Bioprocess of nitrite accumulation in water - a review / 生物工程学报

Nitrite is a by-product of the nitrogen cycle. The excessive nitrite not only constrains growth and metabolism of bacteria, but also impairs health of humans and aquatic organisms. On the other hand, the continuous maintaining of nitrite accumulation could achieve the shortcut nitrification process, and reduce energy consumption of biological nitrogen removal to save cost. This article reviews the biological processes and causes of nitrite accumulation in the water environment, and summarizes the factors that affect the accumulation of nitrite, to provide reference for wastewater treatments, including improving the nitrogen removal efficiency, reducing operating costs, decreasing discharge of sewage and nitrite nitrogen in natural water.

Correlación entre los microorganismos oxidantes del amonio y los factores ambientales durante el compostaje de estiércol de ganado / Correlation between ammonia-oxidizing microorganisms and environmental factors during cattle manure composting

Abstract Cattle manure composting was performed in an aerated vessel. Community structure and diversity of ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA) were investigated using polymerase chain reaction and denaturing gradient gel electrophoresis (PCR-DGGE) techniques targeting the ammonia monooxygenase alpha subunit (amoA) gene and the correlation between AOB and AOA communities and environmental factors was explored. Thirteen (13) AOB sequences were obtained, which were closely related to Nitrosomonas spp., Nitrosomonas eutropha, and Nitrosospira spp. and uncultured bacteria, among which Nitrosomonas spp. were predominant. Excessively high temperature and high ammonium concentration were not favorable for AOB growth. Five AOA sequences, belonging to Candidatus Nitrososphaera gargensis and to an uncultured archaeon, were obtained. During composting, community diversity of AOB and AOA fluctuated, with AOA showing a higher Shannon-Wiener index. The AOB community changed more dramatically in the mesophilic stage and the early thermophilic stage, whereas the most obvious AOA community succession occurred in the late thermophilic stage, the cooling stage and the maturity stage. Water content, total nitrogen (TN) and ammonium concentration were more relevant to the AOB community structure, while higher correlations were observed between ammonia, nitrate and TN and the AOA community. AOB community diversity was negatively correlated with pH (r = -0.938, p < 0.01) and water content (r = -0.765, p < 0.05), while positively correlated with TN (r = 0.894, p < 0.01). AOA community diversity was negatively correlated with ammonium concentration (r = -0.901, p < 0.01). Ammonium concentration played an important role in the succession of AOB and AOA communities during composting.

Resumen Se llevó a cabo un compostaje de estiércol de ganado en un recipiente aireado. Se investigó la estructura de la comunidad y la diversidad de bacterias oxidantes del amoníaco (AOB) y las arqueas oxidantes del amoníaco (AOA) mediante el uso de las técnicas de reacción en cadena de la polimerasa y la electroforesis en gel con gradiente de desnaturalización (PCR-DGGE) dirigidas al gen de la subunidad alfa de la amonio monooxigenasa (amoA), y se exploró la correlación entre las comunidades AOB, AOA y los factores ambientales. Se obtuvieron 13 secuencias de AOB, las cuales se relacionaron estrechamente con Nitrosomonas spp., Nitrosomonas eutropha y Nitrosospira spp., y bacterias no cultivadas, entre las cuales fueron predominantes las Nitrosomonas spp. La temperatura excesivamente alta y la concentración de amonio elevada no fueron favorables para el crecimiento de las AOB. Se obtuvieron 5 secuencias de AOA, pertenecientes a Candidatus Nitrososphaera gargensis y un Archaeon no cultivado. Durante el compostaje, la diversidad de AOB y AOA fluctuó y las AOA mostraron un índice de Shannon-Wiener más alto. La comunidad de AOB cambió significativamente en la etapa mesofílica y la etapa termofílica temprana, mientras que la sucesión más obvia de la comunidad AOA ocurrió en la etapa termofílica tardía y las etapas de enfriamiento y de maduración. El contenido de agua, el nitrógeno total (TN) y la concentración de amonio fueron más relevantes para la estructura de la comunidad AOB, mientras que se observaron correlaciones mayores entre amoníaco, nitrato y TN, y la comunidad AOA. La diversidad de la comunidad AOB se correlacionó negativamente con el pH (r= -0,938; p < 0,01) y el contenido de agua (r = -0,765; p < 0,05), mientras que se relacionó positivamente con TN (r = 0,894; p < 0,01). La diversidad de la comunidad AOA se correlacionó negativamente con la concentración de amonio (r = -0,901; p < 0,01). La concentración de amonio desempenó un papel importante en la sucesión de las comunidades AOB y AOA durante el compostaje.

