Evaluation of the effectiveness of a cover with capillary barrier effect to control percolation into a waste disposal facility

Abstract: The goal of an instrumented experimental plot constructed on the Saint-Tite-des-Caps landfill site was to evaluate the field behaviour and the performance of a cover with capillary barrier effect (CCBE) to control water percolation. The CCBE consists of a layer of deinking byproducts (DBP) on top of layer of sand overlying a gravel layer. The DBP layer acts as a hydraulic barrier to control the rate of seepage that can reach the top of the capillary barrier. Analysis of the field data shows that the hydraulic barrier consisting of DBP remained nearly saturated and controlled percolation to the desired level. In addition, for the first year of monitoring, the diversion length determined from field data was very similar to that estimated by the analytical solution that was used for the design of the experimental plot. Afterwards, the diversion length increased due to a decrease in the rate of seepage caused by settlement of the hydraulic barrier, which caused a decrease in its saturated hydraulic conductivity. At all times, the flows that reached the gravel layer at the toe of the experimental CCBE were, for all practical purposes, lower than the maximum seepage rates required by the most restrictive landfill regulations

Predicting the diversion length of capillary barriers using steady state and transient state numerical modeling: Case study of the Saint-Tite-des-Caps landfill final cover

Abstract: Covers with capillary barrier effect (CCBE) have already been proposed to meet regulatory requirements for landfill final covers. Modeling of CCBE may be a relatively complex and time consuming task. Simpler, albeit conservative, design tools – such as steady state numerical analyses – can be, in certain cases, justifiable and have a positive impact in the practice. In this study, we performed numerical simulations of the experimental CCBE constructed on the Saint-Tite-des-Caps landfill (Quebec). The CCBE consists of a capillary barrier, composed of sand and gravel, on top of which a layer of deinking by-products (DBP) was installed as a protective layer (also to control seepage). The addition of a protective layer over the infiltration control layer (such as a capillary barrier) is required nearly everywhere. In many European countries, such as Germany and the Netherlands, a thick “recultivation” layer is required. The results of numerical simulations were compared to the in situ behaviour of the Saint-Tite CCBE as well as to analytical solutions. The effectiveness of the capillary barrier was assessed by quantifying the diversion length (DL), which reflects the lateral drainage capacity of the CCBE, i.e. the capacity to drain water laterally. The latter, if collected, prevents seepage into the waste mass. This study shows that, when the seepage rate reaching the top layer of the capillary barrier is controlled, it is possible to predict the worst case scenario in terms of seepage (and therefore predict the shortest DL) using steady state numerical simulations. These simpler-to-perform numerical simulations could be adopted, at least in a pre-feasibility study for cases with a similar profile as the one at the Saint-Tite-des-Caps experimental CCBE

Assessment of the design of an experimental cover with capillary barrier effect using 4 years of field data

Abstract: One important step in the design of inclined covers with capillary barrier effect (CCBE) is the determination of the water diversion length (DL). Numerical simulations can predict the DL more precisely than steady-state analytical solutions. Nevertheless, as simplified methods have always been part of engineering design, the application of analytical solutions with conservative boundary conditions, may allow engineers to make reasonable predictions, particularly during the pre-feasibility stage of a project. In this study, a CCBE was designed, constructed and instrumented at the Saint-Tite-des-Caps landfill, Quebec, Canada. This CCBE included a seepage control layer superimposing a sand-gravel capillary barrier. The seepage control layer was made up of deinking by-products (DBP), an industrial by-product that was previously disposed of as waste. The capillary barrier was designed using an adaptation of the Ross analytical solution and the scenario considered was that of steady-state flow during constant seepage flow applied uniformly at the top of the sand-gravel capillary barrier. Although these conditions appear simplistic, they were deemed reasonable because placement of the seepage control layer on the top of the capillary barrier led to very low suctions at the interface, thereby allowing uniform downward seepage rates, limited by the saturated hydraulic conductivity of the DBP. In this paper, a discussion about the behaviour of the cover system based on 4 years of field data from several instruments is presented. The challenge of using DBP, more precisely the settlement of the DBP layer and its impact on k sat , is also assessed. The DL was reassessed considering the new k sat . A discussion on the validity of employing analytical solutions to determine DL is also presented. This paper illustrates how certain variables affect the design of inclined CCBEs that include a highly compressible material as seepage control layer

Self-Healing Corrosion Protective Sol-Gel Coatings

Inspired by the state of the art and the recent advances in the field of self-healing corrosion protective coatings, the thesis entitled “Self-healing corrosion protective sol-gel coatings” addresses novel routes to self-healing corrosion protective sol-gel coatings via extrinsic and intrinsic healing approaches. The employed approaches aim at extending the service life of the coating and the underlying substrate by multiple damage closure/sealing and metal surface protection through incorporation of reversible tetrasulfide groups and inhibitor loaded containers respectively. Intrinsically healable hybrid organic-inorganic coatings containing reversible tetrasulfide groups were successfully developed and investigated using a combination of characterization techniques to address their healing kinetics and mechanism. Extrinsic healing concept was studied by encapsulation of corrosion inhibitors in smart micro- / nano-containers capable of on-demand leach out of the inhibitors to the damage site. Both routes explored have the potential to lead to future commercial self-healing coating systems.Novel Aerospace Materials Group (NovAM)Aerospace Engineerin

