Reuse options for coal fired power plant bottom ash and fly ash

Reuse options for coal fly ash and coal bottom ash are reviewed in this paper. Although, significant quantities of coal fly ash and coal bottom ash are produced worldwide every year, less than 30 % of coal ash produced is reused. Coal ash is mainly reused in civil engineering applications such as road construction, embankments, construction materials, geo-polymer applications and in cement production. Other potential reuse options for coal ash include applications such as glass ceramics, water and wastewater treatment, agriculture as well as for making high value products (e.g. telescope mirrors, break-liners, fire proof products etc.). Considering that only a small fraction of coal ash is reused, other reuse options for commercial applications need to be explored.     

Chemical,microbial and physical properties of manufactured soils produced by co-composting municipal green waste with coal fly ash

Increasing proportions of coal fly ash were co-composted with municipal green waste to produce manufactured soil for landscaping use. Only the 100% green waste treatment reached a thermophilic composting phase (?50 °C) which lasted for 6 days. The 25% and 50% ash treatments reached 36–38 °C over the same period while little or no self-heating occurred in the 75% and 100% ash treatments. Composted green waste had a low bulk density and high total and macro-porosity. Addition of 25% ash to green waste resulted in a 75% increase in available water holding capacity. As the proportions of added ash in the composts increased, the organic C, soluble C, microbial biomass C, basal respiration and activities of β-glucosidase, L-asparaginase, alkali phosphatase and arylsulphatase enzymes in the composted products all decreased. It could be concluded that addition of fly ash to green waste at a proportion higher than 25% did not improve the quality parameters of manufactured soil.     

Evaluation of fly ash as a carrier for diazotrophs and phosphobacteria

Fly ash and its different combinations with soil (w/w) were tested to explore its possible use as a potential carrier for diazotrophs and phosphobacteria. Azotobacter chroococcum, Azospirillum brasilense and Bacillus circulans showed their maximum viability in fly ash alone whereas Pseudomonas striata proliferated most in soil:fly ash (1:1) combination.     

Evaluation of bottom ash and composted manure blends as a soil amendment material

The long-term goal of this project was to find alternative uses for bottom ash (BA) and composted dairy manure (CM), by-products of coal combustion and livestock production, respectively. The study discussed in this paper focused on potential water quality impacts associated with using blended BA and CM as a soil amendment. The constituents of BA and CM include heavy metals and other chemicals that, while essential nutrients for plant growth, also pose a potential threat to water quality. Four blends (BA:CM, v/v) namely, B1 (100%:0%), B2 (70%:30%), B3 (50%:50%) and B4 (0%:100%), were subjected to flow-through water table management and two blends, B2 (70%:30%) and B3 (50%:50%), were subjected to constant head water table management using de-ionized water. Leachate and standing water from saturated and flooded blends of BA and CM were examined for total solids (TS), volatile solids (VS), COD, pH, total Kjeldahl nitrogen (TKN), NO(3)-N, total P, total K as well as selected metals over a 5 and 7 week period for flow-through and constant head watertables, respectively. The results showed that higher CM content resulted in higher TS, VS, TKN, P and K concentrations in the leachate and standing water. Concentrations of these constituents were higher in leachate than in the standing water. Even though, marked reductions of most chemicals in the leachate and standing water were realized within one to three weeks, initially high concentrations of chemicals in leachate and standing water from these particular blends made them unsuitable as soil amendment material. Based upon these results, it was concluded that additional column studies of BA and CM blends with reduced CM content (5%, 10% and 20%) should be performed to further assess the feasibility of BA and CM blends as an environmentally safe soil amendment material.     

