Differential distribution of ammonia- and nitrite-oxidising bacteria in flocs and granules from a nitrifying/denitrifying sequencing batch reactor

A lab-scale sequencing batch reactor was operated with alternating anoxic/aerobic conditions for nitrogen removal. Flocs and granules co-existed in the same reactor, with distinct aggregate structure and size, for over 180 days of reactor operation' Process data showed complete nitrogen removal, with temporary nitrite accumulation before full depletion of ammonia in the aerobic phase. Microbial quantification of the biomass by fluorescence in situ hybridisation showed that granules contained most of the nitrite-oxidising bacteria (NOB) whereas the ammonium-oxidising bacteria (AOB) seemed to be more abundant in the flocs. This was supported by microsensor measurements, which showed a higher potential of NO2- uptake than NH4 uptake in the granules. The segregation is possibly linked to the different growth rates of the two types of nitrifiers and the reactor operational conditions, which produced different sludge retention time for flocs and granules. The apparent physical separation of AOB and NOB in two growth forms could potentially affect mass transfer of NO2- from AOB to NOB, but the data presented here shows that it did not impact negatively on the overall nitrogen removal. (c) 2006 Elsevier Inc. All rights reserved.

Treatment of linear alkylbenzene sulfonate in a horizontal anaerobic immobilized biomass reactor

Linear alkylbenzene sulfonate (LAS) is an anionic surfactant widely used to manufacture detergents and found in domestic and industrial wastewater. LAS removal was evaluated in a horizontal anaerobic immobilized biomass reactor. The system was filled with polyurethane foam and inoculated with sludge that was withdrawn from an up flow anaerobic sludge blanket reactor that is used to treat swine wastewater. The reactor was fed with easily degradable substrates and a solution of commercial LAS for 313 days. The hydraulic retention time applied was 12 h. The system was initially operated without detergent and resulted to 94% reduction of demand. The mass balance in the system indicated that the LAS removal efficiency was 45% after 180 days. From the 109th day to the 254th day, a removal efficiency of 32% was observed. The removal of LAS was approximately 40% when 1500 mg of LAS were applied in the absence of co-substrates suggesting that the LAS molecules were used selectively. Microscopic analyses of the biofilm revealed diverse microbial morphologies and denaturing gradient gel electrophoresis profiling showed variations in the total bacteria and sulfate-reducing bacteria populations. 16S rRNA sequencing and phylogenetic analyses demonstrated that members of the order Clostridiales were the major components of the bacterial community in the last step of the reactor operation. (c) 2009 Elsevier Ltd. All rights reserved.

Performance of a horizontal-flow anaerobic immobilized biomass (HAIB) reactor and dynamics of the microbial community during degradation of pentachlorophenol (PCP)

The anaerobic biological treatment of pentachlorophenol (PCP) and methanol as the main carbon source was investigated in a horizontal-flow anaerobic immobilized biomass (HAIB) reactor at 30 +/- 1 degrees C, during a 220-day trial period. The reactor biomass was developed as an attached biofilm on polyurethane foam particles, with 24 h of hydraulic retention time. The PCP concentrations, which ranged from 2.0 to 13.0 mg/L, were controlled by adding synthetic substrate. The HAIB reactor reduced 97% of COD and removed 99% of PCP. The microbial biofilm communities of the HAIB reactor amended with PCP, without previous acclimatization, were characterized by polymerase chain reaction (PCR) and amplified ribosomal DNA restriction analysis (ARDRA) with specific Archaea oligonucleotide primers. The ARDRA technique provided an adequate analysis of the community, revealing the profile of the selected population along the reactor. The biomass activities in the HAIB reactor at the end of the experiments indicated the development of PCP degraders and the maintenance of the population of methanogenic Archaea, ensuring the high efficiency of the system treating PCP with added methanol as the cosubstrate. The use of the simplified ARDRA method enabled us to monitor the microbial population with the addition of high concentrations of toxic compounds and highlighting a selection of microorganisms in the biofilm. (C) 2008 Published by Elsevier Ltd.

