Pulp Mill Effluent Research Articles

The Fenton oxidation of biologically treated paper and pulp mill effluents: A performance and kinetic study

Abstract The Fenton oxidation (Fe2+/H2O2) of bio-recalcitrant organics, which are present in biologically treated paper and pulp mill effluents (BTME), were investigated in this study. This study primarily focused on the performance and kinetics involved in the Fenton oxidation of BTMEs. A biologically treated recycle mill effluent (RME) and a neutral sulfite semi-chemical (NSSC) mill effluent were used for the experiments. The impact of FeSO4·7H2O and H2O2 dosages on chemical oxygen demand removal (COD) was evaluated. The Fenton oxidation experiments were carried out at 25 °C and a pH value of 3.8. The initial COD of the biologically treated NSSC and RME effluents were 3756 mg/L and 436 mg/L, respectively. The maximum COD removal was found at a Fe2+/H2O2 ratio of 2.22 and 0.32 for the RME and NSSC effluents, respectively. The optimal COD/H2O2 for the RME and NSSC effluents was found to be 0.96 and 1.19 respectively. After a 60 min reaction, the maximum COD removal efficiency for the NSSC and RME effluents were found to be 44% and 63%, respectively. The maximum reaction rates obtained for the RME and NSSC effluents were 18 mg COD L−1 min−1 and 48 mg COD L−1 min−1, respectively. The experimental results demonstrated that bio-recalcitrant organics, such as phenols and lignin, were readily degraded into organic acids. The applicability of the first order, second order, Behnajady–Modirshahla–Ghanbery (BMG) and a newly developed two staged first-order (TSF) kinetic model were evaluated. Both the BMG and TSF models yielded high correlation coefficients (r2). For extended reaction times, it was found that the TSF model best described the COD removal. In addition, the TSF kinetic constants (k12, k13) revealed that a rapid initial degradation reaction is followed by a slower secondary degradation reaction. This performance and kinetic study demonstrated that the conventional Fenton process can effectively remove bio-recalcitrant organics that are found in BTMEs.

Exploring the diverse potentials of Planococcus sp. TRC1 for the deconstruction of recalcitrant kraft lignin

Kraft lignin (KL) is the chief contaminant which is responsible for dark coloration, toxicity and high chemical oxygen demand (COD) of paper pulp mill effluent. The present study investigated the diverse potentials of Planococcus sp. TRC1 in the biodegradation of KL. Preliminary evaluation indicated that the strain was able to grow on broad spectrum of lignin-derived compounds, decolorize lignin-mimicking dyes and catabolize substrates of ligninolytic enzymes. Response surface methodology (RSM) was executed to perform the optimization of different process parameters. The results displayed that Planococcus sp. TRC1 could completely utilize 100 mg L−1 of KL and 78% of 200 mg L−1 of KL as sole source of carbon with concurrent reduction in COD and color. The biokinetic details of KL biodegradation showed that the values of $$\mu^{*}$$ , µ max, $$q^{*}$$ and q max were 0.018 h−1, 0.01 h−1, 0.023 g g−1 h−1 and 0.05 g g−1 h−1, respectively. UV–visible spectrophotometry, SEM and FTIR indicated the significant alterations in the surface morphology, functional groups and chromophores during the course of biodegradation. XRD revealed the emergence of peak signifying the formation of low molecular weight intermediates after bacterial treatment. Considering the environmental impact, bacterial-treated KL illustrated less phytotoxicity using Vigna radiata seed bioassay. These results suggested that Planococcus sp. TRC1 could be a promising strain for the degradation of KL in an ecofriendly way.

Evaluating the potential of effluent extracts from pulp and paper mills in Canada, Brazil, and New Zealand to affect fish reproduction: Estrogenic effects in fish.

