Nitrifying Capacity Research Articles

Diversidad de especies nativas de Halomonas con capacidad nitrificante aisladas de criaderos de Litopenaeus vannamei

El objetivo de la investigación fue identificar cuáles son las especies del género Halomonas, con capacidad nitrificante, aisladas de sedimentos de criaderos de Litopenaeus vannamei provenientes de langostineras de Tumbes-Perú. A partir del sedimento de 3 criaderos de langostinos en tiempo de cosecha, se obtuvo una muestra representativa, a la cual se realizó un pre-enriquecimiento en Caldo Marino por 48 horas, luego se cultivó en Agar Marino, hasta la observación de colonias características del género Halomonas. Los cultivos obtenidos fueron identificados fenotípicamente a nivel de especie, para luego evaluar su capacidad nitrificante según la metodología de Griess-llosvay. Como resultados se obtuvo el aislamiento de 5 cultivos bacterianos, dos identificados como H. sulfidaeris y 3 como H. salina; todos los cultivos evidenciaron capacidad de reducir el nitrato a nitrito eliminando el amonio del medio. Se concluye que en el sedimento de criaderos de Litopenaeus vannamei ubicadas en Tumbes-Perú, están presentes las especies H. sulfidaeris y H. salina, con capacidad nitrificante, que permiten la eliminación del amonio, la cual se desarrolla como una opción eficaz para el tratamiento de agua residuales salinas de amonio.

Зміна азотного режиму сірого лісового крупнопилувато-легкосуглинкового ґрунту за різних систем удобрення та хімічної меліорації

The results of research in a stationary study, based in 1992 on gray forest coarse-grained loamy soil, on the impact of long-term chemical reclamation and0,0 various supply systems (mineral, organic, organo-mineral) on the nitrogen regime. Nitrogen is extremely important in agriculture, as all processes, photosynthesis, volume of substances and distribution of the level of yield and its quality are impossible without this element. In the total coverage of the country, the share of soils of forest origin exceeds 33 %, and among agricultural lands – 25 %. Given the content of humus and its total reserves, the integrated indicator of soil formation and the most important characteristic that determines the overall habit of the soil, in the articles above, change it from the above factors. It can also be shown that the content of gross nitrogen reflects the humus content, which is determined and differs from the humus content of the residual. There is a high density correlation between these indicators for all different studies (r = 0,991). The obtained data indicate that only with the use of greens and by-products of precursors and measured doses of mineral fertilizers with the use of liming achieved by the size of the total nitrogen to the initial level. The growth of the composition is 0,36 – 0,45 t / ha and in this case we can state the expansion of its reproduction. Only after mineralization nitrogen of organic compounds becomes available to plants. The form of nitrogen, which is easily hydrolyzed, is a fairly reliable indicator of the provision of this element. To classify the test content with the content of mobile compounds 81,2 – 103 mg / kg belong to the user groups with a very high degree of supply, but the degree hydrolyzes organic substances in high quantities (9,6 – 10,2 %). With the combined use of green manures, non-marketable plant products, single doses of mineral fertilizers in a combination of lime achieved growth of 27,5 % on the restoration to control of this form of nitrogen. For the above complex of nutrients at an increased content of 16,5 mg/kg to control the amount of N-NO3- + N-NH4 +, as well as 7,4 mg / kg of nitrifying capacity of the soil. The studied gray forest soils belong to the group of soils with low humus content and its total reserves, which are inherited from the original pedogenesis and modern soil formation processes. Under the influence of a set of agronomic measures for a long time the type of humus does not change, which indicates the invariability of the direction of soil formation

Micro-aeration with hollow fiber membrane enhanced the nitrogen removal in constructed wetlands.