Evaluation of the microbial diversity in a horizontal-flow anaerobic immobilized biomass reactor treating linear alkylbenzene sulfonate

The purpose of this work was to assess the degradation of linear alkylbenzene sulfonate (LAS) in a horizontal-flow anaerobic immobilized biomass (HAIB) reactor. The reactor was filled with polyurethane foam where the sludge from a sanitary sewage treatment was immobilized. The hydraulic detention time (HDT) used in the experiments was of 12 h. The reactor was fed with synthetic substrate (410 mg l(-1) of meat extract, 115 mg l(-1) of starch, 80 mg l(-1) of saccharose, 320 mg l(-1) of sodium bicarbonate and 5 ml l(-1)of salt solution) in the following stages of operation: SI-synthetic substrate, SII-synthetic substrate with 7 mg l(-1) of LAS, SIII-synthetic substrate with 14 mg l(-1) of LAS and SIV-synthetic substrate containing yeast extract (substituting meat extract) and 14 mg l(-1) of LAS, without starch. At the end of the experiment (313 days) a degradation of similar to 35% of LAS was achieved. The higher the concentration of LAS, the greater the amount of foam for its adsorption. This is necessary because the isotherm of LAS adsorption in the foam is linear for the studied concentrations (2 to 50 mg l(-1)). Microscopic analyses of the biofilm revealed diverse microbial morphologies, while Denaturing Gradient Gel Eletrophoresis (DGGE) profiling showed variations in the population of total bacteria and sulphate-reducing bacteria (SRB). The 16S rRNA gene sequencing and phylogenetic analyses revealed that the members of the order Clostridiales were the major components of the bacterial community in the last reactor operation step.

The influence of immobilized biomass and particle size on the fluid dynamics of an anaerobic fluidized bed reactor

Fluid dynamic analysis is an important branch of several chemical engineering related areas, such as drying processes and chemical reactors. However, aspects concerning fluid dynamics in wastewater treatment bioreactors still require further investigation, as they highly influence process efficiency. Therefore, it is essential to evaluate the influence of biofilm on the reactor fluid dynamic behavior, through the analysis of a few important parameters, such as minimum fluidization velocity, bed expansion and porosity, and particle terminal velocity. The main objective of the present work was to investigate the fluid dynamics of an anaerobic fluidized bed reactor, having activated carbon particles as support media for biomass immobilization. Reactor performance was tested using synthetic residual water, which was prepared using the solution employed in BOD determination. The results showed that the presence of immobilized biomass increased particle density and altered the main fluid dynamic parameters investigated.

Anaerobic fluidized bed reactor with expanded clay as support for hydrogen production through dark fermentation of glucose

This study evaluated hydrogen production in an anaerobic fluidized bed reactor (AFBR) fed with glucose-based synthetic wastewater. Particles of expanded clay (2.8-3.35 mm) were used as a support material for biomass immobilization. The reactor was operated with hydraulic retention times (HRT) ranging from 8 to 1 h. The hydrogen yield production increased from 1.41 to 2.49 mol H(2) Mol(-1) glucose as HRT decreased from 8 to 2 h. However, when HRT was 1 h, there was a slight decrease to 2.41 mol H(2) Mol(-1) glucose. The biogas produced was composed of H(2) and CO(2), and the H(2) content increased from 8% to 35% as HRT decreased. The major soluble metabolites during H(2) fermentation were acetic acid (HAc) and butyric acid (HBu), accounting for 36.1-53.3% and 37.7-44.9% of total soluble metabolites, respectively. Overall, the results demonstrate the potential of using expanded clay as support material for hydrogen production in AFBRs. (c) 2008 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.

Kinetic behavior of nitrification in the post-treatment of poultry wastewater in a sequential batch reactor

