Influence of flow velocity on the removal of faecal coliforms in horizontal subsurface flow constructed wetland

2012 ◽  
Vol 66 (12) ◽  
pp. 2808-2813 ◽  
Author(s):  
W. S. Lohay ◽  
T. J. Lyimo ◽  
K. N. Njau
Keyword(s):  
Flow Velocity ◽  
Rate Constants ◽  
Membrane Filtration ◽  
Removal Rate ◽  
Plug Flow ◽  
Flow Equation ◽  
Faecal Coliforms ◽  
Pathogen Removal ◽  
Removal Rates ◽  
Filtration Technique

In order to determine the influence of flow velocity on the removal of faecal coliforms (FC) in constructed wetlands (CWs), removal rate constants of FC (kFC) were studied at various flow velocities (u). Membrane filtration technique was used during analysis. Values of kFC were determined using Reed's equation of pathogen removal; the results were compared with the plug flow equation. According to Reed's equation, kFC values ranged from 1.6 day−1 at a velocity of 4 m/day to 34.5 day−1 at a velocity of 42.9 m/day. The removal rates correlated positively with flow velocity (r = 0.84, p < 0.05). On assuming a plug flow equation, removal rates constants ranged from 0.77 to 11.69 day−1; a more positive correlation (r = 0.93, p < 0.05) was observed. Optimum removal rate constants were observed for the velocity ranging 36 to 43 m/day. Generally, the increase of flow velocity improved FC removal rate constants: implying that pathogen removals are influenced by diffusion of the microorganisms into the biofilms on CW media. The velocity dependent approach together with the plug flow equation is therefore proposed for incorporation in the design of CW in a tropical climate where temperature variations are minor.

Effect of diffusional mass transfer on the performance of horizontal subsurface flow constructed wetlands in tropical climate conditions

2011 ◽  
Vol 63 (12) ◽  
pp. 3039-3045 ◽  
Author(s):  
K. N. Njau ◽  
L. Gastory ◽  
B. Eshton ◽  
J. H. Y. Katima ◽  
R. J. A. Minja ◽  
...  
Keyword(s):  
Mass Transfer ◽  
Flow Velocity ◽  
Rate Constants ◽  
Removal Rate ◽  
Subsurface Flow ◽  
Plug Flow ◽  
Pollutant Removal ◽  
Velocity Correlation ◽  
Climate Conditions ◽  
Horizontal Subsurface Flow

The effect of mass transfer on the removal rate constants of BOD5, NH3, NO3 and TKN has been investigated in a Horizontal Subsurface Flow Constructed Wetland (HSSFCW) planted with Phragmites mauritianus. The plug flow model was assumed and the inlet and outlet concentrations were used to determine the observed removal rate constants. Mass transfer effects were studied by assessing the influence of interstitial velocity on pollutant removal rates in CW cells of different widths. The flow velocities varied between 3–46 m/d. Results indicate that the observed removal rate constants are highly influenced by the flow velocity. Correlation of dimensionless groups namely Reynolds Number (Re), Sherwood Number (Sh) and Schmidt Number (Sc) were applied and log–log plots of rate constants against velocity yielded straight lines with values β = 0.87 for BOD5, 1.88 for NH3, 1.20 for NO3 and 0.94 for TKN. The correlation matched the expected for packed beds although the constant β was higher than expected for low Reynolds numbers. These results indicate that the design values of rate constants used to size wetlands are influenced by flow velocity. This paper suggests the incorporation of mass transfer into CW design procedures in order to improve the performance of CW systems and reduce land requirements.

scholarly journals Direct Measurements of Removal Rates of CHF(X˜1A′(0,1,0)) by Simple Alkenes

1992 ◽  
Vol 12 (1-2) ◽  
pp. 43-52 ◽  
Author(s):  
José A. Fernández ◽  
Alfredo Ortiz de Zárate ◽  
María N. Sánchez Rayo ◽  
Fernando Castaño
Keyword(s):  
Energy Transfer ◽  
Ground State ◽  
Rate Constants ◽  
Removal Rate ◽  
Removal Rates ◽  
A Value ◽  
Vibrational Ground State ◽  
Direct Measurements ◽  
Intermolecular Energy ◽  
Intermolecular Energy Transfer

