连续流反应器污水硝化过程中的N_2O释放

污水生物脱氮硝化阶段是温室气体一氧化二氮（N2O）的重要释放源。采用连续流反应器在2种进水氨氮（NH4-N,低氮反应器60 mg/L和高氮反应器180 mg/L）浓度条件下驯化硝化菌,并研究了不同初始NH4-N浓度和不同初始亚硝酸盐（NO2-N）浓度条件下所驯化硝化菌释放N2O的特征。结果表明在反应器运行过程中2个反应器释放N2O较少,均小于去除NH4-N浓度的0.01%;N2O的释放均随着初始NH4-N浓度或初始NO2-N浓度的升高而增加;不同初始NH4-N浓度条件下,低氮反应器驯化硝化菌的N2O释放率在0.51%~1.40%之间,高氮反应器驯化硝化菌在0.29%~1.27%之间;不同初始NO2-N浓度条件下,低氮反应器驯化硝化菌的N2O释放率在1.38%~3.78%之间,高氮反应器驯化硝化菌在1.16-5.81%之间。     

异养硝化-好氧反硝化菌ADN-42的脱氮特性

从大连海域典型繁茂膜海绵(Hymeniacidon perleve)中筛选出1株耐盐异养硝化-好氧反硝化菌,通过形态观察、生理生化实验和16S rRNA基因序列分析,确定其为假单胞菌属(Pseudomonas),命名为ADN-42。其异养硝化-好氧反硝化条件为氯化铵为氮源,柠檬酸三钠为碳源,温度30℃,C/N值为12,摇床转速150 r/min,NH+4-N初始浓度约300 mg/L,盐度为40 g/L Na Cl,在此条件下菌株84 h时NH+4-N去除率为75.4%,无硝态氮产生,亚硝态氮最大积累量为8.3 mg/L;将菌株投加到NH+4-N和NO-2-N混合体系中,混合系统比仅以NH+4-N为氮源的体系的NH+4-N去除速率提高了12.7%;研究结果表明Pseudomonas sp.ADN-42可能是一株有着良好应用前景的高效耐盐异养硝化-好氧反硝化菌。     

生物脱氮好氧阶段不同反应过程N_2O产量

在成功实现生活污水短程生物脱氮的基础上,采用体积为3 L的小试反应器,利用在线DO监测手段控制DO=1.0 mg·L~(-1),通过投加Na NO2的方式控制系统初始NO~(-2)-N=40 mg·L~(-1),以丙烯基硫脲(ATU)抑制NH+4-N的氧化过程,考察了生物脱氮好氧阶段不同反应过程中N_2O的产生量。结果表明,除缺氧反硝化细菌的反硝化过程外,好氧条件下,氨氧化菌(AOB)能够以NH+4-N作为电子供体,NO~(-2)-N作为电子受体,进行反硝化脱氮过程,其反硝化产物为N_2O。生物脱氮好氧阶段AOB的好氧反硝化和异养菌的缺氧反硝化反应中,N_2O的产量分别占分别占进水总氮(NH+4-N+NO~(-2)-N)的7.23%和7.80%。好氧阶段NH+4-N和NO~(-2)的氧化过程中,几乎没有N_2O的产生。     

高浓度氨氮污泥脱滤液的半硝化实验研究

对高浓度氨氮污泥脱滤液进行了半硝化实验研究。运行结果表明,反应器进水氨氮浓度在402 mg/L、HRT=5.5 h、温度为22～31℃、DO〈1.0 mg/L、pH值在7.4～8.2时,半硝化反应器出水的NO 2--N/NH3-N维持在1.13～1.32,且负荷达到1.76 kg N/（m3.d）,NO2--N/NOx...     

DO浓度对间歇曝气单级自养脱氮系统N2O排放的影响

以单级自养脱氮系统为研究对象,采用有效容积为15 L的SBBR反应器,系统进水NH+4-N浓度约为360 mg/L,控制温度为(30±2)℃,采用间歇曝气方式运行,曝气段DO浓度从2.4~2.6 mg/L逐渐下降到0.9~1.1 mg/L,研究了单级自养脱氮系统的脱氮性能与N2O排放情况。结果表明,反应器曝气段DO浓度从2.4~2.6 mg/L下降到0.9~1.1mg/L,系统TN去除率均达到80%,但在相同运行时间内的TN去除率依次降低,NH+4-N平均反应速率从0.19 mg/(L·min)降低至0.05 mg/(L·min),NO-3-N累计产生量稳定于14.9~16.5 mg/L,NO-2-N浓度在反应器内未产生明显的积累。随着曝气段DO浓度的下降,最大N2O释放速率逐渐降低,N2O累计释放量从73.8 mg下降到61.0 mg,N2O转化率介于2.4%~2.9%。     

