Performance And Mechanism Of Potassium Ferrate(?) Enhancing Hydrogen Accumulation By Anaerobic Fermentation Of Waste Activated Sludge

Sewage treatment plants,as the last barrier for wastewater to enter natural water bodies,have far-reaching significance for environmental protection.Activated sludge process is widely used in sewage treatment plants because of its low cost,simple operation,convenient management,and high efficiency in removing phosphorus and nitrogen in sewage,as well as suspended solids and organic matter.However,the application of the activated sludge method has produced a large number of by-products—Waste activated sludge(WAS).Anaerobic fermentation is currently the conventional method for processing WAS.During this period,sludge reduction,resource and energy recovery,and environmental risk mitigation can be achieved at the same time.Potassium ferrate(K₂FeO₄,PF)has higher reactivity and selectivity than traditional oxidants,and has excellent disinfection and coagulation ability,so it is considered as a strong oxidant.In recent years,the application of PF has been extended to a new field,namely sludge treatment.PF has been proved to promote sludge dewatering,recovery of resources and energy,and removal of toxic and harmful substances.However,although some scholars have been studying the accumulation of hydrogen in anaerobic fermentation,the influence of PF on hydrogen production in anaerobic fermentation is still unclear.In addition,the influence of PF on sludge anaerobic fermentation process has not been clearly revealed,which hinders a comprehensive understanding of the sludge fermentation process in which PF participates.Therefore,this study aims to explore the effect of adding PF on hydrogen accumulation in the dark fermentation of sludge,and to understand the effect of PF on hydrogen production.First,this article explores the effect of different concentrations of PF on the cumulative hydrogen production through hydrogen accumulation batch experiments.The experimental results show that when the PF dose increases from 0 to0.09g/g TSS,the maximum hydrogen production increases from 1.47 to 8.35 m L/g VSS.When the PF dose is further increased to 0.12g/g TSS,the cumulative production of hydrogen will decrease to 6.31 m L/g VSS.Next,this study analyzes the influence of PF on sludge decomposition by measuring COD dissolution,VSS reduction and phosphorus release,and analyzes the influence of PF on sludge cell and EPS decomposition by EEM fluorescence spectrometry and lactate dehydrogenase/deoxyribonucleic acid(LDH/DNA).The experimental results showed that PF did accelerate the decomposition and destruction of sludge cells and EPS provided sufficient substrates for subsequent anaerobic fermentation to produce hydrogen.At the same time,EEM study also found that The existence of PF will destroy the composition of non-biodegradable substrate in sludge,reduce the percentage of non-biodegradable released organic matter,and promote the transformation of released organic matter from non-biodegradable to biodegradable,thus further improving hydrogen production.Secondly,this study further explored the mechanism of PF promoting anaerobic fermentation of surplus sludge by simulating various stages of fermentation.The experimental results showed that although the activities of microorganisms related to anaerobic fermentation were inhibited to a certain extent in the presence of PF,the induction and inhibition of hydrogen-consuming bacteria were more serious,and the above experimental results are also verified in the study of key enzyme activities.Finally,the influence of potassium ferrate on microbial community was measured and analyzed experimentally.The experimental results showed that in the presence of PF,the community composition and abundance of microorganisms in sludge anaerobic system were changed.Among them,the relative abundance of hydrogen-producing bacteria(such as Petrimonas and Proteiniborus)increased,while the relative abundance of hydrogen-consuming bacteria(such as Methanosaeta and Methylocaldum)decreased,which may be the reason why PF increased the hydrogen production.The research results of this article not only discussed the influence of PF on hydrogen production by dark fermentation for the first time,but also revealed the mechanism of PF's influence on hydrogen production,deepened the understanding of the sludge fermentation process in which PF participates,and expanded the application scope of PF.Treatment provides an alternative method.