Fed-batch and batch operating mode analysis of a stirred anaerobic sequencing reactor with self-immobilized biomass treating low-strength wastewater

This work presents an analysis of a stirred anaerobic sequencing discontinuous reactor with different substrate feeding strategies resulting in batch, fed-batch/batch and fed-batch operating modes. The reactor, containing granulated biomass, was fed with approximately 2.0L of synthetic domestic wastewater with Chemical Oxygen Demand of nearly 500 mg/L per cycle and operated at 30 degrees C and 50 rpm. Three feeding strategies with a total cycle time of 6 h, including 30-min settling, were adopted: batch mode with a fill cycle of 6 min, a fed-batch/batch mode with fill cycles of 60, 120 and 240 min and fed-batch mode with a fill cycle of 320 min. The system attained average non-filtered and filtered substrate removal efficiency of 78 and 84%, respectively, for all operating conditions, presenting good stability, solid retention and no granule break-up. A first order kinetic model with a residual organic matter concentration was proposed to analyze the influence of the feeding strategy on the performance during a cycle and bicarbonate alkalinity and total volatile acids concentration profiles were also quantified in order to verify the transient stability behavior.     

Review of ozone and temperature lidar validations performed within the framework of the Network for the Detection of Stratospheric Change

The use of assimilation tools for satellite validation requires true estimates of the accuracy of the reference data. Since its inception, the Network for Detection of Stratospheric Change (NDSC) has provided systematic lidar measurements of ozone and temperature at several places around the world that are well adapted for satellite validations. Regular exercises have been organised to ensure the data quality at each individual site. These exercises can be separated into three categories: large scale intercomparisons using multiple instruments, including a mobile lidar; using satellite observations as a geographic transfer standards to compare measurements at different sites; and comparative investigations of the analysis software. NDSC is a research network, so each system has its own history, design, and analysis, and has participated differently in validation campaigns. There are still some technological differences that may explain different accuracies. However, the comparison campaigns performed over the last decade have always proved to be very helpful in improving the measurements. To date, more efforts have been devoted to characterising ozone measurements than to temperature observations. The synthesis of the published works shows that the network can potentially be considered as homogeneous within +/-2% between 20-35 km for ozone and +/-1 K between 35-60 km for temperature. Outside this altitude range, larger biases are reported and more efforts are required. In the lower stratosphere, Raman channels seem to improve comparisons but such capabilities were not systematically compared. At the top of the profiles, more investigations on analysis methodologies are still probably needed. SAGE II and GOMOS appear to be excellent tools for future ozone lidar validations but need to be better coordinated and take more advantage of assimilation tools. Also, temperature validations face major difficulties caused by atmospheric tides and therefore require intercomparisons with the mobile systems, at all sites.     

Fluxes and pools of methane in wetland rice soils with varying organic inputs

Measurements of methane emission rates and concentrations in the soil were made during four growing seasons at the International Rice Research Institute in the Philippines, on plots receiving different levels of organic input. Fluxes were measured using the automated closed chambers system (total emission) and small chambers installed between plants (water surface flux). Concentrations of methane in the soil were measured by collecting soil cores including the gas phase (soil-entrapped methane) and by sampling soil solution in situ (dissolved methane). There was much variability between seasons, but total fluxes from plots receiving high organic inputs (16–24 g CH₄ m^–2) always exceeded those from the low input plots (3–9 g CH₄ m^–2). The fraction of the total emission emerging from the surface water (presumably dominated by ebullition) was greater during the first part of the season, and greater from the high organic input plots (35–62%) than from the low input plots (15–23%). Concentrations of dissolved and entrapped methane in the low organic input plots increased gradually throughout the season; in the high input plots there was an early-season peak which was also seen in emissions. On both treatments, periods of high methane concentrations in the soil coincided with high rates of water surface flux whereas low concentrations of methane were generally associated with low flux rates.     

Biopotentiality as an index of environmental compensation for composting plants

The Biopotentiality Index is a landscape ecology indicator, which can be used to estimate the latent energy of a given land and to assess the environmental impacts due to the loss of naturalness on a landscape scale. This indicator has been applied to estimate the effectiveness of the measures put in place to provide an environmental compensation for the revamping of a composting plant. These compensation measures are represented by a green belt with a minimum width of 25 m all around the plant, representing both a windbreak and a buffer zone, and by two wide wooded zones acting as core natural areas.This case-study shows that the compensation index could be used as a key tool in order to negotiate the acceptance of waste treatment plant with the population.     

