Search

A two-step process involving coagulation-flocculation followed by solar photocatalysis – based Advanced Oxidation Process (AOP) using TiO2-Reduced Graphene Oxide (TRGO) nanocomposite as catalyst ha...

Lignin in chemical pulping waste, or black liquor (BL), can be converted into various products via supercritical water gasification (SCWG). However, the inherited alkaline contents from the pulping chemicals may affect the product yields and properties. In this research, the influence of the residual alkali on the product distribution via SCWG of soda BL and kraft BL was evaluated. The SCWG was performed in a batch quartz reactor for 10 min at various temperatures (673, 773 and 873 K) and pressures (250, 300 and 400 bar). The highest hydrogen (H2) production occurred at 873 K for the soda BL. The water–gas shift reaction with sodium ions played an important part in the H2 production, while only small amounts of methane and carbon monoxide were detected. Hydrocarbons, carboxylic acids and esters were the dominant substrates in the liquid products, which denoted the potential of this method for bond cleaving of the lignin macromolecule. As a result, BL, which typically contains alkali salt, was an a...

Paper machine white water is generally characterized as a high concentration of suspended solids and organic matters. A combined physicochemical-biological and filtration process was used in the study for removing pollutants in the wastewater. The removal efficiency of the pollutant in physicochemical and biological process was evaluated, respectively. Furthermore, advanced technology was used to analyse the water quality before and after the process treatment. Experimental results showed that the removal efficiency of suspend solids (SS) of the system was above 99%, while the physicochemical treatment in the forepart of the system had achieved about 97%. The removal efficiency of chemical oxygen demand (COD) and colour had the similar trend after physicochemical treatment and were corresponding to the proportion of suspended and the near-colloidal organic matter in the wastewater. After biological treatment, the removal efficiency of COD and colour achieved were about 97% and 90%, respectively. Furthermore, molecular weight (MW) distribution analysis showed that after treatment low MW molecules (5 kDa) increased. Three-dimensional excitation-emission matrix fluorescence analysis showed that most humic-like substances were effectively removed during the treatment. The analyses of gas chromatography/mass spectrometry showed that the composition of organic matter in the wastewater was not complicated. Methylsiloxanes were the typical organic components in the raw wastewater and most of them were removed after treatment.

The treatment of pulp and paper mill wastewater by combining an ultrafiltration (UF) membrane and advanced oxidation processes (AOPs) was investigated at a bench scale. In the present study, the effects of impressive parameters on membrane fouling such as CaCl2 (mg/L), pH, and temperature (°C) were studied using response surface methodology (RSM). According to the results yielded, at the temperature of 45°C, pH of 10 and CaCl2 concentration of 400 mg/L, the fouling reached its minimum (32%). Therefore, scanning electron microscopy (SEM) analyses showed that the average thickness of cake layer on the UF surface decreased from approximately 75.37 µm to 11.38 µm by optimizing the operating conditions. The results showed the UF permeate quality is not sufficient. Thus, AOPs applied for permeate. In this way, the performance of sulfate and hydroxyl radicals, generated by the activation of oxidants, such as persulfate () and H2O2, by Fe(II) for removal efficiencies was examined. Accordingly, under the o...

Composting of pig manure is a challenging task that requires appropriate co-substrate and bulking agent to provide optimum composting conditions and reduce nitrogen loss. In this study, paper waste is co-composted with pig manure as well as wood chips as the bulking agents. These raw materials were mixed at three different ratios of paper: pig manure: wood chips = 1:1:0 (pile 1), 3:2:1 (pile 2) and 3:1:1(pile 3), respectively. Each composting pile was about 11 m3 in size equipped with negative-pressure forced aeration. The temperature of all the three piles ranged between 43 and 76°C and therefore produced pathogen-free compost. The overall total carbon reduction of 39%, 36% and 36% were achieved from pile 1, 2 and 3, respectively. The increased with the composting period, indicating the transformation of ammoniacal-N into nitrate by nitrification activity. However, all three piles showed significant variations in soluble at different stages of composting, which could be due to the microbial assim...

High quantities of industrial wastewaters containing a wide range of organic and inorganic pollutants are being directly discharged into the environment, sometimes without proper treatment. Nanotechnology has a tremendous potential improving the existing treatments or even develop new treatment solutions. In this study, nano-TiO

The performance of modified anaerobic inclining-baffled reactor (MAI-BR) treating recycled paper mill effluent (RPME) was investigated by varying the influent chemical oxygen demand (CODin) concentration from 1000 to 4000 mg/L, and the hydraulic retention time (HRT) from 3 to 1 day, corresponding to an organic loading rate increase from 0.33 to 4 g COD/L day. Throughout 126 days of operation, a maximum removal efficiency of up to 96% of chemical oxygen demand (COD) and 99% of biological oxygen demand, methane (CH4) yield of 0.259 L CH4/g COD, and a stable effluent pH of 6.5 were achieved. Furthermore, the compartmental performance showed that most of the organic substrates were removed in the initial two compartments, resulting in low pH and alkalinity levels and a high concentration of volatile fatty acids. Overall, the results showed that the MAI-BR successfully treated RPME, and the performance was affected by the variation of HRT more than the CODin.

