High nitrification rate at low pH in a fluidized bed reactor with chalk as the biofilm carrier

Tarre, Sheldon; Beliavski, Michael; Denekamp, N.; Gieseke, Armin; Beer, Dirk de; Green, M.

doi:10.2166/wst.2004.0814

Cited by 21 publications

(21 citation statements)

References 14 publications

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“…Previous microelectrode measurements profiling pH and oxygen concentrations in a nitrifying biofilm grown at low pH revealed an active biofilm with a pH similar to the bulk pH and even lower (36). Furthermore, modeling nitrifying biofilm based on known kinetic parameters and diffusion constants supported the microsensor's measurements (35).…”

Section: Resultsmentioning

confidence: 66%

“…Summarizing, a proton-producing biofilm cannot possibly have a favorable pH microenvironment, with the corresponding increase in NH 3 concentration strongly suggesting that autotrophic nitrifying bacteria have an efficient uptake mechanism for the ammonium cation. The phenomenon of highrate nitrification at low pH was repeated in several other biofilm reactors with inocula from different sources (36), and pH values as low as 3.75 were observed (results not shown).…”

Section: Resultsmentioning

confidence: 96%

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High-Rate Nitrification at Low pH in Suspended- and Attached-Biomass Reactors

Tarre

Green

2004

Appl Environ Microbiol

100

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This article reports on high-rate nitrification at low pH in biofilm and suspended-biomass reactors by known chemolithotrophic bacteria. In the biofilm reactor, at low pH (4.3 ؎ 0.1) and low bulk ammonium concentrations (9.3 ؎ 3.3 mg ⅐ liter ؊1 ), a very high nitrification rate of 5.6 g of N oxidized ⅐ liter ؊1 ⅐ day ؊1 was achieved. The specific nitrification rate (0.55 g of N ⅐ g of biomass ؊1 ⅐ day ؊1 ) was similar to values reported for nitrifying reactors at optimal pH. In the suspended-biomass reactor, the average pH was significantly lower than that in the biofilm reactor (pH 3.8 ؎ 0.3), and values as low as pH 3.2 were found. In addition, measurements in the suspended-biomass reactor, using isotope-labeled ammonium ( 15 N), showed that in spite of the very low pH, biomass growth occurred with a yield of 0.1 g of biomass ⅐ g of N oxidized ؊1 . Fluorescence in situ hybridization using existing rRNA-targeted oligonucleotide probes showed that the nitrifying bacteria were from the monophyletic genus Nitrosomonas, suggesting that autotrophic nitrification at low pH is more widespread than previously thought. The results presented in this paper clearly show that autotrophic nitrifying bacteria have the ability to nitrify at a high rate at low pH and in the presence of only a negligible free ammonia concentration, suggesting the presence of an efficient ammonium uptake system and the means to cope with low pH.

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Section: Resultsmentioning

confidence: 66%

Section: Resultsmentioning

confidence: 96%

High-Rate Nitrification at Low pH in Suspended- and Attached-Biomass Reactors

Tarre

Green

2004

Appl Environ Microbiol

100

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“…A smaller version of a two-column fluidized-bed reactor system with chalk particles as a carrier material was operated as described earlier (59). The total volume of the system was 2 liters (column inside diameter, 34 mm), and the fluidized bed consisted of 800 g of chalk taken from a larger reactor with a similar operation (59).…”

Section: Experimental Reactormentioning

confidence: 99%

“…The total volume of the system was 2 liters (column inside diameter, 34 mm), and the fluidized bed consisted of 800 g of chalk taken from a larger reactor with a similar operation (59). Oxygen and pH levels in the reactor medium were measured daily with conventional electrochemical sensors (Oxi 92; WTW, Weilheim, Germany, and MA130; Mettler-Toledo AG, Schwerzenbach, Switzerland).…”

Section: Experimental Reactormentioning

confidence: 99%

“…In this study, we applied these tools to investigate the microenvironment, local activity, and community structure of a highly active nitrifying biofilm grown under acidic conditions on chalk particles (24,59). The following two hypotheses were addressed: the chalk surface, by concomitant dissolution, provides a microenvironment with a locally elevated pH conducive to nitrification, and the conditions in the system select for the presence of (unknown) acid-tolerant strains of nitrifying bacteria.…”

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confidence: 99%

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Nitrification in a Biofilm at Low pH Values: Role of In Situ Microenvironments and Acid Tolerance

