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.

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.

Simultaneous phosphorus and nitrogen removal in a continuous-flow two-sludge system

The ability of simultaneous biological phosphorus and nitrogen removal was investigated in a lab-scale continuous-flow two-sludge system. Alternating anaerobic and anoxic conditions were combined with contact oxidation stage for treating raw municipal wastewater. Long-term experiments showed that the contradiction of competing for the organic substrate between denitrifying bacteria and PAOs （phosphorus accumulating organisms） in traditional phosphorus and nitrogen removal system has been resolved. The system can adapt to low influent COD/TN ratio （C/N）. Furthermore the SRT （sludge retention time） of nitrifying sludge and denitrifying phosphorus removal sludge can be controlled at optimal conditions respectively. The removal efficiency of COD, TP, TN, and NH4-N was 81.78%, 92.51%, 75.75%, and 84.47% respectively. It was also found that the appropriate influent C/N should be controlled at the range of 3.8-6, while the optimal C/N to the system ranged between 4-5, and the BFR （bypass sludge flow rate） should be controlled at 0.35 around.

Nitrogen and phosphorus removal in pilot-scale anaerobic-anoxic oxidation ditch system

To achieve high efficiency of nitrogen and phosphorus removal and to investigate the rule of simultaneous nitrification and denitrification phosphorus removal （SNDPR）, a whole course of SNDPR damage and recovery was studied in a pilot-scale, anaerobicanoxic oxidation ditch （OD）, where the volumes of anaerobic zone, anoxic zone, and ditches zone of the OD system were 7, 21, and 280 L, respectively. The reactor was fed with municipal wastewater with a flow rate of 336 L/d. The concept of simultaneous nitrification and denitrification （SND） rate （rSND） was put forward to quantify SND. The results indicate that： （1） high nitrogen and phosphorus removal efficiencies were achieved during the stable SND phase, total nitrogen （TN） and total phosphate （TP） removal rates were 80% and 85%, respectively; （2） when the system was aerated excessively, the stability of SND was damaged, and rSND dropped from 80% to 20% or less; （3） the natural logarithm of the ratio of NOx to NH4^＋ in the effluent had a linear correlation to oxidation-reduction potential （ORP）; （4） when NO3^- was less than 6 mg/L, high phosphorus removal efficiency could be achieved; （5） denitrifying phosphorus removal （DNPR） could take place in the anaerobic-anoxic OD system. The major innovation was that the SND rate was devised and quantified.

Optimum operation conditions of nitrogen and phosphorus removal by a biofilm-activated-sludge system

In the biofilm and activated sludge combined system, denitrifying bacteria attached on the fibrous carriers in the anoxic tank, while the sludge containing nitrifying and phosphorus removal bacteria was only recirculated between the aerobic and anaerobic tanks. Therefore, the factors affected and restricted nitrification, denitrification and phosphorus removal in a traditional A/A/O process were resolved. This paper describes the optimum operation conditions for nitrogen and phosphorus removal using this system.

Performance evaluation of a modified step-feed anaerobic/anoxic/oxic process for organic and nutrient removal

A pilot scale modified step-feed process was lmproved to increase nutrient/N ano P） ano organic removal operations from municipal wastewater. It combined the step-feed process and a method named ＂University of Cape Town （UCT）＂. The effect of nutrient ratios and inflow distribution ratios were studied. The highest uptake efficiency of 95% for chemical oxygen demand （COD） has been achieved at the inflow distribution ratio of 40/35/25. However, maximum removal efficiency obtained for total nitrogen （TN） and phosphorus at 93% and 78%, respectively. The average mixed liquor suspended solids （MLSS） was 5500 mg·L- 1. In addition, convenient values for dissolved oxygen （DO） concentration, and pH were obtained throughout different stages. The proposed system was identified to be an appropriate enhanced biological nutrient removal process for wastewater treatment plants owing to relatively high nutrient removal, sturdy sludge settle ability and COD removal.

Simultaneous denitrification and denitrifying phosphorus removal in a full-scale anoxic–oxic process without internal recycle treating low strength wastewater

Performance of a full-scale anoxic-oxic activated sludge treatment plant（4.0×10-5 m-3/day for the first-stage project） was followed during a year.The plant performed well for the removal of carbon,nitrogen and phosphorus in the process of treating domestic wastewater within a temperature range of 10.8℃ to 30.5℃.Mass balance calculations indicated that COD utilization mainly occurred in the anoxic phase,accounting for 88.2% of total COD removal.Ammonia nitrogen removal occurred 13.71% in the anoxic zones and 78.77% in the aerobic zones.The contribution of anoxic zones to total nitrogen（TN） removal was 57.41%.Results indicated that nitrogen elimination in the oxic tanks was mainly contributed by simultaneous nitrification and denitrification（SND）.The reduction of phosphorus mainly took place in the oxic zones,51.45% of the total removal.Denitrifying phosphorus removal was achieved biologically by 11.29%.Practical experience proved that adaptability to gradually changing temperature of the microbial populations was important to maintain the plant overall stability.Sudden changes in temperature did not cause paralysis of the system just lower removal efficiency,which could be explained by functional redundancy of microorganisms that may compensate the adverse effects of temperature changes to a certain degree.Anoxic-oxic process without internal recycling has great potential to treat low strength wastewater（i.e.,TN 〈 35 mg/L） as well as reducing operation costs.

