Preparation And Application Of The Carrier Material Used In Sewage Treatment

At present, the carrier material which usually used in the biological membrane treatment sewage is non-biodegradable material that is not easily biodegradable and could cause secondary pollution of the environment. It is not meeting the requirement of economic development in our country. So developing a biodegradable, high porosity and large biological loading amount sewage treatment carrier material has realistic significance.In this paper, poly-lactic acid(PLA) and cellulose acetate(CA) potous carrier metaial were prepared reapectively, by supercritical anti-solvent technology. Microstructure and pore size distribution of the prepared carrier material were detected by means of SEM method. The best preparation technology conditions were obtaioned through the single factor experiment and orthogoical experiment. The optimum technological parameters of PLA porous carrier material were as follows: solution concentration 160 g/L, pressure 12 MPa, temperature 45 oC, CO2 cycle time 90 min and pressure holding time 60 min. On the above conditions the porosity and aperture of PLA porous carrier material were 89.984 %and 160 μm respectively. The optimum conditions of CA porous carrier material were as follows: temperature 45 oC, polymer concentration 120 g/L, CO2 cycle time 120 min,pressure 14 MPa. The porosity of CA porous carrier material obtained under these conditions was about 66.94%.In addition, the PVA and PVA-starch globular carrier material were obtioned by Gle-Chemical cross-linking method, applying Poly vinyl alcohol(PVA) and starch as raw materials. And the effect of various operating parameters on the carrier material performance was also studied in this paper. At the same time, the starch-PVA foam carrier material was prepared by using chemical cross-linking method together with foaming system method. The factors effecting on the performance of the foam carrier material were also studied. Through the experiment, the appropriate preparation technology conditions were obtained, which as follows: starch 0.6 g, 10 % PVA solution 50 mL, foaming agent sodium carbonate 0.5 g, temperature 50 oC,and the solution of sulfuric acid and formaldehyde 4 mL. The apparent density, water absorption, porosity and cross-linking ratio of starch-PVA foam carrier material obtained under the condition was 0.21 g/cm3,14.1 g/g, 77.5 % and 90.2 % respectively. Finally, the simulated wastewater treatment experiment was carried out adopting the carrier materials which prepared under the abovebest conditions. The results were as follows: the average CODCrremoval rate reached93.19 %, and the average ammonia nitrogen removal rate was 59.48 %.