Direct measurements of the rate constants for collisional removal of CHF(X˜1A′(0,1,0)) by argon (Ar), ethylene (C2H4), propene (C3H6), 1-butene (1-C4H8), iso-butene (i-C4H8), 1,3-butadiene (C4H6), are reported. CHF(X˜1A′(0,1,0)) was prepared by IRMPD of precursor CH2F2. Fluence independence removal rate constants by Ar, ethylene and propene are: 0.0045, 2.70 and 2.46 × 10−11 cm3 molecule−1 s−1, faster than the rates for the vibrational ground state. 1,3-butadiene was measured at a fluence of 42Jcm−2, yielding a value of 0.81 × 10−11 cm3 molecule−1 s−1. Iso-butene has fluence dependence removal rates, given 1.28 and 0.92 × 10−11 cm3 molecule−1 s−1 for fluences of 50 and 32Jcm−2 respectively. For 1-butene a non-linear Stern-Volmer behaviour has been observed and attributed to fast resonant vibrational-to-vibrational (V-to-V) intermolecular energy transfer. The influence of this (V-to-V) energy transfer on the removal rates is discussed.

An Improved Membrane Filtration Method for Enumeration of Faecal Coliforms and E. Coli by a Fluorogenic β-Glucuronidase Assay

1993 ◽  
Vol 27 (3-4) ◽  
pp. 267-270 ◽  
Author(s):  
M. T. Augoustinos ◽  
N. A. Grabow ◽  
B. Genthe ◽  
R. Kfir
Keyword(s):  
Escherichia Coli ◽  
Water Samples ◽  
Membrane Filtration ◽  
Faecal Coliforms ◽  
Environmental Waters ◽  
Filtration Method ◽  
E Coli ◽  
Wide Range ◽  
Pure Cultures ◽  
Glucuronidase Assay

A fluorogenic β-glucuronidase assay comprising membrane filtration followed by selective enumeration on m-FC agar at 44.5°C and further confirmation using tlie 4-metliylumbelliferyl-β-D-glucuronide (MUG) containing medium was evaluated for the detection of Escherichia coli in water. A total of 200 typical blue and non-typical blue colonies were isolated from sea and fresh water samples using initial selective enumeration on m-FC agar. Pure cultures of the selected colonies were further tested using the MUG assay and identified using the API 20E method. Of the colonies tested which were shown to be positive using the MUG assay 99.4% were Escherichia coli. The results of this study indicate the combination of the m-FC method followed by the MUG assay to be highly efficient for the selection and confirmation of E. coli from a wide range of environmental waters.

Analysis of organic removal rates in the aerated submerged fixed film process

1998 ◽  
Vol 38 (8-9) ◽  
pp. 213-221 ◽  
Author(s):  
Mohamed F. Hamoda ◽  
Ibrahim A. Al-Ghusain
Keyword(s):  
Pilot Plant ◽  
Removal Rate ◽  
Domestic Wastewater ◽  
Removal Rates ◽  
Hydraulic Loading ◽  
Organic Removal ◽  
Wide Range ◽  
Fixed Film ◽  
Cod Removal Rate ◽  
And Performance

Performance data from a pilot-plant employing the four-stage aerated submerged fixed film (ASFF) process treating domestic wastewater were analyzed to examine the organic removal rates. The process has shown high BOD removal efficiencies (> 90%) over a wide range of hydraulic loading rates (0.04 to 0.68 m3/m2·d). It could also cope with high hydraulic and organic loadings with minimal loss in efficiency due to the large amount of immobilized biomass attained. The organic (BOD and COD) removal rate was influenced by the hydraulic loadings applied, but organic removal rates of up to 104 kg BOD/ m2·d were obtained at a hydraulic loading rate of 0.68 m3/m2·d. A Semi-empirical model for the bio-oxidation of organics in the ASFF process has been formulated and rate constants were calculated based on statistical analysis of pilot-plant data. The relationships obtained are very useful for analyzing the design and performance of the ASFF process and a variety of attached growth processes.

The comparison of trichloroethylene removal rates by methane- and aromatic-utilizing microorganisms

1998 ◽  
Vol 38 (7) ◽  
pp. 19-24 ◽  
Author(s):  
C.-J. Lu ◽  
C. M. Lee ◽  
M.-S. Chung
Keyword(s):  
Cell Concentration ◽  
Removal Rate ◽  
Carbon Sources ◽  
Batch Reactors ◽  
Initial Cell Concentration ◽  
Removal Rates ◽  
Initial Cell ◽  
Toluene Concentration ◽  
Cell Source ◽  
Removal Efficiencies