An ongoing call to implement a circular economy is underway in the European Union, and a specific attention has been placed on the forest industry, which seeks additional recycling routes for its side streams, including biosludge. Biosludge is often dried and incinerated, thus wasting the nitrogen contained therein. This paper describes a study in which the release of nitrogen during thermal drying, the impact of the drying temperatures of 130°C, 180°C, and 210°C on the mass of ammonia released, and the potential for recovery of nitrogen from biosludge were examined. The results indicate that 1310–1730 mg kgTS−1 of nitrogen was released, which corresponded to 56–74% of the soluble nitrogen in biosolids or 4.0–5.3% of the total nitrogen. Of this released nitrogen, 83–85% was identified in condensate and absorbing water, thus indicating a high potential for recovering nitrogen from biosludge.

A comparative study on the treatment of thermomechanical pulping (TMP) pressate was conducted under thermophilic (55 degrees C) and mesophilic (30 degrees C) temperatures to explore in-mill biological treatment, with the intention to operate under heat-efficient conditions. The experimental study involved sequencing batch reactors (SBRs) operated over 114 days. Receiving a total influent chemical oxygen demand (COD) of 3700-4100 mg L(-1), the COD removal efficiencies of 80-90% and 75-85% were achieved for the mesophilic and thermophilic SBRs, respectively, at a hydraulic retention time (HRT) of 12 and 24h. Excellent sludge settleability (sludge volume index100 mL g(-1) mixed liquor suspended solids) was obtained at both thermophilic and mesophilic SBRs. A higher level of effluent suspended solids was observed under thermophilic conditions. The results support the feasibility of applying thermophilic biological treatment of TMP pressate. The treated effluent has the potential for subsequent reuse as process water after polishing, thus addressing the long-standing desire to develop water system closure for the pulp and paper mill operation.

The urgent need for alternative renewable energies to supplement petroleum-based fuels and the reduction of landfill sites for disposal of solid wastes makes it increasingly attractive to produce inexpensive biofuels from the organic fraction of the municipal solid waste. Therefore, municipal waste in the form of newspaper was investigated as a potential feedstock for fermentable sugars production. Hydrolysis of newspaper by dilute phosphoric acid was carried out in autoclave Parr reactor, where reactor temperature and acid concentration were examined. Xylose concentration reached a maximum value of 14 g/100 g dry mass corresponding to a yield of 94% at the best identified conditions of 2.5 wt% H3PO4, 135 degrees C, 120 min reaction time, and at 2.5 wt% H3PO4, 150 degrees C, and 60 min reaction time. For glucose, an average yield of 26% was obtained at 2.5 wt% H3PO4, 200 degrees C, and 30 min. Furfural and 5-hydroxymethylfurfural (HMF) formation was clearly affected by reaction temperature, where the higher the temperature the higher the formation rate. The maximum furfural formed was an average of 3 g/100 g dry mass, corresponding to a yield of 28%. The kinetic study of the acid hydrolysis was also carried out using the Saeman and the two-fraction models. It was found for both models that the kinetic constants (K) depend on the acid concentration and temperature. The degradation of HMF to levulinic acid is faster than the degradation of furfural to formic acid. Also, the degradation rate is higher than the formation rate for both inhibitors when degradation is observed.

Start-up period is considered to be the most unstable and difficult stage in anaerobic process and usually takes a long time due to slow-degree adaptation of anaerobic microorganisms. In order to achieve a shorter start-up period, a novel modified anaerobic baffled reactor (MABR) has been developed in this study, where each modified baffle has its own characteristics (form/shape) to facilitate a treatment ofrecycled paper mill effluent (RPME). The results ofphysico-chemical characteristics showed that effluent from recycled paper mill consisted of 4328mgL-1 chemical oxygen demand (COD), 669mg L-1 biochemical oxygen demand and 501mg L-1 volatile fatty acid. It also consisted of variety of heavy metals such as zinc, magnesium, iron and nickel at concentrations of 1.39, 12.19, 2.39 and 0.72 mgL-1, respectively. Performance of MABR during the start-up period showed that methane production reached 34.7% with COD removal of 85% at steady state. The result indicates that MABR was successfully operated during the start-up period in treating RPME within a period of less than 30 days.

