Comparative Research On The Effects Of Different Strains On Bioleaching Of Heavy Metals From Sewage Sludge

Sewage sludge as a concomitancy of wastewater treatment process is always a hard nut to crack which puzzles the normal operation of the wastewater treatment plant.Because of the continuously heighten processing degree and the constant enlargement of treatment scale,sludge production is also increasing. However,the sludge treatment technologies which have already been applied are low skill level,can not meet the needs of sludge control,and the high cost of sludge treatment and running have been one of the barriers to the sewage treatment plant,so the sludge issue is a big problem that has been disturbed the normal operation of the sewage treatment plant,and study on the sludge treatment and disposal technology has become the urgent affairs.Moreover,sewage sludge contains large amounts of nutritive elements which are necessary to plants growth such as organic matter and N,P,K etc,and has good fertilizer efficiency.Regardless of the economic efficiency,the environment benefit or treatment effect under the consideration,the sludge land use is a quite economical and feasible way.China is a large agricultural country, and the sludge land use is in accordance with Chinese conditions,has a very broad application prospect,and is conducive to creating a harmonious socialist society.However,the sewage sludge concentrated 1/2~4/5 heavy metals from the wastewater.If we apply the sludge to the farmland directly will lead to accumulation of heavy metals in the soil,threatening human health,therefore, how to reduce the amount of heavy metals efficiently from municipal sludge becomes the key issue of its land application.At present,in domestic and overseas the mean methods in removing heavy metals from sewage sludge are bioleaching,chemical extraction,electro reclamation,and Supercritical Fluid Extraction (SFE) and so on.In comparison,biological leaching technology receives much concern because of its less acid consumption,low operation cost, high efficiency in heavy metal removal, and strong practicality and so on.Currently,it is a just beginning study field for heavy metal bioleaching technology from sewage sludge.The purposes of the study are to the different removal effects of two different species of heavy metals in the sludge,quantitatively and qualitatively investigate the relationship between various physicochemical parameters and metal leaching and to provide a better understanding for the treatment of heavy metal from sewage sludge.Taking sludge from Taiyuan Yangjiabao sewage treatment plant as an object of study in this paper to find a suitable method to remove heavy metal from sludge for Taiyuan city,in order to make it meet the agricultural standards.The contents of Zn and Cd in the experimental sludge were:620.2 mg / kg and 32.97mg/kg,surpassing our sludge agricultural use standard for acid soil condition, must being treated before its agricultural use.Simultaneously,Cu is a heavy metal element which is relatively easy to exceed standard,so before the sludge using in agriculture we must take certain measures to reduce excessive levels of heavy metals o its activeness.Therefore, this paper takes Cu,Zn,Cd as the main control object.This paper has laid solid foundation for the further research of the mechanism of bioleaching process,and provided theoretical basis for enhancing the leaching effect and the leaching technology in the production practice application, providing an effective way for the removal of heavy metal for Taiyuan.According to the characteristic of heavy metals in sewage sludge of Taiyuan city,sewage sludge from Taiyuan Yangjiabao plant was adopted as culture substrate,and Thiobacillus ferrooxidans and Thiobacillus thiooxidans were used to the leaching of heavy metals from sewage sludge.This papermainly studied the removal effect of different strains of Cu,Zn,Cd during the bioleaching process.Research also shows that:Thiobacillus from the excess sludge can adapt quickly to the sludge circumstances can remove he-avy metals from the sludge effectively;pH=4 is the start value of sludge biology leaching;The ORP rise and the pH drop is corresponds;Adding substrate (Fe2+ and S) can increase the rate of leaching of heavy metals;The effect of Thiobacillus ferrooxidans is better than Thiobacillus thiooxidans on the leaching of Zn,Cd from Taiyuan sludge;Under each kind of process condition,the TN and TP drain greatly,but still maintain a good fertilizer effectiveness.