Acidic and alkaline bottom ash and composted manure blends as a soil amendment

Potential water quality impacts associated with using bottom ash (BA) and composted dairy manure (CM) as a soil amendment were evaluated in this study. Two column studies were conducted to evaluate three blends of acidic BA and CM (BA:CM, v/v) namely, B1_ac (95:5), B2_ac (90:10), and B3_ac (80:20) and three blends of alkaline BA and CM (BA:CM, v/v), namely, B1_al (95:5), B2_al (90:10), and B3_al (80:20) under constant head water table conditions. Samples from standing water (top) and leachate (bottom) were collected at weekly intervals until day 49 to evaluate the effects of different blend ratios and elapsed time on standing water and leachate chemical and physical properties. A higher CM content in both acidic and alkaline blends resulted in higher leachate concentrations for solids and nutrients tested in this study. Alkaline blends had higher standing water and leachate nutrients concentration compared to acidic blends. After day 28, standing water total dissolved solids (TDS) concentrations for all acidic blends was below the USEPA drinking water standard however, TDS value for alkaline blend was always below the standard. Similar trends were also observed for NO₃–N and phosphorus (P) concentrations for both blends. Based on these findings, it was concluded that acidic and alkaline blends B1_ac, B1_al, B2_ac and B2_al may be considered as a soil amendment material.     

Light as an information carrier underwater

Light is a source of both energy and information for the biota.The spatial, temporal and spectral variability of light experiencedby marine phytoplankton differs significantly from that experiencedby terrestrial plants, due to the selective attenuation of solarirradiance in the aquatic medium. In the present study we analysedsuch variability and focused, in particular, on those bandswithin the spectrum that may act as potential signals for physiologicalresponses. Our results demonstrate that the spectral variationof the light field carries information on the time of day, thevertical position and the presence of very close neighbours,also underwater. This is consistent with the recent findingsof a widespread occurrence of photoreceptors in marine algae.We show also that red photoreceptors, whose presence in marinealgae was difficult to reconcile with the strong attenuationof long wavelengths by water, may be triggered at depth by thered light generated by transpectral processes.     

Aerobic microbial activity in fresh and aged bottom ashes from municipal solid waste incineration (MSWI)

Although mostly mineral, municipal solid waste incineration (MSWI) bottom ashes also contain organic matter that may support heterogeneous microbial activities. The objective of the present study was to evaluate the potential influence of such activities on the physico-chemical properties of the waste with respect to the release of contaminants into water. Fresh and aged MSWI bottom ashes originating from the same incineration plant were studied. Respirometry assays were carried out under various experimental conditions, where the microbial flora was quantitatively and qualitatively analyzed before and after the incubations. The leaching behavior of the waste was studied before and after the incubations to determine the effects of microbial activities.Relatively high O₂ consumption and CO₂ production were observed during incubation, particularly with the fresh waste which contained more organic matter and was less carbonated than the aged one. Cell counts and DGGE molecular profiles indicated the presence of an abundant and diversified microbial biomass in both aged and fresh waste. Incubations resulted in a reduction of the dissolved fraction of organic carbon in the leaching tests and a modification of the leaching patterns of many metallic species (Al, Cr, Cu, Fe, Pb and Zn). This influence on the leaching behavior was particularly significant with the fresh waste. It was mostly explained by the pH decrease due to the carbonation of the bottom ash resulting from the CO₂ generated by the microbial respiration.     

Use of bituminous coal as an alternative technique for field concentration of waterborne viruses

A filter system that sandwiches a bituminous coal preparation between two prefilters was comparable to those presently used to recover human viruses from large volumes of water. This filter was effective over a pH range of 3.0 to 7.0. Poliovirus type 1 recoveries from 100-liter seeded samples of Cincinnati tap water did not vary significantly when compared with those of identical samples processed through Filterite and Millipore filters. In studies with raw domestic sewage, virus recoveries were nearly identical from comparable samples filtered through coal and Millipore disk filters. Thus, the availability of coal makes this filter system an inexpensive analytical tool, especially in developing nations, for virus concentration.     

Presence of an unusual methanogenic bacterium in coal gasification waste

Methanogenic bacteria growing on a pilot-scale, anaerobic filter processing coal gasification waste were enriched in a mineral salts medium containing hydrogen and acetate as potential energy sources. Transfer of the enrichments to methanol medium resulted in the initial growth of a strain of Methanosarcina barkeri, but eventually small cocci became dominant. The cocci growing on methanol produced methane and exhibited the typical fluorescence of methanogenic bacteria. They grew in the presence of the cell wall synthesis-inhibiting antibiotics d-cycloserine, fosfomycin, penicillin G, and vancomycin as well as in the presence of kanamycin, an inhibitor of protein synthesis in eubacteria. The optimal growth temperature was 37 degrees C, and the doubling time was 7.5 h. The strain lysed after reaching stationary phase. The bacterium grew poorly with hydrogen as the energy source and failed to grow on acetate. Morphologically, the coccus shared similarities with Methanosarcina sp. Cells were 1 mum wide, exhibited the typical thick cell wall and cross-wall formation, and formed tetrads. Packets and cysts were not formed.     

