Recent Developments in the Biological Filtration of Sewage to Produce High-Quality Nitrified Effluents

The biological filtration of sewage remains the process which is most commonly used for small works in rural areas throughout the UK. In many cases, the need to produce an effluent of high quality with full nitrification is essential in order to comply with the standards set by the Environment Agency. Traditionally, design loading rates of biological filters have been based on historical experience of performance, and on relatively short-term statistical evaluation of the performance of a large number of treatment works, using average and maximum values for flow and loading rates. Many works which were designed on such information have failed to nitrify consistently, particularly during the winter and spring months.
This paper describes the detailed evaluation of six full-scale, biological-filtration sewage-treatment works over a period of two years, in which there were significant changes in sewage flow rate, composition and temperature, from summer to winter. The key parameters which influence the production of high-quality nitrified effluents were determined. The conclusions are used to provide a detailed guide on the design of conventional-media biological filters to produce, consistently, fully-nitrified effluents.     

Coarse-scale soil–atmosphere NOx exchange modeling: status and limitations

Gaseous NO and NO₂ (collectively termed NO_x) are trace atmospheric constituents with important functions in various atmospheric and ecosystem processes. Because nitrification and denitrification in soil are included among major sources of the gases, simulation models for predicting soil-atmosphere NO_x exchange should incorporate the strong dependence of these two microbial processes on soil temperature, soil water content, and substrate N availability. We briefly review current understanding of these controls, then describe how various authors have incorporated that knowledge into model parameterization schemes, and finally present some general thoughts regarding how well those schemes work and what might be missing. Existing coarse-scale models have evolved to the point that they are beginning to explicitly address the influences, interactions, and dynamics of all three microscale controllers in formulations suitable for studies at regional to global and seasonal to interannual scales. Perhaps the greatest limitation of the models, as well as their predictor variables, is that they often fail to account for the large pulse of gaseous N oxide emissions commonly observed following wetting of very dry soil. This failure is exacerbated by mounting evidence that similar pulses may occur following sudden removal of other environmental limitations on microbial growth and metabolism. Such pulses ostensibly make a large contribution to soil- atmosphere NO_x exchange, especially in semi- arid, subhumid, and seasonally dry tropical regions of the globe where the exchange has been poorly characterized despite being subject to intense anthropogenic disturbance.     

Interaction of ammonium and nitrate nutrition with potassium in wheat

A greenhouse experiment with wheat in 3L pots filled with a sandy loam soil in a factorial design was conducted to determine the effect of potassium on nitrogen utilization. Nitrogen was applied in three NH₄-N/NO₃-N ratios, 0/100, 25/75 and 50/50, at three levels: 0.75, 1.50 and 3.00gN/pot, and potassium was applied at three levels: 0, 0.5 and 1.0gK/pot. The higher levels of nitrate nitrogen with or without potassium reduced dry matter yields drastically, while the same levels of a NH₄-N/NO₃-N mixture of 50/50 with applied potassium reduced yields only slightly. Highest grain yield and total yield were obtained with a 25/75 mixture of ammonium/nitrate nitrogen with added potassium. Potassium addition to soil increased the utilization of nitrogen fertilizers, particularly when the ratio of ammonium to nitrate was increased. The highest uptake of reduced nitrogen was at the highest level of the ammonium to nitrate nitrogen ratio (50/50) when potassium was applied. Tillering was enhanced by an increased ammonium ratio in the nitrogen mixture, and by potassium.     

Effects of nitrification inhibitors and time and rate of slurry and fertilizer N application on silage maize yield and losses to the environment

Field experiments with silage maize during eight years on a sandy soil in The Netherlands, showed that dicyandiamide (DCD) addition to autumn-applied cattle slurry retarded nitrification, thus reducing nitrate losses during winter. Spring-applied slurry without DCD, however, was on average associated with even lower losses and higher maize dry matter yields.Economically optimum supplies of mineral N in the upper 0.6 m soil layer in spring (EOSMN), amounted to 130–220 kg ha^–1. Year to year variation of EOSMN could not be attributed to crop demand only. According to balance sheet calculations on control plots, apparent N mineralization between years varied from 0.36 to 0.94 kg ha^–1 d^–1. On average, forty percent of the soil mineral N (SMN) supply in spring, was lost during the growing season. Hence, the amounts of residual soil mineral N (RSMN) were lower than expected. Multiple regression with SMN in spring, N crop uptake and cumulative rainfall as explanatory variables, could account for 79 percent of the variation in RSMN.Postponement of slurry applications to spring and limiting N inputs to economically optimum rates, were insufficient measures to keep the nitrate concentration in groundwater below the EC level for drinking water.     

