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With the increased awareness of reusing solid wastes for higher sustainability and the concern of water pollution associated with phosphorus over-emission, there are strong interests in developing solid waste based adsorbents for purifying phosphorus-containing wastewater. As a rich calcium resource, paper mill sludge (i.e., a major solid waste from pulping industry) can be used as phosphorus removal adsorbent after calcination. Thus, in this work, a simple and clean thermally treating route has been proposed for preparing calcium-containing biochar from paper mill sludge. The effect of the physicochemical properties of paper mill sludge and its carbonization condition on phosphorus adsorption has been analyzed. Moreover, the influence of some key adsorption parameters, e.g., biochar dosage, initial pH of solution, co-existing anions, initial phosphorus concentration and contact time has also been investigated. The results showed that the phosphorus adsorption data could be fitted well with pseudo-second-order kinetic and Langmuir isothermal models. The calculated maximum adsorption capacity of the as-prepared optimal calcium-containing biochar could reach to 68.49 mg·g−1 at 25 °C. Combined with the characterization results, it can be reasonably inferred that the adsorption process was chemisorption-dominated. Lastly, the application of this spent adsorbent in agriculture field has also been discussed. In brief, this work provided a feasible strategy for converting paper mill solid waste to an environmental functional material (i.e., calcium-rich biochar) for remediation of eutrophic water.

This study optimizes a novel surfactant-assisted green liquor dregs (GLD) pretreatment of paper mill sludge (PMS), both of which are wastes from the kraft pulping industry, using a combined Response Surface Methodology (RSM) design. Optimized conditions give a maximal reducing sugar release of 16.38 g/L. A substantial reduction in heavy metals aluminum, chromium, cobalt, arsenic, lead, and copper after pretreatment illustrates the enhancement of substrate digestibility by reducing toxic elements. Separate hydrolysis and fermentation (SHF) and simultaneous saccharification and fermentation (SSF) for hydrogen production are assessed. SSF produced a hydrogen yield of 3.72 mL/g, displaying a 36.26% increase from pretreated PMS compared to SHF. These findings provide insights into possible methods of reducing process duration, energy input, and costs incurred with waste disposal within the paper industry. Furthermore, improved hydrogen yield using an SSF process demonstrates the potential beneficiation of pulp and paper GLD and PMS wastes.

Cellulose triacetate (CTA) forward osmosis (FO) membrane from Hydration Technology Innovation (HTI), USA was tested in a locally fabricated FO system to concentrate synthetic and pulp and paper mill wastewater. The industry is among the 17 most polluted industries with intensive water consumption and wastewater generation (MoEFCC, Government of India). The CTA membrane was studied with deionized water as feed solution and 1 M NaCl as draw solution, which resulted into water flux of 5.8 L/m2h and reverse salt flux of 0.2 g/L. A concentration stepping method was used to determine the critical draw concentration with lignin solution as the model feed. There was no deviation in flux between the baseline (deionized water feed) and the lignin solution up to 1.5 M NaCl, but a marginal deviation (8% and 21% respectively at 2 M and 3 M) was seen thereafter. The average water flux after 24 h FO study with synthetic wastewater as feed solution (draw solution 2 M NaCl) was 8 L/m2h, and 80% water recovery. Similar study with pulp and paper wastewater as feed solution (draw solution of 1.5 M NaCl) was 5.4 L/m2h was with 62% water recovery. Lignin and COD rejection in pulp and paper mill wastewater was 90% and 64% respectively. The preliminary results indicate that FO is promising for water and lignin recovery from waste streams.

Paper and pulp mills generate substantial quantities of cellulose-rich sludge materials that are disposed in landfills at a large scale. For sustainability purposes, sludge materials can be bioprocessed to produce renewable fuels and useful chemicals. The enzymatic hydrolysis of cellulose is the process bottleneck that affects the conversion economics directly by using zero-cost raw materials. In order to study and optimize the process, the characteristics of the sludge raw materials should be first evaluated. In this work, sludge samples were obtained from paper mills located at different locations in Wisconsin and Minnesota. Part of the sludge samples was washed (de-ashed) with hydrochloric acid while the other part remained unwashed. The samples were subjected to multiple spectroscopic analyses techniques to evaluate the morphological properties of cellulose fibers and to estimate the total structural carbohydrate content. The results showed that the de-ashing process changed some fiber characteristics and cellulose crystallinity structure in all sludge samples. Sludge sample A (obtained from Kraft pulp and recycled paper mill region) showed a high percentage of fiber, with crystalline cellulose, compared to the other two sludge samples suggesting that sludge A is a valuable source to make value-added products. Aspen Plus mass and energy calculations performed in view of the ‘zero’ cost and the reliable supply of sludge raw materials producing 2 mol H2/mol glucose. Moreover, the results showed that extracting crystalline cellulose from these sludge samples is more profitable than crystalline cellulose made from the other lignocellulosic feedstocks. The results reported here showed that the utilization of these sludge materials would be an economically attractive and promising alternative for the production of hydrogen.

In present investigation, electroless Ni-P-SiC/Ni-P-TiO2-ZrO2 nano-composite platings have been deposited upon mild steel substrate (AISI 1040). A homogeneous and consistent allocation of SiC, TiO2 and ZrO2 nano-particles into EL Ni-P matrix is recognized in as plated and heated (400°C) coupons respectively through SEM and EDAX methods. The investigated coupons exhibited resistance against corrosion in order as: 254SMO > SS2205 > Ni-P-TiO2-ZrO2 as-plated > Ni-P-TiO2-ZrO2 heat treated > Ni-P-SiC as-plated > Ni-P-SiC heat treated > SS316L. The corrosion resistance seems too dependent upon Cr, Mo and N content and hence correlate well with the PRE number of the respective alloys. The conventional materials of construction SS 316L are not suitable for both C and D washers. Avesta 254SMO shows immunity to attack in these environments. On the basis of corrosion resistance, mechanical properties and cost comparison, Avesta 254 SMO seems acceptable material for gaseous phase of C and D washers while duplex stainless steel 2205 and Ni-P-SiC/Ni-P-TiO2-ZrO2 as-plated and heated coatings seems acceptable for the other application in these washers.

Enormous quantities of bagasse are being used as raw material in agro based large integrated pulp and paper mills. Anaerobic technology is an effective means of biodegradation of organic substance in wastewater and energy production of biogas that can be used as an alternative fuel. This study illustrates the effect of HRT on performance of lab scale hybrid upflow anaerobic sludge blanket (HUASB) reactor on treatment of pulp and paper mill bagasse wash water. The lab scale HUASB reactor was designed for an effective volume of 0.013 m3 with bio balls as packing media at the top of reactor and operated under mesophilic condition. After startup period, the reactor was operated with HRTs of 23.55, 15.98, 12.00, 10.03 and 7.97 h for the average influent COD concentrations of 2503.6 mg/L, 3918 mg/L, 5432 mg/L, 6608 mg/L and 7996 mg/L respectively. The results showed that the maximum COD removal efficiencies and TSS removal efficiencies were in the range of 68.60–92.19% and 89.56–94.66% respectively. The minimum and maximum biogas yield of 0.32 and 0.53 m3/kg CODa were obtained at influent concentration of 2503.6 mg/L and 7996 mg/L respectively.

