Aluminum-humic colloid formation during pre-coagulation for membrane water treatment: Mechanisms and impacts

International audienc

Effect of hydrodynamic diameter on the sieving of waterborne carbon nanotubes by porous membranes

International audienceCarbon nanotubes (CNTs) are rapidly influencing the development and applications of membrane technology for water treatment. Passage of CNTs through membrane pores is becoming a fundamental question to water industries, as the toxicity and environmental fate of waterborne CNTs are largely unknown. This study utilized CNTs and membranes with known properties to investigate the applicability of the Ferry-Renkin sieving equation to the rejection of CNTs by porous membranes. The results demonstrate that the hydrodynamic size of CNTs is more important than their physical dimensions for rejection. Moreover, the classical sieving equation provided reasonable predication of the experimental results. Important for water industries, current membranes used in drinking water treatment should be efficient barriers for waterborne CNTs leached from composite membranes or released from wastewater effluents. Further, process streams containing CNTs may be treated using membrane filtration for CNT recovery. However, micron-pore-size membranes used in previous studies for CNT-membrane fabrication may not be efficient in protecting CNT breakthrough. Since the hydrodynamic diameters of waterborne CNTs are usually above 150 nm, as a general rule of thumb, membranes with pore size smaller than 100 nm need to be used to ensure the safety of CNT membranes

Application of carbon nanotubes or carbon particles onto hollow fiber polymeric materials

Methods for generating carbon mats on the inner surface of hollow fiber membranes are disclosed, along with such modified fiber membranes, and methods of use thereof. A method comprises: providing a plurality of carbon nanotubes and/or carbon particles suspended in a solution to form a suspension; providing one or more polymeric hollow fiber membranes, wherein the one or more polymeric hollow fiber membranes have at least one open end in fluid communication with a lumen, and wherein the lumen defines an inner surface of the one or more polymeric hollow fiber membranes; dispensing the suspension in the at least one open end of the one or more polymeric hollow fiber membranes; and filtering the suspension of carbon nanotubes and/or carbon particles through the one or more polymeric hollow fiber membranes

Carbon nanotube composite membranes for small 'designer' water treatment systems

International audienceSmall water systems that serve fewer than a few thousand persons are often less safe and less sustainable than large drinking water systems due to lack of suitable technologies. This ongoing research aims to develop a novel water treatment technology for small communities. By layering structured, functional carbon nanotubes (CNT) onto low pressure membranes (LPMs), composite membranes were prepared to remove different organic and inorganic contaminants from water, including heavy metals, viruses, natural organic matter, and organic micropollutants. The removal efficiencies varied from over 99.9% (for cadmium) to above 60% (for humic substances). A low-cost CNT formed an antifouling layer that removed membrane foulants by depth filtration, thereby extending the membrane filtration cycle over five-fold. When the CNTs were layered inside hollow fiber membranes, superb backwashable properties were observed, allowing the operation of CNT-modified membranes under full-scale treatment conditions. Moreover, a systematic study of CNT rejection by LPMs found that commercially available LPMs efficiently prevented CNT breakthrough, thus ensuring nanosafety of the treated water. By varying the composition and structure of functional CNT layers, energy-efficient composite membranes may be economically produced for designer water treatment systems and applied in small communities

Nitrogen dioxide pollution exposure is associated with olfactory dysfunction in older U.S. adults

Background: Olfactory dysfunction has profound effects on quality of life, physical and social function, and mortality itself. Nitrogen dioxide (NO2) is a pervasive air pollutant that is associated with respiratory diseases. Given the olfactory nerve\u27s anatomic exposure to airborne pollutants, we investigated the relationship between NO2 exposure and olfactory dysfunction. Methods: The ability to identify odors was evaluated using a validated test in respondents from the National Social Life, Health, and Aging Project (NSHAP), a representative probability sample of home-dwelling, older U.S. adults age 57 to 85 years. Exposure to NO2 pollution was assessed using measurements obtained from the U.S. Environmental Protection Agency (EPA) Aerometric Information Retrieval System (AIRS) ambient monitoring site closest to each respondent\u27s home. We tested the association between NO2 exposure and olfactory dysfunction using multivariate logistic regression. Results: Among older adults in the United States, 22.6% had impaired olfactory function, defined as ≤3 correct (out of 5) on the odor identification test. Median NO2 exposure during the 365 days prior to the interview date was 14.7 ppb (interquartile range [IQR], 10.8 to 19.7 ppb). An IQR increase in NO2 exposure was associated with increased odds of olfactory dysfunction (OR, 1.35; 95% CI, 1.07 to 1.72), adjusting for age, gender, race/ethnicity, education, cognition, comorbidity, smoking, and season of the home interview (n = 1823). Conclusion: We show for the first time that NO2 exposure is associated with olfactory dysfunction in older U.S. adults. These results suggest an important role for NO2 exposure on olfactory dysfunction, and, potentially, nasal disease more broadly