Use of biopolymers as solid substrates for denitrification (original) (raw)
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Laboratory-scale solid-phase denitrification (SPD) reactors for nitrate removal were constructed by acclimating activated sludge with poly (L-lactic acid) (PLLA) having weight-average molecular weights (Mw) of 9,900, 12,000, and 45,100 g mol −1. A good nitrate removal rate (3.5–5.3 mg NO3 −-N g [dry wt] −1 h −1) was found in the reactor containing PLLA of 9,900 g mol −1 , whereas the other two reactors with the higher Mw PLLA showed low nitrate removal efficiency. Microbial community dynamics in the low Mw PLLA-acclimated reactor were studied by 16S rRNA gene-targeted PCR-denaturing gradient gel electrophoresis and quinone profiling. Nonmetric multidimensional scaling analyses of these data sets revealed a marked population shift during acclimation of the SPD reactor with low Mw PLLA. The 16S rRNA gene clone library and culture-dependent analyses showed that bacteria belonging to the family Comamonadaceae predominated and played the primary role in denitrification in the PLLA-using reactor; however, none of the bacterial isolates from the reactor degraded PLLA. These results suggest that the nitrate removal property of the PLLA-using SPD reactor is attained through the bioavailability of hydrolysates released abiotically from the solid substrate.
Current Environmental Engineering, 2015
Current studies explore the viability, applicability and comparison of Pseudomonas aeruginosa and Pseudomonas stutzeri based biological denitrification of waters containing high concentration of nitrate and nitrite waste originating from various agricultural and industrial sources. This process converts the readily soluble nitrates to harmless nitrogen gas through a formation of series of intermediates. Experimental work involved use of varying concentration of nitrates and nitrites with different packing conditions, substrates and were analyzed by UV-Vis spectrophotometer. The parameters such as C/N ratio, temperature and pH were optimized for decreasing concentration of nitrates and nitrites. Best packing materials for nitrate reduction proved to be the agro waste based materials which have potential to be used for nitrate reduction of various waste water samples obtained around the city. Average nitrate reduction rates obtained for agro based waste packing condition exhibited about 96.55% and 95% for Pseudomonas aeruginosa and Pseudomonas stutzeri respectively. When applied for denitrification of waste water sample using the obtained reaction parameters, average nitrate reduction obtained was 53.84% and 33.72% for Pseudomonas aeruginosa and Pseudomonas stutzeri respectively. Based on the obtained observations and experimental results, general bioreactor for denitrification process has been designed.
Using natural biomass microorganisms for drinking water denitrification
Journal of environmental management, 2018
Among the methods that are studied to eliminate nitrate from drinking water, biological denitrification is an attractive strategy. Although several studies report the use of denitrifying bacteria for nitrate removal, they usually involve the use of sewage sludge as biomass to obtain the microbiota. In the present study, denitrifying bacteria was isolated from bamboo, and variable parameters were controlled focusing on optimal bacterial performance followed by physicochemical analysis of water adequacy. In this way, bamboo was used as a source of denitrifying microorganisms, using either Immobilized Microorganisms (IM) or Suspended Microorganisms (SM) for nitrate removal. Denitrification parameters optimization was carried out by analysis of denitrification at different pH values, temperature, nitrate concentrations, carbon sources as well as different C/N ratios. In addition, operational stability and denitrification kinetics were evaluated. Microorganisms present in the biomass res...
Microbes and Environments, 2005
A laboratory-scale solid-phase denitrification process for nitrogen removal was constructed by acclimating sewage activated sludge with poly(e-caprolactone) (PCL) as the sole substrate under denitrifying conditions. The sludge thus acclimated exhibited a nitrogen removal rate of 6-7 mg NO3-N g -1 h -1 with PCL as the sole source of reducing power. The microbial community and the distribution of denitrifying bacteria in this process were studied by rRNA-targeted fluorescence in situ hybridization, quinone profiling and standard cultivation methods. The culture-independent molecular and biomarker approaches demonstrated that members of the class Alphaproteobacteria predominated and those of Betaproteobacteria were the second most abundant group of bacteria in the process. The plate counts of denitrifying bacteria with a non-selective agar medium accounted for 6% of the total count and 10% of the direct viable count on average. The most probable number (MPN) obtained with PCL-containing medium under denitrifying conditions was one order of magnitude lower than the plate count. Most of the denitrifying isolates from the MPN enrichment tubes and 10% of the predominant denitrifying bacteria isolated by the plate-counting method were capable of degrading PCL. 16S rRNA gene sequence comparisons showed that the greater majority of the predominant denitrifiers were members of the genera Comamonas, Diaphorobacter and Paracoccus. All of the PCL-degrading denitrifying strains isolated were assigned to a previously unknown species of the genus Comamonas. The results of this study suggest that, apart from their PCL-degrading capacity, members of Alphaproteobacteria and Betaproteobacteria are mainly responsible for nitrogen removal in the PCL-acclimated denitrification process.
