Investigation On The Enhancing Performance Of Landfill Leachate Anaerobic Treatment By Fe₃O₄ And Its Mechanisms

Landfill leachate is characterized by high organic matter concentration,complex composition,high salinity,and poor biodegradability.Therefore,it is very necessary to find a process that can strengthen the conversion of oragnic matter in landfill leachate.Anaerobic treatment of landfill leachate was taken as research object in this paper.Firstly,the efficiency of the anaerobic baffled reactor treating landfill leachate was explored.Secondly,the influence of the addition of Fe₃O₄ on the treatment efficiency of the anaerobic baffled reactor was studied.The mechanism of Fe₃O₄strengthening landfill leachate anaerobic treatment was investigated.The results are as following:Firstly,the efficiency of anaerobic baffled reactors?ABR?in treating landfill leachate was studied.When the COD concentration of influent was about 6100 mg/L,the COD removal rate on the 40^th day of operation stabilized at more than 90%,and methane production could reach 1250 m L/d.After acclimation,except for the first compartment,the actual methane production of the other compartments is higher than the theoretical methane production.The concentration of volatile fatty acids?VFAs?can reach 1370 and 1200 mg/L,respectively in the first and second compartments,and the concentration of VFAs in the latter two compartments is negligibly low.It shows that hydrolysis and acidification stage mainly occured in the first and second compartments of ABRs,and the functions of different compartments were separated.The acetoclastic and hydrogenotrophic methanogenic activity of sludge have been greatly improved by 146%and 58%,respectively.The concentration of EPS and SMP also increased.Changes in the salinity of the influent did not show serious negative impact on ABR operation.Therefore,anaerobic baffled reactor with phase separation characteristics could treat landfill leachate efficiently and stably.Secondly,the enhancement effect of adding Fe₃O₄ on anaerobic digestion of land-fill leachate was studied.When the influent COD concentration is about 7290 mg/L,two reactors stabilized on the 40^th day of operation at more than 95%COD removal rate.The methane production of the reactor added with iron trioxide was 200-350m L/d higher than that of the control group.Compared with the control group,the acetoclastic methanogenic activity,electron transfer activity and coenzyme F₄₂₀ of sludge added with Fe₃O₄ increased by 22%,27%,and 8%,respectively.However,the hydrogenic methanogenic activity of sludge did not change much.Obviously,adding Fe₃O₄ to ABR treating landfill leachate could improve the methanogenic activity and electron transfer efficiency of sludge,thereby increasing the methane production of landfill leachate.In order to explore the mechanism of strenthened landfill leachate treatment by Fe₃O₄,hydrolysis acidification and methanogenic stage of landfill leachate were tested separately.In the hydrolytic acidification stage,when the influent COD concentration was 2500 mg/L,the p H of reactor added with Fe₃O₄ could restored to7.0 quickly,which means the additon of Fe₃O₄enhanced the p H buffer ability and stability,effectively reducing the phosphate concentration by 10%at the same time.When the COD concentration of the influent increased to 3200 mg/L,the reactor added with Fe₃O₄could quickly adapt to the change of organic load,and the concentration of propionic acid and butyric acid was significantly lower than that of the control group.The static experiments showed that the experimental group with Fe₃O₄ increased methane production by 24.7%and the electron transfer activity by33.4%compared with the control group.Therefore,the addition of Fe₃O₄ could improve the acetoclastic methanogenic activity and electron transfer efficiency of anaerobic sludge,thereby enhancing the impact resistance of reactor and the methane production of organic matter in landfill leachate.