Researches On The Sludge Dewaterability Co-conditioned By Electrolysis And Its Combination Technique

Sludge is an important byproduct of urban sewage treatment. According tostatistics, the amount of sludge produced in China in up to30million t (80%in watermeter). Difficult due to dehydration, resulting in high disposal costs. Improve theperformance of sludge dewatering, sludge treatment has become the most importantissue. In view of this, this paper studies the impact of electrochemical technologies andtheir combined effects with flocculant, pressure, ultrasonic, electrolytes for sludgedewatering. The main conclusion of the study include:(1) Optimization of electrochemical oxidation parameters:Capillary Suction Time(CST) and Dry Solid (DS) were measured as a metric of the sludge dewaterability.Sludge had treated by electrochemical methods with anode and cathode that were madeof graphite plates in the electrolysis facilities. The factors contained voltage, electrodedistance, electrolysis time and electrode insert depth and so on. The optimal parametersof these factors were determined by orthogonal test (L49(3)). The results showed thatthe order of the influence on dewatering performance was voltage> electrode distance> electrolysis time> electrode insert depth. Moreover, the optimal parameters werevoltage of20V, electrode distance of2cm, electrolysis time of20min, electrode insertdepth of6cm, respectively. Meanwhile, the CST of sludge has decreased significantlyby19.6%, DS has increased by5.85%than that of untreated sludge.(2) Electro-osmosis parameter optimization: The Solid content of mud cake beingas the index of sludge dewaterability, the response surface methodology (RSM) wasused to study the optimal parameters of electroos-mosis sludge. The results indicatedthat the optimum initial sludge solid content, initial voltage gradient, and initialthickness of sludge were8.58%,20.88V/cm,2.25cm, respectively, solid content of mudcake was48.82%(forecast value was48.45%) under the optimal parameters. RSManalysis of variance results showed that regression model reached the significant level,fitted well in the study area (the initial sludge solid content:5%-10%, the initialvoltage gradient:12-30V/cm, the initial thickness of sludge:1cm-2.5cm), andhaving higher coincided degree with the experimental results.(3) Study the effects of different electric field coupling technology to sludgedewatering. The results showed that:â‘ Different electrolytes (NaCl, CaCl2, Na2SO4, NaHCO3) effect on sludgedewatering. The results showed that: It was found that the amount of dosing canincrease the conductivity of the sludge to improve sludge dewatering; excess addedsludge dewatering effect will be reduced. Several different electrolytes, adding NaCl,CaCl2is best than adding Na2SO4and NaHCO3. NaCl and CaCl2electrolyte comparedto the effect of CaCl2best choice.â‘¡Different pressure (10Kpa,20Kpa,30Kpa,40Kpa) effect on sludge dewatering performance. The results showed: Adding pressure to improve theperformance of sludge dewatering,10Kpa, under20Kpa,30Kpa,40Kpa conditions,sludge dewatering performance increased by27.4%,35.0%,46.8%,38.6%. Thus, thepressure applied to the control30KPa.â‘¢Add different flocculants (NPAM, CPAM),. The experimental results showedthat: after adding CPAM, the largest sludge dewatering performance improved by23.6%, while adding NPAM sludge dewatering performance improved after themaximum of20.3%. Add CPAM600/DS=0.5%, CPAM900/DS=0.3%,CPAM1200/DS=0.25%, the sludge dewatering performance increased by23.6%,21.4%,19.8%.â‘£Study its effect on sludge dewatering performance use ultrasonic cavitation.The results showed that: Ultrasonic sludge particles can be broken to release themoisture inside the sludge. Ultrasonic intensity of12W,24W,36W,48W, sludgedewatering performance increased by6.4%,11.9%,14.6%,9.8%.(4) The use of TIESSER studied electrical osmosis treatment sludgedewatering metals speciation change Experimental results show that,â‘ afterelectro-osmosis treatment, reduce heavy metals in the sludge, Zn, Cu, Pb removal rateswere64.35%,57.61%,43.03%.â‘¡electro-osmosis treatment of heavy metals in thesludge morphological changes, the steady-state organic and residual soluble state to anunstable state, carbonate bound and Fe/O-bound transition. In the sludge, Zn mainly inthe unstable state water soluble, carbonate-bound, Fe/O-bound existence,its migration strong, in the sludge, Cu and Pb mainly in the steady-state organicfraction, residual presence migration poor.