Effects of anaerobic pre-treatment on the degradation of dewatered-sewage sludge

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• 作者：Ivo Achu Nges ; Jing Liu
• 关键词：Anaerobic digestion ; Mesophilic ; Methane yield ; Pre-treatment ; Thermophilic ; VS-reduction
• 刊名：Renewable Energy
• 出版年：2009
• 出版时间：July 2009
• 年：2009
• 卷：34
• 期：7
• 页码：1795-1800
• 全文大小：369 K

文摘

Effects of anaerobic pre-treatment were evaluated on the dewatered-sewage sludge from a municipal wastewater treatment plant in order to improve its biodegradability through anaerobic digestion. The pre-treatment was conducted in laboratory scale at 25, 50 and 70 °C for an incubation time of two days. As a reference, sludge sample was also autoclaved at 121 °C for 20 min to determine the thermal effect to the subsequent sludge digestion. Characteristics of dewatered-sludge such as viscosity, pH and soluble chemical oxygen demand (SCOD) were affected by the pre-treatment. A higher SCOD after the pre-treatment did not necessarily imply an increase in methane yield, although initial biodegradability rate was improved. In fact, a ‘great’ improvement in SCOD concentration (up to 27 % ) was translated in only 8 % increase in the methane yield (298 ± 9 and 276 ± 6 Nml CH₄ gVS_added⁻¹ for pre-treated and untreated samples, respectively). Increasing the anaerobic pre-treatment time from 12 h to 2 days at 50 °C led to an 11 % improvement in methane yield. Methane content in biogas increased from an average of 65–69 % for the pre-treated and untreated substrates, respectively. Volatile solids (VS) reduction increased from 42 % to 51 % . The overall digestion time was not affected by the pre-treatment but 90 % of methane was produced in the first 12 days of incubation for 50 °C pre-treated samples whereas it took 2–5 days more for 25, 70 °C pre-treated and untreated sludge samples. In this study, thermophilic digestion was also found to be a better option in terms of faster digestion and higher VS-reduction, but it showed lower methane yield as compared to mesophilic digestion, i.e. 9 % and 11 % increment in methane yields for thermophilic and mesophilic digestions, respectively.