A sequential batch reactor with suspended biomass and useful volume of 5 L was used in the removal of nutrients and organic matter in workbench scale under optimal conditions obtained by central composite rotational design (CCRD), with cycle time (CT) of 16 h (10.15 h, aerobic phase, and 4.35 h, anoxic phase) and carbon: nitrogen ratio (COD/NO2--N+NO3--N) equal to 6. Complete cycles (20), nitrification followed by denitrification, were evaluated to investigate the kinetic behavior of degradation of organic (COD) and nitrogenated (NH4+-N, NO2--N and NO3--N) matter present in the effluent from a bird slaughterhouse and industrial processing facility, as well as to evaluate the stability of the reactor using Shewhart control charts of individual measures. The results indicate means total inorganic nitrogen (NH4+-N+NO2- -N+NO3--N) removal of 84.32±1.59% and organic matter (COD) of 53.65±8.48% in the complete process (nitrification-denitrification) with the process under statistical control. The nitrifying activity during the aerobic phase estimated from the determination of the kinetic parameters had mean K1 and K2 values of 0.00381±0.00043 min-1 and 0.00381±0.00043 min-1, respectively. The evaluation of the kinetic behavior of the conversion of nitrogen indicated a possible reduction of CT in the anoxic phase, since removals of NO2--N and NO3--N higher than 90% were obtained with only 1 h of denitrification.

Development of Bioreactors for Nitrifying Water In Closed System Hatcheries Of Penaeid And Non-Penaeid Prawns

In the present study the development of bioreactors for nitrifying water in closed system hatcheries of penaeid and non-penaeid prawns. This work is an attempt in this direction to cater to the needs of aquaculture industry for treatment and remediation of ammonia and nitrate in penaeid and non-penaeid hatcheries, by developing nitrifying bacteria allochthonous to the particular environment under consideration, and immobilizing them on an appropriately designed support materials configured as reactors. Ammonia toxicity is the major limiting factors in penaeid and non-penaeid hatchery systems causing lethal and sublethal effects on larvae depending on the pH values. Pressing need of the aquaculture industry to have a user friendly and economically viable technology for the removal of ammonia, which can be easily integrated to the existing hatchery designs without any major changes or modifications. Only option available now is to have biological filters through which water can be circulated for the oxidation of ammonia to nitrate through nitrite by a group of chemolithotrophs known as nitrifying bacteria. Two types of bioreactors have been designed and developed. The first category named as in situ stringed bed suspended bioreactor(SBSBR) was designed for use in the larval rearing tanks to remove ammonia and nitrite during larval rearing on a continuous basis, and the other to be used for nitrifying freshly collected seawater and spent water named as ex situ packed bed bioreactior(PBBR). On employing the two reactors together , both penaeid and non-penaeid larval rearing systems can be made a closed recirculating system at least for a season. A survey of literature revealed that the in situ stringed bed suspended reactor developed here is unique in its design, fabrication and mode of application.

Development of bioreactors for nitrifying sewage

Nitrification is the biological oxidation of ammonium, first to nitrite and then to nitrate by two groups of aerobic, chemolithotrophic bacteria belonging to the family Nitrobacteriaceae. The biological nitrification in municipal wastewater treatment is important in those cases were ammonia removal requirement specially exist. In a trickling filter or in an activated sludge system nitrification is rate limiting and thus necessitates longer detention time. The combined carbon oxidation-nitrification processes generally have low population of nitrifiers due to a high ratio of BOD to total nitrogen in the effluent. This necessitates, separate carbon and nitrogen oxidation processes, which thus minimizes wash out ofthe nitrifiers. Therefore, a separate stage nitrification has become essential to achieve faster and efficient removal of ammonia from the wastewater. The present work deals with the development of bio reactor for nitrifying of sewage as the tertiary process so that the treated wastewater can be used for irrigation, algal culture or fish culture

Immobilization of nitrifying bacterial consortia on wood particles for bioaugmenting nitrification in shrimp culture systems

Shrimp grow out systems under zero water exchange mode demand constant remediation of total ammonia nitrogen (TAN) andNO2 −–Nto protect the crop. To address this issue, aninexpensive and user-friendly technology using immobilized nitrifying bacterial consortia (NBC) as bioaugmentors has been developed and proposed for adoption in shrimp culture systems. Indigenous NBC stored at 4 °C were activated at room temperature (28 °C) and cultured in a 2 L bench top fermentor. The consortia, after enumeration by epifluorescence microscopy,were immobilized on delignifiedwood particles of a soft wood tree Ailantus altissima (300–1500 μm) having a surface area of 1.87m2 g−1. Selection of wood particle as substratumwas based on adsorption of NBC on to the particles, biofilm formation, and their subsequent nitrification potential. The immobilization could be achievedwithin 72 h with an initial cell density of 1×105 cells mL−1. On experimenting with the lowest dosage of 0.2 g (wet weight) immobilized NBC in 20 L seawater, a TAN removal rate of 2.4 mg L−1 within three days was observed. An NBC immobilization device could be developed for on site generation of the bioaugmentor preparation as per requirement. The product of immobilization never exhibited lag phase when transferred to fresh medium. The extent of nitrification in a simulated systemwas two times the rate observed in the control systems suggesting the efficacy in real life situations. The products of nitrification in all experiments were undetectable due to denitrifying potency, whichmade the NBC an ideal option for biological nitrogen removal. The immobilized NBC thus generated has been named TANOX (Total Ammonia Nitrogen Oxidizer)

