| NTU | Nephelometric Turbidity Unit |
| ISO | International Organization for Standardization |
| FNU | Formazin Nephelometric Unit |
| FTU | Formazin Turbidity Unit |
| GRIN | gradient index |
Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.