High levels of nitrifying bacteria in intermittently aerated reactors treating high ammonia wastewater (original) (raw)
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Water Research, 2008
We wished to discover if we could gain greater insights into how biological treatment plants function by contrasting the presence and activity of the most abundant Bacteria in plug flow and completely mixed activated sludge plants. Presence was assessed by amplifying 16S rRNA gene fragments (using PCR) and activity by amplifying native 16S rRNA, using reverse-transcriptase PCR (RT-PCR), using Bacteria-specific primers. The amplified sequences were compared using denaturing gradient gel electrophoresis (DGGE). The plug flow plant exhibited a strong physico-chemical gradient with an initial anoxic zone, whilst the two completely mixed reactors did not. Similarities were observed between the profile of the banding pattern for presence and activity. However, in the plug flow reactor one prominent band was detected in the active population (16S rRNA) but was absent from the corresponding profile of the 16S rRNA gene. Sequencing of this band revealed its identity as a Nitrosomonas-like sequence. The intensity of the 16S rRNA sequenced varied along the physico-chemical gradient of the plug-flow reactor in a manner that coincided with the growth of ammonia-oxidising bacteria (AOB) and the loss of ammonia. This band was also absent from the completely mixed reactors, although significant numbers of AOB were detected in all systems ($10 6-10 8 cells ml À1) by fluorescence in situ hybridisation (FISH). An abundant and highly active AOB population was present in the anoxic zone of the plug-flow reactor where up to 60% of the total ammonia was removed. An examination of nitrogen removal/production rates, together with the above data, reveal that complex nitrogen removal processes occur in this system. These data also enabled the calculation of a specific in situ growth rate for the AOB as 0.12 h À1 .
Applied microbiology and biotechnology, 2017
We investigated the effects of free ammonia (FA) and free nitrous acid (FNA) concentrations on the predominant ammonia-oxidizing bacteria (AOB) and the emission of nitrous oxide (N2O) in a lab-scale sequencing batch reactor for partial nitrification. The reactor was operated with stepwise increases in the NH4(+) loading rate, which resulted in a maximum FA concentration of 29.3 mg-N/L at pH 8.3. Afterwards, FNA was increased by a gradual decrease of pH, reaching its maximum concentration of 4.1 mg-N/L at pH 6.3. Fluorescence in situ hybridization indicated that AOB remained predominant during the operation, achieving specific nitrification rates of 1.04 and 0.99 g-N/g-VSS/day at the highest accumulations of FA and FNA, respectively. These rates were in conjunction with partial nitrification efficiencies of >84%. The N2O emission factor of oxidized NH4(+) was 0.90% at pH 7.0, which was higher than those at pH 8.3 (0.11%) and 6.3 (0.12%), the pHs with the maximum FA and FNA concent...
Environmental Science and Pollution Research, 2014
Cell-specific ammonia oxidation rate (AOR) has been suggested to be an indicator of the performance of nitrification reactors and to be used as an operational parameter previously. However, published AOR values change by orders of magnitude and studies investigating full-scale nitrification reactors are limited. Therefore, this study aimed at quantifying ammonia oxidizing bacteria (AOB) and estimating their in situ cell-specific ammonia oxidation rates (AOR) in a full-scale activated sludge reactor treating combined 2 domestic and industrial wastewaters. Results showed that cell-specific AOR changed between 5.30 and 9.89 fmole/cell/hour although no significant variation in AOB cell numbers were obtained (1.54E+08 0.22 cell/ml). However, ammonia removal efficiency varied largely (52-79%) and was proportional to the cell-specific AOR in the reactor. This suggested that the cell-specific AOR might be the factor affecting the biological ammonia removal efficiency of nitrification reactors independent of the AOB number. Further investigation is needed to establish an empirical relationship to use cellspecific AOR as a parameter to operate full-scale nitrification systems more effectively.
