Contaminant Diffusion, Solubility, and Material Property Differences between HDPE and PEX Potable Water Pipes

The objectives of this work were to identify differences between the composition, bulk properties, contaminant diffusivity and solubility for new high-density polyethylene (HDPE) pipe and crosslinked polyethylene (PEX) pipe, as well as determine which contaminant and polymer properties are useful for predicting contaminant fate in water pipe. Variations in PE pipe density (0.9371–0.9547?g/cm3), crystallinity (69–72%), crosslinking (60 and 76%), and oxidative induction time (33 to >295?min.) were detected. While numerically these differences seem minor, results show that slight material differences have a notable effect on contaminant diffusivity and solubility. Nonpolar contaminant diffusivity and solubility were best predicted by bulk density. Polar contaminants were more soluble and diffused faster through PEX than HDPE pipes because PEX pipes contained a greater amount of oxygen. For all materials, dipole moment and Log Kow were good predictors of contaminant fate and molecular volume was only useful for predicting diffusivity and solubility values for haloalkane and nonpolar aromatic contaminants.     

High-Density Polyethylene Membrane Containing Fe0 as a Contaminant Barrier

To improve the performance of polymer-based containment barriers with respect to the breakthrough of chlorinated solvents, a high-density polyethylene (HDPE) membrane containing zero-valent iron (Fe0) nanoparticles was developed as a reactive barrier. The performance of the reactive membrane was evaluated by challenging it with carbon tetrachloride in a diaphragm cell apparatus. In a Fe0/HDPE system, reaction between carbon tetrachloride and Fe0 did not occur due to a lack of water in the polymer matrix. A glycerol-modified Fe0/HDPE membrane successfully increased the lag time before breakthrough by 13–16 fold compared to HDPE alone. Calculations estimate that only 2.5–3.0% of the Fe0 initially present in the membrane reacted before breakthrough of carbon tetrachloride. Extrapolations of these results to practical situations with larger membrane thicknesses and lower contaminant concentrations predict lag times on the order of years.     

Permeation of BTEX through Unaged and Aged HDPE Geomembranes

The effects of aging of high-density polyethylene (HDPE) geomembranes on the diffusion and partitioning of a group of volatile organic compounds (VOCs) are examined. Two different 1.5?mm thick HDPE geomembranes were aged in the laboratory at 85°C by immersing in a synthetic leachate for up to 32?months. The results of partitioning and diffusion tests performed at room temperature on both unaged and aged geomembranes using a dilute aqueous solution containing four VOCs commonly found in landfill leachates [benzene, toluene, ethylbenzene, and xylenes (BTEX)] are reported. The diffusion and partitioning coefficients decreased with increased aging. The calculated permeation coefficients decreased by 36–62% after aging the geomembrane for about 10–32?months. This decrease in diffusion, partitioning, and permeation coefficients is related to the increase in geomembrane crystallinity during aging. A relationship between partitioning, diffusion, and permeation coefficients with the geomembrane crystallinity is established and could potentially be used to evaluate the migration of VOCs through HDPE geomembranes. Aging of HDPE geomembrane did not increase diffusive transport of organic contaminants.     

Evaluation of High-Density Polyethylene Pipe Installed Using Horizontal Directional Drilling

This paper presents the results of field installations of high-density polyethylene (HDPE) using the horizontal directional drilling process. One each of 114 mm (4 in.) diameter standard dimension ratio (SDR) 17 HDPE pipe, 219 mm (8 in.) diameter SDR 17 HDPE pipe, and 324 mm (12 in.) diameter SDR 17 HDPE pipe were installed in a cohesionless soil medium. Various testing parameters were captured during the pullback phase of these three installations. These testing parameters consisted of utilizing pressure transducers to capture the pullback and rotational pressures on the drilling rig, installing linear potentiometers inside the HDPE pipe to measure the axial strain on the pipe, and applying an external load cell to quantify the loading on the pipe during the pullback phase. Comparisons of the pullback and rotational pressure on the drilling rig, loading on the HDPE pipe, and average and maximum strain experienced by the HDPE pipe are presented with respect to the installed pipe diameter.     

