Shortcut biological nitrogen removal (SBNR) in microbial fuel cells (MFCs)

Microbial Fuel Cells (MFCs) represent nowadays a promising technology for the treatment of industrial wastewater. In this work the Shortcut Nitritation/Denitritation process in H-type MFC was investigated. The cell was fed by sodium acetate and fumaric acid, as organic carbon source, and ammonium sulphate, sodium nitrite and sodium nitrate as nitrogen source. Anaerobic digestion supernatant (digestate) was used as bacterial source. Batch tests were performed at a TOC/N ratio of 0.35, and Total Organic Carbon (TOC), pH and Open Circuit Voltage (OCV) were daily monitored. High organic carbon removal (up to 85%) in short time (within 6 days) were achieved. The nitritation proved to be independent of organic carbon amount and composition: an ammonium content reduction of about 45% was observed. Regarding the denitritation step, an almost quantitative removal of nitrite and nitrate was observed when fumaric acid was used as a carbon source

Increased salinity improves the thermotolerance of mesophilic nitrification

Nitrification is a well-studied and established process to treat ammonia in wastewater. Although thermophilic nitrification could avoid cooling costs for the treatment of warm wastewaters, applications above 40 A degrees C remain a significant challenge. This study tested the effect of salinity on the thermotolerance of mesophilic nitrifying sludge (34 A degrees C). In batch tests, 5 g NaCl L-1 increased the activity of aerobic ammonia-oxidizing bacteria (AerAOB) by 20-21 % at 40 and 45 A degrees C. For nitrite-oxidizing bacteria (NOB), the activity remained unaltered at 40 A degrees C, yet decreased by 83 % at 45 A degrees C. In a subsequent long-term continuous reactor test, temperature was increased from 34 to 40, 42.5, 45, 47.5 and 50 A degrees C. The AerAOB activity showed 65 and 37 % higher immediate resilience in the salt reactor (7.5 g NaCl L-1) for the first two temperature transitions and lost activity from 45 A degrees C onwards. NOB activity, in contrast to the batch tests, was 37 and 21 % more resilient in the salt reactor for the first two transitions, while no difference was observed for the third temperature transition. The control reactor lost NOB activity at 47.5 A degrees C, while the salt reactor only lost activity at 50 A degrees C. Overall, this study demonstrates salt amendment as a tool for a more efficient temperature transition for mesophilic sludge (34 A degrees C) and eventually higher nitrification temperatures

Small aggregates can cause nitrite accumulation in one-stage partial nitritation and anammox

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Shortcut Biological Nitrogen Removal (SBNR) in an MFC anode chamber under microaerobic conditions. The effect of C/N ratio and kinetic study

In this work, the feasibility of the Shortcut Biological Nitrogen Removal (SBNR) in the anodic chamber of a Microbial Fuel Cell (MFC) was investigated. Thirty day experiments were carried out using synthetic wastewaters with a Total Organic Carbon vs. nitrogen ratio (TOC/N) ranging from 0.1 to 1. Ammonium, nitrite, nitrate, pH, and TOC were daily monitored. Results showed that microaerobic conditions in the anodic chamber favored the development of nitritation reaction, due to oxygen transfer from the cathodic chamber through the membrane. Nitritation was found to depend on TOC/N ratio: at TOC/N equal to 0.1 an ammonium removal efficiency of up to 76% was observed. Once the oxygen supply to the cathodic chamber was stopped, denitritation occurred, favored by an increase of the TOC/N ratio: a nitrite removal of 80.3% was achieved at TOC/N equal to 0.75. The presence of nitrogen species strongly affected the potential of the electrochemical system: in the nitritation step, the Open Circuit Voltage (OCV) decreased from 180 mV to 21 mV with the decrease of the TOC/N ratio in the investigated range. Lower OCV values were observed in the denitritation steps since the organic carbon acted as the energy source for the conversion of nitrite to nitrogen gas. A kinetic analysis was also performed. Monod and Blackman models described the ammonium and the organic carbon removal processes well during the nitritation step, respectively, while Blackman-Blackman fitted experimental results of the denitritation step better

Metabolic network analysis reveals microbial community interactions in anammox granules.

