Does the APHA color method correlate to a Standard Method or something similar?
Hach APHA method and Standard Methods
There is no direct Standard Method or EPA method to which the Hach APHA corresponds. It is closest to the visual comparison method and the wavelength 455nm has been traditionally used for measurement with a colorimeter or spectrophotometer. Methods using a wavelength of 465nm are used by the pulp and paper industry.