The nitrogen removal efficiency in constructed wetlands (CWs) was largely affected by the dissolved oxygen (DO). In this study, micro-aeration with different numbers of hollow fiber membrane modules (HFMEs) was adopted to increase the oxygen availability and improve the nitrogen removal efficiency in CWs under different air temperatures and different hydraulic retention time (HRT). Compared to the plant oxygen release (ROL) of wetland plants and traditional mechanical aeration, HFME increased the oxygen availability and enhanced the nitrogen removal efficiency in CWs. The COD and NH4+-N removal efficiencies increased with the increase of the HMFE. TN removal efficiency was increased by 8~16% after the application of HFME in CWs in the high-temperature stage. However, less HFME in CW-M1 realized the highest TN removal efficiency in low- and medium-temperature stages. At low temperature after 4-day HRT, the DO concentration respectively reached 6.25 mg L-1 and 3.25 mg L-1 in the upper zone and the bottom of CW-M1. The TN removal efficiencies in the upper zone of CW-M1 (60.69%) and the bottom of CW-M1 (64.98%) were all significantly higher than those in the upper zone of CK (35.98%) and the bottom of CK (39.9%). In addition, the microbial biomass and community analyses revealed that CW-M1 showed the most nitrifying bacteria and the best metabolic activity of bacteria. HEMF in CW-M1 also increased the nitrifying capacity from 0.12 to 0.46 mg kg-1 h-1. The application of HFME in CWs accelerated the nitrification process by enhancing nitrifying bacteria and less HFME realized the highest TN removal efficiency through nitrification-denitrification processes. Graphical abstract The application of hollow fiber membrane modules in CWs enhanced the pollutants(TN and COD)removal efficiencyinthe process of biologicalnitrification-denitrification andincreased the number of nitrifying bacteria.

Isolation of ammonium- and nitrite-oxidizing bacterial strains from soil, and their potential use in the reduction of nitrogen in household waste water

Currently, nitrogen has become the main element of water pollution, causing riverine, lacustrine and coastal eutrophication. The continuous contamination of aquifers and the absence of planned water resource utilization, boost its scarcity, and has been the only way in which our societies become aware of the urgent need to process the generated wastewater. The objective of this research was to evaluate the nitrifying capacity of different autochthonous bacterial isolates from soils from nearby sources of domestic wastewater drainage. For this, bacteria were isolated from Pirro River, contaminated with nitrogen of domestic sewage. Nitrifying bacteria were counted by serial dilution and agar plates, and were isolated until obtaining axenic colonies. These were identified by biochemical batteries or genetic sequencing, and the quantification of their nitrifying capacity was obtained by the methods 4500- NH4 + -F and 4500-NO-2-B, all between September 26, 2011 and March 16, 2014. A total of seven strains of nitrifying microorganisms were isolated and purified, including four Streptomyces sp., one Pseudomonas putida, one Sphingomonas sp. and one Aeromonas sp. We found that there were 2.23 x 105 UFC/g of soil of ammonium oxidizing bacteria and 2.2 x 104 CFU/g of soil of nitrite oxidizing bacteria in the samples. The quantification of the nitrifying capacity of the strains by colorimetric methods, determined that the maximum ammonium removal capacity was 0.050 mg N/L/day and 0.903 mg N/L/day of nitrite. The collection of few strains of nitrifying organisms and a low CFU count, can be attributed to the technique used, since this only recovers 1 % of the microorganisms present in a sample, which, however, is acceptable for studies which main purpose is to obtain cultivable microorganisms. Future research should consider removal tests with higher ammonium and nitrite levels, to find the maximum capacity of the isolated microorganisms, and evaluate their potential use in wastewater treatment systems.

Promotion of nitrifiers through side-stream bioaugmentation: a full-scale study.

Bioaugmentation of nitrifiers from a side-stream treatment is an efficient method for boosting the mainstream process at a wastewater treatment plant (WWTP). Although this technology has been known for several years, the number of full-scale applications for it is limited. For a WWTP approaching its critical nitrogen load capacity, the benefits are doubled if the introduced side-stream treatment for digester supernatant is combined with bioaugmentation. Not only is the nitrogen load to the mainstream process decreased by 10-25%, but the mainstream process is also boosted with nitrifiers, increasing the nitrifying capacity. In this full-scale study, the increment of the nitrification rate is examined in the mainstream process at different temperatures and at different flow rates of returned activated sludge to the side-stream treatment. Our results show that the nitrification rate in the mainstream process was increased by 41% during the coldest period of the study, implying that the examined WWTP could treat considerably higher nitrogen loads if bioaugmentation were permanently installed.

