| Municipal sludge is a by-product of municipal sewage treatment.With the acceleration of urbanization and the increase of population,sewage discharge is increasing day by day,resulting in a large amount of sludge to be treated.At present,the treatment methods of sludge in urban sewage treatment plants in China mainly include gravity concentration,conditioning,centrifuge dehydration,etc.,and the resulting sludge cake is transported out for subsequent disposal,such as incineration,landfill,etc.However,the treatment efficiency is low,the cost is high,and the effect needs to be further improved.At the same time,at least 14% of the sludge has not been effectively treated.Sludge dewatering is an important part of sludge treatment,and its dewatering effect directly affects the subsequent sludge treatment and disposal process,so it is particularly important to develop efficient sludge dewatering technology.This topic in view of the low efficiency of municipal sludge treatment and sludge moisture content higher question research,based on the concentration technology in vacuum floating sludge concentration and chemical method to improve sludge dewatering performance,fold the screw type sludge dewatering machine for concentrated control of sludge dewatering processing,to build a highly efficient sludge dewatering system to improve the efficiency of municipal sludge treatment.(1)Study on the effect of vacuum floating thickening technology on sludge thickening at different stages.The sludge of aeration tank,anoxic tank,secondary sedimentation tank and concentration tank were thickened by vacuum floatation thickening technology.The floating sludge concentration,sludge height and concentration ratio,floating sludge volume and sludge discharge rate were taken as evaluation indexes.The optimal concentrations of the above four kinds of sludge by vacuum floating thickening technology are: 2656 mg/L,2033 mg/L,2314 mg/L,2044mg/L;When the height of the sludge is between 160 and 180 mm,the sludge floating concentration effect is the best.When the vacuum is less than 60 k Pa,the sludge floatation concentration is not obvious.When the vacuum degree is greater than 60 k Pa,the sludge floatation concentration speed is accelerated with the increase of the vacuum degree,and the solid-liquid separation phenomenon is gradually obvious.When the vacuum degree reaches 90 k Pa,the sludge floatation concentration effect is optimal.(2)Study on the effects of different chemical conditioning methods on sludge filtration performance,flocs particle size,potential changes and sludge morphology.By coking reactive liquid separate sludge conditioning,sludge stirring speed,stirring time and carbonized activated sludge liquid concentration affect the performance of sludge dewatering new,simultaneously will be carbonized activated sludge liquor and PAC and CPAM compound sludge conditioning,through the design of orthogonal test to determine each kind of reagents in the composite conditioner added amount and add the order,Sludge extraction speed,filtration time(TTF)and turbidity of supernatant were used as evaluation indexes to determine the influence of conditioner on sludge dewatering performance.In addition,the changes of Zeta potential and scanning electron microscope(SEM)were measured to understand the changes of sludge microstructure and flocculation performance.The optimal stirring speed of activated sludge carbonization solution was 180 r/min,the stirring time was 3min,the concentration of activated sludge carbonization solution was 10 mg/m L(i.e.M activated sludge carbonization solution: M deionized water =1:100),and the optimal standing time was 25 min.When the sludge carbonization active liquid is combined with PAC and CPAM to adjust the sludge,the sludge filtration speed is increased by 68%,and the weight of sludge cake is less than 3%.Although the addition amount of sludge carbonization active liquid is increased by 50%,the usage amount of CPAM is reduced by 40%.The adverse effects of residual CPAM in the subsequent disposal or utilization of mud cakes on the environment were reduced.The Zate potential of the sludge supernatant was significantly reduced to-6.158-5.0342,and the flocculability of the sludge was significantly improved.The microstructure of sludge flocculation is complete and the boundary between colloidal particles is obvious.The particle size of sludge flocs is larger,about 10-15 mm,which has a great positive effect on the dewatering of the stacked screw sludge dehydrator.(3)Performance optimization of the stacked screw sludge dehydrator.The sludge after chemical conditioning was dehydrated with the stacked screw sludge dehydrator.The influences of the three factors,the sludge intake amount,the rotating speed of the screw shaft and the distance between the back pressure plates,on the moisture content of the sludge cake and the solid content of the filtrate from the stacked screw sludge dehydrator were analyzed through the single factor experiment.The optimal range of these three factors is 750-870 m L/min,15-30 r/min and 3-5mm.Through orthogonal test analysis,it is concluded that when the sludge inflow is820 m L/min,the rotating speed of the screw shaft is 20 r/min,and the distance between the back pressure plate is 5 mm,the water content of the sludge from the stair screw sludge dehydrator can be reduced to 75%-76%,the sludge output can be increased by6-8%,and the sludge recovery can be as high as 93.75%.After a series of studies,fold the screw type sludge dewatering machine combined with vacuum floating on enrichment technology to recuperate for enrichment and dewatering sludge,and the filter cake moisture content compared to the current mainstream dehydration technology out of the mud moisture content can be further reduced by 5%-10%,fold the dehydration properties of sludge dewatering machine significantly increased,processing cost is greatly reduced,provide technical support for sludge volume reduction. |
