Correlation between nitrous oxide (N2O) emission and carbon to nitrogen (COD/N) ratio in denitrification process: a mitigation strategy to decrease greenhouse gas emission and cost of operation

Abstract The reliability and accuracy of in-situ ion selective electrode and ultraviolet (NOx) probes have been investigated at four different treatment plants with different operational conditions. This study shows that the mentioned probes tend to compromise their accuracy and trending stability at lower NOx of <1.0 mg N/L, which if used as a measuring variable for PI feedback controller for denitrification (biological reduction of nitrate to nitrogen gas), would cause overfeeding the external carbon source. In-situ Clark-type N2O sensors, recently introduced for industrial scale use (Unisense Environment) could potentially open a new horizon in the automation of biological processes and particularly denitrification. To demonstrate the applicability of such probes for automation, two in-situ N2O probes were used in two treatment plants in parallel with NOx-N probes. The effects of operational conditions such as COD/N ratios and the correlation between NOx and N2O were investigated at those plants. N2O production at non-detect dissolved oxygen concentrations and pH of 7–7.2 were found to be a function of influent nitrogen load or the ratio of COD/NINFLUENT. Finally, using an N2O probe as a proxy sensor for nitrates is proposed as a measured variable in the PI feedback in the automation of the denitrification process with a NOx set point of <1.2 mg N/L).

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Greenhouse gas emissions from membrane bioreactors: analysis of a two-year survey on different MBR configurations

Water Science & Technology ◽

10.2166/wst.2018.366 ◽

2018 ◽

Vol 78 (4) ◽

pp. 896-903 ◽

Cited By ~ 1

Author(s):

Giorgio Mannina ◽

Kartik Chandran ◽

Marco Capodici ◽

Alida Cosenza ◽

Daniele Di Trapani ◽

...

Keyword(s):

Retention Time ◽

N2o Emission ◽

Influential Factors ◽

Membrane Bioreactors ◽

N2o Emissions ◽

Biological Phosphorus Removal ◽

N2o Production ◽

Operational Conditions ◽

Key Factor ◽

Nitrogen Ratio

Abstract This study aimed at evaluating the nitrous oxide (N2O) emissions from membrane bioreactors (MBRs) for wastewater treatment. The study investigated the N2O emissions considering multiple influential factors over a two-year period: (i) different MBR based process configurations; (ii) wastewater composition (municipal or industrial); (iii) operational conditions (i.e. sludge retention time, carbon-to-nitrogen ratio, C/N, hydraulic retention time); (iv) membrane modules. Among the overall analysed configurations, the highest N2O emission occurred from the aerated reactors. The treatment of industrial wastewater, contaminated with salt and hydrocarbons, provided the highest N2O emission factor (EF): 16% of the influent nitrogen for the denitrification/nitrification-MBR plant. The lowest N2O emission (EF = 0.5% of the influent nitrogen) was obtained in the biological phosphorus removal-moving bed-MBR plant likely due to an improvement in biological performances exerted by the co-presence of both suspended and attached biomass. The influent C/N ratio has been identified as a key factor affecting the N2O production. Indeed, a decrease of the C/N ratio (from 10 to 2) promoted the increase of N2O emissions in both gaseous and dissolved phases, mainly related to a decreased efficiency of the denitrification processes.

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IDENTIFICATION OF NITROUS OXIDE GENERATION IN SUBSURFACE WASTEWATER INFILTRATION SYSTEM FILLED WITH MIXED MATRIX

Journal of Environmental Engineering and Landscape Management ◽

10.3846/jeelm.2020.12073 ◽

2020 ◽

Vol 28 (2) ◽

pp. 88-94

Author(s):

Ying-Hua Li ◽

Lei Yang ◽

Hai-Bo Li ◽

Si-Qi Wang ◽

Fei Su

Keyword(s):

Nitrous Oxide ◽

Release Rate ◽

Potassium Nitrate ◽

Biological Processes ◽

Mixed Matrix ◽

N2o Production ◽

Total N ◽

Influent Concentration ◽

Rest Periods ◽

Denitrification Process

Subsurface wastewater infiltration systems (SWIS) are one of the important sources of nitrous oxide (N2O) production; understanding the biological processes and contributions of N2O will help control the amount of N2O produced. To quantitatively reveal the contribution of nitrification and denitrifiaction processes, 8 g potassium nitrate with 99.99 atom % 15N (i.e. 15N accounts for 99.99% of the total N) was dissolved in the influent (concentration: 3.3 g/L). Results showed that nitrification released more N2O within 0–12 h, accounting for 79.6 ± 2.4%. The denitrification process accounted for 88.5 ± 1.3% for N2O generation after the 12th hour. Thus, in order to effectively control the release of N2O, the denitrification process should be given more attention. The maximum release rate of N2O was 8.45 ± 0.8 mg/m2·h, which occurred near the end of the first wetting-drying cycle. Since then, peaks appeared periodically, mostly in the “rest” periods.

