The microbiological destruction of thiocyanate in activated sludge plants treating coke oven effluent

The treatment of effluents produced during the manufacture of metallurgical coke is normally carried out using the activated sludge process. The efficiency of activated sludges in purifying coke oven effluent depends largely on the maintenance of species of micro-organisms which destroy thiocyanate. The composition, production, toxicity and treatment of coke oven effluent at Corby steelworks are described. A review is presented which follows the progress made towards identifying and monitoring the species of bacteria which destroy thiocyanate in biological treatment plants purifying coke oven effluents. In the present study a search for bacteria capable of destroying thiocyanate led to the isolation of a species of bacteria, identified as Pseudomonas putida, which destroyed thiocyanate in the presence of succinate; this species had not previously been reported to use thiocyanate. Washed cell suspensions of P. putida destroyed phenol and thiocyanate simultaneously and thiocyanate destruction was not suppressed by pyridine, aniline or catechol at the highest concentrations normally encountered in coke oven effluent. The isolate has been included, as N.C.I.B. 11198, in the National Collection of Industrial Bacteria, Torrey Research Station, Aberdeen. Three other isolates, identified as Achromobacter sp., Thiobacillus thioparus and T. denitrificans, were also confirmed to destroy thi.ocyanate. A technique has been developed for monitoring populations of different species of bacteria in activated sludges. Application of this technique to laboratory scale and full scale treatment plants at Corby showed that thiobacilli were usually not detected; thiobacilli were el~inated during the commissioning period of the full scale plant. However experiments using a laboratory scale plant indicated that during a period of three weeks an increase in the numbers of thiobacilli might have contributed to an improvement in plant performance. Factors which might have facilitated the development of thiobacilli are discussed. Large numbers of fluorescent pseudomonads capable of using thiocyanate were sometimes detected in the laboratory scale plant. The possibility is considered that catechol or other organic compounds in the feed-liquor might have stimulated fluorescent pseudmonads. Experiments using the laboratory scale plant confirmed that deteriorations in the efficiency of thiocyanate destruction were sometimes caused by bulking sludges, due to the excessive growth of fungal floes. Increased dilution of the coke oven effluent was a successful remedy to this difficulty. The optimum operating conditions recommended by the manufacturer of the full scale activated sludge plant at Corby are assessed and the role of bacterial monitoring in a programme of regular monitoring tests is discussed in relation to the operation of activated sludge plants treating coke oven effluents.

The chemical structure and mechanical properties of phenolic resins and related polymers

Paper-based phenolic laminates are used extensively in the electrical industry. Many small components are fabricated from these materials by the process known as punching. Recently an investigation was carried out to study the effect of processing variables on the punching properties. It was concluded that further work would be justified and that this should include a critical examination of the resin properties in a more controlled and systematic manner. In this investigation an attempt has been made to assess certain features of the resin structure in terms of thermomechanical properties. The number of crosslinks in the system was controlled using resins based on phenol and para-cresol formulations. Intramolecular hydrogen bonding effects were examined using substituted resins and a synthetically derived phenol based on 1,3-di-(o-hydroxyphenyl) propane.. A resin system was developed using the Friedel Crafts reaction to examine inter-molecular hydrogen bonding at the resin-paper interface. The punching properties of certain selected resins were assessed on a qualitative basis. In addition flexural and dynamic mechanical properties were determined in a general study of the structure-property relationships of these materials. It has been shown that certain features of the resin structure significantly influenced mechanical properties. :F'urther, it was noted that there is a close relationship between punching properties, mechanical damping and flexural strain. This work includes a critical examination of the curing mechanism and views are postulated in an attempt to extend knowledge in this area of the work. Finally, it is argued that future work should be based on a synthetic approach and that dynamic mechanical testing would provide a powerful tool In developing a deeper understanding of the resin fine structure.

