Kinetics of Indigenous Nitrate Reducing Sulfide Oxidizing Activity in Microaerophilic Wastewater Biofilms

23 páginas.-- 10 figuras.-- 2 tablas.-- 74 referencias.-- Supporting Information: Dataset. in http://dx.doi.org/10.1371/journal.pone.0149096Nitrate decreases sulfide release in wastewater treatment plants (WWTP), but little is known on how it affects the microzonation and kinetics of related microbial processes within the biofilm. The effect of nitrate addition on these properties for sulfate reduction, sulfide oxidation, and oxygen respiration were studied with the use of microelectrodes in microaerophilic wastewater biofilms. Mass balance calaculations and community composition analysis were also performed. At basal WWTP conditions, the biofilm presented a double-layer system. The upper microaerophilic layer (~300 μm) showed low sulfide production (0.31 μmol cm-3 h-1) and oxygen consumption rates (0.01 μmol cm-3 h-1). The anoxic lower layer showed high sulfide production (2.7 μmol cm-3 h-1). Nitrate addition decreased net sulfide production rates, caused by an increase in sulfide oxidation rates (SOR) in the upper layer, rather than an inhibition of sulfate reducing bacteria (SRB). This suggests that the indigenous nitrate reducing-sulfide oxidizing bacteria (NR-SOB) were immediately activated by nitrate. The functional vertical structure of the biofilm changed to a triple-layer system, where the previously upper sulfide-producing layer in the absence of nitrate split into two new layers: 1) an upper sulfide-consuming layer, whose thickness is probably determined by the nitrate penetration depth within the biofilm, and 2) a middle layer producing sulfide at an even higher rate than in the absence of nitrate in some cases. Below these layers, the lower net sulfide-producing layer remained unaffected. Net SOR varied from 0.05 to 0.72 μmol cm-3 h-1 depending on nitrate and sulfate availability. Addition of low nitrate concentrations likely increased sulfate availability within the biofilm and resulted in an increase of both net sulfate reduction and net sulfide oxidation by overcoming sulfate diffusional limitation from the water phase and the strong coupling between SRB and NR-SOB syntrophic relationshipAC was funded by projects P06-RNM-01787, P11-RNM-7199, the PAI group RNM-214 from Consejería de Innovación, Ciencia y Empresa, Junta de Andalucía and CTM2013-43857-R from the Spanish Ministry of Economy and Competitiveness. JMG was funded by the PAI group BIO-288 from Consejería de Innovación, Ciencia y Empresa, Junta de Andalucía. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Peer reviewe

Reduction of net sulfide production rate by nitrate in wastewater bioreactors. Kinetics and changes in the microbial community

15 páginas, 7 figuras, 5 tablas, 44 referencias.-- [email protected] addition stimulated sulfide oxidation by increasing the activity of nitrate-reducing sulfide-oxidizing bacteria (NR-SOB), decreasing the concentration of dissolved H2S in the water phase and, consequently, its release to the atmosphere of a pilot-scale anaerobic bioreactor. The effect of four different concentrations of nitrate (0.12, 0.24, 0.50, and 1.00 mM) was investigated for a period of 3 days in relation to sulfide concentration in two bioreactors set up at Guadalete wastewater treatment plant (Jerez de la Frontera, Spain). Physicochemical variables were measured in water and air, and the activity of bacteria implicated in the sulfur and nitrogen cycles was analyzed in the biofilms and in the water phase of the bioreactors. Biofilms were a net source of sulfide for the water and gas phases (7.22±5.3 μmol s−1) in the absence of nitrate dosing. Addition of nitrate resulted in a quick (within 3 h) decrease of sulfide both in the water and atmospheric phases. Sulfide elimination efficiency in the water phase increased with nitrate concentrations following the Michaelis–Menten kinetics (Ks=0.63 mM NO3 −). The end of nitrate addition resulted in a recovery or increase of initial net sulfide production in about 3 h. Addition of nitrate increased the activity of NR-SOB and decreased the activity of sulfate-reducing bacteria. Results confirmed the role of NR-SOB on hydrogen sulfide consumption coupled with nitrate reduction and sulfate recycling, revealing Sulfurimonas denitrificans and Paracoccus denitrificans as NR-SOB of great importance in this process.We acknowledge the support of the grants P06-RNM-01787, P11-RNM-7199, the PAI groups RNM-214 and BIO-288 from Consejería de Innovación, Ciencia y Empresa, Junta de Andalucía, Spain and CTM2009-10736 from the Ministerio de Innovación y Ciencia, Spain, which include cofinancing from FEDER funds. S. Papaspyrou was funded by a JAE-Doc fellowship (Programa JAE, JAE-Doc109, Spanish National Research Council) and a Marie Curie ERG action (NITRICOS, 235005, European Union).Peer reviewe

Biotecnología del consorcio microbiano formado por bacterias sulfatorreductoras y bacterias oxidadoras de sulfhídrico y reductoras de nitrato

