国外旅游季节性研究综述

旅游季节性是一个旅游研究的常态问题。本文对近年来旅游季节性研究成果进行了综述,有助于深入了解旅游季节性影响因素以及动力机制,尤其指出旅游的季节性对生态环境的影响尤为严重,应格外重视旅游季节性问题,积极发展生态旅游,从而实现旅游地的可持续发展。     

On-line controlling system for nitrogen and phosphorus removal of municipal wastewater in a sequencing batch reactor (SBR)

The objectives of this study were to establish an on-line controlling system for nitrogen and phosphorus removal synchronously of municipal wastewater in a sequencing batch reactor (SBR). The SBR for municipal wastewater treatment was operated in sequences: filling, anaerobic, oxic, anoxic, oxic, settling and discharge. The reactor was equipped with on-line monitoring sensors for dissolved oxygen (DO), oxidation-reduction potential (ORP) and pH. The variation of DO, ORP and pH is relevant to each phase of biological process for nitrogen and phosphorus removal in this SBR. The characteristic points of DO, ORP and pH can be used to judge and control the stages of process that include: phosphate release by the turning points of ORP and pH; nitrification by the ammonia valley of pH and ammonia elbows of DO and ORP; denitrification by the nitrate knee of ORP and nitrate apex of pH; phosphate uptake by the turning point of pH; and residual organic carbon oxidation by the carbon elbows of DO and ORP. The controlling system can operate automatically for nitrogen and phosphorus efficiently removal.     

贵州高原草海湿地土壤有机碳分布特征及其与酶活性的关系

基于时空替代的研究方法,对贵州草海湿地土壤有机碳和氧化还原酶活性分布进行了研究,分析了土壤总有机碳(TOC)和可溶性有机碳(DOC)与土壤酶活性、环境因子之间的关系.结果表明,不同退化梯度湿地土壤中有机碳存在较大的差异,沿着退化梯度表层土壤TOC、DOC含量和脱氢酶(DHA)活性逐渐降低(p0.05),而多酚酶(PPO)活性逐渐升高(p0.05);在垂直剖面上,原生湿地(CH1)和轻度退化湿地(CH_2)土壤TOC先增加后减少,而沼泽化湿地(CH3)和草甸湿地(CH_4)土壤TOC无明显的分层和富聚现象;相关性分析表明,TOC、DOC与PPO显著负相关(p0.01),而PPO与土壤含水率(WHC)、总氮(TN)和硝酸盐(NO-3-N)含量等显著负相关(p0.01),与pH显著正相关(p0.01).以上结果表明,土壤有机碳和酶活性的变化是对湿地退化的响应,湿地退化碳库的损失与PPO活性增加有关,而WHC、TN、NO-3-N和pH是影响PPO活性分布的重要因子.     

Advanced nitrogen and phosphorus removal in A2O-BAF system treating low carbon-to-nitrogen ratio domestic wastewater

A laboratory-scale anaerobic-anoxic-aerobic process (A²O) with a small aerobic zone and a bigger anoxic zone and biologic aerated filter (A²O-BAF) system was operated to treat low carbon-to-nitrogen ratio domestic wastewater. The A²O process was employed mainly for organic matter and phosphorus removal, and for denitrification. The BAF was only used for nitrification which coupled with a settling tank Compared with a conventional A²O process, the suspended activated sludge in this A²O-BAF process contained small quantities of nitrifier, but nitrification overwhelmingly conducted in BAF. So the system successfully avoided the contradiction in sludge retention time (SRT) between nitrifying bacteria and phosphorus accumulating organisms (PAOs). Denitrifying phosphorus accumulating organisms (DPAOs) played an important role in removing up to 91% of phosphorus along with nitrogen, which indicated that the suspended activated sludge process presented a good denitrifying phosphorus removal performance. The average removal efficiency of chemical oxygen demand (COD), total nitrogen (TN), total phosphorus (TP), and NH ₄ ⁺ -N were 85.56%, 92.07%, 81.24% and 98.7% respectively. The effluent quality consistently satisfied the national first level A effluent discharge standard of China. The average sludge volume index (SVI) was 85.4 mL·g^?1 additionally, the volume ratio of anaerobic, anoxic and aerobic zone in A²O process was also investigated, and the results demonstrated that the optimum value was 1:6:2.     

Electrochemical dechlorination of chloroform in neutral aqueous solution on palladium/foam-nickel and palladium/polymeric pyrrole film/foam-nickel electrodes

Electrochemical dechlorination of chloroform in neutral aqueous solution was investigated using palladium-loaded electrodes at ambient temperature. Palladium/foam-nickel （Pd/foam-Ni） and palladium/polymeric pyrrole film/foam-nickel （Pd/PPy/foam-Ni） composite electrodes which provided catalytic surface for reductive dechlorination of chloroform in aqueous solution were prepared using an electrodepositing method. Scanning electron microscope （SEM） micrographs showed that polymeric pyrrole film modified the electrode-surface characteristics and resulted in the uniform dispersion of needle-shaped palladium particles on foam-Ni supporting electrode. The experimental results of dechlorination indicated that the removal efficiency of chloroform and current efficiency in neutral aqueous solution on Pd/PPy/foam-Ni electrode could be up to 36.8% and 33.0% at dechlorination current of 0.1 mA and dechlorination time of 180 min, which is much higher than that of Pd/foam-Ni electrode.     

