Pond and wetland treatment

2003 ◽  
Vol 48 (5) ◽  
pp. 1-8 ◽  
Author(s):  
R.H. Kadlec
Keyword(s):  
Temperature Dependence ◽  
Rate Constants ◽  
Cost Effective ◽  
Fecal Coliforms ◽  
First Order ◽  
Loading Rates ◽  
Wetland Treatment ◽  
Long Term Performance ◽  
Term Performance

Wetlands are in use as adjuncts to wastewater treatment lagoons at many north temperate locations. Performance data for 21 systems show median removals of 67, 61, 61, 48 and 99.8% for TSS, BOD, NH4-N, TP and fecal coliforms, respectively. Hydraulic loading rates range from 0.14 to 55 cm/d, areas from 0.02 to 200 ha, and latitudes from 30 to 54°N. Calibrations of first order models with temperature dependence show that rate constants vary from seasonal dependence at low loadings to temperature dependence at high loadings for ammonia. Phosphorus rate constants display seasonal, not temperature effects. BOD and TSS are not affected by season. Wetland rate constants are larger than those for lagoons for all constituents. The optimal winter operating strategy, if hydraulics allow, is partial storage during frozen months, coupled with winter use of the wetlands. The use of FWS wetlands for polishing lagoon effluents is cost effective when land availability is not drastically constrained. Many systems have been in operation long enough to demonstrate sustainable long-term performance. Infiltration beds are potentially a valuable addition to ponds and wetlands.

The Importance of Variables and Parameters in Radiolytic Chemical Kinetics Modeling

1988 ◽  
Vol 127 ◽  
Author(s):  
M. G. Piepho ◽  
P. J. Turner ◽  
P. W. Reimus
Keyword(s):  
Chemical Kinetics ◽  
Rate Constants ◽  
Transient Species ◽  
Geologic Repository ◽  
Species Concentration ◽  
Waste Package ◽  
Long Term Performance ◽  
Term Performance ◽  
Over Time

ABSTRACTRadiolysis may significantly affect the long-term performance of nuclear waste packages in a geologic repository. Radiolysis of available moisture and air in an unsaturated or saturated environment will create transient species that can significantly change the pH and/or Eh of the available moisture. These changes can influence rates of containment corrosion, waste form dissolution, and radionuclide solubilities and transport.Many of the pertinent radiochemical reactions are not completely understood, and most of the associated rate constants are poorly characterized. To help identify the important radiochemical reactions, rate constants, species, and environmental conditions, an importance theory code, SWATS (Sensitivity With Adjoint Theory-Sparse version)-LOOPCHEM, has been developed for the radiolytic chemical kinetics model in the radiolysis code LOOPCHEM. The LOOPCHEM code calculates the concentrations of various species in a radiolytic field over time. The SWATS-LOOPCHEM code efficiently calculates: 1) the importance (relative to a defined response of interest) of each species concentration over time, 2) the sensitivity of each parameter of interest, and 3) the importance of each equation in the radiolysis model. The calculated results will be used to guide future experimental and modeling work for determining the importance of radiolysis on waste package performance. A demonstration (the importance of selected concentrations and the sensitivities of selected parameters) of the SWATS-LOOPCHEM code is provided for illustrative purposes, and no attempt is made at this time to interpret the results for waste package performance assessment purposes.

Rail Highway Grade Crossing Roughness Quantitative Measurement Using 3D Technology

2014 ◽  
Author(s):  
Teng (Alex) Wang ◽  
Reginald R. Souleyrette ◽  
Daniel Lau ◽  
Peng Xu
Keyword(s):  
Quantitative Method ◽  
Cost Effective ◽  
Actual Condition ◽  
Subjective Rating ◽  
3D Surface ◽  
Grade Crossing ◽  
Long Term Performance ◽  
Term Performance

