Degradation Of NH3-N Research Articles

Evaluation of a liquid-phase plasma discharge process for ammonia oxidation in wastewater: Process optimization and kinetic modeling

Removing ammonia-nitrogen (NH3N) from wastewater is of paramount importance for wastewater treatment. In this study, a novel continuous liquid plasma process (CLPD) was evaluated to remove NH3N from synthetic wastewater. The Box–Behnken experimental design was used to optimize the main process parameters, including the initial NH3N concentration (50–200 mg/L), power input (150–300 W), and gas-flow rate (1.5–2.5 L/min), for efficient NH3N removal from wastewater. The gas-flow rate and power input were found to be significant factors affecting the removal efficiency of NH3N, whereas the initial concentration of NH3N played a vital role in determining the energy efficiency of the process. Under the optimal conditions of an initial NH3N concentration of 200 mg/L, applied power of 223 W, and gas-flow rate of 2.4 L/min, 98.91% of NH3N could be removed with a N2 selectivity of 92.91%, and the corresponding energy efficiency was 0.527 g/kWh after 2 hrs of treatment. A small fraction of undesirable NO3−-N (7.05 mg/L) and NO2−-N (2.83 mg/L) were also produced. Kinetic modeling revealed that NH3N degradation by the CLPD followed a pseudo-first-order reaction model, with a rate constant (k) of 0.03522 min−1. Optical emission spectroscopy (OES) was used to gather information about the active chemical species produced during the plasma discharge. The obtained spectra revealed the presence of several highly oxidative radicals, including ‧OH, ‧O, and ‧O2+. These results demonstrate the potential of liquid phase plasma discharge as a highly efficient technology for removing ammonia from aqueous solutions.

Electrochemical Oxidation of Landfill Leachate after Biological Treatment by Electro-Fenton System with Corroding Electrode of Iron.

Electrochemical oxidation of landfill leachate after biological treatment by a novel electrochemical system, which was constructed by introducing a corroding electrode of iron (Fec) between a boron-doped diamond (BDD) anode and carbon felt (CF) cathode (named as BDD–Fec–CF), was investigated in the present study. Response surface methodology (RSM) with Box–Behnken (BBD) statistical experiment design was applied to optimize the experimental conditions. Effects of variables including current density, electrolytic time and pH on chemical oxygen demand (COD) and ammonia nitrogen (NH3-N) removal efficiency were analyzed. Results showed that electrolytic time was more important than current density and pH for both COD and NH3-N degradation. Based on analysis of variance (ANOVA) under the optimum conditions (current density of 25 mA·cm−2, electrolytic time of 9 h and pH of 11), the removal efficiencies for COD and NH3-N were 81.3% and 99.8%, respectively. In the BDD–Fec–CF system, organic pollutants were oxidized by electrochemical and Fenton oxidation under acidic conditions. Under alkaline conditions, coagulation by Fe(OH)3 and oxidation by Fe(VI) have great contribution on organic compounds degradation. What is more, species of organic compounds before and after electrochemical treatment were analyzed by GC–MS, with 56 kinds components detected before treatment and only 16 kinds left after treatment. These results demonstrated that electrochemical oxidation by the BDD–Fec–CF system has great potential for the advanced treatment of landfill leachate.

The screening of high-efficiency ammonia-nitrogen degrading bacteria and their influencing factors were studied

By enriching the culture medium, three dominant bacteria(X1, X2 and X3) were selected from the farmland sludge. The degradation effect of X1, X2, X3 and mixed bacterium(X123) under different initial ammonia nitrogen(NH3-N) concentration, pH and C/N were studied under laboratory, the effect of X123 was compared with purchased bacteria(S1, S2 and S3) and strains in published literature. The results showed that X123 had the best effect when the initial NH3-N concentration was 20 mg·L−1, pH was 7 and C/N was 10, the degradation rate was 96.4% after 2 days of culture. Comparing X123 with S1, S2 and S3, it was found that X123 had the best effect. Comparing X123 with the strains in published literature, it can be seen that the difference for the degradation of NH3-N was very small, and the growth conditions of the strain were almost same. It was shown that X123 can effectively degrade NH3-N from wastewater, which has potential of application for treatment of nitrogen polluted wastewater.