The Influence of Physical Properties of Sod-Podzol Soil on its Ammonifying and Nitrifying Capacity

The research was conducted by the Chair of Agricultural Chemistry and Crop Farming of the Mari State University. The model experiment helped to study the influence of temperature, moisture, and density on nitrifying and ammonifying capacity of sod-podzol midclay low-humic soil. It was found out that change of physical properties factors of sod-podzol soil influenced nitrifying and ammonifying capacity and mineral nitrogen content. Maximum content of nitrate and mineral nitrogen and the biggest nitrifying capacity were at a soil temperature of +15°C and had the following corresponding values: 74.4, 81.3, and 31.9 mg/kg. Moistening conditions optimal for developing nitrifying and ammonifying bacteria were formed at a soil moisture of 20-25% (60-75% WFC). At this moisture there were the biggest figures of nitrifying capacity (31.5-35.0 mg/kg) and maximum values of content of nitrate nitrogen (74.0-77.5 mg/kg) and mineral nitrogen (78.7-82.3 mg/kg). Soil firming had a negative effect on the microflora of soil. With soil density increase from 1.1 to 2.0 g/cm3 nitrifying capacity decreased from 21.0 mg/kg down to 10.4 mg/kg, while nitrate nitrogen content in soil decreased from 63.5 to 32.1 mg/kg. The best conditions for nitrification and ammonification in sod-podzol soil were as follows: soil temperature of +15°C, soil moisture of 20-25%, and soil density of 1.1 g/cm3. Dependence of mineral nitrogen content in soil on its temperature and moisture was curvilinear and was described by a second-order regression equation, while dependence on its density was linear and was described by a first-order regression equation.

杏林湾水体的硝化作用及其影响因素研究

文章采用现场调查结合实验室模拟培养，研究了2011年8月和2012年2月杏林湾表层水体溶解无机氮的分布、硝化作用强度及其影响因素。结果表明，杏林湾水体溶解无机氮和硝化作用强度的空间差异和季节变化显著，湾区上游和下游的溶解无机氮的浓度和硝化速率均比中游高，夏季溶解无机氮的浓度和硝化速率比冬季高，说明溶解无机氮的浓度和温度是控制硝化作用空间变化和季节变化的主要因素。实验室培养的结果表明，温度、pH、氨的浓度和颗粒物对硝化菌的硝化作用均有重要的影响，其中温度和颗粒物对硝化作用强度影响最为显著。在20℃~30℃之间，温度升高10℃硝化速率提高2.9倍；水样经3 μm的滤膜过滤去除颗粒物后，硝化作用强度减弱为原水的1/5。pH对硝化作用有较大影响，当pH值为8.0时，硝化速率最大。当氨的浓度< 3.0 mg∙N∙L−1 (即214 μmol∙N∙L−1)时，提高氨浓度可有效促进硝化作用，但是较高的氨浓度、较高的温度反而会抑制硝化作用，反映了微生物对长期生境的适应性。根据实验结果估算，硝化作用可以把输入杏林湾水体的38%~52%的氨氮转化为硝氮，对区域氮循环具有重要意义。 The spatial distribution and seasonal variation of dissolved inorganic nitrogen, the performance of nitrification and its impact factors in Xinglin Bay were investigated based on field observation and laboratory simulation incubations in August 2011 (summer) and February 2012 (winter). The results showed that the inorganic nitrogen and nitrification rates had significant spatial and seasonal variation. The relative higher concentrations of inorganic nitrogen coupling with higher nitrification rates were observed at the upstream and downstream of the Bay as compared to the middle stream, suggesting that inorganic nitrogen was the major factor affecting the spatial distribution of nitrification. Seasonally, the concentrations of inorganic nitrogen and nitrification rates were higher in summer than that in winter, indicating that inorganic nitrogen concentrations and the water temperature were the major factors affecting the seasonal variation of nitrification in the Bay. The laboratory experiments showed that temperature, pH, ammonia concentration and particulate matter had important effects on nitrification. Especially, the temperature and particulate mater had significant effects on nitrifying capacity. The increase of 10˚C of temperature, the nitrification rate could be increased by 2.9 times within the temperature range 20˚C - 30˚C. The nitrification rate in the filtered water (through ~3 μm pore size filter) was only 1/5 of that in unfiltered water. At low concentration ( -N < 3 mg∙L−1), the increase of ammonia concentration could enhance the nitrification. However, higher temperature and ammonia concentration could inhibit the process of ni-trification. The optimum conditions for nitrification were pH 8.0, temperature 30˚C and ammonia concentration 3.0 mg∙N∙L−1, indicating that the microorganism adapted to the long-term habitat. It was estimated that around 38% - 52% of input ammonia was removed by nitrification in water column in the Bay, suggesting that nitrification was important on nitrogen cycle in Xinglin Bay.

