Study On The Treatment Of Raw Water By Magnetic Ion Exchange Resin

Based on the significant demand of drinking water safety, this thesis focused on the removal of natural organic matter (NOM) from the raw water. The objective of this research was to evaluate:(1) the dissolving-out behavior of the resin and the pretreatment of the magnetic ion-exchange resin; (2) the removal of NOM in raw water by the resin.By the experiment of dissolving-out of resin, the conclusion could be drawn that the dissolving-out substances of resin increased without the pretreatment of the resin. Thus, appropriate pretreatment of fresh resins is necessary. Acid/base pretreatment on resin could increase the amount of dissolving-out substances and led to rapid dissolution properties. Ethanol extraction pretreatment could significantly reduce the type and amount of dissolving-out substances of resins. By using the GC/MS, it was found that dissolving-out substances of resin were straight-chain alkanes which was used as resin porogen. High temperature of water was beneficial to the dissolving-out of the organic residues in resin matrix to dissolve out. The amount of resin dissolving-out substances and dissolution rate was significantly higher under dynamic conditions than the static. Taking the use of resins in water treatment situations into account, dynamic experiments were more objective to reflect the dissolving out of resin dissolving-out substances. Either way (extraction, mixing) or processing time (30 min,24 h) in ethanol pretreatment had little influence on the dissolving-out of resin dissolving-out substances. The pretreatment method for NDMP by industrial production could be stirring the resin with ethanol for 30 min, than precipitate for 30 min, repeat the process 6 times to achieve the desired results. NDMP was superior to MIEX in terms of type and quantity of the dissolving-out substances of resins. Thus, the NDMP resin can be applied to drinking water treatment.Experiments were conducted using raw water from Tongyu River and effluent after coagulation-sand filtration from the local drinking water plant. According to the result from the adsorption experiment, NDMP resin could successfully remove NOM from water. The rate of the reaction was so fast that it could basically reached equilibrium whitin 30min. NOM from the water samples was concentrated by Reverse Osmosis and further separated into fractions with different hydrophobicity using XAD-8/XAD-4 resins. The experiment results showed that not only hydrophobic and transphilic fractions of NOM had a higher removal rate when treated with NDMP, but also the hydrophilic fraction was difficult to remove when treated by traditional process. Fractions with different MWCO (Molecular Weight Cut-offs) were collected by ultrafiltration membranes. It was found that high-MWCO and medium-MWCO fractions could be removed by NDMP, as well as the Low-MWCO matters which cannot be removed by coagulation process. The remove-rate of NOM was especially high for the fraction with molecular weight between 300Da and 2000Da which was up to 65%. Twenty batches of continuous adsorption experiment showed that the removal rate of NOM by NDMP could be stabilized at 20% in the case of no desorption. The result of pilot-scale batch test of the resin showed that the capacity of adsorption increased significantly to 40% of the CODMn removal after regenerated by 15% NaCl solution mixed with 0.1% NaOH solution. Returning partial resin to regeneration was a better way for CODMn removal which ensured that the water quality could reach China's drinking water hygiene standards (CODMn <3 mg/L).