Highly efficient removal of total nitrogen and dissolved organic compound in waste reverse osmosis concentrate mediated by chlorine radical on 3D Co3O4 nanowires anode

Reverse osmosis concentrate (ROC) from wastewater reclamation has posed significant disposal challenges due to its highly concentrated NH3-N, chloride ion and bio-refractory organics, and developing technologies for their removal are essential. Herein, we developed an efficient electrochemical system to remove total nitrogen and dissolved organic compound (DOC) simultaneously mediated by chlorine radical (Cl•), which is generated by activation of chloride ion existing in ROC on an inexpensive, three-dimensional Co3O4 nanowires. Results showed that the total nitrogen and total organic carbon removal were 98.2% and 56.9% in 60 min for synthetic ROC with 56 mg/L of NH3-N and 20 mg/L of DOC. The utilization of Co3O4 nanowires enhanced NH3-N degradation by 2.58 times compared with Co3O4 nanoplates, which were 1.69 and 17.5 times these of RuO2 and Pt. We found that structural Co3+/Co2+ acts as cyclic catalysis to produce Cl• via single-electron transfer, which convert NH3-N to N2 and lead to faster DOC degradation. This architecture provides abundant catalytic sites and sufficient accessibility of reactants. Small amount of nitrate generated by oxidation of NH3-N was further reduced to N2 on Pd-Cu/NF cathode. These findings provide new insights for utilization of waste Cl– and development of novel electrochemical system for ROC disposal.

NH3-N and COD Reduction in Endek (Balinese Textile) Wastewater by Activated Sludge under Different DO Condition with Ozone Pretreatment

Nitrogen and organic matter are part of the pollutant causing eutrophication in freshwater. Textiles industry like Endek is the main source of Nitrogen and organic matter. Tis paper aims to know the degradation process of Ammonia-Nitrogen (NH3-N) and Chemical Oxygen Demand (COD) with ozone pretreatment in operated by different DO level activated sludge. There are 2 scenarios of treatments in this study: with ozone pretreatment (R1) and without ozone pretreatment (R2). Wastewater treatment began with the seeding and acclimatization process. This acclimatization study showed the efficiency degradation of NH3-N and COD by 17.7 and 27.5 %. Biological Oxygen Demand (BOD)/COD level increased with ozone pretreatment, from 0.25 to 0.38, COD/TKN level stated at 3.26. Ozone pretreatment reduced NH3-N and COD by 23.8 and 34.1 %. Wastewater treatment with activated sludge operated by different DO levels showed efficiency of 44.2 % (R1) and 68.2 % (R2). This ammonia elimination was capable of preventing eutrophication in the waterbody. The efficiency of NH3-N and Nitrogen organic degradation was indicated by TKN (Total Kjeldahl Nitrogen) levels: 87 % (R1) and 79 % (R2). The concentration of Nitrate (NO3-N) increased from 2.9 to 5.5 mg/L when DO reached 1 - 3 mg/L. COD reduction levels in this study were 17 % (R1) and 42.5 % (R2). Ozone pretreatment could make the efficiency of wastewater treatment qualified into standard quality.

Thermal degradation and kinetic analysis of organic constituents in coal-gasification wastewater with a novel treatment

Abstract The traditional treatment of coal-gasification wastewater produces high solvent and operation cost, secondary pollution and long processing cycle. The aim of the paper was to attempt an alternative approach of wastewater treatment in coal gasification process. With wastewater being heated and sprayed into the gasifier, water participates in the water–gas shift reaction; meanwhile, organic constituents in wastewater are thermally degraded in specific conditions. In the study, thermal degradation and kinetic analysis of COD and NH3-N from Lurgi coal-gasification wastewater were conducted experimentally. The results showed that COD degradation can be divided into three reaction regions: 200–600, 600–1000 and 1000–1200°C. Also, NH3-N degradation can be divided as 200–400, 400–800 and 800–1200°C. The reaction temperature, oxygen concentration and reaction residence time can improve organic constituents’ degradation rate. The COD and NH3-N degradation rate ranks in the order oxidative > inert > reductive. It is because increasing oxygen concentration indicates more free radical generation and aromatic hydrocarbon polymerization was weakened. In addition, NO conversion with NH3 occurs within a narrow temperature window (800–1000°C). Thus, NO concentration reached the peak 230 mg/m3 at 800°C and then reduced with the increase in reaction temperature. Furthermore, a pseudo-first-order reaction model was implemented to analyse the kinetics of COD and NH3-N degradation rate. The results of the present study indicate that the proposed wastewater treatment is feasible and can be preferable reference for further practical application.

