Wood Fly Ash Research Articles

Characterization and treatment of the phosphoric gypsum transport water

This paper presents a new treatment procedure applied on phosphogypsum transport water. Untreated transport water is highly acidic (pH 1.79), having fluoride content of 1540 mg/L and elevated values of phosphates (215 mg/L) and heavy metals (Fe = 25.8 mg/L; Zn = 5.7 mg/L; Mn = 2.7 mg/L, V = 1.7 mg/L). Neutralization/purification of the transport water was carried out with wood fly ash, otherwise a rich source of calcium, composed of calcite, dipotassium calcium carbonate and hydroxylapatite. Maximum removal efficiency of fluoride was observed at pH 7 (99.99%) and phosphate at pH 9 (96.29%). The removal of fluorides was a consequence of the formation of fluorite and fluorapatite mineral phases derived from the reaction of calcium (released from the fly ash minerals) and fluorides (from the transport water). The removal of phosphates resulted from the formation of fluorapathite and hydroxilapatite. At the optimum conditions removal efficiencies for the elements Pb, V, Cr(VI), Mn, Fe, Ni, Cu, and Zn were 95%, 98.14%, 91.11%, 100%, 99.71%, 96.33%, 97.24%, and 99.65%, respectively. Optimal heavy metal removal occurred in major cases at pH 7.

Environmental assessment of incinerator residue utilisation

Incineration ashes may be treated either as a waste to be dumped in landfill, or as a resource that is suitable for re-use. In order to choose the best management scenario, knowledge is needed on the potential environmental impact that may be expected, including not only local, but also regional and global impact. In this study, A life cycle assessment (LCA) based approach was outlined for environmental assessment of incinerator residue utilisation, in which leaching of trace elements as well as other emissions to air and water and the use of resources were regarded as constituting the potential environmental impact from the system studied. Case studies were performed for two selected ash types, bottom ash from municipal solid waste incineration (MSWI) and wood fly ash. The MSWI bottom ash was assumed to be suitable for road construction or as drainage material in landfill, whereas the wood fly ash was assumed to be suitable for road construction or as a nutrient resource to be recycled on forest land after biofuel harvesting. Different types of potential environmental impact predominated in the activities of the system and the use of natural resources and the trace element leaching were identified as being relatively important for the scenarios compared. The scenarios differed in use of resources and energy, whereas there is a potential for trace element leaching regardless of how the material is managed. Utilising MSWI bottom ash in road construction and recycling of wood ash on forest land saved more natural resources and energy than when these materials were managed according to the other scenarios investigated, including dumping in landfill.

Catalytic ozonation of ammonia using biomass char and wood fly ash

Catalytic ozonation of gaseous ammonia was investigated at room temperature using wood fly ash (WFA) and biomass char as catalysts. WFA gave the best results, removing ammonia (11 ppmv NH 3, 45% conversion) at 23 °C at a residence time of 0.34 s, using 5 g of catalyst or ash at the lowest ozone concentration (62 ppmv). Assuming pseudo zero order kinetics in ozone, a power rate law of - r NH 3 = 7.2 × 10 - 8 C NH 3 0.25 ( r, mol g −1 s −1, C NH3 mol L −1) was determined at 510 ppmv O 3 and 23 °C for WFA. Water vapor approximately doubled the oxidation rate using WFA and catalytic ozonation activity was not measured for the char without humidifying the air stream. Overall oxidation rates using the crude catalysts were lower than commercial catalysts, but the catalytic ozonation process operated at significantly lower temperatures (23 vs. 300 °C). Nitric oxide was not detected and the percentage of NO 2 formed from NH 3 oxidation ranged from 0.3% to 3% (v/v), with WFA resulting in the lowest NO 2 level (at low O 3 levels). However, we could not verify that N 2O was not formed, so further research is needed to determine if N 2 is the primary end-product. Additional research is required to develop techniques to enhance the oxidation activity and industrial application of the crude, but potentially inexpensive catalysts.

