scholarly journals Effects of HRT on the efficiency of denitrification and carbon source release in constructed wetland filled with bark

2017 ◽  
Vol 75 (12) ◽  
pp. 2908-2915 ◽  
Author(s):  
Yinghe Jiang ◽  
Yao Li ◽  
Ying Zhang ◽  
Xiangling Zhang
Keyword(s):  
Carbon Source ◽  
Removal Efficiency ◽  
Constructed Wetland ◽  
Reaction Rate ◽  
Reaction Rate Constant ◽  
Municipal Sewage ◽  
First Order ◽  
N Removal ◽  
Carbon Release ◽  
The Relationship

Constructed wetland is widely used to treat municipal sewage. However, lack of carbon source always constraints the application of constructed wetland in advanced tailwater treatment process. Bark was used as the filler and external carbon source of constructed wetland in the study, and the effects of hydraulic retention time (HRT) on NO3−−N removal efficiency and carbon release velocity were explored. Results showed that the NO3−−N removal process was steady in the constructed wetland filled with bark without additional carbon source. The NO3−−N removal efficiency and NO3−−N concentration presented a first-order reaction. The reaction rate constant k was 0.4 day−1. The relationship between NO3−−N removal efficiency (η) and HRT (t) was η = 1-e−0.4t, and η was increased with increasing of HRT. η reached a maximum of 77% at HRT of 4.48 days. η obtained the minimum of 20% at HRT of 0.75 days. The relationship between the carbon source releasing velocity (v) by bark and HRT was v = 0.53(1.62/t-1/t2) + 0.32. v increased first and then decreased with HRT increasing. The maximum v was detected at t = 1.12 days.

scholarly journals Determination of exothermic batch reactor specific model parameters

2019 ◽  
Vol 292 ◽  
pp. 01063
Author(s):  
Lubomír Macků
Keyword(s):  
Rate Constant ◽  
Reaction Rate ◽  
Batch Reactor ◽  
Specific Model ◽  
Reaction Rate Constant ◽  
Order Reaction ◽  
First Order Reaction ◽  
Model Parameters ◽  
Reactor Model ◽  
First Order

An alternative method of determining exothermic reactor model parameters which include first order reaction rate constant is described in this paper. The method is based on known in reactor temperature development and is suitable for processes with changing quality of input substances. This method allows us to evaluate the reaction substances composition change and is also capable of the reaction rate constant (parameters of the Arrhenius equation) determination. Method can be used in exothermic batch or semi- batch reactors running processes based on the first order reaction. An example of such process is given here and the problem is shown on its mathematical model with the help of simulations.

Estimation of Effective Moisture Diffusivity in Starchy Materials Following Hydrothermal Treatments

2011 ◽  
Vol 312-315 ◽  
pp. 364-369 ◽  
Author(s):  
Seyed Amir Bahrani ◽  
Catherine Loisel ◽  
Jean Yves Monteau ◽  
Sid Ahmed Rezzoug ◽  
Zoulikha Maache-Rezzoug
Keyword(s):  
Reaction Rate ◽  
Effective Diffusivity ◽  
Moisture Diffusivity ◽  
Reaction Model ◽  
Reaction Rate Constant ◽  
Diffusivity Coefficient ◽  
Maize Starch ◽  
First Order ◽  
Melting Phenomenon ◽  
Treatment Processes

Two hydrothermal treatment processes (DV-HMT and DIC treatment) were investigated on standard maize starch for three processing temperatures; 100, 110 and 120°C. The gravimetric change of starch powder during the treatment was analyzed by a simultaneous water diffusion and starch reaction model. The effective diffusivity coefficient (Deff) and reaction rate constant (k) were estimated by minimizing the error between experimental and analytical results. The values of Deff and k clearly increased with temperature. The degree of starch melting was evaluated for the two treatments using the first-order reaction model as a function of processing time. The results suggest that the absorption process is controlled by water–starch reactivity that induces melting phenomenon of starch crystallites, which progresses when temperature increases. The two hydrothermal treatments considerably differ: DIC being more prone to water absorption as demonstrated by the values of Deff and k.

scholarly journals The alcoholysis of 1,2,2-trimethylpropyl-methylfluorophosphonate

