Category: Research

Principal Investigator: Boris M. Khudenko (Georgia Institute of Technology)
Principal Investigator: Harold F. Wiedeman (Georgia Institute of Technology)
Principal Investigator: Joseph P. Gould (Georgia Institute of Technology)

Sponsor: GWRI
Start Date: 1986-07-01; Completion Date: 1986-07-01;
Keywords: Cadmium, Magnesium, Resource Recovery, Hazardous Wastes, Toxic Substances, Industrial Wastes, Waste Treatment

Description:
The kinetics of cementation of cadmium by magnesium were studied in a completely mixed batch reactor at room temperature and constant mixing rate and ionic strength. Magnesium strips provided in stoichiometric excess were used as electrodes. The effect of pH and initial cadmium concentration on the rate of cadmium removal and reaction stoichiometry, or yield of magnesium consumed per cadmium cemented, were evaluated.

The rate of cadmium removal was shown to be independent of pH between 3 and 6. However, as pH increased, the process yield became more favorable. This was attributed to the competing reaction of magnesium dissolution which decreases with increasing pH. The rate of cadmium removal was studied at initial cadmium concentrations between 1 and 100 mM. It was found that the rate and stoichiometry were highly dependent upon initial cadmium concentration.

At initial concentrations of up to approximately 25 mM, the reaction was found to follow apparent half order kinetics consistent with a migration control mechanism. As initial cadmium concentrations increased through this range, removal rates also increased. At approximately 25 mM, a transition was observed to apparent first order kinetics consistent with a diffusion control mechanism. There was a significant decrease in removal rates as the initial cadmium concentration increased to levels of greater than 25 mM.

Stoichiometry was found to become more favorable as initial cadmium concentration increased, and in some cases, less than 1 mole of magnesium was required to cement 1 mole of cadmium. This effect was attributed to electrolysis of water by the induced electrochemical system.

Principal Investigator: John C. Kabouris (Georgia Institute of Technology)
Principal Investigator: Aris Georgakakos (GWRI/Georgia Tech)

Sponsor: GWRI
Start Date: 1986-07-01; Completion Date: 1986-07-01;
Keywords: Unit Hydrographs, Markov Process, Streamflow Forecasting, Infiltration, Surface Runoff. Watershed Management.

Description:
A physically-based methodology for streamflow forecasting is researched and implemented. Watershed response is modelled as Continuous-Time Markov process whose states include both surface and subsurface runoff components. Based on probabilistic arguments, time-varying Instantaneous Unit Hydrographs are derived and convoluted with antecedent rainfall intensities to generate streamflow discharges. The method is applied to the Little River Watershed in South Georgia with encouraging results. Such models are useful in quantifying the response of ungaged watersheds and predicting streamflows in real time. In turn, such studies are instrumental in the design and operation of reservoirs.

Principal Investigator: Jack H. Reeves (The University of Georgia)
Principal Investigator: William P. McCormick (The University Of Georgia)

Sponsor: GWRI
Start Date: 1986-07-01; Completion Date: 1986-07-01;
Keywords: Low Flow Frequency, Design Flow, Time Series Analysis

Description:
In this report we analyze three problems related to a design low flow called the seven day, ten year minimum streamflow ,(7Q1O). The 7Q1O denotes the tenth percentile of the distribution of the streamflow, which gives for a one year period the lowest level of streamflow for which there was a seven consecutive day period with flows below that value on each day. The 7Q1O is commonly used as an annual design low streamflow for determining waste water discharge permit specifications.

The first problem we address is to determine monthly design low streamflow values. A method of assigning design low flow values which can vary over the year is of interest in order to allow greater use of the stream for diluting waste water discharges. We offer a simple method for calculating monthly design low flow values, which does not lead to any greater number of daily contraventions below the monthly design flows than that which already occurs for the one fixed annual 7Q1O method.

The second problem addressed concerns the estimation of 7QIO with a confidence interval. We offer a method based on a model for daily streamflows, and we compare our estimation procedure with two other often used procedures.

The third problem concerns the estimation of 7Q1O when the record of streamflow is only partial and short. We recommend a procedure which incorporates the use of rainfall data into our estimation procedure for 7Q1O.

Principal Investigator: Yoko Parmelee (The University Of Georgia)
Principal Investigator: Jackie Sellers (University of Georgia)
Principal Investigator: Ronald M. North (University of Georgia)
Principal Investigator: Hubert A. Pless (The University Of Georgia)

Sponsor: GWRI
Start Date: 1986-06-01; Completion Date: 1986-06-01;
Keywords: financing, pricing, user charges, cost sharing, financial feasibility, economic cost, water rates, repayment, demand, benefit cost analysis, cost allocation, water rights, tariff, market value, water policy.

