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41.
以红薯浸泡液为碳源的生物反硝化 总被引:3,自引:1,他引:2
为选择低碳氮比污水生物脱氮中合适的碳源,以搅拌罐浸泡淀粉类物质释放碳源,在确定利用红薯浸泡液为碳源后,以浸没式生物滤池为反应器进行生物反硝化实验。实验结果表明:20 g红薯置于2 L自来水中,采用250 r/m in的搅拌速度,搅拌频率为每搅拌3 h停1 h,2 d后得到的浸泡液COD浓度平均为5 921 mg/L,最高可超过7 000 mg/L;将此红薯浸泡液和污水以1∶50的流量比例,采用分别投加的方式进入反应器,污水中总氮、硝酸盐氮、亚硝酸盐氮及氨氮的平均去除率分别为88.6%、91.6%、88.2%和54.8%,出水COD平均在30 mg/L以下;在红薯浸泡液COD浓度为5 700 mg/L左右时,进水中亚硝酸盐氮浓度与硝酸盐氮浓度比为3∶2时总氮去除率为95.3%,当该比例为2∶3时总氮去除率为88.2%。研究表明,红薯浸泡液是一种经济合适的碳源,采用红薯浸泡液作为低碳氮比污水生物处理中反硝化的碳源是可行的。 相似文献
42.
以碘吸附值为裂解残渣吸附性能的指标,通过单因素实验和正交实验,确定了制备裂解残渣的最佳工艺条件,并对残渣的表面元素组成、孔结构组成、晶相组成和吸附性能等性质进行了表征。结果显示:以浓度均为5 mol/L的ZnCl2和H2SO4作活化剂、复配比2∶1、活化温度600℃、活化时间1 h、固液比1∶2.5,制得的裂解残渣酸洗后碘值平均值可达892.8 mg/g;用制备的裂解残渣对苯酚废水进行处理,室温下振荡5 min,苯酚去除率即可达到87.9%,且符合Langmuir吸附等温线方程和Freundlich吸附等温线方程。 相似文献
43.
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
44.
长三角农田土壤中滴滴涕的污染特征与生态风险 总被引:1,自引:0,他引:1
以长江三角洲地区农田土壤为研究对象,分析了土壤和蔬菜中滴滴涕(DDTs)的残留水平和空间分布特征,评估了DDTs对土壤生态和人体健康的潜在风险。结果显示,长三角地区农田土壤中DDTs含量范围为0.2~3 520 ng·g-1,平均63.8 ng·g-1,主要残留在土壤耕作层(0~30 cm)。土壤中DDTs及其代谢产物残留量较低,98.5%的点位土壤符合《中国土壤环境质量标准》的二级标准。15%的蔬菜样品中检出DDTs,其浓度为相应土壤DDTs浓度的9%~18%,土壤残留的DDTs通过食物链进入人体导致的健康风险很小。低残留DDTs对土壤微生物的群落结构和多样性无显著影响(-0.25R0.25,0.307P0.979)。应用美国环保署(USEPA)方法评估了土壤中DDTs对人体的健康风险,其中致癌风险级别为非常低,对儿童和成人具有非致癌风险的样品比例分别为1.1%和0.7%。因此,长三角地区大多数点位农田土壤DDTs残留量较低,不会对生态环境和人体健康产生危害。 相似文献
45.
小麦根系菲与磷吸收及转运的相互作用 总被引:1,自引:0,他引:1
作物根系对多环芳烃(PAHs)与磷吸收及转运之间的相互作用研究对农产品的安全生产和PAHs污染环境植物修复的强化具有重要意义。为此,本文以菲为PAHs的代表,采用水培试验研究了不同磷、菲水平下小麦根系菲、磷吸收及其转运的效果,旨在揭示植物根系吸收PAHs与磷素的相互作用。结果表明,在0~1 200μmol·L~(-1)磷浓度范围内,小麦根系、茎叶菲含量在低磷浓度(10μmol·L~(-1))时最高,分别为36.87 mg·kg~(-1)和2.07 mg·kg~(-1);磷含量总体呈现随磷处理浓度的升高而增大的趋势;成对数据t-检验显示无论加菲与否,根系、茎叶磷含量无显著性差异(P0.05)。磷可促进菲从根部向地上部转运,而菲对磷转运没有显著性影响。在低磷浓度下(10μmol·L~(-1)),随着菲浓度的升高,小麦根系、茎叶菲含量呈现显著升高趋势(P0.05)。磷、菲共存处理介质pH升高幅度大于单一处理。 相似文献
46.