Adding biochar to paper mill biosolids (PB) amendments may affect PB mineralization rate and nitrogen (N) availability. The objective of this 224-day incubation study was to evaluate the effect of amending two PB types varying in carbon (C)/N ratio (PB1, C/N = 24; and PB2, C/N = 13) with three rates (0%, 2%, and 5%) of pine (Pinus strobus L.) biochar produced at 700 °C on the dynamics of total C, total N, mineral N, N mineralization rate, and microbial biomass C (MBC) and N (MBN) in two agricultural soils (Kamouraska clay and St-Antoine sandy-loam). Two reference treatments were also included, namely, mineral fertilization and unamended soil. Total soil C concentration remained stable over the incubation period, whereas a decrease in total soil N was observed in both soils. In comparison with the unamended soil, the application of PB significantly increased total N, NH4-N, NO3-N, net mineralized N, applied N mineralization rate, and MBC in both soils. In comparison with the application of PB alone, biochar addition increased total C and MBC but decreased NH4-N, NO3-N, net N mineralization, and applied N mineralization rate in both soils. The co-application of biochar and PB1 resulted in the sequestration of mineral N released, which was more pronounced in the Kamouraska clay soil. The co-application of biochar and PB2 resulted in moderate release of mineral N. This study showed that the co-application of biochar and PB can benefit agricultural soils by improving NO3-N retention in agroecosystems while increasing organic matter and promoting microbial biomass.

This review paper encompasses the inclusive approach of lime sludge valorization in construction materials. Research studies based on cement and aggregate replacement by lime sludge concludes that 10–30% lime sludge is gainfully utilized in sustainable concrete and mortar. Additional prospect for lime sludge application in construction material is the production of cement and ceramics. Significant use of lime sludge in combination with supplementary cementitious materials such as silica fume, nanosilica and fly ash is recommended for the production of cement components and ceramics. The recommendations are also suggested in accordance with the outcome of the study.

The paper drying process has the highest level of energy consumption in the pulp and paper production process. Analysis and optimization of the energy system during the paper drying process is critical for improving the energy efficiency of the entire paper mill. In the existing model for the paper drying process, the solution requires accurate boundary conditions such as the air temperature and humidity of the pocket area and the cylinder surface temperature, which are very difficult to obtain in the papermaking process. This can result in significant deviations between the model solution and the actual production process. This paper focuses on the single-tier dryer cylinder-based paper drying process that has been widely used with high-speed papermaking machines in recent years. A mathematical model is proposed based on real-time data. The verification via industrial production demonstrates that the proposed model is reliable for the paper drying process. Based on the simulation results, two optimization operations have been proposed. The energy consumption decreases from 1.51 t steam/t paper to 1.44 t steam/t paper, 4.6% of the steam and 1.26 × 106 RMB can be saved for a medium-scale paper mill with the annual production capacity of 105 t paper.

In the present study, the photodegradation of lignin was studied using TiO2/Polystyrene composite under UV-LED irradiation in a batch-recirculated photoreactor as a supplementary treatment for pulp and paper industries. TiO2/PS composite was synthesized by the solvent-casting method and was characterized by scanning electron microscopy (SEM) and EDX analysis. The 3-level, 3-factor Box-Behnken design was applied to study the effects of main operating parameters and optimization of process circumstances. Besides, COD reduction efficiency, toxicity assays, and reusability were also investigated. The predicted model had R2 and R2adj correlation coefficients of 0.97 and 0.99 respectively, which showed experimental results were very close to the predicted values. Furthermore, under the optimal conditions (reaction time = 72.5, volumetric flow rate = 230 mL/min and lignin = 51.8 mg/L) the lignin degradation efficiency was 93.98%. The maximum COD removal (89%) obtained by 250 mL/min volumetric flow rate and lignin concentration of 50 mg/L after 120 min reaction time. Bioassay using D. Magna exhibited that at the beginning of the process, the toxicity of solution increased but continuously decreasing after then to very low values achieved within 120 min of photodegradation. In addition, the reusability tests demonstrated that the TiO2/PS composite after 5 cycles has a good stability and photocatalytic activity.

Pulp and paper industry is one of the high priority sectors that generates large amount of solid (sludge) and liquid (paper mill effluent) wastes. Making use of this huge quantity of paper mill sludge (PMS) in an environment friendly manner is challenging and cost involving. Similarly the present wastewater treatment strategies based on physical and chemical methods encounter certain serious setbacks including secondary pollution generation with expensive mode of abatement processes. The present study aims at a “waste treats waste” strategy for the bioremediation of paper mill effluent in fluidized bed reactor (FBR) using another waste of the same industry, PMS as immobilizing matrix for Planococcus sp. TRC1, a wastewater bacterial isolate. This study simultaneously explores this isolate for the yellowish orange pigment it produces (2.3 ± 0.2 mg/gm of dry bacterial biomass) and characterizes it as a member of the pharmacologically important carotenoid pigment family via UV-Vis spectrophotometry, TLC, FT-IR and 13C NMR. The antioxidant potential of this pigment was studied by DPPH assay (IC50 = 33 ± 0.4 μg/ml) and H2O2 assay (IC50 = 147.4 ± 2.2 μg/ml). In FBR, the PMS immobilized bacteria showed removal of phenol, lignin, colour and COD from the effluent by 96%, 74%, 81% and 85% respectively after 60hr of treatment. The experimental data on immobilization fitted well with pseudo second-order (R2 = 0.955) and Freundlich adsorption isotherm (R2 = 0.996) models. The alterations in PMS before and after bacterial immobilization, as revealed by SEM and FT-IR, depicted the success of PMS as immobilization matrix. Phytotoxicity (90% seed germination) and mutagenicity studies confirmed that the treated effluent was substantially less toxic than its raw state. This study highlights a novel utilization possibility of PMS in an eco-friendly and economic way as immobilization matrix for Planococcus sp.TRC1 for paper pulp mill effluent treatment along with production of carotenoid pigment from this potential bacterial isolate as value added product.

Pulp and paper mill industry is already known as an extensive water user and hence produces large volume of wastewater. Phytoremediation has merits to offer due to its environmentally friendly, relatively low cost and easy maintenance. This work focused on the performance of a continuous pilot subsurface flow (SSF) system of constructed wetlands in removing chemical oxygen demand (COD) representing organic carbon, colour and suspended solids from recycled pulp and paper mill under 5-day hydraulic retention time (HRT) for 95 days. In this study, there were two tanks based on the SSF system; one tank planted with Malaysian native bulrush (Scirpus grossus) and another tank without plants acting as a control. It was found that the SSF system with S. grossus was much better compared to the SSF control. Throughout the 95-day exposure, the planted SSF system have achieved removals of 66.1, 55.8 and 87.2% for COD, colour and suspended solid (SS), respectively. However, the control SSF system without plants has lower performance for all the three parameters (62.4% COD, 44.4% colour and 84.8% SS), giving evidence that constructed wetlands is an efficient technology to phytoremediate COD, colour and SS from recycled pulp and paper effluent.

In this study, a waste pickling liquor from a steel mill, which is rich in iron and acid, was used as the main raw material to prepare a composite coagulant: polymeric ferric aluminum sulfate chloride (PFASC). The as-prepared PFASC was used, together with PAM, for the tertiary treatment of papermaking wastewater to decrease its COD and Chroma. The Results from FT-IR and XRD of PFASC, supported the conclusion that polymeric ferric aluminum hydroxide hydrates compounds/ complexes are formed in the synthesized PFASC. When applied to a waste water sample from a paper mill, PFASC, together PAM, leads to decreases in COD and Chroma by 65.3% and 71.2%, respectively (initial pH 7.5, 1 ml/L PFASC, 1.0 ppm PAM). The technology has been implemented at a paper mill, and the obtained results are consistent with those from the laboratory.