The authors examined the potential of pulp mill effluent from pulp-producing countries (Canada, Brazil, New Zealand) to affect fish reproduction. Specifically, the estrogenic effects in juvenile rainbow trout (Oncorhynchus mykiss) pulse-exposed to 11 different mill effluent extracts (intraperitoneal injections of solid-phase extraction-dichloromethane nonpolar fraction). The results indicated that effluent extracts were estrogenic in juvenile trout irrespective of the gender, as reflected by increasing level of plasma vitellogenin (VTG; Brazil > New Zealand > Canada). Despite the high variability observed among mills, differences in VTG levels were related to the type of mill process (kraft > elementary chlorine-free kraft > thermomechanical pulping). Moreover, effluent treatments did not appear to significantly decrease VTG induction. A consistent estrogenic effect was observed in those mills that process a combination of feedstocks (softwood and hardwood), with the highest increase in VTG related to eucalyptus feedstock. The results demonstrate significant estrogenic effects of pulp mill effluents on chronically exposed juvenile trout, suggesting that in vivo metabolic activation of precursors is necessary to cause the observed increases in VTG levels. This molecular estrogenic response provides a useful starting point for predicting population-level impacts through the adverse outcome pathway methodology. Environ Toxicol Chem 2017;36:1547-1555. © 2016 SETAC.

Photocatalytic degradation of industrial pulp and paper mill effluent using synthesized magnetic Fe2O3-TiO2: Treatment efficiency and characterizations of reused photocatalyst

In this work, heterogeneous photocatalysis was used to treat pulp and paper mill effluent (PPME). Magnetically retrievable Fe2O3-TiO2 was fabricated by employing a solvent-free mechanochemical process under ambient conditions. Findings elucidated the successful incorporation of Fe2O3 into the TiO2 lattice. Fe2O3-TiO2 was found to be an irregular and slightly agglomerated surface morphology. In comparison to commercial P25, Fe2O3-TiO2 exhibited higher ferromagnetism and better catalyst properties with improvements in surface area (58.40 m2/g), pore volume (0.29 cm3/g), pore size (18.52 nm), and band gap (2.95 eV). Besides, reusability study revealed that Fe2O3-TiO2 was chemically stable and could be reused successively (five cycles) without significant changes in its photoactivity and intrinsic properties. Additionally, this study demonstrated the potential recovery of Fe2O3-TiO2 from an aqueous suspension by using an applied magnetic field or sedimentation. Interactive effects of photocatalytic conditions (initial effluent pH, Fe2O3-TiO2 dosage, and air flow-rate), reaction mechanism, and the presence of chemical oxidants (H2O2, BrO3−, and HOCl) during the treatment process of PPME were also investigated. Under optimal conditions (initial effluent pH = 3.88, [Fe2O3-TiO2] = 1.3 g/L, and air flow-rate = 2.28 L/min), the treatment efficiency of Fe2O3-TiO2 was 98.5% higher than the P25. Based on Langmuir-Hinshelwood kinetic model, apparent rate constants of Fe2O3-TiO2 and P25 were 9.2 × 10−3 and 2.7 × 10−3 min−1, respectively. The present study revealed not only the potential of using magnetic Fe2O3-TiO2 in PPME treatment but also demonstrated high reusability and easy separation of Fe2O3-TiO2 from the wastewater.

Physiological Regulation of an Alkaline-Resistant Laccase Produced by Perenniporia tephropora and Efficiency in Biotreatment of Pulp Mill Effluent

Regulation of alkaline-resistant laccase from Perenniporia tephropora KU-Alk4 was proved to be controlled by several factors. One important factor was the initial pH, which drove the fungus to produce different kinds of ligninolytic enzymes. P. tephropora KU-Alk4 could grow at pH 4.5, 7.0, and 8.0. The fungus produced laccase and MnP at pH 7.0, but only laccase at pH 8.0. The specific activity of laccase in the pH 8.0 culture was higher than that in the pH 7.0 culture. At pH 8.0, glucose was the best carbon source for laccase production but growth was better with lactose. Low concentrations of glucose at 0.1% to 1.0% enhanced laccase production, while concentrations over 1% gave contradictory results. Veratryl alcohol induced the production of laccase. A trace concentration of copper ions was required for laccase production. Biomass increased with an increasing rate of aeration of shaking flasks from 100 to 140 rpm; however, shaking at over 120 rpm decreased laccase quantity. Highest amount of laccase produced by KU-Alk4, 360 U/mL, was at pH 8.0 with 1% glucose and 0.2 mM copper sulfate, unshaken for the first 3 days, followed by addition of 0.85 mM veratryl alcohol and shaking at 120 rpm. The crude enzyme was significantly stable in alkaline pH 8.0~10.0 for 24 hr. After treating the pulp mill effluent with the KU-Alk4 system for 3 days, pH decreased from 9.6 to 6.8, with reduction of color and chemical oxygen demand at 83.2% and 81%, respectively. Laccase was detectable during the biotreatment process.

