IDENTIFICATION AND MEASUREMENT OF FOOD AND COSMETIC DYES IN A MUNICIPAL WASTE-WATER TREATMENT-PLANT

Acid Blue 9, Acid Violet 17, Quinoline Yellow, Acid Red 51, Acid Red 87, and Acid Red 92 along with N-benzyl-N-ethylaniline sulfonic acid (BEASA), a synthetic precursor, were identified and measured in colored wastewater samples from a municipal treatment plant. Continuous-flow fast-atom bombardment mass spectrometry was used to analyze BEASA. Liquid chromatography with ultraviolet detection was used to analyze the other dyes, but its lack of selectivity required prior isolation of the analytes from interfering compounds by solid-phase extraction onto C18 extraction disks and onto cartridges packed with strong anion-exchange resins. The xanthene dyes (Acid Red 51, 87, and 92) were found in low parts per billion (ppb) concentrations in the plant influent and were rapidly removed by adsorption to sludge. Acid Red 92 was found to be over 35 times more concentrated on secondary sludge than in the corresponding liquid samples, indicating high levels of accumulation. The other dyes and BEASA were found in hundred ppb concentrations in both the influent and the effluent of the plant, indicating a resistance to both degradation and removal by sorption.