Deep dewatering of municipal sludge by combining alternating electric field electro-osmosis and nano-CaO2 oxidation

Abstract

To improve the effect of traditional electroosmotic sludge dewatering, combining alternating electric field electro-osmosis and nano-calcium peroxide (CaO2) oxidation, a homemade vertical electro-osmosis dewatering device was employed in this work to study the effects of different parameter on the dewatering of primary dewatered sludge from municipal sewage treatment facilities with a moisture content of around 85%. The sludge water content (Wr) was used as an indicator, and concentration of extracellular polymeric substances (EPS) in the dewatered sludge was measured, and its structure was analyzed to investigate the effect of EPS changes on sludge dewatering.The response surface method was used to optimize the parameters. Wr decreased to 36.23 % at a CaO2 amount of 14.79 mg·g−1 dry sludge, a time ratio of 7.98:1, and a voltage gradient of 19.71 V·cm−1. Analysis of zeta potential and infrared characterization indicates that under acidic circumstances, CaO2 reacts more positively with water to produce hydrogen peroxide, and EPS is more easily destabilized and degraded, due to this, the problem of unequal water content in the cathode and anode sludge cakes is also solved. During the sludge dewatering process, the synergistic effect of alternating electric field and calcium peroxide together destroys the cell structure and EPS of sludge, especially the tightly bound EPS (TB-EPS), enabling the migration of substances and the formation of loosely bound EPS (LB-EPS), slime EPS (S-EPS), or filtrate, which can improve the sludge dewaterability.