Chlorinated phenolics of bleached kraft mill origin : An olfactory evaluation

Biologically treated effluent samples from 9 Canadian bleached softwood kraft mills were analyzed for chlorinated phenolics content. Odour thresholds were determined for selected chlorinated phenolics and for a synthetic mixture of these compounds at concentrations typical of a biologically-treated bleached kraft mill effluent. Results indicate that chlorinated phenolics present in effluent discharged from bleached kraft mills are not expected to contribute an off-odour to recipient waters.     

Leeches as in situ biomonitors of chlorinated phenolic compounds. Part 2: Pulp mill investigations

Leeches (Nephelopsis obscura Verrill) were evaluated as in situ biomonitors of chlorinated phenolic compounds in the Fraser River at Prince George, BC, downstream from three bleached kraft pulp mills practising chlorine dioxide (ClO₂) substitution. Five biomonitoring periods, of 7 days duration, were selected to cover a full range of seasonal river conditions.Leeches bioconcentrated tri- and tetrachlorinated phenolics (bioconcentration factors: 465–6000) in proportions similar to those present in both mill effluent and river water. Leeches showed 3,4,5-trichloroguaiacol (3,4,5-TCG) to be the most consistent tracer of bleached kraft mill discharge. Leeches provided direct evidence that increasing ClO₂ substitution reduces amounts of chlorinated phenolics accumulated by aquatic organisms, with sharp decreases observed at ClO₂ levels greater than 90%. This study suggests that leeches could be applied as routine biomonitors for environmental impact monitoring.     

Decreasing effluent loads through bleaching modification

Almost all of the kraft pulp bleach plants worldwide are now practicing elemental chlorine-free (ECF) process to comply with environmental regulations in different countries. Usually, these conventional ECF bleaching sequences contain one or two alkaline extraction stages of which the first one is often the principal source of color and chemical oxygen demand (COD) in the resulting effluent. However, the results of this study showed that the ECF sequences which did not include any alkaline extraction stage and contained solely chlorine dioxide decreased both the color and COD loads of the effluent. On the other hand, the ECF sequences containing both chlorine dioxide and hydrogen peroxide but excluding the alkaline extraction stage could lower only the color but not the COD load. It is suggested that the total kappa factor (the ratio of the total active chlorine to the kappa number) affected the COD load and that the content of hexeneuronic acid groups influenced the color of the bleach effluent. Compared to the reference pulp, the viscosity of the pulp from the exclusively chlorine-dioxide-based ECF sequence without the alkaline extraction stage was lower but the tear index and sheet density at a given tensile index were similar.     

Factors influencing the effect of bleached kraft mill effluents on drinking water quality

The taste and odour of drinking waters contaminated with bleached kraft mill effluent (BKME) were investigated. Mill effluents with a wide range of odour thresholds were selected and the effects of biological treatment, conventional water purification, carbon filtration, residual chlorine concentration, and recipient water quality were evaluated. No correlation was found between the original odour of BKME and the drinking water impairment. The taste and odour of drinking water prepared from pure glacial-fed river water to which biotreated BKMEs from three separate pulp mills were added was found to be impaired at effluent concentrations ranging from 0.1 to 0.4%. Effluent biotreatment, conventional water purification, and carbon filtration significantly reduced, but did not completely eliminate, BKME-associated taste and odour in potable water samples. The concentration of residual chlorine in the finished drinking water samples was an important factor influencing the degree of taste impairment.     

Hepatic metallothionein level and mixed function oxidase activity in fingerling rainbow trout (Oncorhynchus mykiss) after acute exposure to pulp and paper mill effluents

