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    ABSTRACT: Hydraulic fracturing (HF), a method to enhance oil and gas production, has become increasingly common throughout the U.S. As such, it is important to characterize the chemicals found in HF fluids to evaluate potential environmental fate, including fate in treatment systems, and human health impacts. Eighty-one common HF chemical additives were identified and categorized according to their functions. Physical and chemical characteristics of these additives were determined using publicly available chemical information databases. Fifty-five of the compounds are organic and twenty-seven of these are considered readily or inherently biodegradable. Seventeen chemicals have high theoretical chemical oxygen demand and are used in concentrations that present potential treatment challenges. Most of the HF chemicals evaluated are non-toxic or of low toxicity and only three are classified as Category 2 oral toxins according to standards in the Globally Harmonized System of Classification and Labeling of Chemicals; however, toxicity information was not located for thirty of the HF chemicals evaluated. Volatilization is not expected to be a significant exposure pathway for most HF chemicals. Gaps in toxicity and other chemical properties suggest deficiencies in the current state of knowledge, highlighting the need for further assessment to understand potential issues associated with HF chemicals in the environment.
    Journal of Hazardous Materials 04/2014; 275C:37-54. · 4.33 Impact Factor
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    ABSTRACT: Hydraulic fracturing (HF), a method to enhance oil and gas production, has become increasingly common throughout the U.S. As such, it is important to characterize the chemicals found in HF fluids to evaluate potential environmental fate, including fate in treatment systems, and human health impacts. Eighty-one common HF chemical additives were identified and categorized according to their functions. Physical and chemical characteristics of these additives were determined using publicly available chemical information databases. Fifty-five of the compounds are organic and twenty-seven of these are considered readily or inherently biodegradable. Seventeen chemicals have high theoretical chemical oxygen demand and are used in concentrations that present potential treatment challenges. Most of the HF chemicals evaluated are non-toxic or of low toxicity and only three are classified as Category 2 oral toxins according to standards in the Globally Harmonized System of Classification and Labeling of Chemicals; however, toxicity information was not located for thirty of the HF chemicals evaluated. Volatilization is not expected to be a significant exposure pathway for most HF chemicals. Gaps in toxicity and other chemical properties suggest deficiencies in the current state of knowledge, highlighting the need for further assessment to understand potential issues associated with HF chemicals in the environment.
    Journal of Hazardous Materials. 01/2014; 275:37–54.
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    ABSTRACT: Anaerobic digestion of manure and other agricultural waste streams with subsequent energy production can result in more sustainable dairy operations; however, importation of digester feedstocks onto dairy farms alters previously established carbon, nutrient, and salinity mass balances. Salt and nutrient mass balance must be maintained to avoid groundwater contamination and salination. To better understand salt and nutrient contributions of imported methane-producing substrates, a mass balance for a full-scale dairy biomass energy project was developed for solids, carbon, nitrogen, sulfur, phosphorus, chloride, and potassium. Digester feedstocks, consisting of thickened manure flush-water slurry, screened manure solids, sudan grass silage, and feed-waste, were tracked separately in the mass balance. The error in mass balance closure for most elements was less than 5%. Manure contributed 69.2% of influent dry matter while contributing 77.7% of nitrogen, 90.9% of sulfur, and 73.4% of phosphorus. Sudan grass silage contributed high quantities of chloride and potassium, 33.3% and 43.4%, respectively, relative to the dry matter contribution of 22.3%. Five potential off-site co-digestates (egg waste, grape pomace, milk waste, pasta waste, whey wastewater) were evaluated for anaerobic digestion based on salt and nutrient content in addition to bio-methane potential. Egg waste and wine grape pomace appeared the most promising co-digestates due to their high methane potentials relative to bulk volume. Increasing power production from the current rate of 369 kW to the design value of 710 kW would require co-digestion with either 26800 L d(-1) egg waste or 60900 kg d(-1) grape pomace. However, importation of egg waste would more than double nitrogen loading, resulting in an increase of 172% above the baseline while co-digestion with grape pomace would increase potassium by 279%. Careful selection of imported co-digestates and management of digester effluent is required to manage salt and nutrient mass loadings and reduce groundwater impacts.
    Journal of Environmental Management 06/2013; 128C:233-242. · 3.06 Impact Factor
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    ABSTRACT: As the world’s population and demand for fresh water increases, new water resources are needed. One commonly overlooked aspect of the water cycle is fog, which is an important part of the hydrology of coastal, high-altitude, and forested regions. Fog water harvesting is being investigated as a sustainable alternative water resource for drinking water and reforestation. Fog water harvesting involves using mesh nets to collect water as fog passes through them. The materials of these nets, along with environmental factors such as wind speed, influence the volume of water collected. In this article, a review of current models for fog collection, designs, and applications of fog water harvesting is provided. Aspects of fog water harvesting requiring further research and development are identified. In regions with frequent fog events, fog water harvesting is a sustainable drinking water resource for rural communities with low per capita water usage. However, an analysis of fog water harvesting potential for the coastal areas of northern California (USA) showed that fog yields are too small for use as domestic water in areas with higher household water demands. Fog water shows particular promise for application in reforestation. Fog water irrigation can increase growth rates and survivability of saplings in reforestation efforts in regions with frequent fog events. Using fog collectors, denuded areas once dependent on natural fog drip can be restored, benefiting local hydrology and ecosystem recovery. Improvement in fog collector designs, materials, and models to increase collection efficiency, perhaps by inclusion of ideas from natural systems, will expand the regions where fog harvesting can be applied.
    Clean Technologies and Environmental Policy 02/2013; · 1.83 Impact Factor

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