چكيده به لاتين
Although anaerobic digestion technology is not new and has been commercialized since the early 1980s, statistics show that it is still underutilized for energy recovery. The reason for this is the insufficient methane production, which can be rooted in operational issues and process instability. Several factors affect the performance of anaerobic digestion, and optimizing these factors can improve process efficiency and maximize biogas production. Many studies have been conducted in this field, mostly at the laboratory scale, focusing only on investigating the effect of parameters within the anaerobic digester itself, such as temperature, alkalinity, pH, loading rate, and similar factors. However, the conditions inside the digester are influenced by the conditions outside the digester, meaning the performance of upstream process units before digestion. For example, the quality and quantity of the feedstock entering the digester, the performance and efficiency of primary and secondary settling tanks, and even the quality and quantity of the raw wastewater entering the treatment plant are factors that control the conditions inside the digester. For this reason, the present study focuses on statistically examining the correlation and interdependence of quantitative and qualitative parameters of processes preceding anaerobic digestion with the biogas output from the digester, in the form of three different scenarios. In the first scenario, the parameters of the influent feedstock to the treatment plant are considered. In this scenario, the TSS, BOD5, and COD loading of the influent to the treatment plant showed the highest correlation coefficients of 0.66, 0.77, and 0.73, respectively, with the biogas output from the digester. In the second scenario, the parameters of the settling tanks are examined. The results of the primary settling tank indicated the highest correlation between the digester biogas production and the concentration and Load of removal BOD5 during primary settling, with monthly Pearson correlation coefficients of 0.67 and 0.51 respectively. In the secondary settling tank, the digester biogas production showed a relatively high correlation with the MLSS and MLVSS loading from the secondary settling tank, with Pearson correlation coefficients of 0.41 and 0.46, respectively. In the third scenario, the influential parameters in the feedstock entering the digester are investigated. The dry solids content of the sludge from primary settling tank after thickening, the dry solids content of the sludge from the secondary settling tank after thickening, the average weight of the feedstock solids, and the organic mass loading from primary settling tank to the digester showed the highest correlation with the digester biogas output, with monthly Pearson correlation coefficients of 0.66, 0.54, 0.59 and 0.65, respectively. Overall, the results indicate that the characteristics of the influent wastewater to the treatment plant and the characteristics of the feedstock entering the digester (output of sludge thickening units) have the greatest influence on the performance of anaerobic digestion and the amount of biogas produced.