Hepatic metallothionein (MT) levels and mixed function oxidase (MFO) activity (7-ethoxyresorufin-o-deethylase or EROD) were measured in fingerling rainbow trout (Oncorhynchus mykiss) exposed to sublethal concentrations of 12 pulp and paper effluents, after completion of 96 h static acute lethality assays. Barring one primary-treated effluent where MFO levels were significantly depressed and two secondary-treated effluents where no significant MFO induction were observed, all other effluents triggered significant induction of MT and EROD, regardless of mill process/treatment or of effluent lethality and chemical characteristics. MT and EROD inductions were significant, however, at higher concentrations for secondary-treated effluents than for primary-treated ones. Lethal (96 h LC₅₀s) to sublethal (MT and EROD lowest observable effect concentrations) ratios were variable and indicated that significant biochemical effects were present at effluent concentrations that were roughly 4–33 (MT) and 3–59 (EROD) times lower than the LC₃₀. Enzyme induction ranged from 1.3 to 2.5-fold for MT and from 1.3 to 9.4-fold for EROD compared to controls. Limited chemical data available suggest that there were indeed classes of compounds present capable of inducing MT or EROD. Observed patterns of MT/MFO responses also suggest that contaminant interactions may have interfered with induction for some of the effluents studied. Refinements of this combined (sub)lethal bioassay procedure are envisaged to determine whether it can provide an efficient means of detecting hazardous chemicals in industrial wastewaters.     

Biodegradability of kraft mill TCF biobleaching effluents: Application of enzymatic laccase-mediator system

The great amount of pollutants released from kraft pulp processes, mainly from cooking and bleaching stages, is one of the most relevant environmental problems in this type of industry. New bleaching sequences are being studied based on the use of oxidative enzymes from fungal cultures. In this study, the bleaching systems consisting of Laccase and different mediators such as 1-hydroxybenzotriazole, violuric acid, syringaldehyde and methyl syringate in the bleaching sequence of Eucalyptus globulus kraft pulp were applied. The main objective of this study is to evaluate the aerobic and anaerobic biodegradability and toxicity to Vibrium fischeri of generated L-stage and total bleaching sequence effluents.The highest levels of aerobic and anaerobic degradation of the generated effluents were achieved for treatments with laccase plus violuric acid, with 80% of aerobic degradation and 68% of anaerobic biodegradation. V. fischeri toxicity was remarkably reduced for all the effluents after aerobic degradation.     

Identification of chlorinated compounds in the spent chlorination liquor from differently treated sulphite pulps with special emphasis on mutagenic compounds

About 80 compounds present in the spent chlorination liquor from the bleaching of sulphite pulp have been identified. A comparison has been made between these compounds and those identified in kraft bleaching effluent, with special emphasis on mutagens. The influence of oxygen delignification, before chlorination and alkali treatment of the spent bleach liquor, on the composition of the liquors has also been investigated.     

Use of rat brain Na, K-ATPase assay to determine effectiveness of biological treatment to reduce toxicity of paper mill effluents

This work evaluates the toxicity of kraft mill wastewaters and the extent of detoxification attained after biological treatment of these effluents with the fungus Phanerochaete chrysosporium. The degree of inhibition of the enzyme Na⁺, K⁺-ATPase was used as an indicator of toxicity. The untreated alkali extraction stage effluent significantly inhibited the enzyme activity. When this effluent was treated biologically the degree of enzyme inhibition was practically reduced to zero. The inhibition of the enzyme Na⁺, K⁺-ATPase was found to be a suitable indicator of toxicity for bleached pulp and paper mill waste waters.     

Removal of resin acids and sterols from pulp mill effluents by activated sludge treatment

The wastewater treatment plant of an elemental chlorine free bleaching kraft pulp mill located in eastern Finland was sampled in order to study the fate of wood extractives and the toxicity to luminescence bacteria (Vibrio fischeri) in different parts of the plant. Resin acids and sterols were analyzed from water, particles and sludge samples during three different runs. Waters before biotreatment and primary sludge were found to be toxic; but in the activated sludge treatment toxicity was removed. During wastewater treatment, concentrations of wood extractives were reduced over 97%. In activated sludge treatment, over 94% of the resin acids and over 41% of the sterols were degraded or transformed to other compounds. Furthermore, in general, less than 5% of the resin acids and over 31% of the sterols were removed in biosludge to the sludge thickener. Most of the extractives were discharged attached to particles. Although some disturbing factors increased the load of wood extractives during samplings, these factors did not affect the operational efficiency of the secondary treatment system.     

