Dynamics of Nitrogen Transformation and Removal in a Pilot High Rate Pond

The transformation and removal of nitrogen was studied in a pilot high rate pond with a surface area of 10.2 m2 and water depth of 60 cm. The pilot unit received wastewater from an existing field scale primary facultative pond at the University of Dar es Salaam. Wastewater samples were collected from the influent and effluent of high rate pond and were analyzed for physical-chemical parameters in the laboratory and in situ. An appropriate model complexity was selected, from which a conceptual model was then developed to model various processes in the system using STELLA 6.0.1 software. The study demonstrated that dominant nitrogen transformation processes in HRP were nitrification and denitrification, which transformed 0.95 and 0.87 gN/m2·d, respectively. These were followed by mineralization (0.37 gN/m2·d), ammonia uptake by microorganisms (0.34 gN/m2·d), volatilization (0.30 gN/m2·d), sedimentation (0.24 gN/m2·d), and regeneration (0.15 gN/m2·d). Uptake of nitrate was not observed because of microorganisms preference for ammonia, which was abundant in the pond. The major nitrogen transformation mechanisms in high rate pond were denitrification, net sedimentation and volatilization, which accounted for 69.1%, 7.1% and 23.8% of the total permanent removal mechanisms of nitrogen in High Rate Pond.

Removal of Nitrogen Dioxide and Sulfur Dioxide from Air Streams by Absorption in Urea Solution

The study focuses on the absorption rates of NO2, SO2 and a mixture of these two acid gases into urea solution in packed bed column. The absorption rate was studied as a function of absorbent temperature, urea concentration and acid gas concentration. The influence of liquid temperature between 10 - 40?C, urea concentration between 0.1 - 0.5 M and acid gas concentration NO2 between 100 - 1000 ppm (191 - 1910 mg/m3), SO2 between 500 - 2500 ppm (1310 - 6530 mg/m3) were investigated. The mass gas flow rate of 20.646 (kg/m2.min) at 25?C and the absorption rate were determined by measuring the NO2 and SO2 concentrations in the inlet and outlet streams of the absorptioncolumn. The absorption rate of SO2 increases with the decrease of temperature of absorbent (urea solution) and with the increase of the urea concentration. The presence of NO2 in the effluent gas stream lowers the absorption rate of SO2 in urea solution due to the fast reaction of NO2 with urea as compared with SO2. The absorption rate of NO2 decreases as the urea concentration exceeds 0.4 mol/l and for NO2 gas concentration of 100 ppm due to the decrease the diffusivity of the gas. The experimental data were analyzed using dimensionless analysis to find the correlation of mass transfer coefficient in the packed column Sh (H / dp)1.2 = 4.19*10–2 *(G' dp / μg)0.87 (μg / ρg DAB)0.60 The results confirmed the hypothesis that the absorption is accompanied with chemical reaction. Also it is found the increasing the temperature of absorbent solution the absorption rate of two gases is decreases. The mass transfer coefficient models are in good agreements with the Kramer’s equation.

Nitrogen removal efficiency of iron-carbon micro-electrolysis system treating high nitrate nitrogen organic pharmaceutical wastewater

The nitrate nitrogen removal efficiency of iron-carbon micro-electrolysis system was discussed in treating pharmaceutical wastewater with high nitrogen and refractory organic concentration. The results show that the granularity of fillings,pH,volume ratios of iron-carbon and gas-water,and HRT. have significant effects on the nitrogen removal efficiency of iron-carbon micro-electrolysis system. The iron-carbon micro-electrolysis system has a good removal efficiency of pharmaceutical wastewater with high nitrogen and refractory organic concentration when the influent TN,NH4+-N,NO3--N and BOD5/CODCr are 823 mg/L,30 mg/L,793 mg/L and 0.1,respectively,at the granularity of iron and carbon 0.425 mm,pH 3,iron-carbon ratio 3,gas-water ratio 5,HRT 1.5 h,and the removal rates of TN,NH4+-N and NO3--N achieve 51.5%,70% and 50.94%,respectively.

