Nitrogen management in bioreactor landfills

One scenario for long-term nitrogen management in landfills is ex situ nitrification followed by denitrification in the landfill. The objective of this research was to measure the denitrification potential of actively decomposing and well decomposed refuse. A series of 10-l reactors that were actively producing methane were fed 400 mg NO3-N /l every 48 h for periods of 19-59 days. Up to 29 nitrate additions were either completely or largely depleted within 48 h of addition and the denitrification reactions did not adversely affect the leachate pH. Nitrate did inhibit methane production, but the reactors recovered their methane-producing activity with the termination of nitrate addition. In well decomposed refuse, the nitrate consumption rate was reduced but was easily stimulated by the addition of either acetate or an overlayer of fresh refuse. Addition of acetate at five times the amount required to reduce nitrate did not lead to the production of NH4+ by dissimilatory nitrate reduction. The most probable number of denitrifying bacteria decreased by about five orders of magnitude during refuse decomposition in a reactor that did not receive nitrate. However, rapid denitrification commenced immediately with nitrate addition. This study shows that the use of a landfill as a bioreactor for the conversion of nitrate to a harmless byproduct, nitrogen gas, is technically viable.     

Decomposition of forest products buried in landfills

The objective of this study was to investigate the decomposition of selected wood and paper products in landfills. The decomposition of these products under anaerobic landfill conditions results in the generation of biogenic carbon dioxide and methane, while the un-decomposed portion represents a biogenic carbon sink. Information on the decomposition of these municipal waste components is used to estimate national methane emissions inventories, for attribution of carbon storage credits, and to assess the life-cycle greenhouse gas impacts of wood and paper products. Hardwood (HW), softwood (SW), plywood (PW), oriented strand board (OSB), particleboard (PB), medium-density fiberboard (MDF), newsprint (NP), corrugated container (CC) and copy paper (CP) were buried in landfills operated with leachate recirculation, and were excavated after approximately 1.5 and 2.5 yr. Samples were analyzed for cellulose (C), hemicellulose (H), lignin (L), volatile solids (VS), and organic carbon (OC). A holocellulose decomposition index (HOD) and carbon storage factor (CSF) were calculated to evaluate the extent of solids decomposition and carbon storage. Samples of OSB made from HW exhibited cellulose plus hemicellulose (C + H) loss of up to 38%, while loss for the other wood types was 0–10% in most samples. The C + H loss was up to 81%, 95% and 96% for NP, CP and CC, respectively. The CSFs for wood and paper samples ranged from 0.34 to 0.47 and 0.02 to 0.27 g OC g^?1 dry material, respectively. These results, in general, correlated well with an earlier laboratory-scale study, though NP and CC decomposition measured in this study were higher than previously reported.     

Administration of Local Air Pollution Control Programs (Salaries and Qualifications of Personnel)

An attempt to develop medical air quality guides are recently made in Sweden. Even if air pollution is present in only fairly small amounts, problems frequently arise especially concerning nuisance reactions. Present regulations do not provide a basis for a standardized treatment of air pollution problems. The national air pollution situation was discussed and a survey of the literature was performed to collect data concerning current air pollutants. For sulfur dioxide a 30 day value of eight pphm and a two hour value of 25 pphm was recommended. It was further recommended to keep the carbon monoxide concentration as low as possible with an eight hour value of 30 ppm as an absolute maximum. For carcinogenic and mutagenic substances it was also recommended to keep the values as low as possible. Although available data did not support complete medical guides in all cases it was decided rather to have the above approximations than to leave the air pollution situation uncontrolled.     

The Adhesion of Solid Particles to Solid Surfaces,I. a Review

Prior exposure to ozone has been reported to increase the mortality in mice from aerosolized streptococci. The experiments described herein were undertaken to determine the effect of meteorological variables on this ozone-streptococcus model. The work was performed in replicate experiments employing four treatments. The treatments consisted of exposure to (1) ambient temperature and air, (2) ambient temperature and ozone, (3) cold and ambient air, and (4) cold and ozone, and streptococcus. The streptococcus was administered to each treatment as an aerosolized culture for 30 minutes and yielded approximately 30,000 organisms per mouse. The cold exposure was three hours at 6 to 9°C, and the ozone exposure was 0.7 to 0.9 ppm for three hours. Results indicate a significant increase in mortality attributable to the influence of cold.     

