新型短程硝化反硝化工艺处理高浓度氨氮废水

研发了一种新型短程硝化反硝化工艺——ANITATMShunt,它通过特殊的自控系统来控制N2O的释放。采用500 L的SBR中试装置处理消化污泥脱水上清液,经过18个月的稳定运行表明:通过短程硝化反硝化途径可以实现90%的脱氮率,并且释放的N2O不足总脱氮量的0.7%。将通过pH值、温度和在线监测的NO-2-N浓度实时计算的亚硝酸浓度与亚硝酸浓度设定值进行比对,以便对曝气过程进行调控,从而抑制了N2O的释放并实现了对SBR短程硝化反硝化工艺的自动控制。同时证实了在低溶解氧条件下,由氨氧化菌(AOB)在短程硝化反硝化过程中产生的N2O并非与高亚硝酸盐浓度有直接关系,而是与游离亚硝酸浓度有关。     

生活污水生物处理领域中的CDM机会探讨

近年来,清洁发展机制(CDM)随着全球气候变化的加剧而迅速发展起来.以污水生物处理产生的重要温室气体(CO2,、CH4、N2O)为研究对象,从物质流(碳素流、氮素流、硫素流及磷素流)角度对污水生物处理中的CDM机会进行了探讨.结果表明:在污水生物处理领域中存在着较多的CDM机会.主要表现为:①好氧处理中高效节能充氧设备的选用及开发;②厌氧处理中光合细菌的光合作用固定CO2、强化厌氧过程中的H:产生及强化厌氧过程中的CH4产生以发展碳化工;③厌氧氨氧化及亚硝酸型硝化反硝化两种新型脱氮技术中存在着较多的CO2减量机会;④体系运行工况的优化及微生物种群的优化与调控,可有效地减少生物脱氮中产生的N2O;⑤优势微生物(聚磷菌)形成条件的优化.     

A2/O工艺的溶解氧控制及其对处理效果的影响

A2/O工艺是一种广泛使用的生物脱氮工艺,但在城市污水有机物浓度偏低的情况下,其存在反硝化碳源不足、全程硝化反硝化能耗高以及脱氮效果不稳定的问题,而控制溶解氧是解决上述问题的关键措施.为了研究溶解氧控制措施对A2/O工艺处理效果的影响,优化工艺运行,在成都航空港污水处理厂进行工程调试,并对溶解氧水平与风机能耗之间的关系进行定量分析.结果表明,A2/O工艺的好氧区采取低溶解氧策略(1.6 mg/L)能够改善脱氮效果,并能够保证其他主要污染物达标排放;同时,采用低溶解氧措施也有利于节能降耗,好氧区中点的DO为1.6mg/L较DO为2.0 mg/L时的风机能耗降低约8％.     

CANON工艺中N_2O的释放途径及影响因素

N_2O是一种强温室气体,而污水脱氮是N_2O释放的重要人为源。污水生物脱氮过程不仅增加了N_2O的释放潜能,且极有可能从水中转嫁到大气中。CANON作为一种新型脱氮工艺,在处理高氨氮废水时有其独特的技术优势,已广泛用于实际污水处理中,但是进一步的研究发现,该脱氮过程中N_2O的释放量却不容乐观。在微生物机理上,分别从短程硝化、厌氧氨氧化以及反硝化阶段分析N_2O可能的产生途径,并对NH_4~+-N、NO_2~--N、曝气量等关键影响因素进行了讨论。在综合分析CANON中N_2O的产生机理和影响因素的基础上,提出优化系统运行控制条件,避免NO_2~--N的积累和低DO浓度,培养适应高NO_2~--N浓度的微生物种群,实现N_2O的减量化。     

DO和填料对多级A/O工艺同步硝化反硝化的影响

为了解决低碳源污水脱氮效果不佳的问题,挖掘多级A/O工艺强化脱氮的潜力,在小试装置中开展了多级A/O工艺同步硝化反硝化的研究.结果表明,随着DO浓度的升高,同步硝化反硝化率呈现下降的趋势,低DO浓度(0.5 mg/L)下的同步硝化反硝化率高达37.4％.在系统中投加填料之后,系统的同步硝化反硝化脱氮能力得到提升.但是随着DO浓度的升高,填料对同步硝化反硝化的影响逐渐减弱.通过试验,提出了多级A/O工艺在较低溶解氧浓度下的梯级曝气运行控制模式,并确定了最佳运行工况,即各好氧区的最佳DO分别为0.5、1.0、1.5 mg/L,在低曝气能耗下实现了对氨氮的去除与较大程度的同步硝化反硝化.     