Municipal wastewater activated sludge contains a mixed microbial community, which can be manipulated to produce biocrude, a lipid feedstock for biodiesel production. In this study, the potential of biocrude production by activated sludge microorganisms grown in three different types of pulp and paper mill wastewaters was investigated. A 20% (v/v) activated sludge was inoculated into pulp and paper wastewater, supplemented with glucose (60 g/L) and nutrients (nitrogen and phosphorus) to obtain a high carbon to nitrogen ratio (70:1). The culture was incubated aerobically for seven days. The results showed that the activated sludge microorganisms were able to grow and accumulate lipids when cultivated in amended wastewaters. Microorganisms growing in anaerobic settling pond effluent water showed the highest lipid accumulation of up to 40.6% cell dry weight (CDW) after five days of cultivation compared with pulp wash wastewater (PuWW) (11.7% CDW) and mixed wastewater (MWW) (8.2% CDW) after seven days of cultivation. The lipids mostly contained C16-C18 fatty acids groups with oleic acid and palmitic acid being the dominant fatty acids. The maximum biodiesel yield was about 6-8% CDW for all the wastewaters. The results showed the potential of utilizing pulp and paper mill effluents and other waste streams, such as activated sludge for the sustainable production of lipids for biofuel production.

Co-digestion of pulp and paper sludge (PPS) and food waste (FW) in a batch-fed digestion system was conducted on a laboratory scale. Three reactors named A1, A2, and A3 were tested. PPS and FW mixed at different mass ratios of 1:3, 1:1, and 3:1, respectively, were loaded in the reactors. Bioconversion at high efficiency was obtained in the system. The accumulative methane yield of each reactor was 144mLg(-1)VSfed (A1), 256 mL g(-1) VSfed (A2), and 123 mL g(-1)VSfed (A3). The soluble chemical oxygen demand (COD) removal efficiencies reached 73.2% (Al), 93.9% (A2), and 79.6% (A3). A pH in the range 5.8-8.4 was obtained in the three reactors without adjustment due to the high buffer capacity of the mixing feedstock. No toxicity inhibitions of volatile fatty acids and NH3-N occurred in reactor A2. This study showed that it was good for co-digestion of PPS and FW in a mass ratio of 1:1 for methane production, which resulted in higher methane yield, a greater buffer capacity, a higher organics removal efficiency, and a more stable process.

Primary sludge from a Portuguese pulp and paper mill, containing 60% of carbohydrates, and unbleached pulp (as reference material), with 93% of carbohydrates, were used to produce ethanol by simultaneous saccharification and fermentation (SSF). SSF was performed in batch or fed-batch conditions without the need of a pretreatment. Cellic® CTec2 was the cellulolytic enzymatic complex used and Saccharomyces cerevisiae (baker's yeast or ATCC 26602 strain) or the thermotolerant yeast Kluyveromyces marxianus NCYC 1426 were employed. Primary sludge was successfully converted to ethanol and the best results in SSF efficiency were obtained with S. cerevisiae. An ethanol concentration of 22.7 g L−1 was produced using a content of 50 g L−1 of carbohydrates from primary sludge, in batch conditions, with a global conversion yield of 81% and a production rate of 0.94 g L−1 h−1. Fed-batch operation enabled higher solids content (total carbohydrate concentration of 200 g L−1, equivalent to a consistency of 33%) a...

Paper mill sludge (PMS) was utilized to prepare granular activated carbon (GAC) fillers for fluidized-bed bioreactor (FBBR) through stream activation. The properties of the PMS were tested and the optimum conditions for the production process were determined. Then, the GAC fillers were used in the FBBR to investigate the capacity for wastewater treatment. The results showed that the optimal conditions were: carbonization temperature of 450 degrees C, carbonization time of 50 min, activation temperature of 800 degrees C and activation time of 60 min. The specific surface area of the GAC fillers was 130 m2/g and the grain density was 1.34 x 10(3) kg/m3. The wastewater treatment results showed that after40 days ofrunning, under the conditions of influent COD of 800 mg/L and HRT of2 h, the COD removal efficiency was about 90%, which demonstrated that PMS-based GAC fillers were feasible for FBBR.

A pilot scale granular activated carbon-sequencing batch biofilm reactor with a capacity of 2.2 m3 was operated for over three months to evaluate its performance treating real recycled paper industry wastewater under different operational conditions. In this study, dissolved air floatation (DAF) and clarifier effluents were used as influent sources of the pilot plant. During the course of the study, the reactor was able to biodegrade the contaminants in the incoming recycled paper mill wastewater in terms of chemical oxygen demand (COD), adsorbable organic halides (AOX; specifically 2,4-dichlorophenol (2,4-DCP)) and ammoniacal nitrogen (NH3-N) removal efficiencies at varying hydraulic retention times (HRTs) of 1-3 days, aeration rates (ARs) of 2.1-3.4 m3/min and influent feed concentration of 40-950 mg COD/l. Percentages of COD, 2,4-DCP and NH3-N removals increased with increasing HRT, resulting in more than 90% COD, 2,4-DCP and NH3-N removals at HRT values above two days. Degradation of COD, 2,4-DCP and NH3-N were seriously affected by variation of ARs, which resulted in significant decrease of COD, 2,4-DCP and NH3-N removals by decreasing ARs from 3.4 m3/min to 2.1 m3/min, varying in the ranges of 24-80%, 6-96% and 5-42%, respectively. In comparison to the clarifier effluent, the treatment performance of DAF effluent, containing high COD concentration, resulted in a higher COD removal of 82%. The use of diluted DAF effluent did not improve significantly the COD removal. Higher NH3-N removal efficiency of almost 100% was observed during operation after maintenance shutdown compared to normal operation, even at the same HRT of one day due to the higher dissolved oxygen concentrations (1-7 mg/l), while no significant difference in COD removal efficiency was observed.

