| The water in some areas of China by the heavy metal cadmium pollution, purified water treatment technology in water supply plant, most of cadmium in raw water gathered in the mud water. On cadmium pollution of sludge water reuse, water treatment plant will increase risk of water cadmium concentration exceed the standard. In order to reduce the concentration of cadmium in the supernatant of sludge, sludge to ensure safe reuse,this paper use six mixer,cadmium contamination on the atificial sludge "broken reflocculation" experirnent.Through the study of sludge in "broken reflocculation" influence on the condition of cadmium migration process, in-depth study of the "broken rcflocculation" in the process of cadmium in sludge solid -liquid phase transfet two transformation rules, put forward on the basis of strengthening method of removing cadmium in water mud. sludge water tap water security the factory safe reuse. The result shows:(1) was found that the "brcakcn-rcgrowth"was beneficial to the decrease of cadmium concentration in the supenatant. the process of floe breaken and reflocculation can adsorb some cadmium.the removal efficiency of cadmium is related to the breaking strength, breaking strength of the greater the cadmium removal effect is better,The best crushing strength is 600rpm. In rcgrowth proces the contribution of cadmium removal in the 1.3～1.9μg/L range.the removal rate was about 7.9%～11.5%.(2) The change of pH has a greal influence on the migration of cadmium,mainly due to the greater solubility of cadmium in pH solution. High pH is beneficial to reduce the concentration of cadmium, and low pH is unfavorable to the removal of cadmium, even the risk of desorption.(3) In the process of floc"breakcn-rcgrowth", adding appropriate amount of flocculant can decrease the concentration of cadmium in supernatant, there is an optimum range of flocculant dosage. The optimal dosage range of ferric sulfate and aluminum chloride was about 4mg/L and 3mg/L. repectively, the removal of cadmium was 2μg/L and 1.5μg/L,the removal rate increased by 12.1% and 9.1%, respectively. The optimal dosage of PFS and PAC was 2mg/L and 5mg/L, respectively. The removal of cadmum 1.6μg/L and 0.9μg/L,the removal rate increased by 9.7% and 5.5%, rapectively. An excess of flocculant can lead to the release of adsorbed cadmium. The effects of anions and cetions on PAM are different, the addition of anionic PAM had no effect on the removal of cadmium in the process of "breaken-regrowth"and cationic PAM was not conducive to the removal of cadmium.(4) The main content of cadmium in sewage sludge is iron and manganese oxides,in the"breaken-regrowth"process, the decrease of cadmium concentration in the supernatant was mainly due to the increase of the content of iron and manganese oxides in the sludge, After adding flocculant in sludge water, the changes of cadmium is mainly between in the supernatant and iron manganese oxide combination . When PAM was used to regulate the sludge, the unstable cadmium ions and some iron and manganese oxides in the sludge were converted to organic bound cadmium.(5) Molecular diffusion model is the main outcome on the adsorption process of cadmium by sewage sludge , combined action of many kinds of dynamics mechanism; After adsorption saturation, continue to stir the cadmium release process of quasi level rate equation on the outcome of combined action of many kinds of dynamics mechanism. Raise the temperature is bad for sludge adsorption of cadmium.Finally, according to the results and analysis of the experiment, some suggestions for improvement of the existing wastewater reuse process in waterworks are put forward in the light of cadmium pollution in some water sources. |
PDF Full Text Request