The Application Of Carbon Fiber In Water Purification And Ecological Restoration

In recent years, the surface water suffered from pollution to various degree,especially from eutrophication pollution. The water body function and socialenvironment was destroyed by the polluted water. Carbon fiber was a new type ofenvironmental material and was gave gradually attention in the treatment ofwastewater field. This thesis researched on these problems: the characteristic,mechanism and influencing factors of water purification with carbon fiber treatment;the change population structure of algae, especially the inhibitive effect of blue-greenalgae bloom when carbon fiber existed. The author devised a new method to removenitrification and phosphorus simultaneously by the combination method of biofilmand ferric-carbon micro-electrolysis.(1) Using carbon fiber as biofilm carrier, biological membrane grew mature afteronly three days; carbon fiber had a high adsorbability and biocompatibility, so biofilmwas formed quickly and it could removed nitrogen and phosphorus effectively; thesurface of microbial morphology was in a good state and the removal rate of turbidityvalue, TN, TP, NH4+-N could respectively reach90%,40%,60%,98%. There was asignificant correlation between TN and turbidity value (r=0.912, P<0.01). TP andturbidity value were also significantly positive correlation (r=0.918, P<0.01). Thecorrelations indicated that the removal mechanism of the TN and TP were mainly theadsorption of carbon fiber. Signification correlation was found between PO42--P andNO3--N (r=0.856, P<0.01) and the phenomenon might be caused by P release fromanaerobic environment in the inlayer of biofilm.(2) The acidic environment had inhibitory action on the removal of NH4+-N andTP, and their removals were fully suppressed at pH5. The alkaline environmentexerted a big impact on the removal of TOC. Slight alkaline condition (pH at7~8)was good to remove pollutants. Optimum condition for biodegradation of wastewaterwas DO5~5.8mg/l, HRT6~8hours and pH7~8. Adding carbon sources had noeffect on NH4+-N removal, but it improved effectively the removal efficiency of TN,TP and TOC.(3) The biofilm on carbon fiber had a variety of effects on ecological restoration.The ratios of the algaes were changed, the reproduction of blue alga were inhibitedand the bio-diversity were improved when the water was treated by carbon fiber. The time that the cell density of cyanobacteria reached maximum was6days later and theratio of cyanobacteria decreased from47.2%to22.4%when the biofilm existed. Thespecies of alga were mostly diatoms (Melosira sulcata) in the water treated by biofilmand the control water were mostly blue algaes (Oscillatoria tenuis) without treatment。(4) Ferric-carbon Micro-electrolysis could improve remarkably the removaleffect of TN and TOC, and it had no obvious effect on TN. The average concentrationof TP was less than0.1mg/L after treated. The removal rate of TP increased from23.0%to93.3%and the removal rate of TOC increased from24.7%to37.5%whenwastewater was treated by Micro-electrolysis. The removal effect of TP was stable,but the removal efficiency of TOC had a maximum value. The removal rate of TOCwas in decline after the increase, and the reason of this phenomenon might be theextention of the electrolytic reaction.