Assessment of COD fractions in Beja domestic sewage mixed with baker’s yeast factory effluent using respirometric technique

The necessity of our research stems from the substantial environmental implications of baker’s yeast wastewaters (BYW), which pose risks to both human health and aquatic ecosystems due to their high COD, low pH, strong odor, and dark coloration. To address these challenges, we employed an innovative respirometric method to assess the COD fractions of domestic sewage mixed with baker’s yeast factory effluent at the Beja domestic wastewater treatment plant (WWTP). Our original investigation involved conducting three respirometric runs in a closed tank reactor to characterize the raw mixed effluent, with total COD (TCOD) ranging from 564 ± 60 to 890 ± 100 mg O₂/L. The respirometric experiments revealed that the readily biodegradable fraction (S_S) ranged between 6 and 22%, the slowly biodegradable fraction (Xs) ranged from 33 to 42%, the heterotrophic biomass (X_H) ranged from 9 to 40%, and the inert fractions (X_I) and (S_I) ranged from 2 to 40% and 6 to 12% respectively. In terms of nitrogen fractions, the study revealed that the S_NO fraction, comprising nitrates and nitrites, accounted for 6–9% of the total Kjeldahl nitrogen (TK-N). The ammonia nitrogen (S_NH) fraction exhibited a wide range, from 5 to 68%. The organic nitrogen was divided into soluble organic nitrogen (S_ND) and particulate organic nitrogen (X_ND), with S_ND ranging from 11 to 85% and X_ND ranging from 5 to 20%. The inert particulate nitrogen fraction (X_NI) and inert soluble nitrogen fraction (S_NI) were relatively low, ranging from 0.4 to 1% and 0.4 to 3%, respectively. These findings are pivotal as they illuminate the composition and characteristics of mixed effluents, offering valuable guidance for addressing challenges in their treatment. In terms of environmental integration, this research can significantly improve the treatment of mixed effluents, thereby mitigating the environmental impact of baker’s yeast wastewaters. Furthermore, this study underscores the importance of assessing and optimizing treatment strategies for domestic wastewater effluents mixed with baker’s yeast factory effluent.