Wastewater treatment in the pulp-and-paper industry: A review of treatment processes and the associated greenhouse gas emission

Resource recovery and treatment of wastewaters using filamentous fungi

Industrial wastewater, often characterized by its proximity to neutral pH, presents a promising opportunity for fungal utilization despite the prevalent preference of fungi for acidic conditions. This review addresses this discrepancy, highlighting the potential of certain industrial wastewaters, particularly those with low pH levels, for fungal biorefinery. Additionally, the economic implications of biomass recovery and compound separation, factors that require explicit were emphasized. Through an in-depth analysis of various industrial sectors, including food processing, textiles, pharmaceuticals, and paper-pulp, this study explores how filamentous fungi can effectively harness the nutrient-rich content of wastewaters to produce valuable resources. The pivotal role of ligninolytic enzymes synthesized by fungi in wastewater purification is examined, as well as their ability to absorb metal contaminants. Furthermore, the diverse benefits of fungal biorefinery are underscored, including the production of protein-rich single-cell protein, biolipids, enzymes, and organic acids, which not only enhance environmental sustainability but also foster economic growth. Finally, the challenges associated with scaling up fungal biorefinery processes for wastewater treatment are critically evaluated, providing valuable insights for future research and industrial implementation. This comprehensive analysis aims to elucidate the potential of fungal biorefinery in addressing industrial wastewater challenges while promoting sustainable resource utilization.

Multiobjective Optimization of Papermaking Wastewater Treatment Processes under Economic, Energy, and Environmental Goals

Due to the heterogeneity of recycled paper materials and the production conditions, pollutants in papermaking wastewater fluctuate sharply over time. Quality control of the papermaking wastewater treatment process (PWTP) is challenging and costly. As regulations are also growing about the environmental effects of the PWTP on greenhouse gas (GHG) emission, energy consumption, etc., the PWTP formulates a complex multiobjective optimization problem. This research established a multiagent deep reinforcement learning framework to simultaneously optimize process cost, energy consumption, and GHG emission in the PWTP, subjected to the effluent quality, to realize economic, energy, and environmental (3E) goals. The biological treatment process of wastewater in paper mills was simulated using benchmark simulation model no. 1 (BSM1). The data generated based on the BSM manual was utilized for model training, and real data acquired from a local papermaking factory was used to estimate the model performance. The results show that the proposed method outperforms conventional techniques in identifying the best control strategies for multiple targets.

Microbial valorization of kraft black liquor for production of platform chemicals, biofuels, and value-added products: A critical review

The proper treatment and utilization of kraft black liquor, generated from the pulp and paper industry through the kraft pulping method, is required to reduce environmental impacts prior to the final disposal. It also improves the economic performance through the utilization of waste. Microbial valorization appears to demonstrates the dual benefits of waste management and resource recovery by providing an innovative solution to convert kraft black liquor into resource for reuse. A comprehensive review on the microbial valorization of kraft black liquor, describing the role in valorization and management, is still lacking in the literature, forming the rationale of this article. Thus, the present study reviews and systematically discusses the potential of utilizing microorganisms to valorize kraft black liquor as a sustainable feedstock to develop a numerous portfolio of platform chemicals, bioenergy, and other value-added products. This work contributes to sustainability and resource efficiency within the pulp and paper industry. The recent developments in utilization of synthetic biology tools and molecular techniques, including omics approaches for engineering novel microbial strains, for enhancing kraft black liquor valorization has been presented. This review explores how the better utilization of kraft black liquor in the pulp and paper industry contributes to achieving UN Sustainable Development Goals (SDGs), particularly clean water and sanitation (SDG 6) as well as the affordable and clean energy goal (SDG 7). The current review also addresses challenges related to toxicity, impurities, low productivity, and downstream processing that serve as obstacles to the progress of developing highly efficient bioproducts. The new directions for future research efforts to fill the critical knowledge gaps are proposed. This study concludes that by implementing microbial valorization techniques, the pulp and paper industry can transition from a linear to a circular bioeconomy and eco-friendly manage the kraft black liuor. This approach showed to be effective towards resource recovery, while simultaneously minimizing the environmental burden.

Comprehensive review of industrial wastewater treatment techniques

Water is an indispensable resource for human activity and the environment. Industrial activities generate vast quantities of wastewater that may be heavily polluted or contain toxic contaminants, posing environmental and public health challenges. Different industries generate wastewater with widely varying characteristics, such as the quantity generated, concentration, and pollutant type. It is essential to understand these characteristics to select available treatment techniques for implementation in wastewater treatment facilities to promote sustainable water usage. This review article provides an overview of wastewaters generated by various industries and commonly applied treatment techniques. The characteristics, advantages, and disadvantages of physical, chemical, and biological treatment methods are presented.