A2/O-曝气生物滤池深度生物脱氮除磷工艺分析

重点介绍了A<'2>/O-曝气生物滤池工艺的工作原理、运行方式及工艺特征.通过缩短A<'2>/O单元的泥龄,将硝化过程分离出去,使曝气生物滤池实现硝化.A<'2>/O单元在短泥龄条件下运行,有利于除磷及反硝化;曝气生物滤池在长泥龄条件下运行,有利于硝化效果的稳定和高效;从曝气生物滤池回流来的硝酸盐氮为A<'2>/O的缺氧段提供了充足的电子受体,为反硝化除磷提供了必要条件,最大限度地缓解了低C/N值污水在脱氮除磷过程中碳源不足的难题.小试结果表明,该工艺可以实现有机物、氮、磷的同步深度去除,出水水质满足<城镇污水处理厂污染物排放标准>(GB 18918-2002)的一级A排放标准.     

A~2O工艺的局限性及其改进

在城市污水处理众多的脱氮除磷工艺中,A2O工艺由于具有工艺简单,不易产生污泥膨胀,总水力停留时间较短且运行费用低等优点,被城市污水处理厂广泛使用。但该工艺由于硝化菌、反硝化菌和聚磷菌在污泥停留时间、溶解氧以及碳源等方面存在冲突,因此难以同时获得好的脱氮除磷效果。因此通过对上述制约因素的分析研究,在传统A2O工艺的基础上,开发出了Biowin工艺、UCT工艺、Phostrip工艺以及PAST工艺,这些工艺改进都是围绕SRT、DO以及碳源等因素进行的,都是为了给硝化菌、反硝化菌和聚磷菌创造最佳的生存环境。由于没有一种工艺是绝对可行的,因此应根据实际情况确定合适的工艺。随着短程硝化-反硝化理论、反硝化除磷等理论研究的不断深入,还会有更多的新工艺出现。     

A~2/O工艺的反硝化除磷特性研究

为了解传统A2/O工艺中反硝化除磷的作用及强化缺氧吸磷对系统同步脱氮除磷的贡献,以实际生活污水为处理对象,系统研究了缺氧段的反硝化除磷特性及其强化措施,并通过序批式试验考察了除磷微生物种群比例的变化.试验结果表明:稳定运行的A2/O系统中存在反硝化除磷现象,通过提高缺氧段的NO-3-N负荷,可使缺氧除磷贡献率从33.3%提高到53.3%,且系统的除磷率维持在95.4%以上;同时,好氧段的曝气量从400 L/h减少到260 L/h,节约了近35%;反硝化聚磷菌占聚磷菌的比例由35.4%提高到51.3%左右,微生物种群得到了优化.强化A2/O工艺的反硝化除磷功能,对提高低C/N值污水的脱氮除磷效率及降低运行能耗具有重要的意义.     

SBR生物脱氮过程中N_2O释放的影响因素研究

采用SBR反应器研究了在生活污水的生物脱氮过程中pH、DO和投加碳源对N2O释放的影响,并对各条件下N2O的产生特点进行了分析。结果表明,当控制初始pH值为6～9时,N2O释放的峰值均出现在曝气前期、对氨氮的去除率为30%～40%的阶段,当对氨氮的去除率达70%时,N2O的释放量显著下降;初始pH值为8时N2O的产生量最小,且N2O的释放量与硝化强度呈负相关。随DO浓度的增大,硝化过程中N2O的释放量逐渐降低。在硝化过程中将体系的DO控制在不同水平时,N2O的释放会呈现不同的特点:当DO为1.2～1.5mg/L时,N2O主要产生于硝化阶段,释放量明显大于反硝化阶段的;当DO为1.8～2.3mg/L时,硝化和反硝化阶段的N2O产生量相当;当DO为2.6～3mg/L时,N2O主要产生于反硝化前期。在反硝化开始时补充碳源(葡萄糖)可有效提高对总氮和硝酸盐氮的去除率,但同时会引起N2O释放量的显著上升。     