The pulping industry generates vast amounts of bark residues and wastewater treatment sludges, which are combined and stored for varying periods in stacks, often in the open air, prior to utilization for energy via combustion. In order to optimize the storage strategy, the effects of incorporating sludge into bark on heating value and storage-related environmental impacts were investigated in laboratory and outdoor studies. Biological degradation activity was found to be higher in treatments containing 25% sludge (B75S25) and 50% sludge (B50S50) on a fresh mass basis, in comparison with pure bark (B100). Mean monthly dry mass loss was 2.1% (B100), 3.3% (B75S25), and 3.7% (B50S50) in the laboratory and 2.7%, 4.2%, and 4.8%, respectively, outdoors. Sludge addition was found to maintain degradation activity at low temperatures (+ 3°C). Co-storage of sludge and bark led to loss of energy, mainly due to increased loss of biomass and increased moisture content. Overall, biomass moisture content governed the heating value. Cumulative methane emissions over the storage period were higher from the sludge-containing treatments than from pure bark, but emissions of nitrogen-containing gases (N2O and NH3) were negligible throughout. Sludge addition roughly halved the cumulative chemical oxygen demand (COD) of leachate and minimized its concentration of phosphate-P. However, larger amounts of inorganic elements were released to the percolating water from the sludge-containing treatments. Overall, these results indicate that finding alternative uses for the sludge fraction would be beneficial.

Paper industry wastewater is the significant source of water and soil contamination due to various unknown residual organic pollutants directly discharged into the environment without proper treatment. Therefore, the study has focused on the detection of residual organic pollutants (N-(1,2,2,2-tetrachloroethyl) trimethylacetamide, octadecane, 1-iodo, Oleic acid, trimethylsilyl ester, eicosane; hexadecane, 2-methyl-; octadecane, docosane; tricosane) from paper industry wastewater sources showed endocrine-disrupting compounds and their toxicity. This experiment were carried out the effect of paper mill sludge amendments with garden soil (25%, 50%, 75%, and 100%) and garden soil was utilized as a control in a pot experiment. This study revealed the growth parameters of Triticum aestivum in seeds germination percentage and germination index values decreased with rising in sludge concentration. Further, soil amended with 25% paper industry sludge slightly reduced the growth in root length, shoot length, biomass, photosynthetic and 50% sludge amended soil had variable effects on the root, shoot, and photosynthetic pigment of T. aestivum. Moreover, the toxicity of paper industry wastewater on tubifex-tubifex worms after 48 h of exposure (>50% concentration), worms showed various changes such as movement; haemoglobin content disappeared, cell bursting, and the back of the body became white with body disintegration at the lethal concentrations of paper industry wastewater. This article has revealed that the toxicity of the organic pollutants in the terrestrial and aquatic life due to paper industry wastewater there is needed to treat adequately prior to discharge.

Recovery of phosphorus (P) from wastewater has led to growing public concern considering its scarcity and future availability as well as its detrimental environmental impacts. However, the recovered P is inevitably contaminated with co-existing antibiotics like tetracycline (TC) and sulfamethazine (SMT) which will pose serious risks to the health of human and animals after being spread to the environment. In this study, we propose a novel scheme that can recover P from synthetic wastewater and at the same time degrade the co-existing antibiotics. To achieve such a goal, a series of biochar (BC) were prepared from calcination of waste sludge and were used both as the adsorbent for P recovery and as the catalyst for peroxymonosulfate (PMS) activation and antibiotic degradation. Results showed that the sludge source (i.e. Sm: municipal sludge, Sp: paper mill sludge), calcination atmosphere (i.e. air-deficient, N2, vacuum) and temperature (i.e. 600 and 800 °C) exhibited significant influence on P adsorption capacity. Generally, the BC calcined in N2 showed better P uptake, and increase of calcination temperature from 600 °C to 800 °C could further improve P uptake. Though BCp-N-600 (prepared from Sp in N2 at 600 °C) showed faster and higher P uptake (56.3 mg/g) than its counterpart BCm-N-600 (33.2 mg/g), BCm-N-600 showed stronger catalytic activity and more stable performance in the complex pollutant system (P + SMT). It was proposed that P was recovered primarily through the chemisorption and precipitation mechanism, while SMT was nearly completely degraded primarily by the ROS generated from PMS activation.

Lignocellulosic biomass, such as corn stover, pulp and paper mill waste, and switchgrass, is a readily available feedstock for the production of monomeric sugars and platform chemicals that can then be transformed into valuable organic molecules. However, efficiently fractionating lignocellulosic biomass is difficult due to the recalcitrance of lignin at mild reaction conditions and the reactive sugars/platform chemicals at more severe conditions. Biphasic systems present a possible solution to creating an economically viable biomass upgrading process since sugars prefer the aqueous phase while the lignin and furans partition to the organic phase. This review focuses on recent work to fractionate biomass using biphasic reactions as well as monophasic reactions that use biphasic systems to separate products. The use of different biphasic media, heterogeneous and homogeneous catalysts, and reaction conditions are reviewed and trends in isolating the fractions found in biomass are discussed.

To evaluate the effect of brown-rot fungi Oligoporus placenta and earthworm Eisenia fetida on decomposition of paper mill sludge, the paper mill sludge was mixed with cow dung in 0, 25, 50, 75, and 100% proportions and changes in physicochemical quality of waste mixtures was carried out for 28 days. All waste mixtures were treated with: Setup-I (E. fetida), Setup-II (O. placenta) and, Setup-III (E. fetida + O. placenta). A decrease in total organic carbon, C/N ratio and cellulose but an increase in total kjeldhal nitrogen, total phosphorus, total potassium and pH was recorded. The paper mill sludge in 50–75% proportion in feedstock showed the better results and rate of mineralisation were in order: Setup-III > Setup-I > Setup-II. The proportion of CD has direct role in waste mineralisation. The microbial population (bacterial, fungal and actinomycetes) and earthworm biomass were also high in Setup-III, suggesting the influence of brown-rot fungi on paper mill sludge humification. Results indicate that fungal inoculate in vermicomposting was effective in decomposing cellulose-rich industrial sludge.

The non-process-elements (NPE's) in the pulp and paper production, in particular chloride (Cl−) and potassium (K+), eventually accumulate in a sodium sulfate recovery cycle of a paper plant, especially on boiler fly ashes (flue gas cleaning). This accumulation often leads to fouling and corrosion. Thus, in order to reduce such problems, a leaching unit is typically integrated aiming to remove Cl− and K+ and recover sodium sulfate (Na2SO4) from boiler fly ashes. In this context, this research is focused on investigating the effects of temperature, ash concentration and pH on the separation efficiency (Cl− and K+ removal and Na2SO4 recovery) of recovery boiler fly ashes using design of experiments in a devised laboratory setup. As expected from the literature, the results obtained reveals that concentration has the most significant effect on the response variables followed by temperature; whereas pH, not mentioned in this application so far, also has a significant effect. The optimum operating condition, which yields 84 wt% of Na2SO4 recovery and 97 wt% of Cl− and K+ removal, is achieved at 60 °C, 50 wt% of ash and pH 9.0. For practical applications, this optimal condition reduces the accumulation of NPE‘s and mitigates the risks of fouling and corrosion.