Effect of wood fly ash and compost on nitrification and denitrification in agricultural soil

Wood ash from biofuel combustion plants and compost from source-separated household waste are commonly spread on forest, agricultural and horticultural soils as a valuable source of plant nutrients. However, due to anthropogenic activities, wood ash may contain high concentrations of heavy metals. Heavy metals are toxic to microorganisms and therefore, soil microbial response to wood ash should be considered when soil is amended with ash. Compost is known to improve soil structure and may also act as a bioremediating agent, mitigating any toxic effects of wood ash on soil microorganisms. In the present study, the aim was to investigate whether wood ash has any toxic effect on soil microbial activity and, if this is the case, whether compost could mitigate these effects. The effect of wood fly ash on potential ammonium oxidation rate (PAO) and potential denitrification rate (PDA) in arable soil was investigated in one dose–response assay and in two pot experiments with or without plants, respectively. The treatments were amendment with wood fly ash, compost or a combination of wood fly ash and compost. PAO and PDA were assessed immediately or after 7 and 90 days in the different experiments. Wood fly ash decreased PDA to 16–56% compared to the control, while PAO varied between 82% and 205%. Sole compost addition stimulated both processes. This positive effect was also observed in the combined wood fly ash–compost treatment. In conclusion, wood ash had a toxic effect on PDA, both on an immediate, short-term and long-term basis. Amendment of compost clearly mitigated this toxic effect. The observed toxicity could be an effect of the metal content of ash.

Catalytic Ozonation of Propanal Using Wood Fly Ash and Metal Oxide Nanoparticle Impregnated Carbon

Catalytic ozonation of propanal at ambient temperatures (23-25 degrees C) was investigated by varying propanal and ozone concentrations and catalyst type. The catalysts tested included wood fly ash (WFA), magnetically separated ash, synthetic hematite and magnetite, and metal oxide nanoparticle impregnated activated carbon and peanut hull char. A power law model independent of ozone concentration for WFA (r(w), moles g(-1) s(-1)) and magnetite (r(m)) were, respectively, r(w) = k'(w) C(R(0.89)) and r(m) = k'(m)C(R(1.55)), where kw, and k'(m) were 2.36 x 10(-6) g(-1) s(-1) (moles)(-0.11) (m3)(0.89) and 6.5 x 10(-4) g(-1) s(-1) (moles)(-0.55) (m3)(1.55), respectively (5-15 ppmv). Magnetite and hematite present in the WFA were theorized to be the primary active sites, since magnetically separated WFA had a significantly higher reaction rate (approximately 12x, mol m(-2) s(-1)) than that of WFA. X-ray diffraction analysis demonstrated a qualitative increase in magnetite and hematite in the magnetically separated ash, and synthetic magnetite and hematite had reaction rates >80x and 200x that of WFA or activated carbon (surface area basis). Supercritical deposition of hematite on/in peanut hull char successfully generated a porous, pelleted catalystfrom an agricultural residue capable of oxidizing propanal at rates 12x activated carbon and similar to commercially available catalysts (per mass basis). Water vapor significantly increased the propanal reaction rate when using wood fly ash and activated carbon.

Toxicity assessment of heavy metal mixtures by Lemna minor L.

The discharge of untreated electroplating wastewaters directly into the environment is a certain source of heavy metals in surface waters. Even though heavy metal discharge is regulated by environmental laws many small-scale electroplating facilities do not apply adequate protective measures. Electroplating wastewaters contain large amounts of various heavy metals (the composition depending on the facility) and the pH value often bellow 2. Such pollution diminishes the biodiversity of aquatic ecosystems and also endangers human health. The aim of our study was to observe/measure the toxic effects induced by a mixture of seven heavy metals on a bioindicator species Lemna minor L. Since artificial laboratory metal mixtures cannot entirely predict behaviour of metal mixtures nor provide us with informations relating to the specific conditions in the realistic environment we have used an actual electroplating wastewater sample discharged from a small electroplating facility. In order to obtain three more samples with the same composition of heavy metals but at different concentrations, the original electroplating wastewater sample has undergone a purification process. The purification process used was developed by Orescanin et al. [Orescanin V, Mikelić L, Lulić S, Nad K, Rubcić M, Pavlović G. Purification of electroplating wastewaters utilizing waste by-product ferrous sulphate and wood fly ash. J Environ Sci Health A 2004; 39 (9): 2437-2446.] in order to remove the heavy metals and adjust the pH value to acceptable values for discharge into the environment. Studies involving plants and multielemental waters are very rare because of the difficulty in explaining interactions of the combined toxicities. Regardless of the complexity in interpretation, Lemna bioassay can be efficiently used to assess combined effects of multimetal samples. Such realistic samples should not be avoided because they can provide us with a wide range of information which can help explain many different interactions of metals on plant growth and metabolism. In this study we have primarily evaluated classical toxicity endpoints (relative growth rate, Nfronds/Ncolonies ratio, dry to fresh weight ratio and frond area) and measured guaiacol peroxidase (GPX) activity as early indicator of oxidative stress. Also, we have measured metal accumulation in plants treated with waste ash water sample with EDXRF analysis and have used toxic unit (TU) approach to predict which metal will contribute the most to the general toxicity of the tested samples.