Gieseke

Tarre

Green

et al. 2006

Appl Environ Microbiol

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The sensitivity of nitrifying bacteria to acidic conditions is a well-known phenomenon and generally attributed to the lack and/or toxicity of substrates (NH 3 and HNO 2 ) with decreasing pHs. In contrast, we observed strong nitrification at a pH around 4 in biofilms grown on chalk particles and investigated the following hypotheses: the presence of less acidic microenvironments and/or the existence of acid-tolerant nitrifiers. Microelectrode measurements (in situ and under various experimental conditions) showed no evidence of a neutral microenvironment, either within the highly active biofilm colonizing the chalk surface or within a control biofilm grown on a nonbuffering (i.e., sintered glass) surface under acidic pH. A 16S rRNA approach (clone libraries and fluorescence in situ hybridizations) did not reveal uncommon nitrifying (potentially acid-tolerant) strains. Instead, we found a strongly acidic microenvironment, evidence for a clear adaptation to the low pH in situ, and the presence of nitrifying populations related to subgroups with low K m s for ammonia (Nitrosopira spp., Nitrosomonas oligotropha, and Nitrospira spp.). Acid-consuming (chalk dissolution) and acid-producing (ammonia oxidation) processes are equilibrated on a low-pH steady state that is controlled by mass transfer limitation through the biofilm. Strong affinity to ammonia and possibly the expression of additional functions, e.g., ammonium transporters, are adaptations that allow nitrifiers to cope with acidic conditions in biofilms and other habitats.Chemolithoautotrophic nitrifying bacteria, i.e., ammoniaoxidizing bacteria (AOB), catalyzing the first oxidation step of ammonia to nitrite and nitrite-oxidizing bacteria (NOB) completing the oxidation of the intermediate nitrite to nitrate are known to be sensitive to low pHs. Optimum growth occurs under neutral to moderately alkaline conditions (pH 7.5 to 8.0). In liquid pure culture, growth is usually restricted to a lower pH of 5.8 (AOB) or 6.5 (NOB) (62) and activity ceases typically below pH 5.5 (28, 31). The failure of AOB to cope with acidic conditions is thought to be primarily based on the unavailability of a substrate: with decreasing pHs, ammonia, the substrate of AOB (58), is increasingly protonated. Nitrite, the substrate of NOB, undergoes protonation to nitric acid, which disproportionates to nitrate and gaseous nitric oxide at low pHs (6). Furthermore, when present at elevated concentrations under low pHs, free nitric acid negatively affects the growth and activity of nitrifying bacteria (4).Despite these limitations, autotrophic nitrifying bacteria have been isolated from, or nitrifying activity has been demonstrated in, acidic environments, such as soils, activated sludge, and biofilms. Numerous nitrifying isolates have been obtained from soils with pHs around 4 (for a review, see reference 18 and references therein) to even as low as 2.5 (45). However, the majority of such isolates do not show nitrifying activity in acidic mineral medium (18). In contrast, autotrophic nitr...

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Treatment of halogenated organic compounds and monitoring of microbial dynamics in up‐flow fixed bed reactors under sequentially alternating pollutant scenarios

Emanuelsson¹,

Osuna²,

Sipma³

et al. 2008

Biotech & Bioengineering

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Two up-flow fixed bed reactors (UFBR) were operated for 8 months treating a model synthetic wastewater containing 2-fluorobenzoate (2-FB) and dichloromethane (DCM). The stability of the reactors under dynamic conditions, that is, sequentially alternating pollutants (SAP), shock loads, and starvation periods was assessed. Two support materials were used: expanded clay (EC) that does not adsorb 2-FB or DCM, and granular-activated carbon (GAC) that adsorbs 180 mg g(-1) of 2-FB and 390 mg g(-1) of DCM. The reactors were inoculated with a 2-FB-degrading strain (FB2) and a DCM degrader (TM1). 2-FB was fed at organic loads ranging from 0 to 800 mg L(-1) d(-1), while DCM was fed at 0-250 mg L(-1) d(-1). 2-FB or DCM were never detected at the outlet of the GAC reactor, while in the EC reactor outlet small amounts were observed. Nevertheless, the highest biological elimination capacity was observed in the EC reactor (over 700 mg L(-1) d(-1) of 2-FB). DGGE analysis revealed a fairly stable bacterial community with the largest shifts occurring during starvation periods and changes in feed composition. Several bacterial strains isolated from the reactors showed capacity for 2-FB degradation, while only strain TM1 degraded DCM.

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High nitrification rate at low pH in a fluidized bed reactor with chalk as the biofilm carrier

Cited by 21 publications

References 14 publications

High-Rate Nitrification at Low pH in Suspended- and Attached-Biomass Reactors

High-Rate Nitrification at Low pH in Suspended- and Attached-Biomass Reactors

Nitrification in a Biofilm at Low pH Values: Role of In Situ Microenvironments and Acid Tolerance

Treatment of halogenated organic compounds and monitoring of microbial dynamics in up‐flow fixed bed reactors under sequentially alternating pollutant scenarios

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