Genotoxicity assessment of pulp and paper mill effluent before and after bacterial degradation using Allium cepa test

A lignin peroxidases-producing Serratia liquefaciens was used for bioremediation of pulp and paper (P&P) mill effluent. The treatment led to reduction of chemical oxygen demand (COD), colour, lignin and phenolic content by 84%, 72%, 61% and 95%, respectively. The effluent detoxification was studied by genotoxicity assays using Allium cepa L. (onion) root tip cells. Genotoxicity studies included measuring mitotic index (MI), chromosomal aberrations (CA) and nuclear abnormalities (NA) in root tip cells following treatment with 25, 50, 75 and 100% (v/v) of effluent. The root tip cells grown in untreated effluent showed a significant decrease in MI from 69% (control) to 32%, 27%, 22% and 11% at 25%, 50%, 75% and 100% effluent concentration, respectively. This indicated that the untreated effluent was highly cytotoxic in nature. Further, root tip cells, when treated with different concentrations of effluent showed various CA and NA including c-mitosis, stickiness, chromosome loss, chromosome break, anaphase bridge, multipolar anaphase, vagrant chromosomes, micronucleated and binucleated cells. The MI observed in root tip cells grown in bacterial treated effluents at similar concentrations (25, 50, 75 and 100% v/v) showed an increase of 33%, 36%, 42% and 66%. CA showed a substantial decrease and in some instances, complete absence of CA was also observed. The findings suggest that S. liquefaciens culture could be a potential bacterial culture for bioremediation of P&P mill effluent, as it is effective in substantial lowering of pollutants load as well as reduces the cytotoxic and genotoxic effects of effluent.

Improving photofermentative biohydrogen production by using intermittent ultrasonication and combined industrial effluents from palm oil, pulp and paper mills

An ultrasonication technique was applied intermittently onto photofermentation broth during the first six hours of photofermentation to improve biohydrogen production by using Rhodobacter sphaeroides NCIMB8253. In this research, photofermentation broth consisted of a combination of palm oil (25%, v/v), pulp and paper (75%, v/v) mill effluents as well as liquid inoculum. The effects of amplitude (10, 20 and 30%, A) and ultrasonication duration (5, 10 and 15min, T) were investigated in terms of their influences on photofermentative biohydrogen yield and total chemical oxygen demand (CODtotal) removal. The recommended ultrasonication parameters were found at the middle range of amplitude and duration (A20T10). Using A20T10 intermittent treatment, the production of biohydrogen could be maximized up to 14.438mL H2/mLmedium with a CODtotal removal and light efficiency of 52.2% and 7.412%, respectively. By comparing the treatment without intermittent ultrasonication, an increase of biohydrogen yield by 44.6% was achieved in A20T10 treatment. A total energy input of 306.1J/mL (A20T10 treatment) was supplied to improve substrate consumption and light distribution during the photofermentation, which led to the increase of biohydrogen yield.

Phytoextraction potential of heavy metals by native wetland plants growing on chlorolignin containing sludge of pulp and paper industry

The results of physico-chemical analysis of pulp and paper mill effluent sedimented sludge revealed the presence of heavy metals (mgl−1) Fe (67.53), Zn (13.90), Cu (2.15), Cr (2.30), Cd (0.255), Mn (11.0), Ni (3.30), and Pb (1.05) along with persistent chlorolignin. The major persistent organic pollutants detected by GC–MS were ethane, 1,1-diethoxy; tetradecanoic acid; furane 2,5-dimethyl; n-hexadecanoic acid; nonacosane, trimethylenebis-1,3-dioxolane; 1,3-dioxolane, 2-(phynylmethyl). Twelve representative native plants were noted based on their population number growing on pulp and paper sludge and evaluated for their phytoextraction potential of heavy metals. The result revealed that Triticum aestivum was found as root accumulator for all metals except Cu. Similarly, the Brassica campestris accumulated all metals maximum in root except Ni, Fe and Pb. While, Eclipta alba accumulated majority of metals in their shoot and leaves, But Solanum nigrum, Rumex dentatus accumulated metals in root and shoot both. Rananculus scleratus accumulated all the tested metals in their aerial parts except Cd and Pb. Cammelina benghalensis accumulated metals in root except Cd, Pd. Similarly the Phragmites cummunis and Ricinus cummunis accumulated majority of metals in their shoot and leaves. It was also noted that several evaluated plant showed bioconcentration factor (BCF) greater than one for accumulated metals i.e. Pb in T. aestivum (1.285), C. benghalensis (5.142), Cannabis sativa (3.466), P. cummunis (7.180), R. cummunis (66.80) was also noted. Furthermore, greater than one translocation factor (TF) for all these plants showed strong evidence for phytoextraction and in situ remediation potential of these plants. The overall order of phytoextraction potential of native wetland plants were C. sativa>P. cummunis>C. benghalensis>T. aestivum>B. campestris>E. alba.