Advanced sludge reduction and phosphorous removal process

An advanced sludge reduction process, i.e. sludge reduction and phosphorous removal process, was developed. The results show that excellent sludge reduction and biological phosphorous removal can be achieved perfectly in this system. When chemical oxygen demand ρ（COD） is 332 - 420 mg/L, concentration of ammonia p（NH3-N） is 30 - 40 mg/L and concentration of total phosphorous p（TP） is 6.0 -9.0 mg/L in influent, the system still ensures ρ（COD）〈23 mg/L, ρ（NH3-N）〈3.2 mg/L and ρ（TP）〈0. 72 mg/L in effluent. Besides, when the concentration of dissolved oxygen ρ（DO） is around 1.0 mg/L, sludge production is less than 0. 140 g with the consumption of 1 g COD, and the phosphorous removal exceeds 91 %. Also, 48.4% of total nitrogen is removed by simultaneous nitrification and denitrification.

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.

结晶磷回收联合A/O工艺处理猪场沼液工艺特性

厌氧发酵广泛用于猪场废水的前端处理,该过程将产生大量沼液。在中国受土地消纳能力限制,相当一部分猪场沼液不得不经处理后达标排放。猪场沼液含有高浓度污染物,目前仍缺少高效的处理工艺。化学磷回收与A/O工艺均已有较好应用基础,该研究尝试联合结晶磷回收与A/O系统设计了一套具有工程可行性的猪场沼液处理工艺,并以实际猪场沼液为处理对象,探究了该工艺的污染物去除效能与机制。A/O系统缺氧、好氧反应器水力停留时间(HRT,hydraulic retention time)分别为3.4、8.6 h,硝化液回流比为200%,结晶反应器HRT为15min。试验结果表明,所设计工艺获得了较好的污染物去除效果,TP(总磷)、NH_(4)^(+)-N、TN(总氮)、COD(化学需氧量)的去除率分别达到91.20%、94.67%、83.28%和96.18%;工艺同时实现了磷的高效回收,磷回收率(结晶单元对TP去除的贡献率)达到93.44%。缺氧、好氧单元对COD、TN、NH_(4)^(+)-N的去除贡献率分别为75.24%、47.66%、17.30%与24.76%、30.92%、62.75%;该工艺条件下,缺氧单元发生了明显的厌氧氨氧化过程,好氧单元可能通过同步硝化反硝化、厌氧氨氧化等过程实现了部分TN的去除。结晶单元主要结晶产物为MgNH_(4)PO_(4),同步去除了部分TN、NH_(4)^(+)-N,去除贡献率分别为21.39%、19.92%。该研究可为猪场沼液处理及资源回收提供参考。

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。

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.

填料尺寸投加比对同步生物脱氮效果的影响

为探究不同尺寸填料投加比对双污泥系统中脱氮降碳效果的影响。在两个序批生物反应器(SBR)中均投加15%的聚氨酯海绵填料形成两个双污泥系统,分别设置大尺寸(5 cm)与小尺寸(1.66 cm)填料体积投加比为1∶2和2∶1的实验组,处理实际生活污水。结果表明,大尺寸与小尺寸填料体积投加比为1∶2的双污泥系统脱氮降碳效果最佳,COD、NH_(4)^(+)-N、TN的平均去除率和反硝化碳源利用率分别为86.9%、96.07%、70.74%和26.67%。此外,大尺寸填料投加比例大的系统中,填料内部未能充分附着生物膜,建议在实际运行中增加小尺寸填料的投加比例从而高效完成生物脱氮。

锰改性人工矿质纤维载体同时硝化反硝化性能研究

填料的性能对于生物膜工艺脱氮除磷效果起着关键作用。通过MnO_(2)浸渍、MnCl_(2)氧化还原、MnO_(2)甲醇扩散和KMnO4氧化还原四种方法改性人工矿质纤维(ARW),并利用扫描电镜(SEM)和能量色散光谱(EDS)对改性前后的ARW进行形貌和元素分析。再通过实验研究改性前后的ARW在DO质量浓度为0.5 mg/L的环境中微生物群落及脱氮除磷效果。结果表明:1)改性后的ARW上成功负载了锰氧化物;2)负载锰氧化物的ARW系统脱氮除磷效果均优于原始ARW系统,其中MnO_(2)甲醇扩散改性ARW系统的脱氮除磷效果最佳,其稳定后对COD、NH_(4)^(+)-N、NO_(3)^(-)-N和TN的去除率相较于原始ARW系统分别提高了7.51%、17.02%、2.15%和11.19%;3)微生物的纲水平分析显示,MnO_(2)甲醇扩散改性ARW系统中γ-变形菌纲和α-变形菌纲分别占33.32%和13.07%,为原始ARW系统的1.18倍和1.19倍,其为水处理中脱氮除磷的优势菌纲。研究表明锰改性ARW可作为优良的水处理填料。

