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PubMed2006

Effect of grinding and heating on Ni2+ uptake properties of waste paper sludge.

Uptake properties of Ni2+ were examined for unmilled and milled paper sludge calcined at various temperatures to develop a new usage of waste paper sludge. Since paper sludge mainly consists of cellulose ([C6H(10)O5]n) fibers, calcite (CaCO3), kaolinite (Al2Si2O5(OH)4) and talc (Mg3Si(4)O(10)(OH)2), amorphous and crystalline CaO(MgO)-Al(2)O(3)-SiO(2) compounds are formed by calcining paper sludge. Wet and dry milling treatments were performed to accelerate solid-state reaction to form the above mentioned target compounds. The crystalline phases originally present decompose at increasing calcining temperature (up to 800 degrees C) in the order cellulose <kaolinite <calcite <talc. An amorphous phase was formed in the samples below 800 degrees C and the temperatures changed depending on the milling conditions in the order dry milled <wet milled <unmilled. Gehlenite (Ca(2)Al(2)SiO(7)) and anorthite (CaAl(2)Si(2)O(8)) crystallized by calcining at 900 degrees C in all the samples, formed by solid-state reaction of kaolinite with calcite. The (29)Si and (27)Al MAS NMR spectra of the amorphous samples were similar to those of crystalline phases, suggesting that the local structure of the amorphous phase resembles the crystalline structures. Maximum Ni2+ uptake occurred in the dry-milled samples calcined at 600 degrees C, and wet-milled and unmilled samples calcined at 700 degrees C, respectively. The dry-milled and calcined at 600 degrees C sample showed the highest Ni2+ uptake (4.54 mmol/g) and an uptake rate of 3.5 micromol/(gmin).

Adsorption↗

PubMed2006

Choosing policy instruments for controlling ozone depleting substances in a developing context: the case of Chile.

Chile ratified the Montreal Protocol in 1990 which sets out an agenda for the reduction and then elimination of ozone depleting substances (ODS); however, by 1998 the country had not yet defined a strategy to encourage greater compliance, so that in the same year the National Environmental Commission decided to examine the policy options available. This paper examines the process followed to develop this strategy. As a first step it was necessary to look at how far the implicit policy of "business as usual" could be stretched without jeopardizing Chile's compliance obligations. A second step included quantifying compliance costs and their impact on different policy instruments and so policy choice. Finally, the attitudes of decision-makers or participants were identified, by interviews with officials of the different public agents involved, in order to weigh their views about policy. A strategy was proposed, based on this information, which the Chilean regulator has used, although not in its entirety. The methodology developed could well be useful for developing-country Protocol signatories building their own appropriate compliance strategy.

Atmosphere↗

PubMed2006

Application of Eichhornia crassipes and Pistia stratiotes for treatment of urban sewage in Israel.

The effectiveness of sewage purification by aquatic plants, such as water hyacinth (Eichhornia crassipes) and water lettuce (Pistia stratiotes), was tested on laboratory and pilot scales. Cascade and semi-continuous pilot experiments verified that the plants are capable of decreasing all tested indicators of water quality to levels that permit the use of the purified water for irrigation of tree crops. This applies to biochemical oxygen demand (BOD), chemical oxygen demand (COD), total suspended solids (TSS), and turbidity. The laboratory-scale tests confirm the capacity of the plants to reach and hold reasonably low levels of BOD (5-7 mg L(-1)) and COD (40-50 mg L(-1)) and very low levels of TSS (3-5 mg L(-1)) and turbidity (1-2 NTU). In the experimental pilot setup, with circulation, COD decreased from 460 to 100 mg L(-1) after 2.5-4 days of treatment, while 6-7 days were required to this end without circulation. This doubled the active pond area and provided a two-level hydraulic loading (8 and 12 L min(-1)) with circulation that proved to be effective during the summer as well as the winter season. The outflow concentrations were 50-85 mg L(-1) of COD and 4-6 mg L(-1) of BOD. The results show that the use of this free water surface flow system (FWS) and its low maintenance system for treatment of urban and agricultural sewage is a viable option.

Araceae↗

PubMed2006

On the relationship between set-out rates and participation ratios as a tool for enhancement of kerbside household waste recycling.