Paper mill, chemistry, textile and food processing industries are high water consumers. Within the framework of the European project Aquafit4Use, the possibility to close the on-site water loop is studied. The aim is to find new technologies or innovative treatment trains to produce water that is 'fit for use' in the industrial process; an example of a paper mill is given. Laboratory-scale tests on nine technologies were carried out to determine the best suitable treatment train: anaerobic process (already on site) --aerobic process (already on site) --Flexible Fibre Filter Module --softening --nanofiltration --evapoconcentration or ozonation on nanofiltration (NF) concentrate. This treatment train is currently compared on site at pilot scale to another treatment train including some modifications on the existing on-site biological treatment: anaerobic process --softening --membrane bioreactor --nanofiltration --evapoconcentration or ozonation of NF concentrate.

The precipitation of dissolved sulphide ions by electrocoagulation was studied at laboratory scale using pulp and paper mill wastewaters. Concentrations of dissolved organic carbon and phosphorus were analysed before and after the electrocoagulation process to examine the suitability of the process for treatment of sulphide odour from pulp and paper mill wastewater. The electrochemical cell used in this study was constructed from monopolar dissolving iron electrodes. The dissolved iron concentration was directly proportional to the applied electric charge (C/L) at the tested current densities. Electrochemically produced ferrous iron (Fe2+) precipitated dissolved sulphide ions efficiently. Electricity consumption of the treatment was 4-8 C/mg S(2-) while iron consumption was 1.1-2.2 mg/mg S(2-) during the initial phase of the sulphide precipitation when the applied electric charge was 10-60 C/L. When 60 C/L was applied, 88% of dissolved sulphides and 40% of phosphorus was precipitated. The reduction in DOC was low during the sulphide precipitation. According to these results, electrocoagulation can precipitate dissolved sulphides effectively and thereby reduce sulphide odours of pulp and paper mill wastewaters.

Many industries are charged fees based on the organic loads in effluents. Therefore, it can be advantageous to reduce the wastewater strength prior to discharge. We investigated the use of microbial fuel cells (MFCs) to reduce the chemical oxygen demand (COD) of a paper-plant wastewater while at the same time producing electricity in a continuous flow system. At a hydraulic retention time (HRT) of six hours, COD removal using an unamended wastewater (506 mg/L COD) (organic loading rate, OLR = 2.0 kg COD/(m3 d)) was 26 +/- 2%, with a power density of 5.9 +/- 0.2 W/m3 (210 +/- 7 mW/m2). This amount of power was similar to the maximum power density (5.2 +/- 0.4 W/m3) produced in fed-batch tests using a slightly lower strength wastewater in the same device (405 mg/L COD). Increasing the HRT to 25 h (OLR = 0.5 kg COD/(m3 d)) increased COD removal (41 +/- 2%) but substantially decreased power (2.8 +/- 0.3 W/m3). While wastewater strength affected removal rates, the solution conductivity (0.8 mS/cm) was primarily a factor in low power production. These results demonstrate that MFCs can be used to reduce organic loads in effluents at relatively short HRTs, while at the same time generating power.

Increasingly stringent effluent quality limits for bleached kraft pulp mills pose a great challenge to mill wastewater system managers since these limits can require levels of chemical oxygen demand (COD) removal efficiency rarely reported for biological treatment of these types of effluents. The present study was therefore undertaken to better understand the nature of recalcitrant COD in bleached kraft pulp effluents that persists through the biological treatment system. Bleaching effluents from a Brazilian eucalypt bleached kraft pulp mill were collected and treated in a bench-scale sequencing batch reactor. Organic matter in raw and treated effluents was characterized before and after separation into low and high molecular mass fractions. Biological treatment removed 71% of the COD, with 83% removal of the low molecular mass COD but only 36% removal of the high molecular mass COD. Microorganisms capable of degrading the recalcitrant COD were isolated from enrichment cultures of the original activated sludge fed on fractions of the bleaching effluent that presented low biodegradabilities. Use of a microbial consortium composed of ten of these isolates to treat the biologically treated effluent removed a further 12% of the effluent COD, all from the high molecular mass fraction. Results of this research indicate that microorganisms with potential for degrading recalcitrant COD are present in activated sludge, but that these are not metabolically active during normal activated sludge treatment of mill effluents. The use of biological selectors in the treatment system to promote growth of such microorganisms may enhance removal of recalcitrant organic matter.

