Performance of a biogas upgrading process based on alkali absorption with regeneration using air pollution control residues

This work analyzes the performance of an innovative biogas upgrading method, Alkali absorption with Regeneration (AwR) that employs industrial residues and allows to permanently store the separated CO₂. This process consists in a first stage in which CO₂ is removed from the biogas by means of chemical absorption with KOH or NaOH solutions followed by a second stage in which the spent absorption solution is contacted with waste incineration Air Pollution Control (APC) residues. The latter reaction leads to the regeneration of the alkali reagent in the solution and to the precipitation of calcium carbonate and hence allows to reuse the regenerated solution in the absorption process and to permanently store the separated CO₂ in solid form. In addition, the final solid product is characterized by an improved environmental behavior compared to the untreated residues. In this paper the results obtained by AwR tests carried out in purposely designed demonstrative units installed in a landfill site are presented and discussed with the aim of verifying the feasibility of this process at pilot-scale and of identifying the conditions that allow to achieve all of the goals targeted by the proposed treatment. Specifically, the CO₂ removal efficiency achieved in the absorption stage, the yield of alkali regeneration and CO₂ uptake resulting for the regeneration stage, as well as the leaching behavior of the solid product are analyzed as a function of the type and concentration of the alkali reagent employed for the absorption reaction.     

Environmental fate of Ra in cation-exchange regeneration brine waste disposed to septic tanks, New Jersey Coastal Plain, USA: migration to the water table

Fate of radium (Ra) in liquid regeneration brine wastes from water softeners disposed to septic tanks in the New Jersey Coastal Plain was studied. Before treatment, combined Ra (²²⁶Ra plus ²²⁸Ra) concentrations (maximum, 1.54 Bq L⁻¹) exceeded the 0.185 Bq L⁻¹ Maximum Contaminant Level in 4 of 10 studied domestic-well waters (median pH, 4.90). At the water table downgradient from leachfields, combined Ra concentrations were low (commonly ≤0.019 Bq L⁻¹) when pH was >5.3, indicating sequestration; when pH was ≤5.3 (acidic), concentrations were elevated (maximum, 0.985 Bq L⁻¹ - greater than concentrations in corresponding discharged septic-tank effluents (maximum, 0.243 Bq L⁻¹)), indicating Ra mobilization from leachfield sediments. Confidence in quantification of Ra mass balance was reduced by study design limitations, including synoptic sampling of effluents and ground waters, and large uncertainties associated with analytical methods. The trend of Ra mobilization in acidic environments does match observations from regional water-quality assessments.     

On-road ultrafine particle concentration in the M5 East road tunnel,Sydney, Australia

The human health effects following exposure to ultrafine (<100 nm) particles (UFPs) produced by fuel combustion, while not completely understood, are generally regarded as detrimental. Road tunnels have emerged as locations where maximum exposure to these particles may occur for the vehicle occupants using them. This study aimed to quantify and investigate the determinants of UFP concentrations in the 4 km twin-bore (eastbound and westbound) M5 East tunnel in Sydney, Australia. Sampling was undertaken using a condensation particle counter (CPC) mounted in a vehicle traversing both tunnel bores at various times of day from May through July, 2006. Supplementary measurements were conducted in February, 2008. Over three hundred transects of the tunnel were performed, and these were distributed evenly between the bores. Additional comparative measurements were conducted on a mixed route comprising major roads and shorter tunnels, all within Sydney. Individual trip average UFP concentrations in the M5 East tunnel bores ranged from 5.53 × 10⁴ p cm^?3 to 5.95 × 10⁶ p cm^?3. Data were sorted by hour of capture, and hourly median trip average (HMA) UFP concentrations ranged from 7.81 × 10⁴ p cm^?3 to 1.73 × 10⁶ p cm^?3. Hourly median UFP concentrations measured on the mixed route were between 3.71 × 10⁴ p cm^?3 and 1.55 × 10⁵ p cm^?3. Hourly heavy diesel vehicle (HDV) traffic volume was a very good determinant of UFP concentration in the eastbound tunnel bore (R² = 0.87), but much less so in the westbound bore (R² = 0.26). In both bores, the volume of passenger vehicles (i.e. unleaded gasoline-powered vehicles) was a significantly poorer determinant of particle concentration. When compared with similar studies reported previously, the measurements described here were among the highest recorded concentrations, which further highlights the contribution road tunnels may make to the overall UFP exposure of vehicle occupants.     

Organochlorine concentrations, reproductive physiology, and immune function in unique populations of freshwater Atlantic stingrays (Dasyatis sabina) from Florida's St. Johns River

Within the past decade, reproductive and health disorders have been reported to occur in unique populations of Atlantic stingrays (Dasyatis sabina) inhabiting certain components of Florida's St. Johns River. Since these irregularities are consistent with the alleged effects of organochlorine (OC) contaminant exposure in other Florida wildlife, the goal of this study was to examine possible associations between OC concentrations and reproduction and/or immune function in stingrays from this river system. Liver concentrations of 30 OC pesticides/pesticide metabolites and total polychlorinated biphenyls (PCBs) were measured and compared in D. sabina collected from four central Florida lakes of the St. Johns River: Lake George, Lake Harney, Lake Jesup, and Lake Monroe. Reproductive biology, serum testosterone and 17beta-estradiol concentrations, and circulating white blood cell counts were examined and compared in stingrays from lakes that were determined to contain low (Lake George), intermediate (Lake Monroe), and high (Lake Jesup) levels of pesticide contamination, based on the results of liver OC assessments. Successful breeding occurred in Lake Jesup stingrays, indicating that the degree of OC accumulation in these animals is not high enough to cause reproductive impairment. However, elevated serum steroid concentrations and white blood cell counts were observed in Lake Jesup stingrays, suggesting that endocrine and immune function may be altered in these animals due to OC exposure and/or other, as yet unknown, ecological factors. Inconsistencies in the reproductive success of Lake Monroe stingrays were observed, confirming earlier reports of reproductive complications in this sub-population. Based on these findings, previous occurrences of reproductive failure in St. Johns River stingrays may be due to environmental factors other than OC exposure.     

