Geotechnical Properties Of Soda Residue Solidified Sludge Under The Effect Of Leachate And Temperature

With the increasing requirements of municipal wastewater treatment,more and more sewage sludge is becoming a major problem for treatment or disposal in China.Using modified sludge as a daily cover material for landfills is one of the most effective ways to dispose of sludge.Considering that the landfill day cover material is in leachate soak for a long time,while the degradation of organic matter in the waste and the external temperature makes the landfill in high temperature.This paper cures municipal sludge with soda residue,ground granulated blast furnace slag and quicklime as curing materials,studies the changes of engineering properties of soda residue cured sludge under the action of leachate and temperature,reveals the mechanism of the action of leachate and temperature on the engineering properties of soda residue cured sludge,and provides theoretical support and technical reference for soda residue cured sludge as landfill day cover material.The main research contents and results are as follows:(1)The unconfined compressive strength test and consolidation compression test were carried out on soda residue cured sludge specimens to investigate the effects of soaking time,leachate concentration and soda residue dosing on the strength and structural yield stress of cured sludge.The test results show that the strength of the cured sludge is not favoured by excessive soda residue dosing under the long-term action of leachate;the leachate is aggressive to the cured sludge,and cured sludge specimens have a certain stabilising effect on the chromium,copper,lead and arsenic contaminants in the sludge and leachate during the long-term leachate immersion.(2)Unconfined compressive strength,consolidation compression and GDS infiltration tests were carried out to investigate the variation pattern of factors such as soaking time,soaking leachate concentration and soda residue dosing on the specimens.It was found that increasing the soda residue dosing from 40% to 60% improved the geotechnical properties of the cured sludge;the strength of the cured sludge increased when the temperature was increased from 12℃ to 40℃,but decreased when it was increased to 60℃;Compression and permeability coefficients of specimens at 40℃ lower than 20℃ and 60℃.(3)NMR tests,XRD analysis and SEM observations of the cured sludge were carried out.It was shown that hydration products such as needle-rod ettringite and C-S-H appeared in the soaked distilled water specimens to fill the pores and link the particles,while the soaked leachate specimens produced more calcium carbonate,in addition to ettringite and hydrocalumite,increasing the pore volume;as the temperature increased,the pore volume of the specimens decreased;when the temperature was 40℃,C-S-H increased and ettringite decreased,and the strength increased.