Evaluation of membrane bioreactor process capabilities to meet stringent effluent nutrient discharge requirements.

A six-stage membrane bioreactor (MBR) pilot plant was operated to determine and demonstrate the capability of this process to produce a low-nutrient effluent, consistent with the nutrient reduction goals for the Chesapeake Bay. Biological nitrogen removal was accomplished using a multistage configuration with an initial anoxic zone (using the carbon in the influent wastewater), an aerobic zone (where nitrification occurred), a downstream anoxic zone (where methanol was added as a carbon source), and the aerated submerged membrane zone. The capability to reliably reduce effluent total nitrogen to less than 3 mg/L as nitrogen (N) was demonstrated. A combination of biological (using an initial anaerobic zone) and chemical (using alum) phosphorus removal was used to achieve effluent total phosphate concentrations reliably less than 0.1 mg/L as phosphorus (P) and as low as 0.03 mg/L as P. Alum addition also appeared to enhance the filtration characteristics of the MBR sludge and to reduce membrane fouling. Aeration of the submerged membranes results in thickened sludge with a high dissolved oxygen concentration (approaching saturation), which can be recycled to the main aeration zone rather than to an anoxic or anaerobic zone to optimize biological nutrient removal. Biological nutrient removal was characterized using the International Water Association Activated Sludge Model No. 2d. The stoichiometry of chemical phosphorus removal was also consistent with conventional theory and experience. The characteristics of the solids produced in the MBR were compared with those of a parallel full-scale conventional biological nitrogen removal process and were generally found to be similar. These results provide valuable insight to the design and operating characteristics of MBRs intended to produce effluents with very low nutrient concentrations.     

Industrial sources influence air concentrations of hydrogen sulfide and sulfur dioxide in rural areas of western Canada

A survey of monthly average concentrations of sulfur dioxide (SO2) and hydrogen sulfide (H2S) at rural locations in western Canada (provinces of Alberta, British Columbia, and Saskatchewan) was conducted in 2001-2002, as part of an epidemiological study of the effects of oil and gas industry emissions on the health of cattle. Repeated measurements were obtained at some months and locations. We aimed to develop statistical models of the effect of oil and gas infrastructure on air concentrations. The regulatory authorities supplied the information on location of the different oil and gas facilities during the study period and, for Alberta, provided data on H2S content of wells and flaring volumes. Linear mixed effects models were used to relate observed concentrations to proximity and type of oil and gas infrastructure. Low concentrations were recorded; the monthly geometric mean was 0.1-0.2 ppb for H2S, and 0.3-1.3 ppb for SO2. Substantial variability between repeated measurements was observed. The precision of the measurement method was 0.005 ppb for both contaminants. There were seasonal trends in the concentrations, but the spatial variability was greater. This was explained, in part, by proximity to oil/gas/bitumen wells and (for SO2) gas plants. Wells within 2 km of monitoring stations had the greatest impact on measured concentrations. For H2S, 8% of between-location variability was explained by proximity to industrial sources of emissions; for SO2 this proportion was 18%. In Alberta, proximity to sour gas wells and flares was associated with elevated H2S concentrations; however, the estimate of the effect of sour gas wells in the immediate vicinity of monitoring stations was unstable. Our study was unable to control for all possible sources of the contaminants. However, the results suggest that oil and gas extraction activities contribute to air pollution in rural areas of western Canada.     

Air pollution inhalation during acute exercise is dependent of the body mass index and ventilation of young men

Environmental Science and Pollution Research - Obesity and physical inactivity threaten human health, and both could be solved with exercise. However, a higher amount of pollutants is inhaled...     

Effects of propanil, tebufenozide and mefenacet on growth of four freshwater species of phytoplankton: a microplate bioassay

The Albufera Natural Park situated in Valencia (Spain), with a very rich flora and fauna is surrounded by rice fields in which pesticide spraying is a regular practice. With this in mind, the sensitivity of four algal species, Scenedesmus acutus, Scenedesmus subspicatus, Chlorella vulgaris and Chlorella saccharophila to pesticides propanil, tebufenozide and mefenacet was studied using single species toxicity tests. Organisms were exposed to different concentrations of these herbicides and the algal growth was measured in a microplate reader at 410 nm, at 0, 24, 48 and 72 h. Tebufenozide appeared to be the most inhibitory to Scenedesmus and Chlorella species growth. 72 h EC50 of propanil, tebufenozide and mefenacet ranged from 0.29 to 5.98 mg/l, 0.12 to 0.15 mg/l and from 0.25 to 0.67 mg/l, respectively for the four algal species. The two species of Chlorella were more tolerant than the two species of Scenedesmus.     