2000 ◽  
Vol 65 (12) ◽  
pp. 857-866
Author(s):  
Mladjen Micevic ◽  
Slobodan Petrovic
Keyword(s):  
Kinetic Data ◽  
Reaction Rate ◽  
Frequency Factor ◽  
Reaction Rate Constant ◽  
Order Reaction ◽  
Activation Entropy ◽  
Second Order Reaction ◽  
Third Order ◽  
First Order ◽  
Kinetics Of

The alcoholysis of 1,2,2-trimethylpropyl-methylfluorophosphonate (soman) was examined with a series of alkoxides and in corresponding alcohols: methanol, ethanol, 1-propanol, 2-propanol, 2-methoxyethanol and 2-ethoxyethanol. Soman reacts with the used alkoxides in a second order reaction, first order in each reactant. The kinetics of the reaction between 1,2,2-trimethylpropyl-methylfluorophosphonate and ethanol in the presence of diethylenetriamine was also examined. A third order reaction rate constant was calculated, first order in each reactant. The activation energy, frequency factor and activation entropy were determined on the basis of the kinetic data.

Bisulfite Degrades Aflatoxin: Effect of Temperature and Concentration of Bisulfite

1978 ◽  
Vol 41 (10) ◽  
pp. 774-780 ◽  
Author(s):  
M. P. DOYLE ◽  
E. H. MARTH
Keyword(s):  
Rate Constant ◽  
Aflatoxin B1 ◽  
Reaction Rate ◽  
Reaction Rates ◽  
Reaction Rate Constant ◽  
Effect Of Temperature ◽  
Kcal Mole ◽  
First Order ◽  
Potassium Acid Phthalate ◽  
Acid Phthalate

Bisulfite reacted with aflatoxin B1 and G1 resulting in their loss of fluorescence. The reaction was first order with rate depending on bisulfite (or the bisulfite and sulfite) concentration(s). Aflatoxin G1 reacted more rapidly with bisulfite than did aflatoxin B1. In the presence of 0.035 M potassium acid phthalate-NaOH buffer (pH 5.5) plus 1.3% (vol/vol) methanol at 25 C, the reaction rate constant for degradation of aflatoxin G1 was 2.23 × 10−2h− and that for aflatoxin B1 was 1.87 × 10−2h− when 50 ml of reaction mixture contained 1.60 g of K2SO3. Besides bisulfite concentrations, temperature influenced reaction rates. The Q10 for the bisulfite-aflatoxin reaction was approximately 2 while activation energies for degrading aflatoxin B1 and aflatoxin G1 were 13.1 and 12.6 kcal/mole, respectively. Data suggest that treating foods with 50 to 500 ppm SO2 probably would not effectively degrade appreciable amounts of aflatoxin. Treating foods with 2000 ppm SO2 or more and increasing the temperature might reduce aflatoxin to an acceptable level.

The Ammonia Nitrogen Removal Enhanced by Biological Aerobic Filter Packed with a Novel Lightweight Zeolite Particles

2013 ◽  
Vol 361-363 ◽  
pp. 764-767
Author(s):  
Hai Tang ◽  
Long Ouyang ◽  
Xiang Zhao
Keyword(s):  
Removal Efficiency ◽  
Nitrogen Removal ◽  
Ammonia Nitrogen ◽  
Exponential Equation ◽  
N Concentration ◽  
N Removal ◽  
Optimal Value ◽  
Relationship Of ◽  
The Relationship

The ammonia nitrogen (NH4-N) removal enhanced by biological aerobic filter (BAF) packed with novel micro-mesoporous lightweight zeolite particles (LZP) as carrier. The results showed that the biofilm can quickly grow up using LZP as media in the BAF. HLR of 1.2 was chosen as the optimal value under the average influent NH4+-N concentration of 24.6 mg/L, percent NH4-N removal of 87% and NLR of 0.24 kgN/m3.d was achieved. The kinetic performance of the LZP-BAF indicated that the relationship of NH4-N removal efficiency with the L could be described by an exponential equation (Ce/Ci=exp (-1.24/L0.344)).

