A standard EPA-accepted or approved chemical oxygen demand (COD) test is required for EPA reporting, but a more rapid and mercury-free method is available for testing influent streams when reporting is not required. Taking about 2 hours, a standard micro-COD test measures contaminants that can be readily oxidized. A 2.5-mL sample is placed in a twist tube with pre-measured reagent, digested for 2 hours at 150 C, and read in an inexpensive colorimeter. The quick variation substitutes a mercury-free reagent, which permits simpler and cheaper disposal, while shortening the digestion time to 15 minutes. The colorimeter microprocessor selects low or standard COD range, displays the test sequence, and indicates results in ppm. It displays the appropriate built-in light filter to match one of 40 programmed test parameters. The device also indicates the percentage of light transmittance and absorption, so users can develop calibration curves for analyses. The system uses the same or twist tubes similar to the EPA-approved accu-TEST COD method, which requires a spectrophotometer to conform to EPA Method 410.4.