The Efficiency And Mechanism Of Pb²⁺ Removal By Polyphosphorous Granular Sludge

With the continuous acceleration of the pace of industrialization in China,the use of lead is increasing and then lead containing wastewater is also increasing.Lead containing wastewater will cause great harm to the environment and human body,and we need to deal with it strictly.At present,chemical precipitation method,adsorption method,electrolysis method,membrane separation method and ion exchange method are mainly used in the treatment of leaded wastewater in China.Most of the above methods have the problems of high cost,poor effect and easy to cause two pollution.Yet the biosorption is a low cost,good treatment effect and wide application of lead containing wastewater treatment technology,which has attracted wide attention in the academic circles.Therefore,based on the chelating effect of Polyphosphate on heavy metal ions,the characteristics of the granular sludge having the adsorption of heavy metal ions,and the phosphorus removal granular sludge contains a large amount of phosphate,in this study,the biological phosphorus removal granular sludge rich in polyphosphate bacteria was used to treat lead containing wastewater,and the removal efficiency and mechanism of lead removal under the short-term adsorption and long-term biological metabolism of the granular sludge were investigated.A SBR reactor after anaerobic and aerobic alternate operation was used to cultivate biological phosphorus removal granular sludge.After mature,the granular sludge was composed of a large number of brown particles and white particles,with compact structure,complete morphology and good sedimentation,and had excellent function of nitrogen and phosphorus removal.The average particle size of the particles is 583.80?m,the maximum particle size can reach 2000 ?m,the particle SVI5 is 29.6 m L/g,the SVI30 is 26.5 m L/g,MLSS=6416 mg/L,MLVSS=4031 mg/L,the isoelectric point p H of granular sludge is 3.3,the content of P in the particles is in the 32⁴0 mg/g.After the granular sludge system is stable,in a period of time,the removal rate of NH4+-N and TP can reach 100%,the removal rate of is 92%,and the removal rate of COD is over 90%.The biological phosphorus removal granular sludge was used to carry out sequencing batch adsorption experiment to treat high concentration Pb²⁺ wastewater(C(Pb²⁺)=10⁴00 mg/L),and through batch test,and the removal efficiency of Pb²⁺ by granular sludge under different adsorption conditions was investigated.The results showed that the highest removal efficiency of Pb²⁺?up to 99.9%?was achieved under the optimal adsorption conditions(p H=4 and the initial concentration of Pb²⁺ 150 mg/L),and the adsorption equilibrium reached in 20 mins.The adsorption of Pb²⁺ by biological phosphorus removal granular sludge can be described by Langmiur model,the correlation coefficient R2 is 0.9929,and the maximum adsorption quantity is about 49.51 mg/g.Ion exchange and chelation of phosphate with Pb²⁺ played a significant role in the removal of Pb²⁺ by using the phosphorus removal granular sludge.The results of Fourier Transform Infrared Spectroscopy?FTIR?indicated that a variety of functional groups such as –COOH,-OH and phosphoryl were involved in the removal of Pb²⁺ by phosphorus removal granular sludge.Through adding low concentrations of Pb²⁺(C(Pb²⁺)=1⁴ mg/L)to the biological phosphorus removal granular sludge system for a long time to investigate the removal of Pb²⁺ by the metabolism of phosphorus accumulating bacteria and the toxicity inhibition effect of Pb²⁺ on the biological phosphorus removal system for a long time.When the concentration of Pb²⁺ was 1 mg/L,the removal rate of Pb²⁺ could reach 100%,but the metabolism of phosphorus accumulating bacteria was briefly suppressed,and the removal of C,N and P was reduced.After continuous operation of 3d,the metabolic activity of phosphorus accumulating bacteria was also restored.After stable operation,the removal of Pb²⁺ could basically reach 100%,P removal rate reached 100%,COD removal rate was 91.6%,and TN removal rate was 40%.When the concentration of Pb²⁺ was increased to 4 mg/L,the removal rate of Pb²⁺ gradually decreased from 100% to about 70% with the operation.The physical and chemical properties of the system were mainly manifested in the decrease of particle size,the average particle size decreased from 583.80 ?m to 384.21?m,and there was a small amount of particle disintegration and the decline in the settlement performance.From the biological metabolism,the SOUR and enzyme activity of the granular sludge decreased,the activity of phosphorus accumulating bacteria was inhibited,the effect of the system dephosphorization was worse and the removal rate of P was reduced from 100% to 73%.On the overall level,the removal efficiency of Pb²⁺ is still high,the concentration of effluent Pb²⁺ is below 0.5 mg/L,which conforms to the national standard of emission.In addition,the amount of extracellular polymer secreted by granular sludge and the amount of intracellular synthetic PHAs decreased and the content of extracellular polymer decreased from 200 mg/g·VSS to 60 mg/g·VSS in the long run.