温度对亚硝化及氧化亚氮释放的影响

采用批次实验的方法探讨了3种不同温度(15℃,25℃,35℃)对亚硝化及其过程中温室气体氧化亚氮释放情况。结果表明,温度对亚硝化过程及氧化亚氮的释放有显著影响。在15～35℃范围内,随着温度的升高,氨氧化率和亚硝化积累率逐渐升高,N2O释放量也逐渐增大,35℃可以作为适宜的亚硝化温度,平均氨氧化率为50.9%,亚硝化积累率为55.6%,NO2--N与NH4+-N出水浓度比为1.1,氨氧化率,亚硝化积累率和出水中亚硝氮与氨氮浓度比较合适,从而可以为厌氧氨氧化工艺提供合适的进水,但在此温度下平均N2O释放量相对较高,为1.494μg/g MLSS。     

碱度指示MBR中同步硝化反硝化的研究

在连续的操作环境下,通过改变在膜生物反应器(MBR)中的C/N和曝气量,研究碱度对同步硝化反硝化脱氮效果的指示作用。结果发现,在反硝化完全的情况下,出水碱度(330~440 mg/L)在硝化过程中较高并与出水TN表现出好的线性关系(Alk=3.22[N]+333.08,R2=0.85);在硝化完全的情况下,出水碱度(60~280 mg/L)在反硝化过程中较低并与出水TN也有很好的线性关系(Alk=-4.93[N]+317.86,R2=0.89)。实际消耗的碱度可以作为另一个指示因子(ΔAlkexper),实际消耗的碱度随出水的NH4+-N浓度升高而降低(ΔAlkexper=-3.85[N]+149.11,R2=0.88,出水NO3--N4.5 mg/L);实际消耗的碱度随出水的NO3--N浓度升高而升高(ΔAlkexper=3.68[N]+161.11,R2=0.88,出水NH4+-N5.5 mg/L)。虽然pH的变化有一定的规律,但是对SND脱氮效果指示不灵敏。     

同步硝化反硝化工艺中DO浓度对N2O产生量的影响

采用序批式生物膜反应器（SBBR）,在连续曝气全程好氧的运行条件下,考察不同溶解氧浓度对同步硝化反硝化脱氮性能及N2O产量的影响。控制溶解氧浓度恒定在1、2、2.5和3 mg/L。结果表明,DO为2 mg/L和2.5 mg/L时,氨氮去除率分别为97.9%和98.5%,同步硝化反硝化率均为99%。DO为2 mg/L时,系统中N2O产生量最低,为0.423 mg/L,占氨氮去除量的1.4%;DO为3 mg/L时N2O的产生量最高,为2.01 mg/L,是DO为2 mg/L时的4.75倍。系统中亚硝酸盐的存在可能是高溶解氧条件下N2O产量增加的主要原因,同步过程中没有NOx-的积累即稳定的SND系统有利于降低生物脱氮过程中N2O的产生量。     

分段进水多级生物膜反应器脱氮效能影响因素研究

采用分段进水多级生物膜反应器处理高氮低碳小城镇污水,考察负荷、溶解氧和温度对反应器脱氮效能的影响。实验结果表明:负荷、溶解氧和温度对反应器脱氮效能有显著影响。在水温为20～25℃,DO为5 mg/L,负荷为1 kgCOD/(m3.d),挂膜密度为30%,第1、3、6级分段进水,流量分配比为2∶2∶1的条件下,在反应器中可成功构建出高效同时硝化反硝化系统,出水COD、NH4+-N和TN浓度分别为33 mg/L、2.6 mg/L和29.4 mg/L,去除率分别为90.1%、96.0%和63.9%。当水温≤15℃时,硝化速率受温度的影响显著。     

分段进水SBR短程生物脱氮过程中N2O产生及控制

利用SBR,控制曝气量为60 L/h,利用在线pH曲线控制曝气时间,成功实现了短程生物脱氮过程,并考察了不同进水方式下SBR运行性能及N2O产量。结果表明,分段进水能够有效降低短程生物脱氮过程中外加碳源投加量。在原水进水碳氮比较低时,采用递增进水量的进水方式,能够有效降低生物脱氮过程中NO-2积累量,从而降低系统N2O产量。1次进水、2次等量进水和2次递增进水方式下,生物脱氮过程中N2O产量分别为11.1、8.86和5.04 mg/L。硝化过程中NO-2-N的积累是导致系统N2O产生的主要原因。部分氨氧化菌(AOB)在限氧条件下以NH+4-N作为电子供体,NO-2-N作为电子受体进行反硝化,最终产物是N2O。     