Estimation of Mass Transport Parameters of Organic Compounds through High Density Polyethylene Geomembranes Using a Modifield Double-Compartment Apparatus

A modified double-compartment apparatus (MDCA) is used to estimate mass transport parameters of organic compounds through high density polyethylene (HDPE) geomembranes and to investigate the effects of aging and external tension of HDPE geomembranes on the mass transport of organic compounds. A developed one-dimensional partition–diffusion mass transport model successfully explains the mass transport of the organic compounds through the HDPE geomembranes in a dilute aqueous solution–geomembrane system. Similar to batch immersion tests, the HDPE–water partition coefficient (KHDPE–W) values of organic compounds are found to have close relationships with the octanol–water partition coefficient and the aqueous solubility; furthermore, the diffusion coefficient (D) values decrease with the increase of their molecular diameter. For HDPE geomembranes served in the landfill liner for 5 years and stretched by 8% of their initial length, KHDPE–W values for organic compounds increase by 5–58%, D values for organic compounds increase by 10–86%, and breakthrough times are faster, indicating more amounts of organic compounds may break through the HDPE geomembrane in fields than expected. The mass transport parameters from MDCA tests could be used with those from batch immersion tests interchangeably after mass loss and immobilization of organic compounds in MDCA tests are considered.     

钢带增强聚乙烯螺旋波纹排水管的设计与应用

钢带增强聚乙烯螺旋波纹管作为一种新型的排水管道,具有良好的使用性能,但在设计、孑包工上有着不同于其它排水管材的特殊要求。本文主要介绍钢带增强聚乙烯螺旋波纹排水管道的特性与设计要点和施工注意事项。     

Design Guidelines for Polyethylene Pipe Interface Shear Resistance

Polyethylene pipes are commonly used in pipeline systems. Current methods used to determine the pipe pullout capacity do not consider the effects of diameter changes and cyclic movements that the pipelines may experience. Laboratory tests were performed to study the interface shearing resistance of polyethylene pipes under varying conditions. The tests were performed in a temperature-controlled room, where properties were investigated for thermal variations expected in the field. Two types of tests were performed: pull/push tests and cyclic tests. Test results indicated that reductions in pipe diameter affect the interface shear resistance that develops between the pipe and soil. As the pipe diameter gets smaller, the normal contact stresses at the interface decreases, causing a reduction in the interface shearing resistance directly proportional to the normal stress changes. Cyclic pipe movements also cause significant reduction in pipe pullout resistance. The test results indicated that the polyethylene pipe interface shear resistance can be significantly lower than the one determined using the current methods. This paper presents the test results, findings, and design recommendations for the pullout resistance of buried polyethylene pipes.     

Full-Scale Field Tests on Flexible Pipes under Live Load Application

This paper describes the procedure and results of the field tests on high-density polyethylene (HDPE), PVC, and metal large diameter pipes subjected to a highway design truck loading. Numerical simulations using finite element method are performed to determine pipe-soil system response under live load application. Comparisons of field test data with the predicted responses are made for soil pressures around and above the pipes, deformed cross-sectional pipe profiles, and pipe deflections. The field test results indicated that the buried flexible pipes, embedded with highly compacted graded sand with silt, demonstrated good performance without exhibiting any visible joint opening or structural distress. Under shallow burial conditions, the AASHTO specified deflection limit of 5% is found to be adequate for installation of the flexible pipes during the construction phase, and a vertical deflection limit of 2% is suggested for HDPE pipes based on the truck load response and repeated loading effect.     

Microscopic Visualization Technique to Predict the Permeation of Organic Solvents through PVC Pipes in Water Distribution Systems

Organic contaminants may permeate through plastic pipes in water distribution systems and adversely affect the quality of drinking water. In this study, we developed a microscopic visualization technique to investigate the permeation of common organic contaminants (benzene, toluene, ethylbenzene, xylene, and trichloroethene) through polyvinyl chloride (PVC) pipes. By observing the propagation of organic moving fronts in the pipe materials with a light microscope, the technique was able to predict the permeation breakthrough times through PVC pipes that were determined in the pipe-bottle test. The advance of an organic moving front was found to be linearly dependent on the square-root of time and the propagation rate increased with an increase in the external organic chemical activity. Permeation of organic mixtures into PVC pipes was found to be additive in proportion to the permeation rates and volume percents of each component. In combination with a 2-year pipe-bottle test for PVC pipes exposed to premium gasoline, mathematical extrapolations based on the microscopic visualization tests predicted that PVC pipe are likely to resist permeation by commercial gasoline for the service life of the pipe.     

Estimation of Diffusion Coefficients and Solubilities for Organic Solvents Permeation through High-Density Polyethylene Geomembrane

Experiments on the permeation of several chlorinated and aromatic hydrocarbons through high-density polyethylene (HDPE) geomembranes were conducted using the ASTM F-739 standard test method. The diffusion coefficients were estimated by a one-dimensional diffusion equation based on Fick’s second law, and the solubilities of the solvents in HDPE were determined by the steady state permeation rates. The one-dimensional transient model was able to simulate the permeation concentrations and implied that equilibrium partition between organic solvent and HDPE geomembrane was not achieved during the initial permeation. The solubilities of organic solvents in the HDPE geomembranes obtained by immersion tests or weight gain methods of permeation experiments were not an appropriate boundary condition for the model simulation of permeation. It was found that the diffusion coefficients and solubilities of organic solvents correlated well with their molecular weights and dipole moment, respectively. The present work provides information on the extent of organic compounds permeations through HDPE geomembranes as applied in hazardous waste landfills.     

