| There would be a series of ecological environment and healthy problems when ammonium nitrogen concentration in river is much higher than normal level. In this paper ammonium was selected as the target pollutant, and ammonium removal by different adsorbents and conversion characteristic of Paracoccus pantotrophus were studied. Entrapped the combination of adsorbent and microorganism by PVA-SA can get composite immobilized microorganism. The preparation conditions were optimized and different methods for microorganism reactivation were compared. The immobilized pellets were used in river water treatment to provide theoretical support for practical application.(1) When the partical size was less than80mesh, four adsorbents had better adsorption effect for ammonia nitrogen than40-60mesh and60-80mesh, and modified corn cob had higher absorption efficiency than other three adsorbents. Changing the adsorbents dosage, when the original ammonium nitrogen concentration was10mg/L, activated carbon had best removal rate which was68.63%and modified corn cob had best unit adsorption quantity which was0.91mg/g. The result of adsorption isotherm equation showed that the saturated adsorption capacity was modified corn cob> zeolite> activated carbon> slag and adsorption ability was activated carbon> modified corn cob> slag> zeolite. When the four adsorbents were used in river water, activated carbon had best adsorption effect for NH4+-N and CODCr with the removal rate19.45%and50.00%, and modified corn cob had best adsorption effect for TN, NO3—-N and NO2—-N with the removal rates7.61%, NO3—-N and NO2—-N100%, and slag had better effect of removing NH4+-N and TN, while poorer effect for CODCr.(2) Under the condition of30℃and150r/min, the growth of microorganism Paracoccus pantotrophus could reach logarithmic phase in4h and stable phase in20h. The suitable conditions for this microorganism growth were temperature30~35℃, initial pH6~10and shaking speed greater than100r/min. The bacteria could utilize glucose and sodium succinate as carbon source but not sodium citrate, and it also could utilize NH4+-N、NO2—-N and NO3—-N as the only nitrogen source for growth. During the processing of ammonia nitrogen degradation by this microorganism, the degradation trends of NH4+-N was in accordance with the bacteria growth, and removal effecet for TN was not obvious, while little NO2—-N and NO3—-N accumulated. This microorganism couldn’t well adapt the nutrition condition of river water, and cell concentration had greatly impact on NH4+-N removal in river water.(3) The spherical efficient of immobiled pellets was all good when SA mass fraction was0.5~1%, PVA mass fraction was8%and crosslinking time was24h. Adding adsorbents in immobiled pellets could influence density, partical size, specific surface area and mass transfer performance of the pellets, and the particle strength pellets and stability of these pellets with different adsorbents were good. The methods of using river water for immobilized microorganism to recover activity was effective, the process of reactivation by culture medium was slowly and simulated wastewater was unfavorable for the immobilized pellets to maintain spherical. When dosing the four pellets in river water under the conditions of30℃and100r/min, PSLW and PSYW could achieve equilibrium state in10hours, and among the ammonia nitrogen concentration of the water treated by four pelltes after24h, PSLW was the lowest, PSLW and PSYW were lower with the concentration below1mg/L, while the ammonia nitrogen concentration by PSW was1.6mg/L. The removal rates of TN, NO3—-N and NO2—-N by PSLW and PSLYW were all more than90%, while CODCr was rise because of PVA and SA dissolving out, therefor it need to improve the immobilized method to improve the pellet’s long-term stability. |
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