Lizette R. Chevalier

Literature Review of 2-D Laboratory Experiments in NAPL Flow, Transport, and Remediation

The migration of nonaqueous phase liquid (NAPL) contaminants in the subsurface results in a complex multiphase environment due in part to heterogeneity in both the soil and fluid saturations. To accurately predict the flow, transport, and remediation of NAPL contaminants, research has focused on laboratory and numerical modeling of the subsurface environment. Within this research, 2-D laboratory model are advantageous due to the fact that the capillary, viscous, and buoyancy forces found in the subsurface environment can be reproduced. Thus, they can be used to study flow and transport, test and develop remediation technologies, and verify numerical models. However, to date a comprehensive review of the 2-D experimental work has not been compiled. The review presented in this article should be of interest to geohydrologists, engineers and scientists involved in both applied and research aspects of NAPL-contaminated aquifers.

Urban Stormwater Governance: The Need for a Paradigm Shift

Abstract Traditional urban stormwater management involves rapid removal of stormwater through centralized conveyance systems of curb–gutter–pipe networks. This results in many adverse impacts on the environment including hydrological disruption, groundwater depletion, downstream flooding, receiving water quality degradation, channel erosion, and stream ecosystem damage. In order to mitigate these adverse impacts, urban stormwater managers are increasingly using green infrastructure that promote on-site infiltration, restore hydrological functions of the landscape, and reduce surface runoff. Existing stormwater governance, however, is centralized and structured to support the conventional systems. This governance approach is not suited to the emerging distributed management approach, which involves multiple stakeholders including parcel owners, government agencies, and non-governmental organizations. This incongruence between technology and governance calls for a paradigm shift in the governance from centralized and technocratic to distributed and participatory governance. This paper evaluates how five US cities have been adjusting their governance to address the discord. Finally, the paper proposes an alternative governance model, which provides a mechanism to involve stakeholders and implement distributed green infrastructure under an integrative framework.

Surfactant Dissolution and Mobilization of LNAPL Contaminants in Aquifers

Improper disposal, accidental spills and leaks of non-aqueousphase liquids (NAPL) such as gasoline, fuel oil and creosote result in long-term persistent sources of groundwater pollution.Column and 2-D tanks experiments were conducted to evaluate the use of surfactant-enhanced recovery of light non-aqueous phase liquids (LNAPL) in groundwater aquifers. These experiments focused on the use of surfactants to promote dissolution and mobilization in addition to evaluating the increase of aqueous phase permeability as residual NAPL is recovered. Further experiments are presented that show the innovative use of surfactants during primary pumping to recover free product canpotentially increase the amount of free product recovered, canpotentially reduce the amount of residual NAPL remaining afterprimary pumping and performs better than the use of surfactantsto mobilize trapped residual NAPL.

Interactive multimedia labware for strength of materials laboratory

A CD‐ROM–based laboratory manual for the torsion experiment in the Strength of Materials Laboratory was developed through collaboration between Civil Engineering and the Interactive Multimedia Department. The labware is intended to enhance student learning through the development of and exposure to richer learning tools, resources, and advanced technologies.

Evaluation of InSpectra UV Analyzer for measuring conventional water and wastewater parameters

Abstract A relatively new analytical instrument for the measurement of 5-day biochemical oxygen demand (BOD 5 ), chemical oxygen demand, total suspended solids (TSS), total organic carbon (TOC), nitrates and surfactants has been developed commercially. It is based on the use of ultraviolet spectrophotometry and a deterministic approach to analyze the samples spectrum by comparing it with a series of historical reference spectra. Using standard methods for the measurement of BOD 5 , TSS and TOC as true values, the use of this instrument was evaluated. The samples tested were obtained from both wastewater and water treatment facilities. Results indicate that the BOD 5 measurement performed best. There was no correlation found for TSS or TOC.

Impact of Surfactant on Configuration of Petroleum Hydrocarbon Lens

A laboratory-scale physical model was constructed for visual observation of the basic 2-D flow characteristics of a gasoline spill through an unconfined aquifer and the subsequent treatment with a surfactant. The model consists of a parallel-plate glass tank (1 m×1 m×5 cm) packed with Ottawa sand. Gasoline was released from a point source in the vadose zone. As the specific gravity of gasoline is less than one (LNAPL), it pooled above the water saturated pores of the tension saturated region of water. Beyond the lens of gasoline, the height of the capillary fringe was reduced due to capillary pollution. The gasoline lens was then treated with an aqueous phase surfactant solution of 2% dodecyl benzene sulfonate (anionic) and 2% polyethoxylate nonyl phenol (nonionic). This surfactant solution reduced the interfacial tension between the gasoline and the aqueous phase by an order of magnitude. The surfactant solution was released from the same point source in the vadose zone as the gasoline. As a result, the ...