Durability of biomass fly ash concrete: Freezing and thawing and rapid chloride permeability tests

Strict interpretation of ASTM C 618 excludes non-coal fly ashes, such as biomass fly ashes from addition in concrete. Biomass fly ash in this investigation includes (1) cofired fly ash from burning biomass with coal; (2) wood fly ash and (3) blended fly ash (wood fly ash mixing with coal fly ash). A set of experiments conducted on concrete from pure cement and cement with fly ash provide basic data to assess the effects of several biomass fly ashes on the performances of freezing and thawing (F–T) and rapid chloride permeability test (RCPT). The F–T tests indicate that all fly ash concrete has statistically equal or less weight loss than the pure cement concrete (control). The RCPT illustrate that all kinds of fly ash concrete have lower chloride permeability than the pure cement control concrete.

Biomass fly ash in concrete: Mixture proportioning and mechanical properties

ASTM C 618 prohibits use of biomass fly ashes in concrete. This document compares the properties of biomass fly ashes from cofired (herbaceous with coal), pure wood combustion and blended (pure wood fly ash blended with coal fly ash) to those of coal fly ash in concrete. The results illustrate that with 25% replacement (wt%) of cement by fly ash, the compressive strength (one day to one year) and the flexure strength (at 56th day curing) of cofired and blended biomass fly ash concrete is statistically equal to that of two coal fly ash concrete in this investigation (at 95% confidence interval). This implies that biomass fly ash with co-firing concentration within the concentration interest to commercial coal-biomass co-firing operations at power plants and blended biomass fly ash within a certain blending ratio should be considered in concrete.

Low temperature catalytic oxidation of aldehydes using wood fly ash and molecular oxygen

Aldehydes, such a 2-methylbutanal (2-MB) and 3-methylbutanal (3-MB), are odorous and regulated VOCs generated in the poultry rendering process that are ineffectively removed in chemical wet scrubbers. It was theorized that wood fly ash or selective crystalline phases in the ash could act to catalyze the oxidation of aldehydes at room temperature in the presence of ClO2, resulting in a low-cost/energy air pollution control method. Results indicate that wood fly ash catalyzed the oxidation (i.e., breakdown) of 2-MB and 3-MB both in the presence of ClO2 and with just O2 (i.e., air) itself, potentially via a free radical mechanism. Aldehyde oxidation did not occur at measurable rates without the wood fly ash or activated carbon. The presence of ClO2 did not increase the rate, but altered the end products of oxidation. Wood fly ash also catalyzed the oxidation of 2-MB in the presence of air, leading to the appearance of 2-butanone, compared to acetone from 3-MB. Contact times of 30s reduced 3-MB levels by ∼40% in bench scale, batch reactors. Similar results were found using activated charcoal (i.e., in terms of contact times), except that higher molecular weight compounds appeared to be formed. Continuous catalytic oxidation of 3-MB using wood fly ash was also demonstrated in a fixed-bed reactor at room temperature; the overall oxidation rate appeared to be first order with respect to 3-MB and a representative conversion of 20% at an inlet concentration of 67ppmv and 2s residence time (GHSV 18001/h, 25°C, 1atm) was measured. Results indicate the potential of using inexpensive solid waste materials to breakdown C5 aldehydes in rendering emissions to CO2, H2O, and less odor offensive compounds, but a carbon balance on the reaction and complete identification of end products are required for implementation.

