Effect Of Sulfide Amendment On The Passivation And Stabilization Of Heavy Metals In Municipal Sludge

With the rapid development of urbanization process,the rapid development of industrialization,the development of urban construction and the expansion of the scope of urban areas,a large increase in population.the increasing number of urban sewage treatment plants was resulted,the daily sludge production of the sewage treatment plant is also increasing,the excessive heavy metal content of the sludge to make a lot of sludge is difficult to directly use.Disposal and utilization of sludge is an important problem to be solved in every city.In this study,Take Hefei city sewage treatment plant sludge as the research object,a series of passivation of heavy metals in municipal sludge was studied by adding the chemical immobilization method.Analysis the effect of heavy metal in sludge effective state and distribution effected by different proportions of sulfides,study the bright coli T3 photogenic bacteria's luminous intensity test and potted plant experiment,the effects of sludge passivated by sulfide on microbial toxicity changing and sludge passivated by sulfide on vegetable growth and heavy metal accumulation in plant was got,then discusses the effects of heavy metals passivated by sulfide in sewage sludge leaching amount in different leaching conditions,the passivation effect of heavy metals in sewage sludge and the stability of heavy metals was researched.The main research contents and results are as follows:1.Take Hefei city sludge as the research object,we added Na₂S and?NH₄?₂S amendents to passivate heavy metals in sewage sludge,suggesting that the sulfide amendents can improve the sludge pH,the sludge pH of Na₂S treatment was the most obvious,adding Na₂S and?NH₄?₂S amendent,the largest rise in pH compared with control group respectively was 3.1 and 1 units;Amendments on heavy metals in sludge Cu,Zn,Cd and As had significant passivation effect,the content of 2 kinds of amendents are effective in reducing the sludge of heavy metals Cu,Cd,Zn,As,exchangeable to carbonates,Fe Mn oxides and stable state transformation,the exchangeable Zn and Cd compared with the control group,the largest decrease reached 98.8% and 98.6%.2.Amendents added heavy metals in sewage sludge,the bioavailability of heavy metal passivated by sulfide are analyzed,it is concluded that the sulfide treatment can effectively reduce the sludge of heavy metals Cu,Cd,Zn,As effective state content,especially,the most ideal passivation effect of heavy metals Cu,Cd.wih the sulfide addition amount increases,heavy metals effective state content was reduced.The effectivestate of maximum decreases were 87.3% and 34.0%.3.The bright luminescent bacteria T3 of luminous intensity test and potted plant test was study.the toxic effects of sludge heavy metals passivated by sulfide had changed,the growth of vegetables and the heavy metal passivated by sulfide accumulation in vegetables were effect,the results showed that adding sulfide amendent after sludge extraction liquid,the light quantity is stronger than without adding amendent group.In a certain range of concentration,the toxicity of heavy metals and size of the luminous intensity of luminous bacteria change into a negative correlation,then it obtains that the adding amendent to passivate heavy metal can reduced the toxicity of heavy metals;through the pot experiment shows that,adding amendent,egetables biological group is slightly better than the control group,the content of heavy metals and adding amendent group of vegetables in roots and shoots the lower than the control group,while the content of heavy metals in the same treatment group in root vegetables is much higher than that of the shoot.The accumulation of heavy metals in the shoots and roots of the sludge was significantly lower than that in the control group.4.Study the stability of soil column leaching of heavy metals passivated by sulfide in sludge.The results show that the sludge passivated by amendents can reduce sludge heavy metals Zn,Cu and Cd leaching,enhance the stability of heavy metals in the sludge.The NaNO3 leach heavy metals Zn,Cu and Cd of sludge passivated by sulfide,the leaching amount compared with the original sludge were reduced 98.2%,70.3%,52.6%;citric acid solution leach heavy metals Zn,Cu and Cd of sludgepassivated by sulfide,the leaching amount compared with the original sludge were reduced 60.7%,74.9%,78.3%.Respectively,acetic acid solution leach heavy metals Zn,Cu and Cd of sludge passivated by sulfide,the leaching amount compared with the original sludge were reduced 51.2%,73.4%,88.6%.Study the leaching effect of the acid leaching conditions of heavy metal of sludge passivated by amendents,acetic acid leaching compared with citric acid leaching,the heavy metals Zn,Cd,Cu leaching amount were decreased.the leaching curve was more smooth,indicating that under the conditions of acid leaching of heavy metals passivated by sulfide in sewage sludge is also difficult to leaching.