Stabilisation of polypropylene using polymer-bound antioxidants

variety of hindered phenol and hindered piperidine antioxidants containing vinyl or vinylidine functional groups have been synthesised and some of these were successfully bound to Polypropylene backbone during processing operations in presence of a radical generator. Up to 20% concentrates were prepared using this technique. Commercially acceptable concentrates (MASTERBATCHES) can only be prepared with antioxidants that are only weakly chain breaking such as hindered piperidines. One of the antioxidants, AATP was found to polymrise as well as bind to Polypropylene. Bound antioxidants were found to be resistant to such channels of physical loss as solvent extraction. Temperature and concentration of the additive and radical generator were found to be important parameters in the preparation of the concentrates. The stabilising efficiences of the diluted bound antioxidants alone, and in combination (synergistic) with other antioxidants have been evaluated. Results of both thermal and photo-oxidative stabilities of the bound samples in Polypropylene show that the restriction on free mobility of the bound antioxidants in the polymer has virtually no effect on its stabilising efficiency. Bound AATP was found to generate nitroxyl radicals during the course of its stabilising activities, and in combination with a small amount of Irganox 1076, it was shown to be highly synergistic thermally. A mechanism of catalytic phenol regeneration by the resultant piperidine hydroxylamine was proposed. Although the mechanical properties of the masterbatches were affected by the transformation, this was not found to be carried over to the diluted samples. This work has shown that bound concentrates can be effectively prepared in saturated polymers for subsequent dilution to normal concentrates used in commercial stabilisation.

A dynamic model for the activated sludge treatment of coke oven effluents

This is an Inter-Disciplinary Higher Degree (IHD) thesis about Water Pollution Control in the Iron and Steel Industry. After examining the compositions, and various treatment methods, for the major effluent streams from a typical Integrated Iron and Steel works, it was decided to concentrate investigative work on the activated-sludge treatment of coke-oven effluents. A mathematical model of this process was developed in an attempt to provide a tool for plant management that would enable improved performance, and enhanced control of Works Units. The model differs from conventional models in that allowance is made for the presence of two genera of microorganisms, each of which utilises a particular type of substrate as its energy source. Allowance is also made for the inhibitive effect of phenol on thiocyanate biodegradation, and for the self-toxicity of the bacteria when present in a high substrate concentration environment. The enumeration of the kinetic characteristics of the two groups of micro-organisms was shown to be of major importance. Laboratory experiments were instigated in an attempt to determine accurate values of these coefficients. The use of the Suspended Solids concentration was found to be too insensitive a measure of viable active mass. Other measures were investigated, and Adenosine Triphosphate concentration was chosen as the most effective measure of bacterial populations. Using this measure, a model was developed for phenol biodegradation from experimental results which implicated the possibility of storage of substate prior to metabolism. A model for thiocyanate biodegradation was also developed, although the experimental results indicate that much work is still required in this area.

The measurement and significance of ATP pools in activated sludge treating coke oven liquors

Coke oven liquor is a toxic wastewater produced in large quantities by the Iron and Steel, and Coking Industries, and gives rise to major effluent treatment problems in those industries. Conscious of the potentially serious environmental impact of the discharge of such wastes, pollution control agencies in many countries have made progressively more stringent quality requirements for the discharge of the treated waste. The most common means of treating the waste is the activated sludge process. Problems with achieving consistently satisfactory treatment by this process have been experienced in the past. The need to improve the quality of the discharge of the treated waste prompted attempts by TOMLINS to model the process using Adenosine Triphosophnte (ATP) as a measure of biomass, but these were unsuccessful. This thesis describes work that was carried out to determine the significance of ATP in the activated sludge treatment of the waste. The use of ATP measurements in wastewater treatment were reviewed. Investigations were conducted into the ATP behaviour of the batch activated sludge treatment of two major components of the waste, phenol, and thiocyanate, and the continuous activated sludge treatment of the liquor itself, using laboratory scale apparatus. On the basis of these results equations were formulated to describe the significance of ATP as a measured activity and biomass in the treatment system. These were used as the basis for proposals to use ATP as a control parameter in the activated sludge treatment of coke oven liquor, and wastewaters in general. These had relevance both to the treatment of the waste in the reactor and to the settlement of the sludge produced in the secondary settlement stage of the treatment process.