Simultaneous nitrification and autotrophic denitrification in fluidized bed reactors using pyrite and elemental sulfur as electron donors

In this study, simultaneous nitrification and autotrophic denitrification (SNAD) with either elemental sulfur or pyrite were investigated in fluidized bed reactors in mesophilic conditions. The reactor performance was evaluated at different ammonium (12-40 mg/L of NH4+-N), nitrate (35-45 mg/L of NO3--N), and dissolved oxygen (DO) (0.1-1.5 mg/L) concentrations, with a hydraulic retention time of 12 h. The pyrite reactor supported the SNAD process with a maximum nitrogen removal efficiency of 139.5 mg/(L·d) when the DO concentration was in the range of 0.8-1.5 mg/L. This range, however, limited the denitrification efficiency of the reactor, which decreased from 90.0% ± 5.3% in phases II-V to 67.9% ± 7.2% in phases VI and VII. Sulfate precipitated as iron sulfate (FeSO4/Fe2(SO4)3) and sodium sulfate (Na2SO4) minerals during the experiment. The sulfur reactor did not respond well to nitrification with a low and unstable ammonium removal efficiency, while denitrification occurred with a nitrate removal efficiency of 97.8%. In the pyrite system, the nitrifying bacterium Nitrosomonas sp. was present, and its relative abundance increased from 0.1% to 1.1%, while the autotrophic denitrifying genera Terrimonas, Ferruginibacter, and Denitratimonas dominated the community. Thiobacillus, Sulfurovum, and Trichlorobacter were the most abundant genera in the sulfur reactor during the entire experiment.

Personal Review:Sources of sulfide in waste streams and current biotechnologies for its removal

Sulfide-containing waste streams are generated by a number of industries. It is emitted into the environment as dis- solved sulfide (S2- and HS-) in wastewaters and as H2S in waste gases. Due to its corrosive nature, biological hydrogen sulfide removal processes are being investigated to overcome the chemical and disposal costs associated with existing chemically based removal processes. The nitrogen and sulfur metabolism interacts at various levels of the wastewater treatment process. Hence, the sulfur cycle offers possibilities to integrate nitrogen removal in the treatment process, which needs to be further optimized by appropriate design of the reactor configuration, optimization of performance parameters, retention of biomass and optimization of biomass growth. The present paper reviews the biotechnological advances to remove sulfides from various environments.

Study on the Removal of Ammonia Nitrogen from Wastewater Using Microwave Coupled with Active Carbon

[ Objective] The study aimed to discuss the feasibility and optimal conditions of removing ammonia nitrogen by using microwave coupled with active carbon. [ Method ] In the study, a novel process, microwave radiation coupled with active carbon, was applied to remove ammonia nitro- gen from wastewater, and the influences of solution pH, air conditions, active carbon usage, microwave power and time on the removal effect of ammonia nitrogen were studied. [ Result] Microwave coupled with active carbon can remove ammonia nitrogen efficiently, and pumping air into the wastewater can also increase the removal rate of ammonia nitrogen to a certain extent. Higher pH, intensive microwave power and longer treating time could also increase the removal rate of ammonia nitrogen using microwave radiation coupled with active carbon, whereas the usage of active carbon contributed a small impact. It was proved that microwave coupled with active carbon was an effective method for the removal of ammonia ni- trogen from wastewater. Meanwhile, the orthogonal experiment results showed that the removal rate of ammonia nitrogen reached 92.5% under the optimal conditions, that is, the usage of active carbon was 0.5 g, pH = 11, microwave radiation power was 850 W, and microwave action time was 4 minutes. [ Conclusion] The research provided a new method to remove ammonia nitrogen from wastewater, namely microwave coupled with ac- tive carbon.