Improvement of Black-Odor Water by Pichia Strain GW1 under Optimized NH3-N Degradation Conditions.

In this study, a yeast strain with an outstanding NH3-N degradation ability was isolated from the sediment of a black-odor water channel in Guangdong Province, China. Based on phenotypic and phylogenetic analysis, this strain was identified as Pichia kudriavzevii GW1. The optimum conditions for NH3-N degradation by the GW1 strain were as follows: 0.3% inoculum concentration, 1.5 L/min aeration, pH 7, and a temperature of 35°C. Under optimized conditions, the GW1 strain degraded 95.5% of the NH3-N. The strain was then added to simulated black-odor water under optimal degradation conditions to investigate changes to the bacterial community over time. 16S rRNA sequencing of samples collected on days 0, 7, 14, and 21 showed that, in the presence of the GW1 strain, the relative abundances of the phyla Proteobacteria, Bacteroidetes, Chloroflexi, and Firmicutes increased in the black-odor water. In addition, the relative abundance of Propionivibrio, a known NH3-N degrading genus, increased. This study will facilitate the use of microbiological methods to repair black-odor water.

A Novel Method on Contaminant Degradation in Coal-gasification Wastewater

An alternative method of wastewater recycle in coal-gasification process was proposed and evaluated. The experiment was performed using lab-scale entrained-flow reactor system to study thermal degradation of COD and NH3-N contained in wastewater with the variant of temperature and reaction atmosphere. The results showed that reaction temperature has a significant effect on COD and NH3-N degradation, and degradation efficiency is obviously increased with temperature in the range of 400~1000 °C. The degradation efficiency of COD and NH3-N in different atmospheres ranks: oxidative > inert > reductive. The practical operation can meet the requirement to obtain high degradation efficiencies and the cost of facility reconfiguration will be reduced.

Enhancement of Supercritical Water Oxidation for Municipal Sludge Degradation

Different measures to enhance the removal efficiency of municipal sludge by supercritical water oxidation were further studied in a batch reactor, including catalytic supercritical water oxidation, co-oxidation with methanol and multi-injection of oxidant experiments at 580 °C, 25 MPa within a total residence time of 10 min and a total oxidant coefficient of 1.1. The experimental results showed that splitting the same amount of oxidant and feeding into reactor at two different residence time had a significant enhancement on the removal of COD compared with NH3-N, and the optimal second injection time of oxidant was 7.5 min in this investigation. Meanwhile, CuO catalyst could increase the degradation efficiency of both COD and NH3-N, and it increased with the amount of CuO added, which was better than methanol. Moreover, combining CuO with injecting oxidant multi-stage experiment produced the maximum organics degradation efficiency of 99.9% and 83.47% for COD and NH3-N, respectively, it demonstrates lower COD degradation of 99.58% and NH3-N degradation of 35.69% utilizing methanol at fixed reaction condition.

Application of Microbial Technology Used in Bioremediation of Urban Polluted River: A Case Study of Chengnan River, China

Contrary to the constraints in time, investment, and management of the traditional technology for waste water treatment, this paper seeks to propose a more advanced, reliable, and affordable new technology to restore urban polluted rivers to pristine quality levels. The paper also presents new ideas on the selection and use of microbial agents to improve the efficiency of pollution removal. It presents the successful implementation of microbial technology (MT) on Chengnan River, which was heavily polluted before MT implementation. Without artificial aeration, sediment dredging, or complete sewage interception, we directly sprayed a previously configured HP-RPe-3 Microbial Agent into the water body and sediment. We considered the feasibility of MT for treating polluted urban rivers from the perspective of several water quality indices evaluation methods. After the treatment, the concentration of dissolved oxygen (DO) reached 5.0 mg/L, the removal rates of ammonia nitrogen (NH3-N) and chemical oxygen demand (COD) reached 20% and 38% respectively, and the average degradation rate of total phosphorus (TP) along river was close to 15%. Also, the Nemerow Index of the river was reduced from 2.7 to 1.9. The Fuzzy Comprehensive Index shows a tendency for improvement from Inferior Grade V to a better grade (approximately Grade III). The color of the river water changed, from black or dark green, to its original color. The results indicate that the bioremediation technology of directly adding microbial agents mainly aimed for the degradation of NH3-N can preliminarily eliminate the black-odor phenomenon of urban rivers, and improve their water quality. It is expected that the MT application, and the concept of how to select the corresponding microbial agents according to main pollutants, can be widely accepted and applied to similar cases.

