Study On Solidification And Stabilization Technology Of Composite Heavy Metal Contamination In River Sediment

Since the 1990s,the heavy metal pollution in the sediment of a river has been severe due to the influence of the simple and extensive electronic waste disassembly process of the small workshop of pickling and burning plate processing located on both sides of a river in guangdong province.Among them,copper,nickel,cadmium,arsenic and lead have exceeded the standard seriously,and the endogenous pollution brought by them is at risk.Polluted sediment can directly release pollutants into the water environment,making the water quality worse.Secondly,sediment is also the main habitat of benthos and the source of food.Improper control will lead to the direct or indirect entry of heavy metals into the food chain,causing serious harm to the survival of plants and animals in the water environment and even the health of nearby residents.Therefore,it is necessary not only to intercept all external pollution,but also to solve the internal pollution problem in river sediment,so as to fundamentally improve and ensure the quality of river sediment and its overlying water.In recent years,research on remediation technology of heavy metal contaminated sediment has become a hot topic in solid waste treatment.At present,there have been good research results on single or the same type of heavy metal contaminated sediment,but these studies generally do not consider the key problem of coexistence of heavy metal and arsenic.The properties of most heavy metals are different from that of arsenic,and their responses to curing stabilizers are inconsistent.For example,some curing stabilizers play a significant role in the activation of arsenic in the stabilization of heavy metals.Recombination of reagents according to a certain proportion is explored to achieve the effect of joint repair.Therefore,it is of great significance to study the technology of solidification and stabilization of the sediment contaminated with arsenic and heavy metals in the river,so as to develop an effective and reliable solidification stabilizer to repair the sediment contaminated with arsenic and heavy metals.Taking a river in Guangdong Province as an example,to reduce the pollution of the river sediment containing heavy metals arsenic compound,for the purpose of the sediment pollution condition investigation and study of sediment pollution characteristics,the comprehensive assessment of their level of pollution and ecological risk,and design test experiment with different agent of arsenic composite solidification of heavy metal pollution of sediment stabilization effect,under the guide of composite curing heavy metal pollution of sediment were stabilization optimizing pharmaceutical engineering pilot application,finally discussed the curing stabilizers on the influence of heavy metals.The main conclusions are as follows:(1)In this study area,the pollution of complex heavy metals is serious,and the first three heavy metals exceeding the standard are arsenic,nickel and plumbum.The nemero index method and the potential ecological risk index method were used to evaluate the sediment,and the results showed that the pollution was concentrated at 0~0.5m,and the pollution decreased with the increase of depth.The heavy metals arsenic,nickel,copper and cadmium in 0~0.2m sediment are heavily polluted,and lead is moderately polluted.The overall level of potential ecological risk is high risk level.The heavy metals arsenic,nickel,copper and cadmium in the sediment of 0.2~0.5m are heavily polluted,and the overall level of potential ecological risk is low.(2)Six chemical formulations were designed to treat heavy metal contaminated sediment in the pilot experiment.The leaching toxicity was used as the index to determine the optimal combination of iron base and cement curing.The leaching amounts of the five heavy metals all reached the relevant standards.Among them,arsenic(98.37%)has the highest stabilization efficiency,followed by cadmium(97.73%)and nickel(97.62%).(3)According to the results of the pilot test,100 m~3 of heavy metal contaminated sediment was used as the volume of earth in the pilot test,and its leaching toxicity met the relevant standards.The optimal process parameters were obtained:the screening was performed twice,the screening efficiency was about 60 m~3/h,the humidity of stirred bottom mud was about 80%,the stirring efficiency was about 12 t/h,and the residence time was about 5 min.(4)The Tessier five-state experimental analysis was carried out on the original contaminated sediment and the stabilized sediment.The results showed that in the process of solidification and stabilization of the sediment,the five existing forms of heavy metals were changed,and the stable state mass fraction was improved to a certain extent.Combined with the leaching results of small experiments,the active mass fraction of heavy metals does not directly determine the size of the leaching amount,but for the same kind of heavy metals,the leaching amount will decline with the decline of the active mass fraction.In conclusion,this study is expected to provide theoretical research basis,process parameters and technical support for the implementation of the remediation project of arsenic-containing complex heavy metal pollution in river sediment.It provides reference basis for high efficient solidification of heavy metal and arsenic in sediment of urban river.