Effect Of Zero Valent Iron On The Anaerobic Digestion Of Kitchen Wastes

With the continuous improvement of people's living standards,kitchen wastes have occupied 60⁷0% of municipal wastes.Comparing with other municipal wastes,kitchen wastes contain higher organic components and moisture contents,traditional treatment methods such as landfill and incineration might cause secondary pollution,and compost would lead to the breeding of pathogens,so it was difficult for them to adapt the requirements of environmental protection.Due to the advantages of anaerobic digestion technology,such as converting the organics into biogas,generating clean renewable energy,it had been considered environmentally-friendly technology and widely used in treatment of kitchen wastes.But it was also affected by many factors,such as temperature,pH,organic loading and trace elements.Fluctuation of these parameters would lead to the imbalance of anaerobic digestion or even failure,which could cause the decline of the efficiency and decrease of the biogas yields.Especially,as indispensable element of methanogens,the kind and amount of trace elements were very important for accelerating the progress of methanogenesis and maintaining the system stability in anaerobic digestion.Iron,as the largest amount of metal elements in the cells and enzyme systems of methanogens,played a vital role in synthesis and activation of enzyme system.Among several forms of iron(Fe⁰,Fe²⁺,Fe³⁺),zero valent iron?Fe⁰?was an ideal additive,which could alleviate environmental pollution,make some refractory organics become easy treatment in the following biochemical process and easy to add for its stable property.The anaerobic sludge was acclimated,a mixture of kitchen wastes and zero-valent iron was fed by two different ways,semi-continuous way and batch way,under medium temperature?37±1oC?.The influence of adding zero-valent iron during sludge acclimation on methane potential output from kitchen wastes by anaerobic digestion was investigated.It also investigated pH,VFAs,COD,methane production and the optimal adding quantities of Fe⁰ in the kitchen waste's anaerobic digestion at certain organic loading,it might be as reference for engineering application.The experimental results show that:?1?Under the low organic loading,adding the appropriate amount of zero valent iron can strengthen the activity of anaerobic sludge and improve the methane production quantity and the stability of the kitchen wastes' anaerobic digestion system.But with the improvement of kitchen wastes' organic loading,the influence of Fe⁰ on anaerobic digestion of kitchen waste has become smaller and smaller,organic loading gradually become the main factors that affect the anaerobic digestion.?2?In 6.52 g VS/L of organic loading's single-phase anaerobic digesters,adding 500.0²000.0mg/L of Fe⁰ could promote propionic acid to the conversion of acetic acid,reduce the acid accumulation,enhance methane production and increase the yield of biogas of anaerobic digestion system.Adding 1000.0mg/L of Fe⁰ contributed to the largest biogas production and the highest COD removal rate of anaerobic digestion system,and increased by 34.98% and 14.52% respectively comparing with control group.