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 removal of nitrogen and phosphorus from swine wastewater in a sequencing batch biofilm reactor

In this study, the performance of a sequencing batch biofilm reactor(SBBR) for removal of nitrogen and phosphorus from swine wastewater was evaluated. The replacement rate of wastewater was set at 12.5% throughout the experiment. The anaerobic and aerobic times were 3 h and 7 h, respectively, and the dissolved oxygen concentration of the aerobic phase was about 3.95 mg·L-1. The SBBR process demonstrated good performance in treating swine wastewater. The percentage removal of total chemical oxygen demand(COD), ammonia nitrogen(NH4+-N), total nitrogen(TN), and total phosphorus(TP) was 98.2%, 95.7%, 95.6%, and 96.2% at effluent concentrations of COD85.6 mg·L-1, NH4+-N 35.22 mg·L-1, TN 44.64 mg·L-1, and TP 1.13 mg·L-1, respectively. Simultaneous nitrification and denitrification phenomenon was observed. Further improvement in removal efficiency of NH4+-N and TN occurred at COD/TN ratio of 11:1, with effluent concentrations at NH4+-N 18.5 mg·L-1and TN 34 mg·L-1, while no such improvement in COD and TP removal was found. Microbial electron microscopy analysis showed that the filler surface was covered with a thick biofilm, forming an anaerobic–aerobic microenvironment and facilitating the removal of nitrogen, phosphorus and organic matters. A long-term experiment(15 weeks) showed that stable removal efficiency for N and P could be achieved in the SBBR system.

Simultaneous removal of ethanol, acetaldehyde and nitrogen oxides over V-Pd/γ-Al_2O_3-TiO_2 catalyst

V-Pd/γ-Al2O3-TiO2 catalysts with different vanadium contents were prepared by a combined sol-gel and impregnation method. X-ray diffraction （XRD）, N2 adsorption-desorption （BET）, X-ray photoelectron spectroscopy （XPS） and catalytic removal of ethanol, acetaldehyde and nitrogen oxides at low temperature （〈300 ？C） were used to assess the properties of the catalysts. The results showed that the sample with 1wt% vanadium exhibited an excellent catalytic performance for simultaneous removal of ethanol, acetaldehyde and nitrogen oxides. The conversions of ethanol, acetaldehyde and nitrogen oxides at 250 ？C were 100%, 74.4% and 98.7%, respectively. V-Pd/γ-Al2O3-TiO2 catalyst with 1 wt% vanadium showed the largest surface area and higher dispersion of vanadium oxide on the catalyst surface, and possessed a larger mole fraction of V4＋ species and unique PdO species on the surface, which can be attributed to the strong synergistic effect among palladium, vanadium and the carriers. The higher activity of V-Pd/γ-Al2O3-TiO2 catalyst is related to the V4＋ and Pd2＋ species on the surface, which might be favorable for the formation of active sites.

Mechanism of Simultaneous Nitrogen Removal and Electricity Generation by Microbial Fuel Cell

The working mechanism of MFC used for simultaneous nitrogen removal and electricity generation was studied.The results show that the electrode biofilms and suspension had different modes of electron transfer.The microorganisms growing on the electrodes and bioflocs could transfer electrons by direct contact and intermediaries respectively.The electrode biofilms and bioflocs were dominant in different functional spaces,and played a synergistic role in the process of contaminant removal,but showed a certain competitive relationship in the process of electricity generation.This study can provide a theoretical basis for the development of a new low-consumption wastewater treatment technology and promote technological innovation in wastewater treatment.

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.

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.

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.

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.

Simultaneous Removal of SO2 and NOx From Flue Gas

In this paper,the recent progress of simultaneous removal of SO_2 and NO_x process at home and abroad is reviewed.We mainly introduced calcium based absorbent catalytic oxidation method,complexation absorption process,Electron beam method et al,principle of each technology are described,and the development direction was put forward in the future.

Novel strategy of nitrogen removal from domestic wastewater using pilot Orbal oxidation ditch

A pilot-scale Orbed oxidation ditch was operated for 17 months to optimize nitrogen removal from domestic wastewater of average COD to total nitrogen ratio of 2.7, with particular concern about the roles of dissolved oxygen （DO）, mixed liquor suspended solids （MLSS） and return activated sludge （RAS） recycle ratio. Remarkable simultaneous nitrification and denitrification （SND） was observed and mean total nitrogen （TN） removal efficiency up to 72.1% was steadily achieved, at DO concentration in the out, middle and inner channel of 0.1, 0.4 and 0.7 mg/L, respectively, with an average M LSS of 5.5 g/L and RAS recycle ratio of 150%. Although the out channel took the major role in TN removal, the role of middle channel should never be ignored. The denitrification potential could be fully developed under low DO, high MLSS with adequate RAS ratio. The sludge settleability was amazingly improved under low DO operation mode, and some explanations were tried. In addition, a scries of simplified batch tests were done to determine whether novel microorganisms could make substantial contribution to the performance of nitrogen removal. The results indicated that the SND observed in this Orbal oxidation ditch was more likely a physical phenomenon.

