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 Colilert -18) method - Total Coliform and E. Coli and EPA 353.2 method - Nitrate and Nitrite as N, Nitrate as N, Nitrite as N.

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.

EPA 353.2 Method -  Nitrate and Nitrite as N, Nitrate as N, Nitrite as N is use to determine Nitrate + Nitrite as N in drinking water, surface water and waste water.  The Nitrate is quantitatively reduced by passage of the sample through a copperized cadmium column.  The nitrite (reduced nitrate plus original nitrite is then determined by diazotizing with sulfanilamide followed by coupling with N(1-napthyl) ethylenediamine dihydrochloride.  The resulting water soluble dye ha a magenta color which is read at 520 nm.  Nitrite alone also can de determined by removing the cadmium column.