Using one-step facile and solvent-free mechanochemical process to synthesize photoactive Fe2O3-TiO2 for treating industrial wastewater

In this present study, Fe2O3-TiO2 photocatalyst was synthesized and used to degrade real industrial wastewater, namely pulp and paper mill effluent (PPME). Fe2O3-TiO2 was synthesized via ball milling at ambient conditions without incorporating any solvent. Comprehensive characterization studies and photocatalytic evaluations of the synthesized Fe2O3-TiO2 were conducted in this study. It was verified that Fe2O3-TiO2 possessed crystalline structures of γ-Fe2O3, anatase and rutile TiO2. Also, a good dispersion of Fe and O elements within the TiO2 framework was attained. A detection of FeOTi bond elucidated a substitution of Ti4+ by Fe3+ in the TiO2 lattice sites through mechanical milling, which ultimately enhanced the photocatalytic activities of Fe2O3-TiO2. Moreover, Fe2O3-TiO2 exhibited enhanced catalytic properties in terms of specific surface area (58.40 m2/g), band gap (2.95 eV), and charge separation in comparison with commercial P25. The present work also proved that both characteristics and photoactivity of Fe2O3-TiO2 were significantly affected by its synthesis conditions (milling time, milling speed, and Fe2O3 loading). The highest treatment efficiency of PPME (62.3% of chemical oxygen demand or COD removal) was achieved using Fe2O3-TiO2, which was synthesized at 20 min, 250 rpm and 1 mol% of milling time, milling speed, and Fe2O3 loading, respectively. Noticeably, the photoactivity of the Fe2O3-TiO2 was more superior to P25 (40.6% of COD removal). This study proved that mechanochemical process enabled the green synthesis of Fe2O3-TiO2 that could be used in the treatment of real industrial wastewater.

Bacterial Lignin Peroxidase Mediated Biobleaching and Biodegradation of Paper and Pulp Mill Effluent

Large amount of lingo-cellulosic waste generated by forestry, agricultural practices, paper-pulp industries and textile dye-stuff industries poses a severe environmental pollution problem. Paper factory effluent is one of the major pollutants on the earth because it is highly coloured. The persistent dark brown colour is due to dissolved lignin based synthetic, aromatic and chlorinated compounds derived from the blow heat condensate, pulp decker washing, chlorine and alkali bleach waste, black liquor spillage and foul evaporator condensate. Selection of correct and ecofriendly treatment method for paper-pulp mill waste-water prior to discharge into the environment is still a matter of concern. In the present study, the application of the lignin peroxidase enzyme as crude extracts of the bacterial isolate cultures was reported as an effective tool in biobleaching and biodegradation of paper pulp mill effluent which was measured spectrophotometrically. The isolates Sphingomonas paucimobilis and Corynebactrium jeikeium were found to be an efficient biobleaching agent as compared to the other isolates studied. They showed 91.32%, 86.57%, 84.21% and 83.82%, 82.43% and 78.94% biobleaching respectively when applied as axenic cultures while the mixed consortia being the most effective showed the biobleaching in the range of 91.61%, 89.47% and 86.84% of the effluent 50%, 75% and 100% respectively.