基于SIMULINK的硝化反应动力学模型的仿真

利用MATLAB/SIMULINK对序批式生物膜反应器内的氨氧化细菌与亚硝酸盐氧化菌的生化反应进行仿真预测。模型的验证结果表明,适当的选择模型中的溶解氧浓度、碱度以及温度3种参数,SIMULINK仿真动力学模型能够比较准确地对氨氧化细菌与亚硝酸氧化细菌处理生活污水的过程进行仿真和预测.NH4+-N、NO2--N和NO3--N 3种基质仿真值的绝对平均误差最大为15.88,最小为1.13;NH4+-N、NO2--N和NO3--N的Nash.Suttcliffe模拟效率系数分别为99.36%、98.64%和99.25%;此外,还对SIMULINK仿真动力学模型中的溶解氧浓度、碱度以及温度进行了灵敏度分析,结果表明,温度的灵敏度最大、溶解氧次之、碱度灵敏度相对最小。     

不同污泥源条件下ANAMMOX启动及其与反硝化协同脱氮对比

采用城市生活污水配水同时启动两组ASBR,R1接种好氧硝化污泥,R2按2∶1混合接种短程硝化和厌氧氨氧化污泥,研究2个ANAMMOX反应器启动的可行性及其差异。实验结果表明,R1和R2均可成功启动ANAMMOX,R1需130 d,R2仅需73 d;稳定期R1和R2反应器NH4+-N、NO2--N和TN去除率分别达95.30%、91.30%、76.28%和96.2%、98.3%、90.1%,且周期内NH4+-N、NO2--N和NO3--N降解规律相似;R1和R2反应器发生的主要反应为厌氧氨氧化,但同时存在反硝化作用;2组反应器稳定运行后污泥颜色、形态及微生物组成相似,经SEM观察多为球状菌。     

实时荧光定量PCR对A2/O短程硝化系统内氨氧化菌的定量分析

通过控制好氧区低DO浓度以及缩短好氧实际水力停留时间(actual hydraulic retention time,AHRT),在处理低C/N比实际生活污水的A2/O工艺中,成功启动并维持了短程硝化反硝化;系统亚硝酸盐积累率稳定维持在90%左右,氨氮去除率在95%以上。通过提取富集氨氧化菌(ammonia oxidizing bacteria,AOB)的基因组DNA,经两次常规PCR扩增和琼脂糖凝胶电泳,以纯化回收的DNA扩增片段作为实时荧光定量PCR检测AOB数量的DNA标准品,建立了检测AOB数量的实时荧光定量PCR标准曲线。利用实时荧光定量PCR技术比较了A2/O系统在不同运行条件及亚硝酸盐积累率情况下AOB菌群数量。结果表明,随着系统亚硝酸盐积累率的上升,系统内AOB菌群数量也大幅上升。全程硝化和短程硝化时,系统内的AOB菌群数量分别为5.28×109cells/g MLVSS和3.95×1010cells/g MLVSS。此外,亚硝酸盐积累率的下降相对于AOB菌群数量的下降有一定的滞后性。     

Simultaneous nitrification and denitrification by Pseudomonas sp. Y-5 in a high nitrogen environment

Pseudomonas sp. Y-5, a strain with simultaneous nitrification and denitrification (SND) capacity, was isolated from the Wuhan Municipal Sewage Treatment Plant. This strain could rapidly remove high concentrations of inorganic nitrogen. Specifically, Pseudomonas sp. Y-5 removed 103 mg/L of NH₄⁺-N in 24 h without nitrate or nitrite accumulation when NH₄⁺-N was its sole nitrogen source. The NH₄⁺-N removal efficiency (RE) was 97.26%, and the average removal rate (RR) was 4.30 mg/L/h. Strain Y-5 also removed NO₃^?-N and NO₂^?-N even in aerobic conditions, with average RRs of 4.39 and 4.23 mg/L/h, respectively, and REs of up to 99.34% and 95.81% within 24 h. When cultured in SND medium (SNDM-1), strain Y-5 achieved an NH₄⁺-N RE of up to 97.80% and a total nitrogen (TN) RE of 93.01%, whereas NO₃^?-N was fully depleted in 48 h. Interestingly, high nitrite concentrations did not inhibit the nitrification capacity of Y-5 when grown in SNDM-2, the RE of NH₄⁺-N and TN reached 96.29% and 94.26%, respectively, and nitrite was consumed completely. Strain Y-5 also adapted well to high concentrations of ammonia (~401.68 mg NH₄⁺-N/L) or organic nitrogen (~315.12 mg TN/L). Our results suggested that Pseudomonas sp. Y-5 achieved efficient simultaneous nitrification and denitrification, thus demonstrating its potential applicability in the treatment of nitrogen-polluted wastewater.