This study characterizes the combustion of paper and sewage sludge in a pilot-scale fluidized bed. The highest temperature during combustion within the system was found at the surface of the fluidized bed. Paper sludge containing roughly 59.8% water was burned without auxiliary fuel, but auxiliary fuel was required to incinerate the sewage sludge, which contained about 79.3% water. The stability of operation was monitored based on the average pressure and the standard deviation of pressure fluctuations. The average pressure at the surface of the fluidized bed decreased as the sludge feed rate increased. However, the standard deviation of pressure fluctuations increased as the sludge feed rate increased. Finally, carbon monoxide (CO) emissions decreased as oxygen content increased in the flue gas, and nitrogen oxide (NOx) emissions were also tied with oxygen content.

Anaerobic digestion of alkaline kraft elemental chlorine-free bleaching wastewater in two mesophilic, lab-scale upflow anaerobic sludge bed reactors resulted in significantly higher biogas production (250±50 vs. 120±30 NmL g [Formula: see text]) and reduction of filtered total organic carbon (fTOC) (60±5 vs. 43±6%) for wastewater from processing of hardwood (HW) compared with softwood (SW). In all cases, the gas production was likely underestimated due to poor gas separation in the reactors. Despite changes in wastewater characteristics, a stable anaerobic process was maintained with hydraulic retention times (HRTs) between 7 and 14 h. Lowering the HRT (from 13.5 to 8.5 h) did not significantly affect the process, and the stable performance at 8.5 h leaves room for further decreases in HRT. The results show that this type of wastewater is suitable for a full-scale implementation, but the difference in methane potential between SW and HW is important to consider both regarding process dimensioning and biogas yield optimization.

The aim of this work is to study the possibilities of effluent recycling in a bleached Kraft pulp mill, for a better water management. To avoid problems associated with effluent recycling (corrosion, odors, loss in pulp and paper quality), wastewaters have to be treated before recycling. This study is particularly focused on organic matter removal. Several treatments are applied on a biological secondary effluent: adsorption on activated carbon, coagulation with ferric chloride or alum sulfate, precipitation with lime, ozonation and catalytic ozonation. These techniques are compared in terms of COD (Chemical Oxygen Demand) removal. Catalytic ozonation is finally chosen as the most effective solution to achieve 50% of COD removal in the effluent. The characteristics of the effluent treated according to this technique are then used to simulate the impact of its reuse in the process for pulp production. The study is focused on the changes in these parameters in the various stages of bleaching and final washing when water is replaced by the wastewater treated or directly issued from the wastewater treatment plant. The simulation demonstrates the need of a tertiary treatment to eliminate COD in order to avoid possible reactant overconsumption and decrease in pulp brightness. Chloride and sulfate ions which could cause corrosion should also be removed.

The tremendous environmental impact of pulping and bleaching effluents and the relatively low efficiency of the current biological remediation processes represent one of the most important problems of the paper industry. In this work the efficiency of heterogeneous and homogeneous advanced oxidative processes was evaluated toward the degradation of model substrates (phenol and lignin) and the remediation of paper effluents. Best results were found by application of the UV-H2O2 system, with almost total discoloration of both pulping and bleaching effluents and typical COD removal higher than 60%, at reaction times of 120 min. In view of the reported results, and mainly on account of the simplicity of the UV-H2O2 system, shows good potential for the advanced process to remediation of recalcitrant effluents like those studied in this present work.

Nowadays many industries are considering the recycling of process waters as a way of improving environmental safety, preventing pollution, and avoiding the loss of valuable production materials. One industry in the forefront of this trend is the pulp and paper industry. Lignin is a pollutant present in the mill process waters and such macromolecules can cause problems during biological treatment of process waters. Wet oxidation (WO) is a process that can be used as a pre-treatment method for lignin fragmentation and improvement of biodegradability. Wet oxidation (WO) under alkaline conditions permits faster lignin fragmentation than the conventional WO process and, therefore, should favour biodegradability improvement. In this study, the experiments were carried out in a high-pressure batch reactor with an alkali lignin solution at temperatures up to 438 K, an alkali concentration of 1.5-3.5 g l(-1) and an oxygen partial pressure of 0.4 to 1.5 MPa. At an alkali concentration of 3.5 g l(-1)1 and 0.4 MPa of oxygen partial pressure, an increase in BOD/COD ratio was achieved from an initial 11% to 71%. The experiments also showed that the amount of small molecules in the solution measured by Immediately Available BOD (IA BOD) depends on the amount of alkali added and the operating temperature.