In this study, a mathematical model has been developed for sustainable inventory, in which the effects of environmental factors on social factors, have been investigated. To this end, first, we revised Economic Order Quantity (EOQ) model by adding income from waste sales to this model. Next, considering the emission of sulfur oxides (SOx), nitrogen oxides (NOx) gases, Biochemical Oxygen Demand (BOD) and chemical oxygen demand (COD) indicators in waste water as a measure of water organic pollutants, we proposed a Green Economic Order Quantity (GEOQ) model. Then in order to examine interdependency between environmental aspects and social aspects, we introduced the sustainable model by adding environmental ergonomics in the terms of the effect of SO2 emission on human health. Since the structure of the model consists of nonlinear objective function and linear constraints, the model could be solved based on an exact nonlinear constrained solution method. Finally, we examined the effectiveness of the proposed model demonstrated in a real case study of pulp and paper mill. Validation of the model was done by comparing the cost function of the proposed model with the pure economic model and the actual data. The results of study showed that proposed sustainable model plays a significant role in determining the order quantity and reduction of cost function, sulfur oxides (SOx) and nitrogen oxides (NOx) emissions, and Biochemical Oxygen Demand (BOD) and chemical oxygen demand (COD) in waste water.

Dewatering and handling of pulp and paper mill sludge is challenging and often comprises more than half of the overall wastewater treatment costs at a mill. Primary sludge is usually more dewaterable than biosludge (waste activated sludge), and the ratio between both types of sludge largely determines the dewaterability of the sludge mix. This study has quantified the benefits of adding primary sludge to biosludge to enhance the dewaterability in terms of cake solids and filtrate/pressate solids content. Furthermore, the effects of the particle size distribution and the monovalent to divalent cation ratio of the various types of sludge were investigated. Biosludge and three types of primary sludge from a Canadian pulp and paper mill were mixed at various ratios and tested for dewaterability using a Crown Press®, a bench-scale device which simulates industrial belt press dewatering. Results show that after addition of primary sludge at up to 40% mass proportion (dry solids basis) the dewatered cake solids content increased substantially, from 10.4% to 18.7–19.9%, depending on the type of primary sludge added. Further addition of primary sludge led to comparably only small improvements. Primary sludge addition also resulted in decreased total suspended solids (TSS) concentrations in the combined gravity filtrate / Crown Press pressate. Primary sludge content of only 10% in the sludge mix was sufficient to decrease the TSS concentration from 1.8 g/L to 0.2 – 0.4 g/L. The study shows that only less than half of the sludge mix needs to consist of primary sludge, in order to achieve adequate dewaterability. This opens up the possibility of retaining more primary fiber within the pulping process, without compromising downstream sludge dewatering.

Anaerobic treatment of sedimented fibers collected from bottom of a bay that had been receiving pulp and paper mill wastewater for about 70 years were studied for the first time in semi-continuously fed continuously stirred tank reactors (CSTR). Anaerobic treatment of the fiber sediment was shown to be feasible, without dilution and with nitrogen and buffer supplement, at organic loading rates (OLR) up to 2.5 kg VS/m3d and hydraulic retention times (HRT) of 60 d resulting in methane yields of 201 ± 18 L CH4/kg VS. Co-digestion of sedimented fiber with sewage sludge at an OLR of 1.5 kg VS/m3d and HRT of 20 d resulted in a methane production of 246 ± 10 L CH4/kg VS. The techno-economic feasibility of mono and co-digestion process together with several case dependent factors such as maximum operable OLR, digestate utilization needs to be evaluated before making further conclusions for larger scale remediation applications. acceptedVersion

In the present study, the extraction of polyester like polyhydroxyalkanoates (PHAs) from enzymes extracted sludge was investigated by varying extraction time and chloroform – sodium hypochlorite dosage. Maximum of 874 mg/g of PHAs was achieved at an optimum extraction time of 120 min and chloroform – sodium hypochlorite dosage of 30% v/v. The characteristics of derived PHAs were examined using Fourier transform infrared (FTIR) spectroscopy and Nuclear magnetic resonance (1H NMR) spectroscopy. Then, the effect of derived PHAs dosage on biomethane production from pulp and paper mill secondary clarifier (PPSC) sludge was studied. Higher amount of biomethane production was observed to be 174 L/(kg VS) at 35 mg of PHAs dosage when compared to other dosage. To further enhance biomethane production, disperser pretreatment method was carried out by optimization of specific energy. At optimum specific energy of 8547 kJ/kg TS, the maximum solubilization rate and suspended solids (SS) reduction were found respectively to be 19% and 15.8%. Then, biomethane assay was conducted on disperser pretreated sludge, disperser pretreated sludge with optimized PHAs dosage (35 mg) and control sludge. Among these, disperser mediated PHAs method exhibited maximal biomethane production and was observed to be 267 L/(kg VS). Hence, PHAs based sludge treatment method can be implemented in sludge management studies by retrieval of value added product and PHAs canbe used to enhance biomethane production sustainably.

The present study demonstrates the vermistabilization of paper mill wastewater sludge (PMS) spiked with cow dung (CD) employing indigenous epigeic earthworm Perionyx excavatus Perrier. A total of six treatments were prepared along with a positive control (PC) and negative control (NC). Twenty earthworms were released into each treatment including PC and NC without earthworms. The different proportions viz., T1 (CD – 100%), T2 (PMS:CD – 1:3), T3 (PMS:CD – 1:2), T4 (PMS:CD – 1:1), T5 (PMS:CD – 3:1), T6 (PMS:CD – 2:1), PC (PMS – 100%) and NC (PMS – 100%) and changes in chemical parameters and microbial properties were recorded during the course of 60 days. Vermistabilization caused a significant decrease in the level of heavy metals: Cd (2.9–27.8%), Cu (0.22–42.3%), Pb (1.3–56.3%) and Cr (0.8–46.2%). The bioconcentration factor (BCFs) was also calculated and great amount of heavy metals accumulated in their body (mg kg−1) that ranged from 0.31 ± 0.003–0.45 ± 0.007 for Cd, 0.12 ± 0.005–0.24 ± 0.003 for Cu, 0.15 ± 0.005–0.31 ± 0.006 for Pb and 0.29 ± 0.007–0.56 ± 0.001 mg kg−1 for Cr, accumulation of heavy metals are in the order: Cr > Cd > Pb > Cu. The physicochemical parameters of earthworm treated substrate such as electrical conductivity, total nitrogen, total phosphorus and total potassium were significantly increased; whereas, pH, total organic carbon, C:N ratio (carbon: nitrogen) and C:P ratio (carbon: phosphorus) were reduced after 60 days of vermistabilization. The vermistabilized materials also had a higher population of bacteria (98.90 ± 0.30 CFU × 106 g−1), fungi (43.75 ± 0.55 CFU × 103 g−1) and actinomycetes (67.65 ± 0.45 CFU × 105 g−1) than initial mixtures. Moreover, several histopathological changes were observed in earthworm tissues viz., disintegration of cells, irregular surface of epidermis, cellular debris, irregular cellular compartmentation, and oval-shaped nucleus. Higher level of histopathological abnormalities was recorded in PC (PMS-100%) while none were detected in lower concentrations of PMS. Furthermore, the study concludes that the paper mill sludge in a mixture of cow dung (1:1 ratio) can be a useful proposition for utilizing this hazardous waste through the adoption of vermitechnology.

