Degree Level

Rural Shared Service Arrangements: An Analysis of Perceived Responsibilities / Roles With and Without Site-Based Decision-Making (open access)

Rural Shared Service Arrangements: An Analysis of Perceived Responsibilities / Roles With and Without Site-Based Decision-Making

This study examined the perceptions of school superintendents of districts and building principals of schools within selected shared service arrangements in the state of Texas who receive services from the cooperative, and selected directors of rural shared service arrangements pertaining to the responsibilities and roles of shared service arrangements when site-based decision-making (SBDM) was used as the guiding philosophy.
Date: December 1996
Creator: Mullins, Frank E. (Frank Edward)
System: The UNT Digital Library
The Development of a Rating Scale for Use by Texas School Board Members to Evaluate a Superintendent's Performance (open access)

The Development of a Rating Scale for Use by Texas School Board Members to Evaluate a Superintendent's Performance

The problem with which this investigation is concerned is that of developing a scale for rating a public school superintendent in Texas in terms of his adherence to selected characteristics of administrative leadership. A secondary problem is to verify the hypothesis that very few schools in Texas, if any, use a rating scale to evaluate the performance of the superintendent. The purpose of this study will be to identify a set of administrative leadership characteristics which are accepted by members of Boards of Trustees, professors of educational leadership, and superintendents.
Date: August 1972
Creator: Craighead, Carl H., 1934-
System: The UNT Digital Library
Participant's perceptions of online staff development and learning tools. (open access)

Participant's perceptions of online staff development and learning tools.

This study analyzed participants in an online professional development and certification program can to see if they could predict the learning value of individual distance education tools. The Texas Center for Educational Technology (TCET) funded by the Texas Telecommunications Infrastructure Fund (TIF) designed the Technology Applications Certification Program (TACP). In the TACP, students are offered four graduate level classes which, when combined, meet the standards for the State Board for Educator Certification (SBEC) Technology Applications certification. The four courses that comprise the TACP are Computers in Education, Introduction to the Internet, Multimedia in Technology Applications, and Introduction to Video Technologies. The first course started in January 2002 with approximately 706 participants in 40 cohorts across the state of Texas. The TACP combines two different worlds of technology training. Half of the coursework was completed through asynchronous content and discussions, while the remaining classes were hands-on classes in local district computer labs. These face-to-face meetings enabled learners to get hands-on training with direct assistance. Between the online and face-to-face segments, a variety of learning tools were introduced to the participants. Participants were surveyed through the online Snapshot Survey in January and again in September.
Date: May 2003
Creator: Smolka, Jennifer
System: The UNT Digital Library
The Isolation and Characterization of a Hitherto Undescribed Gram-Negative Bacterium (open access)

The Isolation and Characterization of a Hitherto Undescribed Gram-Negative Bacterium

A unique undosciribed gramnegative rod is extensively characterized in this study. The cells of this unusual water isolate measure 1.2 X 6.5 microns, The most distinguishing characteristic of the bacterium is a polar tuft of 35-40 flagella that aggregate to function as a single organelle which is visible under phase contrast. Aging cells deposit poly- -hydroxybutyric acid granules which are bound by an inclusion membrane made up of four distinct layers. It also possesses an unusual exterior membrane outside the cell wall which contains large fibrils of protein running at a slight angle to the longitudinal axis of the cell. The guanosine-cytosine ratio was found to be 62.2$. The organism's taxonomic position was further investigated by immunological, morphological, and biochemical methods. It was found to be most closely akin to members of the genus Pseudo onas, although somewhat divergent from other species classified in this genus. After careful evaluation of the findings obtained during this study, the new bacterium was subsequently named Pseudomonas multiflagella.
Date: August 1972
Creator: Lassiter, Carroll Benson
System: The UNT Digital Library
Standing in the Gap: Subposts, Minor Posts, and Picket Stations and the Pacification of the Texas Frontier, 1866-1886 (open access)