Konark Pulp and Paper Industries Private Limited is a medium size industry producing 1600 m3 of wastewater a day. The existing water treatment system of the industry was found to be ineffective both in performance and economy. In the present study, a new system of treatment has been developed using water hyacinth Eichornia crassipes, coagulation by lime and alum, followed by rapid sand filtration. The performance efficiency of each unit viz. Eichornia treatment; coagulation with lime, with alum, and with lime:alum combinations, and filtration was studied. Water quality parameters considered were Biological Oxygen Demand, Chemical Oxygen Demand, Dissolve Oxygen, Total Dissolved Solids, turbidity, percentage transmission, and water colour. Based on the individual performance of each unit, a continuous system has been designed and was tested. The new system of treatment could treat the wastewater to the discharge standards and also was found economically feasible. Testing culture of fish (tilapia) proved that the treated water could be safely discharged into natural waters. All fish tested, survived and remained healthy throughout the period of testing. Culture of fish further improved the water quality.

The main objective of this study was to analyse cost reduction by reducing the use of fresh water in the cellulose bleaching process and to make it easier to obtain water in a closed circuit. Eucalyptus oxygen delignified industrial pulp was used. The pulp was bleached 10 times in the D(E+P)DP sequence in the same conditions. Counter current washing was used in the bleaching stages, and each sequence was carried out with different wash factors: 9, 6, 3, and 0 m³ of distilled water/ton of oven dry pulp. The goal was to reach brightness of 92±0.5% ISO. The results showed that there was a chemical oxygen demand (COD) increase and brightness reversion, but the kappa number and viscosity did not change. The apparent colour was increased by increasing COD in the effluent during the cycles and by decreasing the wash water. Up to 3 m³/t of water was tolerable and even recommended to wash pulp. Nine cubic metre per tonne of fresh water is most commonly used in the industry, so water savings make the implementation of the process possible.

Present study relates to the corrosivity of paper mill effluent and corrosion performance of stainless steel (SS) as a construction material for the effluent treatment plant (ETP). Accordingly, immersion test and electrochemical polarization tests were performed on SS 304 L, 316 L and duplex 2205 in paper mill effluent and synthetic effluent. This paper presents electrochemical polarization measurements, performed for the first time to the best of the authors' information, to see the influence of chlorophenols on the corrosivity of effluents. The corrosivity of the effluent was observed to increase with the decrease in pH and increase in Cl- content while the addition of SO4- tends to inhibit corrosion. Mill effluent was found to be more corrosive as compared to synthetic effluent and has been attributed to the presence of various chlorophenols. Corrosion performance of SS was observed to govern by the presence of Cr, Mo and N contents.

In this paper, the preliminary study on the impact of filamentous particles (FP) in the septic tank effluent (STE) on filter cake (FC) development was presented. The number, length and diameter (30 p./cm3, 451 and 121 microm, respectively, on average) of FPs were measured using microscope image analysis of STE samples condensed using a vacuum evaporation set. Results of this study showed, that 0.73% of volatile suspended solids (VSSs) mass from the STE occurs in the form of FPs. No correlation between FP total mass and VSS was found. An experiment with a layer of FPs simulated by ground toilet paper was conducted and showed the impact of this layer (4.89 mg/cm2) on wastewater hydraulic conductivity--for an FC with FPs (FC-FP), hydraulic conductivity was seven times lower than for the FC without the FP layer, and on outflow quality (lower concentration of organic matter expressed as chemical oxygen demand (COD) in effluent from the FC-FP filter than in the effluent from the FC filter: 618 and 732 gO2/m3, respectively). Despite a relatively small amount of FPs in STE solids (as volume fraction), they play an important role in FC development due to their relatively high length and low degradability. Probably relatively small pores of the FC containing FPs (FC-FP) caused a small particle blocking and a decrease in permeability.

Four specices of detritivorous (humus-former) earthworms were tested for their ability to vermicompost paper waste blended with cowdung in 6:1 (w/w) ratio. The anecic Lampito mauritii, Kinberg and the epigeic Eudrilus eugeniae, Kinberg were the most effective of the four species employed; 20 animals of each of these species generated castings amounting to about 52% of the feed mass (75 g) per fortnight. The performance of these two species was followed by the anecic Drawida willsi, Michaelsen and the epigeic Perionyx excavatus, Perrier; they achieved approximately 46% vermiconversion in comparable settings. The vermireactors were sustainable as the animals have remained consistently healthy and reproductive over a period of six months, and are continuing to remain so, turning in a steadily rising vermicast output. During this period E. eugeniae have grown to 2.3 times their original weight while the other three species have more than trebled their weights. The studies establish the feasibility of vermicomposting as a viable process for the gainful utilization of paper waste in an environmentally clean manner. They also indicate that all the four species of the worms screened by us are suitable for the process, with L. mauritii and E. eugeniae a shade more efficient than the other two species.

