Study On The Preparation Of PVA Immobilized Particles Composited With Acacia Fiber And Its Treatment On Model Ammonia Nitrogen Wastewater

With the rapid process of urbanization and the growth of population, waterpollution has become one of the main environmental problems. Compared withsuspended biological treatment methods, immobilized microorganism technology forwastewater treatment has a lot of advantages, such as high processing efficiency,strong stability, less sludge, good solid-liquid separation effect, high-densitymicroorganism, strong capacity of anti-shock loading, etc. Immobilization methods,reaction conditions and carrier materials are the key to be widely used.In this thesis, a new type of immobilized carrier was prepared by chemicalcrosslinking method. This new carrier was acacia fiber-PVA immobilized particle,which was added the acacia fiber and used polyvinyl alcohol as skeleton. By testingelasticity, compression strength, specific surface, the synthetic process conditions ofacacia fiber-PVA immobilized particles were determined: at room temperature, with4%(wt) boric acid,1%(wt) sodium alginate,CaCl2as inorganic salt crosslinking agentand12h as crosslinking reaction time, the immobilized particles had better physicaland chemical properties. At this time, the specific surface was62.02m2/g, and thecompression strength was0.5101MPa.When PVA was5%(wt), acacia fiber whichless than0.105mm was about0.9%(wt),the specific surface was29.1%up and thecompression strength increased by9.8%.Efficient denitrifying bacteria was obtained by increasing ammonia nitrogenconcentration of wastewater and using SBR process, providing efficient bacteria forimmobilized particles. Results showed that, when the concentration of ammonianitrogen was50mg/L,100mg/L,150mg/L,200mg/L,250mg/L,300mg/L and350mg/L,the removal rate of ammonia nitrogen reduced at the7th cycle in eachconcentration range. After34days of domestication, when the concentration ofammonia nitrogen was350mg/L,the removal rate was above95%and the number ofnitrifying bacteria was increased from1.1×107MPN/mL to2.0×108MPN/mL, marking the domestication process was completed.The optimal entrapment conditionswere ensured by orthogonal experiment method, ammonia nitrogen removal rate asindex：PVA was5%(wt), microbial package(the ratio of weight between concentratedefficient denitrifying bacteria solution and liquid gel) was1:2.0, crossing time was12h, fiber was1.2%(wt).Under different aeration intensity, temperature and pH, the free bacteria, un-fiberimmobilized particles and acacia fiber-PVA immobilized particles had differentremoval efficiency. The experimental results showed that: under the condition of30℃, pH=7.0,15%of filling rate, when rotate speed was more than120r/min,thethree’s removal rate got above98%.Within0~110r/min, when the rotate speed ofvibrator got the same value, the ammonia nitrogen removal rate of the acaciafiber-PVA immobilized particles was higher than un-fiber immobilized particles’.Under the condition of pH=7,120r/min,15%of filling rate, when the temperatureranged from10℃to25℃, the ammonia nitrogen removal rate ofthe acacia fiber-PVAimmobilized particles was the highest, the un-fiber immobilized particles’was thesecond, and the the free bacteria’was the last. Under the condition of30℃,120r/min,15%of filling rate, the optimum temperature of free bacteria was7.2~8.2,and un-fiber immobilized particles’s was6.7~8.2,fiber immobilized particles’was6.2~8.2.This suggested that the immobilization enhanced the microbial toleranceof pH changes,and it also illustrated that adding acacia fiber could improve thisadvantage.