Molecular characterization of the nitrifying bacterial consortia employed for the activation of bioreactors used in brackish and marine aquaculture systems

The addition of commercial nitrifying bacterial products has resulted in significant improvement of nitrification efficiency in recirculating aquaculture systems (RAS). We developed two nitrifying bacterial consortia (NBC) from marine and brackish water as start up cultures for immobilizing commercialized nitrifying bioreactors for RAS. In the present study, the community compositions of the NBC were analyzed by universal 16S rRNA gene and bacterial amoA gene sequencing and fluorescence in situ hybridization (FISH). This study demonstrated that both the consortia involved autotrophic nitrifiers, denitrifiers as well as heterotrophs. Abundant taxa of the brackish water heterotrophic bacterial isolates were Paenibacillus and Beijerinckia spp. whereas in the marine consortia they were Flavobacterium, Cytophaga and Gramella species. The bacterial amoA clones were clustered together with high similarity to Nitrosomonas sp. and uncultured beta Proteobacteria. FISH analysis detected ammonia oxidizers belonging to b subclass of proteobacteria and Nitrosospira sp. in both the consortia, and Nitrosococcus mobilis lineage only in the brackish water consortium and the halophilic Nitrosomonas sp. only in the marine consortium. However, nitrite oxidizers, Nitrobacter sp. and phylum Nitrospira were detected in both the consortia. The metabolites from nitrifiers might have been used by heterotrophs as carbon and energy sources making the consortia a stable biofilm.

Electrocoagulation/flotation followed by fluidized bed anaerobic reactor applied to tannery effluent treatment

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Phenol degradation in an anaerobic fluidized bed reactor packed with low density support materials

The objective of this research was to study phenol degradation in anaerobic fluidized bed reactors (AFBR) packed with polymeric particulate supports (polystyrene - PS, polyethylene terephthalate - PET, and polyvinyl chloride - PVC). The reactors were operated with a hydraulic retention time (HRT) of 24 h. The influent phenol concentration in the AFBR varied from 100 to 400 mg L-1, resulting in phenol removal efficiencies of similar to 100%. The formation of extracellular polymeric substances yielded better results with the PVC particles; however, deformations in these particles proved detrimental to reactor operation. PS was found to be the best support for biomass attachment in an AFBR for phenol removal. The AFBR loaded with PS was operated to analyze the performance and stability for phenol removal at feed concentrations ranging from 50 to 500 mg L-1. The phenol removal efficiency ranged from 90-100%.

Estudio de la influencia de la relación C/N en la desnitrificación y metanogénesis de aguas residuales en un reactor anaeróbico de lecho fluidizado inverso

