Kraft Effluent Research Articles

Bioaugmentation with Advenella kashmirensis for the treatment of a kraft pulp effluent by aerated lagoon

Brazil is considered a world leader in paper production. It is estimated that the sector contributes 46.5% of the national gross domestic product, and its effluents have high concentrations of organic matter and recalcitrant compounds which can cause coloration and ecotoxicity, generating impact if not properly treated. A potential strategy for the treatment of this wastewater is bioaugmentation with native bacteria isolated from the industrial sludge and effluent, which, due to their potential metabolism adapted to adverse environmental conditions, may favor the removal of specific compounds. When associated with immobilization techniques, the inoculum can develop as a biofilm adhered to a support medium, which provides surfaces for adhesion, growth and survival of bacteria. We therefore investigated the treatment of Kraft pulp effluent by bioaugmentation with the autochthonous bacterium Advenella kashmirensis both immobilized in a spongy support medium - Aqua Porous Gel (APG) - and in free-swimming (planktonic) form, denominated Phase I and II, respectively. The investigation was performed in a bench-scale aerated lagoon system with untreated industrial effluent. The effect of the use of bacteria in bioaugmentation was assessed by the removal parameters of Chemical Oxygen Demand (COD), Biochemical Oxygen Demand (BOD5), Color, Total Phenolic Compounds (TPC) and Lignin Compounds (LC). The results indicate that both Phases I and II were efficient for the treatment of COD, BOD5 and color parameters. However, the biofilm form provided better stability to the biological system in the treatment of the Kraft pulp effluent.
 Keywords: adhered, kraft effluent, SEM, suspended solids.

Bacterial diversity in aerated facultative lagoon treating kraft cellulose effluent with bioaugmentation

The microbiological diversity was evaluated in an aerated facultative lagoon system with organic loading rates of 0.2 and 0.6 kgCODm-3d-1 treating effluent from the kraft pulp industry for bioaugmentation purposes. Samples were taken from a laboratory-scale lagoon at steady state treating kraft pulp effluent and operated with two different rates for 120 days. The analysis was performed by 16S rDNA sequencing. The autochthonous bacteria were identified through statistical similarity obtained from the NCBI-BLAST database. The lagoon performance was assessed based on the removal efficiency of biochemical oxygen demand (94% and 80%), chemical oxygen demand (51% and 44%), total organic carbon (49% and 41%), lignin-derived compounds (13% and 27%), turbidity (94% and 87%), for the low and high rates used respectively. Color and TPC were not significantly removed during the biological treatment of the industrial matrix. In the biomass samples collected at a steady state, 9 and 12 species of bacteria were identified at the applied rates. The species Bacillus cereus, Bacillus thuringiensis, and Paenibacillus glucanolyticus found in this matrix presented significant removal of the parameters in the kraft effluent. The three referred species show great promise in the removal of specific parameters in an AFL biological treatment system using bioaugmentation.

Trametes versicolour laccase immobilization by covalent binding and its application in Kraft E1 effluent pre-treated with ozone

Wastewater deriving from cellulose and paper manufacturing is one of the most important industrial effluents due to its large-volume production and high pollution load. Effluent deriving from the pulp bleaching stage (Kraft E1 effluent) remains one of the major issues faced by paper mills among all wastewaters generated in each stage of paper-making processes. Kraft E1 effluent was submitted to a sequential chemical (ozonization) – biological (immobilized laccase) treatment. Laccase was obtained from Trametes versicolour in liquid medium of culture using 2,5 -xylidine as inducer. Crude laccase extract was immobilized through covalent binding in Montmorillonite KSF and Eupergit®C supports based on different protocols. Eupergit®C has shown the best protein immobilization (51%), retention activity (100%), and operational stability (ten oxidative cycles) results. Enzymatic treatments using free and immobilized laccase onto Eupergit®C were applied to Kraft E1 effluent. After 18-h treatment, total phenol removal reached 20% and 40% in free and immobilized laccase, respectively. Ozone combined to enzymatic processes using reactor assembled with immobilized laccase (31 U g−1, total mass = 10.0 g) had effect on decolonization efficiency and on total phenols’ removal from Kraft effluent. Ozone treatment was capable of removing 52% of total phenols and 76% of colour from the investigated effluent. Sequential enzymatic treatment has increased total phenols’ removal to 64% within 30-minute treatment and reached 70% removal within 60 minutes. The herein observed additional phenol removal based on enzymatic treatment is an important outcome if one takes into consideration the fraction of total phenols that could not be removed by the ozone process.