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.

Insights into a novel nitrogen removal process based on simultaneous anammox and denitrification(SAD) following nitritation with in-situ NOB elimination

Simultaneous anammox and denitrification(SAD) is an efficient approach to treat wastewater having a low C/N ratio;however, few studies have investigated a combination of SAD and partial nitritation(PN). In this study, a lab-scale up-flow blanket filter(UBF) and zeolite sequence batch reactor(ZSBR) were continuously operated to implement SAD and PN advantages, respectively. The UBF achieved a high total nitrogen(TN) removal efficiency of over 70% during the start-up stage(days 1–50), and reached a TN removal efficiency of 96%in the following 90 days(days 51–140) at COD/NH_(4)^(+)-N ratio of 2.5. The absolute abundance of anammox bateria increased to the highest value of 1.58 × 107copies/μL DNA;Comamonadaceae was predominant in the UBF at the optimal ratio. Meanwhile, ZSBR was initiated on day 115 as fast nitritation process to satisfy the influent requirement for the UBF. The combined process was started on day 140 and then lasted for 30 days, during the combined process, between the two reactors, the UBF was the main contributor for TN(66.5% ± 4.5%)and COD(71.8% ± 4.9%) removal. These results demonstrated that strong SAD occurred in the UBF when following a ZSBR with in-situ NOB elimination. This research presents insights into a novel biological nitrogen removal process for low C/N ratio wastewater treatment.

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。

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.

Performance and recent improvement in microbial fuel cells for simultaneous carbon and nitrogen removal: A review

Microbial fuel cells（MFCs） have become a promising technology for wastewater treatment accompanying electricity generation. Carbon and nitrogen removal can be achieved by utilizing the electron transfer between the anode and cathode in an MFC. However,large-scale power production and high removal efficiency must be achieved at a low cost to make MFCs practical and economically competitive in the future. This article reviews the principles, feasibility and bottlenecks of MFCs for simultaneous carbon and nitrogen removal, the recent advances and prospective strategies for performance improvement, as well as the involved microbes and electron transfer mechanisms.

Response of aerobic sludge to AHL-mediated QS:Granulation,simultaneous nitrogen and phosphorus removal performance

The effects of different species and concentrations’signal molecules on aerobic activated sludge system were investigated through batch experiments.Results showed that the fastest NH^(+)_(4)-N oxidization rate and the most extracellular polymeric substances(EPS)secretion were obtained by adding 5 nmol/L N-hexanoyl-l-homoserine lactone(C_(6)-HSL)into the aerobic activated sludge.Further study investigated the correlation among N-acyl-homoserine lactones-mediated quorum sensing(AHLs-mediated QS),nutrient removal performances and microbial communities with the long-term addition of 5 nmol/L C_(6)-HSL.It was found that C_(6)-HSL-manipulation could enhance the stability and optimize the decontamination performance of aerobic granular sludge(AGS)system.Microbial compositions considerably shifted with long-term C_(6)-HSL-manipulation.Exogenous C_(6)-HSL-manipulation inhibited quorum quenching-related(QQ-related)activities and enhanced QS-related activities during the stable period.The proposed C_(6)-HSL-manipulation might be a potential technology to inhibit the growth of harmful bacteria in AGS,which could provide a theoretical foundation for the realization of more stable biological wastewater treatments.

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。

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。

羟氨强化硫自养反硝化与厌氧氨氧化协同脱氮效果

针对硫化物基质对硫自养反硝化与厌氧氨氧化协同脱氮体系的抑制问题,采用UASB反应器,通过逐渐增加进水羟胺质量浓度实现耦合体系高效脱氮。结果表明:在水力停留时间(t HRT)为4 h,进水NH^(+)_(4)-N和NO^(-)_(3)-N质量浓度分别为60和125 mg/L条件下,实现总氮去除负荷达1.05 kg/(m^(3)·d),其中厌氧氨氧化贡献率达76%~95%,是未投加羟胺时的1.55倍;羟胺的投加能够促进耦合系统污泥heme c合成和EPS(胞外聚合物)的分泌,NH_(2)OH与S^(2-)质量比超过0.024时有助于提高SAA(最大比厌氧氨氧化活性)值;厌氧氨氧化菌Candidatus_Kuenenia丰度和活性在羟胺存在时明显提高,从而与硫自养反硝化菌Thiobacillus、Thiothrix、Sulfurimonas、Sulfurovum和Sulfuritalea协同作用实现高效脱氮。