Twenty percent of all the material delivered to construction and demolition (C&D) disposal sites in the Province of Nova Scotia, Canada, is waste gypsum wallboard (WGW) (Dillon Consulting Ltd., 2006). This is typically in the form of residential or business demolition waste, which includes WGW from new construction activities. This study looked at the use of papered and de-papered waste gypsum wallboard in compost to evaluate its impact on the process, total heavy metal concentration, bioavailable metal concentration, and movement of heavy metals. The study consisted of three components: a short term mechanical in-vessel compost sub-study to assess the impact of composting WGW; a lysimeter cell sub-study to evaluate potential movement of compost constituents from compost to soil and water under a static compost system open to the ambient environmental conditions; and, a final sub-study to determine the performance of waste gypsum wallboard in compost under controlled composting conditions. The study found that the inclusion of up to 34% (by mass) WGW had no negative effects on the degradation of carbon, final pH, and final electrical conductivity in the compost product, however, WGW-containing composts did increase concentrations of total sulphur. There was the potential for elevated levels of total lead and cadmium but the compost produced was within the CCME Class A guidelines for heavy metal concentration. Waste gypsum wallboard containing composts also had increased levels of bioavailable cadmium compared to non-WGW composts.

Master of Dental Surgery / This work was digitised and made available on open access by the University of Sydney, Faculty of Dentistry and Sydney eScholarship . It may only be used for the purposes of research and study. Where possible, the Faculty will try to notify the author of this work. If you have any inquiries or issues regarding this work being made available please contact the Sydney eScholarship Repository Coordinator - ses@library.usyd.edu.au

Thesis (Ph. D.)--Columbia University, 1937. / Vita. Bibliography: p. 32.

Thesis (M.S.)--University of Wisconsin--Madison, 1968. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Gypsum is produced as a waste product by various industries, e.g. the fertilizer industry, the mining industry and power stations. Gypsum waste disposal sites are responsible for the leaching of saline water into surface and underground water and create airborne dust. Gypsum waste is not only an environmental problem but has measurable economic value as well. However, all these environmental and economical concerns can be avoided should valuable/saleable by-products like sulphur and calcium carbonate be recovered from the low quality gypsum. The aim of this project was to evaluate a process for converting waste gypsum into sulphur. The process evaluated consists of the following stages: reduction of gypsum to calcium sulphide; stripping of the sulphide with CO2 gas and the production of sulphur. Thermal reduction study showed that gypsum can be reduced to CaS with activated carbon in a tube furnace operating at 1100º C. The CaS yield was 96%. The CaS formed was slurried in water. The reaction of gaseous CO2 with the CaS slurry leads to the stripping of sulphide to form H2S gas and the precipitation of CaCO3. The H2S generated was then reacted in the iron (IIII) and PIPco processes to form elemental sulphur. Sulphur with the purity between 96% and 99% was recovered from waste gypsum in this study. / Thesis (PhD)--University of Pretoria, 2009. / Chemistry / unrestricted

Improving productivity of sodic soils has become a concern in North Dakota because of the desire for more land for producing crops. Field and incubation studies were conducted to determine the impacts of different amendments (flue-gas desulfurization gypsum, sugar beet processing by-product lime, and langbeinite) on the chemical and biological properties of two sodic soils. The field study evaluated the amendment effects on the chemical conditions of the soil and the impact on alfalfa yield and quality. Differences were not observed in percent sodium (%Na) in the first 17 months and alfalfa yield was not impacted by the treatments except for the high rate of langbeinite. The incubation study investigated the effects of amendments on both the chemical and biological properties of the soil. Spent lime increased the cumulative respiration but was not impacted by gypsum or langbeinite. Labile carbon (C) was negatively correlated with %Na and electrical conductivity (EC). / North Dakota Soybean Council

Indiana University-Purdue University Indianapolis (IUPUI) / Phosphorus is an essential plant nutrient and an important contributor to the eutrophication of aquatic ecosystems. Studies have shown that gypsum (CaSO4∙H2O) applications can potentially reduce phosphorus export from agricultural fields. Most studies have examined the effect of gypsum application rates on treatment effectiveness, but limited research has been conducted to determine how the timing of gypsum application can affect soil phosphorus mobility and phosphorus leaching. A greenhouse experiment was conducted to address this question and further our understanding of the effect of gypsum addition on soil phosphorus chemistry. For the experiment, two soil types with different background phosphorus levels (low P, high P), and three different time intervals between gypsum and phosphorus fertilizer application (2, 28 and 56 days) were applied. A total of 18 soil columns (L: 15 cm; diam: 10 cm) packed with sieved soil were treated with gypsum (3.9 g) and separated into three sets corresponding to each of the phosphorus application times. An equal number of columns not treated with gypsum were also included to serve as controls. Phosphorus fertilizer (0.34 mg P cm-1) was added as KH2PO4 solution. Rainwater (58 mL) was applied every 2-4 days to generate leachate that was collected and analyzed for ortho-P, total P, and SO4-2. At the end of each time series, the set of soil columns were sliced into 2-4 cm increments, and water extractable and bicarbonate extractable phosphorus (Olsen-P) was determined to examine downward phosphorus movement. Results of the study showed that Olsen-P levels were not affected by the gypsum treatment, indicating no interference of gypsum treatment with the P-supplying capacity of soils. The gypsum treatment reduced water-extractable P levels in the high-P soil, but treatment effect was not significant in the low-P soil. Likewise, in the high-P soil, gypsum treatment resulted in leachate ortho-P reduction during the second and third period of collection. For the low-P soil, there was no significant reduction in ortho-P. Overall, these results indicated that the beneficial effect of gypsum on phosphorus export from agricultural fields is dependent on soil-P status and time interval between gypsum amendment and P fertilizer application.

No description available.

3 pp. / Gypsum can help stabilize aggregate structure in some soils.

Revised; Originally Published 2006 / 5 pp.