Although the use of kerbside recycling facilities by householders is often key to the reduction of materials disposed of to landfill, the quantitative assessment of householders' recycling behaviour is problematic. This study introduces a method to diagnose recycling behaviour by assessing kerbside scheme use in terms of the set-out of recyclate containers compared to the proportion of households participating in recycling (participation ratio). Application of numerical behaviour models demonstrated that kerbside recycling in sampled regions of the UK tends to be consistent with householders using kerbside schemes more frequently than would be observed with random patterns of use that are uniform amongst all householders. When aggregated to collection rounds, householders' modal recycling behaviour tended towards either non-participation or frequent participation. We propose that initiatives to enhance kerbside recycling should employ such quantitative assessments of recycling behavioural modes to inform and guide promotional and educational strategies. A conceptual model for prioritizing campaigns to promote recycling at the kerbside on the basis of identifiable and quantifiable patterns of householder recycling behaviour is presented.

Community Participation↗

PubMed2006

Para-chlorophenol containing synthetic wastewater treatment in an activated sludge unit: effects of hydraulic residence time.

Due to the toxic nature of chlorophenol compounds present in some chemical industry effluents, biological treatment of such wastewaters is usually realized with low treatment efficiencies. Para-chlorophenol (4-chlorophenol, 4-CP) containing synthetic wastewater was treated in an activated sludge unit at different hydraulic residence times (HRT) varying between 5 and 30 h while the feed COD (2500 mg l(-1)), 4-CP (500 mg l(-1)) and sludge age (SRT, 10 days) were constant. Effects of HRT variations on COD, 4-CP, toxicity removals and on settling characteristics of the sludge were investigated. Percent COD removals increased and the effluent COD concentrations decreased when HRT increased from 5 to 15 h and remained almost constant for larger HRT levels. Nearly, 91% COD and 99% 4-CP removals were obtained at HRT levels above 15 h. Because of the highly concentrated microbial population at HRT levels of above 15 h, low effluent (reactor) 4-CP concentrations and almost complete toxicity removals were obtained. High biomass concentrations obtained at HRT levels above 15 h were due to low 4-CP contents in the aeration tank yielding negligible inhibition effects and low maintenance requirements. The sludge volume index (SVI) decreased with increasing HRT up to 15 h due to high biomass concentrations at high HRT levels resulting in well settling sludge with low SVI values. Hydraulic residence times above 15 h resulted in more than 90% COD and complete 4-CP and toxicity removals along with well settling sludge.

Bacteria↗

PubMed2006

Solid olive waste in environmental cleanup: oil recovery and carbon production for water purification.

A potentially-economic three-fold strategy, to use solid olive wastes in water purification, is presented. Firstly, oil remaining in solid waste (higher than 5% of waste) was recovered by the Soxhlet extraction technique, which can be useful for the soap industry. Secondly, the remaining solid was processed to yield relatively high-surface area active carbon (AC). Thirdly, the resulting carbon was employed to reversibly adsorb chromate ions from water, aiming to establish a water purification process with reusable AC. The technique used here enabled oil recovery together with the production of a clean solid, suitable for making AC. This process also has the advantage of low production cost.

Adsorption↗

PubMed2006

Study on the influence of additives in an industrial calcium fluoride and waterworks sludge co-melting system.

This work explores the effect of additives on the pouring temperature in a waterworks and industrial calcium fluoride sludge co-melting system. Two kinds of sludge were mixed in various ratios to find a mixing ratio at which the operating temperature for subsequent additive tests was relatively low. Various proportions of either sodium carbonate (Na2CO3) or potassium carbonate (K2CO3) reagent were added to the mixed-sludge samples to elucidate the consequent changes in pouring temperature. The experimental results revealed that the pouring temperature was lowest when calcium fluoride was mixed with waterworks sludge in a ratio of 4:6 (w/w). Adding sodium carbonate or potassium carbonate reagent to the mixed-sludge samples further reduced the pouring temperature. Increasing the amount of sodium carbonate did not significantly reduce the pouring temperature beyond that observed when 2% was added, suggesting that 2% was the optimal additional percentage of sodium carbonate. In contrast, the pouring temperature was increased when over 2% potassium carbonate was added to the mixed-sludge samples, revealing that the optimal additional percentage of potassium carbonate was also 2%. These findings indicate that both sodium carbonate and potassium carbonate can be used as additives to increase the energy efficiency of the melting process, but sodium carbonate is more operationally convenient.

