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241.
Junhua LI Yue PENG Huazhen CHANG Xiang LI John C. CRITTENDEN Jiming HAO 《Frontiers of Environmental Science & Engineering》2016,10(3):413
Selective catalytic reduction (SCR) of NOx with NH3 is an effective technique to remove NOx from stationary sources, such as coal-fired power plant and industrial boilers. Some of elements in the fly ash deactivate the catalyst due to strong chemisorptions on the active sites. The poisons may act by simply blocking active sites or alter the adsorption behaviors of reactants and products by an electronic interaction. This review is mainly focused on the chemical poisoning on V2O5-based catalysts, environmental-benign catalysts and low temperature catalysts. Several common poisons including alkali/alkaline earth metals, SO2 and heavy metals etc. are referred and their poisoning mechanisms on catalysts are discussed. The regeneration methods of poisoned catalysts and the development of poison-resistance catalysts are also compared and analyzed. Finally, future research directions in developing poisoning resistance catalysts and facile efficient regeneration methods for SCR catalysts are proposed. 相似文献
242.
Jing FENG Yili WANG Xueyuan JI Dongqin YUAN Hui LI 《Frontiers of Environmental Science & Engineering》2015,9(2):352
We investigated the performance of a 15.3 L capacity anaerobic baffled reactor (ABR) toward the treatment of low-strength domestic wastewater. The start-up period of the ABR was finished within approximately 130 days at a temperature below 25°C. The average CODCr in the effluent was 165 mg·L-1, and the corresponding CODCr removal efficiency of the ABR was 52.3%. During the third stage (from day 130 to day 233) of ABR operation, the average CODCr in the effluent reached 71 mg·L-1, which meets the secondary discharge requirement of the Integrated Wastewater Discharge Standard (GB 18918-2002, China). Moreover, partial microbial separation was observed along the five ABR compartments through scanning electron microscopic images. The geometric mean diameter of bioparticles in the five compartments increased from 0.050 mm to 0.111, 0.107, 0.104, 0.110, and 0.103 mm during the start-up stage. After operation for 179 days, the corresponding diameters further increased to 0.376, 0.225, 0.253, 0.239, and 0.288 mm, respectively. The fractal dimensions of the bioparticles indicated that these particles have smoother surfaces and more compact structures during ABR operation. Morphological analysis of the bioparticle sections demonstrated that the bioparticles have a pore volume of 30%–55%. The highest porosity was observed for the bioparticles in the second ABR compartment, whereas the lowest fractal dimension of bioparticle section was observed in the fifth compartment. 相似文献
243.
针对污水处理厂尾水TN去除问题,采用16S rDNA克隆文库法,探究了3DBER-S(三维电极生物膜耦合硫自养脱氮工艺)的强化脱氮机制及其菌群特征. 结果表明,I(电流)和HRT(水力停留时间)对3DEBR-S中氢自养和硫自养反硝化作用所占比例的影响较大,但对脱氮效率影响不显著. 当进水C/N〔ρ(CODCr)/ρ(TN)〕为1、ρ(NO3--N)为35 mg/L、I为300 mA、HRT为4 h时,NO3--N和TN去除率可分别稳定在80%和74%以上. 16S rDNA克隆文库结果显示,反应器中β变形菌纲为优势菌群,占47.89%〔以OUT(操作单元)计〕. 在β变形菌纲中,与具有反硝化功能的陶厄氏菌属(Thauera)相似的细菌所占比例最大,为52.94%;与可分别利用硫和氢为电子供体进行反硝化脱氮的硫杆菌属(Thiobacillus)和食酸菌属(Acidovorax)相似的细菌分别占17.65%和14.71%. 3DBER-S中存在异养联合氢自养和硫自养反硝化协同去除硝酸盐氮的作用,可为反硝化脱氮提供充足的电子供体,节约了有机碳源消耗,并保证了稳定高效的脱氮效果. 相似文献
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以合成废水为研究对象,以丙酸盐为单一外加碳源,通过比较进水中不同Zn2+浓度(0,1,5,10,20mg/L)下单级好氧模式下序批式反应器(SBR)的除磷效果,考察进水Zn2+浓度对单级好氧SBR生物除磷性能的影响,并通过分析各反应器中典型周期内磷及微生物体内储能物质的变化,探究Zn2+对单级好氧SBR生物除磷性能的影响机理.当进水Zn2+浓度为0和1mg/L时,除磷率分别高达96.84%和97.90%.当进水Zn2+浓度为5,10,20mg/L时,系统除磷率分别为89.32%,76.43%和57.29%,说明较高浓度Zn2+对单级好氧SBR生物除磷有抑制作用.结果表明,较高浓度Zn2+可抑制COD的降解,微生物体内聚羟基脂肪酸酯好氧合成及磷酸盐激酶活性,并促进GAOs的代谢,使聚磷合成和水解量减少,从而降低系统的除磷性能. 相似文献
246.
