Abstract

PIRE SIERRA, María Carolina et al. BIODEGRADABILITY OF DIFFERENT FRACTIONS OF WASTEWATER PRODUCED IN A TANNERY. Cienc. Ing. Neogranad. [online]. 2011, vol.21, n.2, pp.5-19. ISSN 0124-8170.

Tannery wastewater is composed by organic components with different biodegradability levels, so it is important to know its biodegradable and inert contents to select the most appropriate treatments. The organic matter fractionation, measured as chemical oxygen demand (COD), allowed to detect the contents of a readily biodegradable COD (rbCOD), slowly biodegradable COD (sbCOD), soluble inert COD (siCOD) and particulate inert COD (piCOD), contained in three types of tannery effluents produced (dyed-soak liquor mixture, dyed-tanning mixture, and pond-stored effluent). The goal of this research was to select the best effluent based on its biodegradability and propose the most appropriate purification treatments. For this investigation a 2L-batch reactor of mixed liquor was used with 70% industrial effluent and 30% biomass. The system remained aerated during the cycle (24 h). Total and soluble COD were measured for raw wastewater and mixed liquor at the beginning and end of the process. The effluent with the highest content of biodegradable COD was the mixture effluent stored in the pond with 57.4%, formed by 33.1% rbCOD and 24.3% sbCOD, whereas the segregated mixtures showed a lesser biodegradable COD (35.8 and 34.0%, respectively). Therefore, the COD fractionation showed that a biological treatment would be more effective to treat the effluent stored in the pond, reaching 57.4% biological removal of COD. Also, results showed a post-treatment is required to remove the colloidal part from a non-biodegradable fraction (29.0% siCOD and 13.6% piCOD).

Keywords : organic matter; biodegradable COD; inert COD; tannery.

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