In this work, an eco-friendly solution for the remediation of wastewater generated in the lignin recovery process from eco-industrial paper mill has been proposed in their way towards a more circular economy strategy. Thus, the application of the electro-Fenton process for the degradation of the non-recovered lignin and other organic compounds form a scarcely studied acid black liquor waste (ABLW) was successfully performed. This treatment was able to operate in a range of COD loads (0.5–19.5 mg O2·L–1) showing high degradation values of the ABLW determined by the abatement of color, total phenolic content and COD. Then, the optimization of the working conditions for the design of a sustainable treatment system with optimum efficiency was carried out using a response surface methodology. The experiment carried out in the calculated optimal conditions for the electro-Fenton degradation process (current intensity 132.5 mA, catalyst dosage of 0.10 mM, and temperature 40 °C) showed a COD removal of 74.82% and current efficiency 77.79%, close to the theoretical value predicted by the model 73.12% and 77.06%, respectively. In addition, the identification of the final products permitted to confirm the mineralization efficiency.

Primary and secondary sludges originating from kraft pulp mill effluent treatment plants represent an environmental challenge. Their final disposal mainly includes landfill or burning in the mill's biomass boiler. Seeking energy self-sufficiency and better environmental outcomes, the pulp industry is looking to develop new waste management strategies. Biogas production is a millennial technology already applied in many fields, but still behind in terms of pulp and paper mill sludges. Due to the high moisture content of sludge, anaerobic digestion shows great potential. This paper aimed to study biogas production using kraft pulp mill primary and secondary sludges under thermophilic conditions, coupling laboratory experiments with mathematical modeling. Methane production was estimated through the Biochemical Methane Potential (BMP). The Process Simulation Model developed by Rajendran et al. [1] was calibrated for kraft pulp mill sludge based on the BMP results. Cumulative methane production from the secondary sludge reached 46.9 NmL CH4/g VS in 30 days. In addition, the Rajendran et al. [1] model was shown to be suitable for simulating the methane yield from bleached kraft pulp mill secondary sludge after minor adjustments. The energy balance showed that the anaerobic digestion process under thermophilic condition for kraft pulp mill secondary sludge still is not feasible on large scale, since the heat produced by biogas was smaller than the heat demanded for heating the reactors.

Primary paper mill sludge (PPMS) is the major waste expelled from the pulp and paper industries contributing soil and water pollution through the recalcitrant organic and inorganic constituents. These pollutants can, however, be transformed into a high-value soil ameliorating material with nominal investment and time. Current study therefore evaluated the potential of rotary drum composting PPMS for 20 days to delineate an environmentally sustainable option. Five trials with proportions of PPMS, cow dung and saw dust: Trial 1 (10:0:0), Trial 2 (8:1:1), Trial 3 (7:2:1), Trial 4 (6:3:1) and Trial 5 (5:4:1) were performed for evaluation of degrading and nutritive ability along with the fate of pollutants for total mass of 150 kg. Trial 4 exhibited highest metabolic activity contributing higher temperature evolution and longer thermophilic phase (10 days) owing to optimum addition of innoculum and nitrogen through the cattle manure. Moreover, degradation of 16.8% organic matter was also best achieved in Trial 4 following up first-order kinetics. Furthermore, BOD, COD and C/N ratio also explains degradation to be maximum in trial 4 (6:3:1) with reduction of 59.3%, 60.1% and C/N ratio from 55.1 to 18 respectively, proving to be the essential determining factors. Phosphorus availability increased by around 67% in trial 4. PPMS can be thus transformed into a potential valued added product and safe for subsequent land application.

Management of industrial sludge is a big challenge for developing countries. Composting is an economical and viable option to manage and treat an industrial sludge. However, efficient compost production requires nature of materials involved, process understanding and physics behind the process. We investigated the physical parameters during composting of solid pulp and paper mill sludge in 550 L rotary drum composter. Variation in physical parameters such as bulk density, volatile solids, moisture content, free air space, void ratio, ash content and particle density were analyzed over the period of composting. Bulk density was observed increasing, whereas free air space was showed declining trend and observed 52% in end compost. The particle density was observed to be increasing from 610 to 680 kg m−3. End compost was analyzed for nutritional parameters and seen to be increasing over the period of composting. A strong relationship was found between various physical parameters. Pearson’s correlation coefficient matrix was formed between free air space, bulk density, moisture content and particle density.

The pulp and paper industry, one of Canada’s largest and most important industries, produces many by-products, some of which are used to produce electricity and steam for mill operations; however, the by-products are not used economically. The industry has been facing financial challenges and, therefore, an appropriate means of converting by-products to value-added products is highly desired. In this study, we explore nine pathways for the conversion of black liquor, the major by-product of the industry, to different value-added final products. These include steam, electricity, dimethyl ether, Fischer-Tropsch liquids, mixed alcohols, methanol, acetone, butanol, ethanol, and lignin. The most economical conversion pathway is selected based on the internal rate of return (IRR) calculated through a techno-economic assessment. Lignin production through the fractionation of black liquor is the most attractive scenario. Sensitivity and uncertainty analyses were performed on the IRR for the lignin production scenario to evaluate the effect of different parameters on overall performance and assess the accuracy of the results. The sensitivity analysis shows that lignin price and operating costs are the most influential parameters on IRR. This study offers insights into options of revenue generation for the pulp and paper industry through the innovative use of its by-products.

While many studies have shown that pulp mill effluents can affect ovarian physiology in fish, far fewer studies have considered the effects in males. We conducted a lab study to examine the effects of effluent from a Brazilian pulp and paper mill on hepatic and testicular morphology and various aspects of testicular physiology in the zebrafish Danio rerio. Males were exposed to lab water (control) or 4% effluent for 14 days. Effluent exposure did not affect testis size as measured by the gonadosomatic index, but contributed to morphological changes in the seminiferous tubules. The number of cysts with histopathological changes was elevated in effluent-exposed fish and the number of cysts containing spermatids was significantly reduced. The testis of effluent exposed fish had reduced levels of lactate, elevated lactate dehydrogenase activity, increased levels of reactive oxygen species and reduced levels of phosphorylated P38 mitogen-activated protein kinase (pP38 MAPK). Separate studies showed that the addition of lactate to testicular tissue incubated in vitro increased the activation of P38 MAPK. Effluent exposure also increased vacuolization, necrosis, apoptosis, hyperemia, and fat infiltration of the hepatocytes. Collectively, we provide evidence of short term effects of pulp mill effluent on testicular and hepatic physiology and biochemistry in the zebrafish.

The pulp and paper industry produces about 300–350 million tons of paper mill sludge (PMS) annually and majority is disposed of by landfill. PMS contains up to 75% carbohydrates. In this study, PMS was treated by de-ashing, fiber regeneration and enzymatic hydrolysis. The PMS hydrolysate was used for butyric acid production by Clostridium tyrobutyricum B-67062/RPT 4213. We reported that 8.52 and 8.35 gL−1 butyric acid was produced from 4 L batch fermentation in MRS and RCM4 medium respectively. Moreover, nearly 7 gL−1 butyric acid was produced by using PMS hydrolysates from two different mills when combined with a fraction of MRS, and over 6 gL−1 butyric acid was produced from hydrolysate combined with a fraction of RCM4 medium. This study suggested that beside agricultural lignocellulosic biomass feedstocks, low valued waste materials from the pulp and paper industries could also be used for the sustainable production of butyric acid.

