| In recent years,with the increase of sewage treatment and treatment depth,the amount of sludge production increase.As of 2015,the discharge of municipal sewage in China reached 53.52 billion tons,and the annual emission of sludge was about42.82 million tons(according to the water content of 80%).Therefore,the safe and effective treatment and disposal of sludge has become a key research issue at present.This study used sludge,stone powder and fly ash as raw materials,the optimum raw material ratio and sintering condition range of ceramsite were determined by different experimental methods,and the influence of different raw material ratio and sintering conditions on ceramsite Properties was analyzed.Finally,the optimum preparation conditions of sludge ceramsite were further determined by orthogonal test.The feasibility of the sludge ceramsite as a water treatment filler was investigated by using the self-made biological aerated filter(BAF)small test device,and the effect of its application in the treatment of domestic sewage was compared with the commercial ceramsite.The following conclusions are obtained through experimental study:(1)According to the single factor experiment,the effect of different raw material ratio on the performance of sludge ceramsite was studied,and the optimum raw material ratio was determined as sludge:stone powder:fly ash=40%:15%:45%.Under the optimum ratio of raw materials and sintering conditions,with the particle density,bulk density and compressive strength as testing indexes,the optimum technological conditions were selected by orthogonal test:preheating condition:300℃,25 min,roasting condition 1200℃,15 min.Under these conditions,the bulk density of sludge ceramsite is 0.664 g/cm~3,the particle density is 1.234g/cm~3,the compressive strength is 4.61 MPa,the hydrochloric acid soluble rate is0.98%and the porosity is 44.7%.Through the microstructure and mineral composition analysis of sludge ceramsite at different temperatures,it is found that there are many pores in the ceramsite under the optimal preparation conditions.With the increase of temperature,the interior of the ceramsite will gradually form a new crystal structure.The heavy metal leaching toxicity analysis of ceramsite and its raw materials showed that the leaching concentration of ceramsite was lower than that of raw materials which was far below the national limits.The mechanism of the firing process of ceramsite shown that proper gas production and fluxing components are the main factors for ceramsite expansion,the sinter temperature and time are the necessary conditions for the expansion of Ceramsite;The volume shrinkage of ceramsite is mainly related to the melting material,sintering temperature and time.(2)The sludge Ceramsites prepared under the optimum conditions was used as filler to treat the micro-polluted water and actual domestic sewage in the self-made biological aerated filter simulator.Under the condition of different operation stages and reaction,the reactor has achieved good effect of wastewater treatment.The removal rate of COD and turbidity in domestic sewage by sewage sludge ceramsite reactors were all above 80%and 90%,It shows that sludge Ceramsite as filler is feasible.In this study,three kinds of solid waste such as sludge,stone powder and fly ash were used as raw materials to study the preparation of ceramsite,and the optimum preparation conditions were determined,which provided theoretical guidance for the preparation of ceramsite and the utilization of waste resources.Meanwhile,the application effect of sludge Ceramsite as filler was investigated,and the utilization of solid waste and the integration of later application were realized. |
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