| With the rapid development of the national economy, China’s paper mill production is also increasing, along with a large number of paper sewage generated, and pollution load is heavy. When the scale of China’s papermaking wastewater treatment plant in a step by step to expand, paper sludge is not disposed properly because of the cost of paper sludge account for approximately 50% of the waste water treatment cost, resulting in secondary pollution, so that sewage treatment it lost its original meaning in some degree. The moisture content of paper sludge as high as 95% to 99%, and have a large area, how to reduce the footprint and arrive to the effect of "harmless, minimization, recycling", the key is how to reduce the moisture content of sludge cake. But paper sludge have a certain charge, and the dewatering performance of sludge is poor, so how to improve the dewatering performance become a serious problem of paper companies.The key to improve the dewatering performance of sludge is how to condition the sludge, and chemical conditioning becomes a common method that adding chemical drug to sludge, changing the microstructure of sludge to enhance sludge dewatering performance. After examined the character of the sludge from Yuanjiang paper mill in this experiment, ordering suction filtration time and the moisture content of sludge cake as indicators, the optimal technology of organic flocculants cationic polyacrylamide (CPAM), inorganic coagulant polymeric ferric chloride (PFC),cationic surfactant hexadecyl trimethyl ammonium bromide (CTAB) and the combined of CPAM and CTAB are studied.The experiment results showed that the optimal technology of a single conditioner are as follows:the best configuration of CPAM concentration was 0.2%, the best dosage is 0.2% (relative to absolute dry sludge), best stirring intensity is 250r/min, best stirring time is 120s, cake moisture content low to 70.79%; the best dosage of PFC is 0.2%(relative to absolute dry sludge), best stirring intensity is 180r/min, best stirring time is 80s, cake moisture content low to 71.34%; the best dosage of PFC is 10%(relative to absolute dry sludge), cake moisture content low to 70.08%. CPAM and CTAB have a synergistic effect, both the order of dosing and dosing ratio have a certain impact on the dewatering performance of sludge, the sequence of first CTAB and then CPAM could improve the settling properties. When the amount of CPAM is 5% and CTAB is 0.1%, the moisture content decreased to 68.22%.The experimental study the microstructures of sludge cake by adding different conditioners to further investigate the mechanism of sludge dewatering, the result showed that there is a certain relationship between microstructure and dewatering of sludge cake. Low moisture content of uneven surface of the sludge cake, more porosity, loose structure and porous floc presents, helping water to shuttle and improving the dewatering performance of sludge. There is small floc in the high moisture content of the sludge cake. Sludge connected together in large area without significant voids, is not conducive to the removal of moisture. In addition, the main role of CPAM used in paper sludge is charge neutralization, adsorption bridging and flocculation; PFC is primarily to damage sludge stability and the hydrolyzate and sludge have complex reaction, thereby enhancing the role of the sludge settling properties; CTAB is primarily to reduce the surface tension of water and to improve the solubility of EPS in sludge surface, thereby releasing the wate of the sludge cell pellets inside, to achieve the objective of reducing the moisture content of sludge; CTAB and CPAM can play a synergistic effect, mainly because of CTAB release of the wate of the sludge cell pellets inside, decomposition the large particles into small particles, and CPAM can quickly sludge net small particles into groups, to enhance the sedimentation performance of sludge, thereby improving the dewatering performance of paper sludge. |
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