Bleached Kraft Research Articles

Studies on decolourization, degradation and detoxification of chlorinated lignin compounds in kraft bleaching effluents by Ceriporiopsis subvermispora

Ceriporiopsis subvermispora CZ-3 , a wood degrading white rot fungus, was able to decolourize and degrade the first extraction stage effluent from kraft pulp bleaching at lower co-substrate concentration than the basidiomycetes previously investigated. With glucose at 1 g l −1, this fungus removed up to 90% colour, 45% COD, 62% lignin, 32% AOX, and 36% EOX in 48 h at temperatures of 30–35°C and pH 4.0–4.5. In the absence of glucose, the fungus removed up to 62% of the colour. Significant reduction in chlorinated aromatic compounds was observed and toxicity to zebra fish was completely eliminated. The fungal mycelium could be immobilized in polyurethane foam and used repeatedly to treat batches of effluent. The molecular weight of chlorolignins was substantially reduced.

Application of photocatalytic oxidation treatment to pretreated and raw effluents from the Kraft bleaching process and textile industry

Treatability of mixed raw, coagulated and biologically pretreated textile and pulp wastewater and effluents from different process stages by enhanced heterogenous photocatalytic oxidation process was investigated. Treatment performances have been evaluated in terms of COD, TOC, BOD 5, and colour removal. Results clearly indicate that photocatalytic oxidation process enhanced with 15 mM H 2O 2 was more efficient in removal of pollutants for pretreated wastewater samples. By the application of photocatalytic treatment, 52 and 87% COD removals were obtained for biotreated Kraft bleaching and textile effluents, respectively. Addition of only 1 mM ferric ion speeded up the oxidation time of the textile effluent significantly, but it had no impact on total COD reduction. While complete colour removal of the textile wastewater was achieved within the first hour of photocatalytic treatment, complete decolourisation could not be obtained for pulp effluents, except for the coagulated wastewater throughout the reaction period. Biologically pretreated textile wastewater was found to have potential for reuse after photocatalytic treatment.

Loss of volatile organics from kraft bleaching filtrates in the evaporation/drying phase of the analysis for dissolved total solids (DTS) and dissolved volatile solids (DVS)

Measurement for describing dissolved organic matter (DOM) was needed to calibrate bleached kraft process model. Volatile solids (VS) measurement from filtered sample (DVS) was chosen as closest possible, especially because it is readily available and easy to perform. The extreme conditions of kraft chlorine dioxide bleaching filtrates (e.g. pH 2–11), however, prerequisite evaluation of the analyzing method in these circumstances. Measurements before and after evaporation/drying (SFS 3008) and redissolution showed that considerable amounts of dissolved organic carbon (DOC) escaped from acid filtrates. When identified, particularly alcohols, carboxylic acids but also aldehydes and ketons covered the majority of the disappeared quantity. According to DOC the escaped share was from 17 to 37% in the acid filtrates depending on stage (D0/D1/D2) and conditions in production process. In alkaline bleaching stage filtrates the share was 4 to 9%. The major identified volatilized compounds in D0-filtrate were methanol and formic acid. They represented 94% of the identified compounds. Identified volatilized quantity from D0-filtrate in DVS measurement represents about 4–5 kg per metric air dry ton of pulp as discharge. The carbon of the identified volatilized compounds covered 63% of the loss measured as DOC. Knowledge of volatiles and process conditions is required when DVS is used for DOM description in kraft bleaching filtrates.

Reactor development for biodegradation of pentachlorophenol

Biodegradation of pentachlorophenol (PCP) by the free-cell and polyurethane immobilized white-rot fungus Trametes versicolor was investigated in batch and continuous bioreactors. Results with both active and deactivated fungus showed that the degradation process proceeds intracellularly after initial uptake by the mycelia. However, unpurified extracellular fluid alone showed negligible PCP degradation. The polyurethane immobilized T. versicolor fungal bioreactor, previously demonstrated for the treatment of kraft bleach plant effluents, yielded greater than a 99% removal within 12 h for inlet PCP concentrations ranging from 20 to 25 mg/l. A substrate inhibition model adequately described PCP degradation kinetics in the prepolymer immobilized fluidized bed bioreactor system.