Water science and technology : a journal of the International Association on Water Pollution Research, 2003
Nitrification was assessed in two full-scale wastewater treatment plants (WWTPs) over time using molecular methods. Both WWTPs employed a complete-mix suspended growth, aerobic activated sludge process (with biomass recycle) for combined carbon and nitrogen treatment. However, one facility treated primarily municipal wastewater while the other only industrial wastewater. Real time PCR assays were developed to determine copy numbers for total 16S rDNA (a measure of biomass content), the amoA gene (a measure of ammonia-oxidizers), and the Nitrospira 16S rDNA gene (a measure of nitrite-oxidizers) in mixed liquor samples. In both the municipal and industrial WWTP samples, total 16S rDNA values were approximately 2-9 x 10(13) copies/L and Nitrospira 16S rDNA values were 2-4 x 10(10) copies/L. amoA gene concentrations averaged 1.73 x 10(9) copies/L (municipal) and 1.06 x 10(10) copies/L (industrial), however, assays for two distinct ammonia oxidizing bacteria were required.
Environmental Science & Technology, 2011
The increasing regulatory demands to achieve greater nutrient removal from wastewater treatment plant effluents, while minimizing infrastructure investments and operating costs, has resulted in the development of several innovative biological nitrogen removal (BNR) processes. Partial nitrification based processes such as the single reactor system for high ammonium removal over nitrite (SHARON 1 ) and its variants are attractive for treating high-strength nitrogen waste streams such as anaerobic digestion reject water or centrate, owing to their reduced consumption of energy (for aeration) and organic carbon (for denitrification). Indeed, separate treatment of centrate via partial nitrification is one of the options for limiting nitrogen discharges to Jamaica Bay in New York City 2 and is part of PlaNYC, a sustainability plan for New York City targeted for 2030.
Water Research, 2015
Ammonia-oxidizing microbial communities involved in ammonia oxidation under low dissolved oxygen (DO) conditions (<0.3 mg/L) were investigated using chemostat reactors. One lab-scale reactor (NS_LowDO) was seeded with sludge from a full-scale wastewater treatment plant (WWTP) not adapted to low-DO nitrification, while a second reactor (JP_LowDO) was seeded with sludge from a full-scale WWTP already achieving low-DO nitrifiaction. The experimental evidence from quantitative PCR, rDNA tag pyrosequencing, and fluorescence in situ hybridization (FISH) suggested that ammonia-oxidizing bacteria (AOB) in the Nitrosomonas genus were responsible for low-DO nitrification in the NS_LowDO reactor, whereas in the JP_LowDO reactor nitrification was not associated with any known ammonia-oxidizing prokaryote. Neither reactor had a significant population of ammonia-oxidizing archaea (AOA) or anaerobic ammonium oxidation (anammox) organisms. Organisms isolated from JP_LowDO were capable of autotrophic and heterotrophic ammonia utilization, albeit without stoichiometric accumulation of nitrite or nitrate. Based on the experimental evidence we propose that Pseudomonas, Xanthomonadaceae, Rhodococcus, and Sphingomonas are involved in nitrification under low-DO conditions.
Nitrite Accumulation at Low Ammonia Concentrations in Wastewater Treatment Plants
Sustainability
At higher ammonium concentrations, nitritation can be easily attained by picking out the inhibitor. In low-concentrated reactors, nitrite accumulation without using any chemical inhibitor is a challenging process. In this study, two continuous stirred-tank reactors (CSTR) with biofilm and without biofilm were operated with total ammonium nitrogen feed concentrations of ~50 mg/L and ~30 mg/L and effluent concentrations of ~1 mg/L. A CSTR without biofilm was operated in three phases. In phase 1, a substrate-shock concentration of 1 to 2000 mg total ammonium nitrogen (TAN)/L was tested. It was found that the shock concentration was not successful in long-term operations because nitrite-oxidizing bacteria (NOB) recovered rapidly. In phases 2 and 3, the sludge-treatment method was applied, and a high nitrite accumulation efficiency was achieved (~98%). In a CSTR with biofilm, the free ammonia shock concentration was ~91.7 mg/L, and a nitrite accumulation efficiency of ~90% was achieved.