ON IMPROVING SAFETY OF OPERATION OF ROCKET-SPACE SYSTEMS USING MEASURES OF REMEDIATION OF LANDS CONTAMINATED BY DIFFERENT TYPES OF FUELS

Using heavy space rockets Angara-A5 on Vostochny Spaceport with environmentally friendly components of rocket fuel (kerosene – liquid oxygen) would allow significantly reducing emissions and spills from the Space Rocket Machinery on the launch pads and to ensure environmental safety in the spaceport area. Treatment of contaminated soil using sodium selenate increases the microbial activity, mineralization rate, nitrifying and enzymatic capacity of mineralization of grey forest soil. This effects the conservation and restoration of the soil fertility.

Impacts of Edaphic Factors on Communities of Ammonia-Oxidizing Archaea, Ammonia-Oxidizing Bacteria and Nitrification in Tropical Soils

Nitrification is a key process in soil nitrogen (N) dynamics, but relatively little is known about it in tropical soils. In this study, we examined soils from Trinidad to determine the edaphic drivers affecting nitrification levels and community structure of ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA) in non-managed soils. The soils were naturally vegetated, ranged in texture from sands to clays and spanned pH 4 to 8. The AOA were detected by qPCR in all soils (ca. 105 to 106 copies archaeal amoA g−1 soil), but AOB levels were low and bacterial amoA was infrequently detected. AOA abundance showed a significant negative correlation (p<0.001) with levels of soil organic carbon, clay and ammonium, but was not correlated to pH. Structures of AOA and AOB communities, as determined by amoA terminal restriction fragment (TRF) analysis, differed significantly between soils (p<0.001). Variation in AOA TRF profiles was best explained by ammonium-N and either Kjeldahl N or total N (p<0.001) while variation in AOB TRF profiles was best explained by phosphorus, bulk density and iron (p<0.01). In clone libraries, phylotypes of archaeal amoA (predominantly Nitrososphaera) and bacterial amoA (predominanatly Nitrosospira) differed between soils, but variation was not correlated with pH. Nitrification potential was positively correlated with clay content and pH (p<0.001), but not to AOA or AOB abundance or community structure. Collectively, the study showed that AOA and AOB communities were affected by differing sets of edaphic factors, notably that soil N characteristics were significant for AOA, but not AOB, and that pH was not a major driver for either community. Thus, the effect of pH on nitrification appeared to mainly reflect impacts on AOA or AOB activity, rather than selection for AOA or AOB phylotypes differing in nitrifying capacity.

TWO VIGNA SPECIES NATIVE TO ARGENTINA WITH ORNAMENTAL POTENTIAL

Fil: Hoc, Patricia Susana. Universidad de Buenos Aires. Facultad de Cs.exactas y Naturales. Departamento de Biodiversidad y Biologia Experimental. Laboratorio del Grupo de Est.de Plantas Vasculares; Argentina. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Oficina de Coordinacion Administrativa Ciudad Universitaria. Instituto de Micologia y Botanica. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Micologia y Botanica; Argentina

Biological nutrients removal via nitrite from the supernatant of anaerobic co-digestion using a pilot-scale sequencing batch reactor operating under transient conditions

The short-cut nitrogen removal (SCNR) and denitrifying phosphorus removal via nitrite (DPRN) were studied using a pilot-scale sequencing batch reactor (SBR) for the treatment of the supernatant produced from the anaerobic co-digestion of waste activated sludge (WAS) and the organic fraction of municipal solid waste (OFMSW). The stability and behaviour of the biological via-nitrite processes were examined under transient conditions, imposed from the ordinary and extraordinary operation of the full-scale anaerobic digestion plant and the dewatering process of the anaerobic digestate. Nutrients removal was tested at low volumetric nitrogen loading rates (vNLR=0.2kgNm−3d−1), at the vNLR of the system’s nitrifying capacity (0.8kgNm−3d−1) and above its nitrifying capacity (1.1kgNm−3d−1). Complete absence of nitrite oxidizing bacteria (NOB) activity was accomplished, even when the free ammonia (FA) concentration in the reactor was very low (<0.45mgNH3–NL−1). The type of external carbon source critically impacted on the specific nitrite uptake rate (sNUR) and DPRN with fermentation liquid from OFMSW and from cattle manure and maize silage (CM&MS) to enhance these processes.