Rhizosphere localized cationic peroxidase from barley roots is strongly activated by cadmium and correlated with root growth inhibition

The activity of Cd-induced POD isozyme isolated from the surface of intact barley roots growing under some abiotic stress conditions (toxic metals: Al, Co, Cu, Hg; drought, NaCl, extreme temperatures: heat, cold) and compounds activating (2,4-D) or inhibiting (SHAM) POD activity as well as H(2)O(2) and H(2)O(2) scavenger (DTT) was characterized. Strong Cd concentration-dependent accumulation of one cationic POD isozyme was observed on PAGE, which correlated with Cd- and other stress induced root growth inhibition. This isoPOD is basic with isoelectric point about 9 and its localization is restricted only to the apical part of the barley root tip.     

Ozone Air Quality over North America: Part I—A Review of Reported Trends

ABSTRACT

Ozone and precursor trends can be used to measure the effectiveness of regulatory programs that have been implemented. In this paper, we review trends in the concentrations of O₃, NO_x, and HCs over North America that have been reported in the literature. Although most existing trend studies are confounded by meteorological variability, both the raw data trends and the trends adjusted for meteorology collectively indicate a general decreasing trend in O concentrations in most areas of the United States during 1985-1996. In Canada, mean daily maximum 1-hr O₃ concentrations at urban sites show mixed trends with a majority of sites showing an increase from 1980 to 1993. Mean daily maximum 1-hr O₃ at most regionally representative Canadian sites appears to decrease from 1985 to 1993 or shows no significant change. There are far fewer data and analyses of NO_x and HC trends. Available studies covering various ranges of years indicate decreases in ambient NO_x and HC concentrations in Los Angeles, CA, decreases in HC concentrations in northeastern U.S. cities, and decreases in NO concentrations in Canadian cities. Two key needs are long-term HC and NO_x measurements, particularly at rural sites, and a systematic comparison of trend detection techniques on a reference data set.     

Modeling of the long-term tropospheric trends of hydroxyl radical for the Northern Hemisphere

The MGO 2D (altitude–longitude) channel photochemical transport model has been applied to elucidate the spatial and temporal behavior of the hydroxyl radical in the troposphere of the northern temperate belt for the pre-industrial (1850) period and the last few decades (1960 and 1995). The relation between the tropospheric OH content and the carbon monoxide, methane, nitrogen oxides emissions during 1850–1995 is studied. The distribution of the carbon monoxide concentration is calculated and validated using the observational data collected in the different locations because of the geographical non-homogeneity of its emissions. The response of the hydroxyl radical concentrations to the non-homogeneity of the CO and other atmospheric species distribution is estimated. The carbon monoxide and methane contributions to the hydroxyl photochemical sink are also evaluated. Because the changes of OH in the troposphere alternate the intensity of methane and carbon monoxide oxidation, the CO, CH₄ and OH lifetime evolution due to the increase of anthropogenic pollution intensity is analyzed and discussed.     

Toxicity Identification Evaluation (Phase I) of water and sediment samples from a tropical reservoir contaminated with industrial and domestic effluents

The Funil Reservoir (Rio de Janeiro State, Brazil) is an environment degraded by constant discharge of nutrients and pollution coming from the most industrialized region of the country. As a consequence of eutrophication, there are continuous cyanobacteria blooms, which cause acute and chronic toxicity to zooplankton. In this context, Phase I of Toxicity Identification Evaluation (TIE) was performed on Daphnia similis using water and interstitial water from the reservoir, with the aim of identifying classes of compounds responsible for toxicity. The results indicated that water toxicity was due to cyanobacteria resulting from blooms in the reservoir and surfactants. Metals, especially copper, contributed to sediment toxicity. This research is the first attempt to describe the nature of toxicity in this reservoir using this method.     

An Approach to Multi-criteria Environmental Evaluation with Multiple Weight Assignment

In the domain of environmental protection, multi-criteria evaluation is used in cases where multiple alternatives, on the bases of multiple parameters, need to be evaluated. Depending on the particular goal of investigation, various approaches have been developed and applied. This various multi-criteria approaches differ in parameter weighting method, in data normalization method as well as in the method for assessment of alternatives. According to the applied multi-criteria methodology, the result, i.e., the rank of alternatives may differ to some extent. In this context, parameter weighting bears special significance in multi-criteria evaluation, while the choice of method is crucial for final result. The specificity of parameter weighting process in environment protection is directly related to pronounced interdisciplinary character of this area, as well as the large number of influential parameters. With this in mind, this paper presents an approach to multi-criteria evaluation which—through integration of three specific methods for parameter weighting—allows more flexible and multi-purpose application. Based on the established concept, a software application was developed. Besides automated parameter weighting, it also provides graphical interpretation of results. The developed approach and software have been verified on the case study related to evaluation of environmental loadings at six locations in the city of Novi Sad.