Cytotoxicity and Mutagenicity Study of Waste and Purified Water Samples from Electroplating Industries Prepared by Use of Ferrous Sulfate and Wood Fly Ash

Toxicological safety of the new purification method for electroplating wastewaters (EWW) has been assessed. Method utilizes waste by–product ferrous sulfate and wood fly ash to scavenge heavy metals from EWW. Energy dispersive X–ray fluorescence (EDXRF) analysis of all samples met the law requirements for safe depositing of waste into the environment. The toxicity study consisted of determination of frequency of bacterial and human cell lines survival and the Ames assay (plate incorporation assay and the preincubation assay). Unexpectedly, data obtained indicate cytotoxicity and slight mutagenic potential of purified water. Ames assay showed that combination of alkalis and heavy metals present in the water purified with original fly ash and eluates of fly and waste ash were metabolically activated and conjugated with glutathione, resulting in new metabolites active and toxic for the cell. In order to reduce this effect pretreatment of fly ash (partial removal of highly soluble compounds) are necessary prior to its usage for neutralization /coagulation/flocculation processes.

Catalytic Ozonation of Gaseous Reduced Sulfur Compounds Using Wood Fly Ash

The feasibility of reusing wood ash as an inexpensive catalyst in a catalytic ozonation process has been demonstrated. Catalytic ozonation was demonstrated to oxidize H2S, methanethiol (MT), dimethyl sulfide (DMS), and dimethyl disulfide (DMDS) at low temperatures (23-25 degrees C). The process oxidized 25-50% of an inlet MT stream at 70 ppmv without the formation of DMDS (contrary to ash plus oxygen in air), oxidized 90-95% of an 85 ppmv stream of DMS, and oxidized 50% of a 100 ppmv DMDS stream using 2 g of wood ash at a space velocity of 720 h(-1) using ozone concentrations ranging from 100 to 300 ppmv. Similarly, 60-70% conversion of a 70 ppmv H2S stream was achieved with 2 g of ash in 1.1 s without catalytic deactivation (approximately 44 h). The overall oxidation rate of H2S, DMS, and DMDS increased with increasing ozone concentration contrary to the oxidation rate of MT, which was independent of ozone concentration. Dimethyl sulfoxide and dimethyl sulfone were identified as the primary end products of DMS oxidation, and SO2 was the end product of H2S and MT oxidation.

Purification of Electroplating Wastewaters Utilizing Waste By-Product Ferrous Sulfate and Wood Fly Ash

A new procedure for electroplating wastewater treatment using waste by-product (ferrous-sulfate) and waste (wood fly ash) is presented. Ferrous-sulfate was employed for Cr(VI) reduction whereas neutralization and heavy metal removal from electroplating wastewaters was performed using wood fly ash. Heavy metal removal efficiency varied from 97.5% for Cu to 99.973% for Zn. Satisfying results can be achieved already at the pH 8. The method is suitable for the purposes of wastewater treatment and disposal in compliance with environmental laws. Furthermore, it is technically simple, cost-efficient and requires less space compared to the classical methodology. According to the composition of its water extractable fraction remaining waste ash could be safely deposited on domestic waste repositories.

Properties of Controlled Low-Strength Materials Made with Wood Fly Ash

Abstract Controlled low-strength materials (CLSM) were made in the field using one source of wood fly ash as a major component. CLSM Mixtures S-1 and S-3 contained cement, wood fly ash (81 and 89%, respectively, by mass of cementitious materials [Cm]), and sand; whereas, Mixture S-2 contained cement, wood fly ash (11% of Cm), Class C coal fly ash (67% of Cm), and sand. Mixtures S-1, S-2, and S-3 showed respective compressive strength values of 0.8, 0.3, and 0.6 MPa at 28 d, and 1.4, 14.4, and 1.0 MPa at one year. Combination of wood and coal fly ashes might have caused the drastic increase in the strength of Mixture S-2 at late ages. The respective water permeability values of Mixtures S-2 and S-3 decreased from 68 and 33 μm/s at 63 d to 6 and 12 μm/s at 227 d due to the improvement of microstructure of these CLSM mixtures.