Studies on the adverse effects of bleached sulphite pulp mill effluents on physiology of liver function in Heteropneustes fossilis

Studies on the adverse effects of bleached sulphite pulp mill effluents on physiology of liver function in Heteropneustes fossilis

Evaluation of the Phytotoxic and Genotoxic Potential of Pulp and Paper Mill Effluent Using Vigna radiata and Allium cepa

Pulp and paper mill effluent induced phytotoxicity and genotoxicity in mung bean (Vigna radiata L.) and root tip cells of onion (Allium cepa L.) were investigated. Physicochemical characteristics such as electrical conductivity (EC), biological oxygen demand (BOD5), chemical oxygen demand (COD), and total phenols of the pulp and paper mill effluent were beyond the permissible limit specified for the discharge of effluent in inland water bodies. Compared to control plants, seedling exposed to 100% effluent concentration showed a reduction in root and shoot length and biomass by 65%, 67%, and 84%, respectively, after 5 days of treatment. A. cepa root tip cells exposed to effluent concentrations ranging from 25 to 100% v/v showed a significant decrease in mitotic index (MI) from 32 to 11% with respect to control root tip cells (69%) indicating effluent induced cytotoxicity. Further, the effluent induced DNA damage as evidenced by the presence of various chromosomal aberrations like stickiness, chromosome loss, anaphase bridge, c-mitosis, tripolar anaphase, vagrant chromosome, and telophase bridge and micronucleated and binucleated cell in A. cepa. Findings of the present study indicate that pulp and paper mill effluents may act as genotoxic and phytotoxic agents in plant model system.

Enhanced Removal of COD and Color in Paper-making Wastewater by Ozonation Catalyzed by Fe Supported on Activated Carbon

After biological treatment, pulp and paper mill effluent still may contain large amounts of recalcitrant organic pollutants that need to be further treated. In this study, Fe supported on activated carbon (Fe@AC) was prepared and used as a catalyst in the catalytic ozonation of pulp and paper mill effluent. The activity of this catalyst was studied in terms of color and chemical oxygen demand (COD) removal efficiencies. Results showed that the COD removal rate was increased by 21% in the presence of the Fe@AC catalyst. After 60 min of ozonation (3g/h ozone flow rate) of the pulp and paper mill effluent (initial COD 360 mg/L), COD removal rates reached 56% in the presence of Fe@AC, 43% using AC as catalyst, and only 35% with ozonation alone. Ozone alone can achieve satisfactory color removal results. Owing to the scavenging effect of carbonate and bicarbonate ions towards hydroxyl radicals, the COD removal rate in Fe/AC catalytic ozonation of the effluent was strongly inhibited in the presence of these two ions. The COD removal rate followed the pseudo-second-order kinetics model well. The COD removal rate constant in the Fe@AC/O3 process was about 1.6 times higher than that of the AC/O3 process, and approximately 2.1 times higher than that of ozone alone.

Black Liquor Electrolysis for Hydrogen and Lignin Extraction

Black liquor is a pulp mill effluent from wood cooking with a solid content of 15-18 wt.%, which is mostly lignin. The present study focuses the electrolysis of black liquor for energy recovery. The process has several economic and environmental advantages, as it simultaneously generates a clean fuel (hydrogen) at the cathode and a precipitated material with economic value (lignin) at the anode surface. Platinum, nickel, and AISI 304 stainless steel bulk electrodes are tested for black liquor electrolysis, both as anodes and as cathodes. Voltammetric methods are used to study the lignin oxidation in the black liquor at room temperature, allowing the calculation of kinetic parameters such as the charge transfer coefficient and the number of exchanged electrons. The hydrogen evolution reaction in the black liquor is also evaluated. A small-scale laboratory black liquor electrolyzer using Ni plates is assembled and its operation parameters are evaluated.

Antifouling grafting of ceramic membranes validated in a variety of challenging wastewaters

