Recommended Microbial Water Testing for Aquaponic Farms
To minimize the risk of food safety outbreaks, it is important for hydroponic farms to test their water for microbial contamination periodically. Periodic water testing can help identify areas of potential contamination and allow farms to take the necessary steps to ensure their water is safe for use.
Types of Microbial Testing
There are a variety of types of microbial testing that can be done on water, including:
- Total Coliform Bacteria: These bacteria are found in the environment and can indicate the presence of other potentially dangerous bacteria.
- E. coli: This type of bacteria indicates fecal contamination and can cause serious illness if consumed.
- Heterotrophic Plate Count: This test measures the number of bacteria in the water, indicating the presence of pathogens.
- Enterococcus: This type of bacteria can indicate the presence of other potentially dangerous bacteria and can cause serious illness if consumed.
FDA Produce Safety Rules
The FDA Produce Safety Rule states water used for irrigation purposes that are likely to come into contact with the edible portion the fruit and vegetables must not exceed a defined limit of Escherichia coli in the water.
It requires a geometric mean (GM) and a statistical threshold (STV) of 126 or less and 410 CFU or less of generic E. coli/100 mL of irrigation water, respectively.
Even though aquaponics has not been included in this guideline, it creates a baseline for aquaponic facilities to reference if monitoring the water.
Maximum Concentration of Microbial Levels Permitted in US Hydroponics
| Microbe | Maximum Concentration (CFU/ml) | Course of Action |
|---|---|---|
| Total Coliform Bacteria | 1,000 | A more appropriate test would be to test for generic e.coli. |
if you have a total coliform test>99 cfu / 100 ml in leafy green production it is recommended by the Arizona leafy greens food safety committee that you submit the sample for a generic E coli test. Refer to farm food safety plan; one example may be to, wash and sanitize produce, and add a treatment to the water to reduce the concentration of E.coli |
Here are a couple of additional resources for your reference.
- https://www.fda.gov/food/food-safety-modernization-act-fsma/fsma-final-rule-produce-safety
- https://www.mdpi.com/2311-7524/6/3/42/pdf&ved=2ahUKEwjh-sjS9ND1AhV8m2oFHf8iAGEQFnoECAsQAQ&usg=AOvVaw07suPOfhQMXqrjxOdGCfJX
Frequency of Microbial Testing
Due to the nature of microbial secession in an aquaponic system, the concentration of microbes of concern can change drastically over a 24- period; therefore, long periods of waiting between testing may result in a missed positive. Alternatively, testing frequently can result in high test costs which may not be feasible for the farm.
Unless you have a specific prevention protocol in your HACCP plan, as a rule of thumb to minimize the risk of food safety outbreaks, we recommend that hydroponic farms test their water at the time of harvest or at least once a month. This will help identify potential contamination and allow farms to take the necessary steps to ensure their water is safe.
Some choose to test only as needed and operate the systems under the assumption that if nothing is wrong, then not to test, aka. “ignorance is bliss.” We can’t force you one way or another; at the end of the day, you are your business owner.
Conclusion
By regularly testing their water, hydroponic farms can minimize the risk of food safety outbreaks and ensure the safety of their crops.