Assessing the impact of industrial intelligence on urban carbon emission performance: Evidence from China

With the growing emphasis on sustainable development, there has been increasing attention given to measures aimed at promoting environmental improvements and reducing carbon emissions, including the adoption of intelligent industry. Recent studies have analyzed the influence of industrial intelligence on urban carbon emission performance while ignore the spatial spillover effects and lack in-depth discussion of the mechanisms, which reduces the reliability of the assessment of industrial intelligence's impact on carbon emission performance. To address this issue, the paper examines direct effect, spatial spillover effects, and mechanisms, utilizing a balanced panel data from 2008 to 2019 for 238 Chinese cities. The findings reveal that a 1 % improvement in industrial intelligence results in a 2.747 % enhancement of local carbon emission performance. Moreover, through the spatial spillover analysis, we determined that industrial intelligence has a notable negative impact on the carbon emission performance of surrounding areas. The mechanism analysis demonstrated that industrial intelligence affects the carbon emission performance of local and neighboring areas by influencing the agglomeration of productive services. Furthermore, our study illustrates that the industrial intelligence's enhancement effect on carbon emission performance shows more significantly in eastern, resource-dependent, and ordinary prefecture-level cities. Finally, endogeneity and robustness tests conducted yielded consistent conclusions. Our study provides a new perspective on industrial intelligence's carbon reduction effect and contributes to the development of policies related to industrial upgrading and green development.

New insights into toxicity reduction and pollutants removal during typical treatment of papermaking wastewater

Papermaking wastewater contained various of toxic and hazardous pollutants that pose significant threats to both the ecosystem and human health. Despite these risks, limited research has addressed the detoxification efficiency and mechanism involved in the typical process treatment of papermaking wastewater. In this study, the acute toxicity of papermaking wastewater after different treatment processes was assessed using luminousbacteria, zebrafish and Daphnia magna (D. magna). Meanwhile, the pollution parament of the corresponding wastewater were measured, and the transformation of organic pollutant in the wastewater was identified by three-dimensional fluorescence and other techniques. Finally, the possible mechanism of toxicity variation in different treatment processes were explored in combination with correlation analyses. The results showed that raw papermaking wastewater displayed high acute toxicity to luminousbacteria, and exhibited slight acute toxicity and acute toxicity effect to zebrafish and D. magna, respectively. After physical and biochemical processes, not only the toxicity of the wastewater to zebrafish and D. magna was completely eliminated, but also the inhibitory effect on luminousbacteria was significantly reduced (TU value decreased from 11.07 to 1.66). Among them, the order of detoxification efficiency on luminousbacteria was air flotation > hydrolysis acidification > IC > aerobic process. Correlation analyses revealed a direct link between the reduced of Total Organic Carbon (TOC) and Chemical Oxygen Demand (COD) and the detoxification efficiency of the different processes on the wastewater. In particular, the removal of benzene-containing aromatic pollutant correlated positively with decreased toxicity. However, the Fenton process, despite lowering TOC and COD, increased of the acute toxicity of the luminousbacteria (TU value increased from 1.66 to 2.33). This may result from the transformation generation of organic pollutant and oxidant residues during the Fenton process. Hence, oxidation technologies such as the Fenton process, as a deep treatment process, should be more concerned about the ecological risks that may be caused while focusing on their effectiveness in removing pollutant.

Country-specific net-zero strategies of the pulp and paper industry

The pulp and paper industry is an important contributor to global greenhouse gas emissions1,2. Country-specific strategies are essential for the industry to achieve net-zero emissions by 2050, given its vast heterogeneities across countries3,4. Here we develop a comprehensive bottom-up assessment of net greenhouse gas emissions of the domestic paper-related sectors for 30 major countries from 1961 to 2019-about 3.2% of global anthropogenic greenhouse gas emissions from the same period5-and explore mitigation strategies through 2,160 scenarios covering key factors. Our results show substantial differences across countries in terms of historical emissions evolution trends and structure. All countries can achieve net-zero emissions for their pulp and paper industry by 2050, with a single measure for most developed countries and several measures for most developing countries. Except for energy-efficiency improvement and energy-system decarbonization, tropical developing countries with abundant forest resources should give priority to sustainable forest management, whereas other developing countries should pay more attention to enhancing methane capture rate and reducing recycling. These insights are crucial for developing net-zero strategies tailored to each country and achieving net-zero emissions by 2050 for the pulp and paper industry.

Performance evaluation of gravity-driven bioreactor (GDB) for simultaneous treatment of black liquor and domestic wastewater

A lab-scale gravity-driven bioreactor (GDB) was designed and constructed to evaluate the simultaneous treatment of black liquor and domestic wastewater. The GDB was operated with a mixture of black liquor and domestic wastewater at a ratio of 1:1 and maintained at an average organic loading rate of 1235 mg-COD/L-Day. The wastewater was fed to the primary sedimentation tank at a flow rate of approximately 12 mL/min and subsequently passed through serially connected anaerobic and aerobic chambers with the same flow rate. Each wastewater sample was allowed to undergo a hydraulic retention time of approximately 72 h, ensuring effective treatment. The GDB was actively operated for nine samples (W1-W9) at a weekly frequency. The entire process was conducted within the workstation's ambient temperature range of 30-35 °C to sustain microbial activity and treatment efficiency in an open environment. The performance of the GDB was evaluated in terms of various pollution indicators, including COD, BOD5, lignin removal, TDS, TSS, EC, PO43-, SO42-, microbial load (CFU/mL and MPN index), total nitrogen, and color reduction. The results showed that the GDB achieved promising treatment efficiencies: 84.5% for COD, 71.80% for BOD5, 82.8% for TDS, 100% for TSS, 74.71% for E.C., 67.25% for PO43-, 81% for SO42-, and 69.36% for TN. Additionally, about 80% reduction in lignin content and 57% color reduction were observed after the treatment. The GDB substantially reduced microbial load in CFU/mL (77.98%) and MPN (90%). This study marks the first to report on wastewater treatment from two different sources (black liquor and domestic wastewater) using a simple GDB design. Furthermore, it highlights the GDB's potential as a cost-effective, environmentally friendly, and efficient solution for wastewater treatment, with no need for supplementary chemical or physical agents and zero operational costs.