The effects of surface extractives and lignin on the surface energy of eucalypt kraft pulp fibres

This study focuses on the surface chemical composition, the surface energy, and the acid-base characteristics of lignin, cellulose, and eucalypt kraft pulps, and on the effects of changes in the surface chemical compositions on the dispersive components of the surface energy and acid-base characteristics of eucalypt pulp fibres. Surface chemical compositions, the dispersive component of the surface energy, and acid-base characteristics of Eucalyptus regnans soda lignin, cellulose, and bleached and unbleached eucalypt kraft pulps were investigated using X-ray photoelectron spectroscopy (XPS), inverse gas chromatography (IGC), and the Wilhelmy method. The dispersive component of lignin was found to be lower than that of cellulose. Measurements of the acid-base interactions of cellulose and lignin with acidic and basic probes showed that whereas cellulose is predominantly acidic, lignin is more evenly bipolar. XPS measurements of unbleached eucalypt kraft pulps indicated that there was a concentration of lignin and extractives at the surface. The presence of these materials on the fibre surface has the general effect of decreasing the surface energy of the fibres. Soxhlet extraction was employed to remove the extractives from the surface of the fibres so that the effect of the extractives and lignin on the surface energetics could be studied separately. Good correlations were found in most cases between the fibre surface energies obtained by IGC and single-fibre/water contact angles obtained by the Wilhelmy method. However, in one case, this correlation broke down; this was attributed to the high sensitivity of IGC to high-energy sites on the pulp surface.

Loss of volatile organics from kraft bleaching filtrates in the evaporation/drying phase of the analysis for dissolved total solids (DTS) and dissolved volatile solids (DVS)

Measurement for describing dissolved organic matter (DOM) was needed to calibrate bleached kraft process model. Volatile solids (VS) measurement from filtered sample (DVS) was chosen as closest possible, especially because it is readily available and easy to perform. The extreme conditions of kraft chlorine dioxide bleaching filtrates (e.g. pH 2–11), however, prerequisite evaluation of the analyzing method in these circumstances. Measurements before and after evaporation/drying (SFS 3008) and redissolution showed that considerable amounts of dissolved organic carbon (DOC) escaped from acid filtrates. When identified, particularly alcohols, carboxylic acids but also aldehydes and ketons covered the majority of the disappeared quantity. According to DOC the escaped share was from 17 to 37% in the acid filtrates depending on stage (D0(/D1/D2) and conditions in production process. In alkaline bleaching stage filtrates the share was 4 to 9%. The major identified volatilized compounds in D0-filtrate were methanol and formic acid. They represented 94% of the identified compounds. Identified volatilized quantity from D0-filtrate in DVS measurement represents about 4–5 kg per metric air dry ton of pulp as discharge. The carbon of the identified volatilized compounds covered 63% of the loss measured as DOC. Knowledge of volatiles and process conditions is required when DVS is used for DOM description in kraft bleaching filtrates.

AOX reduction of kraft bleach plant effluent by chemical pretreatment—Pilot-scale trials

Laboratory tests indicate that the adsorbable organic halogen (AOX) in bleached kraft pulp mill effluent can be reduced by about 30% by an alkaline sulphide chemical treatment. Pilot-scale trials, consisting of chemical pretreatment of effluent with green liquor followed by air activated sludge biological treatment, were conducted to evaluate this chemical treatment process. The chemical pretreatment reduced the AOX in the acid effluent by 50%, thus reducing the AOX in the influent to the biological treatment plant by 30%, in agreement with the laboratory tests. The performance of the biological treatment was not adversely affected by the chemical pretreatment in terms of COD, BOD and AOX removal. The percent AOX reduction by combined chemical and biological treatment ranged from 53 to 59% depending on the operating conditions of the biological treatment plant. The chemical pretreatment significantly enhanced the overall treatment versus biological treatment alone.

