4-Log Viral Inactivation

What is?

When Required

What to do When 4-Log Viral Inactivation is Required

Are There Special Requirements After 4-Log Viral Inactivation is Met?

Assistance

What is 4-Log Viral Inactivation?

Removal/inactivation of 99.99% of viruses through filtration and/or disinfection.

When is 4-Log Viral Inactivation Required?

For a total coliform positive well sample:
- If more than 10 percent of the samples of the 20 sample well survey come back positive, or if either of the last two samples are positive, the well will be deemed susceptible to microbial contamination and the water system will have to submit documentation that the water treatment plant meets 4-log viral inactivation.
For an E. coli positive well sample:
- 4-log viral inactivation may be required after an assessment well sample is E. coli positive and any of the follow up repeat samples are also E. coli positive. If all other corrective actions have been explored, the Department may decide that 4-log inactivation is required. If any well survey samples are E. coli positive, the well will be deemed susceptible to microbial contamination and the water system will have to submit documentation that the water treatment plant meets 4-log viral inactivation.

What to do when 4-Log Viral Inactivation is Required?

Retain the services of a professional engineer Licensed in the State of Florida.
Your engineer will analyze your water system and will submit CT calculations to the Department in accordance with Rule 62-555.320(12)(b) and (c).
- Direct all submittals and questions to Richard S. Lott, P.E. P.G. by email at Richard.Lott@dep.state.fl.us or by phone at 407-897-4122.
The Drinking Water Permitting section will review the calculations to determine if sufficient CT is provided.
- If sufficient CT is provided, no changes will need to be made to the water system.
- If CT is deemed to be insufficient, a permit to modify the drinking water treatment plant must be obtained.

*Note: CT is a parameter that is obtained by multiplying the disinfectant residual by the water's detention time before or at the first customer. It does not mean "contact time."

Are There Special Requirements after 4-Log Viral Inactivation is Met?

You must also complete columns 6-11 on the Monthly Operation Reports (MORs) for each day that the plant serves water to the public.
Your 4-log acceptance letter will contain minimum free chlorine levels that must be maintained before or at the first customer.