4年O3熏气对小麦根际土壤氮素微生物转化的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 四年O3熏气对小麦根际土壤氮素微生物转化的影响 DOI: 10.5846/stxb201301040015 作者: 作者单位: 南京信息工程大学环境科学与工程学院,南京信息工程大学环境科学与工程学院,南京信息工程大学环境科学与工程学院,南京信息工程大学环境科学与工程学院,南京信息工程大学环境科学与工程学院 作者简介: 通讯作者: 中图分类号: 基金项目: 教育部高等学校博士学科点专项科研基金资助项目（20123228110003）；国家自然科学基金资助项目（41075114） Induced changes in soil microbial transformation of nitrogen in maize rhizosphere by 4-year exposure to O3 Author: Affiliation: Nanjing University of Information Science Technology,Jiangsu Key Laboratory of Atmospheric environmental monitoring and Pollution control high-tech research,Nanjing University of Information Science Technology,Jiangsu Key Laboratory of Atmospheric environmental monitoring and Pollution control high-tech research,Nanjing University of Information Science Technology,Jiangsu Key Laboratory of Atmospheric environmental monitoring and Pollution control high-tech research,Nanjing University of Information Science Technology,Jiangsu Key Laboratory of Atmospheric environmental monitoring and Pollution control high-tech research,Nanjing University of Information Science Technology,Jiangsu Key Laboratory of Atmospheric environmental monitoring and Pollution control high-tech research Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:采用开顶箱（open top chambers，OTC） 法设置3个臭氧浓度梯度，连续4a对小麦生长季土壤进行臭氧增加试验。测定小麦拔节、孕穗、抽穗、灌浆和成熟期的根际土壤微生物量氮、氨氧化细菌、反硝化细菌数量以及硝化和反硝化强度。结果显示微生物量氮、氨氧化细菌数量和硝化强度随小麦生育进程的推进，呈先升高后降低的趋势，4a变化趋势相同。O3胁迫下，小麦根际微生物量氮、氨氧化细菌数量、硝化强度亦降低，与对照比较，均达显著水平（P < 0.05）；随O3作用年限增加，抑制效应越强，第4年 O3对其的抑制率显著高于第1年的抑制率。反硝化细菌数量在前期没有显著变化，成熟期则增加两个数量级，O3显著促进成熟期反硝化细菌数量增加。4a试验有相同的变化趋势。在较短时间里O3对土壤反硝化强度没有显著影响，而作用3个生长季后，反硝化强度显著升高。结果说明，O3浓度升高降低了麦田土壤微生物量氮、氨氧化细菌数量和硝化强度，并有一定的积累效应。O3剂量和作用时间的累积量达到一定阈值，显著增加土壤反硝化细菌数量和反硝化强度，增加麦田土壤N2O排放的风险。土壤氮素微生物转化受小麦生长发育状况和O3剂量、作用时间的共同影响，不同形态的氮素对O3的敏感阈值不同，响应的时间和变化的范围有差异。 Abstract:For determining changes in soil microbial transformation of nitrogen in a crop rhizosphere under ozone(O3)stress, using ozone treatments in OTCs (open top chambers), the effects of increase atmospheric surface level O3 contents on soil microbial transformation of nitrogen in winter wheat (Triticum aestivum)rhizosphere was investigated, during the growing/development (G/D) periods including reviving, jointing, booting, heading, filing and maturing stages. Four independent experiments were performed in four years, each for one year,using six OTCs. The chambers were equivalent, but two were fed with air while the other four with ozone at different concentration, in that two chambers with 100 nL/L and the other two with 150 nL/L. Winter wheat were grown to all life stage in OTCs. From reviving to mature stages, the plants were treated for 8 h (8:00-16:00) in every sunny day with different dose of O3, respectively. Soil microbial biomass N, amount of ammonium-oxidizing bacteria and denitrifying bacteria, soil nitrifying and denitrifying capacity were measured. Each treatment was assayed in triplicate. The data were initially compared by analysis of variance and differences between means were detected using the Duncans Multiple Range Tests. Values of P < 0.05 indicated significance. Quite similar results were obtained during the four years' experiments, suggesting that as a G/D stage is progressing, soil microbial biomass N, amount of ammonium-oxidizing bacteria and soil nitrifying capacity increased firstly but consequently declined. Under increased O3 stress, either soil microbial biomass N, or amount of ammonium-oxidizing bacteria or nitrifying capacity were found dropped. Their differences compare to control were significant (P < 0.05). With the increased of O3 dosage, the inhibition effects were found increasing. Inhibition rate of soil microbial biomass nitrogen, amount of ammonium-oxidizing bacteria and nitrifying capacity on wheat growth stages in the fourth years were significantly higher than those of the first year. The number of denitrifying bacteria was found to be no significant change in the earlier stages, but increased two orders of magnitude in the maturing stage. In maturity stage, the quantity of denitrifying bacteria was significantly improved by O3.Four years test showed the same change trend. No obvious influence of O3 on soil denitrifying capacity was found under short time ozone fumigation, but significantly increased during the later three growing seasons. Taking together,the elevated O3 concentration in atmospheric surface layer, impinges on the features of soil microbial transformation of nitrogen. O3 stresses can reduce soil microbial biomass N, amount of ammonium-oxidizing bacteria and nitrifying capacity. Enhance O3 irradiation and prolong fumigation time the Inhibition efficiency was up-regulated. When the cumulant of O3 dose and fumigation time reached a certain threshold, the number of denitrifying bacteria and denitrifying capacity rose up, meanwhile soil N2O emission risk was heighten. The effects on nitrogen microbial transformation were found to relate to (G/D) periods of winter wheat, dose of O3 and the exposure time. The different forms of nitrogen have different O3-sensitive, indicating that the threshold of subjected to O3, the responses time to O3 stress and the variation scope are different. 参考文献 相似文献 引证文献