Effect of surface modification of high-density polyethylene by direct current and radio frequency glow discharge on wetting and adhesion characteristics

The present investigation aims to optimize the process parameters of Direct Current (DC) and Radio Frequency (RF) glow discharge treatment through air in terms of discharge power and time of exposure for the surface modification of high-density polyethylene (HDPE) sheet, for attaining best adhesive joint of the polymer to mild steel. In order to estimate the extent of surface modification, the surface energies of the polymer surfaces exposed to glow discharge have been determined by measuring contact angles using two standard test liquids of known surface energies. It is observed that at a given power level of DC glow discharge, surface energy and its polar component increase with increasing exposure time, attaining a maximum and then decreasing. In the case of RF glow discharge, surface energy and its polar component increase with increasing exposure time and then saturate. Surface modification by DC glow discharge increases the surface energy of HDPE relatively more at a lower power compared to that observed for RF glow discharge. The dispersion component of surface energy remains almost unaffected. The surfaces have also been studied by electron spectroscopy for chemical analysis (ESCA) and energy-dispersive spectra (EDS). A significant oxygen peak is observed for surface-modified polymer as detected by ESCA and EDS. Lap shear tensile test of an adhesive (Araldite AY 105) joint of HDPE with mild steel has been carried out in optimizing the parameters of DC and RF glow discharge for maximum joint strength. When HDPE is exposed to DC glow discharge, improvement of adhesive joint strength of HDPE to mild steel is found to be by a factor more than 7. On the other hand, when HDPE is exposed to RF glow discharge, results in improvement of adhesive joint strength of HDPE to mild steel by a factor nearer to 7 are found. Thus, DC glow discharge is more capable for increasing wetting and adhesion characteristics of the polymer.     

Numerical Examination of a Method for Reducing the Temperature of Municipal Solid Waste Landfill Liners

A method to control the increase in landfill liner temperature due to the heat generated by the waste is examined. The design involves installation of an array of cooling pipes beneath the waste. The feasibility of this system for cooling the liner was examined by performing a series of analyses for conditions based on the Tokyo Port Landfill. The results suggest that the introduction of a cooling system can substantially reduce liner temperature and consequently significantly increase the service life of a high-density polyethylene (HDPE) geomembrane liner in an engineered barrier system. The effects of pipe layout, pipe spacing, and coolant flow rate are examined. It is shown that a periodic pipe layout is the most efficient. Liner temperature decreases with increased coolant transfer flow rate     

钛设备在水相悬浮法氯化聚乙烯工业中的应用

介绍了氯化聚乙烯的性能和用途,当前水相悬浮法是应用最多的氯化聚乙烯生产方法,结合其工艺过程,水相悬浮法氯化聚乙烯工业选用钛设备的必要性和依据,钛设备在使用中应注意的问题。     

Removal of Immiscible Contaminants from Sandy Soils Monitored by Means of Dielectric Measurements

The main objective of this paper is to explore the potential application of electromagnetic waves to evaluate the effect of contaminant removal in granular soils. Thus, various specimens of saturated silica sand were prepared using paraffin oil and lubricant oil as contaminants. Four flushing fluids were used to remove the contaminants from sand columns: Deionized water, water-detergent, water-detergent-alcohol solution, and water vapor. Dielectric permittivity was measured at different stages of the removal process at the frequency from 20?MHz?to?1.3?GHz. The measured permittivity was compared with that determined for clean and fully contaminated specimens. A theoretical mixture formula was calibrated and implemented to estimate the volume fraction of contaminant present in the pore fluid. It is concluded in this work that dielectric parameters reflect the contamination level of the soil for the nonpolar organic compounds used here. Measurement of permittivity allows us to determine that the inclusion of alcohol and detergent in the displacing fluid improved the removal efficiency. However, water vapor was the most efficient removal agent.     

