Advances in the Study of Nitrogen and Phosphorus Removal Mechanisms in Constructed Wetlands

Constructed wetlands are wastewater treatment ecosystems composed of substrata, plants, microorganisms and water. We summarize herein recent research findings about nitrogen and phosphorus removal mechanisms in wastewater treated by constructed wetlands and the influencing factors, such as substrata, plants, microorganisms, hydraulic loads, temperature and dissolved oxygen. To increase the nitrogen and phosphorus removal efficiency and extend the fields of constructed wetland application, nitrogen and phosphorus removal mechanisms, influencing factors and techniques must be studied intensively in the future.     

Research on the Strengthening Effect of the Nitrogen and Phosphorus Removal by the Multi-loop Reactor in Low Carbon-resource Condition

A multi-loop reactor is constructed based on analysis of temporal and spatial character of several continuous current nitrogen and phosphorus removal process in this paper.Through cross experiment design,the important factors to influence the effect of the nitrogen and phosphorus removing under low carbon-resource condition were found,and the feasible control parameters of the biological nitrogen and phosphorus removal process under low carbon-resource condition were put forward.The results are valuable for design and operation of wastewater treatment process with similar conditions.     

Comparison of Dissolved Oxygen Distribution and Nitrogen Removal Effect in Wetlands with Different Structures

The dissolved oxygen distribution and nitrogen removal effect in different structures of wetlands were investigated by two groups of comparison experiments (vertical flow with horizontal flow; single stage with three stage horizontal flow). It was found that the different hydraulic flow patterns in different structures of wetlands would result in different oxygen distribution and nitrogen removal effect. The special structure design and hydraulic flow pattern of vertical flow wetland were favorable to its dissolved oxygen distribution, which could increase 0.17 mg/L in local area than that in horizontal flow wetland. The nitrogen removal effect of vertical flow wetland was better than that of horizontal flow wetland in the same operation conditions. The removal efficiency of NH+4-N and TN could increase 9% and 5% respectively in vertical flow wetland than that in horizontal flow wetland. Because of reaeration in contacting channels of three stage wetland, the removal efficiency of NH+4-N and TN reached 66% and 71% respectively, which improved 8% and 5% respectively than that of single stage wetland. In addition, three stage wetland could keep higher nitrogen removal effect even in low operation water level, and the range of its best hydraulic retention time(HRT) was extended.     

Review on Nitrogen and Phosphorus Removal by the Bio-filter

In this paper, the new development of nitrogen and phosphorus removal by bio-filter in home and abroad is summarized.The factors influencing the nitrification-de-nitrification, nitration-denitration, phosphorous removal and simultaneous nitrogen and phosphorus removal in bio-filter reactor are reviewed.It is pointed out that further improving the operation, enhancing the effect of nitrogen and phosphorus removal and advancing the process of bio-filter is the aim of study in the future.     

Approach to the Enhancement of Removal of Phosphorus and Nitrogen in Oxidation Ditch

In response to the characteristic of oxidation ditch and its limitation in removal of phosphorus and nitrogen,the research of the biological phosphorus and nitrogen removal in micro-environment and macroenvironment was reviewed.The process of enhancing phosphorus and nitrogen removal was discussed,the way to improve the phosphorus and nitrogen removal was presented:(1)the proper sequential arrangement of the locations of aerator,influent,effluent and return sludge to form the reversed A~2/O process;(2)forming more rigorously anaerobic zone by means of vertical flow circle;(3)the proper supply of oxygen,to avoid insufficiency of aerobic phosphorus uptake and nitrification with low oxygen supply;While to keep from overmuch waste of carbon source going against de-nitrification,and high oxygen concentration going against anaerobic phosphorus release due to high oxygen supply;(4)the proper hydraulic parameter and oxygen supply mode.     

Domestic Sewage Treatment Using Three-stage SBR Denitrification and Phosphorus Removal Process

Based on the mechanism of biological phosphorus and nitrogen removal, the collision between on nutrient and resident time is given. In order to solve this problem, a new process for wastewater biological treatment- three-stage SBR process has been developed. Three- stage SBR process treat domestic sewage is applied, which controls various kinds of bacteria optimum growth with the different function that responsibility for removal organics, nitrogen and phosphorus existed in the different reactors and combine with the denitr/fying phosphorus removing process . The experiment results show that ,the three-stage SBR process not only improved the treatment efficiency that COD ,TN,and TPaverage removal efficiency is 87% ,80% and 86% , but also saved the energy cost. removal. The process can make better effect on simultaneous nutrients removal, simple operation and low cost will make a good application prospect for it.     

Analysis of Phosphorus Removal in the Non-backflow Intermittent Aeration System

In this paper the phosphorus removal performance has been studied in Non-backflow Intermittent Aeration System (NBIAS), when the aeration duration and SRT were adjusted. At the same time, nitrogen removal was also studied. Test results show that when the cycle duration is 6 h., anaerobic duration 1.5h. sedimentation and displacement time 0.5 h. and SRT=20 d,aerobic ratio 0.42, the removal efficiency for CODcr, nitrogen and phosphorus will be 85%, 75% and 69%, respectively.     