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Optimal operations for groundwater denitrification of drinking water using heterotrophic biological denitrification process

Water Science & Technology Water Supply ◽

10.2166/ws.2006.060 ◽

2006 ◽

Vol 6 (2) ◽

pp. 125-130

Author(s):

C.-H. Hung ◽

K.-H. Tsai ◽

Y.-K. Su ◽

C.-M. Liang ◽

M.-H. Su ◽

...

Keyword(s):

Drinking Water ◽

Removal Efficiency ◽

Nitrate Removal ◽

Drinking Water Treatment ◽

Nitrate Content ◽

Source Water ◽

Nitrogen Gas ◽

Negative Effect ◽

Denitrification Process ◽

Heterotrophic Denitrification

Due to the extensive application of artificial nitrogen-based fertilizers on land, groundwater from the central part of Taiwan faces problems of increasing concentrations of nitrate, which were measured to be well above 30 mg/L all year round. For meeting the 10 mg/L nitrate standard, optimal operations for a heterotrophic denitrification pilot plant designed for drinking water treatment was investigated. Ethanol and phosphate were added for bacteria growing on anthracite to convert nitrate to nitrogen gas. Results showed that presence of high dissolved oxygen (around 4 mg/L) in the source water did not have a significantly negative effect on nitrogen removal. When operated under a C/N ratio of 1.88, which was recommended in the literature, nitrate removal efficiency was measured to be around 70%, sometimes up to 90%. However, the reactor often underwent severe clogging problems. When operated under C/N ratio of 1.0, denitrification efficiency decreased significantly to 30%. Finally, when operated under C/N ratio of 1.5, the nitrate content of the influent was almost completely reduced at the first one-third part of the bioreactor with an overall removal efficiency of 89–91%. Another advantage for operating with a C/N ratio of 1.5 is that only one-third of the biosolids was produced compared to a C/N value of 1.88.

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Microbial N2O consumption in and above marine N2O production hotspots

The ISME Journal ◽

10.1038/s41396-020-00861-2 ◽

2020 ◽

Author(s):

Xin Sun ◽

Amal Jayakumar ◽

John C. Tracey ◽

Elizabeth Wallace ◽

Colette L. Kelly ◽

...

Keyword(s):

Kinetic Parameters ◽

Substrate Affinity ◽

N2o Production ◽

Anoxic Waters ◽

Production And Consumption ◽

Consumption Rates ◽

Anoxic Zones ◽

First Time ◽

Microbial N

AbstractThe ocean is a net source of N2O, a potent greenhouse gas and ozone-depleting agent. However, the removal of N2O via microbial N2O consumption is poorly constrained and rate measurements have been restricted to anoxic waters. Here we expand N2O consumption measurements from anoxic zones to the sharp oxygen gradient above them, and experimentally determine kinetic parameters in both oxic and anoxic seawater for the first time. We find that the substrate affinity, O2 tolerance, and community composition of N2O-consuming microbes in oxic waters differ from those in the underlying anoxic layers. Kinetic parameters determined here are used to model in situ N2O production and consumption rates. Estimated in situ rates differ from measured rates, confirming the necessity to consider kinetics when predicting N2O cycling. Microbes from the oxic layer consume N2O under anoxic conditions at a much faster rate than microbes from anoxic zones. These experimental results are in keeping with model results which indicate that N2O consumption likely takes place above the oxygen deficient zone (ODZ). Thus, the dynamic layer with steep O2 and N2O gradients right above the ODZ is a previously ignored potential gatekeeper of N2O and should be accounted for in the marine N2O budget.

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Field study on N2O emission from subsurface wastewater infiltration system under variable loading rates and drying-wetting cycles

Water Science & Technology ◽

10.2166/wst.2017.388 ◽

2017 ◽

Vol 76 (8) ◽

pp. 2158-2166 ◽

Cited By ~ 10

Author(s):

Ying-Hua Li ◽

Hai-Bo Li ◽

Xin-Yang Xu ◽

Si-Yao Xiao ◽

Si-Qi Wang ◽

...