Effects of carbon source on N2O production in the process of simultaneous nitrification and denitrifica-tion via nitrite by aerobic granular sludge

2016 ◽  
Vol 1 (2) ◽  
pp. 10 ◽  
Author(s):  
Hong Liang ◽  
Xue Li ◽  
Shanshan Wang ◽  
Dawen Gao
Keyword(s):  
Nitrous Oxide ◽  
Carbon Source ◽  
Removal Efficiency ◽  
Release Rate ◽  
Sequencing Batch Reactor ◽  
Removal Rate ◽  
Batch Reactor ◽  
Granular Sludge ◽  
Aerobic Granular Sludge ◽  
N Removal

A sequencing batch reactor (SBR) was used to study the effect of carbon source (C6H12O6 and CH3COONa) and C/N ratio (C/N=4:1 and C/N=7:1) on the production of nitrous oxide (N2O) in the process of simultaneous nitrifica-tion and denitrification via nitrite (short-cut SND) by aerobic granular sludge and the removal efficiency of nitrogen under low dissolved oxygen (DO). The results showed that short-cut SND occurred in this system, and the removal ef-ficiency of total nitrogen (TN) at C6H12O6 and CH3COONa were 28.93 % and 41.19 %, respectively. However, the production of N2O significantly increased when CH3COONa was used as a carbon source. In addition, the rate of N2O release when CH3COONa was a carbon source was 8.34 times the rate when C6H12O6 was the carbon source. With the increase of C/N, removal rate of TN and the efficiency of the short-cut SND were increased. The removal efficiency of TN at C/N=7:1 was 90.33%, which was 2.19 times at C/N=4:1. The percentage of short-cut SND at C/N=4:1 and C/N=7:1 were 87.47% and 95.97%, respectively. The release rate of N2O from the original 1.14 mg/(g • min) decreased to 0.10 mg/(g • min) after increased the C/N from 4:1 to 7:1.

The 4,4'-dimethoxytrityl carbenium ion by ionization of 4,4'-dimethoxytrityl alcohol in acetonitrile - aqueous perchloric and nitric acids containing electrolytes: kinetics, equilibria, and ion-pair formation

1999 ◽  
Vol 77 (5-6) ◽  
pp. 530-536 ◽  
Author(s):  
Juan Crugeiras ◽  
Howard Maskill
Keyword(s):  
Rate Constant ◽  
Perchloric Acid ◽  
Reaction Rate ◽  
Reaction Rate Constant ◽  
Ion Pair ◽  
Ion Concentration ◽  
Forward Rate ◽  
First Order ◽  
Hydronium Ion ◽  
Carbenium Ion

We have studied the equilibration shown in eq. [3] of 4,4prime-dimethoxytrityl alcohol in aqueous perchloric and nitric acids containing low proportions of acetonitrile using stopped-flow kinetics techniques. The rate constants for the overall progress to equilibrium, kobs, have been resolved into forward and reverse components using the equilibrium UV absorbance and a value for the molar absorptivity of the 4,4prime-dimethoxytrityl carbenium ion determined in concentrated aqueous perchloric acid. The forward reaction (rate constant kf) is first order in both the alcohol and the acid concentrations; the reverse reaction (rate constant kr) is pseudo first order with respect to the carbocation. At constant hydronium ion concentration, the forward rate constant increases linearly with the concentration of electrolyte, whereas the reverse rate constant decreases. These effects depend upon the nature of the anion, but not the cation, and are not ionic strength effects. At constant anion concentrations, kf in both acids, and kr in perchloric acid, are independent of hydronium ion concentration; however, kr decreases with increasing hydronium ion concentration at constant nitrate concentration. At nonconstant ionic strength, changes in kf and kr observed in increasing concentrations of perchloric acid are attributable wholly to changes in perchlorate concentration. A mechanism is proposed which involves pre-equilibrium protonation of the alcohol, heterolysis of the protonated alcohol to give a 4,4prime-dimethoxytrityl carbenium ion - water ion-molecule pair, then conversion of this into a dissociated carbenium ion in equilibrium with ion pairs. To account for the strong effects of perchlorate and nitrate upon the forward rate constants, it is proposed that these anions provide additional reaction channels from the ion-molecule pair. However, we find no evidence of acid catalysis in the reaction of the ion-molecule pair (in contrast to our finding for the reaction of the corresponding ion-molecule pair formed from dimethoxytritylamine in acidic media). Some of the elementary rate and equilibrium constants of the proposed mechanism have been evaluated.Key words: trityl, carbenium ion, stopped-flow, ion pair, ion-molecule pair.