双泥SBR系统的短程硝化反硝化和反硝化除磷研究

针对我国中小城镇污水低C/N值的水质特点,考察了双泥法SBR工艺的脱氮除磷效果。结果表明:硝化反应器采用生物膜SBR并控制溶解氧为1.0mg/L进行连续曝气,可以实现短程硝化反硝化;在厌氧/缺氧反应器中,聚磷菌能同时利用硝酸盐和亚硝酸盐为电子受体进行反硝化除磷,从而降低了对有机碳源和溶解氧的需求以及能耗。小试系统对模拟城镇污水中COD、TN、TP的平均去除率分别为94.9%、81.2%、89.5%,出水水质达到了《城镇污水处理厂污染物排放标准》(GB18918—2002)的一级A标准。     

短程与全程硝化反硝化过程中N_2O产量比较

采用序批式活性污泥反应器(SBR)对生活污水短程及全程硝化反硝化过程中N2O的产生量进行了考察.结果表明,在进水氨氮浓度相同且不限制DO的条件下,全程硝化反硝化过程中N2O的总产生量为短程硝化反硝化的2倍左右;硝化类型不会影响反硝化过程对溶解性N2O的还原,无论以(NO2-)-N还是以(NO3-)-N为电子受体,反硝化过程均有利于降低N2O的浓度.     

Nitrous oxide emissions from secondary activated sludge in nitrifying conditions of urban wastewater treatment plants: effect of oxygenation level

In order to better understand the mechanisms of N(2)O emissions from nitrifying activated sludge of urban WWTPs, sludge from the Valenton plant (Paris conurbation) are subjected to lab-scale batch experiments under various conditions of oxygenation. The results show that the highest N(2)O emissions (7.1 microgN-N(2)OgSS(-1) h(-1) in average) occur at a dissolved oxygen (DO) concentration of around 1mgO(2)L(-1). These high emissions at low oxygenation (from 0.1 to 2 mg O(2)L(-1)) are due to two processes: autotrophic nitrifier denitrification and heterotrophic denitrification. Nitrifier denitrification always dominates, representing from 58% to 83% of the N(2)O production. This N(2)O production originating from nitrifying activated sludge becomes 8 times higher when nitrite is added at a DO of 1 mg O(2)L(-1); a decrease is observed both at higher and lower oxygenation. Heterotrophic denitrification represents less than 50% of the N(2)O production, decreasing from 42% to 17% when oxygenation increases from 0.1 to 2 mg O(2) L(-1). We show that ammonium oxidizing bacteria (AOB) can shift to nitrifier denitrification when oxygen is depleted in the environments including in the WWTPs, nitrite then plays the role of oxygen as the final electron acceptor. As opposed to what happens in nitrification, the end products of nitrifier denitrification are gaseous forms of nitrogen, where N(2)O is not negligible compared to N(2). Overall, N(2)O emissions represent 0.1-0.4% of oxidized NH(4)(+), depending on the oxygenation level. N(2)O emissions would range from 0.11 to 0.42 TN-N(2)O day(-1) for a tertiary treatment of the Paris wastewater effluents, consisting exclusively of activated sludge nitrification.     

Nitrification and denitrification as a source for NO and NO2 production in high-strength wastewater

