Clostridium difficile-associated diarrhea (CDAD) is the most commonly identified cause of nosocomial diarrhea (10,12,17). The pathogenicity of C. difficile is due to the production of two exotoxins: toxin A, an enterotoxin, and toxin B. Both toxins A and B contribute to human disease (19).TechLab Inc. (Blacksburg, Va.) has recently marketed an enzyme immunoassay, C. DIFF CHEK-60, which detects glutamate dehydrogenase (GDH), a common C. difficile antigen (the assay is hereinafter referred to as TL-GDH), and also markets an enzyme immunoassay, C. difficile Tox A/B II (Tox-A/B), for the detection of toxins A and B. The aim of this study was to evaluate and compare these two assays with another immunoassay, the Triage C. difficile Panel assay (Biosite Diagnostics, San Diego, Calif.), which detects both GDH (TR-GDH) and toxin A (TR-Tox-A); an in-house cytotoxin assay (C-Tox); and stool cultures for C. difficile.All nonformed stool specimens from inpatients suspected of having CDAD were included in the study. Except for stool cultures, all tests were performed within 48 h of the arrival of specimens in the laboratory. Specimens were kept at 4°C if not processed immediately. A portion of stool was stored at Ϫ70°C for subsequent culture. Specimens of insufficient quantity were excluded from all tests.The results of TL-GDH and Tox-A/B were read by using a dual-wavelength spectrometer (450 and 620 nm). TR-GDH, TR-Tox-A, TL-GDH, and Tox-A/B were carried out according to the manufacturer's instruction. Details of the Triage panels and Tox-A/B and C-Tox have been described previously (16).After thawing, fecal samples were planted onto prereduced cycloserine-cefoxitin-fructose agar (cefoxitin, 8 mg/liter; cycloserine, 250 mg/liter; fructose agar; Oxoid, Ottawa, Canada) and incubated for 96 h at 35°C in an anaerobic glove box. Suspected colonies were identified based on their growth on selective media, their colonial morphology, and a positive reaction by the MicroScreen C. difficile latex slide agglutination test (Microgen Bioproducts Ltd., Surrey, United Kingdom) (2, 11).All C. difficile isolates were tested by PCR for the presence of toxin A and B genes by use of primers NK9 and NK11, derived from the repeating portion of toxin A, and NK104 and NK105, derived from the nonrepeating portion of toxin B. These primers have been described by Kato and coworkers (13). The composition of our master mix and the amplification conditions were the same as used by those investigators.For the purpose of this study, a true positive sample was defined as a sample that was positive for toxin A and/or B and from which a toxigenic C. difficile strain (positive by PCR for a toxin gene) was isolated. If a positive toxin detection test result was seen for a sample which was negative for C. difficile by culture or yielded a nontoxigenic strain, the reaction was considered to be falsely positive. Sensitivity, specificity, and positive and negative predictive values for each test were calculated on this basis.C. difficile was isolated from 93 of 49...

Musselwhite Mine in Northwestern Ontario, Canada began thickened tailings disposal in May 2010. Surface disposal of thickened tailings for the 4,000 tpd gold mine was chosen following a series of studies beginning in 2002 to investigate options to expand the capacity of the tailings management area. This technology was considered most cost effective in maximising storage capacity within the existing site footprint. The elimination of a pond for closure will reduce the risk of dam failure. Further, the non-segregating tailings are expected to be relatively impervious and saturated. These characteristics will help inhibit tailings oxidation and reduce the likelihood of acid generating and metals leaching in the long term. Musselwhite Mine is currently planning to remove the sulphide minerals from the tailings stream using a flotation plant. This paper discusses the design of the thickened tailings disposal system and presents preliminary observations on tailings deposition to date. In preparation for thickened tailings disposal the tailings management area was partitioned by an internal dyke in 2008. This has allowed tailings to be 'stacked' using the upstream method of construction in the west cell and the east cell to serve as a water management pond. The cold climate presents a special challenge to operating the thickened tailings system as there is very little precedent experience. The design has incorporated a number of contingency measures to facilitate tailings thickening and deposition in winter. Field data have suggested that the thickened tailings system is performing very well to date. The thickening plant has consistently produced underflow at about 70% solids with minimal attention. The tailings beaches are steeper than expected. The deposited tailings are non-segregating and relatively saturated. The measured in situ dry density of the tailings is higher than expected. The performance of tailings deposition is being closely monitored.

The use of polyacrylamide-based high-molecular-weight polymer addition at the tailings storage facility (TSF) discharge locations has gained considerable interest in recent years. The intended result of implementing this technique is to have tailings slurry release clear water and create a steepened beach, compared to a conventional tailings slurry disposal method. This paper will focus on a study of a typical iron ore project which required improved water recovery. It has been suggested in previous studies that uneven shear on the polymer dosed tailings deposition on the tailings beach may be problematic. In this testing program, tailings and polymer mixture were tested for water release behaviour under partially sheared and fully sheared conditions. It is concluded that varying the shear regime affects the initial water recovery, up to around two hours after mixing and shearing. At the end of the test, the shear regime had less effect on the overall water recovery. A trade-off comparison between conventional slurry surface disposal and in-line polymer addition disposal is also presented in the paper. The trade-off study demonstrates that the in-line polymer addition technology could provide financial water-saving benefit.

With the advent of Energy Resources Conservation Board of Alberta (ERCB) Directive 074, there has been increased pressure on oil sands operators to find practical, field proven solutions to deal with tailings management. While significant research and development has gone into understanding the characteristics of oil sands tailings materials and their subsequent behaviours in the field, there are still uncertainties. All operations will need to dewater their oil sands tailings in some manner to produce a material that will gain strength over time. There is great interest among oil sands companies to investigate and potentially apply different dewatering techniques for surface disposal of their waste materials. This paper presents the highlights of lab and field testing programs that have focused on thickening the multiple tailings streams that are produced by oil sands operators. Each tailings stream has its challenges and these will be discussed in the context of various dewatering methods that have been trialled. In addition, some focus will be put on how to employ these dewatering methodologies to compliment deposition strategies.

INTRODUCTION Rehabilitation is essential in legacy mines as mine hazards do not improve with time; they will always get worse. Most hazard mitigation techniques address immediate risk but do nothing to actually fix the problem. The current impetus is to move away from simply identifying and managing risks and towards long-term solutions that eliminate the hazards in a planned way. This article will describe a proven approach to identify and eliminate hazards in such a way as to preserve the positive legacy of mining while eliminating issues that affect the environment and communities in proximity to legacy mine sites.