Application of Functional Polymer Gels to Water Quality Control Systems

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(1) Development and Control of a Chemical ValvepH-responsive functional gels were synthesized by N-isopropylacrylamide (NiPAAm) with methacrylic acid, in order to examine swelling characteristics of the gels and to develop a chemical valve which can control a flow rate of air in an aeration tank. The proposed chemical valve could control the flow rate of air in distilled water. However in sewage the pH-responsive functional gels swelled and shrank slightly with large pH-stimuli. There- fore it was difficult to control the flow rate of air by the chemical valve in a solvent with high ionic strength like sewage. This indicates that new pH-responsive functional gels should be synthesized, otherwise new types of chemical valves should be proposed. In this research, a chemical piston with pH-responsive gel beads was pro- posed as a new type system.(2) Kinetic and Biological Studies on Volume Phase Transition Processes ofElectro-Responsive Functional Gels Electro-responsive functional gels s … More ynthesized by PVA-PAA, were examined on bending characteristics un- der an electric field. The gel responded quite rapidly to electro-stimuli, in comparison with thermo- or pH-respon- sive functional gels. Bending of the gels took place toward the negative electrode within several seconds to min- utes. The PVA-PAA gel was utilized as an immobilization medium for denitrification microorganisms in waste water treatment systems.(3) Application of Functional Gels to Increase in Rate of Biological NitrificationA method to increase the nitrification rate with an advantage of the immobilization technique was developed. NiPAAm was adopted as a functional gel which shrinks and swells reversibly depending on the change of tem- perature, e.g., a thermo-responsive gel. Effects of the volume phase transition of the gel on the nitrification activ- ity were studied. Nitrifiers were immobilized in the gel, and pellets of it were incubated under a cyclic thermal operation between 25 and 35 C.It was compared with the nitrification activity by nitrifiers immobilized in the gel under three isothermal operations at 25, 28 and 35 ﾟC.In conclusion, the nitrification activity is enhanced by utilization of the thermo-responsive gel. Under the cyclic thermal operation, a drastic increase in the rate of nitrification occurs due to a "pumping effect" caused by the volume phase transition of the thermo-responsive gel. The evaluation of nitrifiers' distribution in the gels by FISH agreed with this phenomenon. Less