Combined removal of sulfur compounds and nitrate by autotrophic denitrification in bioaugmented activated sludge system

An autotrophic denitrification process using reduced sulfur compounds (thiosulfate and sulfide) as electron donor in an activated sludge system is proposed as an efficient and cost effective alternative to conventional heterotrophic denitrification for inorganic (or with low C/N ratio) wastewaters and for simultaneous removal of sulfide or thiosulfate and nitrate. A suspended culture of sulfur-utilizing denitrifying bacteria was fast and efficiently established by bio-augmentation of activated sludge with Thiobacillus denitrificans. The stoichiometry of the process and the key factors, i.e. N/S ratio, that enable combined sulfide and nitrogen removal, were determined. An optimum N/S ratio of 1 (100% nitrate removal without nitrite formation and low thiosulfate concentrations in the effluent) has been obtained during reactor operation with thiosulfate at a nitrate loading rate (NLR) of 17.18 mmol N L(-1) d(-1). Complete nitrate and sulfide removal was achieved during reactor operation with sulfide at a NLR of 7.96 mmol N L(-1) d(-1) and at N/S ratio between 0.8 and 0.9, with oxidation of sulfide to sulfate. Complete nitrate removal while working at nitrate limiting conditions could be achieved by sulfide oxidation with low amounts of oxygen present in the influent, which kept the sulfide concentration below inhibitory levels.     

The integration of methanogenesis with shortcut nitrification and denitrification in a combined UASB with MBR

A combined system consisting of an up-flow anaerobic sludge blanket (UASB) and an aerobic membrane bioreactor (MBR) was operated at 28-30 degrees C and pH 7.8-8.1 for the treatment of low-strength synthetic wastewater enriched with organic carbon and NH4Cl. The MBR slurry was recirculated into the UASB with a ratio of 50-800%. It was found that nitrite was able to accumulate steadily during the nitrification step in the MBR at a low TOC/NH4+-N ratio. The mixed liquid containing NOX(-)-N in the MBR was recirculated to the UASB, and denitrification rather than methanogenesis became the preferred pathway. Whereas, the less carbon requirement for denitrification via nitrite rather than nitrate allowed methanogenesis to proceed simultaneously in the same reactor. The combination of membrane filtration and partial nitrification in the MBR with simultaneous denitrification and methanogenesis in the UASB could stably reach 98% TOC removal and 48.1-82.8% TN removal with recirculation ratio increasing from 50% to 800%.     

Inactivation of ANAMMOX communities under concurrent operation of anaerobic ammonium oxidation (ANAMMOX) and denitrification

A concurrent operation of anaerobic ammonium oxidation (ANAMMOX) and denitrification was investigated in a well known UASB reactor seeding with both ANAMMOX and anaerobic granular sludges. ANAMMOX activity was confirmed by hydroxylamine test and the hybridization of biomass using the gene probes of Amx 820 and EUB 338 mixed. Denitrification was observed through the reductions of both COD and nitrate-nitrite concentrations under anaerobic/anoxic conditions. By providing a stoichiometric ratio of nitrite to ammonium nitrogen with addition nitrate nitrogen, a gradual reduction of ANAMMOX activity was found with an increase of COD concentration in a range of 100-400 mg l(-1). This is equivalent to the COD to N ratio of 0.9-2.0. The COD concentration was found to be a control variable for process selection between ANAMMOX reaction and denitrification. A reduction of COD and nitrite-nitrate concentrations in all reactors confirmed the undergone concurrent denitrification which thrives when sufficient organic matter is available. COD concentration over 300 mg l(-1) was found to inactivate or eradicate ANAMMOX communities.     