Microbiological diversity in an aerated lagoon treating kraft effluent

The microbiological diversity of cultivable bacteria was analyzed in an aerated facultative lagoon. The removal of specific compounds and measures of pollutant load was evaluated with isolated native bacteria, selected and identified in kraft cellulose effluent. The system was operated with an organic loading rate of 0.2 kgCODm-3d-1 for 60 days. Analyses of the fluorescence excitation-emission matrix, acute ecotoxicity, and microbiology were performed. Bioaugmentation tests were done to emphasize the removal of color, using promising species. The removals of biochemical oxygen demand, chemical oxygen demand, and total organic carbon in AFL were 94%, 51%, and 41%, respectively. Regarding color, removal was up to 4%, and the total phenolic compounds were not removed through biological treatment. The treatment also decreased turbidity by 94% and lignin derivatives by 12%. The bacteria identified through NCBI-BLAST and statistical similarity totaled 9 species in the cellulose effluent, three of which have the potential for color treatment: Bacillus cereus, Bacillus thuringiensis, and Paenibacillus sp. The Bacillus cereus combined with biomass removed color (69%), total phenolic compounds (37%), and compounds derived from lignin (53%). These species are promising for removing specific parameters combined with biomass from biological AFL treatment systems.

Tratamento de efluente kraft por sistema de lodos ativados com adição de carvão ativado como meio suporte

Os efluentes industriais de celulose apresentam uma complexa composição desubstâncias, com elevada carga orgânica e compostos recalcitrantes que dificultamo tratamento em sistemas biológicos comumente aplicados, como lodos ativados.Assim, faz-se necessária a realização de estudos para a melhoria desses tratamentos.Nessa perspectiva, este trabalho teve como objetivo avaliar um sistema delodos ativados com adição de meio suporte de carvão ativado em pó (CAP) parao tratamento de efluente Kraft. Para isso, um reator foi operado por 110 dias,separado em quatro etapas. A primeira apenas de lodos ativados e as outras comconcentrações de CAP de 2,4 e 6 g L-1 (etapas II, III e IV, respectivamente). A remoçãoda matéria orgânica foi maior nas etapas com meio suporte, obtendo médias de55,94 e 58% para demanda química de oxigênio, demanda bioquímica de oxigênioe carbono orgânico total, respectivamente. Parâmetros específicos, como cor,derivados de lignina e compostos aromáticos, foram removidos em 28, 29 e 36% emmédia, respectivamente, nas etapas com o CAP. Observou-se a formação de biofilmena superfície do meio suporte durante o tratamento, com maior concentração debiomassa na etapa IV, alcançando 4.086 mg L-1 de sólidos suspensos voláteis. Nogeral, a adição do CAP como meio suporte no sistema de lodos ativados melhorou aeficiência de tratamento, entretanto o aumento da concentração de CAP no reatornão apresentou melhorias significativas, o que indica a quantidade de 2 g L-1 de CAPcomo a melhor concentração aplicada no sistema de lodos ativados.

Expression profiling and gene ontology analysis in fathead minnow (Pimephales promelas) liver following exposure to pulp and paper mill effluents

Many studies link pulp and paper mill effluent (PPME) exposure to adverse effects in fish populations present in the mill receiving environments. These impacts are often characteristic of endocrine disruption and may include impaired reproduction, development and survival. While these physiological endpoints are well-characterized, the molecular mechanisms causing them are not yet understood. To investigate changes in gene transcription induced by exposure to a PPME at several stages of treatment, male and female fathead minnows (FHMs) were exposed for 6days to 25% (v/v) secondary (biologically) treated kraft effluent (TK) or 100% (v/v) combined mill outfall (CMO) from a mill producing both kraft pulp and newsprint. The gene expression changes in the livers of these fish were analyzed using a 22K oligonucleotide microarray. Exposure to TK or CMO resulted in significant changes in the expression levels of 105 and 238 targets in male FHMs and 296 and 133 targets in females, respectively. Targets were then functionally analyzed using gene ontology tools to identify the biological processes in fish hepatocytes that were affected by exposure to PPME after its secondary treatment. Proteolysis was affected in female FHMs exposed to both TK and CMO. In male FHMs, no processes were affected by TK exposure, while sterol, isoprenoid, steroid and cholesterol biosynthesis and electron transport were up-regulated by CMO exposure. The results presented in this study indicate that short-term exposure to PPMEs affects the expression of reproduction-related genes in the livers of both male and female FHMs, and that secondary treatment of PPMEs may not neutralize all of their metabolic effects in fish. Gene ontology analysis of microarray data may enable identification of biological processes altered by toxicant exposure and thus provide an additional tool for monitoring the impact of PPMEs on fish populations.

