3 research outputs found
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Multiscale Investigation of Acid Mine Drainage: the Effect of Organic Carbon Cycling on Microbial Activity and Pyrite Oxidation
Acid mine drainage (AMD) generation from abandoned waste rock piles is a serious environmental problem. One proposed solution is the use of organic carbon to bring about biogeochemical changes that can slow down AMD. The growth of mine waste rock enrichments on a glucose substrate was studied in batch cultures and a monod kinetic model was developed. Various concentrations of soluble microbial products (SMPs) of these enrichments were studied for their interaction with ferric iron and the resulting effect on pyrite oxidation. Four Waste rock packed columns were run in series and the chemical and biological indicators of interest measured for the rock pore liquid and column bulk liquid effluent. The growth experiment results gave a maximum specific growth rate of 0.13 ± 0.01 (1/hr). The enrichments were able to grow from pH 1.6 to 6.0 and had a pH optimum between 2.5 and 3.0. A dissolved oxygen half saturation constant of 0.11 ± 0.05 mg/l was obtained indicating the high sensitivity of the organisms to oxygen. SMPs were able to reduce the pyrite oxidation rate by up to 90% with lysis derived SMPs having a much higher impact than growth derived SMPs for an equivalent SMP-DOC (dissolved organic carbon). A mathematical relationship was developed to predict the rate of pyrite oxidation given an SMP-DOC concentration. The column experiments showed that rock pores contain up to 16 times higher iron and sulfate concentrations compared to column bulk liquid effluents. These and other microbial evidence suggest high pyrite oxidation rate is maintained at rock pores and that bulk liquid effluent concentrations are controlled by diffusional exchange with rock pores as indicated by a tracer test. Results of the growth and SMP-ferric iron interaction study can be incorporated to AMD models and used to predict remediation effects of carbon addition. Waste rock AMD generation results can be used as preliminary guides to design efficient carbon delivery schemes to reactive sites of waste rock piles
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Solar Thermal Processing to Disinfect Human Waste
Almost half of the world’s population is living without access to sanitation services that are safe, reliable, and minimize public health risk of human waste exposure. Modern flush-based sanitation networks are unsustainable: substantial resources, namely water and fuel, are required to bring human waste to centralized treatment facilities. Moving toward sustainable sanitation requires the implementation of innovative renewable energy technologies for stabilization and disinfection of waste, at the local or household scale, where minimal inputs of water, electricity or chemicals are required. A novel solar thermal disinfection toilet prototype has been constructed and is assessed for overall solar to receiver efficiency in treating waste without electrical, chemical, or water inputs from municipal supply. The measured solar to receiver efficiency is 28%, incorporating the capturing and concentration of sunlight and transmission of the energy to the receiver. For a typical sunny day, the current system can achieve thermal treatment of 0.8 kg human waste in roughly 100 min. The novel toilet is available for any location in the world with sufficient sunlight and irradiance data, and is scalable by adding solar collectors for sizes from single dwellings to communities.
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Solar Thermal Processing to Disinfect Human Waste
Almost half of the world’s population is living without access to sanitation services that are safe, reliable, and minimize public health risk of human waste exposure. Modern flush-based sanitation networks are unsustainable: substantial resources, namely water and fuel, are required to bring human waste to centralized treatment facilities. Moving toward sustainable sanitation requires the implementation of innovative renewable energy technologies for stabilization and disinfection of waste, at the local or household scale, where minimal inputs of water, electricity or chemicals are required. A novel solar thermal disinfection toilet prototype has been constructed and is assessed for overall solar to receiver efficiency in treating waste without electrical, chemical, or water inputs from municipal supply. The measured solar to receiver efficiency is 28%, incorporating the capturing and concentration of sunlight and transmission of the energy to the receiver. For a typical sunny day, the current system can achieve thermal treatment of 0.8 kg human waste in roughly 100 min. The novel toilet is available for any location in the world with sufficient sunlight and irradiance data, and is scalable by adding solar collectors for sizes from single dwellings to communities