限氧自养硝化-反硝化生物脱氮新技术

限氧自养硝化—反硝化是部分硝化与厌氧氨氧化相耦联的生物脱氮反应过程,通过严格控制溶解氧在0．1～0．3mg·L^-1,实现硝化反应控制在亚硝酸阶段,然后以硝化阶段剩余的NH4^+作为电子供体,在厌氧条件下实现反硝化,该反应过程是完全的自养硝化—反硝化过程,具有能耗低、脱氮效率高、反应系统占地面积小等优点,适用于处理COD／NH4^+—N低的废水,是一种非常有应用前景的生物脱氮技术,文中详细介绍了限氧自养硝化—反硝化生物脱氮反应过程的研究进展,讨论了其微生物学机理及应用前景。     

Toluene mineralization by denitrification in an up flow anaerobic sludge blanket (UASB) reactor

In order to examine the effect of easily degradable substrate such as acetate on toluene mineralization by denitrification, an upflow anaerobic sludge blanket (UASB) reactor in steady state was set up. The experimentation was carried out in two stages. Initially, the reactor was fed with a carbon loading rate of 250 mg acetate-C L-1 d-1 as electron source. Nitrate loading rate (mg ) was adjusted to obtain a constant C/N ratio of 1.4. In the second stage, five toluene-C loading rates (TLR, mg toluene-C L-1 d-1), 25, 50, 75, 100 and 125, were assessed while total carbon loading rate and C/N were maintained constant at 250 mg C L-1 d-1 and 1.4, respectively. In so doing, acetate-C loading rate (mg acetate-C L-1 d-1) was gradually substituted by toluene-C. When acetate-C was the only electron source a dissimilative denitrifying process resulted as indicated by bicarbonate yield YHCO3, mg produced/mg carbon consumed) of 0.74 +/- 0.005 and denitrifying yield (YN2, mg N2 produced/mg consumed) of 0.89 +/- 0.042. The addition of different TLR did not affect the biological process as consumption carbon efficiency (CCE) values remained up to 95% +/- 3.5 and YHCO3 and YN2 values were higher than 0.71 +/- 0.03 and 0.88 +/- 0.01, respectively. Toluene mineralization by denitrification in continuous culture was successfully achieved. A simple UASB denitrifying reactor system has promising applications for complete conversion of nitrate, toluene and acetate into N2 and CO2 with a minimal sludge production.     

以N-甲基吡咯烷酮(NMP)为电子供体进行反硝化的可行性及实验研究

【目的】利用N-甲基吡咯烷酮(N-methylpyrrolidone, NMP)作为电子供体进行反硝化实验,以实现废水资源化。【方法】分别将NMP废水和葡萄糖作为电子供体加入到模拟的城市污水处理尾水中进行反硝化,比较2种电子供体去除硝酸盐的规律。同时考查NMP在反硝化过程中的氮素释放规律,并对所释放的氮素进行后续处理。最后再对它们作为电子供体时的反硝化污泥采用高通量测序,从微生物群落的角度分析NMP作为电子供体时其作用机理是否相同。【结果】当以NMP为电子供体时,硝酸盐氮的去除速率比葡萄糖为电子供体时要快67%。在8 h的反硝化结束后,剩余的硝酸盐氮、累积的亚硝酸盐氮和NMP本身所释放氨氮之和的总氮,与葡萄糖为电子供体时相近。【结论】NMP废水可以作为电子供体用于城镇污水处理厂的深度脱氮。对2种碳源所驯化的反硝化污泥样品进行高通量分析表明,NMP与葡萄糖作为电子供体用于反硝化反应时,相关的作用机理是不同的。该项研究结果对利用含氮杂环化合物作为电子供体进行反硝化具有重要的理论指导意义。     