Ultra-High-Molecular-Weight, Narrow-Polydispersity Polyacrylamides Synthesized Using Photoiniferter Polymerization to Generate High-Performance Flocculants

Ultra-high-molecular-weight, water-soluble polyelectrolytes are commonly employed as flocculants for solid-liquid separation via colloidal destabilization, enabling the rapid and efficient removal of particulate matter from wastewater streams. A drive toward more sustainable and less polluting industrial practices, coupled with the desire to reduce freshwater usage and improve closed-loop systems, demands the development of flocculants with ever-higher dewatering dose performance. Herein, the use of trithiocarbonate-mediated reversible addition-fragmentation chain transfer (RAFT) polymerization under either blue LED (λmax = 470 nm) or UV (λmax = 365 nm) irradiation, known as photoiniferter polymerization, was successfully utilized to generate ultra-high-molecular-weight (Mn > 1,000,000 g mol-1) polyelectrolyte copolymer flocculants with narrow molecular weight distributions (Mw/Mn < 1.2). Cationic and anionic polyelectrolyte flocculants were synthesized containing various monomer compositions of acrylamide (AM), dimethylacrylamide (DMA), 3-(acryloyloxyethyll)trimethylammonium chloride (DMAEAq), 3-(acrylamidopropyl)trimethylammonium chloride (APTAC), sodium acrylate (NaAA), and sodium 2-(acrylamido)-2-methylpropylsulfonate (NaATBS) with high monomer conversion using simple experimental apparatus. The narrow molecular weight distribution cationic polyelectrolytes showed improved flocculation efficiency in the clarification of kaolin suspensions of up to 50% in comparison to a broad polydispersity (Mw/Mn > 5.0) commercial benchmark with an equivalent number average molecular weight. The improved performance of the narrow-polydispersity copolymers is attributed to the reduction in the content of the lower-molecular-weight polymer chains, which impart lower flocculation performance.

Trickling filter systems for sustainable water supply: An evaluation of eco-environmental burdens and greenhouse gas emissions

Despite the global water crisis, the significant potential of trickling filter systems as a crucial auxiliary option for sustainable water supply has received insufficient attention. Therefore, this study presents the first-ever evaluation of the environmental impacts of trickling filter application in wastewater treatment, focusing on eco-environmental burdens. Additionally, the study explores greenhouse gas emissions, energy, and exergy footprints, providing novel insights into the environmental implications of using trickling filters for wastewater treatment. The study's findings indicate that the consumption of heat and electricity in trickling filters has significant environmental impacts, particularly on land use (93.24%), freshwater/marine eutrophication (∼81.98%), and human health (45.36%). The majority of the energy required for trickling filter operation is supplied by fossil fuels (96.02%), resulting in increased greenhouse gas emissions (65.58%). The exergy of trickling filters is highly efficient, accounting for over 95% of the system's energy. Mathematical modeling reveals that anaerobic digestion and secondary clarifier have the highest energy consumption, with contributions of 94.65% and 2.63%, respectively. Construction expenses account for almost 88% of the total cost, with anaerobic digestion (42.15%) and trickling filters (35.39%) being the most costly components. The cost of treating 1 m3 of wastewater is estimated at 0.52 $/m3. Sensitivity analysis demonstrates that electricity (14.66%) and heat (18.65%) significantly impact terrestrial ecotoxicity and land use, respectively. This study presents a framework for future investigations in this field.

Heavy metals in vegetables: a review of status, human health concerns, and management options

For sustainable global growth, food security is a prime concern issue, both quantitatively and qualitatively. Adverse effects on crop quality from contaminants like heavy metals have affected food security and human health. Vegetables comprise the essential and nutritious part of the human diet as they contain a lot of health-promoting minerals and vitamins. However, the inadvertent excess accumulation of heavy metals (As, Cd, Hg, and Pb) in vegetables and their subsequent intake by humans may affect their physiology and metabolomics and has been associated with diseases like cancer, mental retardation, and immunosuppression. Many known sources of hazardous metals are volcano eruptions, soil erosion, use of chemical fertilizers in agriculture, the use of pesticides and herbicides, and irrigation with wastewater, industrial effluents, etc. that contaminate the vegetables through the soil, air and water. In this review, the problem of heavy metal contamination in vegetables is discussed along with the prospective management strategies like soil amendments, application of bioadsorbents, membrane filtration, bioremediation, and nanoremediation.

