The use of pure oxygen for aeration in aerobic wastewater treatment: A review of its potential and limitations.

In aerobic wastewater treatment, aeration is the most critical element of the treatment system. It supplies microorganisms with the required dissolved oxygen, maintains solids in suspension and, in membrane bioreactors, it controls fouling. However, conventional activated sludge is limited to the treatment of low strength wastewaters, as higher loadings require both higher biomass and higher dissolved oxygen concentrations. By replacing air with pure oxygen, oxygen transfer rates increase at lower flowrates. In this work, the potential and limitations of pure oxygen aeration are reviewed. The effect of the system's operational parameters and the mixed liquor characteristics on oxygen transfer, and vice versa, are determined. Pure oxygen treats higher loadings without compromising effluent quality. Fine bubbles are more efficient in oxygen transfer due to their increased contact area. However, pure oxygen is not always essential, so it is recommended to be restricted to applications where air is not adequate.

Life cycle assessment of nutrient removal technologies for the treatment of anaerobic digestion supernatant and its integration in a wastewater treatment plant.

The supernatant resulting from the anaerobic digestion of sludge generated by wastewater treatment plants (WWTP) is an attractive flow for technologies such as partial nitritation-anammox (CANON), nitrite shortcut (NSC) and struvite crystallization processes (SCP). The high concentration of N and P and its low flow rate facilitate the removal of nutrients under more favorable conditions than in the main water line. Despite their operational and economic benefits, the environmental burdens of these technologies also need to be assessed to prove their feasibility under a more holistic perspective. The potential environmental implications of these technologies were assessed using life cycle assessment, first at pilot plant scale, later integrating them in a modeled full WWTP. Pilot plant results reported a much lower environmental impact for N removal technologies than SCP. Full-scale modeling, however, highlighted that the differences between technologies were not relevant once they are integrated in a WWTP. The impacts associated with the WWTP are slightly reduced in all categories except for eutrophication, where a substantial reduction was achieved using NSC, SCP, and especially when CANON and SCP were combined. This study emphasizes the need for assessing wastewater treatment technologies as part of a WWTP rather than as individual processes and the utility of modeling tools for doing so.

Environmental and economic profile of six typologies of wastewater treatment plants.

The objective of wastewater treatment plants (WWTPs) is to prevent pollution. However, it is necessary to assess their sustainability in order to ensure that pollution is being removed, not displaced. In this research, the performance of 24 WWTPs has been evaluated using a streamlined Life Cycle Assessment (LCA) with Eutrophication Potential (EP) and Global Warming Potential (GWP) as environmental indicators, and operational costs as economic indicators. WWTPs were further classified in six typologies by their quality requirements according to their final discharge point or water reuse. Moreover, two different functional units (FU), one based on volume (m(3)) and the other on eutrophication reduction (kg PO(4)(3-) removed) were used to further determine sustainability. A correlation between legal requirements and technologies used to achieve them was found: Organic matter removal plants were found to be less costly both in environmental and economic terms if volume was used as the functional unit, while more demanding typologies such as reuse plants showed a trade-off between lower EP and higher cost and GWP; however, this is overcome if the second FU is used instead, proving the sustainability of these options and that this FU better reflects the objectives of a WWTP.

Hipertricosis cubital o síndrome del codo piloso / Hypertrichosis cubiti (hairy elbow syndrome)

La hipertricosis cubital, o síndrome del codo piloso, es una afección rara, con una repercusión fundamentalmente estética, aunque en la mitad de los casos descritos se ha asociado a otras malformaciones. Se describe el caso de un paciente de 6 años de edad, con un aumento de vello en las superficies extensoras de las extremidades superiores, diagnosticado de hipertricosiscubital. Asimismo, se comentan diferentes aspectos de esta entidad tan poco conocida (AU)

Hypertrichosis cubiti, or hairy elbow syndrome, is a rare disease with fundamentally esthetic repercussion although in half of the described cases other malformations have been associated. We describe the case of a six years old patient with an increase of localized hair in superficial extensors of upper extremities, diagnosed of hypertrichosis cubiti. Different aspects of this little-known syndrome are commented (AU)

Macroamilasemia en pediatría / Macroamylasemia in paediatrics

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Síndrome diarreico prolongado debido a la administración de carbamacepina / Prolonged syndrome of diarrhoea due to the administration of carbamazepine

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¿Onda hipervoltada en el potencialevocado auditivo de tallo cerebral? / Can hypervoltage waves exist in brain stem auditory evoked potentials?

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[Frequency of intestinal and bacterial parasites producing diarrhea in children in a regional hospital]. / Frecuencia de parásitos intestinales y bacterias productoras de diarrea en niños de un hospital de zona.

The diarrhoea diseases are priority health problems in all countries of the Third World. The number of the cases of diarrhoea and other intestinal infections have very high morbi-mortality rate in mexican childhood. There are many factors that affect these pathologies, those related to social, economic and cultural aspects seem to be the most important. Although the intestinal viruses are frequent, the enteritis produced by bacteria are more severe and acute. There area also parasites that yield the chronic type disease. In this paper, the most frequent parasites and enteropathogenic bacteria infecting children below 15 years old, either hospitalized or being outpatients from the Hospital de Zona No. 29 del IMSS in México City, were studied. The data obtained were related to the socioeconomic level. A total of 415 stool samples were collected from newborn to 14 years old children over a period of nine months. The samples were classified according to the ages, schooling and number of persons who slept with the child in the same bedroom. The samples were examined by a centrifugal concentration technique and by cultivation. The group of children up to five years old were found to be the most infected by bacteria, while children from 10 to 14 years old were by parasites. Those children whose parents either have not finished the elementary school or can not read and write were the most parasitized (40%), these children were also found to be most infected, as the number of persons who slept in the same bedroom increased, the number of infections per children either by bacteria or parasites, also increased.(ABSTRACT TRUNCATED AT 250 WORDS)