Purification of Electroplating Wastewaters Utilizing Waste By-Product Ferrous Sulfate and Wood Fly Ash

Abstract A new procedure for electroplating wastewater treatment using waste by-product (ferrous-sulfate) and waste (wood fly ash) is presented. Ferrous-sulfate was employed for Cr(VI) reduction whereas neutralization and heavy metal removal from electroplating wastewaters was performed using wood fly ash. Heavy metal removal efficiency varied from 97.5% for Cu to 99.973% for Zn. Satisfying results can be achieved already at the pH 8. The method is suitable for the purposes of wastewater treatment and disposal in compliance with environmental laws. Furthermore, it is technically simple, cost-efficient and requires less space compared to the classical methodology. According to the composition of its water extractable fraction remaining waste ash could be safely deposited on domestic waste repositories.

Characterization and electrodialytic treatment of wood combustion fly ash for the removal of cadmium

Due to a high content of macronutrients and a potential liming capacity, recycling of ashes from biomass combustion to agricultural fields as fertilisers and/or for soil improvement is considered in Denmark and other countries utilising biomass as an energy source. However, the fly ash fractions especially contain amounts of the toxic heavy metal cadmium that may exceed the limiting values for agricultural utilisation given by the Danish Environmental Protection Agency. In this work the advances of using an electrodialytic remediation method to reduce the Cd content in wood combustion fly ash—for the aim of recycling—was described. Initial characterisation of the experimental ash showed that the Cd content exceeded the limiting values for agricultural use and therefore needed treatment before being recycled. The pH in the ash was very high (13.3), and the Cd was not soluble at these alkaline conditions. However, significant amounts of Cd could be extracted at neutral to alkaline conditions using an ammonium citrate solution as a desorption agent. Electrodialytic remediation experiments showed that, under optimised remediation conditions using a mixture of ammonium citrate ( 0.25 M ) and NH 3 (1.25%) as an assisting agent, more than 70% of the initial Cd could be removed from the wood fly ash. The results also indicated that a continuous out-separation of Cd from the aqueous process solutions is possible. Thereby, recycling of the (nutrient rich) process solutions as well as of the remediated ash seems achievable.

INFLUENCE OF ASH AMENDMENT ON ODOR EMISSIONS AND AEROBIC BIODEGRADATION OF BIOSOLIDS MIXES

Controlled incubation studies (120 h at 37.C) using a mixture of 32% biosolids and 68% wood shavings (dry weight basis) amended with ash (biosolids blend:ash = 1:0.3, dry weight) were conducted to evaluate the influence of ash on odor emissions and biological activity of the mix. Three coal fly ashes (high carbon, medium carbon, and low carbon), wood fly ash, and activated carbon were evaluated against a no–ash control. The concentration of dimethyl disulfide (DMDS), dimethyl sulfide (DMS), and CO2 in the exhaust gas was measured at 0, 24, 48, 72, 96, and 120 h. Data were used to calculate emission rates and cumulative emission, which were analyzed to determine treatment differences. Results show that peak emission rates of DMDS and DMS in the no–ash control treatment were 41.9 and 1.89 .g/kg/min, respectively, while 120–h cumulative emissions were 189.95 and 11.39 mg/kg, respectively. Amendments reduced peak DMDS emission rates in all treatments. Percent reductions were highest in activated carbon and wood fly ash at 90% and 63%, respectively. For the three coal fly ashes, percent reduction ranged from 18% to 24%. Percent reduction in 120–h cumulative DMDS emission for high carbon, medium carbon, and low carbon coal ashes; wood ash; and activated carbon compared to the no–ash control were 41%, 29%, 53%, 59%, and 89%, respectively. In contrast, the peak emission rate for DMS increased while using two coal ash treatments and the wood fly ash treatment, where percent increases were 54% to 122% compared to the control. There was no difference in biological activity between treatments based on maximum CO2 production rates, which were in the range of 34 to 42 mg/kg/min. These rates correspond to 2.04 to 2.52 mg/g/hr of CO2 production, representing high biological activity.

Quantitative trace element analysis of individual fly ash particles by means of X-ray microfluorescence.