Liquid balance monitoring inside conventional,Retrofit, and bio-reactor landfill cells

The Outer Loop landfill bioreactor (OLLB) in Louisville, KY, USA has been the site of a study to evaluate long-term bioreactor performance at a full-scale operational landfill. Three types of landfill units were studied including a conventional landfill (Control cell), a new landfill area that had an air addition and recirculation piping network installed as waste was being placed (As-Built cell), and a conventional landfill that was modified to allow for liquids recirculation (Retrofit cell). During the monitoring period, the Retrofit, Control, and As-Built cells received 48, 14, and 213 L Mg^?1 (liters of liquids per metric ton of waste), respectively. The leachate collection system yielded 60, 57 and 198 L Mg^?1 from the Retrofit, Control, and As-Built cells, respectively. The head on liner in all cells was below regulatory limits. In the Control and As-Built cells, leachate head on liner decreased once waste placement stopped. The measured moisture content of the waste samples was consistent with that calculated from the estimate of accumulated liquid by the liquid balance. Additionally, measurements on excavated solid waste samples revealed large spatial variability in waste moisture content. The degree of saturation in the Control cells decreased from 85% to 75%. The degree of saturation increased from 82% to 83% due to liquids addition in the Retrofit cells and decreased back to 80% once liquid addition stopped. In the As-Built cells, the degree of saturation increased from 87% to 97% during filling activities and then started to decrease soon after filling activities stopped to reach 92% at the end of the monitoring period. The measured leachate generation rates were used to estimate an in-place saturated hydraulic conductivity of the MSW in the range of 10^?8 to 10^?7 m s^?1 which is lower than previous reports. In the Control and Retrofit cells, the net loss in liquids, 43 and 12 L Mg^?1, respectively, was similar to the measured settlement of 15% and 5–8% strain, respectively (Abichou et al., 2013). The increase in net liquid volume in the As-Built cells indicates that the 37% (average) measured settlement strain in these cells cannot be due to consolidation as the waste mass did not lose any moisture but rather suggests that settlement was attributable to lubrication of waste particle contacts, softening of flexible porous materials, and additional biological degradation.     

Health Significance of Pulmonary Function Responses to Airborne Irritants

Exposures to airborne irritants such as O₃, NO₂, SO₂ and H₂SO₄ can produce measurable changes in a variety of pulmonary functions such as respiratory mechanics, pulmonary gas exchange, mucociliary particle clearance, and airway permeability. The most commonly measured indices of pulmonary function are those obtained by analyzing flows and volumes during a maximal forced expiratory maneuver, because they can be obtained readily in both laboratory and field studies in humans. Other functional measures are essentially limited to laboratory studies on relatively small populations of humans, or on experimental animals. Interpretation of respiratory function changes in relation to exposures to airborne irritants is complicated by the large interindividual variability in baseline function and responsiveness, the superposition of both the transient effects of recent acute exposure and the cumulative effects of chronic exposure at any given measurement, and the inherent day-to-day variability of effort dependent indices. Furthermore, community exposures occur as mixtures. Each of several components may affect the same functions, but with different time scales, and may affect different segments of the population to different degrees. The greatest uncertainties lie in the significance of transient and apparently reversible effects, and their contribution, if any, to permanent functional changes. Use of animal models to study the role of transient changes in function on the development of permanent changes is illustrated in terms of the effects of H₂SO₄ on particle clearance function.     

A 10-year survey, 1980–1990, of prenatally diagnosed small supernumerary marker chromosomes,identified by fish analysis. Outcome and follow-up of 14 cases diagnosed in a series of 12 699 prenatal samples

A cytogenetic survey and follow-up studies were made of 14 cases with supernumerary marker chromosomes, identified among 12 699 prenatal samples, investigated at our institution over a 10-year period from 1980 to 1990. FISH (fluorescence in situ hybridization) techniques were employed to identify the chromosomal origin of the marker chromosomes. Five cases were familial, all derived from acrocentric chromosomes, and all without apparent phenotypic effects in the children. Nine cases represented de novo aberrations. In two cases (one with a marker from chromosome 14 or 22, the other with a ring-like marker derived from chromosome 17), the pregnancies continued and apparently normal babies were delivered at term, but the child with a marker derived from chromosome 17 showed slight psychomotor retardation at 2 years of age. All other pregnancies with de novo markers were terminated. In three cases, significant abnormalities were found at autopsy. One of these had an isochromosome 12p and the phenotype was consistent with Pallister-Killian syndrome. In conclusion, marker chromosome identification, as well as clinical follow-up, is essential for the purpose of improving genetic counselling.     

The ultrasonic detection of an isolated craniosynostosis

The prenatal detection of scaphocephaly, an isolated form of craniosynostosis, is presented. The diagnosis was made at 34 weeks of gestation in a woman with polyhydramnios. The ultrasound appearance and postnatal follow-up are presented.