Mengistu Geza

• Professor (Assistant) at South Dakota School of Mines and Technology

Population growth and the associated increase in the use of Onsite Wastewater Treatment Systems (OWTS) in the Black Hills have been a reason for interest in nitrate contamination within the public water supply over the past few years. The main concern for the Black Hills is the presence of karst formation that all OWTS for wastewater travel faster,...

Experimental data from fixed-bed column studies and a numerical model based on convection-dispersion equations were used to describe transport and retention of Graphene Oxide (GO) in sand, biochar (BC), and BC modified with nanoscale zero-valent iron (BC-nZVI). Three blocking functions, namely no blocking, site-blocking, and depth-dependent blockin...

The potential for stacking ensemble modeling to enhance the performance and generalizability of machine learning (ML) models for the estimation of total suspended solids (TSS) concentration was assessed by comparing the results with ensemble boosting, bagging, and single ML models. Seven stacking ensemble models (M1 to M7) were created using combin...

This research investigated the removal of heavy metal ions (Cd, Cu, Pb, and Zn) and metalloid (As) common to stormwater runoff onto biochar-based media arranged in multiple configurations. Laboratory scale column experiments were conducted to quantify heavy metal removal efficiencies using sand, biochar, and nZVI-modified biochar (BC-nZVI) in four...

The objective of this research is to develop a module for the design of best management practices based on percent pollutant removal. The module is a part of the site-scale integrated decision support tool (i-DSTss) that was developed for stormwater management. The current i-DSTss tool allows for the design of best management practices based on flo...

Machine Learning (ML) algorithms provide an alternative for the prediction of pollutant concentration. We compared eight ML algorithms (Linear Regression (LR), uniform weighting k-Nearest Neighbor (UW-kNN), variable weighting k-Nearest Neighbor (VW-kNN), Support Vector Regression (SVR), Artificial Neural Network (ANN), Regression Tree (RT), Random...

A new Green Infrastructure Placement Tool coupled with Storm Water Management Model (GIP-SWMM) is developed for selection and strategic placement of Green Infrastructure (GI) practices. The tool supports GI placement at multiple scales - from a few city blocks to large watersheds. GI is a multi-benefit option for stormwater management and can revit...

Urbanization leads to water quality degradation in virtually all urban streams. Stormwater runoff contains suspended solids, nutrients, trace organic compounds, heavy metals, and pathogens that are discharged into natural water bodies, impairing ecosystems, and human health. Physically-based models are frequently used for predicting pollutant loadi...

In this paper, effects of bed roughness on the flow pattern and turbulence characteristics, such as velocity contours, shear stresses, Reynolds stresses and turbulence intensities on a three-dimensional wall jet were investigated experimentally. The experiments have been conducted in a channel which is made of metal floor and glass walls, width 0.5...

Planning of water reuse systems is a complex endeavor. We have developed a software toolkit, IRIPT (Integrated Urban Reclaimed Water Infrastructure Planning Toolkit) that facilitates planning and design of reclaimed water infrastructure for both centralized and hybrid configurations that incorporate satellite treatment plants (STPs). The toolkit in...

Florida’s aquifer system exhibits spatially variable hydrogeological characteristics including shallow depth to aquifer and karst features. These characteristics contribute to groundwater vulnerability to nitrogen contamination and thus warranting vulnerability studies that allow zonation of areas into different levels of susceptibility to contamin...

Oil shale deposits of the Green River Formation (GRF) in Northwestern Colorado, Southwestern Wyoming, and Northeastern Utah may become one of the first oil shale deposits to be developed in the U.S. because of their richness, accessibility, and extensive prior characterization. Oil shale is an organic-rich fine-grained sedimentary rock that contain...

Study region: The Upper Colorado River Basin (UCRB), comprised of the Colorado and Gunnison River basins, is the prime water source for much of the western United States. Study focus: Future climate change models were used to drive a hydrologic model of the UCRB to evaluate future water resources and hydropower potential of the basin, using three d...

Produced water management is a major challenge to oil and natural gas exploration and production, in particular for unconventional gas development. Rapid development of shale gas production, regulations, water scarcity, concerns of environmental impacts, and limited disposal options are driving operators to consider, plan and change their current h...

Understanding the fate and transport of wastewater constituents in groundwater is an important aspect in the design and management of onsite wastewater systems (OWS) as well as maintaining groundwater quality. Numerous mathematical models exist for evaluating fate and transport however the robust numerical models that exist are complex and difficul...

URTeC 1618963 Selection of water treatment processes is a complex task and has to consider many parameters including changes in water quality and quantity and overall economics. The DST is intended to help designers, utilities, and regulators to select treatment trains considering options for beneficial use of treated domestic wastewater. The VBA-b...

