Experimental Study On Pre-removal Of Heavy Metals In Sewage

A large amount of sludgeproduced in water treatment process,and the heavy metals contained in the water will enter the sludge,which often causes the heavy metals in the sludge to exceed the standard,making the sludge a hazardous waste,which increases the difficulty of sludge treatment and disposal.In order to reduce the heavy metal content in the sludge,Advance generated the heavy metals in the source-wastewater from the sludge and avoid most of the heavy metals entering the sludge system,reducing the hidden dangers of heavy metals in the sludge.The paper pre-removed the heavy metals in the sewage,and examined the effects of static sulfide precipitation,sulfide precipitation flotation and ion flotation on the removal of heavy metals.A sludge-based adsorbent was prepared from the raw materials and applied to the experiment of pre-removal of heavy metals in sewage.The main conclusions of the paper are as follows:?1?Static sulphide precipitation and sulphide-precipitation flotation technique were compared,the removal efficiency of heavy metals is higher by static sulphide precipitation,but it is not suitable for the wastewater treatment process because it is difficult to separate its sedimentation.However the flotation test was simple and can effectively separate the heavy metal sulfide from the wastewater.The operation was feasible,but the removal efficiency was not high by sulphide-precipitation flotation,for example,the removal efficiency of Cr³⁺was only 3.27%.The effect of ion flotation on the removal of heavy metals from sewage was investigated,and some collectors were compared in the tests.The results showed that the highest removal efficiency can be obtained using dithio phosphate in ion flotation,and when thedithio phosphate dosage was 3.5 mg/L,flotation time 240s,stirring rate 120 r/min,the removal efficiency of Cu²⁺,Zn²⁺,Pb²⁺were 17.89%,and 16.24%respectively,with only 3.09%for removal of Cr³⁺.?2?Using sludge as raw material preparation of carbonized sludge particles,in order to improve the traditional sludge adsorbent make small specific surface area,the adsorption effect is poorer,the experiment add chestnut shell as recarburizer,using chemical activation method,compared with ZnCl₂ as activating agent,level and factor determined by single factor experiment,the optimum reaction conditions were determined through orthogonal test,determine the various factors affect the size of the order as follows:Activation temperature>chestnut shell scale>activator concentration activation time>solid-liquid ratio,the effect of solid-liquid ratio,minimum and carbonized chestnut shell preparation of sludge and sludge particle,the optimal preparation conditions for 60 min activation time,activation temperature of650?,the concentration of zinc chloride 3 mol/L,solid-liquid ratio 1:3,chestnut shell 20%,under the condition of the preparation of the carbonized sludge particles,and the characterization and application.?3?Sulphide precipitation--adsorption flotation process for removal of heavy metals from sewage was proposed and the effect of removal of heavy metals by this novel process was studied,and a new type of adsorbent,sludge carbonaceous particles,was prepared.For the wastewater sample with COD 465 mg/L,NH₃-N 55 mg/L,TP4.8 mg/L,and Zn²⁺0.513 mg/L,Cu²⁺0.121 mg/L,Pb²⁺0.072 mg/L,Cr³⁺0.112 mg/L,heavy metals removal tests were carried out.The results showed that when the dosage of carbonized particle was 10 mg/L and calcium sulfide was 5 mg/L,stirring time 2minutes,3 mg/Lof 733 oxidized paraffin wax soaps,1 mg/L of dithio phosphate,2minutes of flotation time after stirring for 1minute,the COD,NH₃-N and TP 4.8 in the treated water were 450 mg/L,47 mg/L and 4.2mg/L,and Zn²⁺,Cu²⁺,Pb²⁺and Cr³⁺were 0.16 mg/L,0.04mg/L,0.02mg/L,0.05mg/L,respectivly,the removal efficiency of Cu²⁺,Zn²⁺,Pb²⁺,Cr³⁺were 66.7%,68.6%,71.4%,and 50.3%,respectivly.The effect of sulfurization-adsorption-flotation experiment on the removal of heavy metals in smelting wastewater was studied.The experimental results showed that the foam products scraped by flotation experiments had high content of heavy metals and were a kind of high-quality metal mineral resources.The product was recycled,and the heavy metal in the smelting wastewater was effectively recycled and harmless.To a certain extent,the heavy metal content in the sludge produced by the smelting wastewater can be reduced and reduced the harm.Taking a lead-zinc smelting wastewater as the research object,the removal effects of several major heavy metal ions Zn²⁺,Cu²⁺,Pb²⁺and Cr³⁺in wastewater were studied.The experimental results showed that the removal of Cu²⁺,Zn²⁺,Pb²⁺and Cr³⁺in smelting wastewater The rates were 80.23%,79.26%,89.08%,and 41.06%,respectively.The foam products scraped by flotation experiments have high levels of heavy metals.It was a high-quality metal mineral resource that can be used to recover foam products and effectively smelt wastewater.The medium and heavy metals were resource-resourced and harmless,which can reduce the heavy metal content in the sludge produced by the smelting wastewater to a certain extent and reduce its harmfulness.