CANON工艺处理实际晚期垃圾渗滤液的启动实验

针对晚期垃圾渗滤液NH₄^--N浓度高、C/N低、深度脱氮困难的问题,采用CANON工艺在曝气/缺氧搅拌循环交替的运行方式下,处理晚期垃圾渗滤液实现了深度脱氮。系统经过130 d的驯化培养后成功启动,长期试验研究结果表明,在进水COD、NH₄^--N、TN浓度（mg·L^-1）分别为2050±250、1625±75和2005±352情况下,出水COD、NH₄^--N、TN浓度（mg·L^-1）能达到407±14、8±4和19±4,总氮去除率达到了98.76%。在未投加外碳源的情况下,CANON工艺在曝气/缺氧搅拌的运行方式下实现了对晚期垃圾渗滤液的深度脱氮。此外,经荧光原位杂交（FISH）检测表明,在该运行方式下能够成功富集氨氧化菌和厌氧氨氧化菌,各占总菌数的19.5%±1.3%和42.7%±5.02%,为CANON工艺用于处理晚期垃圾渗滤液的工程应用提供参考。     

高氮豆制品废水的亚硝酸型同步硝化反硝化生物脱氮工艺

采用序批式活性污泥法,通过控制溶解氧浓度开发出处理高氮豆制品废水的新工艺.实验结果显示,当曝气阶段反应器内溶解氧浓度保持在0.5 mg•L^-1左右时,曝气过程中NO^-₂-N/NO^-_x-N的比率始终维持在93%以上,并且曝气结束时,有大约87.6%的氨氮是通过同步硝化反硝化途径去除的.因此,控制反应器内溶解氧浓度在0.5 mg•L^-1左右时,在一个反应器内同时实现了亚硝酸型硝化反硝化和同步硝化反硝化.经过理论计算和机理分析,在此溶解氧下,亚硝酸菌的比增殖速率近似为硝酸菌的2.22～2.43倍,并且低溶解氧容易在活性污泥颗粒内形成进行反硝化作用的缺氧区.因此,在常温下,只要采用溶解氧传感器控制SBR反应器内溶解氧浓度在0.5 mg•L^-1左右,就可以实现稳定的亚硝酸型同步硝化反硝化生物脱氮工艺.     

风化煤和硼在土壤中对尿素氨化与硝化作用及磷有效性的影响

在实验室培养条件下,研究风化煤和硼在土壤中对尿素氨化与硝化作用及磷有效性的影响。结果表明,风化煤和硼对尿素氨化作用有显著的抑制作用,风化煤对脲酶抑制率为5.7%～14%,硝化抑制率为1.4%～8.5%;硼的脲酶抑制率为5.5%～18.3%,硝化抑制率为1.4%～12.7%;风化煤与硼配合的抑制效果更明显,脲酶抑制率为18.3%～43.6%,硝化抑制率为0.6%～10.6%。在专用肥中添加风化煤能使土壤中磷的有效性提高8.2%～23.6%。     

硝酸改性活性炭纤维负载TiO2及其催化降解甲苯性能

将TiO2负载于经硝酸改性的活性炭纤维(ACF)上得到TiO2/ACF复合催化剂,采用扫描电镜(SEM)、X射线光电子能谱(XPS)、紫外激光拉曼光谱(Raman)和X射线衍射(XRD)等手段研究其形貌,并考察环境湿度、ACF硝化强度和TiO2负载量对甲苯光催化氧化降解的影响。结果表明:经硝酸改性的ACF表面富含含氧基团,能使TiO2在其表面均匀分布,从而使甲苯转化率提高近3.5倍;随环境湿度上升,甲苯转化率先上升后下降,主要是因为湿度上升,吸水量上升,导致甲苯吸附量下降;ACF硝化强度增大,导致催化剂吸水能力增强,从而提高甲苯转化率;TiO2负载量上升导致ACF表面TiO2颗粒形貌改变,使甲苯转化率先上升后下降。     

生物流化床反应器脱氮技术的研究与应用进展

生物流化床技术是废水处理中常采用的生物技术之一。作者介绍了生物流化床脱氮技术的最新研究进展与应用,详细分析了影响生物流化床脱氮效率的主要因素,指出了生物流化床脱氮技术存在的一些急需解决的问题,提出了生物流化床技术今后的发展方向。     

在SBBR中接种硝化菌时SND特性及机理

通过加硝化菌与未加硝化菌的对比试验,对序批式生物膜法(SBBR)中户斤表现出来的脱氮特性进行了试验分析,研究探讨生物膜法SND脱氮的机理：好氧情况下生物膜的吸附作用为反硝化菌提供碳源和能源;SND反应主要发生在好氧生物膜层和兼性生物膜分界内;在深层的反硝化菌利用生物膜中储存的有机物作为有机碳源,将好氧生物膜中产生的N03^ 3-N转化为N2。同时加入一定量的硝化菌能较好地提高硝化,脱氮率。