A critical review on graphene oxide membrane for industrial wastewater treatment

An important way to promote the environmental industry's goal of carbon reduction is to promote the recycling of resources. Membrane separation technology has unique advantages in resource recovery and advanced treatment of industrial wastewater. However, the great promise of traditional organic membrane is hampered by challenges associated with organic solvent tolerance, lack of oxidation resistance, and serious membrane fouling control. Moreover, the high concentrations of organic matter and inorganic salts in the membrane filtration concentrate also hinder the wider application of the membrane separation technology. The emerging cost-effective graphene oxide (GO)-based membrane with excellent resistance to organic solvents and oxidants, more hydrophilicity, lower membrane fouling, better separation performance has been expected to contribute more in industrial wastewater treatment. Herein, we provide comprehensive insights into the preparation and characteristic of GO membranes, as well as current research status and problems related to its future application in industrial wastewater treatment. Finally, concluding remarks and future perspectives have been deduced and recommended for the GO membrane separation technology application for industrial wastewater treatment, which leads to realizing sustainable wastewater recycling and a nearly "zero discharge" water treatment process.

Agricultural Residues as Raw Materials for Pulp and Paper Production: Overview and Applications on Membrane Fabrication

The need for pulp and paper has risen significantly due to exponential population growth, industrialization, and urbanization. Most paper manufacturing industries use wood fibers to meet pulp and paper requirements. The shortage of fibrous wood resources and increased deforestation are linked to the excessive dependence on wood for pulp and paper production. Therefore, non-wood substitutes, including corn stalks, sugarcane bagasse, wheat, and rice straw, cotton stalks, and others, may greatly alleviate the shortage of raw materials used to make pulp and paper. Non-woody raw materials can be pulped easily using soda/soda-AQ (anthraquinone), organosolv, and bio-pulping. The use of agricultural residues can also play a pivotal role in the development of polymeric membranes separating different molecular weight cut-off molecules from a variety of feedstocks in industries. These membranes range in applications from water purification to medicinal uses. Considering that some farmers still burn agricultural residues on the fields, resulting in significant air pollution and health issues, the use of agricultural residues in paper manufacturing can eventually help these producers to get better financial outcomes from the grown crop. This paper reviews the current trends in the technological pitch of pulp and paper production from agricultural residues using different pulping methods, with an insight into the application of membranes developed from lignocellulosic materials.

An environment-benign approach of bamboo pulp bleaching using extracellular xylanase of strain Bacillus stratosphericus EB-11 isolated from elephant dung

The use of microbial enzymes is highly encouraged in paper and pulp industries to reduce the excessive use of hazardous chemicals. During the study, xylanase of Bacillus stratosphericus EB-11 was characterized for pulp bleaching applications. The extracellular xylanase was produced under submerged fermentation using bamboo waste as a natural carbon source. There was fast cell division and enzyme production under optimized fermentation conditions in the bioreactor. The highest activity was 91,200U after 30 h of growth with Km and Vmax of 3.52 mg/mL and 391.5 μmol/min per mg respectively. The purified enzyme with molecular mass ~ 60 kDa had conferred positive activity on native PAGE. The strong inhibition by ethylenediaminetetraacetate and SDS showed the metallo-xylanase nature of the purified enzyme. The bacterial xylanase reduces the use of hydrogen peroxide by 0.4%. Similarly, biological oxygen demand and chemical oxygen demand were reduced by 42.6 and 35.2%. The xylanase-hydrogen peroxide combined treatment and conventional chlorine dioxide-alkaline (CDE₁D₁D₂) bleaching showed almost similar improvement in physicochemical properties of bamboo pulp. Xylanase-peroxide bleaching reduces the lignin content to 4.95% from 13.32% unbleached pulp. This content after CDE₁D₁D₂ treatment was 4.21%. The kappa number decreased from 15.2 to 9.46 with increasing the burst factor (15.51), crystallinity index (60.25%), viscosity (20.1 cp), and brightness (65.4%). The overall finding will encourage the development of new cleaner methods of bleaching in the paper and pulp industry.

Valorisation of residual iron dust as Fenton catalyst for pulp and paper wastewater treatment

In this work, the performance of residual iron dust (RID) from metallurgic industry was assessed as Fenton catalyst for the treatment of real pulp bleaching wastewater. The focus was on the removal of recalcitrant pollutants AOX (adsorbable organic halides), by a novel, cleaner, and cost-effective circular solution based on a waste-derived catalyst. The behaviour of RID as iron source was firstly assessed by performing leaching tests at different RID:wastewater w/v ratios and contact time. Afterwards, RID-catalysed homogeneous and heterogeneous Fenton processes were conducted to maximise AOX removal from the pulp bleaching wastewater. Reusability of RID was assessed by a simple collect-and-reuse methodology, without any modification. Similar AOX removal under less consumption of chemicals was achieved with the novel heterogeneous Fenton process. Reaction in the bulk solution was the main pathway of AOX removal, given that the low surface area and porosity of the material did not allow for a high contribution of surface reaction to the overall performance. Moreover, AOX removal was similar over two consecutive treatment cycles, with Fenton process being responsible for 56.7-62.1% removal of AOX from the wastewater, and the leaching step adding 11.4-13.2%. At the end of treatment, COD either decreased (1^st cycle) or remained unchanged (2^nd and 3^rd cycle). The operating cost of the optimised heterogeneous Fenton was 3-11% lower than under conventional Fenton process. This work presented a novel, circular solution based on a low-cost waste-derived catalyst, advancing the knowledge needed to foster industrial application of such technologies to increase industrial environmental performance and efficiency.

