Experimental Study Of Hybrid Immersed Membrane Systme Application On Trace Elements Removal In Groudwater

With the shortage of water resources and the aggravation of water quality all over the world, membrane separation technology and its combined processes have become one of the research focuses in water treatment field. The application of hybrid immersed membrane system on removing trace elements (iron, manganese, ammonium, boron etc.) of groundwater was studied in this dissertation. In this experiment, operational conditions, removal rate, membrane fouling mechanism and so no were discussed and analyzed. The main results were as followings:Two systems of experimental apparatus were set up. One is for oxidation method combined with immersed micro-filtration to remove iron and manganese. The other is for absorption method combined with immersed micro-filtration to remove ammonium, boron and arsenic.In the test of iron and manganese: (1) Through jar tests, the effect of some operational factors were discussed, such as oxidants dosage, reaction time, raw water components, aeration intensity and pH value; (2) In the systematical membrane tests, firstly aeration method without pH value adjustment was verified infeasible for iron and manganese removal. Then without pH value adjustment, strong oxidants NaCIO was also verified not to give satisfied removal rates. But with pH value adjustment ( for 5ppm Fe, pH=7; for 1ppm Mn, pH>10.2), the concentration of effluent can meet the requirement of drinking water quality(Fe<0.3ppm;Mn<0.05ppm). (3) On the above basis, the effects of hydraulic retention time, aeration intensity, interval suction, raw water components on membrane performance and removal rate were analyzed. Which should be pointed out is that the addition of calcium was very effective to mitigate membrane fouling. (4) The effective membrane detergents ( for Fe, HCI; for Mn, HNO3+Ascorbic acid ) were found out. By jar tests, iron and manganese oxidized proportion and oxidation products’size distribution were also analyzed, which provided the theoretical basis for membrane fouling reason analysis. (5) Primary calculation was conducted for 100m3/d treatment according to test results.In the test of ammonium and boron: (1) The effective absorbents for ammonium, boron and arsenic were chosen out respectively through series of jar tests. Their isotherm was simulated by Langmuir and Freundlish models and the saturated absorption quantity were determined. (2) For 10ppm ammonium raw water, the effects of zeolite concentration, aeration intensity, HRT, interval suction were studied. The effect of zeolite concentration and aeration intensity on critical flux were analyzed as well. (3) For 1-2pmm boron raw water, the effects of GRY-L concentration and aeration intensity on critical flux were studied. (4) GRY-L and zeolite as the two different sorbents, their physical characteristics, membrane permeability, sorbents concentration and aeration intensity effect in two different systems were compared.At last, the cross flow rate in immersed tank was calculated through theory model simulation and the hydraulic characteristics was analyzed, which provided the theoretical base for the system optimal design.