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71.
The maximum specific growth rates of both ammonium oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB) were investigated under varying aerobic solids retention time (SRTa) and in the presence/absence of anoxic (alternating) conditions. Two bench SBRs, reactor R1 and R2, were run in parallel for 150 d. Reactor R1 was operated in aerobic conditions while R2 operated in alternating anoxic/aerobic conditions. The feed (synthetic wastewater), temperature, hydraulic retention time and mixing were identical in both reactors. The SRTa in both reactors was, sequentially, set at four values: 5, 4, 3 and 2 d.Kinetic tests with the biomasses from both reactors were carried out to estimate the maximum specific growth rates (μmax) at each tested SRTa and decay rates, in both aerobic and anoxic conditions. The kinetic parameters of nitrifier were estimated through the calibration of a two step nitrification-denitrification activated sludge model.The results point to a slightly higher μmax,AOB and μmax,NOB in alternating conditions, while both μmax,AOB and μmax,NOB were shown not to vary in the tested range of SRTa (from 2 to 5 d) at 20 °C. They were relatively high when compared to literature data: 1.05 d−1 < μmax,AOB < 1.4 d−1 and 0.91 d−1 < μmax,NOB < 1.31 d−1. The decay coefficients of both AOB and NOB were much higher in aerobic (from 0.22 d−1 to 0.28 d−1) than in anoxic (0.04 d−1 to 0.16 d−1) conditions both in R1 and R2, which explained the higher nitrification rates observed in the alternating reactor. 相似文献
72.
The ecotoxicity of silver nanoparticles (Ag-NPs) to wastewater biota, including ammonia oxidizing bacteria (AOB), is gaining increasing interest as the number of products containing Ag-NPs continues to rise exponentially and they are expected to accumulate in wastewater treatment plants. This research demonstrated that the addition order of Ag-NP and the media constituents had a profound influence on the stability of the Ag-NP suspension and the corresponding repeatability of results and sensitivity of Nitrosomonas europaea. N. europaea, a model AOB, was found to be extremely sensitive to ionic silver (Ag+) and two sizes of Ag-NPs (20 and 80 nm). Ag+ exposures resulted in the highest level of toxicity with smaller Ag-NPs (20 nm) being more toxic than larger Ag-NPs (80 nm). The increased sensitivity of N. europaea to smaller Ag-NPs was caused by their higher rates of dissolved silver (dAg) release, via dissolution, due to a greater surface area to volume ratio. dAg was shown to be responsible for the vast majority of the observed Ag-NP toxicity, as determined by abiotic Ag-NP dissolution tests. For the sizes of Ag-NP studied (20 and 80 nm), there appears to be a negligible nanoparticle-specific toxicity. This was further supported by similarities in inhibition mechanisms between Ag+ and Ag-NP, with both causing decreases in AMO activity and destabilization of the outer-membrane of N. europaea. Finally, equal concentrations of total silver were found to be tightly associated to both Ag+ and Ag-NP-exposed cells despite Ag-NP concentrations being five times greater, by mass, than Ag+ concentrations. 相似文献
73.
Impact of biochar application to a Mediterranean wheat crop on soil microbial activity and greenhouse gas fluxes 总被引:16,自引:0,他引:16
Castaldi S Riondino M Baronti S Esposito FR Marzaioli R Rutigliano FA Vaccari FP Miglietta F 《Chemosphere》2011,85(9):1464-1471
Biochar has been recently proposed as a management strategy to improve crop productivity and global warming mitigation. However, the effect of such approach on soil greenhouse gas fluxes is highly uncertain and few data from field experiments are available. In a field trial, cultivated with wheat, biochar was added to the soil (3 or 6 kg m−2) in two growing seasons (2008/2009 and 2009/2010) so to monitor the effect of treatments on microbial parameters 3 months and 14 months after char addition. N2O, CH4 and CO2 fluxes were measured in the field during the first year after char addition. Biochar incorporation into the soil increased soil pH (from 5.2 to 6.7) and the rates of net N mineralization, soil microbial respiration and denitrification activity in the first 3 months, but after 14 months treated and control plots did not differ significantly. No changes in total microbial biomass and net nitrification rate were observed. In char treated plots, soil N2O fluxes were from 26% to 79% lower than N2O fluxes in control plots, excluding four sampling dates after the last fertilization with urea, when N2O emissions were higher in char treated plots. However, due to the high spatial variability, the observed differences were rarely significant. No significant differences of CH4 fluxes and field soil respiration were observed among different treatments, with just few exceptions. Overall the char treatments showed a minimal impact on microbial parameters and GHG fluxes over the first 14 months after biochar incorporation. 相似文献
74.
