemical Parameters
- Key Tests:
- Turbidity: <0.3 NTU (EPA Method 180.1).
- pH: 6.5–8.5 (ISO 10523).
- Conductivity: <500 µS/cm (ISO 7888).
| Standard | Scope | Key Parameters |
| ISO 5667-3:2018 | Sampling guidance for drinking water | Metals, organics, microbes |
| EPA 500 Series Methods | U.S. compliance protocols for contaminants | DBPs, pesticides, nitrates |
| WHO Guidelines (2021) | Global health-based limits | Lead, arsenic, E. coli |
| EU Directive 2020/2184 | Europe’s updated water safety rules | PFAS, microplastics, Legionella |
1. ICP-MS (Inductively Coupled Plasma Mass Spectrometry)
- Use: Detects trace metals (lead, arsenic) at ppt levels.
- Compliance: ISO 17294-2, EPA Method 200.8.
2. GC-MS (Gas Chromatography-Mass Spectrometry)
- Use: Analyzes volatile organics (THMs, pesticides).
- Compliance: EPA Method 524.2, ISO 15680.
3. Automated Microbial Analyzers
- Use: Rapid E. coli and coliform enumeration.
- Compliance: ISO 9308-1, EPA Method 1604.
4. Ion Chromatographs
- Use: Measures anions (nitrates, sulfates).
- Compliance: ISO 10304-1, EPA Method 300.0.
1. Sample Collection:
- Use sterile, pre-treated bottles (ISO 5667-3).
- Preserve samples with HNO₃ (metals) or Na₂S₂O₃ (chlorine neutralization).
2. Preparation:
- Filter samples (0.45 µm membrane) for microbial/particulate removal.
3. Analysis:
- Run spikes/replicates for QA/QC (EPA Requirements).
4. Reporting:
- Compare results to WHO/EPA limits using LIMS (Lab Information Management Systems).
- Challenge: Lead exceedances in aging infrastructure.
- Solution:
- Adopted ICP-MS (EPA 200.8) for 10x lower detection limits.
- Implemented 24-hour turnaround for lead testing.
- Result: Lead violations reduced by 85% in 2 years.
Routine laboratory testing for microbial, chemical, and physical parameters is non-negotiable for drinking water safety. By adhering to ISO, EPA, and WHO standards—and leveraging advanced tools like ICP-MS and GC-MS—labs can ensure regulatory compliance, protect public health, and build trust.