The comparison of TCE cometabolic removal by methane, toluene, and phenol utilizers was conducted with a series of batch reactors. Methane, toluene, or phenol enriched microorganisms were used as cell source. The initial cell concentration was about 107 cfu/mL. Methane, toluene, and phenol could be readily biodegraded resulting in the cometabolic removal of TCE. Among the three primary carbon sources studied, the presence of phenol provided the best cometabolic removal of TCE. When the concentration of carbon source was 3 mg-C/L, the initial TCE removal rates initiated by methane, toluene, and phenol utilizers were 1.5, 30, and 100 μg/L-hr, respectively. During the incubation period of 80 hours, TCE removal efficiencies were 26% and 96% with the presence of methane and toluene, respectively. However, it was 100% within 20 hours with the presence of phenol. For phenol utilizers, the initial TCE removal rates were about the same, when the phenol concentrations were 1.35, 2.7, and 4.5 mg/L. However, TCE removal was not proportional to the concentrations of phenol. TCE removal was hindered when the phenol concentration was higher than 4.5 mg/L because of the rapid depletion of dissolved oxygen. The presence of toluene also initiated cometabolic removal of TCE. The presence of toluene at 3 and 5 mg/L resulted in similar TCE removal. The initial TCE removal rate was about 95 μg/L-hr at toluene concentrations of 3 and 5 mg/L compared to 20 μg/L-hr at toluene concentration of 1 mg/L.

Relations between carbon removal rates, biofilm size and density of a novel anaerobic reactor: the inverse turbulent bed

2000 ◽  
Vol 41 (4-5) ◽  
pp. 253-260 ◽  
Author(s):  
P. Buffière ◽  
R. Moletta
Keyword(s):  
Removal Rate ◽  
Removal Rates ◽  
Carbon Removal ◽  
Biofilm Growth ◽  
Loading Rates ◽  
Biomass Activity ◽  
High Turbulence ◽  
The One ◽  
High Level ◽  
Very High

An anaerobic inverse turbulent bed, in which the biogas only ensures fluidisation of floating carrier particles, was investigated for carbon removal kinetics and for biofilm growth and detachment. The range of operation of the reactor was kept within 5 and 30 kgCOD· m−3· d−1, with Hydraulic Retention Times between 0.28 and 1 day. The carbon removal efficiency remained between 70 and 85%. Biofilm size were rather low (between 5 and 30 μm) while biofilm density reached very high values (over 80 kgVS· m−3). The biofilm size and density varied with increasing carbon removal rates with opposite trends; as biofilm size increases, its density decreases. On the one hand, biomass activity within the reactor was kept at a high level, (between 0.23 and 0.75 kgTOC· kgVS· d−1, i.e. between 0.6 and 1.85 kgCOD·kgVS · d−1).This result indicates that high turbulence and shear may favour growth of thin, dense and active biofilms. It is thus an interesting tool for biomass control. On the other hand, volatile solid detachment increases quasi linearly with carbon removal rate and the total amount of solid in the reactor levels off at high OLR. This means that detachment could be a limit of the process at higher organic loading rates.

Singlet Methylene Removal Rate Constants from the (0,1,0) Vibrational Level: Enhancement via Complex-Mediated Vibrational Relaxation

2001 ◽  
Vol 215 (6) ◽  
Author(s):  
M.A. Buntine ◽  
G.J. Gutsche ◽  
W.S. Staker ◽  
M.W. Heaven ◽  
K.D. King ◽  
...  
Keyword(s):  
Vibrational Level ◽  
Rate Constants ◽  
Vibrational Relaxation ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Removal Rate ◽  
Laser Flash ◽  
Laser Absorption ◽  
Photolysis Laser ◽  
Singlet Methylene

The technique of laser flash photolysis/laser absorption has been used to obtain absolute removal rate constants for singlet methylene,

scholarly journals Enhanced Wastewater Treatment by Immobilized Enzymes

2021 ◽  
Author(s):  
Jakub Zdarta ◽  
Katarzyna Jankowska ◽  
Karolina Bachosz ◽  
Oliwia Degórska ◽  
Karolina Kaźmierczak ◽  
...  
Keyword(s):  
Wastewater Treatment ◽  
Process Optimization ◽  
Organic Pollutants ◽  
Large Scale ◽  
Removal Rate ◽  
Immobilized Enzymes ◽  
Future Research ◽  
Process Conditions ◽  
Removal Rates ◽  
Catalytic Cycles

