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.

Simultaneous nitrification and denitrification in step feeding biological nitrogen removal process

The simultaneous nitrification and denitrification in step-feeding biological nitrogen removal process were investigated under different influent substrate concentrations and aeration flow rates. Biological occurrence of simultaneous nitrification and denitrification was verified in the aspect of nitrogen mass balance and alkalinity. The experimental results also showed that there was a distinct linear relationship between simultaneous nitrification and denitrification and DO concentration under the conditions of low and high aeration flow rate. In each experimental run the floc sizes of activated sludge were also measured and the results showed that simultaneous nitrification and denitrification could occur with very small size of floc.

Effects of COD/N ratio and DO concentration on simultaneous nitrification and denitrification in an airlift internal circulation membrane bioreactor

The effects of chemical oxygen demand and nitrogen(COD/N)ratio and dissolved oxygen concentration(DO)on simultaneous nitrification and denitrification(SND)were investigated using an airlift internal circulation membrane bioreactor(AIC-MBR)with synthetic wastewater.The results showed that the COD efficiencies were consistently greater than 90% regardless of changes in the COD/N ratio.At the COD/N ratio of 4.77 and 10.04,the system nitrogen removal efficiency became higher than 70%.However,the nitrogen remova...

Nitrogen Removal by Simultaneous Nitrification and Denitrification via Nitrite in a Sequence Hybrid Biological Reactor

Sequence hybrid biological reactor （SHBR） was proposed, and some key control parameters were investigated for nitrogen removal from wastewater by simultaneous nitrification and denitrification （SND） via nitrite. SND via nitrite was achieved in SHBR by controlling demand oxygen （DO） concentration. There was a programmed decrease of the DO from 2.50 mg·L^-1 to 0.30 mg·L^-1, and the average nitrite accumulation rate （NAR） was increased from 16.5% to 95.5% in 3 weeks. Subsequently, further increase in DO concentration to 1.50 mg·L^-1 did not destroy the partial nitrification to nitrite. The results showed that limited air flow rate to cause oxygen deficiency in the reactor would eventually induce only nitrification to nitrite and not further to nitrate. Nitrogen removal efficiency was increased with the increase in NAR, that is, NAR was increased from 60% to 90%, and total nitrogen removal efficiency was increased from 68% to 85%. The SHBR could tolerate high organic loading rate （OLR）, COD and ammonia-nitrogen removal efficiency were greater than 92% and 93.5%, respectively,, and it even operated under low DO concentration （0.5 mg·L^-1） and maintained high OLR （4.0 kg COD·m^-3·d^-1）. The presence of biofilm positively affected the activated sludge settling capability, and sludge volume index （SVI） of activated sludge in SHBR never hit more than 90 ml·L^-1 throughout the experiments.

Performance of simultaneous nitrification and denitrification in lateral flow biological aerated filter

A new wastewater treatment facility—lateral flow biological aerated filter (LBAF) was developed aiming at solving energy consumption and operational problems in wastewater treatment facilities in small towns. It has the function of nitrification and removing organic substrate. In this study, we focused on the denitrification performance of LBAF and its possible mechanism under thorough aeration. We identified the existence of simultaneous nitrification and denitrification (SND) by analyzing nitrogenous compounds along the flow path of LBAF and supportive microbial microscopy, and studied the effects of air/water ratio and hydraulic loading on the performance of nitrogen removal and on SND in LBAF to find out the optimal operation condition. It is found that for saving operation cost, aeration can be reduced to some degree that allows desirable removal efficiency of pollutants, and the optimal air/water ratio is 10:1. Hydraulic loading less than 0.43 m h?1 hardly affects the nitrification and denitrification performance; whereas higher hydraulic loading is unfavorable to both nitrification and denitrification, far more unfavorable to denitrification than to nitrification.

Control strategy of simultaneous nitrification and denitrification in SBR system

The influence of main process parameters on simultaneous nitrification and denitrification （SND） in a sequencing batch reactor （SBR） were investigated while treating actual municipal sewage. The influent average concentration of CODcr and total nitrogen was 350mg-L-l and 35mg.L-l. The experiment indicated the following four operation control strategies： （1） When operation cycle was 6 hours, oxidation of organic pollutants and simultaneous nitrification and denitrification could well completed in the SBR reactor; （2） TN removal rate could be increased significantly, 40% higher than traditional SBR processes when idle period was set between influent and aeration; （3） The time of idle period could affect simultaneous nitrification and denitrification and the best time is 30 minutes; （4） Increase of sludge organic load may improve TN removal efficiency, but NH3-N removal efficiency declines.

