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 influence factors in A/O process and decision trees for nitrification/denitrification system

In order to improve nitrogen removal in anoxic/oxic(A/O) process effectively for treating domestic wastewaters, the influence factors, DO(dissolved oxygen), nitrate recirculation, sludge recycle, SRT(solids residence time), influent COD/TN and HRT(hydraulic retention time) were studied. Results indicated that it was possible to increase nitrogen removal by using corresponding control strategies, such as, adjusting the DO set point according to effluent ammonia concentration; manipulating nitrate recirculation flow according to nitrate concentration at the end of anoxic zone. Based on the experiments results, a knowledge-based approach for supervision of the nitrogen removal problems was considered, and decision trees for diagnosing nitrification and denitrification problems were built and successfully applied to A/O process.

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.

Study on Characteristics in the Removal Process of Ammonia Nitrogen and Nitrate Nitrogen by an Isolated Heterotrophic Nitrification-Aerobic Denitrification Strain Rhodococcus Sp.

Removal of ammonia nitrogen and nitrate nitrogen by an heterotrophic nitrification-aerobic denitrification strain is an economical and effective method. In this article, a kind of heterotrophic nitrification-aerobic denitrification strain which has aerobic denitrification and heterotrophic nitrification ability was selected, and then was identified as rhodococcus sp. by 16S rRNA sequencing analysis and morphological observation. After that, carbon source utilization and nitrification- denitrification activity of this strain in different C/N, initial nitrogen concentration were studied. In addition, the assimilation and denitrification activities of ammonia and nitrate were also researched under the condition of nitrate and ammonia coexisted in the solution. The results show that the strain can grow in sodium acetate, glucose, sodium succinate and sodium citrate solutions, and it can not survive in sodium oxalate, sucrose and soluble starch solutions. Initial concentration and C/N were important for nitrogen removal rate. This strain can completely remove nitrate/ammonia when nitrate/ammonia concentration was lower than 15 mg l-1/80 mg l-1. the C/N of 10 and of 12 were the optimum C/N ratio in the nitrate and ammonia removal process respectively. pH value rose up sharply in the denitrification process and it increased relatively slowly in the nitrification process, which shows that pH is one of the most important factor inhibiting the denitrification removal process. Nitrite concentration was much higher in denitrification process than in nitrification process. In addition, this strain gave priority to utilizing ammonia as nitrogen source when ammonia and nitrate coexisted in the solution.

Nitrogen Release Kinetics and Nitrification-Denitrification on Surface Sediments under Aerating Disturbance Condition

[Objective] This study aimed to investigate the nitrogen release kinetics and nitrification-denitrification on surface sediments under aerating disturbance condition, with the purpose to solve the sediment nitrogen release and secondary pollution problems. [Method] The effect of in situ sediments aeration on the release of nitrogen pollutants was investigated, and the nitrogen release kinetics parameters were analyzed. The process of nitrification and denitrification under sediments aeration condition was investigated in laboratory. [Result] The nitrogen released from sediments was enhanced by aeration disturbance. The concentration of NH4＋-N and TN reached the maximum value in 30 min, and release rates were proportional to the disturbance strength. In this study, with the distance of aerator to the sediments surface of 0, 1, 2 and 3 cm, the suspended sediments concentrations were 3.52, 3.41, 3.26 and 3.01 g/L, respectively. Maximum release concentration of NH4＋-N and TN were 14.3, 13.8, 13.2, 12.2 mg/L and 33.21, 30.98, 29.83, 27.30 mg/L, respec- tively. In addition, both NH4＋-N and TN release kinetics could be described by Double Constant Equation as InC=A＋Blnt. Nitrification reaction occurred and was promoted by continued aerating to sediments.The concentration of NH4＋-N dropped down from 12.4 mg/L to 0.2 mg/L in 8 d, with the concentration of NO3--N increased to the maximum value of 10.8 mg/L. In addition, concentration of NO3--N and TN decreased from 10.8 mg/L and 37.4 mg/L to 0.36 mg/L and 23.2 mg/L after the stop of aeration for 12 d, indicating the occurrence of denitdfication reaction. Therefore, sediment aeration could accelerate nitrogen release and nitrification reaction, and with intermittent aeration, nitrogen could be removed from sediments in-situ by nitrification and denitrification. [Conclusion] The results provided technical reference for the in situ sediment remediation for the black-odor rivers in cities.

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.

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.