Laboratory and half-technical scale experiments were performed to evaluate nitric oxide (NO) and nitrogen dioxide (NO2) production during biological N-elimination from wastewater with high ammonium concentration (about 700 mg N L-1). In a laboratory scale bioreactor with biomass retention, the ammonia oxidizer Nitrosomonas europaea and the denitrifier Paracoccus denitrificans were grown as reference organisms in co-culture in order to simulate the nitrifying and denitrifying community of wastewater treatment plants. Synthetic wastewater and sludge liquor from the municipal wastewater treatment plant in Lueneburg (Germany) were used. In the laboratory scale reactor, during the treatment of synthetic wastewater, 0.28% of the oxidized ammonium-N was released as NO-N by a pure culture of Nitrosomonas. A simultaneously nitrifying and denitrifying co-culture only released 0.04 to 0.2%. NO2 formation was not observed. NO production was much higher in sludge liquor. A pure culture of Nitrosomonas produced 0.52% NO + NO2-N (= NOx-N), a co-culture of Nitrosomonas and Paracoccus even 1.64% NOx-N. The production rate strongly depended on the media and the organisms used. In a co-culture of N. europaea and P denitrificans, Nitrosomonas was shown to be the most efficient NO producer. NO production increased with ammonium oxidation rate and with nitrite concentration of the medium. In synthetic wastewater, NO production was not influenced by reduced oxygen content. However, in sludge liquor NO production rate increased with decreasing O2 concentration. Here, for the first time, the formation of significant amounts of NO2 during simultaneous nitrification/denitrification could be demonstrated. In half-technical scale experiments, only 0.07% of the oxidized ammonium-N was released as NO-N from the nitrification stage. NO2 was not detectable. Release of nitric oxide from the denitrification stage was mainly diffusion limited and the amount produced did not exceed 0.0001%. A calculation on the basis of the results presented, revealed that biological treatment of nitrogen-rich wastewater is not a significant source for pollution of the atmosphere with NOx in industrial areas.     

污水处理中N2O的产生及减量化控制

N2O是一种重要的温室气体,针对污水处理生物脱氮过程中N2O的产生量、产生机理、影响因素及减量化控制等进行了综述。提出了采用DNA探针及定量PCR技术对生物脱氮中影响N2O产生的关键酶进行量化研究来实现N2O减量化控制的研究思路。     

SBR法短程硝化过程的氮平衡分析

采用SBR工艺处理生活污水,考察了短程硝化过程中可能存在的氮转化途径。结果表明,短程硝化过程中有52.6%的氨氮以非亚硝化的形式离开了反应系统,即存在52.6%的氮损失。其中,生成中间产物N2O、微生物合成作用以及同步硝化反硝化作用引起的氮损失分别占整体氮损失的15.5%、13.5%和71%。游离氨吹脱不是造成试验系统氮损失的原因。微生物种类、进水水质、环境条件和操作条件是影响氮转化途径的主要因素。     

Nitrous oxide emission during wastewater treatment

Nitrous oxide (N₂O), a potent greenhouse gas, can be emitted during wastewater treatment, significantly contributing to the greenhouse gas footprint. Measurements at lab-scale and full-scale wastewater treatment plants (WWTPs) have demonstrated that N₂O can be emitted in substantial amounts during nitrogen removal in WWTPs, however, a large variation in reported emission values exists. Analysis of literature data enabled the identification of the most important operational parameters leading to N₂O emission in WWTPs: (i) low dissolved oxygen concentration in the nitrification and denitrification stages, (ii) increased nitrite concentrations in both nitrification and denitrification stages, and (iii) low COD/N ratio in the denitrification stage. From the literature it remains unclear whether nitrifying or denitrifying microorganisms are the main source of N₂O emissions. Operational strategies to prevent N₂O emission from WWTPs are discussed and areas in which further research is urgently required are identified.     

Nitrous oxide production in high-loading biological nitrogen removal process under low COD/N ratio condition

Effects of influent COD/N ratio on N2O emission from a biological nitrogen removal process with intermittent aeration, supplied with high-strength wastewater, were investigated with laboratory-scale bioreactors. Furthermore, the mechanism of N2O production in the bioreactor supplied with low COD/N ratio wastewater was studied using 15N tracer method, measuring of reduction rates in denitrification pathway, and conducting batch experiments under denitrifying condition. In steady-state operation, 20-30% of influent nitrogen was emitted as N2O in the bioreactors with influent COD/N ratio less than 3.5. A 15N tracer study showed that this N2O originated from denitrification in anoxic phase. However, N2O reduction capacity of denitrifiers was always larger than NO3(-)-N or NO2(-)-N reduction capacity. It was suggested that a high N2O emission rate under low COD/N ratio operations was mainly due to endogenous denitrification with NO2(-)-N in the later part of anoxic phase. This NO2(-)-N build-up was attributed to the difference between NO3(-)-N and NO2(-)-N reduction capacities, which was the feature observed only in low COD/N ratio operations.     