一株耐盐的卓贝儿氏菌(Zobellella sp.)的分离鉴定及其硝酸盐还原能力

【背景】好氧反硝化是指在有氧条件下进行反硝化作用,使得硝化和反硝化过程能够在同一反应器中同时发生,是废水脱氮最具竞争力的技术。红树林湿地中蕴藏着丰富的微生物资源,分布着大量好氧反硝化微生物。【目的】了解耐盐微生物的脱氮机制,为含盐废水生物脱氮的工程实践提供理论依据,对一株分离于红树林湿地中的耐盐好氧细菌A63的硝酸盐异化还原能力进行分析。【方法】利用形态学特征及16S rRNA基因序列测定分析,对其种属进行了鉴定,采用单因子实验测定该菌在不同环境因子下的硝酸盐还原能力,并对其反硝化脱氮条件进行了优化。【结果】初步判定该菌株为卓贝儿氏菌(Zobellellasp.),其能在盐度0%-10%、pH5.0-10.0、温度20-40°C范围内进行反硝化脱氮和硝酸盐异化还原为氨(dissimilatorynitratereductiontoammonium,DNRA)作用。菌株A63最适生长碳源为柠檬酸钠(1.2 g/L),适宜脱氮盐度为3%、pH 7.0-7.5、温度30-35°C,且C/N为10。在最适脱氮条件下,该菌株12h内能将培养基中208.8mg/L硝态氮降至0,且仅有少量铵态氮生成...     

Combined removal of nitrate and carbon in granular sludge: Substrate competition and activities

Granular sludge from an upflow anaerobic sludge blanket reactor treating synthetic waste water containing a mixture of volatile fatty acids and nitrate showed a removal efficiency of nearly 100% for both nitrogen and carbon. This activity was achieved by a combined process of denitrification and methanogenesis under conditions of surplus carbon. Under batch conditions the two processes proceeded clearly separated in time with first denitrification dominating and excluding methanogenesis. However, as soon as nitrate was depleted, methane production was initiated, showing that the inhibition of methanogenesis by nitrate was reversible. Of the volatile fatty acids supplied to the reactor, i.e. acetate, propionate, and butyrate, the denitrifying population clearly preferred butyrate and propionate even though acetate could also be metabolized. Consequently, growth of syntrophic volatile fatty acid degraders was suppressed by the denitrifiers in cases of low C:N ratios in the medium, leaving acetate as the major substrate for methanogenesis.Abbreviations UASB upflow anaerobic sludge blanket - COD chemical oxygen demand - VFA volatile fatty     

Effects of temperature on simultaneous nitrification and denitrification via nitrite in a sequencing batch biofilm reactor

A laboratory scale experiment was described in this paper to enhance biological nitrogen removal by simultaneous nitrification and denitrification (SND) via nitrite with a sequencing batch biofilm reactor (SBBR). Under conditions of total nitrogen (TN) about 30 mg/L and pH ranged 7.15–7.62, synthetic wastewater was cyclically operated within the reactor for 110 days. Optimal operation conditions were established to obtain consistently high TN removal rate and nitrite accumulation ratio, which included an optimal temperature of 31 °C and an aeration time of 5 h under the air flow of 50 L/h. Stable nitrite accumulation could be realized under different temperatures and the nitrite accumulation ratio increased with an increase of temperature from 15 to 35 °C. The highest TN removal rate (91.9%) was at 31 °C with DO ranged 3–4 mg/L. Process control could be achieved by observing changes in DO and pH to judge the end-point of oxidation of ammonia and SND.     

Biological treatment of ammonium-rich wastewater by partial nitritation and subsequent anaerobic ammonium oxidation (anammox) in a pilot plant

In wastewater treatment plants with anaerobic sludge digestion, 15-20% of the nitrogen load is recirculated to the main stream with the return liquors from dewatering. Separate treatment of this ammonium-rich digester supernatant would significantly reduce the nitrogen load of the activated sludge system. Some years ago, a novel biological process was discovered in which ammonium is converted to nitrogen gas under anoxic conditions with nitrite as the electron acceptor (anaerobic ammonium oxidation, anammox). Compared to conventional nitrification and denitrification, the aeration and carbon-source demand is reduced by over 50 and 100%, respectively. The combination of partial nitritation to produce nitrite in a first step and subsequent anaerobic ammonium oxidation in a second reactor was successfully tested on a pilot scale (3.6 m(3)) for over half a year. This report focuses on the feasibility of nitrogen removal from digester effluents from two different wastewater treatment plants (WWTPs) with the combined partial nitritation/anammox process. Nitritation was performed in a continuously stirred tank reactor (V=2.0 m(3)) without sludge retention. Some 58% of the ammonium in the supernatant was converted to nitrite. At 30 degrees C the maximum dilution rate D(x) was 0.85 d(-1), resulting in nitrite production of 0.35 kg NO(2)-N m(-3)(reactor) d(-1). The nitrate production was marginal. The anaerobic ammonium oxidation was carried out in a sequencing batch reactor (SBR, V=1.6 m(3)) with a nitrogen elimination rate of 2.4 kg N m(-3)(reactor) d(-1) during the nitrite-containing periods of the SBR cycle. Over 90% of the inlet nitrogen load to the anammox reactor was removed and the sludge production was negligible. The nitritation efficiency of the first reactor limited the overall maximum rate of nitrogen elimination.     

