Mine Water as a Resource: Selective Removal and Recovery of Trace Antimony from Mine-Impacted Water

The objective of this study was to evaluate the feasibility of combined modular processes to selectively remove Sb from mine-impacted waters in an Arctic environment in order to fulfil local environmental criteria for discharged waters. Novel ion exchange, selective extraction and ultrafiltration, electrocoagulation, and dissolved air flotation technologies were investigated, individually or in combination, from the laboratory- to pilot-demonstration scale. Laboratory-scale testing using Fe₂(SO₄)₃ precipitation, ion exchange resin, selective ion extraction and ultrafiltration, and electrocoagulation with or without subsequent dissolved air flotation indicated that any of the methods are potentially applicable to Sb removal from mine water. The observed differences between Sb and As removal efficiency by ion exchange resin illustrated the need for Sb-specific removal and recovery technologies. Techno-economic analyses showed that treatment of mine water using electrocoagulation-dissolved air flotation yields the lowest comparative life-cycle cost of examined technologies. Results demonstrated increased Sb attenuation efficiency using either electrocoagulation-dissolved air flotation or selective extraction and ultrafiltration, even when treating only 50% of the mine-impacted water, compared with conventional Fe₂(SO₄)₃ precipitation from mine water. Additional investigation is necessary to characterize the long-term stability of the mineral phases in Sb-containing solid residues and to inform selection of Sb recovery methods and utilisation or final disposal options for the residual materials.

     

The salmon-peloton: Hydraulic habitat shifts of adult Atlantic salmon (Salmo salar) due to behavioural thermoregulation

In recent decades, there has been an increase in conservation and restoration projects targeting Atlantic salmon (Salmo salar – AS), as populations in eastern Canada decline. Missing however, is an understanding of thermo-hydraulic habitat use by adult AS during summer, and thus the actual benefits of altering in-river physical structures. Here, we illustrated how optical and thermal infrared (TIR) imagery acquired from a UAV can be used in concert with in-situ depth and velocity data to map adult AS and develop models of thermo-hydraulic habitats in the Miramichi River, New Brunswick. We found during normal temperature conditions (<19°C) boulder proximity, depth, velocity, and Froude number, a non-dimensional hydraulic metric, were key parameters that characterized adult AS habitat. However, during behavioural thermoregulation events (>19°C), proximity to the cool thermal plume and Froude number were critical controls on habitat use. We also observed AS forming a distinct geometric formation during behavioural thermoregulation events, and term this formation a “thermal-peloton”; in reference to competitive cycling in which groups of cyclists pack together. The primary function of the peloton is undoubtedly to reduce thermally induced stressed; however, we conceptualize that the geometry of the peloton attenuates hydraulic-drag, and reduces the energetic expenditure of individuals practicing behavioural thermoregulation. These data provide a blue print for Atlantic salmon restoration work. The use of UAV-based sensors has the potential to initiate a paradigm shift for river sciences.     

Interannual variation in spawning success of striped bass (Morone saxatilis) in the Saint John River,New Brunswick

Barriers such as dams have been cited as a serious threat to striped bass survival, especially when they affect or impede migration and access to spawning grounds. On the Saint John River, New Brunswick, the installation of the large Mactaquac Dam in the immediate vicinity of a historic striped bass spawning location was suspected to have caused the arrest of striped bass reproduction and the collapse of the native striped bass population. In 2014, juvenile striped bass of confirmed Saint John River origin were documented in the river for the first time since 1979. In the current study, we examined juveniles from 6 years of sampling to determine corresponding years of successful recruitment. We also tracked adult striped bass matching the ancestry of native Saint John River juveniles to determine the timing and location of spawning. Over 5 years, we observed an annual upstream migration by adult striped bass to historic spawning areas near Fredericton, identified a dominant year class of Saint John River origin juveniles reproduced in 2013, and linked the apparent successful production of year classes to definable discharge conditions, that is, extended periods of sustained flow >36 hr downstream from the Mactaquac Dam. The results of this study suggest important first management actions towards recovering and sustaining the re‐discovered striped bass population in the Saint John River, New Brunswick.     

Transesterification of trimethylolpropane and rapeseed oil methyl ester to environmentally acceptable lubricants

Biodegradable trimethylolpropane [2-ethyl-2-(hydroxymethyl)-1,3-propanediol] esters of rapeseed oil fatty acids were synthesized by transesterification with rapeseed oil methyl ester both by enzymatic and chemical means, both in bench and pilot scales. Nearly complete conversions were obtained with both techniques. A reduced pressure of about 2 to 5 kPa, to remove the methanol formed during transesterification, was critical for a high product yield. The quantity of added water was also critical in the biocatalysis. Candida rugosa lipase was used as biocatalyst and an alkaline catalyst in chemical transesterifications. In biocatalysis the maximum total conversion to trimethylolpropane esters of up to 98% was obtained at 42°C, 5.3 kPa, and 15% added water. The maximum conversion of about 70% to the tri-ester was obtained at the slightly higher temperature of 47°C. The reaction time was longer in the biocatalysis, but considerably higher temperatures were required in chemical synthesis. In the chemical synthesis tri-ester yields increased when the temperature was first held at 85 to 110°C for 2.5 h and subsequently increased to up to 120°C for 8 h. The trimethylolpropane esters obtained were tested as biodegradable hydraulic fluids and compared to commercially available hydraulic oils. The hydraulic fluids based on trimethylolpropane esters of rapeseed oil had good cold stability, friction and wear characteristics, and resistance against oxidation at elevated temperatures.     

