Study On Surfactant Combined With Hydrogen Peroxide To Improve Dewaterability Of Sludge

In order to improve the dewaterability of sludge,we used the combination of surfactant with the hydrogen peroxide?H₂O₂?to treat the sludge.Three kinds of surfactants,such as cetyltrimethylammonium chloride?CTAC?,sodium dodecyl sulfate?SDS?and alkyl glycoside?APG 0810?,were selected in the test.The result shows that the best surfactant is CTAC when combined with H₂O₂.Through tests,we found the effects of various influencing factors on sludge dewatering and the order of their influence.Moreover,we got the optimum condition for improving sludge dewatering in the combination of CTAC and H₂O₂.And the mechanism of sludge dewatering was analyzed by measuring the changes in the zeta potential,particle size,microscopic morphology and extracellular polymer?EPS?content of the sludge floc.By adding surfactants CTAC,SDS,and APG 0810 to the raw sludge alone,it was found that the sludge dewatering was the best by adding CTAC.In addition,the effect of adding surfactants under acidic conditions is better.The combination of CTAC,SDS and APG 0810 with H₂O₂ showed that cationic surfactant CTAC combined with H2O2 had the best effect on the treatment of sludge,and combined treatment could reduce the dosage of CTAC and H₂O₂.The optimal sludge conditioning method for combination is to add H₂O₂ after CTAC.And the optimum condition for the combined treatment is this:the initial pH=3,first adding CTAC 73.2 mg/g TS,and then,adding H₂O₂ 1 mL/L to the sludge and let it oxidize for one hour.In this way,the mud cake moisture content was reduced to 64.3%,and the specific resistance decreased to5.92×10¹¹ m/kg.Through the orthogonal test,it was determined that when the CTAC and H₂O₂ were combined to treat the sludge,the order of the influence of each influencing factor on the moisture content of the sludge and the sludge specific resistance:pH>CTAC dosage>H₂O₂ dosage>H₂O₂ oxidation time.Through the mechanistic analysis tests,it was further found that the addition of H₂O₂ and CTAC under acidic conditions can improve the zeta potential of the sludge.The value of the zeta potential was improved to-0.58 mV when CTAC and H₂O₂ was combined.The zeta potential has a certain relationship with the floccule size of the sludge.Through the particle size analysis test,it was found that the floc size of the raw sludge is the smallest,the cumulative volume percentage Dx?90?is 128.4?m.And after H₂O₂ conditioning,the sludge floc was tighter and the particle size became larger,and the Dx?90?is 155.2?m.After CTAC treatment,the sludge floc increased significantly,and the Dx?90?is 230.5?m.When the two chemicals are combined,the floc size become smaller,and the Dx?90?is 176.1?m.In addition,we observed the microscopic morphology of the sludge floc.It was found by the light microscopy that the sludge floc in the raw mud was loosely bound,and the flocculation of the sludge after treatment was more compacted.Through electron microscopy observation,it was found the sludge floc was the most compact when treated by CTAC alone,and the the sludge flocs became more broken when the two chenmicals were used together to treat the sludge,and there were a lot of tiny gaps between the sludge flocs,forming lots of drainage channels.After the sludge was treated with H₂O₂,the concentration of EPS increased significantly,indicating that H₂O₂ could damage the cell wall and release intracellular substances and water.After CTAC treatment,the content of S-EPS in sludge increased,and the total EPS content decreased significantly.It shows that CTAC can promote the solubilization and release of EPS in the sludge,which could increase the EPS content in the solution,and reduce the content of LB-EPS,and help to improve the dewatering performance of the sludge.When the two chemicals are combined,the contnet of LB-EPS didn't increase much,while the TB-EPS increased a lot.Therefore,the mass ratio of TB-EPS and LB-EPS increases,and making the sludge dewatering performance further improved.