光驱动SND生化工艺研究

为探寻菌藻结合实现光驱动同步硝化反硝化(SND)生化工艺的应用,在自制的AAO+沉淀池的反应器中通过人工配制进水的方式模拟对现实生活污水处理。经过四个月的运行成功实现光驱动SND生化工艺的稳定运行,在提供光照的条件下,降低约42.86%的曝气量出水依旧能达到一级A排放标准。培养过程中污泥产生大量的蛋白质(PN)和多糖(PS),PN/PS由2.89增长到5.05,实现污泥颗粒化,由于颗粒内部氧气传质的影响,实现内层缺氧,外层好氧的结构,为氨化细菌(AOB)、硝化细菌(NOB)和反硝化细菌的生长提供了适宜的场所,从而实现同步硝化反硝化(SND)脱氮过程的运行。根据计算得出,最终培养出的菌藻共生(ABS)系统相比原有系统曝气能耗更低,且具有更大的资源化潜力和脱氮潜力。

Simultaneous nitrogen and phosphor removal in an aerobic submerged membrane bioreactor

Simultaneous nitrification and denitrification （SND） effect and phosphor removal were investigated in a one-staged aerobic submerged membrane bioreactor on pilot-scale with mixed liquor suspended solids （MLSS） 19--20 g/L. The effects of DO concentration, sludge floc size distribution on SND were studied. Test results suggested that SND was successfully performed in the membrane bioreactor （MBR） and about 70% total nitrogen removal efficiency was achieved when DO concentration was set to 0.2-- 0.3 mg/L. The main mechanisms governing SND were the suitable sludge floc size and the low DO concentration which was caused by low oxygen transfer rate with such a high MLSS concentration in the MBR. In the meantime, phosphor removal was also studied with polymer ferric sulfate （PFS） addition and 14 mg/L dosage of PFS was proper for the MBR to remove phosphor. PFS addition also benefited the MBR operation owing to its reduction of extracellular polymer substances （EPS） of mixed liquor.

Traditional Nitrogen Removal Coupled with SND to Meet Advanced WWTP Standards at a Full Scale SBR Wastewater Treatment Facility

A Florida wastewater treatment facility studied how Simultaneous Nitrification Denitrification (SND) coupled with traditional nitrogen removal would be used to meet the state’s current advanced wastewater treatment nutrient criterion. This study examined the effect of these combined processes on the fate and transport of the nitrogen species during the treatment process. The effectiveness of nitrogen removal within the full scale sequential batch reactor system (SBR) and the extent of SND compared to nitrification and denitrification in the nitrogen removal process was also evaluated. Finally, the overall performance of the municipal wastewater treatment facility utilizing these combined processes was evaluated. Overall, this application reduced the total nitrogen to almost 6% of the permitted concentration of 3.0 mg/L. The combination of both processes also resulted in an actual ?concentration 93.7% lower than the acceptable theoretical ?concentration, which also resulted in effluent Total Inorganic Nitrogen nearly 80% lower than the permitted 3.0 mg/L effluent concentration. Further, the process produced a composite Total Nitrogen concentration that was 74% lower than the permitted concentration. This coupling of SND with traditional nitrogen removal resulted in a highly effective process to reduce nitrogen in the municipal wastewater effluent which is also attractive for potential implementation due to the low cost expenditure incurred in its utilization.

同步硝化内源反硝化除磷好氧颗粒污泥的储存与恢复

针对好氧颗粒污泥颗粒化时间慢等问题,进行了同步硝化内源反硝化除磷好氧颗粒污泥常温储存及活性恢复实验研究.结果表明,好氧颗粒污泥经过60d的常温储存后,颗粒的结构基本能保持稳定,但是颗粒污泥的活性大幅度降低,污染物去除率仅有储存前的30%~40%.将常温储存的颗粒污泥接种到反应器中,经过一定的调控手段,可以在60d内恢复好氧颗粒污泥的功能及活性.此外,经过储存与恢复,好氧颗粒污泥的群落结构也发生了明显变化.大部分的微生物的相对丰度变化可逆,经过储存和恢复可以恢复至储存前的状态(包括Defluviicoccus(GAOs)和Flavobacterium(PAOs)),重构同步脱氮除磷的微生物群落结构.