Characteristics and treatment of Brazilian pulp and paper mill effluents: a review

Pulp and paper industries are very important for developing the Brazilian economy. During production processes, many effluents are generated with high polluting potential. The objective of this study is to conduct an extensive literature review on the characteristics of effluents and treatment forms adopted by Brazilian mills in this industrial sector. Most consulted studies address raw (without treatment) and secondary (after biological treatment) effluents, considering their main characteristics like pH, chemical and biochemical oxygen demands (COD and BOD, respectively), color, solids, organochlorines, toxicity, estrogenic activity, and phenols. Raw effluents differ considerably in composition, depending on the type of paper produced, the pulping process employed, and other steps, like pulp bleaching. Raw effluent characteristics indicate that this effluent cannot be directly disposed of into water bodies, because it does not comply with federal and state disposal standards. Secondary effluents normally comply with Brazilian legislations, although some studies have reported COD and total phenol concentrations higher than disposal standards, suggesting that additional treatments are necessary. Treated effluent reuse was verified in some Brazilian mills, while its disposal in eucalyptus plantations has been considered a promising alternative for irrigation purposes.

High-value utilization of bamboo pulp black liquor lignin: Preparation of silicon-carbide derived materials and its application

The black liquor of bamboo pulp contains a large amount of silicon, which makes it difficult to separate industrial lignin, thus hindering its high-value utilization. Herein, this paper dedicates to exploring the high-value use of silica-containing lignin. Tetraethyl silicate (TEOS) was added to the above silicon-containing lignin for crosslinking with the lignin to prevent disintegration during carbonization and provide an additional source of silica. The carbonization is carried out at 600 °C (LT-6), 900 °C (LT-9) and 1200 °C (LT-12), and the structural evolution of SiO_xC_y is innovatively analyzed. The results show that LT-9 is dominated by the SiO₃C structure and has a specific surface area of 269 m² g^-1. The specific capacitance of LT-9 and LT-12 as supercapacitors electrodes is 78.6 F g^-1 and 74.8 F g^-1 at a current density of 1 A g^-1, and remains 95 % and 91.7 % after 10,000 cycles. Moreover, LT-9 has a high yield of 54 %. In this work, silicon-containing lignin is exploratively prepared as a silicon-carbide-derived material. Furthermore, the potential relationship between different SiO_xC_y molecular structures and electrochemical performance is evaluated, which is instructive for the high-value utilization of black liquor in bamboo pulp.

Optimization of Microalgae–Bacteria Consortium in the Treatment of Paper Pulp Wastewater

The microalgae–bacteria consortium is a promising and sustainable alternative for industrial wastewater treatment, since it may allow good removal of organic matter and nutrients, as well as the possibility of producing products with added value from the algae biomass. This research investigated the best bacterial and microalgae inoculation ratio for system start-up and evaluation of removing organic matter (as chemical oxygen demand (COD)), ammoniacal nitrogen (NH4+–N), nitrite nitrogen (NO2−–N), nitrate nitrogen (NO3−–N), phosphate phosphorus (PO43−–P) and biomass formation parameters in six photobioreactors with a total volume of 1000 mL. Reactors were operated for 14 days with the following ratios of pulp mill biomass aerobic (BA) and Scenedesmus sp. microalgae (MA): 0:1 (PBR1), 1:0 (PBR2), 1:1 (PBR3), 3:1 (PBR4), 5:1 (PBR5), and 1:3 (PBR6). Results show that COD removal was observed in just two days of operation in PBR4, PBR5, and PBR6, whereas for the other reactors (with a lower rate of initial inoculation) it took five days. The PBR5 and PBR6 performed better in terms of NH4+–N removal, with 86.81% and 77.11%, respectively, which can be attributed to assimilation by microalgae and nitrification by bacteria. PBR6, with the highest concentration of microalgae, had the higher PO43−–P removal (86%), showing the advantage of algae in consortium with bacteria for phosphorus uptake. PBR4 and PBR5, with the highest BA, led to a better biomass production and sedimentability on the second day of operation, with flocculation efficiencies values over 90%. Regarding the formation of extracellular polymeric substances (EPS), protein production was substantially higher in PBR4 and PBR5, with more BA, with average concentrations of 49.90 mg/L and 49.05 mg/L, respectively. The presence of cyanobacteria and Chlorophyceae was identified in all reactors except PBR1 (only MA), which may indicate a good formation and structuring of the microalgae–bacteria consortium. Scanning electron microscopy (SEM) analysis revealed that filamentous microalgae were employed as a foundation for the fixation of bacteria and other algae colonies.

Getting Value from Pulp and Paper Industry Wastes: On the Way to Sustainability and Circular Economy

The pulp and paper industry is recognized as a well-established sector, which throughout its process, generates a vast amount of waste streams with the capacity to be valorized. Typically, these residues are burned for energy purposes, but their use as substrates for biological processes could be a more efficient and sustainable alternative. With this aim, it is essential to identify and characterize each type of waste to determine its biotechnological potential. In this context, this research highlights possible alternatives with lower environmental impact and higher revenues. The bio-based pathway should be a promising alternative for the valorization of pulp and paper industry wastes, in particular for bioproduct production such as bioethanol, polyhydroxyalkanoates (PHA), and biogas. This article focuses on state of the art regarding the identification and characterization of these wastes, their main applied deconstruction technologies and the valorization pathways reported for the production of the abovementioned bioproducts.