Nitrogen removal and ammonia-oxidising bacteria in a vertical flow constructed wetland treating inorganic wastewater

Nitrogen removal performance and the ammonia-oxidising bacterial (AOB) community were assessed in the batch loaded 1.3 ha saturated surface vertical flow wetland at CSBP Ltd, a fertiliser and chemical manufacturer located in Kwinana, Western Australia. From September 2008 to October 2009 water quality was monitored and sediment samples collected for bacterial analyses. During the period of study the wetland received an average inflow of 1,109 m3/day with NH3-N = 40 mg/L and NO3-N = 23 mg/L. Effluent NH3-N and NO3-N were on average 31 and 25 mg/L, respectively. The overall NH3-N removal rate for the period was 1.2 g/m2/day indicating the nitrifying capacity of the wetland. The structure of the AOB community was analysed using group specific primers for the ammonia monooxygenase gene (amoA) by terminal restriction fragment length polymorphism and by clone libraries to identify key members. The majority of sequences obtained were most similar to Nitrosomonas sp. while Nitrosospira sp. was less frequent. Another two vertical flow wetlands, 0.8 ha each, were commissioned at CSBP in July 2009, since then the wetland in this study has received nitrified effluent from these two new cells.

Comparison of the operational characteristics between a nitrifying membrane bioreactor and a pre-denitrification membrane bioreactor process

