>
Natural resources are important for the livelihood and survival of populations. One of the most important resources is water, and to be even more specific clean water. The distribution of water serves many purposes, from aquatic ecosystems, domestic use to commercial and industrial use. Clean and safe drinking water can be monitored through microbiological testing. At WETLAB – Western Environmental Testing Laboratory we are proud to offer four certified microbiology analyses and two non-compliance tests. We are certified in Nevada and California to analyze Presence/Absence (P/A), Quanti-tray, Fecal Coliform, and Heterotrophic Plate Count (HPC). The two non-compliance tests we offer are tests to determine Iron Related Bacteria and Sulfate Reducing Bacteria. WETLAB is continuously evolving each department and strives to offer quality data for clients and we encourage method development by researching new tests in order to meet our client needs.
This post is provided to help clients better understand the microbiology analyses at WETLAB. Each test will be described in detail with regards to what we are testing for, what type of sample matrices can be analyzed for certain tests, brief description of the analyses and the hold times for each test (please note there are two different hold times for Quanti-tray). The definition that we follow at WETLAB for sample hold time is the time from sample collection to when analysis MUST begin.
For more information on microbiology analysis, please refer to Standard Methods, Part 9000, Methods 9222 and 9223.
Bacteria Sample Bottle, Volume and Sample Integrity
- Plastic, sterile bottle
- Sample bottle contains sodium thiosulfate.
- Fill to 100 mL line.
- Chill to 2-6o C.
- Cleanliness is required!
SM 9223 B
Presence/Absence (P/A)
Laboratory Hold time (HT)
- P/A = 30 Hour HT
Sample Matrix
- This test is recommended for the analysis of potable drinking water and fresh source waters
Biology Background
- The scope of this test is to analyze for the presence or absence of Total Coliform bacteria and Escherichia Coli. Total Coliform bacteria are abundant in the environment and are easily identified in the laboratory. While these bacteria may not be pathogenic they are used as “indicator bacteria,” for the sanitation of drinking water. If Total Coliform bacteria are present, there is a chance that E.Coli could also be present. Some types of E.Coli can be found in the guts of living organisms as beneficial co-factors in the daily health of that individual. Because E.Coli is found in the gut, the purpose of testing for it is to determine the possibility of fecal contamination, which is used as an indicator for the sanitation of a water source.
Laboratory Analysis
- Tests for Total Coliform and E. coli only.
- Strictly a qualitative result is obtained.
- Used almost exclusively for drinking water.
- 24 hour incubation.
- Incubation temperature, 35.0 + 0.5 oC
- Analysis performed in sample bottle.
- Commercially available chromogenic substrate (ONPG)-known as “Colilert” is used.
- Colilert is used to detect the enzyme b-D-galactosidase, which is produced by total coliform.
- Total coliform detection produces a yellow color.
- Colilert is used to detect the enzyme b-glucuronidase, which is produced by E. coli.
- E. coli detection produces a fluorescent product when viewed under long-wavelength UV light.
SM 9223 B
Quanti-tray (MPN)
Laboratory Hold time (HT)
- Quanti-tray = 30 Hour HT for Drinking water/Source water
- Quanti-tray = 6 Hour HT for Wastewater samples
Sample Matrix
- This test is recommended for the analysis of potable drinking water, fresh source water or wastewaters
Biology Background
- The scope of this test is to analyze for a “most probable number” index of the number of Total Coliform bacteria and Escherichia Coli, present in the sample.. Total Coliform bacteria are abundant in the environment and are easily identified in the laboratory. While these bacteria may not be pathogenic they are used as “indicator bacteria,” for the sanitation of drinking water. If Total Coliform bacteria are present, there is a chance that E.Coli could also be present. Some types of E.Coli can be found in the guts of living organisms as beneficial co-factors in the daily health of that individual. Because E.Coli is found in the gut, the purpose of testing for it is to determine the possibility of fecal contamination, which is used as an indicator for the sanitation of the water source.
Laboratory Analysis
- Tests for Total Coliform and E. coli only.
- Quantitative result is obtained.
- Most commonly used for source water.
- 24 hour incubation.
- Incubation temperature, 35.0 + 0.5 oC
- Uses Colilert just like presence/absence.
- Sample poured into analysis tray, then incubated.
- Count yellow/fluorescent wells in tray, this produces MPN-Most Probable Number result.
SM 9222 D
Fecal Coliform
Laboratory Hold time (HT)
- Fecal Coliform = 8 Hour HT
Sample Matrix
- This test is recommended for the analysis source water, wastewaters and sludge’s.
Biology Background
- The scope of this test is to analyze a direct count of colony forming units of fecal coliform. Fecal coliform can originate in feces (e.g. E.Coli) or non-fecal origin, such as plant materials and paper mill effluents examples of bacteria are Enterobacter, Klebsiella, Citrobacter. The assay is intended to detect E. Coli as an indicator organism for fecal contamination.
Laboratory Analysis
- Tests for fecal contamination in water.
- Quantitative result is obtained.
- Most commonly used for waste water and surface water.
- 24 hour incubation in water bath.
- Incubation temperature, 44.5. + 0.2 oC
- Sample is filtered (0.45 mm), microorganisms collect on filter and grow due to media used in petri dish.
- Count blue colonies.
SM 9215 B / SimPlate
HETEROTROPHIC PLATE COUNT (HPC)
Laboratory Hold time (HT)
- HPC = 8 Hour HT
Sample Matrix
- This test is recommended for the analysis of potable drinking water, fresh source water or wastewaters.
Biology Background
- Heterotrophic bacteria, must consume carbon sources for energy and growth. They are found prevalent in the environment as decomposing bacteria as well as being normal flora of the human body. Current research is investigating the use of Heterotrophic bacteria testing for similar purposes as P/A and Fecal Coliform, to evaluate the composition of the water, using Heterotrophic bacteria as the “indicator” organism for possible contamination in water.
Laboratory Analysis
- Tests for Heterotrophic bacteria
- Quantitative result is obtained.
- Most commonly used for drinking water.
- 48 hour incubation.
- Incubation temperature, 35.0 + 0.5 oC
- Uses IDEXX’s Multiple Enzyme Technology media.
- Sample poured into analysis tray, then incubated.
- Count blue fluorescence, this produces MPN-Most Probable Number result.
SM 9240 B
Iron Related Bacteria (IRB)
SM 9240 C
Sulfate Reducing Bacteria (SRB)
Laboratory Hold time (HT)
- IRB/SRB = WETLAB would prefer to use a hold time of 30 Hours
Sample Matrix
- This test is recommended for the analysis of treated water, distribution systems and water used in for industrial use, such as cooling and boiler waters.
Biology Background
- The scope of these tests are very similar, hence the reason they have been grouped together. The metabolic processes of Iron Bacteria and Sulfur Bacteria chemically change the constituents they are associated with. The metabolic wastes can be bothersome because they can form slimes that clog pipelines or affect the aesthetic properties of water.
Laboratory Analysis
- Tests for either Iron Related Bacteria or Sulfate Reducing Bacteria
- Strictly a qualitative result is obtained.
- Most commonly used for water used for industrial and distribution systems.
- 8 Day incubation.
- Incubation temperature, 20-25oC
- Uses BARTTM test kit for IRB or SRB analysis
- Sample poured into analysis tray, then incubated.
- Visually inspect for reactions of presence/absence.