A comprehensive review on comparison among effluent treatment methods and modern methods of treatment of industrial wastewater effluent from different sources

In recent years, rapid development in the industrial sector has offered console to the people but at the same time, generates numerous amounts of effluent composed of toxic elements like nitrogen, phosphorus, hydrocarbons, and heavy metals that influences the environment and mankind hazardously. While the technological advancements are made in industrial effluent treatment, there arising stretch in the techniques directing on hybrid system that are effective in resource recovery from effluent in an economical, less time consuming and viable manner. The key objective of this article is to study, propose and deliberate the process and products obtained from different industries and the quantity of effluents produced, and the most advanced and ultra-modern theoretical and scientific improvements in treatment methods to remove those dissolved matter and toxic substances and also the challenges and perspectives in these developments. The findings of this review appraise new eco-friendly technologies, provide intuition into the efficiency in contaminants removal and aids in interpreting degradation mechanism of toxic elements by various treatment assemblages.

Economic and environmental sustainability for anaerobic biological treatment of wastewater from paper and cardboard manufacturing industry

The sustainable application of an up-flow anaerobic baffled reactor (UABR) to treat real paper and cardboard industrial effluent (PCIE) containing bronopol (2-bromo-2-nitropropan-1, 3-diol) was investigated. At a hydraulic retention time (HRT) of 11.7 h and a bronopol concentration of 7.0 mg L^-1, the removal efficiencies of total chemical oxygen demand (COD_total), COD_soluble, COD_particulate, total suspended solids (TSS), volatile suspended solids (VSS), carbohydrates, and proteins were 55.3 ± 5.2%, 26.8 ± 2.3%, 94.4 ± 4.6%, 89.4 ± 2.6%, 84.5 ± 3.2%, 72.1 ± 1.8%, and 22.4 ± 1.8%, respectively. The conversion of complex organics (e.g., carbohydrates and proteins) into bio-methane (CH₄) was assisted via enzyme activities of, in U (100 mL)^-1, α-amylase (224-270), α-xylanase (171-188), carboxymethyl cellulase (CM-cellulase) (146-187), polygalacturonase (56-126), and protease (67,000-75300). The acidogenic condition was dominant at a short HRT of 2.9 h, where methane yield dropped by 32.5%. Under this condition, the growth of methanogenic bacteria could be inhibited by volatile fatty acids (VFA) accumulation. The analysis of Fourier-transform infrared (FTIR) spectra detected peaks relevant to methylene and nitro groups in the sludge samples, suggesting that entrapment/adsorption by the sludge bed could be a major mechanism for removing bronopol. The economic feasibility of UABR, as proposed to receive 100 m³ d^-1 of PCIE, showed a payback period (profits from environmental benefits, biogas recovery, and carbon credit) of 7.6 yr. The study outcomes showed a high connection to the environmental-, economic-, and social-related sustainable development goals (SDGs).

Technology status and trends of industrial wastewater treatment: A patent analysis

Globally, 80% of wastewater, among which 28% came from industry, returned to the ecosystem without treatment or reuse. The discharge of industrial wastewater poses public health and environmental concerns. The necessity and urgency of industrial wastewater treatment (IWT) will bring great challenges to most countries. This paper conducted the patent analysis combined with text mining to quantitatively analyze 11,840 patents related to IWT in the Derwent Innovations Index database. The results showed that: From 1973 to 2020, the number of patents related to IWT annually was increasing consistently. China ranked first in the number of patent publications. In contrast, the United States and some patent organizations, such as World Intellectual Property Organization, produced fewer patents, while they played more important roles in knowledge transfer. The core technology analysis suggested that method, device, material and related industry were hot topics. From activated sludge treatment technology, industrial wastewater treatment technology had gone through a development process from single technology treatment to combined technologies treatment. In the foreseeable future, research on devices for physical treatment, advanced oxidation processes, automated and energy-saving treatment systems were the promising directions.

An Integrated Water Quality Model to Support Multiscale Decisions in a Highly Altered Catchment

Decision-making in highly altered catchments occurs at different temporal and spatial scales, requiring integration of various datasets and models. This paper introduces two of the components of an environmental multiscale decision support system (EMDSS) for highly altered catchments, designed to make decisions at different time scales. First, an integrated dynamic flow and water quality model is proposed to analyze the river system, including wastewater discharges and water intakes. This integrated model is capable of representing unsteady flow conditions, allowing analysis at different time scales. Second, three postprocessing tools are presented to support short- (hours to days), medium- (days to months), and long- (years to decades) term operational, management, and planning decisions. The water quality component of the model can represent conventional and toxic determinands to simultaneously analyze domestic and industrial pollution throughout a river system. The first postprocessing tool of the EMDSS is useful in defining concentration limits for wastewater discharges for different water users downstream. The second tool allows the assessment of river water quantity and quality to determine water availability for intake extensions and medium-term wastewater flow augmentation. The third makes it possible to simulate and perform effective operational reservoir releases to improve water quality in the river during short-term pollution incidents. The proposed integrated model and postprocessing tools are applied in the upper Bogotá River stretch in Colombia, one of the most altered catchments and polluted rivers in the world. The results obtained illustrate the utility of the proposed EMDSS for river management and decision making regarding water quality at different time scales.