Driving and alternatives: older drivers in Michigan

Method: A statewide telephone survey of Michigan drivers and former drivers aged 65 and older collected information on transportation mode choices, experience with alternatives to driving, and whether drivers planned for when they could no longer drive. Results: Results showed that most older adult households owned at least one automobile, and that the automobile was the primary mode of transportation. Most former drivers obtained rides from relatives and friends. Use of public transportation was low, and some seniors were not aware of available public transportation services. Older drivers did not plan for driving cessation. Over half the drivers who perceived a likelihood of driving problems within 5 years expected to keep driving beyond 5 years. Impact on industry: Because of their lifelong reliance on the automobile, their desire to drive themselves, and their lack of experience with public transportation, efforts to enhance the mobility of older people should consider this background while alternatives to the personal automobile are developed.     

Small-scale variability of metals in soil and composite sampling

Soil pollution data is also strongly scattering at small scale. Sampling of composite samples, therefore, is recommended for pollution assessment. Different statistical methods are available to provide information about the accuracy of the sampling process. Autocorrelation and variogram analysis can be applied to investigate spatial relationships. Analysis of variance is a useful method for homogeneity testing. The main source of the total measurement uncertainty is the uncertainty arising from sampling. The sample mass required for analysis can also be estimated using an analysis of variance. The number of increments to be taken for a composite sample can be estimated by means of simple statistical formulae. Analytical results of composite samples obtained from different fusion procedures of increments can be compared by means of multiple mean comparison. The applicability of statistical methods and their advantages are demonstrated for a case study investigating metals in soil at a very small spatial scale. The paper describes important statistical tools for the quantitative assessment of the sampling process. Detailed results clearly depend on the purpose of sampling, the spatial scale of the object under investigation and the specific case study, and have to be determined for each particular case.     

Prioritizing Stream Barrier Removal to Maximize Connected Aquatic Habitat and Minimize Water Scarcity

Instream barriers, such as dams, culverts, and diversions, alter hydrologic processes and aquatic habitat. Removing uneconomical and aging instream barriers is increasingly used for river restoration. Historically, selection of barrier removal projects used score‐and‐rank techniques, ignoring cumulative change and the spatial structure of stream networks. Likewise, most water supply models prioritize either human water uses or aquatic habitat, failing to incorporate both human and environmental water use benefits. Here, a dual‐objective optimization model identifies barriers to remove that maximize connected aquatic habitat and minimize water scarcity. Aquatic habitat is measured using monthly average streamflow, temperature, channel gradient, and geomorphic condition as indicators of aquatic habitat suitability. Water scarcity costs are minimized using economic penalty functions while a budget constraint specifies the money available to remove barriers. We demonstrate the approach using a case study in Utah's Weber Basin to prioritize removal of instream barriers for Bonneville cutthroat trout, while maintaining human water uses. Removing 54 instream barriers reconnects about 160 km of quality‐weighted habitat and costs approximately US$10 M. After this point, the cost‐effectiveness of removing barriers to connect river habitat decreases. The modeling approach expands barrier removal optimization methods by explicitly including both economic and environmental water uses.     

Does temperature modify short-term effects of ozone on total mortality in 60 large eastern US communities? An assessment using the NMMAPS data

Many studies have indicated that ozone is associated with morbidity and mortality. A few studies have reported that the association is heterogeneous across seasons and geographic regions. However, little information is available on whether both temperature and geographic factors simultaneously modify the ozone effect. This study used a Poisson regression model to explore whether temperature modifies the effect of ozone on mortality in the 60 large eastern US communities during April to October, 1987-2000. Results show that temperature modified ozone-mortality associations and that such modification varied across geographic regions. In the northeast region, a 10-ppb increment in ozone was associated with an increase of 2.22% (95% posterior interval [PI]: 1.19%, 3.13%), 3.06% (95% PI: 2.21%, 3.76%) and 6.22% (95% PI: 4.77%, 7.56%) in mortality at low, moderate and high temperature level, respectively, while in the southeast region a 10-ppb increment in ozone was associated with an increase of 1.13% (95% PI:-1.12%, 3.18%), 1.50% (95% PI: 0.22%, 2.81%) and 1.29% (95% PI:-0.33%, 2.96%) in mortality, respectively. We concluded that temperature synergistically modified the ozone-mortality association in the northeast region, but such a pattern was not apparent in the southeast region. Thus, both temperature and geographic factors should be considered in the assessment of ozone effects.     

Comparison of various sampling methods for PCDDs and PCDFs in stack gas

There have been discussions about how complete PCDDs and PCDFs are sampled from stack gas of waste combustion plants by various sampling methods. In Germany, at present, a sampling method is used, which was first proposed by Nottrodt et al.¹, consisting of a filter device, condenser, and an absorption train. Since this sampling procedure complicates sampling and analysis, we compared this “standard procedure” with a “dilution method”, where only a filter, impregnated with paraffin, is used as trapping device, and also tested the effectiveness of XAD-2 as an adsorption trap.

As standard procedure the standard train was always used in parallel to other sampling methods. The results of four parallel sampling periods confirmed, that comparable results are obtained, when parallel sampling is carried out with the standard train.

The result of our investigation can be summarized as follows: The total emission of PCDDs and PCDFs determined by different sampling procedures varies only insignificantly. This means that sampling and analysis for PCDDs and PCDFs in stack gas could be simplified considerably.