趋磁微生物处理污水研究

指出了趋磁性微生物能够在缺氧和厌氧条件下,以硝酸盐作为最终电子受体,产生反硝化反应,进行脱氮处理。趋磁微生物可以利用硫酸盐、硫代硫酸盐为电子受体,进行硫化反应,去除污水中的硫。趋磁微生物在磁场的作用下,可以定向移动。增加污泥的沉淀速度,减少沉淀池的容积及沉淀时间。趋磁微生物处理重金属污水,能够很好地解分选,回收有用的重金属。对趋磁微生物处理污水进行了研究。     

好氧反硝化复合菌剂的研制及其在海水养殖废水处理中的应用

从天津某海水养殖场底泥中分离筛选好氧反硝化菌,获得3株具有高效反硝化特性的微生物,分别为MCW148、MCW151和MCW154。采用正交试验对功能菌进行优化组合,研制好氧反硝化复合菌剂。结果表明,MCW148、MCW151、MCW154的最优配比为3∶2∶1,其在12 h内对海水养殖废水中无机氮的去除率为60.39%。     

SBR生物脱氮机理及其影响因素

开发高效经济的生物脱氮技术一直是国内外科研工作者所关注的热点。本文介绍了SBR系统的微生物相、硝化－反硝化、亚硝化－反亚硝化生物脱氮技术及其影响因素的研究进展，并指出了当前SBR法在脱氮方面存在的问题以及发展趋势。     

Nitrate stability in loess soils under anaerobic conditions—laboratory studies

The objective of this laboratory study with six loess soils (three Eutric CambisoIs and three Haplic Phaeozems) incubated under flooded conditions was to examine the effect of a wide range of NO doses under anaerobic conditions on soil redox potential and N₂O emission or absorption. Due to the fact that loess soils are usually well‐drained and are expected to be absorbers during prevailing part of the season, the study aimed at determination of the conditions decisive for the transition from emission to absorption process. On the basis of the response to soil nitrate level, the two groups of soils were distinguished with high and low denitrification capacity. The soil denitrification activity showed Michaelis‐Menten kinetics with respect to soil nitrate content with K_M in the range 50–100 mg NO ‐N kg^–1. Percentage of nitrates converted to N₂O increased linearly with nitrate concentration in the range from 25 to 100 mg NO ‐N kg^–1 up to 43% and decreased linearly at higher concentrations reaching practically zero at concentrations about 600 mg NO ‐N kg^–1. No denitrification was observed below 25 mg NO ‐N kg^–1. Nitrous oxide absorption in soil occurred only at nitrate concentrations to 100 mg NO ‐N kg^–1 and in this concentration range was proportional to the denitrification rate. Nitrous oxide was formed at redox potentials below +200 mV and started to disappear at negative E_h values.     

Nitrification activity in tropical rain forest soils of the Coastal Lowlands and Atherton Tablelands,Queensland, Australia

Intact soil cores from a montane tropical rain forest site in the Atherton Tablelands (Kauri Creek) and from a lowland tropical rain forest site in the Coastal Lowlands (Bellenden Ker), Queensland, Australia were investigated during different hygric seasons for the magnitude of gross nitrification rates using the Barometric Process Separation technique (BaPS). Pronounced seasonal variations of gross nitrification rates were found at both sites with highest values during the transition period between dry and wet season (montane site: 24.0 mg N (kg SDW)^—1 d^—1; lowland site: 13.1 mg N (kg SDW)^—1 d^—1) and significantly lower rates of gross nitrification during the dry and wet season. Rates of gross nitrification were always higher at the montane site than at the lowland site, but the opposite was found for N₂O emissions. The results indicated that the high losses of N₂O at the lowland tropical rain forest site may be contributed largely by high denitrification activity due to its wetter and warmer climate as compared to the dryer and colder climate at the montane tropical rain forest site. This conclusion was supported by analysis of cell numbers of microbes involved in N‐cycling. Higher numbers of denitrifiers were present at the lowland site, whereas higher numbers of nitrifiers were found at the montane site.     