La nitrificación-desnitrificación es el proceso biológico tradicional para la remoción de nitrógeno de las aguas residuales (Ruiz G. et al., 2006a), siendo fundamental ya que contribuye a controlar la eutroficación de los cuerpos receptores. Debido al deterioro que sobre la disponibilidad de los recursos han ejercido las actividades antropogénicas, es necesario orientar el tratamiento de las aguas residuales hacia tecnologías que ofrezcan el mayor grado de sustentabilidad, planteando innovaciones en el tratamiento. El presente proyecto de tesis doctoral versa sobre el estudio de la influencia de la relación C/N en la desnitrificación y metanogénesis de aguas residuales urbanas en un reactor anaeróbico de lecho fluidizado inverso (RLFI). Previamente a la realización de las pruebas experimentales de variación de la relación C/N, se llevó a cabo la etapa de arranque del RLFI la cual se inició en modo batch, favoreciendo la formación y adhesión de biopelícula al medio de soporte utilizado (Extendosphere). Después, sobrevino la operación en modo continuo desde una carga volumétrica aplicada (CVA) de 0.5 g DQOs/L⋅d hasta alcanzar 4 g DQOs/L⋅d, carga volumétrica a la cual se logró la plena estabilización del reactor, siendo la alta variabilidad de la concentración de DQOs en el agua residual urbana de alimentación, la principal problemática que ocasionó retrasos en la estabilidad del reactor. A una CVA de 4 g DQOs/L⋅d en estado estacionario, el valor mínimo de eficiencia de remoción de DQOs fue del 32.36% y el máximo de 66.99%. En estas condiciones el porcentaje de metano presente en el biogás producido tuvo un valor medio de 85.57 ± 2.93%, siendo un valor alto comparado con otros porcentajes de metano encontrados en la digestión anaerobia de aguas residuales urbanas. El YCH4 tuvo un valor medio de 0.316 ± 0.110 LCH4/g DQOrem⋅día. Los porcentajes de metanización variaron en el rango de 20.50 a 100%, registrándose un valor medio de 73.42 ± 25.63%. La considerable variabilidad en el porcentaje de metanización se debió principalmente a que se presentaron eventos de lavado de soporte colonizado, lo cual propició que las actividades metabólicas fueran orientadas hacia formación de biopelícula (anabolismo) en vez de estar dirigidas hacia producción de metano (catabolismo). En relación a los ensayos con variación de la relación C/N, se manejaron relaciones DQOs/N-NO3 en el rango de 1.65 a 21.1 g DQOs/g N-NO3. La tasa de remoción anaerobia de DQOs se incrementó con la concentración de sustrato en una relación casi lineal, ajustándose a una cinética de primer orden, lo que regularmente se presenta a concentraciones bajas de sustrato. La eficiencia del proceso de desnitrificación fue por lo regular alta, incrementándose ligeramente con la concentración de DQOs en el influente, con valores en el rango de 73.8 a 99.1%. Por otra parte, la tasa de remoción por metanogénesis se incrementó con la concentración relativa de sustrato (es decir, a mayores relaciones DQOs/N-NO3), siendo más sensitiva la metanogénesis a la concentración relativa de sustrato que la desnitrificación. Conforme aumentó la relación DQOs/N-NO3, la desnitrificación, de ser la ruta metabólica principal de utilización de la materia orgánica (comparada con la metanización), empezó a combinarse con la metanización. De manera evidente, a las relaciones DQOs/N-NO3 probadas, se manifestaron más las actividades desnitrificantes, quedando reflejadas por el alto porcentaje de utilización de la DQOs removida hacia la desnitrificación. La relación experimental DQOs/N-NO3 a la cual se pudiera haber cumplido con el requerimiento de materia orgánica (en términos de DQOs) para la desnitrificación de nitratos en las aguas residuales urbanas tratadas resultó aproximadamente ser igual a 7.1 g DQOs/g N-NO3. A una CVA de 4 g DQOs/L⋅d, se obtuvo un diámetro promedio máximo de soporte colonizado igual a 266.106 ± 69.279 μm aunque, hay que indicarlo, se presentaron fluctuaciones, las cuales se reflejaron también en el espesor de la biopelícula, el cual tuvo un valor máximo de 50.099 μm y un valor promedio de 37.294 ± 11.199 μm. Estas fluctuaciones pudieron deberse a la existencia de corrientes preferenciales dentro del reactor, las cuales no permitieron un acceso equitativo del sustrato a todo el lecho. Nitrification-denitrification is the traditional biological process for nitrogen removal from wastewaters (Ruiz G. et al., 2006a), being fundamental since it contributes to control the eutrophication of the receiving waters. Due to the deterioration that on the availability of the aquatic resources the anthropogenic activities have exerted, it is necessary to orient the treatment of wastewaters towards technologies that offer the greater degree of sustainability, raising innovations in the treatment. This work studied the influence of C/N ratio on denitrification and methanogenesis of urban wastewaters in an inverse fluidized bed reactor (IFBR). Previously to the accomplishment of the experimental tests with variation of C/N ratio, the start up of the IFBR was carried out in batch way, encouraging the formation and adhesion of biofilm to Extendosphere, which it was used as support. The operation in continuous way carried out from an organic loading rate (OLR) of 0.5 g CODs/L ∙ d to 4 g CODs/L ∙ d, when the steady-state was reached. The high variability of the CODs of the urban wastewaters caused delays in the stability of the reactor. Once stationary state was reached, the removal efficiency of CODs ranged from 32.36 to 66.99% to 4 g CODs/L ∙ d. In these conditions the percentage of methane in produced biogas had an average value of 85.57 ± 2.93%, being a high value compared with other studies treating anaerobically urban wastewaters. The YCH4 had an average value of 0.316 ± 0.110 LCH4/g CODrem ∙ d. The percentage of methanisation ranged from 20.50 to 100%, with an average value of 73.42 ± 25.63%. The considerable variability in the methanisation percentage occurred mainly due events of wash-out of colonized support, which caused that the metabolic activities were oriented towards formation of biofilm (anabolism) instead of methane production (catabolism). Concerning the tests with variation of C/N ratio, CODs/NO3-N ratios from 1.65 to 21.1 g CODs/g NO3-N were proved. The CODs anaerobic removal rate increased with the substrate concentration in an almost linear relation, adjusting to a kinetic of first order, which regularly appears to low concentrations of substrate. Efficiency of the denitrification process was regularly high, and it increased slightly with the CODs concentration in the influent, ranging from 73.8 to 99.1%. On the other hand, the CODs removal rate by methanogenesis increased with the substrate relative concentration (e.g., to greater CODs/NO3-N ratios), being more sensitive the methanogenesis to the substrate relative concentration that the denitrification. When the CODs/NO3-N ratio increased, the denitrification, of being the main metabolic route of use of the organic matter (compared with the methanogenesis), began to be combined with the methanogenesis. Definitively, to the proven CODs/NO3-N ratios the denitrification processes were more pronounced, being reflected by the high percentage of use of the removed CODs towards denitrification. The experimental CODs/NO3-N ratio to which it was possible to have been fulfilled the requirement of organic matter (in terms of CODs) for the denitrification of nitrates in urban wastewaters turned out to be approximately 7.1 g CODs/g NO3-N. It was obtained a maximum average diameter of colonized support of 266.106 ± 69.279 μm to 4 g CODs/L ∙ d, although it is necessary to indicate that appeared fluctuations in the thickness of biofilm, which had a maximum value of 50.099 μm and an average value of 37.294 ± 11.199 μm. These fluctuations could be due to the existence of preferential currents within the reactor, which did not allow an equitable access of the substrate to all the bed.