Compared to traditional separation and purification techniques, membrane filtration is particularly beneficial for the treatment of wastewater streams such as pulp and paper mill effluents (PPME), olive oil wastewater (OOWW) and oil/gas produced water (PW). However, severe membrane fouling can be a major issue.In this work, the use of ceramic membranes and the potential for the broad applicability of a recently developed antifouling grafting was evaluated to tackle this issue. To this end, the fouling behavior of native and grafted membranes was tested in the selected difficult wastewater streams, both in dead-end and in cross-flow mode. In addition, the quality of the produced permeate water was determined to assess the overall performance of the investigated membranes for reuse or recycling of the treated wastewater.The obtained results show that grafting significantly enhances the antifouling tendency of the ceramic membranes. Particularly, the membrane grafted with methyl groups using the Grignard technique (MGR), showed in all cases no or negligible fouling as compared to the native membrane. As a consequence, the process flux or filtration capacity of the MGR membrane in cross-flow is always higher and more stable than the native membrane, even though the grafting lowers the pure water flux. Hence, the inert character of the MGR membrane is repeatedly proven and shown to be broadly applicable and generic for anti-fouling, without loss in permeate quality.Moreover, in case of OOWW, the quality of the MGR permeate is even better than that of the native membrane due to its lower fouling. All results can be explained taking into account the physico-chemical properties of foulants and membranes, as shown in previous work. In conclusion, the use of MGR membranes could provide an optimum economical solution for the treatment of the selected challenging wastewaters.

Sublethal effects of pulp and paper mill effluent on two commonly cultured carps: a SEM- and EDS-based hematological biomarker analysis.

Blood being a vehicle for the transport of industrial pollutants in living system, fish hematology is considered as potent biomarker. In the present study, we investigated respective sublethal effects of pulp and paper mill effluents on hematology of two commonly cultured carps, Cyprinus carpio and Ctenopharyngodon idella, using optical, scanning electron microscopy and energy-dispersive X-ray spectroscopy. Irrespective of species, results showed significant decrease in erythrocyte, hematocrit and hemoglobin contents while an increase in white blood cell counts (P<0.05). We observed an increasing trend of MCV (170.0±3.07 to 193.16±2.5) and MCH (34.31±1.89 to 38.71±3.61) up to 28th day in C. carpio (P<0.05), while, in C. idella, the highest percent increase in MCV (180.8±2.19) and MCH (32.9±0.62) was observed on seventh exposure day, which subsequently declined, respectively, to 173.1±17.1 and 27.9±2.45 on 28th day. Unlike C. carpio, significant and progressive MCHC declining trend (18.23±0.28 to 16.13±0.31) was observed in C. idella. The most commonly observed abnormalities under SEM include echinocytes, cytoplasmic blebbing, cytoplasmic ring, spherocytes, lobopodial projections and acanthocytes in red blood cells of exposed fishes. EDS further revealed the presence of aluminum, antimony, arsenic, cadmium, mercury, tungsten, zinc and titanium; some of these metals were not even detected in the effluent samples, suggesting the probable metal bio-concentration in fish tissue, and subsequent jeopardization is a major concern particularly in the industrial area. Our study further suggested the use of sensitive and specific techniques like SEM and EDS in fish hematological biomarker analysis along with the conventional approach.

Impact of Resin and Fatty Acids on Full-Scale Anaerobic Treatment of Pulp and Paper Mill Effluents

Wastewater generated during pulp and paper production usually contains large amounts of organic matter that may be converted to biogas through anaerobic treatment. These effluents can also contain a variety of inhibitors such as resin acids and long-chain fatty acids (RFAs) among other compounds. A multivariate data analysis was conducted with performance and water quality data from an anaerobic reactor at a pulp and paper mill, which provides unprecedented evidence for the long-term inhibitory effects of RFAs during full-scale operation. Although RFAs in the reactor influent did not cause serious process disturbance, they significantly contributed to the variability in the percentage removal of soluble chemical oxygen demand (percent sCOD removal) (∼45% to ∼75%), as well as the variability in volatile fatty acid concentration in the effluent (2 to >20 meq/L). Furthermore, a linear correlation was found between RFA concentrations in the reactor sludge bed and the percent sCOD removal. An effective strategy to remove RFAs before anaerobic treatment is upfront removal of particles within the primary clarifier. Based on an exploratory model, a graphical method is introduced that allows for quick assessment of the extent to which resin acids are sorbed to particles, and associated potential for upfront settling. When the pH of high-solids wastewater is below 7, the majority of resin acids will be associated with particles and a considerable fraction of these can therefore be removed by means of settling or floatation. Finally, a novel liquid chromatography–mass spectrometry method that rapidly quantifies major RFA constituents was developed. In the full-scale reactor, dehydroabietic acid (DHA) represented the bulk (∼92%) of the resin acids within the granular sludge. DHA in sludge warrants special attention and should be monitored closely.