Description:
As appropriated Federal funds for water resources projects, programs, and services decline the funding needs must be made up by state and local governments and/or by the private sector businesses and consumers. As the responsibility for infrastructure moves to the private sector it is essential for economic efficiency and financial feasibility to price water services at their full cost or at a price that reflects their value to consumers and users in a manner that covers at least the full cost. For all of the flow services produced by water (supply, waste treatment, hydropower), a two part tariff is recommended to reflect a capacity charge and a commodity charge. Tariffs should be set to reflect the high fixed cost of service and to reflect user willingness to pay for essential services. The excess revenue may be used to provide for welfare transfer to low income users or to provide for water related common goods type services such as flood control or environmental enhancement.

The researchers review demand theory and present a case study for price/income elasticities of demand for Georgia municipal systems to illustrate price and income effects on revenues. Similar theoretical constructs are presented for two market pricing solutions and for discriminatory pricing within a market for flow type commodities, both systems intended to generate revenue more closely aligned to market value of the services provided. A second case study is used to show how updated alternative cost pricing will lead to increases of 4-10 times in the revenue received from hydropower generation (capacity and energy). Although some repayments are long term contracts, there are opportunities to renegotiate contracts for better terms to Federal agencies producing and marketing hydropower. Specific details are given for the Southeast Power Administration (SEPA).

Principal Investigator: James L. Anderson (The University of Georgia)

Sponsor: GWRI
Start Date: 1986-07-01; Completion Date: 1986-07-01;
Keywords: Water Analysis, Correlation, Electrochemistry, Spectrophotometry

Description:

Theory was developed and experimentally tested for the response of amperometric electrochemical detectors in thin-layer flow channels, and theory was developed and preliminary experiments initiated for the response of spectroelectrochemical correlation detectors in thin-layer flow channels. The theory for amperometric response was evaluated experimentally for several designs of arrays of thin strip microelectrodes in series on one wall of a flow channel, with long axes perpendicular to flow. The electrode arrays were fabricated microlithographically, using gold conductors on silicon dioxide-covered silicon wafers, and platinum conductors on glass or quartz substrates. Experiments were carried out using flow injection methodology with sufficiently large injected volume to insure attainment of steady-state response. Experimental response was in excellent agreement with theoretical prediction, for a series of uniformly spaced arrays of gold microelectrodes with widely varying spacing and number of electrodes. Optimum progression of microelectrode spacing across the array was investigated theoretically. It was shown that the optimum geometry is a uniform array of strip electrodes of equal size and constant spacing. Experimental results support the theoretical conclusion.

Theory was developed for the correlation detector based on electrochemical and spectrophotometric signals generated simultaneously in a thin-layer detector cell. The optimum geometry for the spectrophotometric optical beam was evaluated based on signal/noise considerations, assuming that shot noise was the dominant noise source.

Optimum response is predicted for illumination parallel to the electrode surface and either parallel or perpendicular to flow. Preliminary experiments are qualitatively consistent with theoretical predictions.

Principal Investigator: Dan M. Skolds (Georgia Institute of Technology)
Principal Investigator: Terry W. Sturm (Georgia Tech)

Sponsor: GWRI
Start Date: 1985-06-01; Completion Date: 1986-06-01;
Keywords: Bed load, Dams, Degradation, Rivers, Scour, Sediment

Description:

The effects of man’s activities on an alluvial river are investigated in this research. Specifically, streambed adjustments downstream of a dam constructed on a wide alluvial river are studied experimentally in a laboratory model of an existing alluvial river. The experimental results show that both scour and fill occur in the river bed downstream of the dam as the result of an alluvial bar moving through the system. The bar originates from the local scour hole just downstream of the outlet structure. The channel becomes choked on one side by the bar, while scour occurs on the opposite side of the channel. A numerical model using the streamtube approach is developed to enable prediction of both scour and fill in the same river cross section. The numerical model is tested for sensitivity to the upstream boundary condition, the sediment porosity, the sediment transport relation, and the numerical time step. When compared with the experimental results, the numerical model results agree with the observed scour and fill trends, but the magnitudes are underpredicted. The streamtube approach was found to be a viable technique for investigating two-dimensional streambed adjustments, but additional refinements related to the fundamental problems of transverse velocity distribution and widening due to streambank failure are needed as these problems are illuminated by further research.