     

Influence of environmental factors on net N2 and N2O production in sediment of freshwater rivers

Denitrification is an important N removal process in aquatic systems but is also implicated as a potential source of global N₂O emissions. However, the key factors controlling this process as well as N₂O emissions remain unclear. In this study, we identified the main factors that regulate the production of net N₂ and N₂O in sediments collected from rivers with a large amount of sewage input in the Taihu Lake region. Net N₂ and N₂O production were strongly associated with the addition of NO₃ ^?-N and NH₄ ⁺-N. Specifically, NO₃ ^?-N controlled net N₂ production following Michaelis–Menten kinetics. The maximum rate of net N₂ production (V _max) was 116.3 μmol N₂-N m^?2 h^?1, and the apparent half-saturation concentration (k _m) was 0.65 mg N L^?1. N₂O to N₂ ratios increased from 0.18?±?0.03 to 0.68?±?0.16 with the addition of NO₃ ^?-N, suggesting that increasing NO₃ ^?-N concentrations favored the production of N₂O more than N₂. The addition of acetate enhanced net N₂ production and N₂O to N₂ ratios, but the ratios decreased by about 59.5 % when acetate concentrations increased from 50 to 100 mg C L^?1, suggesting that the increase of N₂O to N₂ ratios had more to do with the net N₂ production rate rather than acetate addition in this experiment. The addition of Cl^? did not affect the net N₂ production rates, but significantly enhanced N₂O to N₂ ratios (the ratios increased from 0.02?±?0.00 to 0.10?±?0.00), demonstrating that the high salinity effect might have a significant regional effect on N₂O production. Our results suggest that the presence of N-enriching sewage discharges appear to stimulate N removal but also increase N₂O to N₂ ratios.     

Start-up of sequencing batch reactor with <Emphasis Type="Italic">Thiosphaera pantotropha</Emphasis> for treatment of high-strength nitrogenous wastewater and sludge characterization

Biological treatment of high-strength nitrogenous wastewater is challenging due to low growth rate of autotrophic nitrifiers. This study reports bioaugmentation of Thiosphaera pantotropha capable of simultaneously performing heterotrophic nitrification and aerobic denitrification (SND) in sequencing batch reactors (SBRs). SBRs fed with 1:1 organic-nitrogen (N) and NH₄ ⁺-N were started up with activated sludge and T. pantotropha by gradual increase in N concentration. Sludge bulking problems initially observed could be overcome through improved aeration and mixing and change in carbon source. N removal decreased with increase in initial nitrogen concentration, and only 50–60 % removal could be achieved at the highest N concentration of 1000 mg L^?1 at 12-h cycle time. SND accounted for 28 % nitrogen loss. Reducing the settling time to 5–10 min and addition of divalent metal ions gradually improved the settling characteristics of sludge. Sludge aggregates of 0.05–0.2 mm diameter, much smaller than typical aerobic granules, were formed and progressive increase in settling velocity, specific gravity, Ca²⁺, Mg²⁺, protein, and polysaccharides was observed over time. Granulation facilitated total nitrogen (TN) removal at a constant rate over the entire 12-h cycle and thus increased TN removal up to 70 %. Concentrations of NO₂ ^?-N and NO₃ ^?-N were consistently low indicating effective denitrification. Nitrogen removal was possibly limited by urea hydrolysis/nitrification. Presence of T. pantotropha in the SBRs was confirmed through biochemical tests and 16S rDNA analysis.     

用微电极测定曝气量对SBR系统中硝化作用的影响

为了研究曝气量对硝化作用的影响,实验采用3个相同的SBR装置,分别在曝气量为4、10和16 L/h的条件下处理人工污水,并采用自制的溶解氧、NO3-、NH4+和pH微电极测定了活性污泥絮体内部微元环境中相应基质的浓度。结果表明,曝气量为4 L/h时,活性污泥絮体内存在厌氧微区,NO3--N浓度减小了,发生了反硝化作用;而曝气量为10 L/h和16 L/h时,活性污泥絮体内发生的都是硝化反应,且NH4+-N浓度的减小量、NO3--N浓度的增大量都随着曝气量的增大而增大,pH随着曝气量的增大而减小。     

Measurements and modeling of reactive nitrogen deposition in southeast Brazil

Increased reactive nitrogen (N_r) deposition due to expansion of agro-industry was investigated considering emission sources, atmospheric transport and chemical reactions. Measurements of the main inorganic nitrogen species (NO₂, NH₃, HNO₃, and aerosol nitrate and ammonium) were made over a period of one year at six sites distributed across an area of ∼130,000 km² in southeast Brazil. Oxidized species were estimated to account for ∼90% of dry deposited N_r, due to the region’s large emissions of nitrogen oxides from biomass burning and road transport. NO₂-N was important closer to urban areas, however overall HNO₃-N represented the largest component of dry deposited N_r. A simple mathematical modeling procedure was developed to enable estimates of total N_r dry deposition to be made from knowledge of NO₂ concentrations. The technique, whose accuracy here ranged from <1% to 29%, provides a useful new tool for the mapping of reactive nitrogen deposition.