Enrichment of nitrifying microbial communities from shrimp farms and commercial inocula

Nitrifying bacteria were selected from shrimp farm water and sediment (natural seed) in Thailand and from commercial seed cultures. The microbial consortia from each source giving the best ammonia removal during batch culture pre-enrichments were used as inocula for two sequencing batch reactors (SBRs). Nitrifiers were cultivated in the SBRs with 100 mg NH4-N/I and artificial wastewater containing 25 ppt salinity. The two SBRs were operated at a 7 d hydraulic retention time (HRT) for 77 d after which the HRT was reduced to 3.5 d. The amounts of ammonia removed from the influent by microorganisms sourced from the natural seed were 85% and 92% for the 7 d HIRT and the 3.5 d HRT, respectively. The ammonia removals of microbial consortia from the commercial seed were 71% and 83% for these HRTs respectively. The quantity of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) was determined in the SBRs using the most probable number (MPN) technique. Both AOB and NOB increased in number over the long-term operation of both SBRs. According to quantitative fluorescence in situ hybridisation (FISH) probing, AOB from the natural seed and commercial seed comprised 21 +/- 2% and 30 +/- 2%, respectively of all bacteria. NOB could not be detected with currently-reported FISH probes, suggesting that novel NOB were enriched from both sources. Taken collectively, the results from this study provide an indication that the nitrifiers from shrimp farm sources are more effective at ammonia removal than those from commercial seed cultures.