Development and Study on Nitrogen Removal Controller in A/O Process

In this paper three controllers for A/O process are developed, including a DO cascade controller, an external carbon flow rate controller and an internal recycling flow rate controller. The objective of the different controllers is to control the nitrate and ammonia concentration. Simulation study demonstrated that these controllers could efficiently control nitrogen removal and meet stricter effluent quality standards at a minimum cost.

Simulation Study on Purification Efficiency for Nitrogen in Different Types of Wetlands in Sanjiang Plain, China

The purification law of nitrogen in Deyeuxia angustifolia, Carex lasiocarpa and Deyeuxia angustifolia-Carex lasiocarpa combined wetland systems in the Sanjiang Plain, China was studied by field simulation experiment. The results indicate that the removal rates of TN, NH4^＋-N and NO3^--N in above three types of wetlands present an obvious logarithm growth trend along with the time. There are evident removal effects for NH4＋-N and NOa--N in water bodies of wetlands after the 30th day of experiment, with the removal rates over 80.0%, but the removal rate of TN is slightly low, being 63.1%-74.3%. NO3 -N is most quickly removed by the combined wetland, and NH4^＋-N by Deyeuxia angustifolia wetland. The removal speeds of TN by the three wetland systems are comparatively slow, of which the Deyeuxia angustifolia wetland is the fastest. In consideration of plant growth season, Deyeuxia angustifolia wetland has much more practical application value in purifying nitrogen. These results can provide references for the study on the purification function of wetlands and the control of non-point source pollution in Northeast China.

Complete Nitrogen Removal through Integrating Anammox and Autotrophic Denitrification in an UASB Reactor

Complete nitrogen removal was achieved through integrating anammox and autotrophic denitrification in an UASB reactor.The total nitrogen(TN)removal rate increased stepwise from 0.46 to 0.94 kg-N/(m3·d),with an effluent TN concentration of below 3.0 mg-N/L achieved.The process is relatively insensitive to the nitrite to ammonium ratio,achieving complete nitrogen removal when their ratio in the influent varied in the range of 1.35-1.55.The added S0 quantity in the system could be utilized to adjust the competition between autotrophic denitrifiers and anammox bacteria.High-throughput sequencing technology indicated that Candidatus_Kuenenia and Thiobacillus were the functional strains for anammox and autotrphic denitrification process,respectively,in the studied reactor.This result provides a theoretical and technical basis for the large-scale application of anaerobic ammonium oxidation process.

Experimental Study on Treatment of Ammonia Nitrogen in Landfill Leachate Flowing from MBR Using Catalytic Wet Peroxide Oxidation

Active iron catalysts with 5A molecular sieve as the carrier were prepared firstly, and then were used in the treatment of ammonia nitrogen in landfill leachate pretreated by MBR by using CWPO, finally the effects of preparation process of catalysts, assistants and reaction conditions on the removal rate of ammonia nitrogen were analyzed. The results show that the preparation process of catalysts and assistants had great effects on catalytic activity; when steeping fluid concentration was 2 mol/L and 0.01 mol/L cerium nitrate was used as an assistant, Fe-Ce/5A catalyst roasted for 3 h at 400 ~C had a good catalytic effect. As 10 g of Fe-Ce/5A catalyst was added to water sample, and landfill leachate pretreated by MBR reacted with 15 ml of H2 02 for 30 min at 60 ~C, the removal rate of ammonia nitrogen was up to 90.8%, that is, ammonia nitrogen concentra- tion decreased from 253 to 23 mg/L, reaching the national emission standard. Besides, the kinetic analysis of ammonia nitrogen removal reveals that the removal reaction of ammonia nitrogen conformed with pseudo first order kinetic equation. Thus, it is feasible to use this method to deeply treat landfill leachate pretreated by MBR.