Xiaoya Liu Yu Hong Peirui Liu Jingjing Zhan Ran Yan 《Frontiers of Environmental Science & Engineering》2019,13(5):78
47.
Yang Li Yixin Zhang Guangshen Xia Juhong Zhan Gang Yu Yujue Wang 《Frontiers of Environmental Science & Engineering》2021,15(1):1
48.
Jantsje M. van Loon-Steensma Pieter A. Slim Mathieu Decuyper Zhan Hu 《Journal of Coastal Conservation》2014,18(4):415-430
This paper explores the impact of erosion and restoration measures on habitat development and on wave damping by a small salt marsh nestled alongside a dike on the Wadden island of Terschelling. The aim is to advance knowledge about the benefits and possible side-effects of salt-marsh restoration. Analysis of a time series of aerial photographs from 1944 to 2010 indicates that the salt marsh decreased steadily in size after maintenance of accretion works was terminated. In the western part of the marsh, which is accessible to sheep, vegetation is low (5–15 cm) and dominated by Salicornia europaea and by Spartina anglica. In the most intensively grazed parts, vegetation is very scarce. The eastern, inaccessible part of the salt marsh is covered by dense patches of the shrubby perennial Atriplex portulacoides and Spartina anglica (15–25 cm in height). SWAN wave models show that wave height at this location is significantly affected by the areal extent of the salt marsh as well as by the vegetation. High or dense vegetation are in the models nearly as effective in damping waves (with an initial height of 0.15 and 0.5 m) as widening the salt-marsh area by 350 m. A low density of low plants, as observed in the grazed part of the marsh, has almost no wave-damping effect. Even under conditions of sea level rise, a broader salt marsh vegetated with high plants significantly affects modelled wave height. Therefore, salt-marsh restoration is an adaptation measure worth exploring, though an array of effect types must be considered. 相似文献
49.
Lei Shen Yuntao Guan Guangxue Wu Xinmin Zhan 《Frontiers of Environmental Science & Engineering》2014,8(5):776-783
Nitrous oxide (N2O) is a greenhouse gas that can be released during biological nitrogen removal from wastewater. N2O emission from a sequencing batch reactor (SBR) for biological nitrogen and phosphorus removal from wastewater was investigated, and the aims were to examine which process, nitrification or denitrification, would contribute more to N2Oemission and to study the effects of heterotrophic activities on N2O emission during nitrification. The results showed that N2O emission was mainly attributed to nitrification rather than to denitrification. N2O emission during denitrification mainly occurred with stored organic carbon as the electron donor. During nitrification, NaO emission was increased with increasing initial ammonium or nitrite concentrations. The ratio of N2O emission to the removed ammonium nitrogen (N2O- N/NH4-N) was 2.5% in the SBR system with high heterotrophic activities, while this ratio was in the range from 0.14% to 1.06% in batch nitrification experiments with limited heterotrophic activities. 相似文献
50.
Three metallised azo dyes were investigated under TiO2‐photocatalytic and photosensitised conditions in aqueous buffering solutions. The degradation follows apparent first‐order kinetics. The size and strength of intramolecular conjugation determine the light‐fastness of the investigated dyes. Compared with 1O2 produced in photosensitised process, the more powerful *OH radicals in TiCO2 photocatalytic process are highly reactive towards the investigated azo dyes. And as a result, the TiO2‐photocatalysis makes little less distinction in the degradation kinetic data of the azo dyes compared with the photosensitised degradation of them. 相似文献