Principal Investigator: George A. Brook (University of Georgia)
Principal Investigator: Chin-Hong Sun (The University of Georgia)

Sponsor: GWRI
Start Date: 1985-08-01; Completion Date: 1985-08-01;
Keywords: Modelling, Simulation, Georgia, Hydrology, Lower Coastal Plain, Watershed, Ground Water, Streamflow

Description:
Overland flow to streams is rare in the Lower Coastal Plain watersheds of Georgia. As a result, commonly-used watershed hydrologic simulation models can not be used to predict streamflow accurately. Therefore, a distributed watershed hydrologic simulation model, named COASTAL, has been developed specifically for the Lower Coastal Plain regions of Georgia, Florida, and South Carolina. A basic assumption of the model, which can be run on a personal computer, is that all streamflow results from ground water discharge into stream channels. COASTAL was developed by combining surface and ground water simulation models. In modelling, the watershed is divided into rectangular grid elements. Input data for each grid element can be obtained easily from topographic maps, soil surveys, aerial photographs and generalized published tables. At least one year of measured daily streamflow data is needed to calibrate the model. Outputs from the model include daily stream discharge, a water budget, and average daily ground water level for each grid element within the watershed.

The model has been tested using data for the Hurricane Creek watershed of Georgia. Correlation coefficients between simulated and measured streamflow were in the range 0.8 to 0.9. Work is presently underway to improve COASTAL by installing an automatic calibration module.

Principal Investigator: M. M. Aral (Georgia Institute of Technology)

Sponsor: GWRI
Start Date: 1984-08-01; Completion Date: 1985-08-01;
Keywords: Ground water seepage, *Finite element method, Multilayer aquifers, Aquifer management

Description:
In order to effectively monitor and manage aquifers subjected to artificial recharge as well as increased pumping demands, it becomes necessary to analyse their hydrodynamic response. Several mathematical/numerical models are developed earlier to accomplish this purpose in a regional scale for single layer aquifers. In the present study a regional two-dimensional flow analysis is formulated using finite element techniques for multilayer aquifers. The advantages of using finite element analysis for aquifer analysis become evident when attempting to model irregular boundaries and variable inputs such as recharge, pumping and field properties in multilayer systems. Numerical solutions are also presented, which when compared with known analytical solutions show the accuracy levels expected and also some limitations of the model. This study is a preliminary step toward the ultimate goal of predicting and monitoring water quality and quantity in a multilayer aquifer system.

Principal Investigator: Gian S. Ghuman (Savannah State College)

Sponsor: GWRI
Start Date: 1984-08-01; Completion Date: 1985-08-01;
Keywords: groundwater, contamination, leaching, sludge, water quality

Description:

A study was conducted on the City of Savannah’s Water Pollution Control Plant to determine the efficiency of wastewater treatment in the removal of heavy metals. Four periodic samples of influent water, effluent water and sewage sludge were collected in October, December, 84 and March, June, 85 and were analyzed for the concentrations of Mn, Zn, Cd, Cu, Ni and Cr. The concentrations of dissolved heavy metals were slightly greater in the treated effluent water than in the influent water. Separation of sludge was effective in the overall removal of heavy metals from the wastewater. The activated sludge component of effluent water had high concentrations of heavy metals and must be fully removed to minimize the heavy metal content in the discharged water. Among the heavy metals, the total concentrations of Zn, Cu and Ni in the effluent water (both the aqueous and the sludge phases) were decreased, which indicated a material balance of zero for these metals when removal in the separated sludge is considered. On the other hand, the total concentrations of Mn, Cd and Cr were increased in the effluent water as compared to the influent water and it may be possibly due to the influent water samples collected from the outlet in the plant not being truly representative of the material, going in for treatment. A leaching study in PVC columns packed with sludge ash (pH 10.4) was conducted using de-ionized water, lagoon water, and acetic acid 5000 ppm (pH 5.0) as the leaching solutions. All leachates contained very low amounts of heavy metals and the incineration of limed sewage sludge into ash appears to be an efficient method of disposal. High concentrations of heavy metals as insoluble oxides in the sludge ash may prove to be a commercial source in the future for chemical separation.

Principal Investigator: James E. Kundell (The University of Georgia)
Principal Investigator: S. Wesley Woolf (The University of Georgia)

Sponsor: GWRI
Start Date: 1984-07-01; Completion Date: 1985-06-01;
Keywords: coastal marshes, drainage, erosion, estuaries, flood control, forest management, Georgia, land use, law, marshes, salt marshes, soils, urban runoff, vegetation, water management, waterfowl, wetlands.

Description:
Georgia is experiencing “Sunbelt” population growth and expansions in agricultural and forestry production resulting in increased pressure to convert wetlands to other uses. An analysis was undertaken of data generated by the Fish & Wildlife Service’s National Wetland Inventory, Georgia Department of Natural Resources’ Landsat land use study, and Soil Conservation Service’s National Resources Inventory. Wetland acreage, distribution, types, and trends were identified for Georgia. A review of case law and statutory law was conducted and wetland management activities of federal, state, and local governments were determined. Alternative management strategies were identified for Georgia.