Basic Research On Preparation And Characterization Of New Biological Carriers And Application In Biological Wastewater Treatment

Along with the research of biological nitrogen removal and biorefractory organic pollutants treatment, some requirements for raising the treating capacity of traditional activated sludge process are provided. So technology enhancing the efficiency of biological methods by increasing microbial activity and biodiversity received increasing attention. Carriers' sludge which has high biomass and biofacies formed in carriers of biomembrance technique. It's performance depend on carriers' performance. At the middle of 90's, suspended carrier biofilm absorption of advantages of fluidized bed and biological contact oxidation process has become one kind of new and high efficient wastewater treatment method. It's principle is add suspended carrier to aeration tank in order to forming microorganism sludge of high biological density, biological activity and rich biofacies in carriers, So the biochemical treatment efficiency is improved. Researches on superior capability suspended carrier become the focal point studied at present.In this paper, we took attapulgite nanoocomposites powder by ultrasonic dispersion into between entrapment method and carrier-bound method by mechanical blending process. Physical physical and biological activity of carries as evaluation index, through improving upon PVF carrier-bound carries, AT-PVF carrier-bound carries was obtained. Then combined SBR with immobilized microbial carriers, Sequencing Batch Adsorption Immobilization Reactor (AI-SBR) was formed. Starting performance, ability of resisting temperature, pH, loads, phenol and Cr⁺⁶ shock, treatment effect of domestic sewage were analyzed, and biological density, distribution characteristics, distribution of microorganism dynamics of microorganism fixed in AT-PVF carrier and pollutant degradation in AI-SBR were studied. New carriers' practicality and performance were determined. Microbial characteristics before and after carrier microbial formed were compared. Application advantage of AI-SBR weas analyzed. Main result as follows: (1) Through attapulgite nanoocomposites was mixed into PVF by ultrasonic dispersion, new immobilized microbial carriers (AT-PVF) was obtained by catalytic, crosslinking and foaming reaction. The best condition were that: PVA: 13%, formaldehyde:PVA: 0.75, H₂SO₄:PVA: 1.0, surfactant :0.5%, AT:0.4%(2) Comparied materialization and biochemical performance of AT-PVF carrier with that of sponge carriers, AT-PVF carrier's microorganism coherence and mass transfer performance were better than sponge carrier's. The tension strength of AT-PVF carrier was 2.38Mpa, which is 1.23 times of sponge carrier's. The pore-size ranges were large, the homogeneous pore of AT-PVF was distributed, and the surface of AT-PVF was roughened. Under steady state conditions, the speed of biofilm cultivation was 5 days which was 2 days faster than sponge carrier's, the removal rate of COD was 96.2% which was 6 % higher than sponge carrier's, the removal rate of ammonia nitrogen was 95.3 % which was 7 % higher than sponge carrier's, and the quantity of sludge was 1.25 times of sponge carrier's.(3) Combined SBR with AT-PVF carrier, AI-SBR was formed. Comparied AI-SBR reactor with SBR reactor, the speed of starting-rate, the removal-rate of pollutants, and the shock resistance were relatively high in AI-SBR. After reactor performance 6 days and 210 days, biological density of AT-PVF carrier were15.2 mg/cm³and 44.3mg/cm³, that was 4-11 times than that of conventional activated sludge. Microorganism carrier has high bological activity, plentiful biofacies, and strong resistance to bad environment.(4) When used AT-PVF carrier in the aeration tank, a two-tier network from top to bottom must be set up. When carrier microbes withed 2-3 cm³ massive and at the filling rate of 60% were added to network, the effect was best. When used AT-PVF carrier in the SBR, Lower network was lied above aeration equipment, higher network was lied between highest water level and lowest water level and vertical network was lied in order to isolation water decanter equipment. Because net carrier microbes can play 'active intercept', the SS concentration of effluent was low. For aeration tank, the burden of secondary sedimentation tank can be reduced, so the sedimentation tank can be omitted. For SBR reactor, precipitation stage can be shorten and omitted, so the period was shorter and the ability of SBR reactor was raised.(5) The process of formation of biofilm can be divided into two parts: reversible adhesion and irreversible adhesion. In first 30 min, reversible adhesion was occurred. When microbe and carriers contacted 40-300min, irreversible adhesion was occurred. After300min, microorganism on carriers began propagation.In reversible adhesion, the change of microbial biomass coherence on carriers with time is related by B = (?). Among them, B_max is maximum microorganismattachment amounts in unit volume carriers, which effect the adsorption rate and attachment amounts. The large numerical is good.αis microorganism coherence constant. The large numerical is good. For AT-PVF carriers, B_max=8.23mg/cm³,α=0.04min^-1.In irreversible adhesion, The change of microbial biomass coherence on carrierswith time is related by B = (?). Among them, B₀ is microorganism attachmentamounts in unit volume carriers at the beginning of irreversible adhesion, which effect the irreversible adsorption rate and final attachment amounts. The large numerical isgood.α'₃ is rate constant of microbial-fixed. The large numerical is good. For AT-PVF carrier, B₀=2.287mg/cm³,α'₃ =0.085min^-1。B_max ,α,B₀ andα'₃ can be used as index to measure service performance of biologicalcarrier.(6)Kinetic experiment showed that removal COD by microorganism fixed in AT-PVF carrier was accord with first-order Monod kinetic reation. At different pH and temperature, The K_COD of AI-SBR reactor was more than that of SBR reactor.Removal ammonia nitrogen by microorganism fixed in AT-PVF carrier was also accord with first-order Monod kinetic reation. The maximum degradation rates Vmax=16.581, half-saturation constant Ks=40.65mg/L in SBR. Vmax=24.078 in AI-SBR, which was 1.5 times than SBR's. It showed that the ammonia nitrogen degradable behavior of AI-SBR was superior. Ks=22.9885mg/L in AI-SBR reactor, which was little than SBR's. It showed that the maximum degradation rates easily attained at a low ammonia nitrogen concentration in AI-SBR.The results show that: AI-SBR which formed by adding AT-PVF carriers into SBR has high removal-rate of pollutants and the shock resistance than SBR. AT-PVF carrier had good ability of resisting temperature, pH, loads and Cr⁺⁶ shock. The intended purpose was reached.