Effects of Aeration Rates and Patterns on Shortcut Nitrification and Denitrification

The effects of aeration rates and aeration patterns on the oxidation of ammonia-nitrogen into nitrite were investigated. The influent high ammonia-nitrogen synthetic wastewater resembled to those of the catalytic process of the petrochemical refinery. The method involved the biological shortcut nitrification and denitrification lab-scale’s sequencing batch reactor (SBR) process based on intermittent aerations and aeration patterns. All the operations were carried out in a 20 L working volume SBR bioreactor, and the influent synthetic wastewater’s concentration was always 1000 mg/L ammonia-nitrogen NH4-N concentration at a C/N (carbon/nitrogen) ratio of 2.5:1. Effective shortcut nitrification to nitrite was registered at 1.1 mg-O2/L (i.e. 9 L-air/min) with 99.1% nitrification efficiency, 99.0% nitritation rate and 2.6 mg-NO3--N/L nitrate concentration. The best results with 99.3% nitrification efficiency were recorded when operating at 1.4 mg-O2/L (i.e. 12 L-air/min). According to these experiments, it results that the nitrite accumulation rate was related to aeration rate and cycle’s duration. However, at 1.7 mg-O2/L (i.e. 15 L-air/min), the system was limited by an increase in nitrate concentration with more than 5 mg/L which could be a point of reverse to conventional nitrification. The best total nitrogen (TN) removal was about 71.5%.

Immigration,transformation,and emission control of sulfur and nitrogen during gasification of MSW:Fundamental and engineering review

This paper proposes a comprehensive summary and analysis of an important issue during municipal solid waste(MSW)gasification-sulfur and nitrogen pollution.It provides an overview of the fundamentals of MSW and the basic aspects of nitrogen and sulfur elements.Their characteristics of immigration,transformation and distribution during gasification with control solutions in realized or potential engineering are also concluded.The analysis indicates that the complete scenario of the occurrence form of sulfur and nitrogen elements in MSW is difficult to obtain,owing to the diverse sources and complicated compositions.However,with the assistance of advanced characterization and quantification methods(XPS,XRD,TG-FTIR,et al.),the common sulfur-and nitrogen-containing compounds in both organic and inorganic states can be detected.Adjustment of gasification conditions can regulate the transformation of these elements for emission control.The multiple pollutants including H_(2)S,SO_(x),COS,NH_(3),HCN and NO_(x)cannot be eliminated by one-step treatment but a combination of adsorption and catalytic treatments may realize the control goal.This research aims to benefit meeting emission standards during MSW gasification and to provide a reference for other processes such as incineration,pyrolysis and other feedstocks like biomass and refuse derived fuel(RDF).

综合法二氧化氯生产系统废水除铬实例

以某浆纸厂含铬废水处理工程实例为研究对象,针对综合利用自产化学药品和现有设备开发的间歇性六价铬(Cr^(6+))综合处理系统,探讨了二氧化氯车间Cr^(6+)废水产生原因及性质,根据不同的反应池pH值、反应温度、反应时间和硫磺投加量对废水中Cr^(6+)还原效果的影响,确定了二氧化硫还原法去除Cr^(6+)的最佳反应条件,并结合实际生产数据,展示了Cr^(6+)还原效果。结果表明,有效去除高浓度含铬废水中Cr^(6+)的条件为:pH值=2~4、反应温度控制在40~60℃、硫磺投加量为理论反应所需投加量的1.4~1.6倍、反应时间40 min。3次二氧化氯车间停修废水出水中Cr^(6+)含量均低于0.005 mg/L,总铬含量均低于0.06 mg/L,符合《污水综合排放标准》(GB 8978—1996)中的要求,证实了间歇性Cr^(6+)综合处理系统处理的有效性。

Combined biologic aerated filter and sulfur/ceramisite autotrophic denitrification for advanced wastewater nitrogen removal at low temperatures

