Modelling of the fate and emission of carbon disulfide in a full-scale extended aeration process using TOXCHEM simulations

Over the past few decades, odours caused by the emission of carbon disulfide (CS₂) have been a significant problem at wastewater treatment plants. The fate of CS₂, in terms of fate and emissions, was investigated for the Muharram Aisha wastewater treatment plant's (MAWWTP's) extended aeration activated sludge system using the TOXCHEM model. Sensitivity analyses at various aeration levels and mix liquor suspended solid (MLSS) were investigated. The TOXCHEM model was calibrated for the spring and summer seasons and validated for the fall and winter. The results were tested using root mean square error (RMSE) and the correlation coefficient (R) and were found to be within the required limits. The findings indicated that emission and biodegradation were the main system activities. The results showed that in summer (32°C), biodegradation, absorption, emission and treated wastewater values were 33%, 2.6%, 64% and 0.45%, whereas in winter, they were 49%, 4.5%, 45% and 2%, respectively. Emissions from drying beds and aeration tanks represent hot spots and are not environmentally acceptable. Sensitivity analysis results indicated that increasing MLSS concentrations reduce emissions and increase the biological decomposition of carbon disulfide. Finally, the TOXCHEM model was able to accurately forecast the fate and emissions of CS₂ in the extended aeration system.