Chlorpyrifos residues levels in fruits and vegetables after field treatment

Chlorpyrifos (O,O-diethyl O-3,5,6-trichloro-2-pyridyl phosphorothioate) was applied with three different formulations on oranges, peaches, tomatoes, wine and table grapes, and its behaviour was evaluated after field treatment. The formulations applied were emulsifiable concentrates (EC), microencapsulates (ME), and wettable granules (WG). The residues were similar in all crops studied in the EC and WG experiments, except peaches with WG treatment, the residue amount was lower than EC values. Tomatoes which were grown in greenhouse showed similar residues in all treatments just after treatment. Wine and table grapes showed different decline curves in the EC experiments ascribable to the different growing technology. Instrumental limit of determination (LOD) and limit of quantification (LOQ) for all matrices were 0.01, and 0.03 mg kg?1, respectively. Repeated treatments showed that Chlorpyrifos can accumulate leading to residue levels at the preharvest interval (PHI) over the maximum residue level (MRL), especially on oranges and peaches. Among the formulates used ME showed the higher risk of residues over the MRL at harvest.     

Long-term phenol, cresols and BTEX monitoring in urban air

This paper reports the results of a long-term monitoring of benzene, toluene, ethylbenzene, xylenes (BTEX), phenol and cresols in the air of Padua during a wide period of the year 2007 using two radial passive samplers (Radiello system) equipped with BTEX- and phenol-specific cartridges. Two sites were monitored, one in the industrial area and one close to the town centre. Relevant pollution episodes have been observed during both the winter and summer periods. Benzene, together with toluene, ethylbenzene and xylenes showed their maximum concentrations during the winter season, but the secondary pollutant phenol was higher than benzene for a large period of the year when the meteorological conditions blocked the pollutants in the lower layers of the atmosphere and solar radiation increased the benzene photo-oxidation process.     

Validation of an analytical method for the quantification of pyrethrins on lemons and apricots using high-performance liquid chromatography/mass spectrometry

An analytical procedure has been developed for the determination of natural pyrethrins (pyrethrin I, pyrethrin II, jasmolin I, jasmolin II, cinerin I and cinerin II) in lemon and apricot. The QuEChERS method, which stands for quick, easy, cheap, effective, rugged and safe was used for extraction. Analysis of the extract was performed by liquid-chromatography-electrospray ionisation-tandem mass spectrometry. The ions prominent in the ESI spectra were [M+H]+ for the six compounds. A Zorbax SB-C18 column was used with a programmed gradient mobile phase consisting of (A) water containing 0.1% formic acid and 5 mM ammonium formate and (B) ACN. The method was linear within the investigated concentration range, displaying a calibration curve correlation factor of 0.99. The coefficients of variation obtained (RSD) were below 20% and the recoveries were in the 70-110% range.     

Investigations on mechanical biological treatment of waste in South America: towards more sustainable MSW management strategies

This work presents an analysis on the suitability of mechanical biological treatment of municipal solid waste in South America, based on two previous experimental investigations carried out in two different countries. The first experiment was performed for determining the mass and volume reduction of MSW in the province of Concepción (Chile). The implemented bench-scale process consisted of a manual classification and separation stage, followed by an in-vessel biological degradation process. The second experiment consisted of a full-scale experiment performed in the city of Estrela (Brazil), where the existing municipal waste management facility was adapted to enhance the materials sorting and separation. Expressed in wet weight composition, 85.5% of the material input in the first experiment was separated for biological degradation. After 27 days of processing, 60% of the initial mass was reduced through degradation and water evaporation. The final fraction destined for landfilling equals 59% of the total input mass, corresponding to about 50% of the initial volume. In the second experiment, the fraction destined to landfill reaches 46.6% of the total input waste mass, whilst also significantly reducing the total volume to be disposed. These results, and the possible recovery of material streams suitable for recycling or for preparing solid recovered fuels, are the main advantages of the studied process.