Denitrification in anaerobic digesters: Possibilities and influence of wastewater COD/N‐NO X ratio

Koetz

2005

Eng. Sanit. Ambient.

RESUMOUm sistema combinado reator UASB-reator aeróbio foi utilizado para a remoção de nitrogênio total e DQO de efluente de parboilização de arroz. O experimento foi realizado em reatores de bancada, com volumes de 4 L (UASB) e 3,6 L (reator aeróbio). Os parâmetros de operação pH, temperatura, alcalinidade e concentração de ácidos voláteis foram monitorados durante o perío-do experimental. Para o reator aeróbio de mistura completa, foi determinada, também, a concentração de oxigênio dissolvido. O sistema combinado reator UASB-reator aeróbio apresentou uma eficiência de remoção de carbono de 84% e uma eficiência de remoção de nitrogênio total Kjeldahl de 83%. O sistema proposto, nas condições experimentais, demonstrou ser adequado para remoção, simultânea, de DQO e de compostos oxidados de nitrogênio, em reator UASB. PALAVRAS-CHAVE:Digestão anaeróbia, reator UASB, nitrificação, desnitrificação. ABSTRACT An UASB-aerobic reactor system was used for the removal of total nitrogen and COD of effluent from industries of parboilized rice. The experiment was performed in reactors with volumes of 4 L (UASB reactor) and 3,6 L (aerobic reactor)

Section: Sistema Experimentalunclassified

Section: Introductionunclassified

“…O doador de elétrons pode ser obtido pela adição de uma fonte de carbono externa ou pelo uso do carbono que já existe no efluente a ser tratado (Akunna et al, 1992).…”

Section: Introductionunclassified

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Pós-tratamento de efluente nitrificado da parboilização de arroz utilizando desnitrificação em reator UASB

Koetz

2005

Eng. Sanit. Ambient.

Environmental Technology

“…This is because its optimal temperature is higher than the aerobic reactor temperature (about 16 ºC). As nitrates were not measured in the anaerobic digester (none were expected to be found there) the presence of denitrifying bacteria in it is not fully understood, but other authors reported the existence of denitrifiers in environments where nitrate or oxygen was not present for long periods of time which suggests that denitrifiers can survive in nitratefree anaerobic environments by carrying out low-level fermentation [58,59]. A detailed study of the metabolism of this microorganism is required in order to explain the results obtained.…”

mentioning

confidence: 99%

Identification and quantification of microbial populations in activated sludge and anaerobic digestion processes

Reyes

Borrás

Seco

et al. 2014

Identification and quantification of microbial populations in activated sludge and anaerobic digestion processesEight different phenotypes were studied in an activated sludge process (AeR) and anaerobic digester (AnD) in a full-scale WWTP by means of fluorescent in situ hybridization (FISH) and automated FISH quantification software. The phenotypes were: ammonia-oxidizing bacteria (AOB), nitrite-oxidizing bacteria (NOB), denitrifying bacteria, phosphate-accumulating organisms (PAO), glycogen-accumulating organisms (GAO), sulfate-reducing bacteria (SRB), methanotrophic bacteria and methanogenic archaea. Some findings were unexpected: (a) Presence of PAO, GAO and denitrifiers in the AeR possibly due to unexpected environmental conditions caused by oxygen deficiencies or its ability to survive aerobically; (b) Presence of SRB in the AeR due to high sulfate content of wastewater intake and possibly also due to digested sludge being recycled back into the primary clarifier; (c) Presence of methanogenic archaea in the AeR, which can be explained by the recirculation of digested sludge and its ability to survive periods of high oxygen levels; (d) Presence of denitrifying bacteria in the AnD which cannot be fully explained because the nitrate level in the AnD was not measured. However, other authors reported the existence of denitrifiers in environments where nitrate or oxygen was not present suggesting that denitrifiers can survive in nitrate-free anaerobic environments by carrying out low-level fermentation; (e) The results of this paper are relevant because focus on the identification of nearly all the significant bacterial and archaeal groups of microorganisms with a known phenotype involved in the biological wastewater treatment.Keywords: microbial diversity, FISH, phenotype, activated sludge, anaerobic digester IntroductionThe heart of a wastewater treatment plant (WWTP) is a dense microbial consortium in which organic and nutrient contaminants are removed, mainly by bacteria and archaea.There is, therefore, great interest in identifying the structure of this consortium and the functions of the groups of bacteria and archaea it is composed of.Many studies have investigated the diversity of microbial populations. Such studies now increasingly use molecular techniques that do not need the microorganisms to be isolated or cultivated, e.g. 16S rRNA analysis and fluorescence in situ hybridization (FISH). Other techniques such as microautoradiography-fluorescence in situ hybridization (MAR-FISH) have also been used to identify the bacterial community phylum level and phenotype in wastewater [1], along with other techniques such as polymerase chain reaction (PCR) combined with denaturing gradient gel electrophoresis (DGGE) [2], and pyrosequencing [3,4]. In other words, some studies using molecular techniques have been conducted to identify the microorganisms involved in the removal of nutrients such as phosphorus [5,6,7] and nitrogen [8,9,10,11,12,13], whilst other studies have focused on methanogenic archaea [14,15] and...

Stoichiometry of biological nitrogen transformations in wetlands and other ecosystems

Zhou

2007

Biotechnology Journal

The stoichiometric equations of ammonification, nitrification and denitrification have demonstrated that the nitrogen cycle in nature is rather complicated. The mechanisms of biological nitrogen transformations are very important for analysis, design, operation and optimal control of natural ecosystems or engineered systems for nitrogen removal, and accurate stoichiometric equations can help in the maintenance of these environments. In this study, the new stoichiometric equations of intermediate nitrification, and heterotrophic and autotrophic denitrification with sulfur as the electron donor have been developed and discussed. The parameter values of f(s) (the fraction of electron donor coupled to cell synthesis) in stoichiometric equations of nitrification and denitrification are calculated according to experimental results implied in previously reported stoichiometric equations. Some new stoichiometric relationships of nitrification and denitrification, such as the O(2) demand for nitrifications, chemical oxygen demand/N ratios and the yield coefficients for denitrifications have been established. The pathway steps of nitrification and denitrification have been discussed.