Removal of ammonium via simultaneous nitrification-denitrification nitrite-shortcut in a single packed-bed batch reactor

A polyurethane packed-bed-biofilm sequential batch reactor was fed with synthetic substrate simulating the composition of UASB reactor effluents. Two distinct ammonia nitrogen concentrations (125 and 250 mg l(-1)) were supplied during two sequential long-term experiments of 160 days each (320 total). Cycles of 24h under intermittent aeration for periods of 1h were applied, and ethanol was added as a carbon source at the beginning of each anoxic period. Nitrite was the main oxidized nitrogen compound which accumulated only during the aerated phases of the batch cycle. A consistent decrease of nitrite concentration started always immediately after the interruption of oxygen supply and addition of the electron donor. Removal to below detection limits of all nitrogen soluble forms was always observed at the end of the 24h cycles for both initial concentrations. Polyurethane packed-bed matrices and ethanol amendments conferred high process stability. Microbial investigation by cloning suggested that nitrification was carried out by Nitrosomonas-like species whereas denitrification was mediated by unclassified species commonly observed in denitrifying environments. The packed-bed batch bioreactor favored the simultaneous colonization of distinct microbial groups within the immobilized microbial biomass. The biofilm was capable of actively oxidizing ammonium and denitrification at high ratios in intermittent intervals within 24h cycles.     

Nitrification-denitrification via nitrite accumulation for nitrogen removal from wastewaters

The biological nitrification-denitrification process is used extensively for removal of ammonia nitrogen from wastewaters. Saves in aeration, organic matter (for denitrification) and surplus sludge are achievable if nitrite accumulation is possible in the nitrification step. In this paper, operational parameters were studied for each process for maximum nitrite accumulation in the nitrification step and nitrite adaptation in the denitrification step. Nitrite accumulation during nitrification can be controlled by the dissolved oxygen (DO) concentration, presenting a maximum of 65% at around 0.7 mg DO/L. Denitrification can be adapted to nitrite and the process is stable if nitrite in the reactor is keep low. The performance of a continuous stirred tank reactor (CSTR) and an up flow sludge blanket reactor (USB) were compared. Once the operational parameters were established, a CSTR for nitrification and an USB reactor for denitrification were operated in series for 25 days. The process was stable and a steady state was maintained for 20 days, and 93.5% of overall nitrogen removal was achieved in the nitrification-denitrification via the nitrite process.     

Comparison of aerobic denitrification under high oxygen atmosphere by Thiosphaera pantotropha ATCC 35512 and Pseudomonas stutzeri SU2 newly isolated from the activated sludge of a piggery wastewater treatment system

AIMS: This study compares the ability of Thiosphaera pantotropha ATCC 35512 and the newly isolated Pseudomonas stutzeri SU2 to perform aerobic denitrification. METHODS AND RESULTS: Nitrate-supplemented basal medium in airtight crimp-sealed serum bottles containing an atmosphere of 92% oxygen was inoculated with Ps. stutzeri SU2 or T. pantotropha and incubated at 30 degrees C. During the 92-h incubation period, aerobic denitrification by Ps. stutzeri SU2 (NO3(-) - N removal 99.24%) was more efficient than that by T. pantotropha (NO3(-) - N removal 27.29%). CONCLUSION: Pseudomonas stutzeri SU2, which was isolated from the activated sludge of a sequencing batch reactor treating piggery wastewater, rapidly reduced the nitrate to nitrogen gas without nitrite accumulation. The nitrate removal rate of SU2 was 0.032 mmol NO3(-) - N g cell-1 h-1 after 44 h incubation. SIGNIFICANCE AND IMPACT OF THE STUDY: Pseudomonas stutzeri SU2 can be used in a full-scale sequencing batch system for efficient in situ aerobic nitrate removal from piggery wastewater.     

