The Importance of Using Standardized Microbiological Methods to Monitor Water Quality in California
- joe15219
- Oct 31
- 4 min read
Clean and safe water is fundamental to public health, environmental protection, and California’s economy. Whether it’s drinking water drawn from Sierra Nevada reservoirs, treated wastewater discharged to coastal waters, or stormwater runoff entering local creeks, microbiological testing plays a crucial role in evaluating water safety and regulatory compliance.
At Aquatic Bioassay & Consulting Laboratories, Inc., we perform microbiological analyses using Standard Methods for the Examination of Water and Wastewater (SM) the most widely recognized analytical protocols for water testing worldwide. These methods provide consistency, comparability, and reliability across projects, agencies, and laboratories, ensuring that decisions made on water quality are based on trustworthy data.
Standardized Methods Used in Microbiological Testing
Our laboratory utilizes two major testing technologies — IDEXX enzyme-based detection and the Multiple Tube Technique (MTT) — to quantify indicator organisms that reflect the sanitary quality of water.
Parameter | Technology | Method Reference | Holding Time | Temperature |
Total Coliform | IDEXX | SM 9223 B | 6 hours | 4°C |
Escherichia coli | IDEXX | SM 9223 B | 6 hours | 4°C |
Enterococcus | IDEXX | SM 9230 B | 6 hours | 4°C |
Total Coliform | Multiple Tube Technique | SM 9221 B6 | 6 hours | 4°C |
Fecal Coliform | Multiple Tube Technique | SM 9221 F6 | 6 hours | 4°C |
Enterococcus | Multiple Tube Technique | SM 9230 B6 | 6 hours | 4°C |
These approved methods are used for compliance monitoring under various programs, including:
NPDES (National Pollutant Discharge Elimination System) permit testing for wastewater treatment plants and industrial dischargers
Stormwater monitoring for municipal and construction permits
Recreational water quality assessments at beaches, lakes, and rivers
Drinking water testing for public water systems
Groundwater and reclaimed water evaluations for reuse under Title 22
Understanding the Indicator Organisms
Total Coliform
Total coliform bacteria are a broad group naturally found in the environment. While not all are harmful, their presence in treated water can indicate possible contamination or inadequate disinfection. Testing for total coliform is a key component of both drinking water safety assessments and wastewater treatment performance evaluations.
Example: Monitoring treated effluent from a municipal wastewater treatment plant before it’s discharged to a river under an NPDES permit.
Escherichia coli (E. coli)
A specific type of coliform bacteria that originates from the intestinal tract of warm-blooded animals. Its presence confirms fecal contamination and possible presence of pathogens.
Example: Testing stormwater outfalls in urban areas where pet waste or sewage leaks may enter the drainage system.
Enterococcus
These bacteria are used as indicators of fecal pollution in marine and freshwater recreational waters. Enterococcus testing is a requirement for many beach monitoring programs throughout coastal California.
Example: Routine testing at beaches in Ventura and Orange Counties to ensure public health protection under the California Ocean Plan.
Fecal Coliform
Traditionally used in monitoring treated wastewater and shellfish-growing waters, fecal coliform testing provides an additional layer of confirmation for fecal contamination.
Example: Testing effluent from a coastal wastewater facility that discharges into an estuary used for aquaculture.
The Technologies: IDEXX vs. Multiple Tube Technique
IDEXX Enzyme-Based Methods (SM 9223 B & SM 9230 B)
IDEXX methods, such as Colilert® and Enterolert®, utilize defined enzyme substrates that produce a color change or fluorescence when specific bacteria are present. These tests are rapid, precise, and ideal for large-volume routine monitoring.
Advantages:
Results typically within 24 hours
High specificity for target bacteria
Quantitative results (Most Probable Number, MPN)
Minimal sample handling and reduced contamination risk
Common Uses:
Drinking water compliance monitoring by public utilities
Routine monitoring of stormwater retention ponds
NPDES compliance testing for secondary effluent
Multiple Tube Technique (SM 9221 & SM 9230)
The Multiple Tube Technique is one of the oldest and most reliable microbiological testing procedures. It involves inoculating a series of culture tubes with serial dilutions of a sample and incubating them to detect bacterial growth.
Advantages:
Proven, regulatory-accepted method
Effective for complex matrices or highly turbid samples
Useful for confirmatory or backup testing
Common Uses:
Wastewater and industrial effluent testing under NPDES
Recycled water and Title 22 reuse monitoring
Validation of enzyme-based test results
The Critical Role of Holding Time and Temperature
Even when the correct analytical method is used, proper sample preservation is essential for accurate microbiological analysis.
Holding Time: Samples must be analyzed within 6 hours of collection. Delays can allow bacteria to multiply or die, leading to erroneous results and potential regulatory violations.
Temperature: Samples must be maintained at 4°C during transport. Cooling slows biological activity, keeping the microbial population stable between collection and testing.
For example, a stormwater grab sample collected during a rainfall event in Los Angeles must be promptly placed on ice and delivered to the lab the same day to maintain compliance with California’s General Permit for Stormwater Discharges.
Regulatory Compliance and Public Health Protection
Microbiological monitoring using approved Standard Methods is required by several California and federal programs, including:
California NPDES Program (Clean Water Act Section 402)
Title 22 Recycled Water Quality Standards
Safe Drinking Water Act
California Ocean Plan for coastal water quality monitoring
ELAP Accreditation Requirements for certified laboratories
By following these standardized testing protocols, Aquatic Bioassay ensures that results are scientifically defensible, traceable, and accepted by regulatory agencies at every level.
Commitment to Quality and Environmental Stewardship
At Aquatic Bioassay & Consulting Laboratories, Inc., we uphold the highest standards of microbiological testing by strictly following SM 9223 B, SM 9221 B6, SM 9221 F6, and SM 9230 B6 methods and adhering to prescribed holding times and temperature requirements. Our laboratory provides accurate and timely microbiological data to help municipalities, environmental consultants, and regulatory agencies make informed decisions about water quality management.
Whether ensuring the safety of California’s drinking water supplies, protecting swimmers at coastal beaches, or supporting wastewater treatment plant compliance, our goal remains the same — to protect public health and the environment through precise, accredited, and dependable laboratory science.
Contact us more information or assistance Bioassay testing in California
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