Nitrous oxide flux from soil amino acid mineralization

Nitrous oxide (N₂O) is a greenhouse gas produced during microbial transformation of soil N that has been implicated in global climate warming. Nitrous oxide efflux from N fertilized soils has been modeled using NO₃⁻ content with a limited success, but predicting N₂O production in non-fertilized soils has proven to be much more complex. The present study investigates the contribution of soil amino acid (AA) mineralization to N₂O flux from semi-arid soils. In laboratory incubations (−34 kPa moisture potential), soil mineralization of eleven AAs (100 μg AA-N g⁻¹ soil) promoted a wide range in the production of N₂O (156.0±79.3 ng N₂O-N g⁻¹ soil) during 12 d incubations. Comparison of the δ¹³C content (‰) of the individual AAs and the δ¹³C signature of the respired AA-CO₂-C determined that, with the exception of TYR, all of the AAs were completely mineralized during incubations, allowing for the calculation of a N₂O-N conversion rate from each AA. Next, soils from three different semi-arid vegetation ecosystems with a wide range in total N content were incubated and monitored for CO₂ and N₂O efflux. A model utilizing CO₂ respired from the three soils as a measure of organic matter C mineralization, a preincubation soil AA composition of each soil, and the N₂O-N conversion rate from the AA incubations effectively predicted the range of N₂O production by all three soils. Nitrous oxide flux did not correspond to factors shown to influence anaerobic denitrification, including soil NO₃⁻ contents, soil moisture, oxygen consumption, and CO₂ respiration, suggesting that nitrification and aerobic nitrifier denitrification could be contributing to N₂O production in these soils. Results indicate that quantification of AA mineralization may be useful for predicting N₂O production in soils.     

土壤反硝化酶活性测定方法及影响因素研究

借助土壤酶学的基本原理,初步建立了一种底物(KNO3)最佳浓度为10 g/L,土样不需二次离心的土壤反硝化酶活性测定方法——硝态氮剩余量法,并对其影响因素进行了研究。结果表明,该测定方法简便、快速、灵敏;有机肥的加入可显著提高土壤反硝化酶的活性,有机肥和化肥的共施是最佳的培肥措施;种植作物也可提高土壤反硝化酶活性;甲苯对土壤反硝化酶活性有明显的抑制作用,且土壤肥力水平越高,抑制幅度越大。     

厌氧同时反硝化产甲烷工艺研究进展

近年来,厌氧废水处理工艺的功能在原有单纯去除有机物的基础上,得到了进一步的扩展。本文介绍了厌氧同时反硝化/产甲烷工艺的原理、技术开发与应用实践,并对其应用前景进行了展望。根据我国现阶段国情,高效低耗、操作简单、易于管理的厌氧同时反硝化/产甲烷工艺是今后高含氮有机废水处理的发展方向。     

人工湿地脱氮性能优化分析及研究建议

简要论述了人工湿地生态系统氮转化的几种主要影响因素.进行了人工湿地植物的选择、不同的进水方式对提高大气复氧的研究和增加湿地系统碱度的措施等方面的讨论.从碱度方面分析,提出了分步硝化、反硝化的设计构想,并做了简单的论述,同时在增加反硝化碳源的问题上设想了两种新的方案.最后,针对我国小城镇以及广大农村地区的排水特点和我国的地形特征提出了在具有一定坡度的地形上建立小型"分散式"人工湿地的建议.     

Separating N2O production and consumption in intact agricultural soil cores at different moisture contents and depths

Agricultural soils are a major source of the potent greenhouse gas and ozone depleting substance, N₂O. To implement management practices that minimize microbial N₂O production and maximize its consumption (i.e., complete denitrification), we must understand the interplay between simultaneously occurring biological and physical processes, especially how this changes with soil depth. Meaningfully disentangling of these processes is challenging and typical N₂O flux measurement techniques provide little insight into subsurface mechanisms. In addition, denitrification studies are often conducted on sieved soil in altered O₂ environments which relate poorly to in situ field conditions. Here, we developed a novel incubation system with headspaces both above and below the soil cores and field-relevant O₂ concentrations to better represent in situ conditions. We incubated intact sandy clay loam textured agricultural topsoil (0–10 cm) and subsoil (50–60 cm) cores for 3–4 days at 50% and 70% water-filled pore space, respectively. ¹⁵N-N₂O pool dilution and an SF₆ tracer were injected below the cores to determine the relative diffusivity and the net N₂O emission and gross N₂O emission and consumption fluxes. The relationship between calculated fluxes from the below and above soil core headspaces confirmed that the system performed well. Relative diffusivity did not vary with depth, likely due to the preservation of preferential flow pathways in the intact cores. Gross N₂O emission and uptake also did not differ with depth but were higher in the drier cores, contrary to expectation. We speculate this was due to aerobic denitrification being the primary N₂O consuming process and simultaneously occurring denitrification and nitrification both producing N₂O in the drier cores. We provide further evidence of substantial N₂O consumption in drier soil but without net negative N₂O emissions. The results from this study are important for the future application of the ¹⁵N-N₂O pool dilution method and N budgeting and modelling, as required for improving management to minimize N₂O losses.