Study On Leaching Characteristics Of Co-disposal Of Waste Incineration Fly Ash And Leachate Concentrate

The fly ash classified as hazardous waste is produced during the waste incineration process,the heavy metal cause harmless to human health in the transportation.In addition,domestic waste will produce a large amount of leachate during storage or landfill.Membrane method(nanofiltration membrane,reverse osmosis membrane or a combination of the two method)is the main method of leachate treatment,but a large amount of concentrate will produced.The concentrate has complex composition with high organic content,poor biodegradability and high salt content.Improper handling can cause serious pollution to water and soil.At present,there are few related studies on co-processing of fly ash and leachate concentrate based on solidification stabilization method,and the risk of heavy metal leaching still lacks systematic research.Based on this study,co-disposal of fly ash and concentrate was carried out to explore different treatment methods for heavy metals in fly ash.In order to provide a scientific experimental basis and theoretical basis for the comprehensive treatment of fly ash and concentrate.The following conclusions as follows:(1)The short-term leaching behavior of different heavy metals is greatly affected by the ashing rate.The ashing rate increases,the leaching of Zn,Pb,Cd,Cu,and Al will increase,and the leaching of Ba decreases.After the addition of the concentrate,the amount of leaching of Zn,Pb,and Cu is reduced,and the leaching of Ba is increased.The long-term leaching behavior of different heavy metals is also affected by the ashing rate.The increase of the ashing rate reduces the leaching of Zn and the leaching of Pb and Cd in the solidified blocks.The leaching amount of Zn,Pb,Cr and As will not increase on the 36 th day,and the leaching amount of Ba increased linearly.After the addition of the concentrate,the leaching amount of Zn,Cd and As increased slightly,and not exceed the standard value,which can meet the requirements of leaching toxicity of curing or resource treatment.(2)In phosphate stabilization,the dosage of the drug increases,and the leaching of Zn,Pb,Cu,and Ba decreases.After the concentrate is added,the leaching of Zn and Cr decreases,Pb,Cu,and Ba will increase,the leaching concentration of Pb after adding the concentrated solution for phosphate stabilization treatment exceeds the standard value and cannot be directly landfilled.According to the comprehensive evaluation of the metal stabilization rate,the optimum dosage of phosphate stabilization is 5%.In the stabilization of the chelating agent,there was no significant correlation between the dosage of the drug.After the concentration of the leaching solution,the leaching concentration of Cr decreased,and the leaching concentration of the chelating agent stabilized Pb failed to reach the standard value,and the stabilization rate was stabilized.In other words,different metals have different stabilization rates when different dosages of chemicals are applied,and it is difficult to select an optimal dosage ratio.(3)The effect of compounding agent on different heavy metals is different.When Zn is added in the ratio of phosphate compound 3.5% chelating agent 1.5%,the stabilizing effect is best.The ratio of Cu in compounding agent is phosphate 4% chelating agent Stabilization.Adding cement during stabilization treatment has different treatment effects on different metals.The leaching of Zn and Pb decreases with the increase of cement addition.The leaching concentration of Cu and Cd after adding cement is lower than the detection limit and stable.The effect has been significantly improved.In general,phosphate stabilization is better than chelating agent stabilization.Pb stabilization effect phosphate agent is superior to chelating agent.Zn,Cu,Cr stabilization effect chelating agent is superior to phosphate agent,comprehensive metal Stabilizing effect,the chelating agent has a better effect on the treatment of fly ash by adding concentrated liquid.In order to stabilize the effect of various heavy metals and to consider the economic feasibility,when adding 5% cement to the fly ash,the addition of 5% cement can increase the stabilization efficiency.At present,the fly ash treatment method commonly used in landfills is to stabilize the fly ash with the cement,and it is feasible to use the concentrate instead of the water to achieve the co-disposal.The effect of the cement curing method is better than the drug stabilization method.