Standing in the Gap: Subposts, Minor Posts, and Picket Stations and the Pacification of the Texas Frontier, 1866-1886

This dissertation describes the various military outposts on the Texas frontier between 1866 and 1886. It is arranged geographically, with each chapter covering a major fort or geographical area and the smaller posts associated with it. Official military records and government reports serve as the primary sources of data. In 1866 when the United States Army returned to the defense of Texas after four years of civil war, the state's frontier lay open to depredations from several Indian tribes and from lawless elements in Mexico. The army responded to those attacks by establishing several lines of major forts to protect the various danger areas of the frontier. To extend its control and protection to remote, vulnerable, or strategically important points within its jurisdiction, each major fort established outposts. Two main categories of outposts existed in Texas, subposts and picket stations. Subposts served as permanent scouting camps or guarded strategic points or lines of communication. Picket stations protected outlying locations, such as stage stations, that were particularly vulnerable to attack. Because Indians raiding in Texas usually operated in fairly small groups, garrisons at outposts were similarly small. Company-sized detachments generally garrisoned subposts, and picket stations seldom held more than a dozen …
Date: May 1995
Creator: Uglow, Loyd M. (Loyd Michael)
System: The UNT Digital Library
Petroleum in Saudi-American Relations: The Formative Period, 1932-1948 (open access)

Petroleum in Saudi-American Relations: The Formative Period, 1932-1948

This dissertation is an examination of the American oil industry in Saudi Arabia and its influence on United States foreign policy. The study examines the Americans who went to Saudi Arabia, the effect of the oil companies on Saudi- American relations, and the American government's response to oil company actions. There is an attempt to answer such questions as: Did the oil companies exert pressure on the American government to influence governmental policy? How effective was this pressure? And, what benefits did the oil companies have from their relationship with the government? The study concludes that Aramco was instrumental in bringing official and nonofficial contact and representation between Saudi Arabia and the United States. Moreover, Aramco was instrumental in involving the American government directly in Saudi Arabia through the extension of lend-lease aid to that country. American government involvement thwarted potential British ambitions in the Saudi oil resources and resulted in the American dominance of oil interests in that kingdom. In addition, Senate investigations showed that the oil companies grossly overcharged the United States Navy on oil purchases and that the financial assistance to Saudi Arabia was made for the protection of Aramco's oil concession.
Date: August 1978
Creator: Nairab, Mohammad Mahmud
System: The UNT Digital Library
Considerations in Selecting, Developing, and Validating Laboratory Experience Units in General Biology for Prospective Elementary School Teachers (open access)

Considerations in Selecting, Developing, and Validating Laboratory Experience Units in General Biology for Prospective Elementary School Teachers

The primary purpose of this study was to develop the considerations and techniques for the selection, development, and validation of laboratory experience units in general biology for prospective elementary school teachers. The completed laboratory experience unites developed in this study may serve as resources of activities for college instructors who teach general biology to undergraduate majors in elementary education. For purposes of this study the laboratory experience unites were centered about those principles of general biology which an elementary school teacher should understand in order to teach about plants and animals.
Date: August 1956
Creator: Syrocki, Boleslaus John, 1912-
System: The UNT Digital Library
Emotional/Behavioral Disturbance and Speech/Language Disorders: Prevalence of the Dual Diagnoses in a School-Age Population (open access)

Emotional/Behavioral Disturbance and Speech/Language Disorders: Prevalence of the Dual Diagnoses in a School-Age Population