Fate of wood extractives in wastewater treatment plants at kraft pulp mills and mechanical pulp mills

Extensive environmental effects of the forest industry led to implementation of activated sludge treatment of effluents in the 1980s. Although the existence of chlorinated compounds in the effluents has decreased, a discussion about the possible environmental effects of elemental-chlorine-free (ECF) and total-chlorine-free (TCF) bleached pulp mill effluents has arisen, and chronic effects on aquatic organisms have still been found. Recently, studies have mainly focussed on wood extractives and their role in the effects of effluents. Resin acids and unsaturated fatty acids are found to be toxic, and plant sterols are reported to have adverse endocrine effects on water organisms already at low concentrations. In this study, Finnish wastewater treatment plants of an ECF kraft pulp mill, a paper mill, and an integrated TCF kraft pulp and paper mill were sampled in order to ascertain how wastewater treatment plants, and especially activated sludge treatments, remove wood extractives. Concentrations of extractives in discharged wastewaters varied between 0.4 and 11 g/t kraft or mechanical pulp, and the concentrations decreased over 95% during the treatment processes. Of the wood extractives, 1.1-64% were adsorbed to biosludge and 35-99% were degraded or transformed to other forms during the activated sludge treatment. A major part of these compounds were discharged in particles (74-99%). The removal of extractives was efficient even in the effluent treatment plant, which was highly loaded during the sampling period.     

Disinfection by-products in filter backwash water: Implications to water quality in recycle designs

The overall purpose of this research was to investigate disinfection by-product (DBP) concentrations and formation potential in filter backwash water (FBWW) and evaluate at bench-scale the potential impact of untreated FBWW recycle on water quality in conventional drinking water treatment. Two chlorinated organic compound groups of DBPs currently regulated in North America were evaluated, specifically trihalomethanes (THMs) and haloacetic acids (HAAs). FBWW samples were collected from four conventional filtration water treatment plants (WTP) in Nova Scotia, Canada, in three separate sampling and plant audit campaigns. THM and HAA formation potential tests demonstrated that the particulate organic material contained within FBWW is available for reaction with chlorine to form DBPs. The results of the study found higher concentrations of TTHMs and HAA9s in FBWW samples from two of the plants that target a higher free chlorine residual in the wash water used to clean the filters (e.g., clearwell) compared to the other two plants that target a lower clear well free chlorine residual concentration. Bench-scale experiments showed that FBWW storage time and conditions can impact TTHM concentrations in these waste streams, suggesting that optimization opportunities exist to reduce TTHM concentrations in FBWW recycle streams prior to blending with raw water. However, mass balance calculations demonstrated that FBWW recycle practice by blending 10% untreated FBWW with raw water prior to coagulation did not impact DBP concentrations introduced to the rapid mix stage of a plant’s treatment train.     

Effect of chemical and physical parameters on a pulp mill biotreatment bacterial community

The bacterial community composition in an activated sludge plant treatment from a bleached kraft pulp mill was monitored over a period of 209 days. Using DGGE and terminal-Restriction Fragment Length Polymorphism (t-RFLP) analysis we generated community DNA fingerprints over the time period. Both methods produce fingerprints that can be used to monitor stability in the system and generate fragments that can be associated with bacterial taxa. Chemical and physical parameters were also collected during that same time frame. We found a number of significant correlations with influent variables such as temperature, chemical oxygen demand (COD), Biochemical oxygen demand (BOD) and chloroform concentrations suggesting that these were the most likely parameters to influence the bacterial community structure. In addition several taxa correlated to important performance indicators such as COD/BOD removals and SVI. Multivariate analysis also confirmed the strong links between taxa variation and temperature, nutrient loads, chloroform and also one class of filaments. Establishing the identity of these taxa and their ecological preferences will greatly enhance our understanding and management of biological treatment systems.     

Development of chlorine dioxide-related by-product models for drinking water treatment.