Microbiology Research Journal International, 2024
Denitrification is a crucial microbial process in the nitrogen cycle, transforming nitrate (NO₃⁻) into nitrogen gas (N₂), thereby mitigating nitrogen pollution in aquatic ecosystems. This microbial activity plays a vital role in wastewater treatment by removing excess nitrogen, which contributes to eutrophication and water contamination. The denitrification process involves various microbial communities, including bacteria such as Pseudomonas, Paracoccus, and Bacillus, which operate under anoxic conditions to achieve nitrogen reduction, an optimizing denitrification in wastewater treatment presents several challenges, such as maintaining ideal environmental conditions (e.g., carbon availability, oxygen levels, pH) and overcoming issues related to incomplete denitrification, which can lead to the production of harmful intermediates like nitrous oxide (N₂O). Despite these hurdles, recent advancements in microbial ecology, such as the use of biofilms, bioreactors, and genetic engineering, offer promising opportunities to enhance denitrification efficiency. This review explores the microbial ecology of the denitrification process, its application in wastewater treatment, and the challenges and opportunities associated with its practical implementation in reducing nitrogen pollution.
Iranian Journal of Environmental Health Science & Engineering, 2010
Nitrate contamination in ground and surface water is an increasingly serious environmental problem and only a few bacterial strains have been identified that have the ability to remove nitrogen pollutants from wastewater under thermophilic conditions. We therefore isolated thermophilic facultative bacterial strains from wood chips that had been composted with swine manure under aerated high temperature conditions so as to identify strains with denitrifying ability. Nine different colonies were screened and 3 long rod-shaped bacterial strains designated as SG-01, SG-02, and SG-03 were selected. The strain SG-01 could be differentiated from SG-02 and SG-03 on the basis of the method that it used for sugar utilization. The 16S rRNA genes of this strain also had high sequence similarity with Geobacillus thermodenitrificans 465 T (99.6%). The optimal growth temperatures (55C), pH values (pH 7.0), and NaCl concentrations (1%) required for the growth of strain SG-01 were established. This strain reduced 1.18 mM nitrate and 1.45 mM nitrite in LB broth after 48 h of incubation. These results suggest that the G. thermodenitrificans SG-01 strain may be useful in the removal of nitrates and nitrites from wastewater generated as a result of livestock farming.
Water Research, 2012
Nitrate Immobilization Activation energy Hyphomicrobium a b s t r a c t This study evaluated the nitrogen removal performance of polyethylene glycol (PEG) gel carriers containing entrapped heterotrophic denitrifying bacteria. A laboratory-scale denitrification reactor was operated for treatment of synthetic nitrate wastewater. The nitrogen removal activity gradually increased in continuous feed experiments, reaching 4.4 kg N m À3 d À1 on day 16 (30 C). A maximum nitrogen removal rate of 5.1 kg N m À3 d À1
Application of polyhydroxyalkanoates for denitrification in water and wastewater treatment
Applied Microbiology and Biotechnology, 2003
Application of polyhydroxyalkanoates (PHAs) and related biodegradable polymers has gained momentum in various areas of biotechnology. A promising application that started appearing in the past decade is the use of PHAs as the solid substrate for denitrification of water and wastewater. This type of denitrification, termed here "solid-phase denitrification", has several advantages over the conventional system supplemented with liquid organic substrate. PHAs serve not only as constant sources of reducing power for denitrification but also as solid matrices favorable for development of microbial films. In addition, in contrast to conventional processes, the use of PHAs has no potential risk of release of dissolved organic carbon with the resultant deterioration of effluent water quality. If the production cost of PHAs can be brought down, its application to the denitrification process will become economically more promising. A number of PHA-degrading denitrifying bacteria have been isolated and characterized from activated sludge and continuous flow-bed reactors for denitrification with PHAs. Most of these isolates have been assigned phylogenetically to members of b-Proteobacteria, especially those of the family Comamonadaceae. The metabolic and regulatory relationships between PHA degradation and denitrification, and the interactive relationship between PHA-degrading cells and the solid surface structure are important subjects awaiting future studies, which would provide a new insight into our comprehensive understanding of the solid-phase denitrification process.
Microbes and Environments, 2007
Two laboratory-scale solid-phase denitrification (SPD) reactors, designated reactors A and B, for nitrogen removal were constructed by acclimating activated sludge with pellets and flakes of poly(3-hydoxybutyrate-co-3hydroxyvalerate) (PHBV) as the sole added substrate under denitrifying conditions, respectively. The average denitrification rate in both reactors was 60 mg NO3 − -N g −1 (dry wt) h −1 under steady-state conditions, whereas washed sludge taken from the reactors showed an average denitrification rate of 20 mg NO3-N g −1 (dry wt) h −1 with fresh PHBV as the sole substrate. The difference in the denitrification rate between the two might be due to the bioavailability of intermediate metabolites as the substrate for denitrification, because acetate and 3-hydroxybutyrate were detected in the reactors. Most of the predominant denitrifiers isolated quantitatively by the platecounting method using non-selective agar medium were unable to degrade PHBV and were identified as members of genera of the class Betaproteobacteria by studying 16S rRNA gene sequence information. nirS and nosZ gene clone library-based analyses of the microbial community from SPD reactor A showed that most of the nirS and nosZ clones proved to be derived from members of the family Comamonadaceae and other phylogenetic groups of the Betaproteobacteria. These results suggest that the efficiency of denitrification in the PHBV-SPD process is affected by the availability of intermediate metabolites as possible reducing-power sources as well as of the solid substrate, and that particular species of the Betaproteobacteria play the primary role in denitrification in this process.