Integration of coagulation-flocculation and heterogeneous photocatalysis for the treatment of pulp and paper mill effluent

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 has been employed for the treatment of pulp and paper mill effluent. As the effluent is loaded with a high amount of organics with initial chemical oxygen demand (COD) as high as 3516, a pre-treatment is required before applying photocatalytic treatment. Coagulation-flocculation was identified as an effective pre-treatment strategy. Among the various coagulants tested, CuSO₄.5H₂O showed the best % COD reduction of 84 at pH 6, at a loading of 5 g/L. The primary treatment of coagulation improved the biodegradability index from 0.23 to 0.37. TRGO photocatalyst, employed in the second stage of photocatalytic treatment was synthesised by an ultrasound assisted solvothermal method and well characterised by various spectroscopic/analytical tools. The composite was found to be an efficient solar photocatalyst and achieved 1.76 and 2.1 times more COD reduction than synthesised TiO₂ and commercial P25 respectively. The final effluent after the combined treatment was neutral and the biochemical oxygen demand (BOD) and COD were 11.7 and 120 mg/L respectively which were below the given limit of National Environmental Quality Standards.

Trends and strategies in the effluent treatment of pulp and paper industries: A review highlighting reactor options

From the beginning of the paper-making process, the pulp and paper industry has utilized a large amount of water and generated a vast amount of highly polluted wastewater. The paper industry faces global pressure to reduce water use and lower environmental pollution. However, traditional physicochemical methods of wastewater treatment need high energy input, and their ecological impact is questionable. Due to the zero discharged policy, the industries urgently require novel eco-friendly, sustainable, and efficient treatment techniques. Microbial technology is the most recommended option to treat wastewater and support sustainable growth. The present article describes the overview of traditional and novel methods, including membrane bioreactor (MBR) and moving-bed biofilm reactor (MBBR) technology's with their current state and their limits for treating pulp and paper wastewater. It is expected to integrate the novel methods with advanced hybrid technology to fulfill wastewater treatment criteria and prospects. Furthermore, coupling MBR and MBBR technology make energy and water recovery possible, and recycling wastewater will be economically and environmentally feasible.

Effects of nickle, nickle-cobalt and nickle-cobalt-phosphorus nanocatalysts for enhancing biohydrogen production in microbial electrolysis cells using paper industry wastewater

Paper industries are water-intensive industries that produce large amount of wastewater containing dyes, toxicity and high nutrient content. These industries require sustainable technology for their waste disposal and MEC could be one of them. However, effective MEC operation at neutral pH and ambient temperature requires economical and efficient cathodes that are capable to treat indusial wastewater along with recovery of energy/biohydrogen. Co-deposits of Nickel, Nickel-Cobalt and Nickel-Cobalt-Phosphorous on the surface of SS and Cu base metals distinctly were used as cathodes in MEC for the concurrent treatment of real paper industry wastewater and biohydrogen production. MECs were utilized in batch mode at neutral pH, applied voltage of 0.6 V and 30 ± 2 °C temperature with paper industry wastewater and activated sludge as microbial sources. The fabricated Nickel-Cobalt-Phosphorous gives the higher hydrogen production rate of 0.16 ± 0.002 m³(H₂) m^-3d^-1 and 0.14 ± 0.002 m³(H₂) m ^-3d ^-1 respectively, with ~33-42 % treatment efficiency for a 500 ml wastewater in 7-day batch cycle in both the cases; while it is lowest in the case of the control cathodes (SS1 (0.07 ± 0.002 m³(H₂) m^-3d^-1) & Cu1 (0.06 ± 0.004 m³(H₂) m^-3d^-1)). It was also found that fabricated cathodes have the capability to treat industrial wastewater at ambient conditions efficiently with higher energy recovery. Prepared cathodes show enhanced hydrogen production and treatment efficiency as well as are competitive to some reported literature.

Evaluating CO2 emissions from continuous flow and batch growth systems under autotrophic mode: Implications for GHG accounting of biological nutrient removal

The oxidation of ammonia by autotrophic bacteria is a central part of the nitrogen cycle and a fundamental aspect of biological nutrient removal (BNR) during wastewater treatment. Autotrophic ammonia oxidation produces protons and results in net-CO₂ production due to the neutralizing effect of bicarbonate alkalinity. Attention must be paid to the propensity for this produced CO₂ to be transferred to the atmosphere where it can act as a greenhouse gas (GHG). In the context of BNR systems, bicarbonate-derived CO₂ emissions should be considered distinct from the biogenic CO₂ that arises from cellular respiration, though this distinction is not made in current GHG accounting practices. The aim of this study was to evaluate the performance of two experimental systems operated under autotrophic mode and buffered with bicarbonate, to investigate the relationship between ammonia removal and gaseous CO₂ emissions. The first system consisted of continuously aerated lab-scale batch reactors, which were effective in demonstrating the important link between ammonia oxidizer activity, pH, and gaseous CO₂ production. Depletion of the buffer system always led to a rapid decline in system pH and cessation of CO₂ emissions when the pH fell below 7.0. The second system was a tubular continuous-flow biofilm reactor which permitted comparison of ammonia removal and CO₂ emission rates. A linear relationship between ammonia removal and CO₂ emissions was demonstrated and the quantified CO₂ production was relatively close to that which was predicted based on the stoichiometry of nitrification, with this CO₂ being detected in the gas phase. It was apparent that this system offered minimal resistance to the mass transfer of CO₂ from the liquid to gas, which is an important factor that determines how much of the bicarbonate-derived CO₂ may contribute to greenhouse gas emissions in engineered systems such as those used for BNR.