铁基催化剂的微波水热处理对其SCR脱硝性能的影响 总被引:1,自引:0,他引:1
利用微波对共沉淀制备的铁铈钛复合氧化物催化剂前驱体进行水热处理,探讨了微波水热处理对铁基催化剂低温SCR脱硝性能的优化;并对微波水热处理条件的影响进行了正交分析.结果表明:对铁基催化剂前驱体进行微波水热处理,可提高其低温SCR脱硝性能,使其脱硝温度窗口向低温偏移;且微波水热处理的低温优化效果与催化剂中Fe/Ti摩尔比密切相关,Fe/Ti摩尔比越小,微波水热处理的低温优化越强;微波加热方式和微波辐射时间会影响微波水热处理对铁基催化剂SCR脱硝性能的低温优化;在相同微波辐射时间条件下,当P30逐渐变为P80,微波水热处理对铁基催化剂低温SCR脱硝的促进作用降低;在P30条件下,微波辐射15min使铁基催化剂具有最佳低温SCR脱硝活性. 相似文献
247.
248.
Sheng CHANG Jianzheng LI Feng LIU 《Frontiers of Environmental Science & Engineering》2011,5(1):140-148
An anaerobic contact reactor (ACR) system comprising a continuous flow stirred tank reactor (CSTR) with settler to decouple the hydraulic retention time (HRT) from solids retention time (SRT) was developed for fermentative hydrogen production from diluted molasses by mixed microbial cultures. The ACR was operated at various volumetric loading rates (VLRs) of 20–44 kgCOD·m-3·d-1 with constant HRT of 6 h under mesophilic conditions of 35°C. The SRT was maintained at about 46–50 h in the system. At the initial VLR of 20 kgCOD·m-3·d-1, the hydrogen production rate dropped from 22.6 to 1.58 L·d-1 as the hydrogen was consumed by the hydrogentrophic methanogen. After increasing the VLR to 28 kgCOD·m-3·d-1 and discharging the sludge for 6 consecutive times, the hydrogentrophic methanogens were eliminated, and the hydrogen content reached 36.4%. As the VLR was increased to 44 kgCOD·m-3·d-1, the hydrogen production rate and hydrogen yield increased to 42.1 L·d-1 and 1.40 mol H2·molglucose-consumed-1, respectively. The results showed that a stable ethanol-type fermentation that favored hydrogen production in the reactor was thus established with the sludge loading rate (SLR) of 2.0–2.5 kgCOD·kgMLVSS-1·d-1. It was found that the ethanol increased more than other liquid fermentation products, and the ethanol/acetic acid (mol/mol) ratio increased from 1.27 to 2.45 when the VLR increased from 28 to 44 kgCOD·m-3·d-1, whereas the hydrogen composition decreased from 40.4% to 36.4%. The results suggested that the anaerobic contact reactor was a promising bioprocess for fermentative hydrogen production. 相似文献
249.
Rongchang WANG Xinmin ZHAN Yalei ZHANG Jianfu ZHAO 《Frontiers of Environmental Science & Engineering》2011,5(1):48-56
Nitrogen removal performance and nitrifying population dynamics were investigated in a redox stratified membrane biofilm reactor (RSMBR) under oxygen limited condition to treat ammonium-rich wastewater. When the N H 4 + - N loading rate increased from 11.1±1.0 to 37.2 ± 3.2 g N H 4 + - N · m - 2 · d - 1 , the nitrogen removal in the RSMBR system increased from 18.0±9.6 mgN·d-1 to 128.9±61.7 mgN·d-1. Shortcut nitrogen removal was achieved with nitrite accumulation of about 22.3 ± 5.3 m g N O 2 - - N · L - 1 . Confocal micrographs showed the stratified distributions of nitrifiers and denitrifiers in the membrane aerated biofilms (MABs) at day 120, i.e., ammonia and nitrite oxidizing bacteria (AOB and NOB) were dominant in the region adjacent to the membrane, while heterotrophic bacteria propagated at the top of the biofilm. Real-time qPCR results showed that the abundance of amoA gene was two orders of magnitude higher than the abundance of nxrA gene in the MABs. However, the nxrA gene was always detected during the operation time, which indicates the difficulty of complete washout of NOB in MABs. The growth of heterotrophic bacteria compromised the dominance of nitrifiers in biofilm communities, but it enhanced the denitrification performance of the RSMBR system. Applying a high ammonia loading together with oxygen limitation was found to be an effective way to start nitrite accumulation in MABs, but other approaches were needed to sustain or improve the extent of nitritation in nitrogen conversion in MABs. 相似文献
250.