有机碳源对同时硝化/反硝化(SND)过程的影响

究了同时硝化 反硝化 (SimultaneousNitrificationandDenitrification ,SND)体系中有机碳源对氨氮去除的影响。实验结果表明 ,在氨氮初始浓度为 35mg L时 ,存在使氨氮降解率达到 99 5 %以上的有机碳源浓度区间 ,其CODCr浓度为40 0mg L～ 10 0 0mg L ;为保证反应后期体系中C N维持在微生物所需的水平 ,提出了补料的方式 ,使得氨氮降解不会出现停滞阶段 ,可以达到较好的去除效果 ;在周期为 8h的连续序批式 (SBR)操作中 ,采用较高的有机碳源初始进料值 ,并在反应过程中进行补料 ,可以很好的将出水氨氮的浓度维持在较低值 (<5mg L)

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(SB BR)中所表现出来的脱氮特性进行了试验分析,研究探讨生物膜法SN D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;SN D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N O3--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。

A/O生物脱氮工艺处理生活污水中试(二)系统性能和SND现象的研究

应用A/O中试装置处理实际生活污水,研究了低DO浓度下系统对有机物、氨氮和总氮的去除效果.研究结果表明,低DO浓度下COD和氨氮的平均去除率分别为85%和92%.由于进水C/N比仅为2.93,总氮平均去除率仅为64%,但提高亚硝酸氮积累率可以提高总氮去除率,当亚硝化率从15%增加到85%,总氮去除率将增加12%.氨氮去除率和硝化速率、总氮去除率具有较好的相关性.维持低DO浓度可以实现亚硝酸型同步硝化反硝化反应,基于氮的物料平衡可知它占系统总氮去除率的5%～12%,增加DO浓度将破坏同步硝化反硝化（SND）现象.

不同粒径零价铁对微氧脱氮系统的影响

构建了部分硝化反硝化厌氧氨氧化(SNAD)微氧体系,并定期向体系内投加120 mg不同粒径的零价铁(ZVI),从反应器运行情况、微生物性能以及群落结构来探究不同粒径ZVI对微氧系统的影响。研究结果表明,在50 nm粒径ZVI(50 nZVI)的介导下,系统的TIN去除率最终稳定在83.591%,电子传递活性(ETSA)是接种污泥的1.48倍,均高于其他粒径ZVI的影响。越小粒径ZVI越能促进胞外聚合物的产生,有利于活性污泥结构稳定。这都源于粒径越小的ZVI更容易被微生物吸附、利用。微生物群落结构与功能分析结果表明,在粒径越小的ZVI介导下的微生物群落多样性越高,群落结构也越复杂。ZVI介导会促进对氧需求不敏感的微生物的富集,样品中主要检测出Candidatus_Brocadia和Candidatus_Kuenenia两种厌氧氨氧化菌(AnAOB),且在50 nZVI影响下丰度最高,分别为4.650%和0.692%。nZVI介导下,AnAOB与Gemmobacter和norank_f_Comamonadaceae两种兼性厌氧型反硝化菌共同作用构成SNAD的脱氮途径。而在mZVI介导下,兼性厌氧型反硝化为主要脱氮途径。

沼液二级生化出水铁硫协同同步硝化-自养反硝化深度脱氮

针对沼液二级生化出水仍含高浓度硝态氮(NO-3-N)、氨氮等问题,文中研究了铁硫协同同步硝化-自养反硝化的影响因素。结果表明,在无外加碳源的条件下,铁硫协同同步硝化反硝化可有效提高TN、NO^(-)_(3)-N和氨氮的去除率。同时,在S/N为2的条件下,对TN、NO^(-)_(3)-N、氨氮去除率分别达到51.25%、83.63%、67.33%。氮去除动力学结果表明,TN去除规律在0~15 h内符合一级反应动力学特征,且其反应速率常数(0.0510 h^(-1))大于不投铁硫的空白组(0.0355 h^(-1))。微生物群落演变规律表明,铁刨花及硫代硫酸钠的投加会使微生物群落丰富度提高、多样性降低,且投加铁硫可显著提高自养反硝化菌[硫杆菌属(Thiobacillus)、铁杆菌属(Ferribacterium)]及异养反硝化菌[聚糖菌属(Defluviicoccus)、Candidatus_Competibacter、陶厄氏菌属(Thauera)]的丰度。