Shortcut biological nitrogen removal in hybrid biofilm/suspended growth reactors

A shortcut biological nitrogen removal (SBNR) process converts ammonium directly through nitrite to nitrogen gas, thus requiring less aeration and carbon. We evaluated a hybrid SBNR (HSBNR) reactor containing an anoxic tank followed by an aerobic tank and a settling tank. The aerobic tank was filled with polyvinyl alcohol sponge media (20%, v/v) to attach and retain ammonium oxidizers. Two configurations of the HSBNR reactor were tested for treating a wastewater with high strength ammonium and organic electron donor. The HSNBR reactors accumulated nitrite stably for 1.5 years and maintained a high free ammonia (FA) concentration (20–25 mg/L) and a low dissolved oxygen (DO) concentration (<1 mg/L) in the aerobic tank. Apparently, the biofilm carriers increased the solids retention time (SRT) for ammonium oxidizers, while high FA and low DO selected against nitrite oxidizers and promoted direct denitrification of nitrite in the aerobic tank. The significant amount of chemical oxygen demand (COD) was removed by shortcut denitrification of nitrite in the anoxic tank.     

一株海洋好氧反硝化细菌的鉴定及其好氧反硝化特性

【目的】从处理海洋养殖循环水的生物滤器生物膜中分离到1株具有好氧反硝化活性的细菌(菌株2-8),并进一步研究了该菌的分类地位及反硝化特性。【方法】采用16S rRNA基因序列分析对菌株进行初步鉴定,采用好氧培养技术,探讨了碳源种类、起始pH、NaCl浓度、C/N、温度和摇床转速对菌株2-8好氧反硝化活性的影响。【结果】该菌株的16S rRNA基因序列与Pseudomonas segetis FR1439T(AY770691)的相似性最高,达到99.9%,因此初步鉴定菌株2-8属于假单胞菌属(Pseudomonas sp.2-8)。碳源类型和C/N对其好氧反硝化作用的影响最为显著,以柠檬酸钠为唯一碳源,C/N为15时脱氮效率最高,低C/N导致亚硝酸盐的积累;其好氧反硝化的最适温度和pH分别为30℃和7.5;菌株2-8在摇床转速为160r/min下脱氮效果最好;NaCl浓度对其反硝化活性的影响不明显。【结论】在初始硝酸氮浓度为140mg/L,以柠檬酸钠为唯一碳源、C/N为15、pH为7.5、NaCl浓度为30g/L,30℃以及160r/min摇床培养的条件下,菌株2-8在48h内脱氮率可达92%且无亚硝酸盐积累。     

Evaluation of Anammox and denitrification during anaerobic digestion of poultry manure

Two approaches based on ne w process development and biological nitrogen transformation were investigated in a bench study for removing nitrogen as N2 gas from poultry waste while stabilizing the wastes. The process, known as "Anammox", was explored in batch anaerobic culture using serum bottles. The Anammox process involves the use of nitrite as an electron acceptor in the bacterially mediated oxidation of ammonia to yield N2. Studies are described wherein nitrite was added to poultry waste and the effects on ammonium levels were monitored. About 13-22% ammonium removal was observed with the inoculation of returned activated sludge, and the total ammonium reduction was not proportional to the reduction of nitrite, thereby suggesting that Anammox was less competitive under the conditions in our studies. The addition of nitrite and nitrate was not inhibitory to the process based on gas generation and COD reduction. The classical nitrogen removal process of nitrification followed with denitrification offers a more reliable basis for nitrogen removal from poultry wastes.     