Stabilisation of metallocene ethylene-1-octene copolymers during multiple extrusions

The melt stabilising efficiency of antioxidants with different structures based on hindered phenols, phosphite esters, phosphonite and a lactone was examined during multi-pass extrusions at 265 °C in three metallocene ethylene-1-octene copolymers (m-LLDPE) having different extent of short chain branching (SCB) and one Zeigler copolymer (z-LLDPE) containing the same level of SCB corresponding to one of the m-LLDPE polymers. The effect of the different antioxidants, when used separately and in combination, was investigated by characterising the changes in the polymer's rheological behaviour, colour formation and structural changes based on unsaturated groups and carbonyl content during five multi-pass extrusions. The results showed that all stabilisation systems examined offered higher efficiency in the metallocene polymers compared to the Zeigler. The effect of the extent of SCB in the metallocene polymers on the stabilising efficacy of the antioxidant systems was also examined, and it was shown that it had a significant effect, with both single and combinations of antioxidants giving higher efficiency in the m-LLDPE polymer containing higher extent of SCB. The presence of the lactone HP136 in mixtures containing hindered phenol–phosphite antioxidant systems gave a higher melt stabilisation efficiency than in its absence and this has been attributed to a co-operative antioxidant reaction steps that take place between the antioxidants resulting in the possible regeneration of the lactone antioxidant through a redox reaction. In all the metallocene PE polymers examined, the biologically hindered phenol, Irganox E, was shown to be more effective than the conventionally hindered phenol Irganox 1076, when examined alone or in combination with phosphite esters.

Production of renewable phenolic resins by thermochemical conversion of biomass: a review

This review covers the production and utilisation of liquids from the thermal processing of biomass and related materials to substitute for synthetic phenol and formaldehyde in phenol formaldehyde resins. These resins are primarily employed in the manufacture of wood panels such as plywood, MDF, particle-board and OSB. The most important thermal conversion methods for this purpose are fast pyrolysis and vacuum pyrolysis, pressure liquefaction and phenolysis. Many feedstocks have been tested for their suitability as sources of phenolics including hard and softwoods, bark and residual lignins. Resins have been prepared utilising either the whole liquid product, or a phenolics enriched fraction obtained after fractional condensation or further processing, such as solvent extraction. None of the phenolics production and fractionation techniques covered in this review are believed to allow substitution of 100% of the phenol content of the resin without impacting its effectiveness compared to commercial formulations based on petroleum derived phenol. This survey shows that considerable progress has been made towards reaching the goal of a price competitive renewable resin, but that further research is required to meet the twin challenges of low renewable resin cost and satisfactory quality requirements. Particular areas of concern are wood panel press times, variability of renewable resin properties, odour, lack of reactive sites compared to phenol and potential for increased emissions of volatile organic compounds.

A comparative study of straw, perennial grasses and hardwoods in terms of fast pyrolysis products

The aim of this study is to characterise and compare fast pyrolysis product yields from straw, high yielding perennial grasses and hardwoods. Feedstocks selected for this study include: wheat straw (Triticum aestivum), switch grass (Panicum virgatum), miscanthus (Miscanthus x giganteus), willow short rotation coppice (Salix viminalis) and beech wood (Fagus sylvatica). The experimental work is divided into two sections: analytical (TGA and Py-GC-MS) and laboratory scale processing using a continuously fed bubbling fluidized bed reactor with a capacity of up to 1 kg/h. Pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS) has been used to quantify pyrolysis products and simulate fast pyrolysis heating rates, in order to study potential key light and medium volatile decomposition products found in these feedstocks. Py-GC-MS quantification results show that the highest yields of furfural (0.57 wt.%), 2-furanmethanol (0.18 wt.%), levoglucosan (0.73 wt.%), 1,2-benzenediol (0.27 wt.%) and 2-methoxy-4-vinylphenol (0.38 wt.%) were found in switch grass, and that willow SRC produced the highest yield of phenol (0.33 wt.%). The bio-oil higher heating value was highest for switch grass (22.3 MJ/kg). Water content within the bio-oil is highest in the straw and perennial grasses and lowest in the hardwood willow SRC. The high bio-oil and char heating value and low water content found in willow SRC, makes this crop an attractive energy feedstock for fast pyrolysis processing, if the associated production costs and harvest yields can be maintained at current reported values. The bio-oil from switch grass has the highest potential for the production of high value chemicals. © 2013 Elsevier Ltd. All rights reserved.

