Environmental Surveillance Laboratory


Capabilities and Certification

Capabilities The DEQ laboratory tests several biological and chemical parameters in drinking, recreational, and other source waters.

Biological parameters include: Total Coliforms, Escherichia Coli, Fecal Coliforms and, Enterococci. Chemical parameters include: pH, Turbidity, Conductivity, Chlorides, Hardness, Residual chlorine (free), Temperature, Total Dissolved Solids, Total Suspended Solids and Nitrate.

Certification Status All Drinking Water Certified Laboratories, including the DEQ laboratory Program must be Fully Certified by the Environmental Protection Agency (EPA) Region 9, in order for the laboratory to carry out its tasks in analyzing drinking water in the CNMI. The DEQ laboratory is currently certified for bacteriological analysis using the ONPG – MUG (Colilert 18) method.

About Colilert 18 method... Colilert-18 is used for the simultaneous detection and confirmation of total coliforms and E. coli in water.

The test is based upon the ability of coliforms to produce the enzyme B-galactosidase which cleaves the media substrate O-nitrophenyl-B-d-galactopyranoside (ONPG) producing a yellow color from the release of O-nitrophenyl. In addition, the enzyme B-glucuronidase produced by E. coli forms a fluorescent substance when it hydrolyses 4-methylumbelliferyl-B-d-glucuronide (MUG).

This combination of substrates allows detection of both total coliforms and E. coli within 18 hours. According to the manufacturer, Colilert-18 can detect 1 colony forming unit (CFU) per100ml with as many as 2 million heterotrophic bacteria/100ml present.