Development of dewatering system for activated sludge by using novel thermosensitive porous hydrogels

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Preparation method of novel thermosensitive porous gels utilizing unique thermosensitive properties of acrylamide derivative polymers and development of dewatering system by using such thermosensitive hydrogels were investigated.1. Novel synthesis of thermosensitive porous gels N,N-diethylacrylamide (DEAA) and N-isopropylacrylamide (NIPAM) were used as primary monomers. These monomers dissolve in water, while their polymers have the transition temperature of about 32ﾟC and 31ﾟC, respectively. In other words, these polymers dissolve in water below these temperatures, while they have hydrophobic properties above these temperatures. The porous gels could be synthesized easily by a radical copolymerization of one of these primary monomers and cross-linker. The structures F could be controlled by the synthesis temperature, the concentration of cross-linker and so on. The porous structures composed of microgel particles of several microns and macro pores were formed clearly at the synthesis … More temperature above 40ﾟC, and the size of gel particles decreased with increasing the cross-linker concentration.2. Swelling and shrinking behaviors The porous gels synthesized above 40ﾟC swelled or shrank very fast without deformation because of the small resistance for permeation of water. The swelling rate of these porous gels was larger several hundred times compared with non-porous gels, and was inversely proportional to the square of the characteristic length of gel. The shrinking rate was comparable to the heat transfer rate.3. Dewatering tests of organic wastewater discharged from a rice washing machine The wastewater of 400mL containing organic materials of about 70000 ppm (the initial water content was about 93%) was dewatered by using the porous gels of 100 pieces which were synthesized at 50ﾟC.The size of gel was 3.5 mm. The gels shrank at 50ﾟC immersed into the waste water at 10ﾟC for 15-30min. The water content could be decreased easily to less than 70% by repeating these procedures 5 times.4. Conclusion By selecting the synthesis condition of thermosensitive porous gels, the dewatering of the organic wastewater by using these porous gels proposed in this research could be attained. The further study for practical application will be needed. Less