Uncatalysed and potassium-catalysed pyrolysis of the cell-wall constituents of biomass and their model compounds

Cell-wall components (cellulose, hemicellulose (oat spelt xylan), lignin (Organosolv)), and model compounds (levoglucosan (an intermediate product of cellulose decomposition) and chlorogenic acid (structurally similar to lignin polymer units)) have been investigated to probe in detail the influence of potassium on their pyrolysis behaviours as well as their uncatalysed decomposition reaction. Cellulose and lignin were pretreated to remove salts and metals by hydrochloric acid, and this dematerialized sample was impregnated with 1% of potassium as potassium acetate. Levoglucosan, xylan and chlorogenic acid were mixed with CHCOOK to introduce 1% K. Characterisation was performed using thermogravimetric analysis (TGA) and differential thermal analysis (DTA). In addition to the TGA pyrolysis, pyrolysis-gas chromatography-mass spectrometry (PY-GC-MS) analysis was introduced to examine reaction products. Potassium-catalysed pyrolysis has a huge influence on the char formation stage and increases the char yields considerably (from 7.7% for raw cellulose to 27.7% for potassium impregnated cellulose; from 5.7% for raw levoglucosan to 20.8% for levoglucosan with CHCOOK added). Major changes in the pyrolytic decomposition pathways were observed for cellulose, levoglucosan and chlorogenic acid. The results for cellulose and levoglucosan are consistent with a base catalysed route in the presence of the potassium salt which promotes complete decomposition of glucosidic units by a heterolytic mechanism and favours its direct depolymerization and fragmentation to low molecular weight components (e.g. acetic acid, formic acid, glyoxal, hydroxyacetaldehyde and acetol). Base catalysed polymerization reactions increase the char yield. Potassium-catalysed lignin pyrolysis is very significant: the temperature of maximum conversion in pyrolysis shifts to lower temperature by 70 K and catalysed polymerization reactions increase the char yield from 37% to 51%. A similar trend is observed for the model compound, chlorogenic acid. The addition of potassium does not produce a dramatic change in the tar product distribution, although its addition to chlorogenic acid promoted the generation of cyclohexane and phenol derivatives. Postulated thermal decomposition schemes for chlorogenic acid are presented. © 2008 Elsevier B.V. All rights reserved.

Predicting success with silicone-hydrogel contact lenses in new wearers

Purpose: to evaluate changes in tear metrics and ocular signs induced by six months of silicone-hydrogel contact lens wear and the difference in baseline characteristics between those who successfully continued in contact lens wear compared to those that did not. Methods: Non-invasive Keratograph, Tearscope and fluorescein tear break-up times (TBUTs), tear meniscus height, bulbar and limbal hyperaemia, lid-parallel conjunctival folds (LIPCOF), phenol red thread, fluorescein and lissamine-green staining, and lid wiper epitheliopathy were measured on 60 new contact lens wearers fitted with monthly silicone-hydrogels (average age 36 ± 14 years, 40 females). Symptoms were evaluated by the Ocular Surface Disease Index (OSDI). After six months full time contact lens wear the above metrics were re-measured on those patients still in contact lens wear (n= 33). The initial measurements were also compared between the group still wearing lenses after six months and those who had ceased lens wear (n= 27). Results: There were significant changes in tear meniscus height (p= 0.031), bulbar hyperaemia (p= 0.011), fluorescein TBUT (p= 0.027), corneal (p= 0.007) and conjunctival (p= 0.009) staining, LIPCOF (p= 0.011) and lid wiper epitheliopathy (p= 0.002) after six months of silicone-hydrogel wear. Successful wearers had a higher non-invasive (17.0 ± 8.2. s vs 12.0 ± 5.6. s; p= 0.001) and fluorescein (10.7 ± 6.4. s vs 7.5 ± 4.7. s; p= 0.001) TBUT than drop-outs, although OSDI (cut-off 4.2) was also a strong predictor of success. Conclusion: Silicone-hydrogel lenses induced significant changes in the tear film and ocular surface as well as lid margin staining. Wettability of the ocular surface is the main factor affecting contact lens drop-out. © 2013 British Contact Lens Association.