An innovative advanced wastewater treatment process combining biologic aerated filter （BAF） and sulfur/ ceramisite-based autotrophic denitrification （SCAD） for reliable removal of nitrogen was proposed in this paper. In SCAD reactor, ceramisite was used as filter and Ca （HCO3）2 was used for supplying alkalinity and carbon source. The BAF-SCAD was used to treat the secondary treatment effluent. The performance of this process was investigated, and the impact of temperature on nitrogen removal was studied. Results showed that the combined system was effective in nitrogen removal even at low temperatures （8℃）. Removal of total nitrogen （TN）, NH4＋ -N, NO3-N reached above 90% at room temperature. Nitrification was affected by the temperature and nitrification at low temperature （8℃） was a limiting factor for TN removal. However, denitrification was not impacted by the temperature and the removal of NO3 -N maintained 98% during the experimental period. The reason of effective denitrification at low temperature might be the use of easily dissolved Ca（HCO3）2 and high-flux ceramisite, which solved the problem of low mass transfer efficiency at low temperatures. Besides, vast surface area of sulfur with diameter of 2-6 mm enhanced the rate of microbial utilization. The removal of nitrate companied with the production of SO42-, and the average concentration of SO27 was about 240mg.L^-1. These findings would be beneficial for the application of this process to nitrogen removal especially in the winter and cold regions.

复合硫基质驱动自养反硝化脱氮除磷效能与微生物群落结构

针对单一硫基质驱动自养反硝化性能的缺陷,采用单质硫(S^(0))与天然铁硫矿石(FeS、Fe_(1-x)S、FeS_(2))两种矿物作为生物填料,构建3组复合硫基质填充床反应器(B1、B2、B3),探究了启动与稳定运行期间反应器对市政尾水深度脱氮除磷的效果与微生物群落结构的特征。结果表明,3组反应器均表出现较高的脱氮性能,NO_(3)^(-)-N去除率均随反应器水力停留时间(HRT)的延长而提高,当反应器HRT分别为1h(B1)、12h(B2)和9h(B3)时,均实现20mg/L NO_(3)^(-)-N完全去除。PO_(4)^(3-)-P与脱氮过程中产生的铁离子形成铁磷沉淀物而被去除,且PO_(4)^(3-)P的去除率与脱氮效果呈正相关。复合硫基质反应器的SO_(4)^(2-)/NO_(3)^(-)低于单一硫基质自养反硝化系统,硫酸盐产生量相应降低,且pH保持在6.3以上,无需添加pH缓冲剂。微生物群落结构分析表明,Thiobacillus(硫杆菌属)和Ferritrophicum(铁氧化菌属)是3组反应器中硫自养反硝化菌的优势菌属,在B1、B2和B3反应器的相对丰度分别为16.07%和31.24%、30.07%和50.19%以及30.20%和11.62%。复合硫基质提高了微生物群落丰度和物种多样性,从而表现出良好的脱氮除磷效果。

温度对活性污泥硝化反应的影响

温度是影响活性污泥法污水处理厂生物脱氮效果的重要因素。文章中实验采用1套SBR反应器小试装置,接种某城市污水厂曝气池好氧活性污泥,采用16S rDNA高通量测序技术,对活性污泥的菌群进行了检测,并以人工配水为进水,进行了1℃、5℃、8℃、11℃、17℃、19℃、21℃不同水温对活性污泥硝化反应影响进行实验。结果表明:污泥中存在Nitrosomonas(亚硝化单胞菌属)和Nitrospira(硝化螺菌属),相对丰度分别为0.074%和0.341%。21℃时硝化反应速率最大,达到4.3 mgNO_(3)-N/(gMLVSS·h);随着水温的降低,硝化反应速率下降,1℃时硝化反应速率仅为0.3 mgNO_(3)-N/(gMLVSS·h)。研究成果可为低温地区污水处理厂的优化运行,提高脱氮效果提供理论依据。

