Heavy Metal Stability And Dewatering Method Of River Sediment Polluted By Electronic Industry

The river sediment polluted by the electronics industry has the characteristics of high heavy metal content,high environmental risk and high water content.Generally,heavy metals are stabilized and dehydrated after dredging before subsequent disposal.However,previous studies focused on the stabilization of heavy metals or the dewatering of sediment,which did not form a complete set of technologies that could stabilize heavy metals in sediment and also dehydrate sediment.which limited in application.In view of the above problems,based on the investigation of the current situation and characteristics of the river sediment polluted by the electronic industry,this paper studies the stabilization of heavy metals in the sediment and dehydrates the stabilized sediment.Finally,we will get useful technology for the stabilization and dehydration of river sediment pollu ted by heavy metals,also provides a basis for the treatment and disposal of similar sediment.The total amount,form distribution and environmental risk of heavy metals in sediment of a river polluted by the electronics industry in Shenzhen were investigated and analyzed.The results showed that the content of heavy metals in surface and middle sediment was higher than that in the bottom sediment.The highest values of Ni,Cu,Zn,and Pb were 1036.3 mg/kg,2493.8 mg/kg,2776.3 mg/kg and 121.4 mg/kg,respectively.The heavy metals in the surface and middle sediment of the river are mainly of low and medium risk,and which have high mobility and bioavailability,so it is necessary to stabilize the heavy metals in the sediment to reduce the environmental risk.The results show that the combination of hydroxyapatite and calcium oxide has the best stabilization effect,which can effectively reduce the exchangeable and carbonate bound heavy metals in sediment and increase the residual heavy metals.When the total dosage of the composite agent is 10% of the sediment,and the ratio of HAP and Ca O is 3:1,the leaching amount of Ni,Cu,Zn and Pb in the sediment can be controlled below 2.9 mg/L,0.6 mg/L,6.4 mg/L and 0.03 mg/L respectively,which are lower than the class ? limit “Technical specification for output disposal of contaminated sediment treatment plant of river and lake”.The plate and frame pressure filtration method was used to dehydrate the heavy metal stabilized sediment and optimize the conditioner.Fur ther,reduce the water content of the sediment to meet the relevant disposal standards.The experimental results show that PAC combined with CPAM is the most suitable compound conditioner.When the dosage is 1% and 0.5 ‰ respectively,the specific resistance of sediment can be reduced by 97.3%.When the pressure of the plate and frame is 1 MPa,the pressure filtration time is 10 min,the dosage of PAC is 1%,and the dosage of CPAM is 0.5 ‰,the moisture content of the heavy metal stabilized sediment can be reduced to 38.4%.The moisture content and leaching capacity of the sediment are lower than the class ? limit “Technical specification for output disposal of contaminated sediment treatment plant of river and lake”,which meet the separate processing requirements.