The purpose of this study was to examine the prevalence of the comorbidity of emotional/behavioral disorders (EBD) and speech/language disorders among those students identified as under The Individuals With Disabilities Education Act criteria as emotionally disturbed and speech impaired. The literature reviewed included clinical and school settings that examined a cooccurrence of language disorders in the EBD population. Other research reported a lack of routine involvement of speech/language therapists in the assessment of the EBD population. Implications from clinical studies suggested a need for greater attention to language disorders in a multi- and interdisciplinary assessment. This study investigated the prevalence of the dual occurrence of EBD and speech/language disorders in Grades 2 through 6 in Texas schools in light of the known research. Relationships in ethnicity and socioeconomic status were examined using chi-square test of independence. Aggregate data were obtained from the database of the Texas Pupil Information Management System and from survey questionnaire responses provided by speech therapists in selected districts. The literature review focused on the impact of language in the development of appropriate personal interactions and communication skills, especially those relevant to pragmatic language factors and the implications of language competency in successful personal living and career …
Date: May 2000
Creator: Silver, Kathi Olinsky
System: The UNT Digital Library
An Empirical Investigation into the Information Content of the Required Disclosure of Oil and Gas Reserve Values (open access)

An Empirical Investigation into the Information Content of the Required Disclosure of Oil and Gas Reserve Values

This empirical study is concerned with whether the oil and gas reserve value data reported by petroleum producers have been utilized by investors. Reporting reserve value data based on a present value approach is the initial step toward the development of the Securities and Exchange Commission's new accounting method called "Reserve Recognition Accounting" (RRA) for oil and gas producers. Experimentation with this new accounting concept in the oil and gas industry has been adopted as a tentative resolution of the long-standing controversy over valuation of oil and gas reserves and the measure of income from oil and gas exploration. Evidence gathered in this research will be valuable to the SEC in its efforts to assess the usefulness of RRA. This dissertation assumes capital market efficiency and address two specific questions. First, do investors behave as if the reported end-of-year reserve value data are effective signals for pricing securities of oil and gas producers? Second, has the SEC-mandated reserve value disclosures induced any response in the capital market? Two research designs were employed to permit extensive investigation of these two questions.
Date: August 1980
Creator: Huang, Jiunn-Chang
System: The UNT Digital Library
Use of geographic information systems for assessing ground water pollution potential by pesticides in central Thailand (open access)

Use of geographic information systems for assessing ground water pollution potential by pesticides in central Thailand

This study employed geographic information systems (GIS) technology to evaluate the vulnerability of groundwater to pesticide pollution. The study area included three provinces (namely, Kanchana Buri, Ratcha Buri, and Suphan Buri) located in the western part of central Thailand. Factors used for this purpose were soil texture, percent slope, primary land use, well depth, and monthly variance of rainfall. These factors were reclassified to a common scale showing potential to cause groundwater contamination by pesticides. This scale ranged from 5 to 1 which means high to low pollution potential. Also, each factor was assigned a weight indicating its influence on the movement of pesticides to groundwater. Well depth, the most important factor in this study, had the highest weight of 0.60 while each of the remaining factors had an equal weight of 0.10. These factors were superimposed by a method called “arithmetic overlay” to yield a composite vulnerability map of the study area. Maps showing relative vulnerability of groundwater to contamination by pesticides were produced. Each of them represented the degree of susceptibility of groundwater to be polluted by the following pesticides: 2,4-D, atrazine, carbofuran, dicofol, endosulfan, dieldrin & aldrin, endrin, heptachlor & heptachlor epoxide, total BHC, and total DDT. …
Date: August 2002
Creator: Thapinta, Anat
System: The UNT Digital Library
Lone Star Booster: The Life of Amon G. Carter (open access)

