Research And Application Of Bio Flocculan For Synergistic Treatment Of Heavy Metal Wastewater

With the development of ecological civilization in China,heavy metal wastewater pollution has become one of the restrictive factors for the metallurgical enterprises.At present,lime neutralization precipitation is one of the most commonly technologies for heavy metal wastwater treatment in smelting enterprises.Although the wastewater can be discharged after treated by lime,but its instability still allows enterprises to suffer tremendous pressure on the environment.Upper reaches of Bijiang river----source of drinking water located a smelting plant,which heavy metal wastewater was treated by two section of lime neutralization precipitation process.It is difficult for the wastewater after treated to achieve the purpose of the production reuse,no more to realize the inflexible requirement of "zero emissions".Consequently,it is urgent to upgrade the wastewater treatment process for the smelting plant in order to improve the water reuse rate.This paper takes the acid heavy metal wastewater of a melting plant from Yunnan as the research object,and a new way has been put forward which use self-made bioflocculant conbine lime to remove heavy metals from the wastewater.In this paper,the bioflocculant dosage,pH value and reaction time were studied as the effect factors on the removal of heavy metal in wastewater.After a lot of experiments and research,a new technology was put forward for treating the wastewater from the plant.The conclusions are as follows:(1)Through single factor experiments,the best experimental parameters were obtained which affecting the heavy metal wastewater treatment effect.The best experimental parameters are as follows:the bioflocculant dosage is 250mg/L,the reaction time is 25min,the reaction pH value is 10,the dosage of PAM is 5ppm.It can be seen from the titration curve of neutralization that there are two buffer areas in the process of adjusting the acid wastewater by lime.The first buffer is near pH value of 9,and the second buffer is near pH value of 10.5.(2)Comparison of the original and new treatment methods of the heavy metal wastewater can be seen that:the new method can not only make the heavy metal total precipitation in the lower pH value(pH=10),but also can reduce the residual concentration of heavy metal after treatment.(3)Through the range and variance analysis of the results of the orthogonal experiment,the optimal process parameters are as follows:the optimum reaction time value is10,the reaction time is 20min,the dosage of XLBJ-1 is 250mg/L.(4).The practical operation results show that the residual concentration of Pb2+,Zn2+,Cd2+andCu2+are varied from 0.01 mg/L～0.03 mg/L,0.01 mg/L～0.1 mg/L,0.003 mg/L～0.005 mg/L and 0.001 mg/L～0.01 mg/L in the purified water after decalcification,respectively.The results indicate that the purified water quality can reach respectively III standard of Environmental Quality Standard for Surface Water(GB3838-2002),which greatly improves the utilization rate of water resources.(5)Fourier transform infrared spectroscopy(FT-IR),scanning electron microscopy(SEM)and X-ray diffraction(XRD)are used to analysis the XLBJ-1,which indicates that the active group on the surface of bioflocculant XLBJ-1 is a prerequisite for the reaction with heavy metal ions and the complex clathrate mainly exists in the form of amorphous.