Influence of Carbon Source on Biological Nitrogen Removal by Immobilised Bacteria

Acetate, ethanol, and hydrolysed rice were used as external carbon sources in an ammonium removal process employing immobilised bacteria. The influence of the carbon source on the occurrence of free cells and total nitrogen removal efficiency was examined at C/N ratios of 1.5 (low), 2.5 (medium), and 3.5 (high). At the low C/N ratio, no free cells were found in the reactors and the use of acetate as the carbon source resulted in the highest total nitrogen removal efficiency, followed by ethanol and hydrolysed rice. The occurrence of free cells in reactors fed with acetate and ethanol led to a negligible increase in the total nitrogen removal efficiency with increasing C/N ratio. The results suggest that acetate is the most appropriate carbon source for nitrogen removal and that the number of free cells should be minimized to achieve the highest efficiency during long-term operation.

Isolation of aerobic denitrifier and characteristics of enhanced nitrogen removal in concentric-circles reactor with diversion wall

Three strains of aerobic denitrifiers,named as AT3,AT6 and AT7,were isolated from concentric-circles reactor with diversion wall possessing simultaneous nitrification and denitrification (SND) effect of 69%. The three strains are all gram-positive and rod-shaped,and their colonial colors are pale yellow,milk white and pink,respectively. Combined with 16SrDNA sequence homology comparison and biochemical tests,AT3 and AT7 were identified to belong to Rhodococcus,and AT6 to Gordonia. These bacterial strains could grow well in the medium with potassium nitrate as nitrogen source and sodium citrate as carbon source. Based on the enhanced nitrogen removal experiments of selected bacteria mixture for activated sludge,the inoculum amount of 5% was supposed to be proper. The mixed biomass suspension of selected strains with PVA immobilization was put into the concentric-circles reactor in order to study the characteristics of enhanced nitrogen removal after amplifying cultivation with inoculated amount of 5%. The experimental results show that the average removal efficiencies of ammonia nitrogen (NH3-N) and total nitrogen (TN) in the reactor enhanced with aerobic denitrifying bacteria using PVA are 92.18% and 79.14% respectively,increasing by 5.29% and 7.83% respectively compared with removal effects of control group without strains enhancement.

Nitrogen Removal in Wastewater Irrigation Systems and Its Influence on Groundwater Pollution

The experiment included ten soil columns and field investigation in 1 - 2 year duration. Data on the columns continuously flooded with waste water indicated that when total input of NH4-N reached to above 70% of the NH4-N adsorption capacity in soil the breakthrough would appear in the output . Adequate removal of nitrogen from the waste water would require at least 170 cm deep groundwater table . Fine textured soil would promote denitrification . The columns simulating discontinuous waste water irrigation indicated that denitrification existed only in the partial microenvironment of reduction .Groundwater table depth had no strong influence on nitrogen removal . The investigation in field revealed that the groundwater recharged with waste water was not polluted by nitrogen when the aeration profile was in finer textures owing to the combined contribution of nitrification and denitrification .

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.

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%.

固定化异养硝化-好氧反硝化菌在污水生物强化中的研究进展

异养硝化-好氧反硝化(Heterotrophic nitrification-aerobic denitrification,HN-AD)菌可以在有机碳存在的好氧条件下实现同时硝化和反硝化,广泛应用于各类污水处理过程中。综述了HN-AD菌株的脱氮特性和代谢途径,总结了其在污水处理中的应用和研究现状,比较了不同载体材料的优缺点,重点讨论了固定HN-AD菌株提高反应器处理效果和稳定性的作用机理。最后,展望了固定化HN-AD菌株在污水处理中面临的挑战和未来的研究方向。

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。

一株贝莱斯芽孢杆菌的分离鉴定及水体净化作用研究

从活性污泥中得到1株具有很强絮凝活性的贝莱斯芽孢杆菌菌株,以高岭土悬浊液絮凝沉淀法,通过对取样点菌种发酵液的絮凝效果进行筛选,分离得到1株高活性絮凝活性菌株W-5,经16S rDNA序列分析,菌株W-5为贝莱斯芽孢杆菌YL2021株.实验考察了菌株对水体中氨氮和NO_(3)^(-)-N和NO_(2)^(-)-N的去除能力,发现菌株W-5有明显氨氮去除效果,且对水体中NO_(3)^(-)-N和NO_(2)^(-)-N也具有一定的去除作用.后续工作将继续开展W-5的异养硝化-好氧反硝化(HN-AD)研究,旨在开发一株新型水处理菌种,用于生活污水絮凝和水中氨氮的去除.

