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101.
Nitrification of simulated secondary effluent solution using a variant of the vertical flow bed constructed wetland was studied. In this system oxygen required for the nitrification process is supplied by a passive air pump. The passive air pump is based on a fill and draw cycle, where oxygen depleted air is removed from the system while fresh air is introduced. Each volume of effluent drained is displaced by an equal volume of fresh air. Spatial and temporal oxygen distribution in the system as a function of drained effluent volume was investigated. Experimental results of nitrification and the corresponding oxygen consumption show good agreement with theoretical calculations based on physico–chemical considerations. Observations show that while oxygen distribution within the media was found to be non-uniform at the beginning of each cycle, it approached more uniform distribution with time. The latter resulted mainly from diffusion of oxygen in the gaseous phase. 相似文献
102.
This work represents one stage in the optimization of biological nitrification by attached culture.The utilization of columns packed with fine granular media, such as Biolite, and sterile conditions has enabled the overall nitrite oxidation rates of the pure strain Nitrobacter winogradskyi serotype agilis in attached culture to be measured.The utilization of methods for counting attached bacteria, combined with measurements of the oxygen consumption, has enabled the specific respiratory activity of Nitrobacter in attached culture to be determined and a comparison to be made with the values observed with free cultures.The results obtained show a great increase in the nitrite oxidation rate and a 130% increase in the respiratory activities specific to attached bacteria in comparison with free cells. 相似文献
103.
Transformation of calcium cyanamide and its inhibitory effect on urea nitrification in some tropical soils 总被引:1,自引:0,他引:1
Transformation of calcium cyanamide and its inhibitory effect on urea nitrification was studied in some tropical soils. Three soils, from Onne, Mokwa and Samaru, representing different agro-climatological zones of Nigeria were incubated with calcium cyanamide, urea or a mixture of both for eight weeks at 30 °C and at field capacity moisture content. The recovery of inorganic N (NH
4
+
plus NO
2
-
plus NO
3
-
)from calcium cyanamide varied from 64% to 87% in different soils. Most of the inorganic N accumulated was in NH
4
+
form. Nitrification of the accumulated NH
4
+
in all the soils was slow.Urea (75 mg N kg–1 soil) was completely nitrified within a week in the Samaru and Mokwa soils whereas in the Onne soil the rate of nitrification was slow. Addition of CaCN2 at the rate of 10 mg N kg–1 soil generally delayed ammonification of urea and nitrification was severely inhibited in all the soils. Addition of CaCN2 at the rate of 20 mg N kg–1 soil further reduced the ammonification of urea and completely inhibited the nitrification. High recovery of inorganic N from calcium cyanamide and its effective reduction of nitrification of urea make it suitable source of N for plants in the tropics, provided it is managed to avoid phyto-toxicity. 相似文献
104.
The transformations of urea, ammonium sulfate and dicyandiamide (DCD) were studied in an Inceptisol and three Andisols from Costa Rica, considering the influence of temperature and DCD as a nitrification inhibitor.Nitrification was very slow with or without DCD in the strongly acid Inceptisol. A higher urea dose resulting in higher pH was well nitrified without DCD and appreciably retarded by DCD.In Andisols nitrification was retarded as long as a higher DCD level existed. Higher temperatures accelerated the DCD-breakdown and were followed by a quicker nitrification. The decomposition of DCD was slower compared with the Inceptisol. According to these experiments DCD is suitable as a nitrification inhibitor in tropical soils. 相似文献
105.
106.
JPNL Roorda Van Eysinga 《Nutrient Cycling in Agroecosystems》1984,5(2):149-156
Leafy vegetables grown under glass in winter have a rather high nitrate content. Three possibilities of reducing this content are discussed: the use of nitrification inhibitors, growing on NFT and omission of nitrogen during a certain period before harvest, and the breeding of varieties with a low nitrate content.In the last chapter the question whether high nitrate levels in vegetables are dangerous to human health is briefly discussed. 相似文献
107.
R.?G.?SilvaEmail author E.?E.?Jorgensen S.?M.?Holub M.?E.?Gonsoulin 《Nutrient Cycling in Agroecosystems》2005,71(3):259-270
The size and quality of the soil organic matter (SOM) pool can vary between ecosystems and can affect many soil properties. The objectives of this study were to examine the relationship between gross N transformation rates and microbial populations and to investigate the role that SOM plays in these factors. In our study, culturable microbial and actinomycete populations were positively correlated with gross mineralization and ammonium (NH4+) consumption rates over time in both ecosystems. These correlations provide evidence that microbial plate counts could be a good representation of all microbes responsible for gross mineralization and gross NH4+ consumption. Rates of gross mineralization, nitrification and NH4+ consumption were significantly greater in forest soil than old-field soil. These greater rates in forest soil could be due to the presence of higher levels of readily transferable substrates in SOM. Gross nitrification rates were considerably lower than gross mineralization and NH4+ consumption rates over the experimental period, indicating heterotrophic uptake of NH4+ rather than use by autotrophic nitrifiers under soil and environmental conditions in this study. Additionally, microbial populations were significantly (p<0.01) greater in forest soil than in old-field soil, which could also be related to the higher level of SOM in the forest soil. Net mineralization and nitrification rates were similar between ecosystems. Results also showed that net rates were highly correlated to each other, but were not correlated with culturable microbes or gross N transformation rates, indicating the isolation of net rates in relation to fundamental controlling factors. 相似文献
108.
高溶解氧环境下好氧亚硝化颗粒污泥短程硝化特性研究 总被引:2,自引:0,他引:2
研究好氧亚硝化颗粒污泥的快速形成及在高溶解氧环境下好氧亚硝化颗粒污泥的短程硝化特性。采用SBR反应器,在偏碱性、高溶解氧条件下,以好氧颗粒污泥和具有硝化功能的活性污泥为种泥驯化培养,分析好氧亚硝化颗粒污泥形成机理及对亚硝酸盐的积累能力。研究结果表明:12d可形成具有氨氮平均去除率97%、最高亚硝化率70%的好氧亚硝化颗粒污泥,反应器能持续稳定运行;溶解氧高低对好氧亚硝化颗粒污泥的亚硝化率影响不大。说明此方法能够快速形成具有高亚硝酸盐积累率的好氧亚硝化颗粒污泥。 相似文献
109.
110.
明光市污水处理厂工艺设计采用国内先进的Orbal氧化沟工艺,着重去除污水中的有机物同时兼具生物脱氮除磷功能,工艺流程符合该市的污水特征。但由于受明光市目前的雨、污水管道未完全分流而造成讯、旱两季水质水量变化较大的影响,如何通过适当调整措施,实现污水厂的安全运行,是文章需要探讨的主要问题。 相似文献