The Study Of Inorganic Conditioner With Na₂SiO₃ Used For Secondary Sewage Sludge Dewatering

The urban sewage-dewatered sludge?UDSS?containing cationic polyacrylamide is difficult to dewater.For improving the dewaterability of the dewatered sludge to meet the requirements of the final treatment and disposal for sludge,FeCl₃ and AlCl₃,Na₂SiO₃ and poly-silicon-aluminum-ferric-magnesium?PSAFM?were used as conditioner to adjust the UDSS.The the sludge was secondary dewatering by high press filtration.The results were shows as follows:?1?When Fe³⁺ was added into the UDSS,the inner structure of sludge was destroyed by the charge neutralism ad releasing more water.At the same time,because the function of precipitate produced by the hydrolytic action,the inner structure of the sludge was solidified,therefore the compressibility of UDSS decreased.Finally,the dewaterability of UDSS was improved and the ratio of moisture content of filter cakes can be decreased to 30%??2?For deep decreasing the moisture content of sludge,Na₂SiO₃ as conditioner was used to adjust the dewatered sludge.The results showed when Na₂SiO₃ was used alone,it had no effect on improving the UDSS's dewatering performance.However,under the effect of FeCl₃,Na₂SiO₃ can improve the dewaterabilityof UDSS.Besides,when the dosage of Na₂SiO₃ was 6.7%dry sludge,the dosage of FeCl₃ was 13.3%dry sludge,the moisture content of dewatered sludge can be decreased to about 52%.At last,to analyze the role of Na₂SiO₃ in adjusting the UDSS,the Zeta potential and inner structure of UDSS conditioned by Na₂SiO₃ and FeCl₃ were both studied.The results indicated that the networks structure produced by PAM in the UDSS was destroyed and a new kind of new networks structure was generated by Na₂SiO₃,which could improve the dewaterability of UDSS.?3?For deep reducing the moisture content of sludge and the cost,the poly-silicon-aluminum-ferric-magnesium?PSAFM?that synthesized with poly silicon acid,AlCl₃,FeCl₃ and MgSO4 was used to adjust the sludge.The results indicated that for sludge dewatering with high pressure,the effects of PSAFM were better than other,which was because of its inner structure and combined action of Al,Fe and Mg.When PSAFM was used as the conditioner for secondary sludge dewatering,the moisture contents of the urban sewage dewatered sludge can decrease to 50%.All the above results proved that PSAFM was an effective conditioner for secondary sludge dewatering.