Comparação de métodos para quantificação de bactérias nitrificantes / Comparison of methods for quantification of nitrifying bacteria

RESUMO A quantificação de bactérias nitrificantes é de extrema importância para o monitoramento de sistemas biológicos de tratamento que promovam a nitrificação. Neste trabalho, 15 amostras de efluentes coletadas em sistema de tratamento por lodos ativados (LA) foram analisadas de modo a quantificar bactérias nitrificantes por meio de duas técnicas: tubos múltiplos ou técnica do número mais provável (NMP); e hibridação in situ fluorescente (FISH). Os resultados sugerem que houve uma tendência de se obter valores diferentes para bactérias oxidadoras de amônia por meio da NMP em comparação com a FISH. Não obstante, a análise estatística revelou que a diferença de quantificação encontrada entre as técnicas não foi significativa, indicando que ambas podem ser usadas. Para as oxidadoras de nitrito, não foi possível realizar comparação, uma vez que os gêneros que estavam sendo determinados em cada uma das técnicas provavelmente eram diferentes. Sendo assim, as técnicas NMP e FISH se mostraram métodos relativamente simples e adequados para quantificação de microrganismos nitrificantes, com vantagens e limitações inerentes a cada uma.

ABSTRACT The quantification of nitrifying bacteria is of utmost importance for monitoring biological treatment systems designed to promote nitrification. In this study, 15 activated sludge samples were analyzed in order to quantify nitrifying bacteria by two different methods: the most-probable number (MPN); and the fluorescence in situ hybridization (FISH). The results suggest that there was a tendency to obtain different values for ammonia-oxidizing bacteria by MPN compared to FISH. However, statistical analysis of these data revealed that the difference found between the two techniques was not significant, indicating that both can be used for quantification of ammonia-oxidizing bacteria. For nitrite-oxidizing bacteria it was not possible to make this comparison, since the bacterial genera that were being determined in each technique were likely different. Thus, MPN and FISH techniques proved to be relatively simple and suitable for quantification of nitrifying microorganisms in sludge samples, each of them with advantages and limitations.

Immobilization of ammonia-oxidizing bacteria by polyvinyl alcohol and sodium alginate

Abstract Ammonia-oxidizing bacteria were immobilized by polyvinyl alcohol (PVA) and sodium alginate. The immobilization conditions and ammonia oxidation ability of the immobilized bacteria were investigated. The following immobilization conditions were observed to be optimal: PVA, 12%; sodium alginate, 1.1%; calcium chloride, 1.0%; inoculum concentration, 1.3 immobilized balls/mL of immobilized medium; pH, 10; and temperature, 30 °C. The immobilized ammonia-oxidizing bacteria exhibited strong ammonia oxidation ability even after being recycled four times. The ammonia nitrogen removal rate of the immobilized ammonia-oxidizing bacteria reached 90.30% under the optimal immobilization conditions. When compared with ammonia-oxidizing bacteria immobilized by sodium alginate alone, the bacteria immobilized by PVA and sodium alginate were superior with respect to pH resistance, the number of reuses, material cost, heat resistance, and ammonia oxidation ability.

The abundance and diversity of ammonia-oxidizing bacteria in activated sludge under autotrophic domestication.

Ammonia-oxidizing bacteria (AOB) play a key role in nitrogen-removal wastewater treatment plants (WWTPs) as they can transform ammonia into nitrite. AOB can be enriched in activated sludge through autotrophic domestication although they are difficult to be isolated. In this study, autotrophic domestication was carried out in a lab-scale sequencing-batch-reactor (SBR) system with two activated sludge samples. The ammonia removal capacity of the sludge samples increased during the domestication, and pH exhibited a negative correlation with the ammonia removal amount, which indicated that it was one important factor of microbial ammonia oxidation. The count of AOB, measured by the most probable number (MPN) method, increased significantly during autotrophic domestication as ammonia oxidation efficiency was enhanced. We investigated the changes in the community structure of AOB before and after domestication by amoA clone library and T-RFLP profile. It showed that AOB had been successfully enriched and the community structure significantly shifted during the domestication. Two groups of AOB were found in sludge samples: Nitrosomonas-like group remained predominant all the time and Nitrosospira-like group changed obviously. Simultaneously, the total heterotrophic bacteria were investigated by MPN and Biolog assay. The metabolic diversity of heterotrophs had changed minutely, although the count of them decreased significantly and lost superiority of microbial communities in the sludge.