Paper and pulp industries produce large quantities of wastewater which can have adverse effects on the receiving water systems. In the present study lysimeters were used and filled with different soils replicating natural soil horizons and provided with a leachate collection system. The physico-chemical characteristics of the soil in each lysimeter and the quality of wastewater before leaching were assessed. Treated wastewater was evaluated for crop irrigation, and was categorized according to the irrigation water class 'Increasing Problem to Severe Problem' with respect to salinity and specific ion toxicity. Sandy loam soils showed 96% chemical oxygen demand (COD) removal while clay loam soils removed 99% of COD, and the colour removal in both the cases was found to be 100%. Application of wastewater resulted in an increase of pH value, ranging from 6.2-7.6; the electrical conductivity (ECe) of saturated extracts was found to be 0.6-1.7 dS m(-1), and exchangeable sodium percentage (ESP) ranged from 7.8-11.1% in soils. Similarly, an increase in the organic carbon, available nitrogen, phosphorus and potash content of soils was observed when irrigated with wastewater. Wastewater irrigation showed increased grain and straw yield of jowar, wheat and moong. These results permit successful utilization of pulp and paper mill wastewater for crop production without damaging the soils.

In the last ten years, as international environmental protection consciousness has increased, the study and applications of green building, green construction materials and energy savings as well as reduction of carbon dioxide have become urgent issues for governments. In Taiwan, joss papers are burned in more than 11,731 registered shrines or temples in traditional Chinese deity or ancestor worship ceremonies during special holidays or occasions. Instead of placing this large amount of burned joss paper ash (BJPA) in landfills, this study proposes recycling BJPA by replacing some cement with calcined BJPA (CBJPA) in mortar specimens. After BJPA samples were calcined at a high kiln temperature, mortar samples were created using CBJPA to replace cement at seven different levels: 0%, 5%, 10%, 15%, 20%, 25% and 30%. Tests like setting time and compressive strength were performed for macro-analyses; scanning electron microscopy-energy dispersive spectroscopy, X-ray diffraction and thermal gravimetric analysis/differential thermal analysis were carried out for the microstructure and chemical composition analyses. The test results showed that the compressive strengths of specimens with different levels of CBJPA replacement were apparently less than those of the control group (0% CBJPA) at all curing times. The compressive strength and setting time both decreased as the fraction of CBJPA in the mortar increased. Furthermore, because the hydration product did not cement and the mortar specimen structure was loose, the expected strength improvement from the pozzolanic reaction provided by the CBJPA was not clearly observed.

The methane potential of activated sludge from six Swedish pulp and paper mills was evaluated. The methane production potential of sludge samples ranged from 100-200 NmL CH(4) g(-1) volatile solids (VS) and for four of the six sludge samples the potential exceeded 170 NmL CH(4) g(-1) VS. The effects of sludge age and dewatering on the methane production potential were evaluated. The effects of enzymatic and ultrasonic pre-treatment on the digestibility of sludge were also investigated, but energy or enzyme inputs in viable ranges did not exert a detectable, positive effect. Long-term, semi-continuous trials with sludge from two of the mills were also conducted in attempts to develop stable biogas production at loading rates up to 4 g VS L(-1). Cobalt addition (0.5 mg L(-1)) was here found to positively affect the turnover of acetate. High viscosity was a problem in all the experimental reactors and this limited the organic loading rate. Funding Agencies|Swedish Thermal Engineering Research Institute (Varmeforsk)

With a preliminary insight into the source and leaching behaviour ofbisphenol A (BPA) from municipal solid wastes (MSW), five kinds of plastic and four kinds of paper materials were leached by distilled water. Polyvinyl chloride (PVC) waste was found to have the highest BPA content of 12.1 microg x g(-1) and leachability of 34.7% in distilled water, while cardboard with relatively low BPA content also showed a high ratio of leaching (53.6%). Fresh leachate and leachates from a landfill of age 1.5 and 10 years were adopted as leachants for the PVC plastic and cardboard to simulate the leaching behaviour of BPA under a landfill environment. The enhancement of BPA leachability in the 10-year leachate compared with distilled water was higher than that in the other two leachates due to its basic pH and high content of humic organic matters. Meanwhile, the enhancement of BPA leachability by the fresh leachate was higher than that by the 1.5-year leachate, possibly due to the presence of small molecules such as volatile fatty acids, amino acids, etc. The paper waste was not only a minor origin of BPA leaching, but also a controlling factor in retarding BPA transformation. The BPA sorption K(f) value of the cardboard in the Freundlich equation was 0.2224 mg(1-n)) x L(n) x g(-1) (n = 0.7680), higher than that obtained in sorption experiments by natural organic adsorbents such as sediment. It suggested that the presence of paper with a high sorption capacity in MSW will restrain BPA transport and bioavailability in landfills.

