12VAC5-613-80. Performance requirements; general.

1.        Change section 6. per below:

“6. Dosing of Wastewater entering the treatment unit or treatment system shall accommodate be dosed in a manner that does not exceed the design demonstrated peak flow volume in gallons and the demonstrated instantaneous flow rate in gallons per minute within the treatment unit's rated instantaneous dose and daily capacity;”

Reason: Numerous studies documenting field performance have shown that some treatment units do not perform in the field as well as in a test center.  The main reasons for this are the inconsistency in the dosing method, both in rate and in volume, and the lack of routine service by competent professionals.  Since a treatment unit is often used on a marginal site, the unit’s performance is crucial to protecting the public health and the environment.  The way to remedy this is to require designers to justify the treatment unit incoming instantaneous dose rate and dose volume.  This, in addition to the daily design volume and routine service requirement, will ensure the adequacy of treatment. NSF Standard 40 makes the following statement on influent dosing regimen:

8.2.2.1 Design loading note:
NOTE – The individual dosage shall be no more than 10 gallons per dose, unless the dosage system is based
on a continuous flow, and be uniformly applied over the dosing periods.