Lone Star Booster: The Life of Amon G. Carter

Abstract Though a very influential Texan during the first half of the twentieth century, Amon Carter has yet to receive a full scholarly treatment, a problem which this dissertation attempts to rectify by investigating the narrative of Carter’s life to see how and why he was able to rise from humble beginnings to become a powerful publisher who symbolized boosterish trends within Texas and the New South. Publisher of the Fort Worth Star-Telegram, philanthropist, oilman, and aviation supporter, Carter used his power and influence to become a leading booster of his city and region seamlessly making the transition from being a business progressive to New Deal supporter to an Eisenhower Democrat. His connections with corporations like American Airlines and General Motors helped bring aviation and industry to his region, and his ability to work with public and private entities helped inspire his failed attempt to make the Trinity River navigable up to Fort Worth. His own success at building the Star-Telegram into the largest circulating newspaper in Texas encouraged him to expand his media empire into radio and television, while the wealth he gained from his oil activities enabled him to form a philanthropic foundation that would provide support for …
Date: December 2011
Creator: Cervantez, Brian
System: The UNT Digital Library
Calcium Aluminates Synthesis, Characterization, and Hydration Behavior (open access)

Calcium Aluminates Synthesis, Characterization, and Hydration Behavior

The hydration behavior of the calcium aluminates as a function of the glass content, the curing temperature, and the water-solid ratio was investigated. In order to keep them from influencing the results, the free-lime content and the surface area of all samples were kept constant, whenever possible. Samples were hydrated with a water-solid ratio of 10/1 for periods of 1 to 90 days. Three curing temperatures were studied; 2°C, 25°C, and 50°C. Samples were hydrated in tightly sealed polyethylene containers to prevent reactions with atmospheric carbon dioxide. The hydration was followed by X-ray diffraction and thermal analysis. Only two samples, Hexacalcium Tetra-alumino Magnesium Silicate and Tricalcium Magnesium Dialuminate, were successfully prepared in an amorphous form. These compounds were used to investigate the effect of glass content on the hydration behavior. Results indicate that when the glass content is increased a corresponding increase is found in the percent combined water. Samples hydrated at 25°C were influenced by changes in the glass content to a greater degree than were those hydrated at either 2°C or 50°C. The effect of the water-solid ratio on the hydration behavior of the calcium aluminates was studied using the compounds; Hexacalcium Tetra-Alumino Magnesium Silicate/ and Dodecacalcium Hepta-Aluminate. …
Date: December 1984
Creator: Griffin, Joseph George
System: The UNT Digital Library
Poststructuralist Critical Rhetorical Analysis as a Problem Analysis Tool: A Case Study of Information Impact in Denton’s Hydraulic Fracturing Debate (open access)

Poststructuralist Critical Rhetorical Analysis as a Problem Analysis Tool: A Case Study of Information Impact in Denton’s Hydraulic Fracturing Debate

Energy and the natural environment are central concerns among stakeholders across the globe. Decisions on this scale often require interaction among a myriad of institutions and individuals who navigate a complex variety of challenges. In Denton, Texas in 2014, voters were asked to make such a decision when tasked with a referendum to determine whether the city would continue to allow hydraulic fracturing activity within its borders. For social scientists, this situation requires further analysis in an effort to better understand how and why individuals make the decisions they do. One possible approach for exploring this process is a method of poststructuralist critical rhetorical analysis, which is concerned with how individuals’ identities change through interaction with institutions. This study reflects upon the texts themselves through a poststructuralist critical rhetorical analysis of images employed by those in favor of and those against Denton’s ban on hydraulic fracturing in an attempt to identify images that alter the grid of intelligibility for the audience. The paper includes deliberation about the relative merits, subsequent disadvantages, and possible questions for further study as they relate to the theoretical implications of critical rhetorical analysis as information science. Ultimately, the study identifies poststructuralist critical rhetorical analysis as …
Date: May 2016
Creator: Sykes, Jason
System: The UNT Digital Library
Ecological Sustainability and Peace: The Effect of Ecological Sustainability on Interstate and Intrastate Environmental Conflict (open access)

Ecological Sustainability and Peace: The Effect of Ecological Sustainability on Interstate and Intrastate Environmental Conflict