Diagnosis of dissolved organic matter removal by GAC treatment in biologically treated papermill effluents using advanced organic characterisation techniques

Granular activated carbon (GAC) exhaustion rates on pulp and paper effluent from South East Australia were found to be a factor of three higher (3.62cf. 1.47kgm−3) on Kraft mills compared to mills using Thermomechanical pulping supplemented by Recycled Fibre (TMP/RCF). Biological waste treatment at both mills resulted in a final effluent COD of 240mgL−1. The dissolved organic carbon (DOC) was only 1.2 times higher in the Kraft effluent (70 vs. 58mgL−1), however, GAC treatment of Kraft and TMP/RCF effluent was largely different on the DOC persisted after biological treatment. The molecular mass (636 vs. 534gmol−1) and aromaticity (5.35 vs. 4.67Lmg−1m−1) of humic substances (HS) were slightly higher in the Kraft effluent. The HS aromaticity was decreased by a factor of 1.0Lmg−1m−1 in both Kraft and TMP/RCF effluent. The molecular mass of the Kraft effluent increased by 50gmol−1 while the molecular mass of the TMP/RCF effluent was essentially unchanged after GAC treatment; the DOC removal efficiency of the GAC on Kraft effluent was biased towards the low molecular weight humic compounds. The rapid adsorption of this fraction, coupled with the slightly higher aromaticity of the humic components resulted in early breakthrough on the Kraft effluent. Fluorescence excitation–emission matrix analysis of the each GAC treated effluent indicated that the refractory components were higher molecular weight humics on the Kraft effluent and protein-like compounds on the TMP/RCF effluent. Although the GAC exhaustion rates are too high for an effective DOC removal option for biologically treated pulp and paper mill effluents, the study indicates that advanced organic characterisation techniques can be used to diagnose GAC performance on complex effluents with comparable bulk DOC and COD loads.

Pulp and paper mill effluents induce distinct gene expression changes linked to androgenic and estrogenic responses in the fathead minnow (Pimephales promelas)

Although effluent treatment systems within pulp and paper mills remove many toxicants and improve wastewater quality, there is a need to understand and quantify the effectiveness of the treatment process. At a combined news and kraft pulp and paper mill in northwestern Ontario, Canada, fathead minnow (FHM) reproduction and physiology were examined before, during, and after a short-term (6-d) exposure to 10% (v/v) untreated kraft mill effluent (UTK), 25% (v/v) secondary treated kraft mill effluent (TK), and 100% (v/v) combined mill outfall (CMO). Although UTK exposure significantly decreased egg production, neither TK nor CMO caused any reproductive changes. The expression of six genes responsive to endocrine-disrupting compounds, stress, or metals was then examined in livers of these fish using real-time polymerase chain reaction. In female FHMs, none of the three effluents induced significant expression changes in any genes investigated. By contrast, in males there were significant increases in the mRNA levels of androgen receptor, estrogen receptor (ER) beta, and cytochrome P4501A (CYP1A) upon UTK and TK exposure but no changes in ERalpha or vitellogenin (VTG) gene expression, whereas CMO exposure significantly increased the mRNA levels of ERalpha, VTG, and CYP1A. Together, these results suggest that kraft effluent before and after biological treatment contained compounds able to induce androgenic effects in FHMs, and that combination of kraft and newsmill effluents eliminated the androgenic compounds while inducing distinct and significant patterns of gene expression changes that were likely due to estrogenic compounds produced by the newsmill.