Energy efficient cultivation is the major bottleneck for microalgal biomass production on a large scale and considered very difficult to attain at northern latitudes. In this study an unconventional method for industrial microalgae cultivation for bio-oil production using pulp and paper mill waste resources while harvesting only once a year was performed, mainly in order to investigate the energy efficiency of the process. Algae were cultivated for three months in 2014 in covered pond systems with access to flue gas and waste heat from the industry, and the biomass was recovered as thick sediment sludge after dewatering. The cultivation systems, designed to manage the waste resources, reached a promising photosynthetic efficiency of at most 1.1%, a net energy ratio (NER) of 0.25, and a projected year-round energy biomass yield per area 5.2 times higher than corresponding rapeseed production at the location. Thus, microalgae cultivation was, for the first time, proven energy efficient in a cold continental climate. Energy-rich indigenous communities quickly out-competed the oleaginous monocultures used for inoculation. The recovered biomass had higher heating values of 20–23 MJ kg− 1 and contained 14–19% oil dominated by C16 followed by C18 fatty acids. The cultivation season at 59°15′N, 14°18′E was projected to be efficient for 10 months and waste heat drying of the biomass is suggested for two winter months. The technique is proposed for carbon sequestering and energy storage in the form of microalgal sludge or dry matter for later conversion into biochemicals.

The economic impact of coproduction of renewable fuels with platform chemicals is determined by assessing thermal deoxygenation (TDO) pathway based biorefineries with two distinct product suites: (1) fuel and furfural (a platform chemical) and (2) fuel and levulinic acid (a platform chemical). Greenfield and brownfield plant site scenarios are considered. Additionally, the economic viability of producing activated carbon from biochar, rather than burning it to produce energy, is assessed. The biorefinery in which wood is converted using the TDO pathway to furfural, renewable fuel, and biochar is found to be a product-driven biorefinery. The production of renewable fuel along with levulinic acid from recycled cardboard via the TDO pathway is determined to be an energy-driven biorefinery. The minimum selling price (MSP) of TDO oil produced in product-driven and energy-driven greenfield biorefineries are estimated at US$17 and US$18 per GJ or US$2.78 and US$2.92 per gallon of gasoline equivalent (GGE), respectively. It is found that capital investment for the product-driven and energy-driven biorefineries can be reduced by 23–27% through integrating the TDO process into an existing pulp and paper facility (brownfield site), provided the infrastructure and assets of pulp and paper mill are well maintained. It has been learned that the synergy arising through co-production of chemicals with fuels and vice versa can facilitate the sustainable production of both renewable fuels as well as platform chemicals. Moreover, there is a need for the development of new less energy intensive separation processes for purifying bio-products.

In this study, biochar, a carbonaceous solid material produced from three different waste sources (poultry litter, rice husk and pulp and paper mill sludge) was utilized to replace cement content up to 1% of total volume and the effect of individual biochar mixed with cement on the mechanical properties of concrete was investigated through different characterization techniques. A total of 168 samples were prepared for mechanical testing of biochar added concrete composites. The results showed that pulp and paper mill sludge biochar at 0.1% replacement of total volume resulted in compressive strength close to the control specimen than the rest of the biochar added composites. However, rice husk biochar at 0.1% slightly improved the splitting tensile strength with pulp and papermill sludge biochar produced comparable values. Biochar significantly improved the flexural strength of concrete in which poultry litter and rice husk biochar at 0.1% produced optimum results with 20% increment than control specimens. Based on the findings, we conclude that biochar has the potential to improve the concrete properties while replacing the cement in minor fractions in conventional concrete applications.

Contamination and associated risks posed by cadmium (Cd) and chromium (Cr) were characterized in the soils being continuously exposed by paper mill waste discharge in Assam, India. Soil samples from 20 (S-1 to S-20) sites surrounding a paper mill were analyzed by sequential extraction technique for Cd and Cr to assess the potential mobility and bioavailability of these heavy metals in the soils. Cadmium was mostly found in its carbonate fraction (37.14%) whereas; Cr was mostly available in Fe-Mn oxide bound fraction (34.72%). Relatively low amounts of Cd and Cr were associated with the water soluble fractions. The pollution load index (P i) values of Cd exceeded the maximum permissible limit i.e. 1 in all the sites but, for Cr it exceeded in all sites but S-7, S-13 and S-16. The mobility factor values ranged from 47.4% to 87.1% for Cd and 12.8–67.2% for Cr. High mobility factor values represent relatively higher biological availability in the soil samples and thus could pose environmental threats in the area surrounding the paper mill. The high values of other contamination factors, viz. individual and global contamination factors, potential ecological risk factor, ecological risk index and geo-accumulation index indicated that the studied area was widely polluted by Cd and Cr as a result of the effluents discharged from the paper mill.

The purpose of this study is to investigate influence of calcination and cooling conditions on pozzolanic reactivity of waste paper sludge. Calcined paper sludge (CPS) is prepared by different temperatures of calcination, duration of calcination and cooling methods. Pozzolanic activity of CPS was investigated by using API (Assessed Pozzolanic Activity Index) and SAI (Strength Activity Index) in accordance with ASTM C618 -17 (KS L 5405) and consumption of Ca(OH)2 hydrate in mortars with CPS in detail, and compared to that of commercial fly ash (FA) and blast furnace slag (BFS) used in the concrete industry. Results revealed CPS produced from waste paper sludge had excellent pozzolanic activity compared with commercial pozzolanic admixtures such as FA or BFS. Their pozzolanic activity was most excellent in calcination temperature of 700 °C, calcination duration of 2 h and cooling method of water quenching. SAI (%) of mortar with CPS produced under optimal conditions was 96% at 28 days of age, and satisfied the quality of fly ash (Class F) as specified in ASTM C618 -17 (KS L 5405). There was linear relation between API (%) and SAI (%) of mortars with CPS, and the correlation coefficient was relatively good as 0.8 at 28 days of age. The API method is recommended as rapid and appropriate evaluation of the pozzolanic activity of the CPS.

Industrial productivity is often judged solely by the primary product's marketability, while opportunities for secondary products derived from process by-products are often overlooked. In paper mills, large volumes of moisture-rich paper mill residuals (cellulose sludge) are produced, for which commercial use is currently difficult. Port Hawkesbury Paper LP, Port Hawkesbury, Nova Scotia, produces over 7 t/hr of waste sludge with a seasonally-dependent dryness ranging from 25 to 38% (w/w). Various chemical or mechanical dewatering options exist; however, knowledge of the unique sludge composition and properties is essential to predicting how the product will react under each method. Sonication, Fournier rotary press technology, freeze/thaw cycling, and gravity drying were among the dewatering opportunities briefly explored outside of the chosen method, acidification. Notably, many industries utilizing dewatering technologies may not be producing value-added by-products, while geographic and climatic placement may limit processes which are possible for others. In the present study examining enhanced end-use value, further dewatering occurred through a comparative in situ experiment contrasting sulfuric acid and ferric sulfate acidification (direct acid injection into sludge). While both proton donors acidified the sludge and decreased moisture content, sulfuric acid was the more cost-effective option, yielding an ∼4% increase in dryness, with commensurate economic and environmental benefits.