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。

人工快渗系统短程硝化反硝化的协同启动及脱氮性能

为提高人工快渗(CRI)系统的脱氮性能,构建了好氧(O)/缺氧(A)两段式CRI系统处理模拟生活污水,采用NaCl-pH协同调控的方式启动短程硝化反硝化,考察了其对NH_(4)^(+)-N、TN去除的强化效果。结果表明,进水中投加质量浓度为6 000 mg/L的NaCl运行13 d后,O-CRI反应柱的NO_(2)^(-)-N积累率可达到71.7%,此时提高进水pH至8.8,NO_(2)^(-)-N积累率可增高至95.5%,NaCl-pH协同调控可成功启动短程硝化。O/A-CRI系统稳定运行期间NH_(4)^(+)-N、TN去除率均值分别达到97.6%、87.5%,比对照组分别提高了2.9、41.3个百分点。O-CRI反应柱内的脱氮功能菌以氨氧化菌(AOB)为主,其中相对丰度较高的菌属为Nitrosomonas、Nitrosospira,而以Nitrospira为代表的亚硝酸盐氧化菌(NOB)的活性由于被选择性抑制而致使其相对丰度大幅减小,从而保障了NO_(2)^(-)-N的高效稳定积累。短程硝化反硝化为CRI系统强化脱氮提供了一条高效低耗的新途径。

一株脱氮毕赤酵母Y 4的分离鉴定及其氨氮降解性能

当前水体氨氮污染严重,环境治理迫在眉睫,筛选高效安全的脱氮菌株可为废水脱氮提供更多选择。本研究从沼气发酵污泥中分离筛选能降解氨氮的菌株,使用18S rDNA序列分析,对筛选出的优良菌株进行种类鉴定;同时采用单因素试验和正交试验,探究菌株最佳脱氮条件[培养温度、初始pH值、盐浓度、碳氮比(C/N)]及其硝化、反硝化能力。结果表明,分离筛选得到1株具有较强脱氮能力的野生型毕赤酵母(Pichia sp.)菌株Y 4。在试验优化后,得到菌株Y 4的最适脱氮条件:培养温度25℃,初始pH值8.0、盐浓度(氯化钠浓度)30 g/L、C/N为30。在培养24 h后菌株Y 4对亚硝酸氮(NO-2 N)的降解率为80.50%,在培养48 h后菌株Y 4对氨氮(NH+4 N)的降解率达99.92%,且在24 h内菌株Y 4的异养硝化和好氧反硝化的速率分别达到6.25和6.71 mg/(L·h),表明毕赤酵母菌株Y 4对废水氮污染处理以及生物修复具有一定的应用价值与潜力。

好氧反硝化细菌Burkholderia sp.ZH8的脱氮特性与生物强化作用

针对传统生物脱氮处理含氮废水工艺流程复杂、脱氮效率低的问题,从实验室运行稳定的生物滤池筛选得到一株好氧反硝化菌株ZH8,该菌株具有较强的异养硝化和好氧反硝化能力.通过形态学、生理生化特征及16S rDNA序列分析,鉴定菌株ZH8为伯克氏菌(Burkholderia sp.).单因素试验表明,好氧反硝化菌株ZH8的最佳培养条件为:碳源为丁二酸钠,C/N为15,温度为30℃,转速为160r/min和pH值为7~8.此外,菌株ZH8不仅能以NH_(4)^(+)-N、NO_(3)^(-)-N或NO_(2)^(-)-N分别为单一氮源进行生长,而且在混合氮源条件下也可实现同步硝化反硝化作用.通过全基因组分析,菌株ZH8的异养硝化脱氮为谷氨酸脱氢酶途径的铵同化过程,好氧反硝化途径为:NO_(3)^(-)-N→NO_(2)^(-)-N→NO→N_(2)O→N_(2),碳代谢途径包括三羧酸循环、乙醛酸循环、糖酵解和戊糖磷酸.在采用纯菌ZH8为菌种培养的生物膜反应器中,反应运行至8~15d即可完成挂膜,系统可维持高效稳定的脱氮性能,NH_(4)^(+)-N、NO_(3)^(-)-N及TN的去除率均可达到90%以上.该菌株为生物处理领域提供了新型菌种资源,能够有效处理含氮废水,具有实际应用价值.