秸秆还田对土壤氮磷及水土的影响研究

秸秆还田作为低碳农业、有机农业的重要环节,对改善土壤结构,减少水土流失,提高土壤的养分含量具有积极作用。秸秆还田主要通过增加土壤孔隙度,降低土壤容重从而调节地温,达到蓄水保墒的功能,促进作物生长。秸秆还田能有效增加土壤有机质含量,提高氮肥的利用效率,有效减少氮素、磷素的流失,提高土壤氮素的含量,对土壤中有效磷和全磷含量均有所提高,改善农田生产环境,保障粮食增产能力。秸秆还田能有效减少地表径流量和径流次数,从而减少径流所带走的养分,减缓对周围水系的面源污染,有利于提高土壤含水量。有效的秸秆还田对N2O等温室气体的排放的实验研究,有着不同的研究结果。但是秸秆还田的实施还存在着一定的问题,应进一步深入研究秸秆还田对土壤养分和环境的影响机制,进行长期监测实验,发展恰当的秸秆还田方式,减少化肥的使用,对促进我国农业的持续快速发展有着十分重要的意义。     

河流氮、磷滞留研究方法综述

为了研究河流输送过程中氮、磷的主要滞留途径及滞留效率,笔者综述了国内外近些年关于河流氮、磷滞留的研究方法。结果表明,目前常用的研究方法主要有物质平衡法、经验模型法和同位素示踪法。虽然,这些方法均得到了广泛使用,但仍存在模型参数不具普遍适用性以及估算误差较大、多同位素示踪技术研究缺乏等方面的不足。因此,综合考虑多种影响因素,建立具有普遍适用价值的估算模型,以及如何减少同位素示踪研究中生物地球化学过程对同位素δ值的改造,应成为今后的重点研究领域。     

不同水生植物－微生物系统去除水体氮磷能力研究

目前,中国湖泊水体的富营养化环境现状令人堪忧。如何有效利用更多具有经济价值的水生植物—微生物系统去除氮、磷（特别是氮）具有非常重要的意义。通过对不同总氮（总磷一定）浓度下香根草、水葫芦、水芹等水生植物—微生物系统培养水质、根际细菌总数及植物体氮、磷含量进行监测,来分析其水质动态变化规律,以及水质参数、根际细菌总数及水生植物之间的相关关系;揭示水生植物—微生物系统中水生植物的吸收作用和根际微生物系统对净化水质的作用。试验分析得出：3种水生植物去除营养盐氮、磷的能力各有不同,在所设置的3个总氮（TN）浓度下,各有一种植物能够达到最好的处理效果,且能较好地促进根际细菌的生长。比较而言,水芹系统对高浓度氮的吸收能力强,水葫芦系统对高浓度磷的吸收能力强。     

施氮量对抚仙湖流域烟田氮磷流失及氮素利用的影响

为探究抚仙湖流域植烟区烤烟适宜施氮量,减少烟田径流氮磷流失,通过田间试验研究了不同施氮(N)水平(N0：0 kg/hm²、N60：60 kg/hm²、N75：75 kg/hm²、N90：90 kg/hm²、N105：105 kg/hm²)对植烟区农田地表径流氮磷流失、烤烟(Nicotiana tabacum)氮素吸收利用和经济性状的影响。结果表明：（1）随着氮肥施用量增加,地表径流总氮(TN)和总磷(TP)浓度及其流失量逐渐升高;（2）与常规施氮处理(N105)相比,N60、N75、N90处理径流TN和TP平均浓度分别降低18.6%、14.7%、9.15%和12.3%、7.66%、5.25%,TN和TP流失总量分别降低19.2%、18.1%、9.81%和14.4%、10.1%、6.78%;（3）烟株氮累积量随施氮量的增加而增加,氮肥利用率呈先上升后下降趋势,以处理N75的氮肥利用率最高,为27.00%;氮肥偏生产力随着施氮水平的提高而显著下降(P<0.05);（4）烤烟产量随施氮量提高而增加,施氮处理较N0处理增产3.02%~13.90%,上等烟、上中等烟比例、产值和均价,随施氮量增加呈先上升后下降趋势,以施氮量75 kg/hm²的效果最佳。综合考虑烤烟经济性状及环境效益,N75处理既可提高烤烟经济性状,又能有效降低植烟区氮磷流失风险。     

茄子氮磷钾养分效应研究

为了提高土壤养分供应量及强度、平衡茄子生产养分供求矛盾,探讨适宜茄子高产种植的氮磷钾最佳养分配方。以“农夫3号”为材料,采用“3414”设计方案,试验共设14个处理,3次重复,开展田间试验。结果表明：不施肥情况下茄子产量显著低于施肥处理,在不同施肥措施中N2P2K2处理的产量最高,不施或者少施氮、磷、钾中的任何一种养分均不同程度导致减产,其中氮肥的产量贡献率最大;氮、磷、钾养分供应不足均减少茄子有效结果数;茄子产量随着氮、磷、钾施用水平呈现一定趋势变化,氮素肥料是茄子产量形成最主要限制因子;增施氮、磷、钾养分肥料显著提高了植株养分含量及累积量,但降低了果实养分分配比例。通过茄子产量与养分用量模型分析,得到茄子推荐比例N:P2O5:K2O=1:0.55~0.83:0.63~0.84,施肥量为N:P2O5:K2O=392~433:240~243:271~330 kg/hm2。     

不同施肥模式对菜稻轮作产量和菜田氮磷平衡的影响

通过马铃薯-毛豆-晚稻轮作制2 年定位田间试验,研究不同施肥模式对菜稻轮作产量和菜田氮磷浓度的影响。结果表明：经济施肥使三季作物获得显著增产效果,一个轮作周期下净增收比CK处理增加23.7%,比习惯施肥处理增加10.5%。一个轮作制中,氮磷肥表观利用率分别达到60.5%和16.0%,比习惯施肥提高了15.6 个百分点和7.3 个百分点。马铃薯-毛豆连作在经济施肥下,土柱渗漏水硝态氮和总磷浓度分别比基础土壤提高了63.3%和30.6%,但与晚稻轮作后,土柱渗漏水硝态氮和总磷浓度与基础土壤大致持平。因此,菜稻轮作结合经济施肥是菜田养分管理的有效技术模式。