This study examines the relationship between ecological sustainability and violent conflict at both the interstate and intrastate level. In particular, this study explores the effect of ecological sustainability of a society on the initiation and the occurrence of violent conflict. By developing a theory, which is named "Eco-peace," this study hypothesizes that the more ecologically sustainable the socioeconomic system of societies, the less likely the society is to initiate interstate conflict. Regarding intrastate conflict, it is hypothesized that the more ecologically sustainable the mode of development pursued by the Third World society is, the more likely that society is to experience intrastate conflicts. To test the hypotheses, this study conducts cross-national time-series analyses for 97-127 countries. Negative binomial and Poisson models are used for interstate conflict during 1960-2001, and logit and rare event logit models are used for intrastate conflict during 1960-1999. Militarized interstate dispute dataset and Uppsala Armed Conflict Program dataset are employed for interstate and intrastate conflict. For ecological sustainability, Ecological sustainability factor index and Environmental sustainability index are used. Through the analyses, this study found the supports for the theoretical argument that the ecologically unsustainable modes of development cause the initiation of interstate conflict and the incidence …
Date: August 2010
Creator: Yoon, Jong-Han
System: The UNT Digital Library
An Assessment of the Effect of News Announcements on Stock Prices of Oil and Gas Producing Companies (open access)

An Assessment of the Effect of News Announcements on Stock Prices of Oil and Gas Producing Companies

This empirical study is concerned with the extent to which news announcements affect the performance of common equity securities of oil and gas producing companies. The market effects of news announcements are considered to be of importance in resolving two issues. One concerns financial statement disclosure and the second concerns examination of prior oil and gas industry-related accounting research. This dissertation assumes capital market efficiency and addresses two research questions: do news announcements concerning activities of nonintegrated oil and gas producing companies affect the companies' common stock prices, and are announcements concerning nonintegrated oil and gas companies' financial, personnel, explorational, and developmental and operational activities used equally by investors in their decision-making?
Date: August 1982
Creator: Wright, Charlotte Jean
System: The UNT Digital Library
Resistance and Morphology of Azotobacter Vinelandii Grown on Dialyzed Soil Agar (open access)

Resistance and Morphology of Azotobacter Vinelandii Grown on Dialyzed Soil Agar

The objectives of this research were to identify the form of Azotobacter as it exists in situ in the soil; to compare its resistance to that of laboratory grown cysts typical of those described in the literature; and to compare its resistance to that of cells grown on dialyzed soil agar. In addition, the morphology of the cells grown on dialyzed soil agar was examined by light and electron microscopy and then compared to the cysts grown on n-butanol Burk's medium. Dipicolinic acid and oxygen uptake rate were measured in cysts and on cells grown on dialyzed soil agar in order to determine whether the cells grown on dialyzed soil agar were endospores or other dormant form and also to measure the respiratory quotient in these cells.
Date: May 1987
Creator: Gogu, Sudhir Reddy
System: The UNT Digital Library
An Analysis of the Accounting System of the Quincy Mining Company: 1846-1900 (open access)

An Analysis of the Accounting System of the Quincy Mining Company: 1846-1900

This historical study examines the evolution of the accounting system of the Quincy Mining Company between 1846 and 1900. The external financial reporting practices and internal accounting procedures of the firm are defined and interpreted in the context of three time periods that portray the formation, growth and maturation of the firm. Each period reflects unique economic and social conditions that are associated with changes in the firm's accounting system. A cross temporal analysis of these changes highlights three factors: the relationship between the accounting system and the labor force, the emergence of accounting as a control mechanism and the diminishing informational content of the firm's annual reports. Primary sources are used to document the perspectives of the Quincy management and to assess the motivations for accounting processes such as internal control, auditing procedures, responsibility centers and other managerial practices. This study addresses the inherent nature of accounting information and its relationship to the economic and social environment of an individual firm in the nineteenth century.
Date: December 1992
Creator: Michael, Rodney R. (Rodney Richard)
System: The UNT Digital Library
An Analysis of Audit Risk in Associating with Reserve Information of Oil and Gas Companies (open access)