Microbial communities mediating anaerobic ammonium oxidation (anammox) represent one of the most energy-efficient environmental biotechnologies for nitrogen removal from wastewater. However, little is known about the functional role heterotrophic bacteria play in anammox granules. Here, we use genome-centric metagenomics to recover 17 draft genomes of anammox and heterotrophic bacteria from a laboratory-scale anammox bioreactor. We combine metabolic network reconstruction with metatranscriptomics to examine the gene expression of anammox and heterotrophic bacteria and to identify their potential interactions. We find that Chlorobi-affiliated bacteria may be highly active protein degraders, catabolizing extracellular peptides while recycling nitrate to nitrite. Other heterotrophs may also contribute to scavenging of detritus and peptides produced by anammox bacteria, and potentially use alternative electron donors, such as H2, acetate and formate. Our findings improve the understanding of metabolic activities and interactions between anammox and heterotrophic bacteria and offer the first transcriptional insights on ecosystem function in anammox granules

Dynamic simulation of N2O emissions from a full-scale partial nitritation reactor

This study deals with the potential and the limitations of dynamic models for describing and predicting nitrous oxide (N2O) emissions associated with biological nitrogen removal from wastewater. The results of a three-week monitoring campaign on a full-scale partial nitritation reactor were reproduced through a state-of-the-art model including different biological N2O formation pathways. The partial nitritation reactor under study was a SHARON reactor treating the effluent from a municipal wastewater treatment plant sludge digester. A qualitative and quantitative comparison between experimental data and simulation results was performed to identify N2O formation pathways as well as for model identification. Heterotrophic denitrifying bacteria and ammonium oxidizing bacteria (AOB) were responsible for N2O formation under anoxic conditions, whereas under aerated conditions the AOB were the most important N2O producers. Relative to previously proposed models, hydroxylamine (NH2OH) had to be included as a state variable in the AOB conversions in order to describe potential N2O formation by AOB under anoxic conditions. An oxygen inhibition term in the corresponding reaction kinetics was required to fairly represent the relative contribution of the different AOB pathways for N2O production. Nevertheless, quantitative prediction of N2O emissions with models remains a challenge, which is discussed

Nutrient removal from UASB effluent in agro-industries

Phosphorus and nitrogen are important elements, making a major contribution to agricultural and industrial development, but their release to natural water bodies are the main causes of eutrophication. Anaerobic digestion yields effluents rich in ammonium and phosphate and poor in biodegradable organic carbon, thereby making them less suitable for conventional biological nitrogen and phosphorus removal. In addition, the demand for fertilizers is increasing, energy prices are rising and global phosphate reserves are declining. This requires both changes in wastewater treatment technologies and implementation of new processes. In this contribution the combination of an ureolytic MAP (magnesium ammonium phosphate) precipitation and autotrophic nitrogen removal is described on the anaerobic effluent of a potato processing company to obtain a more sustainable and cheaper method than conventional wastewater treatment processes. The results obtained during this experiment (6 weeks period) show that it is possible to recover phosphate as struvite and remove nitrogen with the autotrophic nitrogen process from wastewater after anaerobic digestion coming from a potato processing company. However further research is necessary to obtain stable results during several months, especially for the nitrite:ammonium ratio produced by the partial nitritation reactor

Effect of process parameters and operational mode on nitrous oxide emissions from a nitritation reactor treating reject wastewater

Nitrous oxide (N₂O) and methane emissions were monitored in a continuous granular airlift nitritation reactor from ammonium-rich wastewater (reject wastewater). N₂O emissions were found to be dependent on dissolved oxygen (DO) concentration in the range of 1-4.5 mg O₂/L, increasing within this range when reducing the DO values. At higher DO concentrations, N₂O emissions remained constant at 2.2% of the N oxidized to nitrite, suggesting two different mechanisms behind N₂O production, one dependent and one independent of DO concentration. Changes on ammonium, nitrite, free ammonia and free nitrous acid concentrations did not have an effect on N₂O emissions within the concentration range tested. When operating the reactor in a sequencing batch mode under high DO concentration (>5 mg o₂/L), N₂O emissions increased one order of magnitude reaching values of 19.3+/-7.5% of the N oxidized. Moreover, CH₄ emissions detected were due to the stripping of the soluble CH4 that remained dissolved in the reject wastewater after anaerobic digestion. Finally, an economical and carbon footprint assessment of a theoretical scaled up of the pilot plant was conducted

NITRITATION-ANAMMOX PILOT SYSTEM FOR NITROGEN REMOVAL FROM EFFLUENT OF UASB REACTOR TREATING SWINE WASTEWATER

Joint Research on Environmental Science and Technology for the Eart