The dominant nitrifying bacterial communities and nitrification performance of two biological nutrient removal plants were evaluated. Fluorescent in situ hybridization was used to detect and quantify the dominant nitrifying bacteria and polymerase chain reaction; cloning and sequence analysis of 16S rRNA genes was done for phylogenetic analysis. Fluorescent in situ hybridization-confocal scanning laser microscopy studies revealed the presence and dominance of Nitrosomonas-related ammonia-oxidizing bacteria (AOB) and Nitrobacter-related nitrite-oxidizing bacteria (NOB); however, a significant variation in AOB/NOB ratios was recorded. The plant with an overall higher AOB/NOB ratio (!1.0) and dissolved oxygen concentration (1.8 to 2.5 mg/L) showed a higher nitrification rate. This study has also shown the co-existence and variation in phylogenetically diverse Nitrosomonas-related AOB and Nitrobacter-related NOB at these two plants. These dissimilar, distinct distribution patterns of nitrifying communities could be attributed to wastewater characteristics and the process configuration, which, in turn, would have also affected the nitrification performance of the systems. Water Environ. Res., 85, 374 (2013).
Applied and Environmental Microbiology, 2001
Uncultivated Nitrospira-like bacteria in different biofilm and activated-sludge samples were investigated by cultivation-independent molecular approaches. Initially, the phylogenetic affiliation of Nitrospira-like bacteria in a nitrifying biofilm was determined by 16S rRNA gene sequence analysis. Subsequently, a phylogenetic consensus tree of the Nitrospira phylum including all publicly available sequences was constructed. This analysis revealed that the genus Nitrospira consists of at least four distinct sublineages. Based on these data, two 16S rRNA-directed oligonucleotide probes specific for the phylum and genus Nitrospira, respectively, were developed and evaluated for suitability for fluorescence in situ hybridization (FISH). The probes were used to investigate the in situ architecture of cell aggregates of Nitrospira-like nitrite oxidizers in wastewater treatment plants by FISH, confocal laser scanning microscopy, and computer-aided three-dimensional visualization. Cavities and a network of cell-free channels inside the Nitrospira microcolonies were detected that were water permeable, as demonstrated by fluorescein staining. The uptake of different carbon sources by Nitrospira-like bacteria within their natural habitat under different incubation conditions was studied by combined FISH and microautoradiography. Under aerobic conditions, the Nitrospira-like bacteria in bioreactor samples took up inorganic carbon (as HCO 3 ؊ or as CO 2 ) and pyruvate but not acetate, butyrate, and propionate, suggesting that these bacteria can grow mixotrophically in the presence of pyruvate. In contrast, no uptake by the Nitrospira-like bacteria of any of the carbon sources tested was observed under anoxic or anaerobic conditions.
Community Analysis of Ammonia and Nitrite Oxidizers during Start-Up of Nitritation Reactors
Applied and Environmental Microbiology, 2003
Partial nitrification of ammonium to nitrite under oxic conditions (nitritation) is a critical process for the effective use of alternative nitrogen removal technologies from wastewater. Here we investigated the conditions which promote establishment of a suitable microbial community for performing nitritation when starting from regular sewage sludge. Reactors were operated in duplicate under different conditions (pH, temperature, and dilution rate) and were fed with 50 mM ammonium either as synthetic medium or as sludge digester supernatant. In all cases, stable nitritation could be achieved within 10 to 20 days after inoculation. Quantitative in situ hybridization analysis with group-specific fluorescent rRNA-targeted oligonucleotides (FISH) in the different reactors showed that nitrite-oxidizing bacteria of the genus Nitrospira were only active directly after inoculation with sewage sludge (up to 4 days and detectable up to 10 days). As demonstrated by quantitative FISH and restr...