Aeration, as a process in pulp and paper wastewater treatment, uses the greatest share of the energy. Therefore, if the energy efficiency of the treatment has to be improved, the focus must be on aeration. A key finding from the trials conducted for this paper, with effluent from a paper and pulp mill, was that the oxygen transfer coefficient could be doubled and the chemical oxygen demand could be decreased by 25%, if the effluent was pre-treated with 30 mg/l of aluminium coagulant (equivalent to 9.4 tonnes per day of AVR to 20000 cubic metres of effluent). Decrease in oxygen requirement implies decreases in aeration energy use. Pulp and paper mill effluents are not as biodegradable as municipal sewage, and the improvement in oxygen transfer properties of the effluent will have a positive influence over a longer period of time in the biological treatment. If the sludge is digested anaerobically, pre-treatment will also result in doubling the potential for methane generation. A holistic analysis of modifications to processes entails a study of the economic and environmental consequences as well. While the economic aspect is beyond the scope of this paper, only the net global warming as an environmental impact category has been studied, by taking recourse to specific emission coefficients. Of the four dosages of ferric aluminium sulphate considered in this analysis, the net greenhouse gas emissions are the least – 426 kg carbon dioxide equivalent per day when the daily consumption is 9.4 tonnes.

This study focuses on the pre-treatment of paper mill sludge ash (PMSA) as a by-product of paper milling industry that contains high amount of calcium, yet low in silica. The presence of high calcium content in geopolymer system will accelerate the setting time of fresh geopolymer and may disrupt the development of its mechanical strength. Therefore, in this study, the refinement of PMSA properties was conducted by treating raw PMSA in hydrochloric acid solution with different molarities of 0.5 M, 1.0 M and 1.5 M. The pre-treatment process was mainly purposed to decrease the amount of calcium and other impurities through leaching mechanism. Characterization of raw materials and pre-treated PMSA was done based on ICPMS and XRF analysis for its leachate and oxide analysis, respectively, while the effect of pre-treated PMSA on geopolymer properties was conducted by adding the pre-treated ash as a replacement material for fly ash at various percentages of replacement (5%, 10%, and 15%). Based on the experimental results, 1.5 M hydrochloric acid solution (HCl) was determined as the optimum concentration due to its ability in removing higher amount of calcium from the ash, yet still able to increase the amount of silica. Testing on the hardened properties of geopolymer specimen also showed the deceleration of fresh fly ash based geopolymer and produced a more workable fresh geopolymer. Higher workability has led to a denser and more compact specimen, which contributed to the higher mechanical strength of hardened specimen, particularly in 5% pre-treated PMSA specimen. Therefore, the use of PMSA as an alternative source material for fly ash based geopolymer has presented a favourable potency, particularly after the pre-treatment process with HCl.

Black liquor is a high energy content by-product of paper mill industries which can be processed to generate energy and help in energy sustainability. In this study, experimental analysis were carried out to find various properties of black liquor and characterization of its bio-oil and bio-char obtained through pyrolysis of dried black liquor solids. It was observed from the present study that the temperature has a significant effect on the distribution of products yields. The bio-oil yield was found to be maximum at 500°C temperature with the heating rate of 40°C/min. The bio-oil obtained from Dry black liquor solids (DBLS) has a calorific value of the 29.86 MJ/kg. Chemical composition of the bio-oils was investigated by using FTIR and 1H NMR analysis. Bio-chars obtained as by-product were also analysed by using SEM-EDX, FTIR and XRD. It was found that the bio char obtained were basic in nature. Hence, it may be used as a potential liming agent for reclamation of acidic soil.

Fate and health risks associated with persistent organic pollutants present in water effluents are one of the major environmental challenges of this century. In this paper, the electrochemical advanced oxidation process electrochemical oxidation is reviewed for its performance over the treatment of actual industrial and urban effluents. The electrochemical treatment of industrial effluents resulting from textile dyeing, petrochemical, paper mill, tannery industry as well as the treatment of domestic and urban wastewaters are discussed. Furthermore, the combination of electrochemical oxidation with other water treatment technologies as pre-treatment, post-treatment, and integrated treatment is also examined.

Causticizing process of pulp and paper mills, is highly energy intensive and environmentally unsafe. We report environmental friendly electro-electrodialysis (EED) process using in-house prepared cation exchange membranes (CEMs) for NaOH production from green liquor solution (GLS) of agro-based paper mills. Different composite CEMs with varied composition of sulfonated graphene oxide (SGO) incorporated sulfonated poly (ether ether ketone) (SPK) were synthesized. Best optimized CEM (SPK-3 with 3.0 wt% SGO loading) exhibited 1.75 mmol·g−1 cation exchange capacity, 32.01% water uptake, 11.41% swelling ratio, conductivity 0.037 S·cm−1, and 0.97 counter-ion transport number with high alkaline and thermo-mechanical stabilities. Industrial GLS was used for NaOH production by EED at 60 mA·cm−2current density. Optimized SPK-3 membrane produced 1.17 mol·L−1 of NaOH with 61.4% current efficiency (η), and 2.58 kW·h·kg−1 energy consumption (EC) during 4 h of EED process. Under similar operating conditions, pristine (SPK), and commercial CEM (FKB-PK-130), showed inferior performance. Longevity of SPK-3 CEM was assessed with industrial GLS for fifty cycles of EED experiments 4 h duration each. Reported results are promising for sustainable NaOH production from industrial GLS of pulp and paper mills, and provide a resourceful alternate for industrial waste.

Pulp and paper mills are known large emitters of air pollution creating potential environmental challenges and human health impacts. This study assesses air pollution and associated impacts from connected pulp and paper facilities which operate in Edmundston, New Brunswick, Canada, and Madawaska, Maine, United States (US). Despite operating within two regulatory jurisdictions on both sides of the international border (in Canada and the US), the mills have exceeded their approvals to operate and national air quality regulations multiple times between 2010 and 2017. Previous studies have linked many types of cancer as well as respiratory and cardiovascular diseases to air pollution emitted by pulp and paper mills, making this an important regional issue in Canada and the US. While potential environmental and community impacts are likely similar on both sides of the international border, emissions from each side are not reported on the other, and few studies have been conducted on either side. Historic and ongoing lack of local epidemiological health and environmental impact studies and recommendations for improvements to mill operations to improve environmental and human health are presented.

The use of membranes in integrated water systems has garnered increasing attention in paper mills operating with virgin fibres, with documented closed water loops in industry. However, limited research exists on the performance of ultrafiltration (UF) in mills operating with 100% recycled fibres (RCF) and closed water systems, as these result in the introduction and accumulation of insoluble contaminants in the effluent. This study investigated the effect of transmembrane pressure (TMP) and feed organic load on the flux, types of fouling, and organic separation with UF membranes in a recycled paper mill using 100% RCF. The high feed organic load caused inevitable fouling, limiting the highest achievable flux. However, the TMP could be manipulated to improve on or exacerbate the process performance, within the range that was set as a result of the feed's characteristics. Low TMP (1.35 bar) generated the highest permeability and chemical oxygen demand removal, while higher TMPs produced higher fluxes and recoveries. The process was characterised by high initial fluxes, followed by cake formation, which dominated, and pore blockage. The excess cake formation induced cake filtration. This study shows the potential of UF membranes to be used as pre-treatment in filtering the process water in a recycled paper mill operating with 100% RCF, a critical step forward in implementing an integrated water system, and eventually closing the water loop.