SRT对于污水脱氮过程中N2O产生的影响

试验采用经过长期驯化,控制污泥龄分别为9d和15d的活性污泥,以实际生活污水为研究对象,考察了不同污泥龄(SRT)对污水脱氮过程中N2O的产生量和转化率的影响.结果表明N2O主要产生于污水脱氮的硝化过程中,而反硝化过程的贡献较少.较短的污泥龄有利于脱氮过程中N2O的产生,9d污泥龄的活性污泥系统产生N2O量是15d污泥龄污泥系统的1.2倍,分别为4.62mg·L-1和3.8mg·L-1.不同污泥龄条件下产生N2O的转化率也有所差别,污泥龄较短的活性污泥系统产生N2O的转化率也较高,分别为11.2%和7.8%.系统经长期在较短的污泥龄下运行,并没有影响系统的脱氮效果,两种污泥龄条件下系统的脱氮率都在96%以上.为了减少污水脱氮过程中N20的产生量,应避免污水处理系统过短的污泥龄,造成污水脱氮过程N2O的产量和转化率的大幅升高.     

温度对短程硝化反硝化的影响

以间歇式活性污泥法(SBR)处理生活污水,系统考察了温度变化对短程硝化反硝化稳定性和硝化反硝化速率的影响.结果表明:在较高哌温度下((28±1)℃),通过实时控制和控制污泥龄在lOd左右,可以成功实现短程硝化反硝化.在此基础上对完全亚硝酸型硝化的污泥(NO2--N/NOx--N≈1)进行降温实验,每降1℃稳定一个多月,半年后不刻意控制温度,经历了冬季lO℃的低温,成功的稳定了常温、低温短程硝化反硝化,亚硝化率始终维持在78.8%以上.实验发现降低温度后对于AOB和NOB的活性都有很大的影响,但对于AOB的影响要大于NOB,对比氨氧化速率的影响大于比反硝化速率的影响.26℃条件下的比氨氧化速率和比反硝化速率分别是10℃条件下的4.49和2.91倍.可见降低温度对于短程系统硝化反应的影响要大于反硝化的影响.     

低C/N比条件下高效生物脱氮策略分析

针对低C/N比污水传统生物脱氮碳源不足、脱氮效率不高,提出从充分利用碳源和减少生物脱氮碳源需求量两个方面,来实现高效生物脱氮.在充分利用碳源方面,介绍了好氧缺氧分段进水工艺、脉冲式SBR工艺等改进型生物脱氮工艺;在减少生物脱氮碳源需求量方面,介绍了短程硝化反硝化、厌氧氨氧化、完全自养脱氮等新型生物脱氮技术.并对这些技术和工艺的原理、优势、存在的问题以及应用情况进行了简要的分析.     

Nitrogen removal via nitrite from municipal landfill leachate

A system consisting of a two-stage up-flow anaerobic sludge blanket (UASB), an anoxic/aerobic (A/O) reactor and a sequencing batch reactor (SBR), was used to treat landfill leachate. During operation, denitrification and methanogenesis took place simultaneously in the first stage UASB, and the e uent chemical oxygen demand (COD) was further removed in the second stage UASB. Then the denitrification of nitrite and nitrate in the returned sludge by using the residual COD was accomplished in the A/O reactor, and ammonia was removed via nitrite in it. Last but not least, the residual ammonia was removed in SBR as well as nitrite and nitrate which were produced by nitrification. The results over 120 d (60 d for phase I and 60 d for phase II) were as follows: when the total nitrogen (TN) concentration of influent leachate was about 2500 mg/L and the ammonia nitrogen concentration was about 2000 mg/L, the shortcut nitrification with 85%–90% nitrite accumulation was achieved stably in the A/O reactor. The TN and ammonia nitrogen removal e ciencies of the system were 98% and 97%, respectively. The residual ammonia, nitrite and nitrate produced during nitrification in the A/O reactor could be washed out almost completely in SBR. The TN and ammonia nitrogen concentrations of final e uent were about 39 mg/L and 12 mg/L, respectively.     

SBR短程脱氮系统中亚硝酸盐积累对生物除磷的影响

采用SBR工艺处理实际生活污水,通过控制好氧段的DO浓度及曝气时间,实现了短程硝化反硝化,并考察了短程硝化引起的亚硝酸盐积累对生物除磷系统的影响.结果表明,在没有补充外碳源的情况下,好氧阶段NO2--N的积累低于10 mg·L-1时,聚磷菌的吸磷及放磷能力没有受到影响,好氧出水磷浓度基本维持在1 mg·L-1以下;当N...