Quantitative study of degradation coefficient of pollutant against the flow velocity

The pollutant degradation coefficient is one of the key parameters to describe the water quality change, for establishing a reasonable water quality model and to determine the water carrying capacity and the environmental capacity. In this research, the environmental channel experiment is conducted to simulate the degradation evolution of the COD and NH3-N under different flow velocity conditions in typical pollution water. It is shown that the processes of the COD and the NH3-N's concentration over time are quite consistent with the first-order kinetic equation and the degradation coefficients increase with the increase of the flow velocity. When the flow velocity varies from 0 m·s−1 to 0.87 m·s−1, the degradation coefficients of the COD and NH3-N increase from 0.011 d−1 to 0.071 d−1 and 0.038 d−1 to 0.258 d−1, respectively. Moreover, the COD and NH3-N's degradation coefficients both have excellent correlation with the reaction time. There is a good linear relationship between the COD degradation coefficient and the flow velocity as well as a good power exponential function between the NH3-N degradation coefficient and the flow velocity. The comparative analysis of the Youth canal prototype monitoring and the calculation results shows that the quantitative formula obtained from the indoor water channel experiments gives results very close to the prototype observation results, which could reflect the degradation of pollutants in river water with varying flow velocity.

Organic matter and nitrogen removal at planted wetlands treating domestic septage with varying operational strategies.

A two-staged engineered wetland-based system was designed and constructed to treat raw domestic septage. Hydraulic loading rates (HLRs) of 8.75 and 17.5 cm/d were studied with four and eight daily dosings at the second stage of the system to investigate the influence of the regimes on septage treatment. Removal of organic matter (OM) was found to be HLR dependent, where the results indicated that the increase of HLR from 8.75 to 17.5 cm/d impaired the overall level of treatment in the wetland units. Effluent of wetland fed at HLR 17.5 cm/d presented significantly lower oxygen reduction potential and dissolved oxygen values than wetland fed at 8.75 cm/d, indicative of the occurrence of less aerobic and reductive conditions in the bed. The reoxygenation capability of the wetland units was found to be heavily affected by the dosing frequency especially under high hydraulic load (17.5 cm/d). NH3-N degradation was found to decrease with statistical importance when the wetland was flushed two times more frequently with smaller batches of influent. The number of hydraulic load fractionings did not seem to affect the level of treatments of OM and ammonia for both the wetlands fed under the lower HLR of 8.75 cm/d. Prediction of hydraulic limits and management of the feeding strategies are important in the vertical type of engineered wetlands to guarantee the treatment performance and minimize the chances of filter clogging.

Electrochemical Catalytic Oxidation Treatment of Coking Wastewater RO Brine

Coking wastewater RO brine is considered to be refractory, toxic, mutagenic and carcinogenic. Electrochemical oxidation has attracted wide attention in wastewater treatment because of its strong oxidation performance and ease of control. In this paper, the electrochemical degradation of NH3-N and COD were investigated at different anodes materials and current densities .The electrochemical oxidation using Ti/RuO2IrO2anode was effective and promising for advanced treatment of coking wastewater RO brine. COD and NH3-N concentration degraded 86% and 100% in 80min at the current density of 5 mA cm-2. Current density is the most important factor of organic degradation and energy consumption. When the current density was 10mA cm-2, the COD removal ratio quickly increased to 52.94% in 20min reaction time, but under high current density, the life of the electrode will be reduced. When the current density is too low, the electrolytic reaction time to reach standard needs to be 2h or more, which will perpetuate the equipment bulky, increase the cost of the equipment. The optimal current density is 5.0 ~ 7.5 mA cm-2. Unit per COD energy consumption is 114.4 kWh kgCOD-1, and unit per cubic meter wastewater energy consumption is 5.9 kWh m-3at the current density of 5 mA cm-2.