Intermediate pyrolysis and product identification by TGA and Py-GC/MS of green microalgae and their extracted protein and lipid components

The thermo-chemical conversion of green microalgae Chlamydomonas reinhardtii wild type (CCAP 11/32C), its cell wall deficient mutant C. reinhardtii CW15 (CCAP 11/32CW15) and Chlorella vulgaris (CCAP 211/11B) as well as their proteins and lipids was studied under conditions of intermediate pyrolysis. The microalgae were characterised for ultimate and gross chemical composition, lipid composition and extracted products were analysed by Thermogravimetric analysis (TG/DTG) and Pyrolysis-gaschromatography/mass-spectrometry (Py-GC/MS). Proteins accounted for almost 50% and lipids 16-22 % of dry weight of cells with little difference in the lipid compositions between the C. reinhardtii wild type and the cell wall mutant. During TGA analysis, each biomass exhibited three stages of decomposition, namely dehydration, devolatilization and decomposition of carbonaceous solids. Py-GC/MS analysis revealed significant protein derived compounds from all algae including toluene, phenol, 4-methylphenol, 1H-indole, 1H-indole-3methyl. Lipid pyrolysis products derived from C. reinhardtii wild type and C. reinhardtii CW15 were almost identical and reflected the close similarity of the fatty acid profiles of both strains. Major products identified were phytol and phytol derivatives formed from the terpenoid chain of chlorophyll, benzoic acid alkyl ester derivative, benzenedicarboxylic acid alkyl ester derivative and squalene. In addition, octadecanoic acid octyl ester, hexadecanoic acid methyl ester and hydrocarbons including heptadecane, 1-nonadecene and heneicosane were detected from C. vulgaris pyrolysed lipids. These results contrast sharply with the types of pyrolytic products obtained from terrestrial lignocellulosic feedstocks and reveal that intermediate pyrolysis of algal biomass generates a range of useful products with wide ranging applications including bio fuels.

Thermo-chemical behaviour and chemical product formation from Polar seaweeds during intermediate pyrolysis

Fundamental analytical pyrolysis studies of biomass from Polar seaweeds, which exhibit a different biomass composition than terrestrial and micro-algae biomass were performed via thermogravimetric analysis (TGA) and pyrolysis-gas chromatography/mass-spectrometry (Py-GC/MS). The main reason for this study is the adaptation of these species to very harsh environments making them an interesting source for thermo-chemical processing for bioenergy generation and production of biochemicals via intermediate pyrolysis. Several macroalgal species from the Arctic region Kongsfjorden, Spitsbergen/Norway (Prasiola crispa, Monostroma arcticum, Polysiphonia arctica, Devaleraea ramentacea, Odonthalia dentata, Phycodrys rubens, Sphacelaria plumosa) and from the Antarctic peninsula, Potter Cove King George Island (Gigartina skottsbergii, Plocamium cartilagineum, Myriogramme manginii, Hymencladiopsis crustigena, Kallymenia antarctica) were investigated under intermediate pyrolysis conditions. TGA of the Polar seaweeds revealed three stages of degradation representing dehydration, devolatilization and decomposition of carbonaceous solids. The maximum degradation temperatures Prasiola crispa were observed within the range of 220-320 C and are lower than typically obtained by terrestrial biomass, due to divergent polysaccharide compositions. Biochar residues accounted for 33-46% and ash contents of 27-45% were obtained. Identification of volatile products by Py-GC/MS revealed a complexity of generated chemical compounds and significant differences between the species. A widespread occurrence of aromatics (toluene, styrene, phenol and 4-methylphenol), acids (acetic acid, benzoic acid alkyl ester derivatives, 2-propenoic acid esters and octadecanoic acid octyl esters) in pyrolysates was detected. Ubiquitous furan-derived products included furfural and 5-methyl-2-furaldehyde. As a pyran-derived compound maltol was obtained by one red algal species (P. rubens) and the monosaccharide d-allose was detected in pyrolysates in one green algal (P. crispa). Further unique chemicals detected were dianhydromannitol from brown algae and isosorbide from green algae biomass. In contrast, the anhydrosugar levoglucosan and the triterpene squalene was detected in a large number of pyrolysates analysed. © 2013 Elsevier B.V. All rights reserved.