Keyword(s):

Field Study ◽

Conversion Rate ◽

Oxygen Demand ◽

N2o Emission ◽

Conversion Ratio ◽

Gas Chromatograph ◽

Variable Loading ◽

N2o Production ◽

Loading Rates ◽

Operation Conditions

In this field study, the impacts of influent loadings and drying-wetting cycles on N2O emission in a subsurface wastewater infiltration (SWI) system were investigated. N2O emitted under different operation conditions were quantified using static chamber and gas chromatograph techniques. N2O conversion rate decreased from 6.6 ± 0.1% to 2.7 ± 0.1% with an increase in hydraulic loading (HL) from 0.08 to 0.24 m3/m2·d. By contrast, N2O conversion rate increased with increasing pollutant loading (PL) up to 8.2 ± 0.5% (PL 4.2 g N/m2·d) above which conversion rate decreased, confirming that N2O production was under the interaction of nitrification and denitrification. Taking into consideration the pollutants (chemical oxygen demand (COD), NH4+-N, NO3−-N and total nitrogen (TN)) removal ratio and N2O emission, optimal loading ranges and drying-wetting modes were suggested as HL 0.08–0.12 m3/m2·d, PL 3.2–3.7 g N/m2·d and 12 h:12 h, respectively. The results revealed that in SWI systems, conversion ratio of influent nitrogen to N2O could be between 4.5% and a maximum of 7.0%.

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Development of anammox reactor equipped with a degassing membrane to improve biomass retention

Water Science & Technology ◽

10.2166/wst.2012.222 ◽

2012 ◽

Vol 66 (2) ◽

pp. 451-456 ◽

Cited By ~ 5

Author(s):

Kosuke Matsunaga ◽

Tomonori Kindaichi ◽

Noriatsu Ozaki ◽

Akiyoshi Ohashi ◽

Yoshihito Nakahara ◽

...

Keyword(s):

Membrane Fouling ◽

N2o Emission ◽

Anammox Bacteria ◽

Component Ratio ◽

Reactor Performance ◽

Contributing Factors ◽

Nitrogen Gas ◽

Biomass Retention ◽

Gas Selectivity

In up-flow anammox reactors, one of the contributing factors to biomass wash-out is the adherence of nitrogen gas produced by the anammox reaction to biomass. In this study, we operated an up-flow anammox reactor equipped with a degassing membrane to minimize the biomass wash-out from the reactor by separating the produced gas from the biomass. In addition, both the effect of degassing on the anammox reactor performance and the durability of the membrane submerged in the anammox reactor were investigated. The results show that the use of the degassing membrane in the anammox reactor could (1) improve the biomass retention ability (by separating the produced gas from the biomass), and (2) increase the component ratio of anammox bacteria in the reactor. In addition, degassing could reduce the N2O emission produced in the reactor (for the gas selectivity of the degassing membrane). No membrane fouling was observed even after 2 months of operation without washing, indicating an advantage to the use of the degassing membrane.

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A Critical Review of the Biological Processes in the Chemical Absorption-biological Reduction Integrated System for NO Removal

Current Biochemical Engineering ◽

10.2174/2212711907666210215093307 ◽

2021 ◽

Vol 07 ◽

Author(s):

Wei Li

Keyword(s):

Catalytic Reduction ◽

Low Cost ◽

Reduction Process ◽

Integrated System ◽

Future Research ◽

Small Scale ◽

Biological Processes ◽

Chemical Absorption ◽

Biological Reduction ◽

Biological Reaction

: Exploring low-cost, green and safe technologies to provide an alternative to the conventional selective catalytic reduction process is key to the control of NOx emitted from small-scale boilers and other industrial processes. To meet the demand, the chemical absorption-biological reduction integrated system has been developing recently. chemical absorption-biological reduction integrated system applies Fe(II)EDTA for NO absorption and iron-reducing and denitrifying bacteria for absorbent regeneration. Many studies have focused on the enhancements of mass transfer and biological reaction, among which the biological processes were the rate-limiting steps. This review summarizes the current researches on the biological processes in the CABR system, which focuses on the mechanism and enhancement of biochemical reactions, and provides the possible directions of future research.