Reactivation of biocatalysts after long-term storage and startup of the DEAMOX process

Studies of our laboratory have led to elaboration of the DEAMOX (DEnitrifying AMmonia OXidation) technology intended for removal of nitrogen contaminants from wastewater. The DEAMOX process comprises two anaerobic stages implemented by the same sludge biocatalyst, namely, denitratation (conversion of nitrate to nitrite) and anammox reaction (ANaerobic AMmonium nitrogen OXidation by nitrite). The results of reactivation of biocatalysts after their long-term storage (5 and 16 months) and successful startup of the DEAMOX process in two modifications (S- and O-) are described. An S-DEAMOX process was launched using a sludge biocatalyst with restored anammox activity of 20.1 mg N/g VSS/day; this process provided removal of 78% of nitrogen in reactor over 20 days. The launched O-DEAMOX process with the sludge biocatalyst with anammox activity of 6.1 mg N/g VSS/day provided for 87% removal of the total nitrogen compounds over 30 days. Two different electron donors were used at the stage of nitrate conversion to nitrite, namely, an inorganic donor, sulfide (S-DEAMOX), and an organic one, acetate (O-DEAMOX).     

The feasibility of using a two-stage autotrophic nitrogen removal process to treat sewage

The feasibility of using a two-stage autotrophic nitrogen removal process to treat sewage was examined in this study. The obtained results showed that total nitrogen (TN) could be efficiently removed by 88.38% when influent TN and chemical oxygen demand (COD) were 45.87 and 44.40 mg/L, respectively. In the first stage, nitritation was instantly achieved by the bioaugmentation strategy, and can be maintained under limited oxygen condition (below 0.2mg/L). The ratio of nitrite to ammonium in the effluent of the nitritation reactor can be controlled at approximate 1.0 by adjusting aeration rate. In the second stage, anammox was realized in the upflow anaerobic sludge blanket (UASB) reactor, where the total nitrogen removal rate was 0.40 kg Nm(-3)d(-1) under limited-substrate condition. Therefore, the organic matter in sewage can be firstly concentrated in biomass which could generate biogas (energy). Then, nitrogen in sewage could be removed in a two-stage autotrophic nitrogen removal process.     

Removal of multiple nitrogenous wastes by Aspergillus niger in a continuous fixed-slab reactor

A biofilter reactor, to which is attached a large variety of microorganisms, can be employed to treat circulating water in an intensive aquaculture system. Some nitrogen-containing wastes, such as ammonium and nitrite, are toxic to the aquatic organisms. The removal rates of the nitrogenous wastes are regarded as indices for the efficiency of treatment by biofilters. In this study, a fungus that was characterized as being able to remediate multiple nitrogenous wastes was identified as Aspergillus niger NBG5. In a continuous fixed-slab reactor, the heterotrophic fungus utilized ammonium, nitrite, protein, and glucose simultaneously. The fungus assimilated ammonium, nitrite and protein at rates of 0.247, 0.07 and 0.096 g-N/g-cell/day, respectively, at 22 degrees C. The remediation rates of ammonium nitrogenous wastes decreased by a factor of eight at 35 degrees C, while the specific growth rates slightly increased. For nitrogenous wastes, ammonium was a preferred substrate but its rate of consumption declined significantly as temperature increased. The nitrogen consumption rates were inconsistent with the cell yields at high temperature. Further analysis of consumption ratios of C/N revealed that cells grew predominantly from the carbon at high temperature. The A. niger NBG5 consumed glucose rapidly at specific rates of 2-2.5 g-C/g-cell/day at 35 degrees C in the presence of ammonium and nitrite; while sluggish consumption of glucose was observed in the protein substrate. The protein could serve as an alternative carbon source. Further ANOVA statistical analysis with P < 0.05 revealed no significant effects of temperature on the specific growth rates of A. niger on the SG-NH4 and milk-protein substrates, whereas significant effects on the C/N ratio at culture temperatures higher than 25 degrees C were observed. These findings indicated that the carbon utilization rate increased with high temperature, whereas nitrogen utilization increased as temperature declined. A suitable operational temperature was suggested, depending upon the amount of waste contents of C/N. A high temperature stimulates the use of carbon waste, while a low temperature favors remediation of all nitrogenous wastes.