Kraft Pulping Properties ofAcacia mearnsiiandEucalyptus grandisGrown in Zimbabwe

SYNOPSIS Pulpwood samples from 8-year old Acacia mearnsii and Eucalyptus grandis plantations grown in Zimbabwe were evaluated for kraft pulping, bleaching and papermaking properties. The possibility of co-pulping the two species was also investigated. A. mearnsii had higher chip basic density than E. grandis, and required more active alkali to produce less pulp. At about the same Kappa number, the A. mearnsii pulp had lower strength properties but higher opacity. Pulps of both species could be bleached to an acceptable brightness. The results demonstrated that the conventional prejudice against the use of A. mearnsii as pulpwood in Zimbabwe may be undeserved. The species has superior pulpwood productivity and can be successfully co-pulped with E. grandis, the preferred hardwood pulpwood species in Zimbabwe.

Characterization of a Ca-alginate-immobilized Trametes versicolor bioreactor for decolorization and AOX reduction of paper mill effluents

The reduction of color and adsorbable organic halides (AOX) from the kraft bleach plant effluents was investigated using a laboratory-scale fungal bioreactor. The fungal bioreactor, containing calcium-alginate-entrapped white-rot fungus Trametes versicolor, was developed and evaluated for continuous color and AOX reduction. A color reduction percentage of 69% (±6%) and AOX reduction percentage of 58% (±6%) were achieved using caustic stage effluent as bioreactor feed at a residence time of 1 day. Retention time, inlet liquor concentration and fungal bead size were investigated for their effect on biodegradation. Percentage reductions of color and AOX ranging from 61%(±5%) to 72%(±2%) and 54%(±4%) to 49%(±2%), respectively, were observed using combined (caustic and acidic stages) effluent as bioreactor feed. Scanning electron microscopy studies showed that the immobilized mycelia was localized to a limited thickness near the outer surface of the polymer bead.

我が国紙パルプ産業のダイオキシン対策結果について

The Japan Paper Association (JPA) established the guideline for dioxin measures on December 20th in 1990 to prevent dioxin pollution of effluent discharged from bleached kraft and/or dissolving sulfite pulp mills. All mills cleared the selfimposed standard of less than AOX 1.5 kg per one ton of bleached pulp before the end of 1993. The standard was completely attained by the deadline. The JPA measured dioxins concentration of effluent from the bleached pulp and paper mills to examine effects of AOX reduction in March 1996 and it was confirmed that dioxins in effluent of these mills was decreased to 86% in average concentration and to 96% in weight as compared with those in the year of 1991. Also it was observed that no relationship existed between dioxins and AOX under such extremely low concentration of dioxins.

Adsorption effects in the decolorization of a Kraft bleach plant effluent by Phanerochaete chrysosporium

Phanerochaete chrysosporium was proposed for the decolorization and degradation of chlorinated compounds (AOX) present in the E1 stage effluent of the Kraft process. We observed that pellets of the fungus inoculated in the E1 effluent, not supplemented with nutrients, strongly absorb colour and AOX. The data were in agreement with a model describing a multilayer adsorption.

Use of Raw and Composted Paper Sludge as a Soil Additive or Mulch for Cottonwood Plants

Pulp and paper sludge is a by-product of paper production and may be suitable in agricultural applications as a soil amendment or mulch. The objective of this study was to evaluate raw and composted pulp and paper sludge as soil additives or mulches for cottonwood plants. Primary sludge, a combination of by-products from bleached kraft and neutral sulfite semichemical paper, was mixed with tailings, slaughterhouse paunch, and 10 percent wood ash (by volume), and used raw or composted and cured in the field for 39 weeks. Cuttings of two cottonwood (Populus deltoides Bartr. ex Marsh) clones were planted in a field soil (Quincy loamy fine sand) that was mixed (incorporated) or mulched (placed on top the soil) with raw or composted sludge mixtures at application rates of 0,45,90, 135 and 180 Mg/ha. The plants were grown in a plastic house for nine weeks. Electrical conductivity (EC), cation exchange capacity (CEC), soluble Cl and extractable Na in soil amended with 180 Mg/ha of compost were 37, 22, 197 and 13...