河水BOD1~20与反应速率常数K的初探 总被引:1,自引:0,他引:1
实验证明,由于无锡水域中硝化菌的存在,使BOD硝化阶段大为提前。因此当水体含氮有机物丰富时,硝化因素应予以重视。 相似文献
75.
表面流人工湿地硝化和反硝化强度研究 总被引:11,自引:0,他引:11
通过对表面流人工湿地不同土壤层硝化反硝化强度的研究,探讨了表面流人工湿地脱氮过程中沿程硝化和反硝化作用的变化,以及不同C∶N对系统反硝化强度的影响.研究结果表明,系统可同时进行硝化和反硝化作用,硝化强度具有较明显的分层现象,表层土壤高于深层土壤.系统中沿程硝化强度呈递减趋势,硝化强度反映了氨氮去除率的大小,其去除率为68%.反硝化强度研究结果表明:深层土壤的反硝化强度略高于表层土壤;沿程1/3至1/2段最大;5倍碳源时反硝化强度最高,3倍碳源次之,不加碳源最低;但系统的反硝化强度普遍较高,保持了良好的脱氮效果. 相似文献
76.
77.
采用室内培养实验的方法,以不加抑制荆的尿素作为对照,对比研究DMPP及它的同分异构体3,5-二甲基吡唑磷酸盐作为硝化抑制剂对尿素氮在土壤中转化的影响。结果表明,3,5-二甲基吡唑磷酸盐具有一定的硝化抑制作用。在培养期间。施加3。5-二甲基吡唑磷酸盐的土壤中硝态氮的含量一周后始终低于对照,铵态氮的含量一周后始终高于对照。但在培养试验中后期(三周以后),3,5-二甲基吡唑磷酸盐的硝化抑制效果劣于DMPP。3,5-二甲基吡唑磷酸盐能否作为新型硝化抑制荆。还要对它的生理、生态效应等进行进一步的研究。 相似文献
78.
79.
缺氧/好氧膜生物反应器处理尿液污水的研究 总被引:3,自引:0,他引:3
采用缺氧/好氧膜生物反应器(A/O MBR)对尿液污水进行处理.结果表明:当进水NH 4-N、COD和BOD5分别为400~980(容积负荷为0.42~1.01 kg/(m3·d))、390~630和120~280 mg/L时,平均去除率分别为79.5%、75.1%和95.0%,同时系统对色度也有一定的脱除效果,经过A/O MBR和活性炭(PAC)处理后出水色度降为8倍;运行期间膜污染较严重,膜内表面微生物的滋生和膜外表面形成沉积层是造成膜污染的主要原因. 相似文献
80.
Kinetics of ammonium removal with suspended and immobilized nitrifying bacteria in different reactor systems 总被引:4,自引:0,他引:4
The degradation of ammonium by free and immobilized bacteria in different reactor systems was investigated. It was found that the start-up of a nitrifying system is enhanced if a reservoir of immobilized bacteria is present. It was also found that in a single stage system with suspended nitrifying bacteria a stable ammonium removal > 95 % could be established up to an influent ammonium concentration of 1000 mg/1 and a volumetric loading rate (VLR) of 2.3 kg NH4+ m−3 d−1. The oxygen uptake rate (OUR) due to nitrification processes was greatly enhanced with increasing volumetric loading rates. Using nitrifying bacteria immobilized on Siran material it was demonstrated that the ammonium degradation rate was directly proportional to the initial ammonium concentration. 相似文献