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Methodology for determining rom size distribution

Rem Revista Escola de Minas ◽

10.1590/0370-44672014670184 ◽

2014 ◽

Vol 67 (4) ◽

pp. 405-412

Author(s):

Christiane Ribeiro da Silva ◽

Vládia C. G. de Souza ◽

Jair C. Koppe

Keyword(s):

Size Distribution ◽

Distribution Curve ◽

Size Distributions ◽

Sampling Protocol ◽

Product Size ◽

Operational Conditions ◽

Specific Protocol ◽

Open Side ◽

Ore Dressing

A methodology to determine the size distribution curve of the ROM was developed in a Brazilian iron ore mine. The size of the larger fragments was determined taking photographs and setting the scale of the images to analyze their dimensions (length of their edges and areas). This was implemented according to a specific protocol of sampling that involves split and homogenization stages in situ of a considerable quantity of ore (about 259 metric tonnes). During the sampling process, larger fragments were separated and smaller size material was screened. The methodology was developed initially in order to preview the performance of a primary gyratory crusher that is fed directly from trucks. Operational conditions of the equipment such as closed and open-side settings could be adjusted previously, obtaining different product size distributions. Variability of size of the fragments affects subsequent stages of crushing and can increase circulating load in the circuit. This leads to a decrease of productivity or recovery of the ore dressing. The results showed insignificant errors of accuracy and reproducibility of the sampling protocol when applied to friable itabirite rocks.

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Semi-Electrical Conductivity of Gelcast Alumina Sintered under Nitrogen Atmosphere

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.11-12.493 ◽

2006 ◽

Vol 11-12 ◽

pp. 493-496 ◽

Cited By ~ 1

Author(s):

Ruben L. Menchavez ◽

Koichiro Adachi ◽

Masayoshi Fuji ◽

Minoru Takahashi

Keyword(s):

Electrical Conductivity ◽

Electrical Resistance ◽

Sintered Sample ◽

Carbon Composite ◽

Nitrogen Atmosphere ◽

Potential Candidate ◽

Nitrogen Gas ◽

Conductive Property ◽

Carbon Network

This work demonstrated an in-situ pyrolysis of gelcast alumina under reduction sintering to make alumina and carbon composite in providing semi-electrical conductivity. To increase the carbon content, the monomer was varied in the premix solution with reduction sintering in nitrogen gas. Two-probe method was used to measure electrical resistance of the sintered samples. The results revealed that the increase of monomer addition and sintering treatment were effective in reducing electrical resistance. The lowest value was 3.6×106-cm, which is a potential candidate for electrostatic shielding application. The reduction-sintered sample was re-sintered in an air in order to gain insight on the conductive path due to carbon network. Further tests such as XRD, TGA/DTA, and scanning electron microscopywere used to explain the semi-conductive property of the material.

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Microbial ecology and geoelectric responses across a groundwater plume

Interpretation ◽

10.1190/int-2015-0058.1 ◽

2015 ◽

Vol 3 (4) ◽

pp. SAB9-SAB21 ◽

Cited By ~ 2

Author(s):

Rory Doherty ◽

Blathnaid McPolin ◽

Bernd Kulessa ◽

Alessandra Frau ◽

Anna Kulakova ◽

...

Keyword(s):

Microbial Ecology ◽

Large Scale ◽

Contaminant Plume ◽

Electrochemical Gradient ◽

Iron Cycling ◽

Nitrogen Gas ◽

Nitrite Nitrate ◽

Redox Boundary ◽

Self Potential

We have used geophysics, microbiology, and geochemistry to link large-scale (30+ m) geophysical self-potential (SP) responses at a groundwater contaminant plume with its chemistry and microbial ecology of groundwater and soil from in and around it. We have found that microbially mediated transformation of ammonia to nitrite, nitrate, and nitrogen gas was likely to have promoted a well-defined electrochemical gradient at the edge of the plume, which dominated the SP response. Phylogenetic analysis demonstrated that the plume fringe or anode of the geobattery was dominated by electrogens and biodegradative microorganisms including Proteobacteria alongside Geobacteraceae, Desulfobulbaceae, and Nitrosomonadaceae. The uncultivated candidate phylum OD1 dominated uncontaminated areas of the site. We defined the redox boundary at the plume edge using the calculated and observed electric SP geophysical measurements. Conductive soils and waste acted as an electronic conductor, which was dominated by abiotic iron cycling processes that sequester electrons generated at the plume fringe. We have suggested that such geoelectric phenomena can act as indicators of natural attenuation processes that control groundwater plumes. Further work is required to monitor electron transfer across the geoelectric dipole to fully define this phenomenon as a geobattery. This approach can be used as a novel way of monitoring microbial activity around the degradation of contaminated groundwater plumes or to monitor in situ bioelectric systems designed to manage groundwater plumes.

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