scholarly journals Immobilized rGO/TiO2 Photocatalyst for Decontamination of Water

Catalysts ◽  
2019 ◽  
Vol 9 (9) ◽  
pp. 708 ◽  
Author(s):  
Radek Zouzelka ◽  
Monika Remzova ◽  
Jan Plsek ◽  
Libor Brabec ◽  
Jiri Rathousky
Keyword(s):  
Photocatalytic Degradation ◽  
Reaction Rate ◽  
Reaction Rate Constant ◽  
Tio2 Photocatalyst ◽  
Limited Effect ◽  
Environmental Application ◽  
First Order ◽  
Beneficial Effects ◽  
Low Concentrations ◽  
Reduced Graphene

The preparation of immobilized graphene-based photocatalyst layers is highly desired for environmental applications. In this study, the preparation of an immobilized reduced graphene oxide (rGO)/TiO2 composite by electrophoretic deposition (EPD) was optimized. It enabled quantitative deposition without sintering and without the use of any dispersive additive. The presence of rGO had beneficial effects on the photocatalytic degradation of 4-chlorophenol in an aqueous solution. A marked increase in the photocatalytic degradation rate was observed, even at very low concentrations of rGO. Compared with the TiO2 and GO/TiO2 reference layers, use of the rGO/TiO2 composite (0.5 wt% of rGO) increased the first-order reaction rate constant by about 70%. This enhanced performance was due to the increased formation of hydroxyl radicals that attacked the 4-chlorophenol molecules. The direct charge transfer mechanism had only limited effect on the degradation. Thus, EPD-prepared rGO/TiO2 layers appear to be suitable for environmental application.

Treatment of laboratory wastewater in a tropical constructed wetland comparing surface and subsurface flow

2001 ◽  
Vol 44 (11-12) ◽  
pp. 499-506 ◽  
Author(s):  
A.A. Meutia
Keyword(s):  
Removal Efficiency ◽  
Constructed Wetland ◽  
Rainy Season ◽  
Transition Period ◽  
Subsurface Flow ◽  
Dry Season ◽  
Surface Flow ◽  
Cod Removal ◽  
N Removal ◽  
Removal Efficiencies

Wastewater treatment by constructed wetland is an appropriate technology for tropical developing countries like Indonesia because it is inexpensive, easily maintained, and has environmentally friendly and sustainable characteristics. The aim of the research is to examine the capability of constructed wetlands for treating laboratory wastewater at our Center, to investigate the suitable flow for treatment, namely vertical subsurface or horizontal surface flow, and to study the effect of the seasons. The constructed wetland is composed of three chambered unplanted sedimentation tanks followed by the first and second beds, containing gravel and sand, planted with Typha sp.; the third bed planted with floating plant Lemna sp.; and a clarifier with two chambers. The results showed that the subsurface flow in the dry season removed 95% organic carbon (COD) and total phosphorus (T-P) respectively, and 82% total nitrogen (T-N). In the transition period from the dry season to the rainy season, COD removal efficiency decreased to 73%, T-N increased to 89%, and T-P was almost the same as that in the dry season. In the rainy season COD and T-N removal efficiencies increased again to 95% respectively, while T-P remained unchanged. In the dry season, COD and T-P concentrations in the surface flow showed that the removal efficiencies were a bit lower than those in the subsurface flow. Moreover, T-N removal efficiency was only half as much as that in the subsurface flow. However, in the transition period, COD removal efficiency decreased to 29%, while T-N increased to 74% and T-P was still constant, around 93%. In the rainy season, COD and T-N removal efficiencies increased again to almost 95%. On the other hand, T-P decreased to 76%. The results show that the constructed wetland is capable of treating the laboratory wastewater. The subsurface flow is more suitable for treatment than the surface flow, and the seasonal changes have effects on the removal efficiency.

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