A new quantification procedure was developed for the evaluation of X-ray microfluorescence (XRF) data sets obtained from individual particles, based on iterative Monte Carlo (MC) simulation. Combined with the high sensitivity of synchrotron radiation-induced XRF spectroscopy, the method was used to obtain quantitative information down to trace-level concentrations from micrometer-sized particulate matter. The detailed XRF simulation model was validated by comparison of calculated and experimental XRF spectra obtained for glass microsphere standards, resulting in uncertainties in the range of 3-10% for the calculated elemental sensitivities. The simulation model was applied for the quantitative analysis of X-ray tube and synchrotron radiation-induced scanning micro-XRF spectra of individual coal and wood fly ash particles originating from different Hungarian power plants. By measuring the same particles by both methods the major, minor, and trace element compositions of the particles were determined. The uncertainty of the MC based quantitative analysis scheme is estimated to be in the range of 5-30%.

Wood Ash as an Amendment in Municipal Sludge And Yard Waste Composting Processes

Wood ash from a wood-fired, electrical generating plant was examined as a potential amendment in municipal biosolids and yard waste composting applications. The rate of composting and the final compost quality (chemical, physical, and plant growth characteristics) were examined. Yard waste (leaves, grass, and wood chips) and a municipal biosolids-chip mixture were either not amended or amended with wood ash at eight percent or five percent by weight, respectively, and then composted outdoors in insulated, 1700L, aerated reactors. Yard waste piles heated rapidly to 60°C within six to seven days, whereas biosolid piles heated more slowly to a maximum of 52 to 57°C within nine to 11 days. Ash had little, if any, effect on the time-temperature response. In general, ash-amended compost had higher pi I, plant nutrient, and salt contents. Tomato plants (Lycopersicum esculentum) produced 100 percent more shoot biomass in biosolids than in yard waste compost media. Poor plant growth in the yard waste compost was likely due to the high initial pH and salt content of the growth medium. In yard waste media, tomato plants germinated and produced more shoot biomass in the control compost than in the ash-amended compost.A pH neutralization study indicated that wood fly ash could be used as an economical substitute for lime which is commonly used to stabilize municipal biosolids prior to land filling or land application. Wood fly ash (pH = 13.2-13.4), when added to biosolids at a 2 to 1 ratio by weight, raised the pH of the mixture to 12.0.

Water chemistry in forested catchments after topsoil treatment with liming agents in South Sweden

Critical loads of sulphur and nitrogen are exceeded in South Sweden, and nutritional imbalances are expected to appear with time in forests. During 1984 paired catchments were established in a northwestern-southeastern gradient in South Sweden. The aim was to study long-term liming effects on throughfall, soil water, groundwater and runoff. Dolomitic limestone and wood ash were tested at one locality, Hagfors (59° N). Three adjacent catchments were used ; one reference area, one treated with dolomitic lime (0.5 kg/m 2 ) in 1985, and one with wood fly ash (0.22 kg/m 2 ) in 1988. The lime and the fly ash was granulated and applied by a helicopter in the end of May. Measurements concerning chemistry of the precipitation, throughfall, soil water and runoff has been conducted since spring 1984. The results showed that top-soil spreading of liming agents, besides the desired effects on soil chemistry, after some years also affected the quality of the recipient water. In the dolomitic lime treated catchment the positive effects were most obvious, with raised pH-, Ca-, and Mg-values and lowered Al-, Fe- and Mn-values. A positive trend regarding lower nitrogen (NO 3 - ) leaching could also be calculated. Wood ash in the used amount affected only slowly, but after six years the runoff water indicated increased pH-values as well as increased Ca- and K-values and Ca/Al-ratios. Dolomitic lime in the amounts of 0.5 kg/m 2 was concluded to be sufficient to achieve positive effects in catchments of the present type. Wood ash in the amount of 0.22 kg/m 2 , although enough for recycling purposes, was not sufficient enough in increasing pH in runoff to prevent acid leaching from the forest soils.

The Effect of pH on the Metal Concentrations Found in the Leachates of Wood Fly Ash

In these preliminary studies we report on the changes observed in the metal concentrations in the leachates of wood fly ash as a function of leachate pH. We examined three pH levels: 7, 5, and 3. One percent by weight slurry solutions of wood fly ash were agitated, monitored and maintained at a constant pH for a 24 hour interval. The elemental analysis of the solutions obtained was then determined using X-ray fluorescence spectrometry. The amounts of Si, K, Ca, Mn, Rb, Ni, Ba, Sr, and Zn found in the leachates all increased as the pH of the leaching solutions decreased. These results suggest that further studies be undertaken to determine if wood fly ash should be considered a possible hazardous waste.