Biodegradation of bilge waste from Patagonia with an indigenous microbial community

Oily residues that are generated in normal ship operation are considered hazardous wastes. A biodegradation assay with autochthonous microbiota of Bilge Waste Oily Phase (BWOP) was performed in a bioreactor under controlled conditions. Petroleum, diesel oil, and PAH degraders were isolated from bilge wastes. These bacteria belong to the genus Pseudomonas and are closely related to Pseudomonas stutzeri as shown by 16S rDNA phylogenetic analysis. The indigenous microbial community of the bilge waste was capable of biodegrading the BWOP (1% v/v) with biodegradation efficiencies of 70% for hexane extractable material (HEM), 68% for total hydrocarbons (TH) and 90% for total aromatics hydrocarbons (TA) in 14 days. Solid phase microextraction (SPME) was successfully applied to evaluate hydrocarbon evaporation in a control experiment and demonstrated a mass balance closure of 88%. The SPME and biodegradation results give useful information to improve and scale up the process for BWOP treatment.     

Use of bituminous coal as an alternative technique for field concentration of waterborne viruses.

A filter system that sandwiches a bituminous coal preparation between two prefilters was comparable to those presently used to recover human viruses from large volumes of water. This filter was effective over a pH range of 3.0 to 7.0. Poliovirus type 1 recoveries from 100-liter seeded samples of Cincinnati tap water did not vary significantly when compared with those of identical samples processed through Filterite and Millipore filters. In studies with raw domestic sewage, virus recoveries were nearly identical from comparable samples filtered through coal and Millipore disk filters. Thus, the availability of coal makes this filter system an inexpensive analytical tool, especially in developing nations, for virus concentration.     

Production of microbial exopolymers for application as flocculants in waste water treatment

Organic synthetic polymers such as polyacrylamide derivates, polythylenimine, Na polyacrylates etc. have received much attention as flocculating substances used in waste water treatment. There is an urgent need for the production of effective flocculants to replace mechanical separation methods or, at least, to optimize them. Biological safety and decomposition are essential pre-requisits for utilizing flocculants produced by microbial processes (e.g. discontinuous and continuous cultivation of bacteria or yeasts). The extracted polymers consisting of proteins, lipids, nucleic acids and polysaccharides are capable of being degraded easily by microbiological reactions because they are natural compounds. The induction phase of excreting cellularic biopolymers is the crucial stage. In the special literature, low pO₂ levels associated with a high concentration of the carbon source, limitation of N, P and trace elements have been recommended for the induction of excreting exopolymers. In order to ensure sufficiant induction, we preferred a special procedure, the main characteristic of it being changed between limitation and excessive supply of components essential for the growth of microorganisms. The quality control of exopolysaccharides for flocculation was determined by turbidimetric methods and sedimentation tests with caoline as a standard substance. For the initial investigations Acetobacter methanolicus and methylobacterium rhodesianum were used.     

Monitoring microbial aeroflora using vegetable waste media: an ecological aspect

For isolation of aeromicroflora in ecologically different zones, a liquid vegetable waste, deproteinised leaf juice (DLJ) was used instead of usual media. DLJ samples from three different plants, cowpea (Vigna sinensis), turnip (Brassica campestris) and radish (Raphanus sativus), were used in order to determine their efficiency as potential growth media for different types of microbes. Four different ecological zones of West Bengal, India were selected to study the aeromicroflora. The zones were as follows: (i) densely populated and industrially polluted Calcutta (CAL); (ii) plateau region of western part of the state (WEST); (iii) Terai region of Northern Bengal (TER); (iv) sandy coastal zone of Midnapore district of Southern Bengal (SB). Each zone was subdivided into three subzones. The variation in population of fungi, bacteria and actinomycetes among these zones was studied. The relative abundance and species diversities of microbes were noted. The study indicates that pollution and ecological diversity both play important roles in controlling the above two factors.     

