Study On Stability And Solidification Of Heavy Metals Of Black-smelly Sediment In River

The discharge of domestic sewage and industrial wastewater leads to the deterioration of river water quality.At the same time,it can also lead to the phenomenon of black and smelly sediment and heavy metal pollution,which will have a serious impact on people’s life and health.In this study,the black-smelly sediment of river course with heavy metals exceeding the standard in a certain area of Shanxi Province was studied,then by adding curing agent to solidify heavy metals in sediment to prevent leaching.At the same time,the mechanism of curing heavy metals by biological promoters and activated sludge to eliminate black odor and different curing agents was discussed.The main findings of this study are as follows:(1)The efficiency and optimal dosage of bio-propagating agent and activated sludge for reducing black-smelly sediment were obtained.When the dosage is 3 nL/L and 10 g/L,the reaction time is 25 d,the reduction rate of organic matter in the sediment can reach 33.8%and 32.5%,respectively.The reduction rate of organic matter is 34.2%,which is basically the same as that of single addition.Three dimensional fluorescence measurement was carried out to monitor the changes of organic matter components in sediment before and after the reaction.It was found that with the stabilization treatment,the color changed from black brown,protein substances in sediment were gradually decomposed into humie acid substances and microbial metabolites.(2)The curing effect of sodium sulfide,sludge based biochar and lime on heavy metals in sediment was clarified.By comparing with the(soil environmental quality agricultu-ral land soil pollution risk control standard》(GB15618-2018),the problem of heavy metal Cu,Cd,Pb exceeding the standard was found in the sediment(Cu:237.65 mg/kg,Cd:2.97 mgg/kg,Pb:591.55 mg/kg).After adding sodium sulfide(15g/kg),,sludge-based biochar(3 g/kg)and lime(1 g/kg)to three Cu Cd Pb of heavy metals,it is found that three heavy metal forms were transformed from weak acid cxuactable and reductive states to oxidable and residue states,conversion rates of heavy metal Cu are 90.6%,90.4%and 89.8%,respectively,the conversion rates of the Cd are 90.3%,89.8%and 87.5%,respectively,the conversion rate of Pb is 88.3%,87.3%and 85.1%,respectively;After curing the bottom mud,the con-centration is lower than《the Surface Water Environmental Quality Standard》(GB3 83 8-2002).(3)The curing mechanism of three curing agents for heavy metals was investigated.The SEM-EDS analysis showed that the proportion of the three elements in Cu,Cd,Pb sludge-based biochar increased before and after curing,the growth rates were 89.9%,85.8%and 84.6%,respectively.At the same time,the surface of the sludge-based biocarbon is covered with a large number of particulate substances,making the porous structure change,indicating that the sludge-based biocarbonar mainly adsorbs heavy metals through its huge specific surface area and porous structure,with precipitation and ion exchange on the surface;after the addition of lime,the generated alkaline environment can promote the heavy metal in the bottom mud and OH-to form metal hydroxide precipitation,at the same time,the addition of lime makes the negative charge in the bottom mud enhanced,can produce a stronger electrostatic adsorption effect on heavy metal ions;the addition of sodium sulfide is mainly caused by S2-or hydrolysis of OH-forming a soluble product of smaller metal sulfide or hydroxide with heavy metalions.