Novel reaction products from the hypervalent iodine oxidation of hydroxylated stilbenes and isoflavones

Novel reaction pathways for the hypervalent iodine-mediated oxidation of bioactive phenols containing extended conjugated π-systems are described. Oxidation of 4-hydroxystilbenes in methanol using a hypervalent iodine-based oxidant led to the formal 1,2-addition of methoxy groups across the central stilbene double bond. Treatment of the structurally related 4-hydroxyisoflavone with di(trifluoroacetoxy)iodobenzene leads to the surprising formation of 2,4′-dihydroxybenzil. Potential mechanisms for these new reaction pathways are discussed, and the X-ray crystal structure of 2,4′-dihydroxybenzil is presented. In contrast, oxidation of the corresponding 3-hydroxystilbenes and 3-hydroxyisoflavone led to conventional dienone oxidation products. The antitumour implications of these oxidation processes are briefly highlighted; the novel 4-substituted phenolic oxidation products were found to be inactive in terms of in vitro antitumour cellular activity, whereas the 3-substituted phenol products gave novel agents with potent and enhanced antitumour activity in the HCT 116 cancer cell line. © The Royal Society of Chemistry 2005.

Pyrolysis study of halogen-containing aromatics reflecting reactions with polypropylene in a posttreatment decontamination process

Halogen-containing aromatics, mainly bromine-containing phenols, are harmful compounds contaminating pyrolysis oil from electronic boards containing halogenated flame retardants. In addition, theirformation increases the potential for evolution of polybrominated dibenzo-p-dioxins (PBDDs) and dibenzofurans (PBDFs) at relatively low temperature (up to 500 °C). As a model compound, 2,4-dibromophenol (DBP) was pyrolyzed at 290-450 °C. While its pyrolysis in a nitrogen flow reactor or in encapsulated ampules yields bromine-containing phenols, phenoxyphenols, PBDDs, and PBDFs, pyrolysis of DBP in a hydrogen-donating medium of polypropylene (PP) at 290-350 °C mainly results in the formation of phenol and HBr, indicating the occurrence of a facile hydrodebromination of DBP. The hydrodebromination efficiency depends on temperature, pressure, and the ratio of the initial components. This thermal behavior of DBP is compared to that of 2,4-dichlorophenol and decabromodiphenyl ether. A treatment of halogen-containing aromatics with PP offers a new perspective on the development of low-environmental-impact disposal processes for electronic scrap. © 2005 American Chemical Society.

Detoxification of brominated pyrolysis oils

The development of an innovative technology for the pyrolytic conversion of brominated phenols in a reductive medium aimed at product recovery for commercial use is discussed in this paper. Brominated phenols are toxic products, which contaminate pyrolysis oil of wastes from electronic and electrical equipment (WEEE). The pyrolysis experiments were carried out with 2,6-dibromophenol, tetrabromobisphenol A, WEEE pyrolysis oil and polypropylene or polyethylene in encapsulated ampoules under inert atmosphere in quasi-isothermal conditions (300-400 °C) with a different residence time (10-30 min). Optimal conditions were found to be the use of polypropylene at 350 °C with a residence time of 20 min. The main pyrolysis products were identified as HBr and phenol. A radical debromination mechanism for the pyrolytic destruction of brominated phenols is suggested. © 2003 Elsevier Science B.V. All rights reserved.