铁基质硅藻土处理油田含硫注入水的吸附性能研究

针对油田注入水中含硫而危害设备的问题,选择铁基质硅藻土脱硫剂(M-1),开展其在不同停留时间下的除硫效果和不同温度下的饱和吸附量实验。利用SEM、EDS等技术对M-1进行表征,利用热力学与动力学模型对实验数据进行拟合。结果表明,M-1表面为均匀细密的孔道,硫容能力强,主要成分为含40%铁的硅藻土;其吸附速度快,反应1 min时,水样中硫含量由原来的40.32 mg/L减少为0.029 mg/L,除硫率达到99.93%;该吸附过程符合Langmuir吸附模型和准二级动力学模型,属于单分子层吸附,是由化学吸附占主导地位,化学和物理吸附共同控制的过程,且该吸附是自发、混乱度降低的微放热反应。

无机硫自养反硝化处理污废水工程应用进展

系统阐述了以无机硫为电子供体的硫自养反硝化系统中微生物特性,分析了不同反应器中硫自养反硝化微生物的优势菌属、无机硫源氧化还原过程中涉及的功能酶,介绍了加快硫自养反硝化启动的方法,如减少S~0颗粒的粒径、外加磁场、添加硫代谢中间产物或牛血清蛋白等,重点归纳了近年来硫自养反硝化国内外的实际工程应用的情况,并展望了硫自养反硝化技术未来的发展方向,旨在为硫自养反硝化体系发展提供借鉴和参考。

锡精炼过程加硫除铜试验

针对锡精炼过程加硫除铜工艺,系统考察加硫量、加热温度和不同形态硫磺对锡铜分离的影响。研究结果表明,片状硫磺加硫量1∶1.2、加热温度300℃时,锡铜分离效果达到最佳,残余锡中的铜含量降低到了0.007%,锡铜分离率和锡直收率分别达到了99.18%、99.52%。该工艺可以有效除去粗锡中的杂质铜,具有操作简单、成本低及效率高的优点。

池塘种稻对养殖水体氮、磷去除效果及对鱼类生长的影响

旨在评估北方养殖池塘中生态浮床种植水稻对水质中氮、磷去除效果及其对养殖鱼类生长的影响。试验选取6个面积均为0.267 hm^(2)的试验池塘,分为试验和对照2个组,每组3个重复。试验组浮床水稻面积占池塘面积20%。试验组和对照组放养鱼类品种、规格、数量、搭配比例、饲料投喂等完全相同。试验期间,每半月监测一次水体总氮(TN)、铵态氮(NH_(4)^(+)-N)、硝态氮(NO_(3)^(-)-N)、磷酸盐(PO_(4)^(3-)-P)、总磷(TP)等水化指标,试验结束后测量各种鱼出池规格,统计各种鱼单位面积产量、总产量、成活率、饲料系数等。结果表明,6月15日试验开始时,试验组和对照组各项水化指标均无差异(P>0.05),7月1日至试验结束,试验组各项水化指标均显著低于对照组(P<0.05)。试验组TN、NH_(4)^(+)-N、NO_(3)^(-)-N、TP、PO_(4)^(3-)-P分别比对照组平均降低55.31%、70.25%、54.61%、68.68%、53.79%。试验结束时,试验组TN、TP分别为0.73 mg/L和0.12 mg/L,均达到了中国池塘养殖尾水排放一级标准。试验组鲫、鲂鱼出池规格和单位面积产量分别显著高于对照组(P<0.05)14.48%、12.68%和12.98%、15.01%,试验组单位面积总产量显著高于对照组(P<0.05)11.59%,试验组各种鱼成活率、鲢、鳙鱼出池规格及单位面积产量与对照组无显著性差异(P>0.05),试验组饲料系数显著低于对照组(P<0.05)7.48%。由此可见,池塘浮床种植水稻对养殖池塘水体中的N、P去除效果显著,并显著提高摄食鱼类产量及饲料利用率。