Effect Of Copper And Chromium On The Anaerobic Co-Digestion Of Phragmites Australis And Cow Dung

It is practical to produce bioenergy by anaerobic co-digesting of reed straws and livestock manures,basing on the background of the energy shortage and environmental remediation.In this study,the mixture of phragmites australis straws and cow dung as raw material for pilot anaerobic fermentation under the medium temperature 37.0±1.0oC conditions.The effects of copper salt and chromium salt on biogas properties,system stability,material degradation and enzyme activities during the fermentation process were researched,and the mechanism of metal salt on anaerobic fermentation was discussed preliminary.The conclusion showed that:（1）Copper salt could promote the arrival of the peak gas production.The low concentration of copper salt（30 mg Cu/L）had a positive effect on the cumulative biogas yield,gaining the highest cumulative biogas yield 158.82 mL/g TS,that was higher 43.62% than the control group,while the high concentration（500 mg Cu/L）had adverse effect.The pH value decreased firstly and then picked up then kept stable or increased slightly.The low concentration of copper salt could quicken the decrease and increase of pH value.The high concentration of copper salt retarded falling and recovery of the pH value.The high concentration of copper salt inhibited the increase and decrease of VFA content,the low concentration of copper salt promoted the increase and decrease of VFA content,then during the peak biogas production,the low concentration of copper salt promoted dehydrogenase and coenzyme F₄₂₀ activities.The low concentration copper salt had a positive effect on dehydrogenase and coenzyme F₄₂₀ activities that was the main reason of treatment group improving biogas production at the peak stage.The high concentration copper salt inhibited the amount of VFA was the main reason of the low biogas production.（2）Both the low concentration chromium salt（30 mg Cr/L and 100 mg Cr/L）and the high concentration chromium salt（500 mg Cr/L）enhanced the cumulative biogas yield,and 30 mg Cr/L treatment group received the highest cumulative biogas yield 131.60 m L/g TS.The lower the concentration of chromium salt was,the greater the cumulative biogas yield was.The three concentration chromium salt both inhibited the decrease of pH value and promoted its rise.The low concentration of chromium salt inhibited the rise of VFA content,and promoted the coenzyme F₄₂₀ activity.The middle concentration of chromium salt inhibited coenzyme F₄₂₀ activity,and promoted dehydrogenase activity.The low concentration Chromium salt gained more biogas production,which was due to the lowest concentration of chromium salt promoting the coenzyme F₄₂₀ activity and the relatively concentration of chromate salt promoting the dehydrogenase activity.The study investigated the impact of copper salt and chromium salt on anaerobic fermentation.This research revealed the variations of several important indexes of the anaerobic system co-digesting phragmites australis straws and cow dung.The results had guiding significance in wetland plant utilization and improvement of biomass fermentation technology.