Reaserch On Treatment Of Sludge Dewatering By Electroosmosis-pressure Filtration

With the development of urbanization in China,the amount of sludge produced by municipal sewage treatment plants and construction sites is increasing,in which the amount of wet sludge discharged directly each year has exceeded 30 million tons.Due to the high moisture content and huge volume,the untreated sludge will cause the serious environmental problems.Therefore,enhancing the dehydration efficiency,reducing the sludge moisture content as well as realizing sludge reduction are the key problems faced by Chinese researchers.Up to date,the conventional belt filtration and centrifugal dehydration technologies in municipal wastewater treatment plants can only reduce the sludge moisture content to about 80%.In this paper,the combination of mechanical dehydration technology and electroosmotic dehydration technology is developed to treat the dehydration sludge and piling sludge in municipal sewage plants.The effects of electroosmosis and pressure filtration process on the dehydration properties of sludge dehydration such as moisture content,specific resistance and extracellular polymer?EPS?,solluted chemical oxigen demand?SCOD?are systematically investigated.As a result,a new type of high pressure pulse electroosmotic filtration?HPEF?device and a new technology for the treatment of deep dehydration of sludge have been developed,which can reduce the moisture content of sludge dehydration to 60%.The main study results are as follows:?1?A new type of insulating high voltage pulse composite electrode is designed by using insulating material to cover metal plate.The breakdown voltage of the electrode and the thickness of the insulating layer of the cathode and anode conform to the empirical formula U=K?X+Y?,in which X,Y are the thicknesses of cathode and anode insulation layers,and K is a constant related to the dielectric constant of the insulating material.?2?The moisture content of dehydrated sludge in wastewater treatment plant can be reduced from 80%to less than 60%by using insulating composite electrodes as both cathode and anode with the electric field intensity of 7.5-10kV·cm^-1 and mechanical pressure of 50 kPa for 15 min.The results demonstrate that the electric field intensity of high voltage pulse is the key factor to improve the specific resistance of sludge dehydration,in which the mechanical pressure and electric field intensity have synergistic dehydration effect.?3?The treatment of sludge with high voltage pulsed electric field can not only effectively destroy extracellular polymer?EPS?coated on sludge surface,but also increase soluble organic carbon source in filtrate.When sludge is treated with 10 kV/cm high-voltage pulsed electric field and pressure filtration for 15 min,the concentrations of protein,polysaccharide and SCOD in sludge filtrate are greatly increased,which are296.6%,361.8%,and 1059.9%,respectively,of the original one.At the same time,it can reduce the content of heavy metals such as mercury,copper,chromium in sludge,so as to effectively reduce the content of toxic and harmful components in sludge.?4?The combination of electroosmosis and pressure filtration is developed to treat the mud of pile foundation.No flocculant is used in this treatment.The IrO₂-Ta₂O₅/Ti coating electrode and stainless steel electrode are employed as anode and cathode,respectively,for the rapid dehydration process of pile foundation mud.The results indicate that pile foundation mud can be dehydrated quickly.The discharge rate of 5.58L/?min?m²?.The moisture content of mud cake is 57.9%.?5?The deep dehydration device for sludge treatment by electroosmosis and pressure filtration of kg level has been designed,in which both low pressure electroosmosis and high pressure pulse electroosmotic dehydration can be realized simultaneously.The dehydration effect of the device on sludge from different sources has been investigated.The results illustrate the deep dehydration technology combined with high pressure pulse electroosmosis and pressure filtration is suitable for the deep dehydration of municipal sludge and canal sludge.In this paper,the deep dehydration technology combined with high pressure pulse electroosmosis and pressure filtration has many merits.On the one hand,this technology can reduce the treatment time,thereby it has a high efficiency.On the other hand,this strategy also can avoid the corrosion of anode.As a result,this novel deep dehydration technology presents a good prospect of development and application in the future.