An Analysis of Audit Risk in Associating with Reserve Information of Oil and Gas Companies

This research was designed to investigate the relationship between audit risk and the conduct of the audit engagement in the specific context of an oil and gas audit. Because reserve estimates are in the financial reports of oil and gas entities (in the depreciation, depletion and amortization calculation, the limitation on capitalized costs for companies using the full-cost method, and the required supplementary disclosure for companies subject to Securities and Exchange Commission requirements) and because the reserve estimation process is considerably affected by numerous factors, there is a chance that a material error could be incorporated into the financial statement representations with which the auditor is associated. The objective of the research was to (1) identify conditions which are important in an assessment of audit risk in associating with reserve estimates, and (2) determine the impact of some of these conditions on the conduct of the audit.
Date: December 1983
Creator: Lee, Patsy Linn
System: The UNT Digital Library
An Empirical Study of Financial Analysts' Valuations Using Proposed Disclosures About Oil and Gas Producing Activities (open access)

An Empirical Study of Financial Analysts' Valuations Using Proposed Disclosures About Oil and Gas Producing Activities

This empirical study is concerned with the usefulness of proposed supplementary disclosures for oil and gas producers to financial analysts in valuing a company. It is concerned with what supplementary information is being used, to what extent it is being used and which type of information is used most. Three main research procedures are employed. In the first procedure, the Mann-Whitney U Test is applied to determine any significant difference between valuing an oil and gas producing company using basic financial statements and ratio data, and valuing the same company with this information plus the proposed disclosures. The second procedure involves applying the chi-square and Cramer's V statistics to determine whether the disclosure information caused switching in valuation method used for each of the cases. The third procedure tests for significant differences between financial ratios used for each case by employing the test of differences between two proportions. Additional evaluation attempts to determine analysts' perceived usefulness of each of the schedules of the proposed disclosures
Date: December 1983
Creator: Avard, Stephen L. (Stephen Lewis)
System: The UNT Digital Library
From Lost Cause to Female Empowerment: The Texas Division of the United Daughters of the Confederacy, 1896-1966 (open access)

From Lost Cause to Female Empowerment: The Texas Division of the United Daughters of the Confederacy, 1896-1966

The Texas Division of the United Daughters of the Confederacy (UDC) organized in 1896 primarily to care for aging veterans and their families. In addition to this original goal, members attempted to reform Texas society by replacing the practices and values of their male peers with morals and behavior that UDC members considered characteristic of the antebellum South, such as self-sacrifice and obedience. Over time, the organization also came to function as a transition vehicle in enlarging and empowering white Texas women's lives. As time passed and more veterans died, the organization turned to constructing monuments to recognize and promote the values they associated with the Old South. In addition to celebrating the veteran, the Daughters created a constant source of charity for wives and widows through a Confederate Woman's Home. As the years went by, the organization turned to educating white children in the “truth of southern history,” a duty they eagerly embraced. The Texas UDC proved effective in meeting its primary goal, caring for aging veterans and their wives. The members' secondary goal, being cultural shapers, ultimately proved elusivenot because the Daughters failed to stress the morals they associated with the Old South but because Texans never embraced …
Date: August 2001
Creator: Stott, Kelly McMichael
System: The UNT Digital Library
Determinants of the Magnitude of Foreign Direct Investment: An Analysis of Korean Manufacturing MNCs (open access)

Determinants of the Magnitude of Foreign Direct Investment: An Analysis of Korean Manufacturing MNCs

The purpose of this study is, therefore, to investigate empirically the firm- and location-specific determinants of the magnitude of FDI by Korean manufacturing MNCs--one of the leading Third World MNCs. This study also examines firm-specific characteristics that distinguish Korean MNCs investing in developing countries from those investing in developed countries.
Date: December 1993
Creator: Kim, Seong-Soo
System: The UNT Digital Library
Charge Interaction Effects in Epoxy with Cation Exchanged Montmorillonite Clay and Carbon Nanotubes. (open access)

Charge Interaction Effects in Epoxy with Cation Exchanged Montmorillonite Clay and Carbon Nanotubes.

