| Because of large quantities of excess sewage sludge produced from wastewater treatment plants,which has brought great pressure to wastewater treatment plants due to high operation cost of sludgetreatment and disposal,sludge dewatering has become one key link of sludge treatment.This paper studied the improvement of municipal sludge dewaterability through the biological acidification and ferrous oxidation caused by Acidithiobacillus ferrooxidans XJF8.The main results were shown as following:?1?The feasibility study of sludge bio-acidification and ferrous oxidation showed that the final pH of sludge dosing bacteria liquid and nutrition in flask cultured for 96 h,reduced to 2.57.The Fe2+ oxidation rate reached more than 98% and the sludge specific resistance was reduced to 0.57×1012 m·kg-1,which instructed the sludge belonged to easy dewatering sludge.The result showed that Acidithiobacillus ferrooxidans XJF8 strains could improve the dewatering performance of the sludge?2?In this part biological acidification iron oxidation reactor had been constructed.Two different laboratory-scale plug flow reactor were applied to improve the municipal sludge dewaterability.The results showed the pH of sludge in two reactors after the treatment eventually dropped under 3.00,and the SRFdecreased to 0.55±0.11×1012m·kg-1and0.29±0.11×1012m·kg-1,both of which were less than 1×1012m·kg-1,and belonged to easily dewatered sludge.The oxidation rate of Fe2+were more than 95%.After mechanical dewatering water without any flocculant the water content were 5861%and 5155%,respectively.The results showed that the At·f XJF8 strain in two kinds reactors could improve the performance of sludge dewatering.?3?Through the comparison of sludge dewatering effect treted two different plug flow reactors,the compartmentalized Air-lift plug flow reactor was more suitable for biological acidification iron oxidation of municipal sludge.The compartmentalized Air-lift plug flow reactor operation parameters were optimized.The results show that the reactor Fe2+ dosage should not be less than 0.50g/L;sludge retention time could be shortened to the 2.0d.?4?The shake flask experiments showed after acidification biological iron oxidation treatment the solubilization of proteins and polysaccharides content and distribution in sludge had changed.The dissolved protein and polysaccharide concentration in slime layer had decresed from11.05mg/g and 6.95mg/g rose to 15.24mg/g and 9.46 mg/g,respectively.The dissolved protein and polysaccharide concentration in LB-EPS had declined from 15.57mg/g and 9.42mg/g to 5.35mg/g and1.31mg/g,respectively.The content of soluble protein and polysaccharide in TB-EPS were increased from 16.26mg/g and 10.35mg/g to 5.47mg/g and 8.25mg/g,respectively.?5?After bio-acidifcation and iron oxidation treatment,the Zeta potential of sludge increased from-22.8mV to-2.35 mV.Compared with untreatment sludge,the percentage of particle diameter within 0100?m had decreased,indicating that the particle size of sludge after the treatment had increased.Throug SEM photos it was observed the structure of sludge after this treatment had changed from loose floc to compact blocks,wich increased the particle size.The block had shape regular surface,wich could be secondary minerals. |
PDF Full Text Request