Factorial experiments were conducted using source waters from seven drinking water treatment plants in Ontario, Canada to develop statistically based model equations capable of predicting chlorine dioxide consumption and chlorite and chlorate formation upon chlorine dioxide application. The equations address raw water quality and operational parameters including pH, temperature, chlorine dioxide concentration, reaction time and water organic content (as described by non-purgeable organic carbon x ultraviolet absorbance measured at 254 nm, NPOC x UV254). Terms describing two-factor interaction effects were also included, improving the accuracy of the predictive equations in fitting measured response concentrations as evaluated through internal and external validations. Nearly 80% of the predictions for chlorine dioxide consumption and chlorite formation were observed to be within 20% of the measured levels. Over 90% of the predicted chlorate levels were within +/- 0.1 mg/L of the measured levels. Chlorine dioxide concentration and NPOC x UV254 were key parameters when developing the predictive models.     

Influence of dilution water on the toxicity of kraft pulp and paper mill effluent, including mechanisms of effect

Ten natural freshwater samples differing widely in pH and other characteristics were collected and examined for their influence as dilution waters on the acute lethality (24-h LC50 values) of a sample of bleached kraft whole mill effluent. When bioassays were conducted at the pH of each dilution water, LC50 values varied by 3.5-fold. These differences were largely accounted for by adjustment of the pH of each test solution to a common value (6.5). The remaining minor differences in LC50 values were attributed to the ionizable inorganic constituents of the dilution waters.A separate study examined the effects of test pH and the involvement of aging of solutions prior to bioassays or of pH overshoots during pH adjustment on the toxicity of a second sample of pulp mill effluent: using a single dilution water. The LC50 values obtained for bioassays conducted at pH 9.5 were significantly higher than those for tests performed at pH 6.5. Neither the adjustment of test solutions to pH 9.5 with immediate readjustment to pH 6.5, nor the prior aging of solutions at pH 9.5 or 6.5 with minimal or no aeration for 6 h, altered the differences due to test pH.The pH-toxicity relationship of the resin acid dehydroabietate and a third sample of bleached kraft whole mill effluent was similar throughout the pH range 5.0–10.5, with test solutions least toxic at pH 9.0–9.5. This pH-toxicity relationship for pulpmill effluents and the influence of dilution water pH on effluent toxicity were attributed mainly to the ionization equilibria of the effluents' resin acid constituents.     

Sequential inactivation of Cryptosporidium parvum oocysts with chlorine dioxide followed by free chlorine or monochloramine.

The main objective of this study was to assess the effect of temperature (4-30 degrees C) on the inactivation kinetics of Cryptosporidium parvum oocysts with sequential disinfection schemes involving the use of chlorine dioxide as the primary disinfectant and free or combined chlorine as the secondary disinfectant in synthetic water. The synergy previously reported for sequential inactivation of C. parvum oocysts with ozone/free chlorine or ozone/combined chlorine did not occur when chlorine dioxide was used. instead of ozone, as the primary disinfectant within the temperature range (4-30 degrees C) and the pre-treatment levels investigated. Sequential ozone/chlorine dioxide and chlorine dioxide ozone experiments revealed that the lower level or absence of synergy for chlorine dioxide/free chlorine and chlorine dioxide, monochloramine was likely the result of chlorine dioxide reacting with oocyst chemical groups that are mostly different from those reacting with ozone, free chlorine, or monochloramine. The CT concept was found to be valid for the primary inactivation kinetics of C. parvum oocysts with chlorine dioxide, thus allowing the use of the simpler CT approach for the development of C. partum inactivation requirements with chlorine dioxide. General consistency was found between the secondary inactivation kinetics of C. parvum oocysts with free chlorine and monochloramine after chlorine dioxide pretreatment obtained in this study with oocyst viability determined by a modified in vitro excystation method and those reported in the literature for the same sequential disinfection schemes based on an animal infectivity assay.     

A possible correlation between environmental chemicals and pigment cell neoplasia in fish

A croaker (Nibea mitsukurii) has a high incidence of the skin melanoma, chromatophoroma, in a Pacific coastal area in Japan. A sea catfish (Plotosus anguillaris) bearing skin melanosis is also found in the same area. For elucidation of a correlation between these pigment cell neoplasms of the skin and environmental contaminants, an epidemiological survey was conducted to determine the distribution and prevalence of tumor-bearing fish. Based upon observations of a high prevalence of skin neoplasms near the discharge point for kraft pulp mills, experiments were conducted to determine the neoplastic induction efficiency of the effluent on the croaker and sea catfish species. Isolation and identification of mutagens in effluent extracts were carried out using the Ames test, followed by mass spectral analysis of mutagenic fractions. The effluent induced a chromatophoroma on one croaker of the 100 tested, and it induced pigment cell hyperplasia on 70 to 100% of the sea catfish. These skin neoplasms were grossly similar to those observed in the field. Five chloroacetones were identified from the Ames-positive fractions of the effluent, and tetrachlorocyclopentene-1,3-dione and two alpha-dicarbonyl compounds were also detected as mutagens. The above experiments indicate that the mutagenic contaminants found in kraft mill effluent may play an important role in the induction of skin neoplastic disease in fish.     