Correlation model to predict residual immiscible organic contaminants in sandy soils.

Researchers in both environmental and petroleum engineering have conducted studies in one-dimensional columns to quantify the amount of residual nonaqueous phase liquids (NAPL) trapped in the porous media as a function of capillary, viscous and buoyancy forces. From these previous studies, it is proven that significant amounts of the original NAPL spill remain as a trapped residual. The objective of this research was to extend this body of work and to develop a correlation model that could predict residual NAPL saturation as a function of common soil characteristics and fluid properties. These properties include parameters derived from sieve analysis, namely, the uniformity coefficient (C(u)), the coefficient of gradation (C(c)), as well as fluid properties (interfacial tension, viscosity and density). Over 100 column experiments were conducted across a range of nine different soil gradations. The data produced by these tests, along with measured soil and fluid properties, were used to generate correlation models to predict residual NAPL saturation (S(rn)). The first correlation model predicts S(rn) for the region where residual NAPL saturation is independent of the capillary number, and dependent on C(u), C(c) and the Bond number. The second correlation model predicts S(rn) for the region where residual NAPL saturation is dependent on capillary number, as well as C(u), C(c) and the Bond number. The third correlation model predicts S(rn) over the entire region as a function of C(u), C(c) and the total trapping number. The correlation models have a R(2) value of 0.972, 0.934 and 0.825, respectively. Hence, the models may potentially be integrated into site characterization approaches.

Managing urban stormwater for urban sustainability: Barriers and policy solutions for green infrastructure application

Green infrastructure (GI) revitalizes vegetation and soil, restores hydro-ecological processes destroyed by traditional urbanization, and naturally manages stormwater on-site, offering numerous sustainability benefits. However, despite being sustainable and despite being the object of unrelenting expert advocacy for more than two decades, GI implementation remains slow. On the other hand, the practice of traditional gray infrastructure, which is known to have significant adverse impacts on the environment, is still ubiquitous in urban areas throughout the world. This relationship between knowledge and practice seems unaccountable, which has not yet received adequate attention from academia, policy makers, or research communities. We deal with this problem in this paper. The specific objective of the paper is to explore the barriers to GI, and suggest policies that can both overcome these barriers and expedite implementation. By surveying the status of implementation in 10 US cities and assessing the relevant city, state and federal policies, we identified 29 barriers and grouped them into 5 categories. The findings show that most of the barriers stem from cognitive limitations and socio-institutional arrangements. Accordingly, we suggest 33 policies, also grouped into 5 categories, which span from conducting public education and awareness programs to changing policies and governance structures.

Comparison of Primary and Secondary Surfactant Flushing to Enhance LNAPL Recovery

Column experiments were conducted to compare the use of surfactants as a part of primary pumping to remove free phase NAPL to the use of surfactants to reduce or recover residual LNAPL in secondary treatment. Eight surfactant blends were tested, for a total of 48 column experiments. The column experiments show that the use of surfactants during primary pumping: (1) can potentially increase the amount of free product recovered; (2) can potentially reduce the amount of residual NAPL remaining after primary pumping; and (3) performs better than the use of surfactants to mobilize trapped residual NAPL.

Use of Optimization to Develop a Correlation Model for Predicting Residual NAPL Saturation

Predicting the residual saturation of a trapped non-aqueous phase liquid (NAPL) contaminant is critical to estimate the region of contamination, the design of remediation strategies, and risk assessment. Models were developed to predict residual NAPL saturation utilizing optimization and non-linear functions, consequently allowing for a broader mathematical approach to model development. The input parameters evaluated represent soil and fluid properties; the uniformity coefficient (C u), the coefficient of gradation, the capillary number (Nc), the bond number (Nc), and the total trapping number (Nt). Overall, the model that performed the best was based on a second-order equation with the independent variables C u and Nt1 using the sum of the squares of the errors. The non-linear error function based on a derivative of Marquardts percent standard deviation performed the best for three other cases.