Calcium Fluoride↗

PubMed2006

Agricultural recycling of treatment-plant sludge: a case study for a vegetable-processing factory.

The present study evaluated the possibility of using the sludge produced by a vegetable-processing factory in agriculture. The sludge was amended with a soil mixture (i.e., a mixture of sand, soil, and manure) and was applied at 0, 165, 330, 495 and 660 t/ha to promote the growth of cucumbers. The effects of various sludge loadings on plant growth were assessed by counting plants and leaves, measuring stem lengths, and weighing the green parts and roots of the plants. We also compared heavy metal uptake by the plants for sludge loadings of 330, 495, and 660 t/ha with various recommended standards for vegetables. Our results showed that plant growth patterns were influenced to some extent by the sludge loadings. In general, the number of leaves, stem length, and dry weight of green parts exhibited a pronounced positive growth response compared with an unfertilized control, and root growth showed a lesser but still significant response at sludge loadings of 165 and 330 t/ha. The sludge application caused no significant increase in heavy metal concentrations in the leaves, though zinc (Zn) and iron (Fe) were found at elevated concentrations. However, despite the Zn and Fe accumulation, we observed no toxicity symptoms in the plants. This may be a result of cucumber's tolerance of high metal levels.

Cucumis sativus↗

PubMed2006

The thief process for mercury removal from flue gas.

The Thief Process is a cost-effective variation to activated carbon injection (ACI) for removal of mercury from flue gas. In this scheme, partially combusted coal from the furnace of a pulverized coal power generation plant is extracted by a lance and then re-injected into the ductwork downstream of the air preheater. Recent results on a 500-lb/h pilot-scale combustion facility show similar removals of mercury for both the Thief Process and ACI. The tests conducted to date at laboratory, bench, and pilot-scales demonstrate that the Thief sorbents exhibit capacities for mercury from flue gas streams that are comparable to those exhibited by commercially available activated carbons. A patent for the process was issued in February 2003. The Thief sorbents are cheaper than commercially-available activated carbons; exhibit excellent capacities for mercury; and the overall process holds great potential for reducing the cost of mercury removal from flue gas. The Thief Process was licensed to Mobotec USA, Inc. in May of 2005.

Adsorption↗

PubMed2006

A study on recovery of oil from sludge containing oil using froth flotation.

Induced air flotation was used to recover oil from synthetically prepared sludge containing oil. A commercial surfactant was used as the collector and frother. The effects of various parameters, namely flotation time, initial amount of oil in the feed and the amount of surfactant used on the recovery of oil were investigated. Within the range of operating conditions studied herein, the maximum oil recovery obtained was about 55%. A detailed study of flotation kinetics based on oil recovery was carried out. It showed that the process followed first-order kinetics.

Benzenesulfonates↗

PubMed2006

Properties of steel foundry electric arc furnace dust solidified/stabilized with Portland cement.

Electric arc furnace dust from steel production is generated in considerable amounts worldwide and needs to be treated as hazardous waste. The aim of this study was to investigate the properties of electric arc furnace dust solidified/stabilized by using Portland cement. Mortar and paste samples were prepared with varying waste-to-binder ratios between 0% and 90%. A comprehensive experimental program was designed including XRF characterization, setting time, unconfined compressive strength, and toxicity characteristics leaching procedure (TCLP), synthetic precipitation leaching procedure (SPLP), and acid neutralization capacity (ANC) tests. The results were evaluated in order to determine if the solidified /stabilized product can be disposed of at a landfill site with domestic waste or at a segregated landfill. The effect of using sand on S/S performance was also investigated. The results indicated that the solidification /stabilization process using PC helps the heavy metals to be bound in the cement matrix, but the TCLP leaching results exceeded the EPA landfilling limits. The SPLP leaching results conformed to the limits implying that the waste or S/S products can be disposed of at a segregated landfill; however the low ANC of the S/S products reveals that there may be leaching in the long-term. The sand used in the mortar samples adversely affected the S/S performance, causing higher heavy metal leaching levels, and lower pH levels in the leachate after the TCLP extraction than those measured in the leachate of the paste samples.