Removal of 17α‐ethinylestradiol,salicylic acid,trimethoprim, carbamazepine and nonylphenol through biological carbon and nitrogen removal processes

This study investigated five different trace organic contaminants (TOrCs) (one hormone: 17α‐ethinylestradiol (EE2), two pharmaceuticals: salicylic acid (SA) and trimethoprim (TMP), one analgesic drug: carbamazepine (CBZ), and one surfactant metabolite: nonylphenol (NP)) removal efficiency at a full‐scale Advanced Wastewater Treatment Plant (AWTP). The AWTP achieved average EE2, SA and NP removal over 80% at the biological carbon removal stages. The results also showed a 66% removal of TMP at the nitrogen removal stages. CBZ was recalcitrant throughout the plant, due to its high solubility and low distribution coefficient between wastewater and sludge. Batch experiments were conducted on active and inactive secondary, nitrification and denitrification sludge by adding TOrCs to understand the removal mechanism through sorption and biodegradation. Sorption was the dominant mechanism to remove EE2, SA and NP in secondary treatment processes. In nitrification and denitrification processes, higher percentage of TOrCs removal through biodegradation were observed compared to removal through sorption.     

Mechanisms of N2O production in biological wastewater treatment under nitrifying and denitrifying conditions

Nitrous oxide (N₂O) is an important greenhouse gas and a major sink for stratospheric ozone. In biological wastewater treatment, microbial processes such as autotrophic nitrification and heterotrophic denitrification have been identified as major sources; however, the underlying pathways remain unclear. In this study, the mechanisms of N₂O production were investigated in a laboratory batch-scale system with activated sludge for treating municipal wastewater. This relatively complex mixed population system is well representative for full-scale activated sludge treatment under nitrifying and denitrifying conditions.Under aerobic conditions, the addition of nitrite resulted in strongly nitrite-dependent N₂O production, mainly by nitrifier denitrification of ammonia-oxidizing bacteria (AOB). Furthermore, N₂O is produced via hydroxylamine oxidation, as has been shown by the addition of hydroxylamine. In both sets of experiments, N₂O production was highest at the beginning of the experiment, then decreased continuously and ceased when the substrate (nitrite, hydroxylamine) had been completely consumed. In ammonia oxidation experiments, N₂O peaked at the beginning of the experiment when the nitrite concentration was lowest. This indicates that N₂O production via hydroxylamine oxidation is favored at high ammonia and low nitrite concentrations, and in combination with a high metabolic activity of ammonia-oxidizing bacteria (at 2 to 3 mgO₂/l); the contribution of nitrifier denitrification by AOB increased at higher nitrite and lower ammonia concentrations towards the end of the experiment.Under anoxic conditions, nitrate reducing experiments confirmed that N₂O emission is low under optimal growth conditions for heterotrophic denitrifiers (e.g. no oxygen input and no limitation of readily biodegradable organic carbon). However, N₂O and nitric oxide (NO) production rates increased significantly in the presence of nitrite or low dissolved oxygen concentrations.     

Effects of recirculation rate of nitrified liquor and temperature on biological nitrification–denitrification process using a trickling filter

In the modified Ludzack–Ettinger process, high‐energy input is required in a nitrification tank. To address this issue, a new biological nitrification–denitrification system was constructed with a trickling filter for nitrification. The effects of recirculation rate of nitrified liquor and temperature through the treatment of municipal wastewater were evaluated. The highest DN removal efficiency was observed at 6.5 h of hydraulic retention in the denitrification tank and 350% of recirculation rate of nitrified liquid against the influent flow rate. The DN removal efficiencies did not reach theoretical values for all conditions tested because the COD/N ratios in the influent often decreased to less than 5 g‐COD/g‐N and temperatures dropped to less than 15°C in winter. The former inhibited the denitrification process and the latter significantly decreased the bioactivity of nitrifying bacteria. As such, this system is suitable in tropical and subtropical areas with annual minimum temperatures of over 15°C.