Characterization of E1 Kraft Mill Effluent by Toxicity Identification Evaluation Methodology

In order to recover and reuse water in the Kraft mill process, evaluation of separate streams is required to identify toxic compounds or microcontaminants. The stage E1 Kraft effluent, corresponding to the first extraction step of the bleaching Kraft mill process, provides the main toxic compounds found in the final process effluent. This paper uses the toxicity identification evaluation (TIE) procedure for the physicochemical and ecotoxicological characterization of the E1 Kraft effluent. To distinguish the most important toxic compounds, a physicochemical characterization and Phase I of the TIE procedure were performed. The acute toxic effect of the E1 Kraft effluent and treated fraction was performed on Daphnia magna. Results show that untreated E1 Kraft effluent exerts an acute toxic effect on D. magna (24 h LC50 = 27.6%), where the E1 Kraft effluent is characterized by pH 10.5, chemical organic demand (COD) 1,348.8 mg/l, and biological organic demand (BOD5) 397.5 mg/l, while total phenolic compounds and color are 853.7 mg/l and 0.204 1 × 1 cm, respectively. Additionally, Cu+2 (0.51 mg/l) and Fe+2 (0.64 mg/l) were detected. With respect to different treatments, our results indicate that activated carbon, anionic and cationic exchange treatments were able to reduce more that 45% of E1 Kraft effluent’s acute toxicity and that the ethylenediaminetetraacetic acid treatment was able to reduce the E1 Kraft effluent’s acute toxicity to around 75% and the Cu+2 concentration to 0.019 mg/l. Moreover, specific analysis of heavy metals and organic compounds by GC-MS show that the main compound responsible for the toxicity was Cu+2, whose tolerance level on D. magna of the 0.12 mg/l.

Remediation of Kraft Effluent by Ozonation: Effect of Applied Ozone Concentration and Initial pH

ABSTRACT In this study, the impact of ozone concentration (14 and 7mg/L−1 applied for 120min) and pH (10 and 12) on color removal, and reduction of dissolved organic matter (DOC) and total phenol of Kraft E1 effluent was investigated. The degradation kinetics for the all parameters at pH 12 were slower than of those at pH 10. The degradation at pH 10 ceased after approximately 120min, while for the ozonation at pH 12, ozone was still being consumed even after 5h of treatment. When the ozone dose was increased, the removal efficiency increased; however, the DOC removal efficiency continued limited.

Exposure of Reproductively Maturing Rainbow Trout to a New Zealand Pulp and Paper Mill Effluent

Long-term studies on the reproductive fitness of fish under controlled exposure conditions are necessary to address some of the controversy surrounding the field-based studies of pulp and paper effluent effects. This study undertook effluent exposures of 2+ age rainbow trout that were approximately halfway through gonadal growth. Trout were exposed to a mixed thermomechanical/bleached kraft effluent in 12,000-L flow-through exposure tanks at an environmental research facility located at a pulp and paper mill in Kawerau, New Zealand. Trout were exposed to either upstream river water or 10% effluent in upstream river water and were maintained at a ration of 0.7% of body wet weight during the experiment. Results of the 2-month study indicated that trout survival was not significantly different between effluent-exposed tanks and reference tanks. There was extensive growth during the exposure but no differences were found due to effluent exposure. Gonadal development was not significantly different between treatments. Steroid hormone concentrations in males and females were not affected by effluent exposure. The effluent showed no potential to be estrogenic as indicated by a lack of vitellogenin induction in male trout. Other physiological indicators of energy storage and utilization also showed no significant differences. Modest induction of hepatic 7-ethoxyresorufin-O-deethylase (2.5-fold) was the only detectable biological effect of the exposure. Biliary concentration of effluent-related compounds were typical of pulp mill effluent exposure and further suggested that the source of phytosterols was in fact dietary and not effluent-derived.

Monitoring of Activated Sludge Systems Using a Combination of Specific Oxygen Uptake Rates and Specific Adenosine Triphosphate Measurements

Abstract Two five-litre activated sludge (AS) bioreactors were operated for several months to demonstrate potential mill applications of a four-assay set, which has been proposed as a tool for monitoring the health of the AS microbial population. The set consists of three specific oxygen uptake rate (SOUR) determinations at different substrate concentrations (SOURat, SOURnmax and SOURtox where at, nmax and tox are defined as aeration tank, near maximum, and toxic, respectively), and a specific adenosine triphosphate (SATP) assay. Two disturbances were applied at different times to an AS system treating kraft effluent. First, temperature was increased from 25 to 40°C, and second, a black liquor spill was simulated. The data before, during, and after these disturbances were statistically analyzed. From this analysis, we concluded that the four-assay set could be used as a microbial health characterization (MHC) tool. It allows an operator to correlate microbial changes with operating data over a mediumterm time scale. We compared the values obtained during periods of upset in the system treating the kraft effluent, to the baseline data set determined from stable operation periods. This demonstrated how the four-assay set could be used as a biological early warning (BEW) tool. It allows a treatment system operator to make appropriate adjustments immediately after detecting values that fall outside the baseline data range.