Quality of surface is an important aspect affecting both the safety and the performance of at-grade rail-highway crossings. Roughness may increase the risk of crashes for both trains and automobiles. Varying grades in crossing profiles increase the likelihood of high-centered crossing collisions between train and truck [1]. The US DOT Railroad Highway Grade Crossing Handbook [2] suggests that rough surfaces could distract a driver’s attention from oncoming trains and that the unevenness of the crossing could result in a driver losing control of their vehicle resulting in a crash. No quantitative method currently exists to quickly and economically assess the condition of rail crossings in order to evaluate the long term performance of crossings and set a quantitative trigger for their rehabilitation. The conventional method to measure the surface of quality of crossings is based on expert judgment, whereby crossing surfaces are classified as poor, fair or good after an inspector visits and drives over the crossing. However, actual condition of the crossing could be different from the subjective rating. Poor condition rating crossings may not always present the most cost-effective locations for preventive maintenance to lower overall life-cycle costs. Conventional ratings may derive from driving a passenger car of pickup once over the crossing. Effects of various speed, on various vehicles (suspension), and at various places (laterally) cannot be determined or even estimated except at the smoothest of crossings. A quantifiable and extensible procedure is desired. With rapid advances in computer science, 3D sensing and imaging technologies, it seems logical that a cost-effective quantitative method could be developed to determine the need to rehabilitate rail crossings and assess long term performance. Fundamental to the quantification of crossing condition is the acquisition of an accurate 3D surface model of the crossing in its present state. This paper reports on the development of an accurate, low cost and readily deployable sensor capable of rapid collection of this 3D surface. The research is seen as a first step towards automating the crossing inspection process, ultimately leading to the quantification and estimation of future performance of rail crossing.

Experimental study on the performance of light and dense backfills

2011 ◽  
Vol 48 (2) ◽  
pp. 214-225 ◽  
Author(s):  
Sumi Siddiqua ◽  
James Blatz ◽  
Greg Siemens
Keyword(s):  
Mechanical Behaviour ◽  
Cost Effective ◽  
Strain Behaviour ◽  
Triaxial Cell ◽  
Important Approach ◽  
Shear Characteristics ◽  
Long Term Performance ◽  
Term Performance ◽  
Sealing Materials

Numerical modeling is a cost-effective and important approach to examine the long-term performance of engineered materials. However, to identify the appropriate constitutive model for a particular material it is necessary to measure physical properties in a laboratory. Laboratory experiments provide the data from which the input parameters for the selected model can be interpreted. This paper studies the mechanical behaviour of two clay-based sealing materials — light backfill and dense backfill — recommended for use in disposal of nuclear waste in a proposed Canadian repository. Test specimens of light and dense backfills were saturated in a triaxial cell and then subjected to specified isotropic and shearing stress paths to measure consolidation and shear characteristics. The triaxial results are interpreted in a critical state context. The light backfill results suggest that it has similar stress–strain behaviour to a bentonite–sand buffer, which has a similar composition, but different preparation procedures and design requirements. Results from testing of dense backfill indicate that it is a much stiffer and stronger material than light backfill. Dense backfill is expected to provide mechanical support to the used-fuel container and other sealing components of the Canadian repository, and the mechanical behaviour of dense backfill satisfies these requirements.

Long-term performance of aerated and planted constructed wetland treatment on domestic wastewater

2017 ◽  
Vol 64 ◽  
pp. 64-71
Author(s):  
Jingjing Lv ◽  
Li’an Hou ◽  
Lieyu Zhang ◽  
Beidou Xi ◽  
Xuhui Mao ◽  
...  
Keyword(s):  
Constructed Wetland ◽  
Domestic Wastewater ◽  
Wetland Treatment ◽  
Long Term Performance ◽  
Term Performance

scholarly journals Porous Fe0/C ceramsites for removal of aqueous Pb(ii) ions: equilibrium, long-term performance and mechanism studies

RSC Advances ◽  
2018 ◽  
Vol 8 (45) ◽  
pp. 25445-25455 ◽  
Author(s):  
Pingfeng Fu ◽  
Xiaofeng Lin ◽  
Zihao Chen
Keyword(s):  
Cost Effective ◽  
Paper Mill ◽  
Paper Mill Sludge ◽  
Long Term Performance ◽  
Term Performance ◽  
Performance And Mechanism

Cost-effective Fe0/C microelectrolysis ceramsites were fabricated from magnetite, coal and paper mill sludge with high long-term performance in the removal of Pb(ii) ions.

