Solidification Of Sludge From Municipal Wastewater Treatment Plants With Phosphogypsum, Fly Ash And Carbide Slag

Because of the city sewage plant sludge with high content of organic matters, highmoisture content, perishable and fetid, and contains a large number of pathogenicbacteria and heavy metals,they are harmful to human health and environment.If the citysewage sludge processing is undeserved which can cause serious environmentalpollution accident.As a result of the soil mechanics nature of sludge is special, The finaldisposition of city sewage sludgeis a diffieult problem and a challenge which bothdomestic and abroad have to face.This thesis is using fly ash, phosphogypsum and carbide slag as a curing agent forthe city sewage plant sludge solidification under the Chongqing climatic conditions,ultimately for landfill disposal. The main content of this paper is the determination ofthe curing agent, sludge and solidification sludge properties, including the moisturecontent, specific gravity, pH value, coefficient of permeability, leaching toxicity,calorific value.Through the study we found when the dewatering sludge and curingagent ratio is sludge70%, phosphorus gypsum12%, fly ash6%, carbide slag12%,cured under certain conditions and the solidified sludge properties can achieve the”Thesewage treatment plant sludge disposal–mixed landfill with sluge”GB T23485-2009requirements of the transverse shear strength>25kN/m2, and moisture content <45%.The pollutants concentration in the leaching solution of solidification sludge canachieve the” Municipal solid waste landfill pollution control standard”GB16889-2008requirements.In the three kinds of curing agent, fly ash is provided volcano ash active substance,which is the main body of curing agent, but due to the fly ash lack of Ca2+, the fly ashitself does not provide sufficient solidification strength, we need calcium excitingactivity. The carbide slag has three functions,first as a fly ash activator,second as adeodorant absorb the emission of sludge,third as a bactericide, bacteriostatic agentinhibition of microbial breeding. Phosphogypsum’s functions is as phosphateactivator,provide the mechanical strength, and the residual phosphate ofphosphogypsum can solidification of heavy metal ions in the sluge, Reduce the amountof leachingIn the solidified sludge curing process, the key condition is ventilation anddrainage, curing temperature on curing process provided little effect.Though the study we found that in the winter of Chongqing, the curing process can be carried outnormally if we have the a good ventilation and drainage condition, and the solidifiedsluge strength increased gradually with time.The solidified sludge permeability coefficient is lower than10-7cm/s according tothe solidified plan. Because of the solidified sludge nature will not change afterimmersion in waterand will not corruption, so it can be used as a landfill cover soil,realize certain resource utilization.