Onsite wastewater treatment systems are commonly used in the United States to reclaim domestic wastewater. A distinct biomat forms at the infiltrative surface, causing resistance to flow and decreasing soil moisture below the biomat. To simulate these conditions, previous modeling studies have used a two-layer approach: a thin biomat layer (1-5 cm...

A typical onsite wastewater treatment system consists of a septic tank and a soil treatment unit to treat wastewater before it is discharged through the vadose zone to an aquifer. A tool was developed for the purpose of predicting the fate and transport of nitrogen in soil treatment units (STUMOD or Soil Treatment Unit Model). STUMOD calculates nit...

A numerical watershed model was used to evaluate the potential influence of various point and nonpoint sources including on-site wastewater systems (OWS) on stream nitrate concentration in Turkey Creek Watershed, Colorado. A watershed analysis risk management framework model was used for this study, and was calibrated to observed stream nitrate con...

Nutrient loading to surface water systems has traditionally been associated with agricultural sources. Sources such as on-site wastewater systems (OWS) may be of concern especially in rural, nonagricultural watersheds. The impact of various point and nonpoint sources including OWS in Turkey Creek Watershed was evaluated using the Watershed Analysis...

Onsite wastewater treatment systems (OWTS) are used by approximately 20% of all households in the United States. The majority of these systems utilize a soil treatment unit (STU), which typically provide effective treatment of nutrients when located in appropriate soils. However, high OWTS density may result in an increase in wastewater nutrient lo...

Models that are simple to use have the advantage of being used by most professionals while complex models require trained professionals to set up, operate and interpret the the results. When possible, models should be simple to use and at the same time detailed enough to include most relevant processes. Thus, a user friendly model was developed for...

Watershed models require calibration before they are utilized as a decision-making tool. This paper describes a rigorous sensitivity analysis, automated parameter estimation and evaluation of prediction uncertainty for a Watershed Analysis Risk Management Framework (WARMF) model of the Turkey Creek Watershed. Sensitivity analysis was conducted usin...

Two erosion control methods are compared for cost effectiveness in reducing sediment loading into the streams; targeted replacement of agricultural crops and placement of vegetative filter strips (VFS) along field drains. The first method implements an optimization approach for reducing sediment load through targeting and replacement of row crops i...

* Normal0 falsefalsefalse MicrosoftInternetExplorer4 The Constructed Wetlands Module, built into the HYDRUS-2D software (Langergraber and Simunek, 2005), originally used to simulate wastewater treatment in wetlands, enables simulation of biozone formation and wastewater treatment in STUs. It is a numerical model, which accounts for the main micr...

Setting a field or laboratory experiment to study the behavior of Soil Treatment Units (STUs) can be a tedious and time consuming process. It may take months for an STU to reach a steady state due to the formation of biofilms ("clogging zones"), for instance. Even then, sampling "snapshots" do not necessarily provide an explanation of microbial pro...

The prediction accuracy of agricultural nonpoint source pollution models such as Soil and Water Assessment Tool (SWAT) depends on how well model input spatial parameters describe the characteristics of the watershed. The objective of this study was to assess the effects of different soil data resolutions on stream flow, sediment and nutrient predic...

Population growth and water quality in the foothills of Jefferson County are of concern to County’s Board of County Commissioners and the Planning and Zoning Department. The Department desires to meet the needs of residents for adequate supplies of good quality water. The Turkey Creek watershed is representative of the foothills portions of Jeffers...

Watershed management plans need to reflect the economic interests of landowners. Row crops such as peanuts grown on Fort Cobb watershed generate more income to the farmers, however the concerns are excessive sediment and nutrient loading to the streams. Conservation Reserve Program (CRP) and bioenergy crops were investigated as alternatives. Two ap...

The paper addresses these problems by presenting the outline of a theory for predicting the dynamic steering behaviour of animal-drawn implements. It is shown that the implement steering behaviour is governed by a first order differential equation. The theory has been tested on an experimental plow whose design is based on the Victory plow, a type...

Setting a field or laboratory experiment to study the behavior of Soil Treatment Units (STUs) can be a tedious and time consuming process. It may take months for an STU to reach a steady state due to the formation of biofilms ("clogging zones"), for instance. Even then, sampling "snapshots" do not necessarily provide an explanation of microbial pro...

Thesis (Ph. D.)--Oklahoma State University, 2006. Includes bibliographical references. Vita. The full text of the dissertation is available as an Adobe Acrobat pdf.file (xii, 229 p.); Adobe Acrobat Reader required to view the file.