Dust↗

PubMed2007

Planning for sustainable tourism in southern Pulau Banggi: an assessment of biophysical conditions and their implications for future tourism development.

A priori assessments of a site's biophysical and socio-economic capacity for accommodating tourism are less common than tourism impact studies. A priori evaluations can provide a contextual understanding of ecological, economic and socio-cultural forces, which shape the prospects for sustainable tourism development at the host destination, and can avert adverse impacts of tourism. We conduct an a priori assessment of the biophysical environment of Pulau Banggi, in the Malaysian state of Sabah for sustainable tourism development. We characterise baseline conditions of the island's marine biodiversity, seasonality, and infrastructure. We then evaluate how existing biophysical conditions will influence options for sustainable tourism development. In particular, we suggest conditions, if there are any, which constitute a limit to future tourism development in terms of compatibility for recreation and resilience to visitor impacts. We find that the biggest constraint is the lack of adequate water and sanitation infrastructure. Blast fishing, although occurring less than once per hour, can potentially destroy the major attraction for tourists. We conclude that while Pulau Banggi possesses natural qualities that are attractive for ecotourism, financial and institutional support must be made available to provide facilities and services that will enable local participation in environmental protection and enhance prospects for future sustainable tourism.

Biodiversity↗

PubMed2005

Soil migration and plant uptake of technetium from a fluctuating water table.

Soil columns (50x15 cm) were used to determine the potential for 95mTc (as a surrogate for 99Tc which is an important component of some radioactive waste) to migrate from a contaminated, fluctuating water table, through sandy loam soil and into perennial ryegrass. Upward migration was significantly retarded with, generally, only the bottom few centimetres of soil becoming contaminated over the 6 months of the experiment. This is thought to have been due to the presence of anoxic conditions within the water table leading to the reduction of pertechnetate to Tc(IV) species which are relatively insoluble. However, some evidence of very slow upward migration over time was found. Only a small and inconsistent transfer of activity into the perennial ryegrass was observed. Whilst these observations would suggest that 99Tc is less important than radionuclides such as 129I and 36Cl in terms of the risk associated with radioactive waste disposal, the potential for a slow upward migration, and/or a pulse-release following the re-oxidation of reduced soil in which 99Tc has accumulated should not be overlooked.

Lolium↗

PubMed2004

Metal behavior during vitrification of incinerator ash in a coke bed furnace.

In this study, municipal waste incinerator ash was vitrified in a coke bed furnace system and the behavior of metals was investigated. Coke and lime were added to provide heat which facilitated vitrification. Ash contributed more than 90% of metal (except for Ca) input-mass. Metal species with low boiling points accounted for the major fraction of their input-mass adsorbed by air pollution control devices (APCDs) fly ash. Among the remaining metals, those species with light specific weights in this furnace tended to be encapsulated in slag, while heavier species were mainly discharged by ingot. Meanwhile, the leachability of hazardous metals in slag was significantly reduced. The distribution index (DI) was defined and used as an index for distribution of heavy metals in the system. A high DI assures safe slag reuse and implies feasibility of recovering hazardous heavy metals such as Cr, Cu, Fe, Pb and Zn. The vitrification in a coke bed furnace proved to be a useful technology for the final disposal of MSW incinerator ash. The heavy metals are separated into the slag, ingot and fly ash, allowing safe reuse of the slag and possible recovery of the metals contained in the ingot and ash fractions.

Air↗

PubMed2004

Performance of three resin-based materials for treating uranium-contaminated groundwater within a PRB.

