Study On The Characteristics And Control Of Membrane And Resin Contamination Of Electrodeionization Process

The characteristics and controlling techniques of fouling in the electrodeionization system was experimentally researched in the test. The results showed that pretreatment only adopt stair RO and then it can satisfy influent requested of EDI, and fouling was very small to module when with the tap water(after salt content low surface water processing) as the water source. With the ground water, surface water or reclaimed water as the water source and module was polluted easily if adopt stair RO, so it must adopt second grade RO which can prevent effectively fouling. During the period of circulating, the chemistry fouling took place most easily and next was organic fouling and bio-fouling. No matter which one kind contaminate once took form, product water conductivity rise quickly, out water quality being changed into a dirty trick. A break point existed on each time-output electric conductivity curves of the three kinds of pollution. It can be considered as the time of cleaning. Reach by the fact that apparent, infrared-spectrum, scanning electron micrograph and X-ray diffractomety carried out analysis on the membrane and resin: The pole water room was easy to encrust. The microorganism of overcast resin in fresh water room easy to be adhered, be happened by the organic and the microorganism contaminate. Hardness ions such as Ca2+, Mg2+ was easy to accumulate, chemical fouling happened on sun resin. The sun film in concentrated room was easy to organic and microorganism happened contaminating and overcast film was easy to chemical pollution happened. The test adopted the laboratorial devices to clean EDI system shows that 2%HCl was best cleaning-scheme of chemistry fouling, organic fouling was 5%NaCl/1.6%NaOH and bio-fouling was 5%NaCl→0.4%H2O2→5% NaCl+1% NaOH. When EDI was in rest for a long time, it should be disinfected and using peroxyacetic acid was the most reasonable. Finally, the test results of industrial experiment showed that the apparatus of pretreatment was in un-appropriately operation or the dead angles exist in the center water-tanks and pipes, which were the main reasons causing the system bio-fouling. The high contents of hardness were the main reasons causing the system chemistry fouling. The best effect can be obtained by the cleaning methods of"acid washing + salt water washing + disinfecting + alkali washing"for synthesis pollution of the EDI system in the experiment.