Performance Characterization And Mechanism Of Magnetic Conditioning-Electro Dewatering Of Activated Sludge

With the urbanization development of China, the dramatically increasing flow of sewage sludge generated from municipal and industrial wastewater purification has become a major societal problem over the last decades. For sludge dewatering and reduction issues, performance and mechanism of magnetic conditioning-horizontal/pressure electro-osmotic dewatering (CM-HED/MPEOD) for activated sludge (AS) was investigated in this study. The operating conditions was optimized using response surface methodology, dewatering effect and energy consumption were analyzed, bound water and free water were measured through differential scanning calorimetry, the removal and migration of organic matter such as polysaccharide, protein and humic substance were extracted and monitored. The results were as followed:When it came to the coupling magnetic conditioning, results showed that magnetic micro-particles (MMPs) dosage and magnetic field (MF) intensity were determined as 0.15 g/g dry solids and 0.065 T for the best dewaterability, respectively. MMPs conditioning could induce a slight coagulation among AS flocs, decrease acid-base interaction between the AS particles. The MMPs-conditioned AS also showed a network-like structure, banded cells with shrunk surfaces.The main experimental procedure for CM-HED included four successive units:MMPs conditioning-MF conditioning-drainage under gravity-HED. The optimum dewatering conditions for CM-HED with the final water content of 89.98% were 40 V and 120 min. CM-HED process effectively reduced the free water content (FWC) and bound water content (BWC)but increased the portion of BWC in AS. The corresponding removal ratios of bound water and free water were 52.89% and 95.86% at the anode side and 46.28% and 92.75% at the cathode side, respectively. The coupling magnetic conditioning led to the largest BWC reduction of 23.14% in CM-HED process. Gravity field caused the largest sludge reduction of 87.45%. Along with water removed by CM-HED process, the organic matter was trasferred from AS biosolids to supernatant/filtrate.The main experimental procedure for MPEOD included four successive units:MMPs conditioning-drainage under gravity-mechanical dewatering stage (MDW)-electrical dewatering stage (EDW). The optimum dewatering conditions for MPEOD with the final water content of 53.52% were determined as 400kpa/120 min for MDW,44.7 V/120 min for EDW. In the whole dewatering process, sludge mass reduction was 97.98%, the removal ratios of FWC and BWC achieved 99.67% and 82.91%. The largest reduction of BWC occurred during EDW and MMPC stages, while largest reduction of FWC occurred during EDW and DG stages. As CM-HED, the migration of organic matter in MPEOD was from AS solids to supernatant/filtrate. LB-EPS has a greater sensitivity to the action from outside.