Seasonal variations in abundance of nitrifying bacteria in fish pond ecosystem.

Seasonal changes in abundance of nitrifiers (ammonia-oxidizing and nitrite-oxidizing bacteria) in surface and bottom water of freshwater ponds were examined with respect to temperature, DO, pH as well as concentration of ammonia and nitrite. The most probable number (MPN) of ammonia-oxidizers in different ponds varied from 1297±3.6 to 1673.23±0.36 ml-l in bottom and 720.5±8.1 to 955.3±10.8 ml-l in surface water during the rainy season while the MPN ranged from 1074±1.07 to 1372.17±4.6 ml-l in bottom and 515±10.1 to 678±11.8 ml-l in surface water in winter. However, the MPN were greatly reduced in summer and ranged from 435.05±15.7 to 547.54±2.12 ml-l in bottom and 218.7±7.3 to 368.4±9.32 ml-l in surface water. Similar seasonal trends were also observed in MPN of nitrite-oxidizers. Among all the physico-chemical parameters, abundance of nitrifiers was more positively correlated with ammonia and nitrite concentration in all the seasons. The abundance of nitrifiers in surface and bottom water was highest in rainy season followed by winter and modest in summer. The potential nitrification activities and oxidation rates were shown to be linear and activity of ammonia-oxidizing and nitriteoxidizing bacteria was highest during rainy season.

Abundance and diversity of ammonia-oxidizing bacteria in relation to ammonium in a Chinese shallow eutrophic urban lake

The measures of most-probable-number and restriction fragment length polymorphism analysis were used to analyze the abundance and diversity of ammonia-oxidizing bacteria in sediment of a Chinese shallow eutrophic urban lake (Lake Yuehu). Among the 5 sampling sites, ammonia concentration in interstitial water was positively proportional not only to the content of organic matter, but also to ammonia-oxidizing bacteria numbers (at a magnitude of 10(5) cells g-1 dry weight) in sediment significantly. Furthermore, the diversity of ammonia-oxidizing bacteria were determined by means of PCR primers targeting the amoA gene with five gene libraries created and restriction pattern analysis. The 13 restriction patterns were recorded with 4 ones being common among all sampling sites. The 8 restriction patterns including 4 unique ones were found at the site with the highest NH4+ concentrations in interstitial water, while, there were only common patterns without unique ones at the site with the lowest NH4+ concentrations in interstitial water. Phylogenetic analysis showed that the amoA fragments retrieved belong to Nitrosomonas oligotropha & ureae lineage, N. europaea lineage, N. communis lineage and Nitrosospira lineage, most of which were affiliated with the genus Nitrosomonas. The N. oligotropha & ureae-like bacteria were the dominant species. Thus, the abundance and diversity of sediment AOB is closely linked to ammonium status in eutrophic lakes.

Effect of Different Media on MPN Estimation of Ammonia-oxidizing Bacteria in Lakes / 微生物学通报

The MPN method was used to enumerate ammonia-oxidizing bacteria (AOB) in water and sediments of several shallow lakes. The suitable incubation time, medium types and substrate (ammonium sulphate) concentrations were studied. The results showed that, MPN values increased with the incubation time, reaching a stable maximum at some time stages, which was 40 days in all the samples for MSF medium. Among the three media used (XZ-AOB、MSF、SW), MSF give the highest MPN value. In addition, am- monium sulphate concentration in medium was an important factor affecting MPN estimation of AOB. Compared to AOB in lake sediments, AOB in lake water was more sensitive to ammonium sulphate concentration.

Analysis of Microbial Flora in Full Autotrophic Ammonium Removal System / 微生物学通报

The microbial flora of fungi,bacterial and actinomycetes in full autotrophic ammonium removal reactor and activated sludge was analyzed,and the amount of nitrite-oxidizing bacteria and ammonia-oxidizing bacteria was also compared.The result showed that the population,species,species number and dominates of microorganisms in full autotrophic ammonium removal reactor were different from that in activated sludge.In full autotrophic ammonium removal reactor,the amount of ammonia-oxidizing bacteria was increased remarkably which indicated that the accumulation of ammonia-oxidizing bacteria was a remarkable feature of full autotrophic ammonium removal system.