Three materials that are designed to treat uranium-contaminated water were investigated. These are a cation exchange resin, IRN 77; an anion exchange resin, Varion AP; and a recently developed material called PANSIL (quartz sand coated with 2% amidoxime resin by weight). The reaction rate, capacity, and effective pH range of the three materials are reported. The capacity and conditional distribution coefficient in neutral, uranyl-contaminated synthetic groundwater containing carbonate are also reported. The suitability of each material for treating uranium-contaminated groundwater using a permeable reactive barrier (PRB) approach is then discussed. All three materials react rapidly in the pH range 5-7, reaching equilibrium in less than 4h at approximately 23 degrees C. The unconditioned cation exchange resin removed 8 g UO2 2+ per kg of resin from neutral synthetic groundwater containing 30 mg/l of UO2 2+, but a lower capacity is anticipated in groundwater with either higher ionic strength or lower UO2 2 concentrations. It operates by first acidifying the solution, then sorbing UO2 2, and can release UO2 2 when its buffering capacity has been exhausted. The anion exchange resin is very effective at removing anionic uranyl carbonate species from solutions with a pH above 5, with good specificity. Up to 50 g/kg of uranium is removed from contaminated groundwater at neutral pH. PANSIL is effective at sequestering cationic and neutral uranyl species from solutions in the pH range 4.5-7.5, with very good specificity. The capacity of PANSIL is pH-dependent, increasing from about 0.4 g/kg at pH 4.5, to about 1 g/kg at pH 6, and 1.5 g/kg around pH 7.5. In neutral groundwater containing carbonate, both the anion exchange resin and PANSIL exhibit conditional distribution coefficients exceeding 1470 ml/g, which is about an order of magnitude higher than comparable reactive barrier materials reported in the literature.

Adsorption↗

PubMed2004

Decomposition of benzene in the RF plasma environment. Part I. Formation of gaseous products and carbon depositions.

This study employed radio-frequency (RF) plasma for decomposing benzene (C6H6) gas, and examined both gaseous products and solid depositions after reaction. The reactants and products were analyzed mainly by using both an on-line Fourier transform infrared (FT-IR) spectrometer and a gas chromatography. The analyses for solid deposition included electron spectroscopy for chemical analysis (ESCA), element analysis and heat value analysis. The C2H2, C2H4, C2H6, CH4, CO2 and CO were detected and discussed. The analytical results demonstrate that in the C6H6/Ar plasma, C2H2 is the sole gaseous product being detected. The fraction of total carbon input converted into C2H2 YC2H2 increased with increasing C6H6 feed concentration, but decreased with increasing input power. In the C6H6/H2/Ar system, besides C2H2, CH4, C2H4 and C2H6 were also detected, and their yields increased with increasing H2/C6H6 ratio. The above results indicated that the addition of H2 (auxiliary gas) achieves the benefit of creating hydrogen-rich species like CH4, C2H4 and C2H6. In the C6H6/O2/Ar system, C6H6 could be totally oxidized into CO2, CO and H2O, and no measurable phenol was found. Analyses of solid depositions revealed that the carbon depositions were similar to those of Anthracite. The carbon deposition has a heat value of 7000 kcal/kg. Additionally, the possible reaction pathways were also built up and discussed.

Air Pollutants↗

PubMed2005

A SEM and X-ray study for investigation of solidified/stabilized arsenic-iron hydroxide sludge.

Despite the fact that the solidification/stabilization of arsenic containing wastes with Portland cement and lime has an extensively documented history of use, the physical and chemical phenomena as a result of the interaction between arsenic and cement components have not been fully characterized. The study investigates the behavior of synthesized arsenic-iron hydroxide sludge, the by-product of arsenic removal by coagulation with ferric chloride, in solidified/stabilized matrices as well as its binding mechanisms by exploring the cementitious matrices in the micro-scale by scanning electron microscopy equipped with energy dispersive X-ray spectrometer (SEM-EDS). It was revealed that arsenic can be chemically fixed into cementitious environment of the solidified/stabilized matrices by three important immobilization mechanisms; sorption onto C-S-H surface, replacing SO4(2-) of ettringite, and reaction with cement components to form calcium-arsenic compounds, the solubility limiting phases.

Arsenic↗

PubMed2005

An ab initio study on ethylenedinitramine and its monovalent ions.

An explosive material, ethylenedinitramine (EDNA), its mono and di aci forms, as well as its monovalent cation and anion forms have been considered for 6-31G (UHF) type ab initio quantum chemical treatment in order to investigate the stability of EDNA in the neutral form and when charges develop on it exposed to electrical fields during the storage, handling or explosion process. The calculations indicate stable species. The aci forms are less stable than EDNA itself and the anion form is more stable than the neutral and cation forms. Although, the charge development is accompanied by some elongation or contraction of bonds and deviation of bond angles also as compared to the neutral state, no bond rapture occurs.

Aza Compounds↗