Semiconductor-assisted photodegradation of lignin, dye, and kraft effluent by Ag-doped ZnO

This work reports a preliminary study of semiconductor-assisted photochemical degradation of lignin, Remazol Brilliant Blue R and Kraft E1 paper effluent by using ZnO and Ag-doped ZnO photocatalysts. The doped semiconductor was prepared in the reaction media by photoreduction of silver nitrate. With the use of 100 mg of ZnO and 15 mg of Ag–ZnO, almost total decolorization of the dye and lignin samples in reaction times lower than 60 min were observed. Extending the photochemical reaction up to 120 min, the total organic carbon content (TOC) was reduced in 90%. For the paper effluent, a fast decolorization was obtained for relatively short reaction times. However, de TOC reduction was negligible (near of 10%) up to high reaction times (300 min). By using the Ag–ZnO photocatalyst, the toxicity of lignin and Kraft E1 effluent toward E. Coli was completely removed. For the dye, the formation of transient toxic species was observed.

Molecular weight distribution of chlorolignin in bleached Kraft effluent by GPC and ultrafiltration

The molecular weight distribution (MWD) of chlorinated compounds of bleached Kraft pulp mill effluent was investigated by aqueous gel permeation chromatography (GPC) and ultrafiltration. The effluent was fractionated by ultrafiltration, using different cut-off membranes (MW 50 000, 20 000, 10 000 and 8000). The retentate and permeate of each ultrafiltration was analyzed by GPC. The results showed that the molecular weight distribution for all samples ranged from 200 to 550 Da. Two effects were discussed: associative interactions between the compounds to form high molecular associated complexes (aggregates); and non-size-exclusion effects, like ion exclusion. Aggregates formation was confirmed by ultrafiltration experiments, using a 50 000 cut-off membrane.

Hydroxamate Iron Complex with Phenoloxidase Activity Acting on Lignin and Chlorolignins

The properties of a siderophore model, acetohydroxamic acid (AHA), of desferral were studied. The pH, ionic strength, and AHA/Fe(III) ratios foro-dianisidine oxidation were optimized. Phenoloxidase activity of hydroxamates/Fe(III) acting ono-dianisidine at pH 7.0 and pH 3.0 was observed. Under these conditions, AHA was able to reduce Fe(III) to Fe(II) followed by ferrozine complexation. AHA/Fe(III) complex degraded lignin and chlorolignins from kraft effluent E1 65% and 85%, respectively, after 24 h.

Biomass photochemistry-XXII: Combined photochemical and biological process for treatment of Kraft El effluent

The photocatalytic conditions for decontamination of Kraft effluents from Eucalyptus grandis (Brazil) and Pinus radiata (Chile) were studied. Irradiation in the presence of ZnO was similar for E. grandis and P. radiata effluents reaching a total decolorization after 2 h. This correlates with the mineralization process. When ZnO was immobilized on sand a two-fold faster decolorization was observed after 30 min of irradiation. The combined photochemical-biobleaching process was effective in the decolorization of Eucalyptus Kraft El effluent. By applying a short time of irradiation (10 min) the time necessary for 50% of biological colour reduction was decreased to half. The contribution of the photochemical process when applied as a post-treatment was least evident. In this case additional reduction of about 10% on the AOX content and almost completion of the decolorization process was observed for Pinus Kraft El effluent. Photochemistry applied to pulp and paper industry appeared as an important technique to remediate pollution problems.

Sensory evaluation of fish exposed to pulp and paper mill effluent: a case study of methods used for environmental effects monitoring

The federal Environmental Effects Monitoring (EEM) program, a requirement of the Fisheries Act Pulp and Paper Effluent Regulations, requires sensory evaluation at Canadian pulp and paper mills where there have been historical complaints of fish tainting or reduced fishing efforts and there is no potential health hazard. Sensory evaluation tests were conducted at three mills in British Columbia. Each test component yielded considerable variability. Nevertheless, there were similarities in the results as defined by difference test methods, while the results of preference and acceptance test were less clear. Tainting, or taste impairment, occurred at one of three mills. Significant tainting of two fish species occurred within three hours and at exposure concentrations less than 0.08% (v/v) unbleached kraft effluent. Adult and juvenile fish appear to be attracted to and reside in effluent plumes immediately downstream of the outfall at some mills. Sensory evaluation may be the most sensitive monitoring tool available to assess and integrate effluent exposure with the usability of valuable sports, recreation, commercial and native fisheries resources. A proposal to focus EEM cycle 2 programs to evaluate the use of these fisheries resources is presented.