The Preparation of Loaded Photocatalyst for Advanced Treatment of NH<sub>3</sub>-N in Coking Water

Photocatalyst of Fe-Sm-Yb modified TiO2 loaded on clay brick was prepared for degradation of NH3-N in coking water. The influence factors of NH3-N degradation rates were discussed by single factor experiment and orthogonal experiment. The optimum process conditions of photocatalytic degradation NH3-N in coking water were confirmed. The results show that NH3-N degradation rates 82.23% were highest in the conditions of pH 6.5, photocatalyst charge of 1.4 g, illumination for 6h, reaction at 55°C, calcination at 500°C.

Community analysis of ammonia-oxidizing Betaproteobacteria at different seasons in microbial-earthworm ecofilters

Microbial-earthworm ecofilters (MEEs) can mitigate nitrogen in wastewater. We studied the ability of microorganisms in different layers in a MEE fed synthetic wastewater to remove ammonia nitrogen (NH3-N) and evaluated their communities of ammonia-oxidizing bacteria (AOB) belonging to Betaproteobacteria over the course of one year. The soil layer efficiently removed both chemical oxygen demand and NH3-N in summer and autumn. The NH3-N degradation rate constant (KNH3-N) generally peaked in autumn, when temperatures and AOB activities were highest. AOB diversities and compositions varied over time to different degrees in the matrices, but the presence of earthworms intensified AOB diversity in mid-level soil in autumn. Two dominant AOB groups, Nitrosospira cluster 3 and Nitrosomonas cluster 8, were found in the system. Furthermore, the Shannon index of AOB diversity depended more on KNH3-N than temperature. This study further improves our understanding of NH3-N removal in MEE wastewater treatment.

NH3-N degradation dynamics and calculating model of filtration bed height in Constructed Soil Rapid Infiltration

The research on Constructed Soil Rapid Infiltration (CSRI) system is in its infancy at home and abroad. There are several details about the mechanism and application of CSRI system needed to be further studied. A major limitation in the current research is the absence of degradation dynamics of pollutants, and the height of filtration bed in CSRI system currently determined by empirical judgment lacks accuracy and logicality. To solve these two problems, the soil column of CSRI system was utilized to treat domestic wastewater, meanwhile, the NH3-N degradation dynamics were studied according to the Monod equation, the research of Mann A T and the NH3-N degradation law. Then the mathematical model of filtration bed height was built based on NH3-N degradation dynamics equation in the soil column. It has been proven that within a limited range this model can calculate the appropriate height of filtration bed accurately in order to optimize technological parameters of hydraulic load and the concentration of influent NH3-N, improving the effluent quality of CSRI system.

Catalytic Wet Air Oxidation of Coke-Plant Wastewater on Ruthenium-Based Eggshell Catalysts in a Bubbling Bed Reactor

Catalytic wet air of coke-plant wastewater was studied in a bubbling bed reactor. Two types of supported Ru-based catalysts, eggshell and uniform catalysts, were employed. Compared with the results in the wet air oxidation of coke-plant wastewater, supported Ru uniform catalysts showed high activity for chemical oxygen demand (COD) and ammonia/ammonium compounds (NH3-N) removal at temperature of 250 degrees C and pressure of 4.8 MPa, and it has been demonstrated that the catalytic activity of uniform catalyst depended strongly on the distribution of active sites of Ru on catalyst. Compared to the corresponding uniform catalysts with the same Ru loading (0.25 wt.% and 0.1 wt.%, respectively), the eggshell catalysts showed higher activities for CODcr removal and much higher activities for NH3-N degradation. The high activity of eggshell catalyst for treatment of coke-plant wastewater can be attributed to the higher density of active Ru sites in the shell layer than that of the corresponding uniform catalyst with the same Ru loading. It has been also evidenced that the active Ru sites in the internal core of uniform catalyst have very little or no contribution to CODcr and NH3-N removal in the total oxidation of coke-plant wastewater.