Field Studies of Discoloration in Water Distribution Systems: Model Verification and Practical Implications

Discoloration in water distribution systems has been studied in partnership with a number of U.K. water companies by measuring the turbidity response to changes in hydraulic conditions induced by systematic flushing. The resulting data was used to verify a predictive empirical model and hence the underlying assumptions made in its development. Model simulations, made using previously established parameters defined solely by pipe diameter and pipe material, are presented alongside measured data to demonstrate this verification. The primary cause of discoloration observed is the mobilization of material from cohesive layers bonded to pipe walls. These layers demonstrate a profile of increasing shear strength with increasing degree of discoloration. Differences are demonstrated in the layer and ultimate shear strength characteristics of the discoloration layers formed in iron and plastic pipes, with a modeled shear stress of 1.2?N/m2 shown to exhaust material layers in plastic pipes. Based on the observed data it is theorized that accumulation of material to the pipe walls is primarily dependent on two mechanisms; ubiquitous background concentrations in the bulk water, and if present corrosion by-products from iron pipes and fittings. A consequence of this is that all pipes within a water distribution system are susceptible to the development of material layers. In the formulation of operation and maintenance strategies it is suggested that iron and plastic pipes should be treated differently to obtain optimum operational effectiveness and minimize discoloration risk.     

管线探测仪对测量供水管道漏损的作用

供水管道在供水过程中出现渗漏和破损,如何及时发现漏损的水量以减少供水的损失,减少漏失率,全功能管线探测仪在供水管道测漏上起了至关重要的作用。     

Comparison of Statistical Deterioration Models for Water Distribution Networks

The use of water main break history as a proxy for condition has become common practice because of the high costs associated with direct assessments. Statistical deterioration models predict future water main breaks on the basis of historical patterns. Many municipalities are beginning to understand the value of utilizing water pipe break histories to manage their noncritical distribution networks via deterioration models. This paper presents a generic IDEF0 process model for developing water main deterioration models. Two common statistical deterioration models for water pipes are compared: rate-of-failure models (ROF) and transition-state (TS) models. ROF models extrapolate the breakage rate for a particular cohort of pipes and do not differentiate between the times between successive failures. On the other hand, transition-state models attempt to model the time between successive failures for pipes. This paper presents a comparison and analysis of ROF models and transition-state models by using a single data set for cast- and ductile-iron pipes in the City of Hamilton, Ontario, Canada. The paper compares the models’ ability to support breakage forecasting, long-term strategic planning, and short-term tactical planning. Best practices for pipe segmentation in support of water main deterioration models are presented.     

Thermal Treatment of Polyethylene in System Containing Hydrogen Chloride

The pyrolysis of high-density polyethylene (HDPE), the principal component of plastics in municipal solid waste, was studied in the thermal gravimetric analysis reaction system containing hydrogen chloride (HCl) gas. The pyrolysis experiments were carried out over a range of room temperatures to 850 K. The results indicated that HCl retarded the pyrolytic reaction of HDPE at high HCl concentration CHCl range. The gas∕liquid products and solid residues were collected and analyzed by gas chromatography, mass spectrometer, and elemental analyzer. The distributions of gas∕liquid products and solid residues as well as the effects of HCl on the pyrolytic products were investigated. The results of this study are useful for the utilization of HDPE as an energy resource and determining the thermal degradation behavior of HDPE in an incinerator.     

Nucleotide sequence of an alternative glucoamylase-encoding gene (glaB) expressed in solid-state culture of Aspergillus oryzae

The potential health effects of environmental contaminants in traditional food has become a concern among northern communities because of the presence of environmental contaminants in the Arctic ecosystem. Exposure assessments are needed but they require comprehensive dietary information and contaminant data. Over the last 10 years, there has been considerable effort to monitor the level of contaminants in fish and wildlife collected from different regions in northern and Arctic Canada. The development of a database and its application for dietary contaminant exposure assessment are described. We conducted an extensive literature review on levels of environmental contaminants in northern and Arctic Canada. The ranges of levels of four contaminants of major concern (chlordane, mercury, polychlorinated biphenyls and toxaphene) in 81 species of marine mammals, terrestrial mammals, birds, fish and plants are summarized. These data represent 69% of the 117 species of fish, wildlife and plants mentioned in our dietary interviews conducted in the northern communities. A significant percentage of the foods had contaminant levels exceeding the guidelines used by Health Canada for market food consumed by the 'southern' populations. Mathematic modelling of the distributions of the data showed that contaminant levels in most food groups are log-normally distributed and have a typical coefficient of variation of about 100%. Examples are presented to demonstrate the use of the data for contaminant exposure assessment. Average contaminant exposure levels estimated using the database for two communities are comparable to those obtained previously using community specific data. With the current knowledge of environmental contaminant levels in the northern traditional food system, it may be feasible to conduct preliminary risk assessment of dietary exposure of environmental contaminants when some diet information for a community is available. Further sampling and analysis may be needed only for confirmation purposes.