渗滤液浸泡对碱渣固化污泥长期性能的影响

Influence of leachate soaking on long-term properties of sludge solidified with soda residue

以碱渣—矿渣—生石灰固化污泥用作填埋场临时覆盖材料为背景,开展不同渗滤液浓度、浸泡时间和碱渣掺量条件下固化污泥性质的研究,探讨渗滤液浸泡对固化污泥长期性能的影响规律及微观机理。结果表明:固化污泥在渗滤液中长期浸泡时,生成钙钒石和水化硅酸钙等物质,试样强度随浸泡时间的增加而增大,固化污泥有较好的耐久性;但当碱渣掺量60%的试样浸泡210 d时,试样中生成大量的碳酸钙和不同尺寸的钙钒石,结构变得疏松,试样出现裂隙,强度大幅降低,低于垃圾填埋场临时覆盖材料强度要求,碱渣掺量过多对固化污泥的长期强度不利。渗滤液对固化污泥有一定的侵蚀性,固化污泥强度随渗滤液浓度的增大而降低。固化污泥具有结构性,不同渗滤液浓度和浸泡时间下固化污泥结构屈服应力变化与强度变化规律基本一致。在渗滤液长期浸泡过程中,碱渣—矿渣—生石灰对污泥和渗滤液中的铬、铜、铅、砷等污染物可起到稳定作用。

Sewage sludge was solidified with soda residue(SR),ground granulated blast furnace slag(GGBS),and quicklime,which was used as a temporary covering material for landfills.The effect of leachate concentration,soaking time and SR content on the long-term properties of solidified sludge was carried out.The micro mechanism of long-term performance was investigated.The results indicate that hydration products such as ettringite and calcium silicate hydrate are generated when the solidified sludge is soaked in the leachate.The strength of the sample increases with the increase in soaking time,indicating that the solidified sludge has good durability to the leachate.Nevertheless,a large amount of calcium carbonate and ettringite of different sizes are generated in the sample with 60%SR content after being soaked for 210 d.Then the structure becomes loose,cracks appear in the sample,the strength decreases significanty,and its long-term strength reduces to lower than the strength requirement for temporary cover.Too much SR content is not good for the long-term strength of solidified sludge.The strength of solidified sludge decreases as the leachate concentration increases due to the corrosive effects of leachate.The solidified sludge is structural,and the changes in the yield stress under leachate soaking are basically similar to the strength.During the long-term leachate soaking,SR-GGBSquicklime can stabilize some pollutions such as chromium,copper,lead and arsenic in the sludge and leachate.