Study Of Sludge Conditioning With Magnetic Particles And It's Function Mechanism

One of the indispensable work in Municipal Sewage Treatment Plant(MSTP) is sludge treatment and disposal, whose purpose is reducing volume, stabilitying, no-poisonous and comprehensive survey, guaranteeing the property operation and the treatment effect of MSTP, presenting a second pollution. The targets of the study are as follows: synthesizing Fe₃O₄ nano-particles; study on effect of Fe₃O₄ nano-particles on settling ability and dewaterability of sludge and their function mechanism, effect of co-conditioning of Fe₃O₄ nano-particles and acid treatment on settling ability and dewaterability of sludge and their function mechanism, effect of co-conditioning of Fe₃O₄ nano-particles and ultrasonic on settling ability and dewaterability of sludge and their function mechanism.The conclusions that were drawn from experimental results are:1. Fe₃O₄ nano-particles can improve settling ability and dewaterability of normal sludge .The optimum dosage of Fe₃O₄ nano-particles is 1.0g/L. Fe₃O₄ nano-particles cannot improve settling ability and dewaterability of sludge, which is bulking or aging. The function mechanism of Fe₃O₄ nano-particles is that it can increase sludge floc, reduceζ, electric potential of sludge and increase sludge dewatering velocity. When environmental pH is less than 7.2, Fe₃O₄ nano-particles with high surface energy can adsorb sludge material such as protein, colloidal substances, dissolved organic matter and so on. The magnetic field can increase the collision frequency of particles, make the sludge floc become bigger, increase sludge settling velocity and reduce settling volume.2. Co-conditioning of Fe₃O₄ nano-particles and acid treatment shows that it can improve settling ability and dewaterability of normal sludge. With the lowering of pH, the effect on settling ability and dewaterability is more notable. The best experimental conditions are that pH is 2.0 and the dosage of Fe₃O₄ nano-particles is 1.0g/L. The function mechanism of co-conditioning of Fe₃O₄ nano-particles and acid treatment are that it can dissolve EPS and disrupt sludge cells; hence, interstitial water within floc or sludge cells was released. So, water distribution in sludge is changed, and dewatering extent improved. Sulfate with positive charge can reduceζelectric potential of sludge, compress the double layer and make sludge become unstable. In sulfuric acid solution, with ultrasound to disperse Fe₃O₄ nano-particles can increase the probability of collision between sludge floc and Fe₃O₄ nano-particles, make the sludge floc become bigger and increase sludge settling velocity.3. Co-conditioning of Fe₃O₄ nano-particles and ultrasound shows that it can improve settling ability and dewaterability of normal sludge under conditions of suitable ultrasonic frequency and ultrasonic power. The best experimental conditions are that ultrasonic frequency is 25KMz, the ultrasonic power is 100W and the dosage of Fe₃O₄ nano-particles is 1.0g/L. The function mechanism of co-conditioning of Fe₃O₄ nano-particles and ultrasound is that it can alter sludge composition and make the water in sludge change into free water, Fe₃O₄ nano-particles can reduceζelectric potentical of sludge and increase sludge settling relocity.