Determination of the level of hexavalent, trivalent, and total chromium in the discharged effluent of Bahir Dar tannery using ICP-OES and UV–Visible spectrometry

Abstract

Tanneries that employ chrome tanning are indicted for discharging their effluents contaminated with health hazard chromium species necessitating monitoring their levels. The levels of chromium species (total chromium, hexavalent chromium, and trivalent chromium) in the discharged effluent of Bahir Dar tannery, Ethiopia, were determined using the inductively coupled plasma optical emission spectrometry, ultra-violet spectrometry and by difference, respectively. The level of total chromium in the discharged tannery effluent sample collected before and after treatment was 82.40 ± 0.20 ppm and 2.96 ± 0.06 ppm, respectively showing that the total chromium concentration in the tannery waste discharged directly to the Blue Nile river water system is above the national permitted limit (2 ppm). Moreover, the concentration of the carcinogenic chromium species (hexavalent chromium) detected in the tannery effluent sample collected before and after treatment was 0.18 ± 0.01 and 0.08 ± 0.002 ppm, respectively indicating that the discharged tannery effluent adds the carcinogenic chromium species to the Blue Nile River in a level above the recommended level by WHO guidelines. The result necessitates the assessment of the level of chromium species in the discharged effluent of all the tanneries in the country.