Comparison of the Performance of Poly Aluminum Chloride (PACl), Ferric Chloride (FeCl3), in Turbidity and Organic Matter Removal; from Water Source, Case-Study: Karaj River, in Tehran Water Treatment Plant No. 2

Coagulation and flocculation are the principal units in water treatment processes. In this study, the Jar test was used to investigate the effects of the pH and TOC on FeCl3 and PACl coagulants for further removal of turbidity, organic matter, aluminum, total organic carbon (TOC), dissolved organic carbon (DOC), organic Aadsorption at a wavelength of 254 nm (UV254 nm ), alkalinity, residual aluminum and ferric, total trihalomethans (TTHMs) in the Karaj River in the year 2007- 2008. These experiments were conducted through a bench scale study using conventional coagulation in the influent to Tehran Water Treatment Plant No. 2 (TWTP2).With normal pH levels, PACl demonstrated more efficiency than FeCl3 in removing turbidity, TOC, UV254 nm, and TTHMs. The lower coagulant consumption, high floc size, lower floc detention time, lower sludge production, lack of the need for pH adjustment in turbidity of 25 NTU and the lower alum consumption were the advantages of PACl application instead of FeCl3 as a coagulant. Also, PACl application was efficient at low turbidity (2 NTU), average turbidity (6 NTU), and high turbidity (100 NTU) in TOC, turbidity, UV254 nm , and DOC removal. Thus, PACl is an economical alternative as a coagulant in TWTP2

Effect of curing on the mechanical and healing behaviour of a hybrid dual network: a time resolved evaluation

In the present work we show the effect of the crosslinking degree on the mechanical and healing behaviour of a healable thermoset dual-network polymer. A hyphenated rheological test (i.e. simultaneous rheology and FTIR) was used to follow the effect of the curing process on the mechanical behaviour in relation to the underlying chemical reactions. The effect of curing on the bulk properties and the polymer interfacial healing was studied using gap closure kinetics and a fracture mechanical test. The increased crosslinking density at longer curing times led to a more temperature-stable polymer network with significantly higher mechanical properties (elastic modulus and strength at break). It was found that the damage closure kinetics decrease with the curing degree but the ultimate interfacial healing efficiency does not. The results here reported highlight the effect of the crosslinking density on the kinetics of damage closure with a low impact on the maximum interfacial healing efficiency as long as the amount of reversible bonds remains constant

Evaluation of an Experimental Model for Flat-Fan Nozzles Drift in Wind Tunnel by Image Processing

Each year, millions of liters of toxic liquid, are used to combat with pests and plant diseases in farms. The wide spread use of chemical pesticides causes great environmental hazards. Particles drift is one of the main problems in spraying which results in the contamination of farm lands, humans and animals. Management of particle size is regarded as the main factor in drift control. In this study, the effect of some parameters on the size of deposited particles on non-target areas was studied using statistical method. The effects of nozzle type (orifice size), spraying pressure, spraying boom height and wind speed as effective factors on drift were examined. A horizontal wind tunnel with working section of 0.47 m wide, 0.75 m height and 5.5 m long was used for testing. Experiment was performed in the form of factorial split-plot based on randomized complete block design with two replications. Droplets were measured in the treatment combinations of the type of flat-fan nozzle with three orifice area (11003- 0.87 mm2, 11004-1.18 mm2 and 11006- 1.8 mm2), spraying pressure (150, 275 and 400 kpa), wind speed (1, 2 and 3 m s-1) and the boom height of (0.35, 0.55 and 0.75 m). Water-sensitive papers were used at intervals of 0.8, 1.6 and 2.4 m from the tip of nozzles for detecting droplets size. The factors of pressure, speed and height had positive effects on the droplet size at the desired distance, but the effect of nozzle size on droplet size was negative. In the regression model the coefficients of speed was higher than the others

Effect of curing on the mechanical and healing behaviour of a hybrid dual network: A time resolved evaluation

In the present work we show the effect of the crosslinking degree on the mechanical and healing behaviour of a healable thermoset dual-network polymer. A hyphenated rheological test (i.e. simultaneous rheology and FTIR) was used to follow the effect of the curing process on the mechanical behaviour in relation to the underlying chemical reactions. The effect of curing on the bulk properties and the polymer interfacial healing was studied using gap closure kinetics and a fracture mechanical test. The increased crosslinking density at longer curing times led to a more temperature-stable polymer network with significantly higher mechanical properties (elastic modulus and strength at break). It was found that the damage closure kinetics decrease with the curing degree but the ultimate interfacial healing efficiency does not. The results here reported highlight the effect of the crosslinking density on the kinetics of damage closure with a low impact on the maximum interfacial healing efficiency as long as the amount of reversible bonds remains constant.Novel Aerospace Material