Removal of nutrients and organic pollution load from pulp and paper mill effluent by microalgae in outdoor open pond

A mixed culture of microalgae, containing two Scenedesmus species, was analysed to determine its potential in coupling of pulp and paper mill effluent treatment and microalgal cultivation. Laboratory studies suggested that 60% concentration of wastewater was optimum for microalgal cultivation. A maximum of 82% and 75% removal of BOD and COD respectively was achieved with microalgal cultivation in outdoor open pond. By the end of the cultivation period, 65% removal of NO3-N and 71.29% removal of PO4-P was observed. The fatty acid composition of mixed microalgal culture cultivated with effluent showed the palmitic acid, oleic acid, linoleic acid and α-linolenic acid as major fatty acids. The results obtained suggest that pulp and paper mill effluent could be used effectively for cultivation of microalgae to minimise the freshwater and nutrient requirements.

Black Liquor Electrolysis for Hydrogen and Lignin Extraction

Black liquor is a pulp mill effluent from wood cooking and has a solid content of 15-18% (weak black liquor), which is mostly lignin, an organic compound that finds wide applications in the market. Black liquor is currently used for steam generation purposes, by burning it, which is not an efficient process due to the undifferentiated combustion of the liquor, losing most of the lignin potential. Considering the world’s energy picture, it is essential to develop sustainable energy generation alternatives, including through waste recovery. Having this in mind, the current work focuses on the electrolysis of black liquor for energy recovery. The process has several economic and environmental advantages, as it simultaneously generates a clean fuel (hydrogen) at the cathode and a precipitated material with economic value (lignin) at the anode surface [1]. The generated hydrogen can be eventually fed to a fuel cell that partially powers the electrolysis plant, thereby decreasing the electricity costs. Herein, platinum (Pt), nickel (Ni), and AISI 304 stainless steel bulk electrodes are tested for black liquor electrolysis, both as anodes and as cathodes. Voltammetric methods are used to study the lignin anodic oxidation at the Pt, Ni and AISI 304 electrodes at temperatures ranging from 25 to 55 ºC. Kinetic and diffusional parameters are calculated (e.g., charge transfer and diffusion coefficients, number of exchanged electrons). The hydrogen evolution reaction in the black liquor is also evaluated at the same electrodes, with Pt and Ni showing the best performance. Activation energies are calculated for both electrochemical processes. Finally, a small-scale laboratory black liquor electrolyzer using Ni plates, both for anode and for cathode, is assembled and its operation parameters are evaluated, specifically the applied cell voltage and the electrolysis duration. The produced lignin is characterized by MIR and reveals a high purity compared with typical lyophilized and Klason lignin. [1] H.R. Ghatak, S. Kumar, P.P. Kundu, Int. J. Hydrogen Energy 33 (2008) 2904-2911.

Reusing pulp and paper mill effluent as a bioresource to produce biohydrogen through ultrasonicated Rhodobacter sphaeroides

Pulp and paper industry is a water-intensive industry. This industry commonly produces considerable amount of effluent, especially from virgin raw materials processing. The effluent, namely pulp and paper mill effluent has the potential to adversely affect the receiving watercourses. However, the nutrients in the pulp and paper mill effluent could be reused as a substrate in biohydrogen production. In this study, photofermentative biohydrogen production was investigated using Rhodobacter sphaeroides and pulp and paper mill effluent as a substrate. An application of low power ultrasound on R. sphaeroides was predicted to increase photofermentative biohydrogen production but excessive ultrasound effects might inhibit the production due to possible cell disruption. Hence, various ultrasonication duration (5, 10 and 15min) and amplitude (15%, 30% and 45%) were applied on the bacteria to determine the recommended ultrasonication conditions for improving biohydrogen production. The recommended conditions were operated at ultrasonication amplitude and duration of 30% and 10min, respectively. A maximum biohydrogen yield of 9.62mL bioH2/mL medium was obtained under this condition, which was 66.7% higher than the result obtained using R. sphaeroides without undergoing ultrasonication (control). The light efficiency and cell concentration were increased by 67% and 150%, respectively, using ultrasonication amplitude and duration of 30% and 10min, respectively as compared to the control. The present results demonstrated that moderate power of ultrasonication applied on R. sphaeroides was an effective method for enhancing photofermentative biohydrogen production using raw pulp and paper mill effluent as a bioresource.