A single submerged membrane bioreactor (MBR) for nitrification of ammonium and a pre-denitrification MBR process for total nitrogen (TN) removal were investigated in comparison. A single nitrifying MBR was fed with synthetic ammonium wastewater of up to 900 mgN/l without organics so that the MBR was maintained as a pure nitrifying system. A high nitrifying capacity around 1.8 kgNH 4-N/m 3/day was achieved while keeping the ammonium oxidation rate above 98%. Sludge volume index (SVI) gradually decreased down to less than 50 indicating good settleability of nitrifying sludge. The increase of suction pressure was less than 5 cm Hg over 7-months of operation. TN removal efficiency was determined in a pre-denitrification configuration with an anoxic reactor. Synthetic wastewater of 1200 mgCOD/l and 200 mgN/l was fed to the system at loads of 2.4 kgCOD/m 3/day and 0.4 kgN/m 3/day, respectively. As the internal recycle ratio from aerobic to anoxic zone increased from 2 to 6, TN removal efficiency was enhanced from 70 ± 9 to 89 ± 3%. With the sludge concentration of around 12,000 mg/l, SVI was highly fluctuated from 60 to 350 indicating the partial deterioration of sludge settleability. The suction pressure after 8 months of operation increased to above 10 cm Hg which is higher than that in a single nitrifying MBR. The concentration of extracellular polymeric substances (EPS), especially for carbohydrate content, was higher in the operation of a pre-denitrification MBR process than in a single nitrifying MBR. It is likely that the sludge characteristic such as settleability is related with membrane fouling but, further extensive study is needed. The performance of a pre-denitrification MBR process was also verified with real petrochemical nitrogen wastewater.

Exploring the relationship between viscous bulking and ammonia-oxidiser abundance in activated sludge: A comparison of conventional and IFAS systems

This study investigated the nature of viscous sludge bulking within a molasses-fed integrated fixed-film activated sludge (IFAS) and conventional activated sludge (AS) plant by routinely measuring the total carbohydrate and protein fractions of the mixed liquor (ML). The impacts of sludge settleability and plant performance on the relative abundance of ammonia-oxidising bacteria (AOB) ( Nitrosomonas oligotropha-cluster) were also investigated using quantitative polymerase chain reaction (qPCR). Results showed that sludge volume index (SVI) correlated positively with the amount of ML total carbohydrate in both the IFAS and traditional AS plants, highlighting the influential role that ML polysaccharide concentration plays on sludge settleability in these reactors. Results also revealed a negative relationship between the AOB/total Bacteria ratio and SVI, demonstrating that a poor settling sludge generally coincided with periods of relatively low AOB abundance. The existence of these relationships suggests that readily available organic carbon (molasses) was likely to have been present in excess in these systems. Our qPCR results also showed that concentrations of both AOB and total Bacteria genomic copies detected within the ML of the IFAS and conventional AS plants were remarkably similar. For the IFAS system, results showed that the ML supported an equivalent number of AOB (per gram of biomass) to that detected on the plastic IFAS media carriers, suggesting that the suspended biomass fraction plays an equally important role in the overall nitrification performance of these systems. Interestingly, large observed variations in AOB and AOB/total Bacteria ratio measured within both the ML and IFAS media carriers had no measurable impact on the apparent nitrification performance of these systems; indicating the presence of some excess or ‘reserve’ nitrifying capacity above that which is required for effective plant performance. Results presented here also constitute the first known side-by-side comparison of the distribution of AOB in IFAS and conventional racetrack-like AS plants at the full-scale level.

Variation in the relationship between nitrification and acidification of subtropical soils as affected by the addition of urea or ammonium sulfate

The effects on nitrification and acidification in three subtropical soils to which (NH 4) 2SO 4 or urea had been added at rate of 250 mg N kg −1 was studied using laboratory-based incubations. The results indicated that NH 4 + input did not stimulate nitrification in a red forest soil, nor was there any soil acidification. Unlike red forest soil, (NH 4) 2SO 4 enhanced nitrification of an upland soil, whilst urea was more effective in stimulating nitrification, and here the soil was slightly acidified. For another upland soil, NH 4 + input greatly enhanced nitrification and as a result, this soil was significantly acidified. We conclude that the effects of NH 4 + addition on nitrification and acidification in cultivated soils would be quite different from in forest soils. During the incubation, N isotope fractionation was closely related to the nitrifying capacity of the soils.