溶解氧和污泥粒径分布对城市污水SND影响

为了进一步探讨同步硝化反硝化的反应机理,采用SBR工艺,考察溶解氧和污泥粒径分布对城市污水同步硝化反硝化的影响。结果表明:低溶解氧(平均DO=0.5~0.8 mg/L)条件下,氮平衡计算证实SBR工艺发生了明显的SND现象,总氮中大约23.11%的氮是通过SND现象去除的。当DO浓度为0.5 mg/L时,硝态氮生成量与氨氮的减少量之比为0.454,硝化速率与反硝化速率基本相当。当DO浓度为4.296 mg/L时,硝化反应产生的氨氮的减少量与硝态氮的生成量相等,此时基本不发生SND现象。当SND发生时,污泥菌胶团颗粒的平均颗粒粒径仅为5.02μm^6μm,说明SND不是单纯的"微环境作用"的结果。

DO对亚硝酸型SND的影响

采用序批式生物膜反应器(Sequencing batch biofilm reactor,SBBR)处理南方地区城市污水,应用亚硝酸型同步硝化反硝化(SND)技术进行强化生物脱氮。在进水TN30mg·L-1、COD150～250mg·L-1、pH值7.20～7.60及常温(24～29℃)等条件下,研究了DO与TN去除率和亚硝酸盐氮积累率的关系。试验结果表明,在40～100L·h-1曝气量下均会得到稳定的亚硝酸型SND,当曝气量增加到120L·h-1时,会向全程硝化转化。曝气量60L·h-1时为SBBR反应器的最佳曝气条件,脱氮效果更好,亚硝酸盐氮积累率可达89.7%,TN去除率最高可达87.8%。

进水C/N对富集聚磷菌的SNDPR系统脱氮除磷的影响

为了解富集聚磷菌（PAOs）的同步硝化反硝化除磷（SNDPR）系统的脱氮除磷特性,采用延时厌氧（180min）/低氧（溶解氧0.5-1.0mg/L）运行的SBR反应器,以实际生活污水为处理对象,通过投加固态乙酸钠调节进水C/N值（约为11,8,4,3）,考察其对系统脱氮除磷特性及同步硝化反硝化（SND）脱氮率的影响.结果表明：C/N对系统的除磷性能没有影响,出水PO4^3--P浓度均稳定在0.3mg/L左右,这是由于系统内聚磷菌（PAOs）含量高,且在低氧段可同时发生好氧吸磷与反硝化吸磷.随着C/N的增大,出水NH4^＋-N浓度升高,C/N下降时,出水NO^3--N浓度升高.此外,随着C/N的减小,厌氧段反硝化所消耗的COD占进水COD的比例增大,SND可利用的内碳源-PHAs储存量减少,但PHV的利用率增加;当C/N为4-8时,SND现象最明显,SND脱氮率达50.8%,而其它C/N条件下,SND脱氮率都有相应程度的减弱.C/N为8时,系统出水综合指标最好,TN去除率高达80.8%.

不同厌氧时间对富集聚磷菌的SNDPR系统处理性能的影响

在延时厌氧（3h）/低氧（2.5h,溶解氧0.5~1.0mg/L）条件下运行的富集聚磷菌的同步硝化反硝化（SNDPR）系统中,以城市生活污水为处理对象,研究了不同厌氧时间（3.5,3,2,1.5h）对系统内碳源贮存以及脱氮除磷效果的影响.试验结果表明：厌氧时间为3.5h,反应器脱氮效果最好.厌氧时间为3h时,反应器除磷效果最好,出水PO43-浓度为0.35mg/L.厌氧时间从1.5h逐渐上升到3.5h时,厌氧末贮存的聚羟基脂肪酸-PHAs的量也随之增加;当厌氧时间从3h升至3.5h时,释P量反而下降,出水P浓度反而升高.这说明增加厌氧时间有利于强化内碳源贮存,但过长的厌氧时间反而不利聚磷菌种群的富集.运行51个周期之后在厌氧时间为1.5h和2h的反应器内出现非丝状菌膨胀;反应周期内p H值的变化曲线可以作为反应各个过程的指示参数.