Pulp and paper mill sludge (PPMS) is applied on agricultural soils as an organic fertilizer. Although it is well accepted that land application of PPMS has benefits for soils and crops, information on PPMS-induced soil N2O emissions is still limited. We assessed the effect of substituting mineral N fertilizer for PPMS on soil N2O emissions after a single application at planting on a clay loam cropped to wheat (Triticum aestivum L.) over two snow-free seasons in eastern Canada. Fertilization treatments consisted of 0, 25, 50, 75, and 100% of crop N requirements derived from N supplied by PPMS, the remaining N being supplied as urea-N. Soil CO2 and CH4 emissions were also measured and not affected by the fertilizer addition; a slight CH4 oxidation occurred. Area-based N2O emissions from PPMS fertilization (4.4 to 12.1 kg N2O-N ha−1) were similar or higher than from urea alone (3.4 and 6.2 kg N2O-N ha−1). Although crop yields were not affected by the type of fertilizer, yield-based N2O emissions, N uptake efficiency and N surplus (applied N minus aboveground N uptake in crop biomass) indicated that N availability from the mineral fertilizer was higher than from PPMS for the wheat crop. However, treatments with PPMS had fertilizer-induced N2O emission factors (FIEF, applied N lost as N2O-N; 0.8 to 3.1%) similar to urea alone (−0.3 and 4.5%). Although substituting urea-N with PPMS in agricultural fields might reduce N2O emissions under moderate soil moisture conditions, PPMS land application produced greater N2O emissions under high soil moisture conditions. Further research on a variety of agricultural practices is needed before concluding that including PPMS in the fertilization plan could result in a global GHG abatement as compared to mineral fertilizers under the cool climate of eastern Canada.

Currently, primary treatment and secondary biological treatment are the main steps for the treatment of wastewater generated from pulp and paper processes. However, in many cases, in particular, in China, due to a very low COD regulation for discharge, the secondarily treated wastewater would have to be further treated. In this short communication, we present a process concept of immobilizing white rot fungi to corn cob for tertiary treatment of secondarily treated wastewater. As an agricultural residue, carbohydrate-rich corn cob can serve as the support for fungi, allowing for continuous wastewater treatment operations. The role of corn cob as a carbon source can facilitate fungal incubation. Enrichment of pollutants by corn cob could also be possible, which is definitely favorable for enhancing fungi-pollutants interactions. This concept may potentially be combined with existing wastewater treatment technologies to meet ever-demanding environmental target for discharging effluent from manufacturing processes, including pulp and paper mills.

Different heating processes were applied to pretreat the pulp and paper mill sludge to enhance the hydrolysis stage. Hot air oven, autoclave, microwave and water bath were used for comparison. Chemical analyses exposed that all the pretreatment methods have shown improvement in solubilisation of organic matter. Among the pretreatments studied, heat transfer through hot air (80 °C for 90 min) mode had the highest impact on sludge solubilisation. There was an increase in cellulose (P = 0.0096), acid soluble (P = 0.0053) and insoluble lignin (P = 0.0012), but decrease in hemicellulose (P = 0.0009) content after pretreatment. The XRD and FT-IR spectroscopic characterisation shows the development of aliphatic, unsaturated and carbonyl carbon functionalities in the pretreated samples at higher severities. FESEM picture also confirms the change in structure after pretreatment. Thus, pretreatments contribute to disruption of the lignocellulosic structure making the cellulose easily accessible to acidogenic microorganisms.

Paper mill wastewater is a complex mixture of different organometallic pollutants with alkaline pH and toxicity to aquatic organisms. This study investigates major physicochemical parameters such as BOD (814.0 ± 2.84), COD (2289.0 ± 3.54), TDS (4128.0 ± 5.21), dissolved solid (3520.0 ± 4.85), suspended solids (608.0 ± 1.53), lignin (628 ± 2.24) and heavy metals along with organometallic pollutants from paper mill wastewater detected by gas chromatography and mass spectrophotometer technique. The organometallic pollutants such as decane, 2,9-dimethyl, eicosane, 2-bromotetradecane, 1,2-dihydro-1,4-diphenylphthalazine, benzene acetic acid, 4-[(trimethylsilyl)oxy]-, trimethylsilyl ester, and docosane were detected via. gas chromatography and mass spectrophotometry (GC–MS). These pollutants are highly toxic and cause significant adverse effects on aquatic organisms. The toxic effects of organometallic pollutants were tested on Heteropneustes fossilis (Stinging catfish) and Tubifex-tubifex (sludge worm) using different concentrations of wastewater (25%, 50%, 75%, and 100%). Due to wastewater exposure Heteropneustes fossilis, toxic effects were observed, showing notable changes in the secondary lamellae (SL); primary lamellae (PL); mucous cell (MC); epithelial cell (EC); chloride cell (CHC). In Tubifex tubifex, minimum toxic effects were noted at the concentration of less than 25% up to 24 h of exposure and maximum at 48 h of exposure at 50% of the wastewater concentration. After 24 h wastewater exposure, the hemoglobin content was decreased, the body’s rear part became white, and body disintegration was observed in worms. In conclusion, the present study investigates that paper mill wastewater is toxic to the aquatic ecosystem and must be treated and assessed before discharge.

A hybrid treatment system of multimedia–sequencing batch biofilm reactor (MM-SBBR; B) and three control bioreactors (C, D, E) processing synthetic wastewater containing pentachlorophenol (PCP), were used to study the effectiveness of PCP removal and the impact of high-levels of PCP (100 mg L−1) on bacterial community compositions. Another MM-SBBR (A) treating real effluent of the recycled paper mill industry containing PCP was also operated and compared. The MM-SBBR (B) achieved a high chemical oxygen demand (COD), ammoniacal nitrogen (NH3-N), and PCP removal efficiencies, reaching 97%, 93% and 99%, respectively, which were attributed to the enrichment of high PCP resistant bacteria in this reactor. It was found that the number of bacterial species was the highest (10 species) in Bioreactor B when compared to the other bioreactors (Bioreactor A, C, D, and E). Proteobacteria phylum (9 species) was found dominated throughout the study, suggesting that the combination MM with granular activated carbon (GAC) and plastic media encouraged the growth of various bacterial species that were resistant to high-levels of PCP and thus enhancing the removal of PCP. It can be concluded that the hybrid treatment system of multimedia (MM) and SBBR is highly capable of removing PCP from water contaminated with PCP due to the diversity presence of PCP resistant bacteria in this bioreactor. MM-SBBR could be the effective treatment method for wastewater containing PCP to improve water quality and ensure sustainability.

Black liquor (BL) rich phenolic and complex compounds is generated from pulp and paper mill manufacturing processes which should be treated before reaching the environment. The potential of achieving several sustainable development goals (SDGs) by recovering energy and valuable by-products from BL was extensively investigated. Results revealed that under a dark-fermentation process, the organic content in BL was effectively bio-degraded by anaerobes to achieve a hydrogen yield (HY) of 0.62 ± 0.04 mol/molglucose. Fortunately, the HY was significantly increased up to 1.41 ± 0.13 mol/molglucose by immobilizing the anaerobes onto magnetite nanoparticles (MN). α-amylase, xylanase, CM-cellulase, polygalacturinase, and protease enzymes activities were increased by 2.3, 23.7, 2.7, 26.8, and 31.1 folds with supplementation of MN. Moreover, the conversion efficiencies of protein and carbohydrate were improved by values of 36 and 113.3% and total phenolic compounds (TPC) were enhanced by 23.5% compared with the control test. Electron-equivalent and COD mass balances were estimated to comprehensively describe the effect of Mn supplementation on the HY performance and fermentation pathways. Digestate generated from the fermentation process was utilized to produce biochar, having C (58.2%), O (32.4%), Na (4.7%), and P (1.1%). The study outputs were interlinked to bio-energy generation, pollution minimization, biochar as a soil amendment, nanoparticles and paper manufacturing industrialization, meeting environmental, economic, and social related SDGs.