Application of high rate nitrifying trickling filters for potable water treatment

The interference of ammonia with chlorination is a prevalent problem encountered by water treatment plants located throughout South East Asia. The efficacy of high rate, plastic-packed trickling filters as a pre-treatment process to remove low concentrations of ammonia from polluted surface water was investigated. This paper presents the findings from a series of pilot experiments, which were designed to investigate the effect of specific conditions—namely low ammonia feed concentrations (0.5–5.0 mg NH 4-N L −1), variations in hydraulic surface load (72.5–145 m 3 m −2 d −1) and high suspended solid loads (51 ± 25 mg L −1)—on filter nitrifying capacity. The distribution of nitrification activity throughout a trickling filter bed was also characterised. Results confirmed that high hydraulic rate trickling filters were able to operate successfully, under ammonia-N concentrations some 10- to 50-fold lower and at hydraulic loading rates 30–100 times greater than those of conventional wastewater applications. Mass transport limitations posed by low ammonia-N concentrations on overall filter performance were insignificant, where apparent nitrification rates (0.4–1.6 g NH 4-N m −2 d −1), equivalent to that of wastewater filters were recorded. High inert suspended solid loadings had no adverse effect on nitrification. Results imply that implementation of high rate trickling filters at the front-end of a water treatment train would reduce the ammonia-related chlorine demand, thereby offering significant cost savings.

Effect of ecological factors on ammonifying and nitrifying capacity of sod-podzolic soil

The optimal conditions for nitrifying and ammonifying processes of sod-podzolic soil in the eastern part of the Non-Chernozem Zone are given: temperature 15°C, soil moisture content 20–25%, soil density 1.1 g/cm3, and neutral pH value.

The kinetics of crossflow dynamic membrane bioreactor

Crossflow dynamic membrane bioreactor (CDMBR) kinetics was investigated by treating caprolactam wastewater over a period of 180 d. The removal efficiencies of organic substances and nitrogen averaged over 99% and 80%, respectively. The observed sludge yield was only 0.14 g SS·g-1 COD·d-1 at an SRT of 30 d and sludge organic loading about 0.3 g COD·g-1 SS·d-1. Based on total organic carbon TOC measurement, accumulation of soluble microbial products (SMP) in the supernatant caused by membrane separation was observed during the initial operational period. SMP in the supernatant was verified biodegradable subsequently through molecular weight distribution (MWD) analysis. Specific oxygen uptake rate (sOUR) decreased with MLSS increasing in the reactor, which could be expressed by a exponential function. sOUR maintained in the range of 4-5 mg O2·h-1·g -1 VSS while oxygen uptake rate (OUR) increased with MLSS concentration. Despite the low sOUR level of Nitrosomo and Nitrobacter, nitrifying capacity of CDMBR remained high enough to qualify nitrogen removal. Water SA Vol.32 (2) 2006: pp.199-204

An innovative biofilm-suspended biomass hybrid membrane bioreactor for wastewater treatment

An innovative membrane-assisted hybrid bioreactor for wastewater treatment was developed in our laboratory. This system was composed by a hybrid circulating bed reactor coupled in series to an ultrafiltration membrane module. Biomass was maintained growing both in suspension and in biofilms onto small rough plastic particles. The growth of nitrifiers in the hybrid system was promoted into biofilms while heterotrophs were in suspension. This made it feasible to operate the unit at higher SRT for nitrifiers than for heterotrophs, which resulted in the presence of a higher fraction of nitrifiers in the reactor. The hybrid bioreactor was used to treat two industrial wastewaters—from a tannery and a fish-canning factory—with high nitrogen and organic matter content. COD removals of around 99% were obtained at an organic loading rate (OLR) of 6.5 kg COD/m 3·d and an NLR of 1.8 kg N-NH + 4/m 3·d during the treatment of the fish canning wastewater. Between 50–60% of the nitrifying capacity of the reactor was located in the biofilm. During the treatment of the tannery wastewater, OLR and ALR were stepwise increased up to 4.5 kg COD/m 3·d and 1.2 kg N-NH + 4/m 3·d, respectively. COD removal efficiency was 95%, while up to 97% of ammonia removal was obtained, the concentration of ammonia in the effluent being low, 10 mg N-NH + 4/L. For both industrial wastewaters, the biofilm nitrifying activity was not affected by the variations in the organic loading rates, COD concentration in the influent or characteristics of the influent. Most of the dissolved COD was consumed by suspended biomass in the reactor, avoiding the competition between nitrifiers and heterothophs in the biofilm. Moreover, the membrane filtration unit made it feasible to operate the reactor at high OLR without problems related to either the settling properties of the sludge or the drop in the nitrogen conversion, which usually occurs in other hybrid biological reactors operated at high OLR or NLR.