Abstract Purpose of Review In the presented review, we have summarized recent achievements on the use of immobilized oxidoreductases for biodegradation of hazardous organic pollutants including mainly dyes, pharmaceuticals, phenols, and bisphenols. In order to facilitate process optimization and achievement of high removal rates, effect of various process conditions on biodegradation has been highlighted and discussed. Recent Findings Current reports clearly show that immobilized oxidoreductases are capable of efficient conversion of organic pollutants, usually reaching over 90% of removal rate. Further, immobilized enzymes showed great recyclability potential, allowing their reuse in numerous of catalytic cycles. Summary Collected data clearly indicates immobilized oxidoreductases as an efficient biocatalytic tools for removal of hazardous phenolic compounds, making them a promising option for future water purification. Data shows, however, that both immobilization and biodegradation conditions affect conversion efficiency; therefore, process optimization is required to achieve high removal rates. Nevertheless, we have demonstrated future trends and highlighted several issues that have to be solved in the near-future research, to facilitate large-scale application of the immobilized oxidoreductases in wastewater treatment.

Lubricant Removal, Degradation, and Recovery on Particulate Magnetic Recording Media

1992 ◽  
Vol 114 (1) ◽  
pp. 61-67 ◽  
Author(s):  
V. J. Novotny ◽  
T. E. Karis ◽  
N. W. Johnson
Keyword(s):  
Bulk Viscosity ◽  
Magnetic Recording ◽  
Photoelectron Spectroscopy ◽  
Removal Rate ◽  
Lateral Diffusion ◽  
Recording Media ◽  
Magnetic Recording Media ◽  
Removal Rates ◽  
Linear Chains ◽  
Mechanical Durability

Lubrication of particulate magnetic recording media improves their mechanical durability in sliding and flying by several orders of magnitude compared with unlubricated media. Lubricant removal, degradation, and recovery were studied using microslit scanning Fourier transform infrared spectroscopy and microspot scanning X-ray photoelectron spectroscopy. These techniques measure the total and surface lubricant amounts in the porous film, respectively. Lubricant dynamics were compared for two physisorbed polyperfluoroalkylether lubricants of similar molecular weight but different molecular structure—Y with a CF3 side group and Z with linear chains. The bulk viscosity of Y was about ten times higher than the viscosity of Z. In sliding, the lubricant removal rate of Y was significantly higher than that of Z while in flying the removal rates were reversed. Removal rates in sliding were orders of magnitude higher than those in flying. Effective lateral diffusion coefficients estimated from the rate of lubricant reflow back to the depleted tracks were close to inversely proportional to the bulk viscosity. During sliding and flying both lubricants degraded as evidenced by chemically altered lubricant detected on the surfaces after dissolution of undegraded lubricant.

Mechanisms of High Efficiency and Stabilization of Baffled Constructed Wetland in Treatment of Domestic Sewage

2013 ◽  
Vol 295-298 ◽  
pp. 1057-1061 ◽  
Author(s):  
Chang Bing Ye ◽  
Zhi Ming Zhou ◽  
Ke Zhao ◽  
Qin Liu
Keyword(s):  
Constructed Wetland ◽  
Removal Rate ◽  
Short Circuit ◽  
Domestic Sewage ◽  
Wetland Plants ◽  
Stable Operation ◽  
Removal Rates ◽  
Operational Life ◽  
High Efficient ◽  
Hydraulic Load

To solve the problem of short-circuit of individual current constructed wetland, a baffled constructed wetland was designed and applied to treat domestic sewage by our research group. The wetland plants were composed of Eichhormia crassipes, Oenanthe javanica, Cyperusalternifolius, Phragmites communis and Aquatic. The results of 18 month indicated that the optimal hydraulic load of baffled constructed wetland was 2.0~2.2 m3/(m2•d). At the hydraulic load of 2.0m3/(m2•d), the COD, TN and TP removal rates of baffled constructed wetland could be over 76.40%, 76.12%, 65.37%, respectively, at 24°C. When the temperature decreased to 12°C, the COD, TN, TP removal rates of system decreased to 67.56%、62.75% and 61.33%, respectively; The SS removal rate of the first 6 compartments was about 79.5% and that of system could maintain 87.18% during the operation of system. Based on the results of trial, the mechanisms of extending the baffled constructed wetland's operational life was owed to high efficient SS removal rate of the first 6 compartments which was used as constructed wetland and anaerobic baffled reactor (ABR). As a result, the long-term stable operation of system in treatment of domestic sewage was explained with extending about 5 times service life than that of individual current constructed wetland. The mechanisms of higher efficiency of baffled constructed wetland in treatment of domestic sewage were owed to the longer flow line of system and the up-down flow of domestic sewage makes pollutant more intimate contact with roots of wetland plants.

Sign in / Sign up

Export Citation Format

Share Document