Toxicity of kraft bleaching plant effluent to aceticlastic methanogens

The toxicity of kraft bleaching plant effluent to aceticlastic methanogens was investigated in batch assays, using an anaerobic serum bottle technique. The effluent was found to exhibit a strong inhibition of the anaerobic conversion of acetate to methane and carbon dioxide, expressed as a long lag-phase before methanogenesis started. The inhibitory compounds were shown to have a low molecular mass and to have their origin in the acidic part-stream of the bleaching plant effluent. The methanogens seemed not to be able to acclimate to the inhibitory compounds, but the toxicity was found to be bacteriostatic rather than bacteriocidal. The inhibitory compounds were found to be degraded slowly in the batch experiments, finally reaching non-toxic levels so that methane production could start. The toxicity of the chlorinated acetic acid analogues mono-, di- and trichloro-acetic acid were studied. These compounds were found not to contribute significantly to the methanogenic toxicity of kraft bleaching plant effluents.

PCBs, dioxins and furans in Hooded Merganser ( Lophodytes cucullatus), Common Merganser ( Mergus merganser) and mink ( Mustela vison) collected along the St.Maurice River near La Tuque, Quebec

A pulp and paper mill located in La Tuque on the St.Maurice River, Quebec, and using the kraft bleaching process was historically the largest pulp and paper industry point source of chlorinated dibenzo- p-dioxins and dibenzofurans in Quebec. A study was undertaken to document the bioaccumulation of PCBs, dioxins and furans in piscivorous birds and mammals in this area. Hooded and Common Merganser eggs were collected in nest boxes along the St.Maurice River and Common Merganser fledglings were collected at two sites on the river. Wild minks were trapped along the St.Maurice River and in a control area upstream. Analysis of pooled merganser eggs showed contamination with dioxins, furans and PCBs. Liver samples of fledglings were contaminated with 2,3,7,8-tetrachlorodibenzofuran at the downstream site. Analysis of mink livers showed a significant higher contamination with dioxins and furans in some downstream samples compared with the upstream samples.

Studies on the treatment of kraft bleaching effluents with lignin-degrading fungi

Typically, for production of high brightness pulp, the residual lignin in unbleached kraft pulp is commonly removed through a multi-stage bleaching process with the use of chlorine species. The effluent from such a bleaching process is dark brown due to their content of chromophoric and polymeric lignin derivaties. Moreover, the organically bound chlorine [measured as total organically bound chlorine (TOCI) or adsorbable organic halogen (AOX)) is present in a wide range of organic materials which have toxic and mutagenic properties. It has recently been discovered that small quantities of dioxines [polychlorinated dibenzo dioxin (PCDD) and polychlorinated dibenzo furan (PCDF)) can also appear in bleach plant effluents. Consequently, this bleaching effluent is not easily recycled within a mill recovery system because of the potential corrosion problems created by its high chlorine content and finally affects the harmful effects on the environment. The purpose of the present research is to describe the decolorization of the El effluent with white-rot fungi showing the Iigninolytic activity, to accomplish efficient treatment of kraft bleachery efficient with less energy and in relatively short treatment-period. First, it was attempted to design the effective treatment process of the El effluent with the fungus IZU-154 showing ligninolytic activity. It has revealed that the color of the effluent was effectively removed when glucose was added as an additive. Furthermore, the addition of glucono-d-lactone to the El effluent produced a more remarkable degree of decolorization than did that of glucose. All white-rot fungi tested showed high decolorization effect of the El effluent in the presence of glucono-d-lactone. It is suggested that the effect of glucono-d-Iactone on the high decolorization of El effluent are closely associated with the activity of the surfaces of the mycelium due to the change of pH of the effluent during fungal treatment. Moreover, to establish a more practical system for the decolorization of the bleaching effluent, a screening have been performed to find fungi having high decolorization activity of the El effluent without any additional nutrients. The

Enhancement of Bleached Kraft Organochlorine Removal by Coupling Membrane Filtration and Anaerobic Treatment

