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Fundamental Study Of Short-cut Nitrification-denitrification Biological Nitrogen Removal And Denitrifying Phosphorus Removal

Posted on:2005-05-24Degree:DoctorType:Dissertation
Country:ChinaCandidate:X L ZhangFull Text:PDF
GTID:1101360122486295Subject:Environmental Engineering
Abstract/Summary:PDF Full Text Request
Biological nutrient removal processes were introduced into wastewater treatment because nitrogen and phosphorus induced eutrophication of closed water bodies. However conventional biological nutrient removal processes exist some problems such as system complex, large footprint, high investment, and etc. Short-cut nitrification-denitrification, simultaneous nitrification-denitrification and denitrifying phosphorus removal are novel biological nutrient removal technologies. The processes have many advantages, such as high efficiency, energy saving and less sludge etc. So these new technologies are being paid more and more attention by environmental engineering experts.In this paper, short-cut nitrification-denitrification was studied in the attached growth system (Biological Turbulent Bed Reactor, BTBR) and suspended growth system (Sequencing Batch Reactor, SBR), respectively. In addition, simultaneous nitrification-denitrification and denitrifying phosphorus removal were studied in SBR reactor. From the experiments I get the main conclusions as follows.(1) In a BTBR, DO concentration was controlled between 0.5 and 1.0mg/L and 300mg/L of ammonium nitrogen was filled, the 80% of nitrite could be reached stably; 90% of ammonium was removed at 25℃, the value of pH 7.2-8.0. The MPN test showed that ammonium oxidizers had dominated in the biofilm at the end of dynamic selection under low DO concentration.(2) The effect of organic carbon concentration on short-cut nitrification was also studied in BTBR. The results showed that nitrification system was destroyed with DO=0.5~1 .0mg/L TOC >100mg/L and TOC/N=1:3, because nitrifiers couldn't compete for DO with heterotrophic bacteria.(3) The alternation of low DO concentration and high DO concentration was the key factor for a successful short-cut nitrification in an SBR. Ammonium oxidizers had feast-famine abilities,so it could endure the fluctuation of DO and survived in the reactor, but nitrite oxidizers did not.(4) Effects of DO concentration and feed mode of organic carbon on simultaneous nitrification-denitrification were studied. The aerobic zone and anoxic zone coexisted in a floe, so nitrification and denitrification took place simultaneously at low DO. Feed mode of organic carbon influenced the efficiency of nitrogen removal. 80% of nitrogen removal efficiency could be reached at 300 mg/L of ammonium nitrogen and 600mg/L of COD using batch feed mode .(5) Nitrate concentration was one of the factors affecting the denitrifying phosphorus removal. Generally, a higher Nitrate concentration benefits denitrifying phosphorus removal. But when the Nitrate-nitrogen concentration was enhanced over 20mg/L, the phosphorus removal efficiency couldn't be improved. At the same Nitrate concentration, denitrifying phosphorus removal efficiency could be promoted with the increase of anoxic time. In order to keep steady phosphorous removal efficiency and sludge settle ability, an aerobic stage should be added following anoxic stage.(6) Nitrite can be used as electron acceptor in denitrifying phosphorus removal. Feed mode of nitrite had significant influence on denitrifying phosphorus removal. Anoxic phosphorus assimilation rate could be reached 10.44mgP/gSS-h after 23 days with continues feed mode.(7) Sludge granular with denitrifying phosphorus removal activity was cultivated In an SBR. The effects of different operational conditions on formation of granular were studied such as COD loading, settling time, HRT and shear force. The dimension of granular was between 50 m and 900 m,. Its water content was at 96.78% -98.14%, specific gravity 1.022-1.006, SVI of sludge 25~40mL/g, COD removal loading could be reached to 1.496kgCOD/m3-d, nitrogen and phosphorus removal loading could be reached to 0.21 kgN/m3-d and 0.06kgP /m3-d respectively.
Keywords/Search Tags:short-cut nitrification-denitrification, denitrifying phosphorus removal, simultaneous nitrification-denitrification, the attached growth system, the suspended growth system, low DO, BTBR, SBR.
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