Primary Study On The Application Of Modified Fibers In The Treatment Ofexcess Sludge By Ozonation

With the economical and social development,the production of excess sludge is expanding rapidly following the increase of wastewater. Traditional methods of the treatment and disposal of sludge have shown many disadvantages both in the economy and the environment. As a result, sludge reduction technologies have emerged and ozonation has become a hotspot in this field. In this study, the preparation and surface structures of carbon nanofibers produced by electrospinning from the active component iron DMF solution and PAN precursors were investigated. This novel iron modified fibers were then used successfully as catalysts for the first time in the ozonation sludge reduction process. The integrated sludge reduction system combining catalytic ozonation and aerobic biological treatment was also built in this research.The modified fibers were prepared by electrospinning method. The iron was used as the active constituent of the modified fiber catalysts and the iron content for the modified fibers were 3% and 6%, respectively. The modified fibers were first preoxidized in an atmospheric air at 265℃at the heating rate of 2℃/min, and then in a pyrolyzing furnace under nitrogen atmosphere, were carbonized at the rate of 8℃/min up to 800℃. The structures and morphologies of the modified fibers were characterized by scanning electron microscopy (SEM). The surfaces of the modified fibers were much rougher, and the diameters increase to 500 and 700nm. The X-ray photoelectron spectroscopic analysis (XPS) of surface modification showed that part of bivalent irons were oxidized to ferric irons, and new compounds have been formed including FeOOH、Fe2(SO4)3、Fe2O3、FeO、FeS and so on. The modified fiber catalysts showed catalytic effects both in the sludge reduction at different initial concentrations and in the removal of phenol, the model compound. Under the studied conditions of the initial sludge CODcr 2000 mg/L, ozone input 6.5 mg/L and the flow rate 7L/min, the catalysts with its iron content 6%, showed better catalytic efficiency than those with iron content 3%. The CODcr removal ratio reached 82.3%, which was 2.3 percentages higher than that without catalyst. The analysis of the ozone concentration in the outlet showed that the ozone concentration was almost zero during the first 20 minutes, which indicated the high utility ratio of ozone and rapid degradation of organic compounds in this period. After that, the ozone concentration from the sludge reduction system increased quickly which indicated the existence of refractory compounds and products in the sludge.The sludge after catalytic ozonation was introduced to the aerobic biological circulation system and the integrated sludge reduction circulatory system combining catalytic ozonation and aerobic biological treatment was built the sludge reduction was built. The results showed that ozonation of the sludge had little influence on the efficiency of dissolved CODcr and ammonia Nitrogen removal. It also suggested that the ozonation sludge reduction system contributed little to the removal of total nitrogen and total phosphorus.