[EN]: The production, accumulation and emission into the atmosphere of hydrogen sulfide in wastewater environments cause corrosion, toxicity and pollution problems that result in increased costs for the water company and health problems for workers. Nitrate treatment is one of the most accepted methods to reduce sulfide concentration in the aqueous and atmospheric phases in sewage systems and other industries where high concentrations of sulfide are reached, like the oil refining industry. However, a consensus has not been yet reached on the mechanisms through which nitrate acts on the microbial community. For this study firstly a pilot scale bioreactor system was designed to be placed at the Wastewater Treatment Plant (WWTP) Guadalete in Jerez de la Frontera. The bioreactor system had an automatic detection and action program to solve pump¿s obstructions and stops of the water flow. After verifying the correct operation of the system, one bioreactor was used as a control and different nitrate concentrations were assayed during 72 hours on the other bioreactor to test the effect on sulfide concentration in both the aqueous phase and the atmosphere. Nitrate caused a rapid effect. A complete cease of sulfide emission to the atmosphere was achieved, but sulfide did not disappear entirely from the aqueous phase at the assayed concentrations. Samples of biofilm from control and treated bioreactors were used to analyze the effect on the microbial community. The great complexity of microbial communities hinders their analysis and it is difficult to detect changes in response to different treatments. The less abundant bacterial groups who may respond to such treatments, like the bacteria involved in the processes of interest for this study, as sulfate reduction and sulfide oxidation, are especially hard to detect. The speed of nitrate response suggests that different groups of nitrate-reducing sulfide-oxidizing bacteria (NR-SOB) already present in the biofilm are activated. This is further supported by the equally fast reversibility of the process to pre-treatment levels of production and emission of sulfur after cessation of the treatment. The activity of some sulfate oxidizing bacterial groups (SRB) decreased but other SRB groups were favored, probably those with increased tolerance to nitrite, so that the sulfate reduction rate was unaltered. To learn more about both the typical microbial composition of the WWTP and the changes in the microbial community associated with nitrate dosage, water and biofilm samples were taken at three time points: pretreatment, after 72 h of treatment with nitrate and 24 h after cessation of treatment.Peer Reviewe

Microbial community fingerprinting by differential display-denaturing gradient gel electrophoresis

4 pages, 2 tables, 2 figures, 29 references. We acknowledge Aguas de Jerez E.M.S.A. for the use of the Guadalete wastewater treatment plant and for technical assistance and E. Iglesias from Yara Iberian for providing Nutriox.Complex microbial communities exhibit a large diversity, hampering differentiation by DNA fingerprinting. Herein, differential display-denaturing gradient gel electrophoresis is proposed. By adding a nucleotide to the 3'ends of PCR primers, 16 primer pairs and fingerprints were generated per community. Complexity reduction in each partial fingerprint facilitates sample comparison.This work was supported mainly by grant P06-RNM-01787 from the Consejería de Innovación, Ciencia y Empresa, Junta de Andalucía, Spain, and by projects CGL2009-12328/BOS and Consolider CSD2009-00006 from the Spanish Ministry of Science and Innovation.Peer reviewe

Freeze-lysable inorganic nutrients in intertidal sediments: dependence on microphytobenthos abundance

9 páginas, 6 figuras, 3 tablas.Freezing is a common treatment for the preservation of sediment samples. To test the role of microphytobenthos (MPB) abundance in the release of intracellular nutrients to the pore water due to cell breakage after freezing, referred to as freeze-lysable inorganic nutrients (FL-IN), parallel extractions were carried out from intertidal sediment cores collected in winter and summer from Cádiz Bay. After the determination of net production and dark respiration rates with O2 microsensors, sediment cores were subcored and sliced into several layers. The samples were divided into 2 fractions; the first was centrifuged to extract pore water (fresh) and the other was frozen at –80°C, thawed and centrifuged to extract pore water after freezing. NO2–, NO3–, NH4+ and PO43– were measured in the pore water extracted by both procedures. Chlorophylls a and c were extracted from the same sediment fractions. Freezing produced a significant increase in the pore water concentrations of all inorganic nutrients. Therefore, if the variable of interest is the inorganic nutrient concentration, pore water should be extracted from fresh samples. In addition, FL-IN correlated significantly with chlorophylls a and c (p < 0.01), r2 ranged from 0.54 for NO3– to 0.94 for NH4+, indicating that most FL-IN were released from MPB biomass. The relationships between chlorophyll a and FL-IN in winter and summer were significantly different, suggesting that nutrient accumulation by MPB changes seasonally and might affect nutrient cycling in intertidal sediments.The research was funded by grants CTM2006-04015 and CTM2009-10736 (Ministry of Education and Science, Spain) and P06-RNM-01787 (Junta de Andalucía) to A.C., and a FPU grant (AP2005-4897) from the Ministry of Education and Science to E.G. and a JAE-DOC fellowship to S.P. fellowship to S.PPeer reviewe

Sulfide elimination and changes in microbial community induced by nitrate addition in wastewater biofilms

Comunicación presentada a la citada conferencia, celebrada del 28 noviembre-1 diciembre, 2007, Sevilla, España.Peer reviewe