This paper illustrates the feasibility of the anaerobic membrane bioreactor concept for the treatment of segregated kraft bleach plant wastewaters by comparing AOX removal achievable by anaerobic biological treatment, ultrafiltration, and coupled anaerobic/ultrafiltration treatment. If high rate anaerobic treatment (UASB) is used as the base case for comparison, then long term AOX removal efficiencies of more than 48% in the other two systems would be indicative of superior performance. Similarly, the accumulation of less than 5% of the influent AOX in the reactor contents would result in lower levels of AOX in any waste streams removed from the systems for disposal. Judging from the long term cumulative mass balance data, AOX removal efficiencies were improved with the application of both ultrafiltration (54%) and anaerobic membrane bioreactor treatment (61%). However, the improvement in AOX removal achieved with ultrafiltration and anaerobic membrane bioreactor treatment was, at best, modest. Since it w...

Reply to Comment on "Nonpurgeable Total Organic Halide Analysis and the Characterization of River Water Quality Adjacent to the Discharge from a Kraft Mill"

Examination of river water quality dowstream of the outfall from a kraft mill has shown that the mill effluent water (bleach liquor) confins significant amounts of chlorinated organic compounds. These compounds, which appear to be polymeric in nature, may be indirectly detected in the river water using the nonpurgeable total organic halide (NPTOX) test. Approximately 30% of the chlorinated organic content of the river is confined in an acid insoluble material (Fenextract), which was separated from the other components in a river-water sample by pH adjustment. Fenextract appears to be a macromolecular chlorinated thiolignin that is formed in the kraft bleaching process when chlorine dioxide is the primary oxidizing agent

Anaerobic and Aerobic Treatment for AOX Removal

A two-year study has focused on AOX removal from bleaching wastewaters in anaerobic and aerobic biological treatment, using bench scale bioreactors operated in parallel and in series. Significantly higher removals have been found in anaerobic than in aerobic treatment. Earlier work with dilute kraft bleaching wastes has been extended in additional laboratory tests and at a nearby kraft mill. 50-75% fractions of bleaching wastes were treated. Toxicity in the anaerobic process was encountered at 85% bleach waste fractions. Total AOX removal experienced in aerobic treatment is 30-35%, in anaerobic treatment 40-45%, and in an anaerobic/aerobic sequence 50-55%. Percentage removals were not sensitive to the fraction of bleaching wastewater. Several process modifications were attempted to try to obtain higher removals with only marginal success. Studies at a kraft mill confirmed the AOX removals that had been found in lab studies. AOX removal occurs by several mechanisms. There is a very significant chemical or abiotic degradation that occurs after neutralization, perhaps enhanced by reductants or other inorganic salts. Biological processes are much more significant in anaerobic than in aerobic treatment. Anaerobic reductive dehalogenation affects specific chlorinated compounds and catalyzed AOX degradation is facilitated by reduced coenzymes that are produced by bacteria. Removal by sorption or insolubilization is relatively minor in aerobic and anaerobic processes.

Anaerobic treatment of kraft bleaching plant effluent

Anaerobic treatment of a kraft bleaching plant effluent was studied with focus on the removal of chlorinated organic compounds and biochemical O2 demand (BOD). Experiments were carried out using a laboratory-scale anaerobic fixed-film process operated at different hydraulic retention times (HRTs). The process efficiently removed a variety of chloro-organic compounds when the HRT was 10 h or longer. However, a very long treatment time was required for significant removal of chlorofor; in fact, at the shortest HRT tested (6 h), there was a net production of chloroform. The overall removal of organically bound chlorine, measured as adsorbable organic halogens, was about 50%, and 60% removal of the extractable organic chlorine was achieved at an HRT of 15 h. About 70% of the BOD7 and 20% of the chemical O2 demand (COD) were removed. Up to 0.19 Nl of methane was produced per gram of COD removed by the treatment. When th HRT of the anaerobic process was shortened from 10 to 6 h, the methane production ceased.

A comparison of biological and thermo-alkaline treatment for the removal of chlorinated organic matter from kraft bleach plant effluent

A comparison of biological and thermo-alkaline treatment for the removal of chlorinated organic matter from kraft bleach plant effluent