Resin acid degradation by bacterial strains grown on CTMP effluent

All resin acids are diterpenoid carboxylic acids that are components of softwood extractives and they are known to contribute to much of the toxicity of pulp mill effluents. Although biological treatment systems can efficiently remove resin acids during normal operating conditions, resin acid breakthroughs occasionally occur. Recently we isolated five bacterial strains from bleach kraft effluents that degrade dehydroabietic acid (DHA), a resin acid commonly found in effluents. In this study we examined the ability of two bacterial strains (BKME 5 and BKME 9) to grow on chemithermomechanical pulping (CTMP) effluent and degrade DHA. Both of the strains could grow on CTMP effluents, but did not degrade DHA. COD measurement showed that both strains used other organic substrates in CTMP effluent. When nutrients (NH4⊕, PO43−, minerals and vitamins) were added to the effluent, both growth and DHA degradation increased significantly. The strains used DHA and other organic sources in the CTMP effluent simultaneously. The stimulated growth resulting from use of other organic material did not increase the rate of DHA degradation. It was found that ammonium played an important role in the DHA degradation of both strains. Without added ammonium, DHA degradation did not occur. Other nutrients also played important roles in DHA degradation by BKME 9.

Effect of H2O2 and DTPA on the characteristics and treatment of TCF (totally chlorine-free) and ECF (elementally chlorine-free) kraft pulping effluents

Perceived negative environmental effects associated with chlorine bleaching have led to the development and implementation of pulp bleaching technologies which eliminate the use of elemental chlorine (ECF) or any chlorine containing compounds (TCF). Commercial implementation of these technologies has moved forward; however, the research necessary to fully understand the impact of effluents from these new bleaching technologies on the environment and on existing biological treatment processes has lagged behind, and is for many novel bleaching sequences, non-existent. This study examined the impact of hydrogen peroxide (H2O2) and chelating agents on the characteristics and treatment of TCF and ECF kraft effluents. Effluent BOD was reduced approximately 25% by addition of H2O2 concentrations from 20-640 mg/L, however, effluent toxicity was not affected by hydrogen peroxide concentrations of up to 640 mg/L. Unacclimated activated sludge was inhibited by sudden exposure to shock doses of hydrogen peroxide. While the viability of the sludge (as measured by the rate of substrate metabolism) was profoundly affected, the effect was reversible, with full recovery of metabolic activity restored within approximately 10 hours of the shock. In continuous trials, as the activated sludge reactor became acclimated to H2O2, the kinetics of degradation of hydrogen peroxide increased. Chelating agents, particularly diethylene triamine pentaacetic acid (DTPA), were also found to have a dramatic impact on sludge viability and reactor performance. Batch tests indicated a DTPA dose-dependent decrease in oxygen uptake rate. Introduction of DTPA at levels commonly found in TCF effluents to continuous reactors resulted in a disruption of floc structure and a 39% decrease in BOD removal efficiency. Removal of acute toxicity as measured by Microtox was maintained despite the poor BOD removal efficiency.

Resin acid degradation by bacterial strains grown on CTMP effluent

All resin acids are diterpenoid carboxylic acids that are components of softwood extractives and they are known to contribute to much of the toxicity of pulp mill effluents. Although biological treatment systems can efficiently remove resin acids during normal operating conditions, resin acid breakthroughs occasionally occur. Recently we isolated five bacterial strains from bleach kraft effluents that degrade dehydroabietic acid (DHA), a resin acid commonly found in effluents. In this study we examined the ability of two bacterial strains (BKME 5 and BKME 9) to grow on chemithermomechanical pulping (CTMP) effluent and degrade DHA. Both of the strains could grow on CTMP effluents, but did not degrade DHA. COD measurement showed that both strains used other organic substrates in CTMP effluent. When nutrients (NH4+, PO43− minerals and vitamins) were added to the effluent, both growth and DHA degradation increased significantly. The strains used DHA and other organic sources in the -CTMP effluent simultaneously. The stimulated growth resulting from use of other organic material did not increase the rate of DHA degradation. It was found that ammonium played an important role in the DHA degradation of both strains. Without added ammonium, DHA degradation did not occur. Other nutrients also played important roles in DHA degradation by BKME 9.