Mechanism Research On Filtration Dewatering And Rheology Of Soft Gel Solid

Soft solid gel materials are widely used in various fields,and their dehydration and rheology are hot topics in current research.Sludge is a typical kind of soft solid gel material.With acceleration of urbanization process,discharge of municipal sludge increased drastically,and it is difficult to dehydrate,especially without pretreatment.In this study,the urban sludge was used as the object to establish permeability equation for soft solid gel materials and to explore rheological properties of sludge in order to provide a theoretical basis for filtration dewatering and rheological properties of soft solid gels.In order to improve sludge dewatering performance,chemical conditioning,physical conditioning,biological conditioning and other pretreatment methods are usually used,among which chemical conditioning is used more widely.Based on previous studies,polyaluminum chloride(PAC),ferric chloride(FC)and cationic polyacrylamide(CPAM)were selected as sludge conditioner,and its dewatering and rheological properties were studied.The main conclusions are as follows:Control variable method was used to study effect of flocculant type,flocculant concentration and filtration pressure on sludge suspension filtration.Experiments show that the addition of flocculant changed sludge physicochemical properties significantly.CPAM makes floc size larger,specific surface area smaller,and fractal dimension decreased.Inorganic flocculants PAC and FC make the floc particle sizes become smaller,the specific surface area become larger,and the fractal dimension decreases.Flocculant dose and filtration pressure had little effect on solid content of filter cake obtained by sludge filtration.Increasement of flocculant dose significantly improved filtration rate of sludge suspension,but reduced solid content of filter cake slightly.Compared with FC and CPAM,PAC has obvious advantages in improving filtration rate of sludge suspension.While,filtration pressure had slightly impact on filtration rate and filter cake solid content,and significant negative correlation between permeability and filtration pressure was observed.Under certain filtration pressure,the sludge conditioned by PAC,FC and CPAM,the permeability increased by about 100 times,respectively.And Kozeny constant ranged from 4 to 100,13 to 150,and 100 to 2000 respectively.Furthermore,the Kozeny constant is linearly related to filtration rate.The rheological study of sludge suspension shows that sludge suspension belongs to pseudoplastic non-Newtonian fluid with yield value and is also thixotropic fluid.Because the sludge suspension rheological experiment in the linear viscoelastic region has certain rules to follow,the rheological properties of sludge suspension in the linear viscoelastic region are more practical.The results of this study provide theoretical basis for dewatering of soft solid gel materials,and provide reference for design of reduction process.It has important theoretical significance and application value.