The influence of charge heterogeneity in nanoparticles such as montmorillonite layered silicates (MLS) and hybrid systems of MLS + carbon nanotubes was investigated in cured and uncured epoxy. Epoxy nanocomposites made with cation-exchanged montmorillonite clay were found to form agglomerates near a critical concentration. Using differential scanning calorimetry it was determined that the mixing temperature of the epoxy + MLS mixture prior to the addition of the curing agent critically influenced the formation of the agglomerate. Cured epoxy samples showed evidence of the agglomerate being residual charge driven by maxima and minima in the concentration profiles of thermal conductivity and dielectric permittivity respectively. A hybrid nanocomposite of MLS and aniline functionalized multi walled nanotubes indicated no agglomerates. The influence of environmentally and process driven properties on the nanocomposites was investigated by examination of moisture, ultrasound, microwaves and mechanical fatigue on the properties of the hybrid systems. The results point to the importance of charge screening by adsorbed or reacted water and on nanoparticulates.
Date: May 2005
Creator: Butzloff, Peter Robert
System: The UNT Digital Library
Schools and Schoolmen: Chapters in Texas Education, 1870-1900 (open access)

Schools and Schoolmen: Chapters in Texas Education, 1870-1900

This study examines neglected aspects of the educational history of Texas. Although much emphasis has been placed on the western, frontier aspects of the state in the years after Appomattox, this study assumes that Texas remained primarily a southern state until 1900, and its economic, political, social, and educational development followed the patterns of the other ex-Confederate states as outlined by C. Vann Woodward in his Origins of the New South. This study of the educational history of Texas should aid in understanding such developments for the South as a whole. For the purposes of this study, "education" is defined in terms of institutions specifically created for the formal education of the young. Additionally, the terms "public education" and "private education" are used extensively. It is a contention of this study that the obvious differences between public and private schools in the last half of the twentieth century were not so obvious in the last half of the nineteenth, at least in Texas. Finally, an attempt has been made to confine the study to those areas of formal schooling which are today commonly called primary and secondary, although this was difficult because of the lack of definition used in naming …
Date: May 1974
Creator: Smith, Stewart D.
System: The UNT Digital Library

Phosphorus Retention and Fractionation in Masonry Sand and Light Weight Expanded Shale Used as Substrate in a Subsurface Flow Wetland

Access: Use of this item is restricted to the UNT Community
Constructed wetlands are considered an inefficient technology for long-term phosphorus (P) removal. The P retention effectiveness of subsurface wetlands can be improved by using appropriate substrates. The objectives of this study were to: (i) use sorption isotherms to estimate the P sorption capacity of the two materials, masonry sand and light weight expanded shale; (ii) describe dissolved P removal in small (2.7 m3) subsurface flow wetlands; (iii) quantify the forms of P retained by the substrates in the pilot cells; and (iv) use resulting data to assess the technical and economic feasibility of the most promising system to remove P. The P sorption capacity of masonry sand and expanded shale, as determined with Langmuir isotherms, was 60 mg/kg and 971 mg/kg respectively. In the pilot cells receiving secondarily treated wastewater, cells containing expanded shale retained a greater proportion of the incoming P (50.8 percent) than cells containing masonry sand (14.5 percent). After a year of operation, samples were analyzed for total P (TP) and total inorganic P (TIP). Subsamples were fractionated into labile-P, Fe+Al-bound P, humic-P, Ca+Mg-bound P, and residual-P. Means and standard deviations of TP retained by the expanded shale and masonry sand were 349 + 169 and 11.9 …
Date: August 2002
Creator: Forbes, Margaret G.
System: The UNT Digital Library