Page 85 - 2017地大报告电子书

环境学院发展报告

disposed and relieve the rapid growth pressure of waste sludge. In comparison totradition

al sludge dewatering processes, pressure electro-osmotic dewatering has many advantages
on sludge dewatering efficiency, low conditioner dosage and concentrated cake are both

beneficial to further recycling of waste sludge. In general, complex electrochemical effects
(eg. electrochemical oxidation, ohmic heating and pH gradient effect) are accompanied by the

pressure electro-osmotic dewatering process. These electrochemical effects will inevitably
cause solubilization and/or degradation of key constituents of wastewater sludge - extracellular p

olymeric substances (EPS).
In this study, the effects ofvoltage, pH and ionic strength on sludge electro-osmotic

dewatering performance and electrochemical effects were investigated. The solubilization and
degradation of

EPS were analyzed by examining the variation of dissolved organic matter (DOM) in the
filtrate, and the relationships between microstructural properties of sludge cake and DOM

and electro-osmosis dewatering performance in electro-dewatering process was examined. It
was found that electro-dewatering properties were improved by raising the operating voltage

or decreasing the pH value, while dewatering rate initially increased at low ionic strength it
decreases with increased ionic strength. In addition, the porous structure of cathodic cake was

more plentiful than that at the anode. At the cathode, the EPS dissolution was mainly
related to alkalization, while the oxidation and acidification were responsible for release of EPS at

the anode. Meanwhile, electrophoresis effect was able to promote migration of EPStoward the
anode. The average electro-osmotic dewatering rate at the anode (R-2.>0.79, p < 0.02) and at the

cathode (R-2.>0.87, p < 0.03) strongly correlated with the volume of pore of sludge cake. There
was no correlation between the total content of anodic DOM (R-2<0.31, p>0.08) and electro-

osmotic dewatering rate at the anode, however, the content of cathodic DOM (R-2 > 0.62, p <
0.09) negatively correlated with average

electro-osmosis dewatering rate of cathode.
Since cathode is the main water-permeable

side in sludge electro-dewatering, and the
sticky biopolymers (proteins and humic

subtances) could not be converted into
small molecules, higher EPS release was

associated with worse sludge filterability.

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