同步硝化反硝化除磷颗粒污泥的快速启动与强化

为了探究同步硝化反硝化除磷颗粒污泥系统的快速启动,本研究首先通过饥饿-饱食、逐步缩短沉淀时间的培养方式进行污泥造粒;其次通过定期投加30mg/L的NO_(2)--N,提供高浓度亚硝酸盐环境以强化氮磷去除;最后进一步提高系统氮负荷,考察其运行氮磷去除效率。系统在28天的培养下实现污泥快速颗粒化,MLSS稳定在5.6~6.2g/L,SVI30/SVI5达到0.96,颗粒沉降性能良好。通过亚硝酸盐强化,系统厌氧释磷量从3.51mg/L提升至29.4mg/L,同时NOB活性被抑制,实现短程硝化反硝化除磷。系统在C/N/P质量比为420/80/10的条件下,实现了99.85%的总氮去除与99.43%的磷去除。微生物群落分析表示在该启动策略下Acinetobacter菌属占据主导地位。

AAO-IMABR耦合工艺在市政污水处理中的应用

针对市政污水COD浓度低,NH_(3)-N与TN浓度相对较高,碳氮比严重失衡的水质特点,采用AAO耦合重离子微孔膜曝气生物膜反应器(IMABR)工艺进行处理。工程运行结果表明:COD平均质量浓度从126 mg/L下降到12.2 mg/L,NH_(3)-N平均质量浓度从32.3 mg/L下降到0.05 mg/L,TN平均质量浓度从38.8 mg/L下降到7.75 mg/L,NH3-N与TN去除率分别高达99.8%和80%。AAO-IMABR耦合工艺不仅能实现同步硝化反硝化功能,脱氮效率高,而且运行成本较低,处理出水稳定达标。

高铁列车集便器废水的同步除碳脱氮处理研究

随着铁路行业的快速发展,集便器废水处理成为近来相关部门比较关注的问题。为探究集便器废水经济高效的处理方法,研究采用短程硝化反硝化工艺+多级AO+固定生物膜活性污泥(IFAS)工艺处理实际的高铁集便器废水,评价其同步除碳脱氮的效果,验证该工艺的可行性。通过控制曝气池内的DO控制硝化反应进行至NO2--N阶段,然后在厌氧阶段将NO2--N转化为N2,实现脱氮。反应器NH4^(+)-N、TN、COD的去除率分别达到95%、90%和70%,TN负荷达到0.64 kg·N/m^(3)·d^(-1)。出水COD浓度低于400 mg/L,出水NH4^(+)-N浓度低于50 mg/L,TN浓度低于70 mg/L,达到了GB/T 31962—2015《污水排入城镇下水道水质标准》。短程硝化池中微生物群落分析表明,短程硝化优势菌为Nitrosomonas,在悬浮污泥和填料架占比分别为3.73%和5.88%。与传统活性污泥法相比,短程硝化反硝化工艺节省了25%的曝气能耗和45%的碳源消耗,多级AO的设计让脱碳除氮更加完全,提高出水水质,活性污泥法与生物膜法相结合,大大增加微生物的量,加快反应速率,可以节省污水处理构筑物的占地面积。从经济以及脱氮效率方面,短程硝化反硝化工艺有望成为集便器废水处理的主要工艺。相比于传统混凝土构筑物,一体化污水处理设备更适合集便器废水。

厌氧-限氧SBR处理低C/N生活污水SNDPR启动及N_(2)O释放

以厌氧-限氧方式运行序批式生物反应器(SBR),采用逐步降低进水碳氮比(C/N)方式驯化聚磷菌(PAOs)和聚糖菌(GAOs),启动了低C/N生活污水同步脱氮除磷过程(SNDPR),并考察了SNDPR内PAOs、GAOs间竞争关系及系统脱氮除磷性能过程N_(2)O释放特性。结果表明,C/N=7.0,SBR限氧段脱氮和除磷效率分别为83.5%和90%以上,N_(2)O产量为0.54 mg/L;C/N=3.0~3.5,脱氮和除磷效率分别降至60.1%和80.5%,N_(2)O产量达1.09 mg/L。SBR内不同反应阶段内源物质变化均表现出PAOs-GAOs共存特性。高C/N有利于微生物合成聚-β-羟基烷酸酯(PHA)并促进N_(2)O还原。C/N降低,SBR内污泥内源物质转化倾向于富集GAOs的降解特性。氨氧化菌(AOB)好氧反硝化过程及GAOs以PHA作为电子供体的内源反硝化过程促进了N_(2)O的释放。随C/N降低,SBR内污泥平均胞外聚合物(EPS)由43.4 mg/g VSS增至50.5 mg/g VSS,污泥容积指数(SVI)由99 ml/g增至127 ml/g。疏松型EPS(LB-EPS)内,蛋白质(PN)与多糖(PS)之比(PN/PS)随C/N增加而降低,污泥亲水性增加,不利于污泥脱水。