Supramolecular self-assembly of beta-cyclodextrin: an effective carrier of the antimicrobial agent chlorhexidine

The supramolecular assembly between chlorhexidine and cyclomaltoheptaose (beta-cyclodextrin, betaCD) was characterized using NMR spectroscopy ((1)H, T(1), and ROESY), ESIMS and ITC. NMR data suggest the formation of high ordered complexes. ESIMS and ITC allowed the confirmation of the average stoichiometry as 1:4 and the thermodynamic data, also obtained by ITC, showed that the assembly is strongly stabilized by short distance interactions, but suffers a strong, opposite effect of entropy reduction. The antimicrobial activity of 1:1, 1:2, 1:3, and 1:4 Clx/betaCD molar ratio mixtures was investigated in aqueous solution and after incorporation into mucoadhesive gels. These were used to determine the initial and the long-term antimicrobial activity, respectively, toward Actinobacillus actinomycetemcomitans (A.a.) (Y4-FDC) and Enterococcus faecalis (E.f.) (ATCC 14508) strains. The results showed that A.a. and E.f. were more susceptible to the 1:4 molar ratio mixture in either solution or gel (p<0.05).     

Lyophilized allogeneic bone tissue as an antibiotic carrier

The rising number of primary joint replacements worldwide causes an increase of revision surgery of endoprostheses due bacterial infection. Revision surgery using non-cemented implants seems beneficial for the long-term outcome and the use of antibiotic-impregnated bone grafts might control the infection and give a good support for the implant. In this study we evaluated the release of antibiotics from fresh-frozen and lyophilized allogeneic bone grafts. Lyophilized bone chips and fresh frozen bone chips were mixed with gentamicin sulphate, gentamicin palmitate, vancomycin, calcium carbonate/calcium sulphate impregnated with gentamicin sulphate, and calcium carbonate/calcium sulphate bone substitute material impregnated with vancomycin. The efficacy of each preparation was measured by drug release tests and bacterial susceptibility using B. subtilis, S. aureus and methicillin-resistant Staphylococcus aureus. The release of gentamicin from lyophilized bone was similar to the release rate from fresh frozen bone during all the experimental time. That fact might be related to the similar porosity and microstructure of the bone chips. The release of gentamicin from lyophilized and fresh frozen bone was high in the first and second day, decreasing and keeping a low rate until the end of the second week. Depending on the surgical strategy either polymethylmethacrylate or allogeneic bone are able to deliver sufficient concentrations of gentamicin to achieve bacterial inhibition within two weeks after surgery. In case of uncemented revision of joint replacements allogeneic bone is able to deliver therapeutic doses of gentamicin and peak levels immediately after implantation during a fortnight. The use of lyophilized and fresh frozen bone allografts as antibiotic carriers is recommended for prophylaxis of bone infection.     

Bioremediation of coal pile run off waters using an integrated microbial ecosystem

The pH of coal pile run off was elevated from <2 to >7 and dissolved heavy metal concentrations were brought within or below drinking water standards following batch treatments utilizing a mixed culture of bacteria. Treatment tanks containing the wastewater were inoculated with the bacterial culture and appropriate media for growth. Remediation (i.e. elevated pH, change in redox, and metal precipitation) occurred in both aerated and non-aerated treatment tanks inoculated with bacteria. The bacterial culture included specific strains of Bacillus and Pseudomonas. Remediation did not occur in treatment tanks containing growth nutrients alone. © Rapid Science Ltd. 1998     

Heterogeneity as an adaptive trait of microbial populations

The review deals with heterogeneity of bacterial populations, a superorganismic characteristic providing for their adaptation to environmental conditions at the population-communication level. This phenomenon attracts increasing attention as an example of collective forms of microbial behavior and the mechanisms of cell survival in communities. Heterogeneity of bacterial populations may be discrete or continuous and may result from both phenotypic and genotypic variations. Heterogeneity of microbial cells results from the interaction of internal and environmental factors, as well as from random fluctuations of the biochemical and physiological characteristics. Cell heterogeneity improves the survival of bacterial populations under heterogeneous or variable environmental conditions, as well as under the effect of stress factors. This phenomenon should be taken into account for the development of strategies for cultivation of the biotechnologically important microorganisms and for the rational therapy of infections.