TUTWLAN – QoS Supporting Wireless Network

Quality of Service (QoS) support has generally been lacking from WPAN and WLAN technologies, which has motivated the research of TUTWLAN. Design objectives have been relatively simple network architecture and capability to support real time services ranging from sensor data to multimedia streaming. The main TUTWLAN entities for QoS support are the Medium Access Control (MAC) protocol called TUTMAC and TUTWLAN Access Point (AP). The channel access is based on dynamic reservation Time Division Multiple Access (TDMA). TUTWLAN is shown to be suitable for wireless home and office applications. It provides flexibility, interoperability and availability of services exceeding the recent QoS proposals that has been accounted at the standardisation bodies for standard wireless technologies. This revised version was published online in September 2006 with corrections to the Cover Date.     

Economic Geography of Knowledge-Intensive Technology Clusters: Lessons from the Helsinki Metropolitan Area

This paper analyzes industrial clusters in the Helsinki Metropolitan Area (HMA) in Finland. The HMA is the largest and most powerful concentration of population and economic activity in Finland. The paper analyzes knowledge-intensive industrial clusters and their structures. Clusters are identified according to a statistical analysis that provides a systematic perspective on the knowledge-intensive economic geography of the HMA. There are two main questions: how diverse are the identified clusters in terms of their internal structure; and, are there spatial irregularities identifiable in these structures? Knowledge-intensive clusters are strongly localized close to the infrastructural nodes: their physical localization is closely linked to road- and rail-structures and terminals. In general, clusters become smaller as their distance to the center of Helsinki increases: distance decay is evidently present. Our findings indicate that clusters are plural entities and their diversities do not follow a clearly identifiable pre-determined logic. Knowledge-based industries focusing on immaterial products tend to have closer central proximity than other industries but variations are extensive. This cluster diversity indicates that the HMA has a threshold for manifesting agglomeration gains that generate and extend industrial diversities within key clusters. The most diverse clusters tend to be located in the urban core, whereas the more narrowly focused clusters may be found in relatively peripheral locations.     

Increased Lifetime for Biomass and Waste to Energy Power Plant Boilers with HVOF Coatings: High Temperature Corrosion Testing Under Chlorine-Containing Molten Salt

Heat exchanger surfaces of waste to energy and biomass power plant boilers experience often severe corrosion due to very aggressive components in the used fuels. High velocity oxy-fuel (HVOF) coatings offer excellent protection for boiler tubes against high temperature corrosion due to their high density and good adherence to the substrate material. Several thermal spray coatings with high chromium content were sprayed with HVOF technique. Their mechanical properties and high temperature corrosion resistance were tested and analyzed. The coating materials included NiCr, IN625, Ni-21Cr-10W-9Mo-4Cu, and iron-based partly amorphous alloy SHS9172 (Fe-25Cr-15W-12Nb-6Mo). High temperature corrosion testing was performed in NaCl-KCl-Na₂SO₄ salt with controlled H₂O atmosphere at 575 and 625 °C. The corrosion test results of the coatings were compared to corrosion resistance of tube materials (X20, Alloy 263 and Sanicro 25).     

The Preparation of Barium Hexaferrite Coatings Using HVOF

Thick coatings of barium hexaferrite with the compositions BaFe₁₂O₁₉ and BaCoTiFe₁₀O₁₉ were prepared using high-velocity oxygen-fuel (HVOF) spraying technology. Nanocrystalline precursors embedded in an amorphous matrix were obtained on both Fe and glass–ceramic substrates. To promote the crystallization of the hexaferrites, the coatings were annealed at 800°–1000°C, and single-phase coatings were obtained at 1000°C. The crystallization process was studied with X-ray powder diffraction and with electron microscopy. The magnetic measurements of the coatings were carried out in a static field and at high frequencies. The magnetization of the coatings increased with the annealing temperature to above 50 emu/g for both compositions. The coercivity of BaFe₁₂O₁₉ increased with the annealing temperature to above 2400 Oe, whereas the coercivity of BaCoTiFe₁₀O₁₉ decreased from over 800 Oe, for the as-deposited sample, to 400 Oe for the sample annealed at 1000°C. A minimum 90% absorption was calculated for the BaFe₁₂O₁₉ coatings with thicknesses of 0.15–0.25 mm at around 47 GHz and for the 1–4-mm-thick coatings of BaCoTiFe₁₀O₁₉ at 3–9 GHz.