The efficiency of advanced oxidation processes (AOPs), enzymatic treatment and combined enzymatic/AOP sequences for the colour remediation of soda and chemimechanical pulp and paper mill effluent was investigated. The results indicated that under all circumstances, the AOP using ultraviolet irradiation (photo‐Fenton) was more efficient in the degradation of effluent components in comparison with the dark reaction. It was found that both versatile peroxidase (VP) from Bjerkandera adusta and laccase from Trametes versicolor, as pure enzymes, decolorize the deep brown effluent to a clear light‐yellow solution. In addition, it was found that in the laccase treatment, the decolorization rates of both effluents were enhanced in the presence of 2, 2’‐azinobis (3‐ethylbenzthiazoline‐6‐sulfonate), while in the case of by VP, Mn+2 decreased the efficiency of the decolorization treatment. The concomitant use of enzymes and AOPs imposes a considerable effect on the colour remediation of effluent samples.

In this study, the electrochemical oxidation technique was used to oxidize sulphides present in paper mill wastewater. Inactivation of anaerobic bacteria in wastewater was also investigated. Sulphide oxidation was effective during the experiments, and the best efficiency was achieved by the smallest current density used. One of the main oxidants of sulphides during the experiments was oxygen. Anaerobic bacteria were better inactivated with higher initial chloride concentration in wastewater because of electrochemically generated chlorine/hypochlorite. Dissolved oxygen, redox potential and pH values of the wastewater increased because of electrochemically generated oxygen-based oxidants and oxidation reactions occurring on the anode. In general, it can be said that sulphide removal was successful in the present study.

This study attempts to evaluate the applicability of chemical oxidation processes to polish biologically treated effluent of a plant manufacturing hardboard from waste paper to comply with the discharge limit of 120 mg l−1 chemical oxygen demand (COD). In the first step, a chemically assisted settling was applied. The optimum results were obtained with alum plus lime with the alum dose of 200 mg l−1. In the second step, chemically assisted settling effluent was fed into an activated sludge system and over 80% COD removal was achieved. In the last step of the experimental study, a series of ozone oxidation and Fenton oxidation methods were tested to remove residual COD. Ozone oxidation provided 80% COD removal. An ozone dose of 40 mg min−1 with a reaction time of two hours was found to be optimum. Catalytic ozonation by using ferric iron, as well as high pH ozonation, Fenton process and H2O2/O3 oxidation did not prove to be more efficient than plain ozonation under these study conditions.

The capillary suction time (CST) test is a commonly used method to measure the filterability and the easiness of removing moisture from slurry and sludge in numerous environmental and industrial applications. This study assessed several novel alterations of both the test methodology and the current standard capillary suction time (CST) apparatus. Twelve different papers including the standard Whatman No. 17 chromatographic paper were tested. The tests were run using four different types of sludge including a synthetic sludge, which was specifically developed for benchmarking purposes. The standard apparatus was altered by the introduction of a novel rectangular funnel instead of a standard circular one. A stirrer was also introduced to solve the problem of test inconsistency (e.g. high CST variability) particularly for heavy types of sludge. Results showed that several alternative papers, which are cheaper than the standard paper, can be used to estimate CST values accurately, and that the test repeatability can be improved in many cases and for different types of sludge. The introduction of the rectangular funnel demonstrated an obvious enhancement of test repeatability. The use of a stirrer to avoid sedimentation of heavy sludge did not have statistically significant impact on the CST values or the corresponding data variability. The application of synthetic sludge can support the testing of experimental methodologies and should be used for subsequent benchmarking purposes.

Ultrafiltration combined with coagulation pretreatment was used to treat two kraft pulp mill wastewaters from first-stage caustic extraction and alkaline bleaching operations, respectively. Both alum and ferric chloride were tested using standard jar apparatus at different dose, pH and ionic strength conditions. Ultrafiltration tests were conducted using a crossflow flat-sheet membrane apparatus operated in the constant transmembrane pressure mode to examine the effects of membrane material, crossflow velocity and transmembrane pressure in terms of permeate flux and treated effluent quality. The results showed that coagulation with both alum and ferric chloride greatly reduced the permeate flux decline rates. In comparison with alum, greater permeate fluxes were obtained with the use of ferric chloride. Among the process parameters examined, coagulant dose was identified as the most important factor affecting the permeate flux. In addition, colour and COD removals were achieved largely by coagulation for alkaline bleaching wastewater while by membrane filtration for caustic extraction wastewater, highlighting the different mechanisms underlying contaminant removal.

Activated carbon with large specific surface area and well-developed porosity was prepared from pyrolysis of K2CO3-impregnated lignin precipitated from reed pulp black liquors. The impregnation ratio was 1:1. The effect of activation temperature upon the Brunauer-Emmett-Teller (BET) specific surface area and pore volume of the carbon was closely investigated. Increasing activation temperature led to an opening and widening of the porous structure below 800'C. Above 800'C, the excess widening of pore led to the decrease of BET surface area and micropore volume. The BET surface area and pore volume of the carbon activated at 800 degrees C were 1395 m(2) g(-1) and 0.7702 ml g(-1) , respectively. The potential application of the carbon activated at 800 degrees C for removal of Cr (VI) was also investigated. The experimental results showed that it had good adsorption capacity.