Performance-based specifications for pavements

1991 ◽  
Vol 18 (6) ◽  
pp. 1054-1061 ◽  
Author(s):  
P. Kuzyk ◽  
R. C. G. Haas ◽  
R. W. Cockfield
Keyword(s):  
Risk Factors ◽  
Key Words ◽  
Current Practice ◽  
Cost Effective ◽  
Pavement Performance ◽  
Substantial Portion ◽  
Actual Performance ◽  
Long Term Performance ◽  
Term Performance

Pavements represent a very substantial portion of the public's investment in infrastructure. It is essential that this investment be preserved through cost-effective planning, design, and maintenance. One way of achieving this is through the use of long-term performance-based specifications. This paper first describes the current practice for pavement specification. For the most part, these specifications are "recipe" orientated. Very specific requirements are set for procedures, such as compaction, or as constructed properties such as density. With the proposed system, the contractor would be required to warranty the actual performance of the pavement over an extended term. The paper describes the overall scope of the system, its key elements and advantages, and the major risk factors. As well, the measures that can be used to characterize performance and a model for estimating performance are identified. A stochastic formulation of the model is used to present a method of determining the risk to the contractor based on a design example. Finally, the paper explores some of the concerns associated with the implementation of the system and how these concerns might be addressed. Key words: long-term warranties, pavement contracting, pavement performance.

scholarly journals Study on the temperature dependence of gas permeation and adsorption behavior of the vacuum insulation panel with getter materials

2020 ◽  
Vol 172 ◽  
pp. 21001 ◽  
Author(s):  
Hideya Yamamoto ◽  
Daisuke Ogura
Keyword(s):  
Thermal Conductivity ◽  
Temperature Dependence ◽  
Pressure Sensor ◽  
Glass Wool ◽  
Adsorption Behavior ◽  
Vacuum Insulation ◽  
Long Term Performance ◽  
Term Performance ◽  
Vacuum Insulation Panel

Vacuum insulation panel (VIP) is a high-performance heat insulation material that has contributed to the energy efficiency of refrigerators, vending machines, and cooler boxes. Glass wool or fumed silica covered by a laminated film are the core materials of VIP; by evacuating air inside, it is possible to reduce the gas thermal conductivity to be close to 0 and exhibit high thermal performance. In recent years, the research on long-term performance prediction has been conducted for use in building insulation. Specifically, various getter materials have been developed to improve the long-term performance of glass wool VIP. However, there are no studies that clearly show the adsorption behavior or temperature dependence inside VIP with getter materials. We measured the adsorption temperature dependence of two types of getters using the constant volume method and then observed the adsorption behavior inside VIP using VIP equipped with a micro pressure sensor. Regarding the internal pressure of VIPs equipped with the micro pressure sensor, the pressure fluctuation derived from the adsorbent was confirmed by the temperature change, and it was confirmed that the thermal conductivity changed accordingly. If the internal temperature of VIP increases, gases may be released from the getter. Therefore, in the building environment, it is necessary to select a getter that is suitable for the usage environment and to use an appropriate amount of getter.

Fine Particle Mass Monitoring with Low-Cost Sensors: Corrections and Long-Term Performance Evaluation

2019 ◽  
Author(s):  
Carl Malings ◽  
Rebecca Tanzer ◽  
Aliaksei Hauryliuk ◽  
Provat K. Saha ◽  
Allen L. Robinson ◽  
...  
Keyword(s):  
Performance Evaluation ◽  
Fine Particle ◽  
Low Cost ◽  
Particle Mass ◽  
Long Term Performance ◽  
Term Performance
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