Building Of Sludge Electro-dewatering Model Based On Percolation Theory

The electric field plays a significant role in the process of sludge dewatering,The degree of dewatering will have a direct impact on the disposal and resource utilization of the sludge.However,current research mainly focuses on the experimental analysis and optimization of operating conditions in the process of electro-dewatering,how to process a vivid theoretical analysis of the electro-dewatering and predict the effect of electro-dewatering quantitatively by using accurate model is a necessity.The movement of moisture in the sludge which realizes the solid-liquid separation is given detailed description based on the seepage theory and current conduction mechanism and the math model of electro-dewatering is built in this paper,which clearly represents the variation of dehydration amount and current with time changing,the accuracy of the model expression is verified by the experiment,results have shown that the experimental data highly approximates with the model data,and the average relative error does not exceed 10%.On the basis of math model in electro-dewatering,this paper explores the effect of chemical modulation and physical function on electro-dewatering,then analyzes their influence on the parameters,such as: K1、K2、K3、K4,and finally get the reversed model in the specific condition under which the sludge characteristics and the water form among the internal structure of floc are changed.Calcium chloride and surfactant CTAB are used for chemical modulation of sludge,the effect of dosage on dewatering content and current are analyzed,results show that with thickness of 4.0 cm and under the voltage value of 30 V,as the dosage of calcium chloride and surfactant CTAB increases,the dewatering content of sludge goes up significantly;the initial current of sludge pretreated by calcium chloride is obviously higher than that in pure electro-dewatering,the initial current reaches above 7.50 A when the dosage of calcium chloride is 146.0 mg/gDS,whereas the initial current is only 2.78 A in the process of pure electro-dewatering,the initial current of sludge pretreated by surfactant CTAB has no obvious regularity;The current decay rapidly after being pretreated by chemical reagent,but current remain at a higher level than that in pure electric dehydration overall.Ultrasonic is used for physical pretreatment before electro-dewatering,previous study has shown that,the ultrasonic being applied into sludge for 3.5min with the frequency of 20 kHz and the power of 40 W has great effect on electro-dewatering,in the process of which the voltage gradient is fixed at 30V/cm.ultrasonic can effectively destroy the sludge floc structure and increase the electro-dewatering rate.The orthogonal experiment is added to the paper to verify the accuracy of previous inquiry experiment.Result shows the initial current in sludge being pretreated by ultrasonic is relatively higher reaching to 5.45 A and the decay tendency of current is more obvious than that in pure electro-dewatering.The internal structure of floc and water form are improved by Ca2+,CTAB and ultrasonic,which results in the conductive resistance of sludge being changed,and ultimately affect the electro-osmotic flow and current.Through reversing the related parameters related with sludge characteristics,finally get the model of electric dehydration being pretreated by Ca2+,CTAB and ultrasonic.The microstructure of sludge under specific condition are observed through scanning electron microscope,which reveals the floc structure of sludge,and the floc structure is obviously changed by Ca2+,CTAB and ultrasonic through observation.