Chlorine dioxide reactivity with nucleic acids

Studies were conducted with the bacterial virus f2 to determine the reactivity of chlorine dioxide with viral nucleic acid, and to evaluate the role of these reactions in the inactivation of virus with chloride dioxide. The effect of chlorine dioxide on naked infectious RNA was compared to the inactivation of intact virus and to infectious f2 RNA extracted from virus which was treated with chlorine dioxide. At pH 7.2 and 5°C, greater than 4 log units of virus inactivation were observed within 2 min of contact time. Almost no inactivation of infectious RNA extracted from chlorine dioxide treated virus was observed. Treatment of naked infectious RNA with chlorine dioxide yielded less than 1 log unit of inactivation after 5 min of contact time. The rate of inactivation both f2 virus and infectious RNA by chlorine dioxide increased with increasing pH.Inactivation of f2 infectious RNA was attributed to chlorine dioxide reactions with nucleotides. The reaction of chlorine dioxide within yeast RNA was uniquely associated with guanosine monophosphate (GMP). The reaction between chlorine dioxide and GMP may account for inactivation of naked f2 RNA. However, this reaction does not explain the inactivation of intact f2 virus, as the RNA within the treated virion remains infectious despite several log units of virus inactivation.     

Utilization of kraft pulp production residues in clay brick production

The main objective of this study is to investigate the utilization potential of kraft pulp production residues in clay brick. Kraft pulp production is the primary phase of the paper industry. Long cellulose fibers are produced from wood, straw and reeds in kraft pulp production. Short cellulose fibers are separated as an organic waste material from the production system. This type of residue is only utilized in agricultural purpose or in the production of moulded egg cartons. Kraft pulp production plant of Seka Company (located at Afyon-Çay/Turkey), which has 50,000 tpy dried pulp production capacity, generates important amount of organic wastes. Location of the plant is very close to brick manufacturing facilities and this is the main encouraging reason for the investigation study.One way of the increasing the insulation capacity of the brick is generating porosity in clay body. Combustible organic types of pore forming additives are most frequently used for this purpose. Due to the organic nature of pulp residue, pore-forming ability in clay body was investigated. For this purpose, increasing amount of residue (0%, 2.5%, 5% and 10 wt%) was mixed with raw brick-clay. All samples were fired at 900 °C. Effect on shaping, plasticity, density and mechanical properties were investigated. 2.5 to 5% residue additions were found to be effective for the pore forming in clay body with acceptable mechanical properties. It was observed that, fibrous nature of residue does not create any extrusion problem but increase in residue addition increased the water content for the plasticity. As a conclusion, kraft pulp residues can be utilized in brick-clay as an organic pore-forming agent and by this way it can be utilized in environmentally safe way.     

二氧化氯、氯胺顺序投加联合消毒工艺的研究

以天津市某自来水厂的滤后水为研究对象,采用二氧化氯、氯胺顺序投加联合消毒工艺对其进行消毒处理。运用化学分析和生物学试验的方法,考察了经不同投量的组合消毒后消毒剂残余量的变化,以及联合工艺的消毒效果和持续消毒能力。试验结果表明,经不同投量组合的二氧化氯、氯胺顺序投加联合消毒后,出水中的细菌总数及总大肠菌群均达到《生活饮用水卫生标准》的要求。氯胺投量对总余氯和二氧化氯残余量的影响显著,而二氧化氯的投加量对其残余量的影响不大。二氧化氯、氯胺顺序投加联合消毒工艺在低投量组合下就能达到良好的消毒效果,且持续消毒能力强。