Valorization of pulp and paper industry wastewater using sludge enriched with nitrogen-fixing bacteria

Nitrogen-fixing bacteria (NFB) can reduce nitrogen at ambient pressure and temperature. In this study, we treated effluent from a paper mill in sequencing batch reactors (SBRs) and monitored the abundance and activity of NFB with a view to producing a sludge that could work as a biofertilizer. Four reactors were inoculated with activated sludge enriched with NFB and fed with a high C/N waste (100:0.5) from a paper mill. Though the reactors were able to reduce the organic load of the wastewater by up to 89%, they did not have any nitrogen-fixing activity and showed a decrease in the putative number of NFB (quantified with qPCR). The most abundant species in the reactors treating high C/N paper mill wastewater was identified by Illumina MiSeq 16S rRNA gene amplicon sequencing as Methyloversatilis sp. (relative abundance of 4.4%). Nitrogen fixation was observed when the C/N ratio was increased by adding sucrose. We suspect that real-world biological nitrogen fixation (BNF) will only occur where there is a C/N ratio ≤100:0.07. Consequently, operators should actively avoid adding or allowing nitrogen in the waste streams if they wish to valorize their sludge and reduce running costs. PRACTITIONER POINTS: Efficient biological wastewater treatment of low nitrogen paper mill effluent was achieved without nutrient supplementation. The sludge was still capable of fixing nitrogen although this process was not observed in the wastewater treatment system. This high C/N wastewater treatment technology could be used with effluents from cassava flour, olive oil, wine and dairy industries.

Bioremediation of lignin derivatives and phenolics in wastewater with lignin modifying enzymes: Status, opportunities and challenges

Lignin modifying enzymes from fungi and bacteria are potential biocatalysts for sustainable mitigation of different potentially toxic pollutants in wastewater. Notably, the paper and pulp industry generates enormous amounts of wastewater containing high amounts of complex lignin-derived chlorinated phenolics and sulfonated pollutants. The presence of these compounds in wastewater is a critical issue from environmental and toxicological perspectives. Some chloro-phenols are harmful to the environment and human health, as they exert carcinogenic, mutagenic, cytotoxic, and endocrine-disrupting effects. In order to address these most urgent concerns, the use of oxidative lignin modifying enzymes for bioremediation has come into focus. These enzymes catalyze modification of phenolic and non-phenolic lignin-derived substances, and include laccase and a range of peroxidases, specifically lignin peroxidase (LiP), manganese peroxidase (MnP), versatile peroxidase (VP), and dye-decolorizing peroxidase (DyP). In this review, we explore the key pollutant-generating steps in paper and pulp processing, summarize the most recently reported toxicological effects of industrial lignin-derived phenolic compounds, especially chlorinated phenolic pollutants, and outline bioremediation approaches for pollutant mitigation in wastewater from this industry, emphasizing the oxidative catalytic potential of oxidative lignin modifying enzymes in this regard. We highlight other emerging biotechnical approaches, including phytobioremediation, bioaugmentation, Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)-based technology, protein engineering, and degradation pathways prediction, that are currently gathering momentum for the mitigation of wastewater pollutants. Finally, we address current research needs and options for maximizing sustainable biobased and biocatalytic degradation of toxic industrial wastewater pollutants.

Neighborhood component analysis for modeling papermaking wastewater treatment processes

It is of great importance to obtain accurate effluent quality indices in time for pulping and papermaking wastewater treatment processes. However, considering the complex characteristics of industrial wastewater treatment systems, conventional modeling methods such as partial least squares (PLS) and artificial neural networks (ANN) cannot achieve satisfactory prediction accuracy. As a supervised metric learning method, neighborhood component analysis (NCA) is able to significantly improve the prediction performance by training an appropriate model in metric space using the distance between samples for papermaking wastewater treatment processes. The results on two data sets show that NCA has a higher prediction accuracy compared with PLS and ANN. Specifically, NCA has the highest determination coefficient (R²) and the lowest root mean square error in a benchmark simulation data set. On the other hand, the results on the data from an industrial wastewater process indicate that NCA has better modeling accuracy and its R² increases by 32.80% and 29.08% compared with PLS and ANN, respectively. NCA provides a feasible way to realize online monitoring and automatic control in wastewater treatment processes.

Electrochemical technique for paper mill effluent degradation using concentric aluminum tube electrodes (CATE

In this study, Taguchi experimental design was used to the optimize operating parameters for the degradation of paper mill effluent using electrochemical (EC) process with two-dimensional concentric aluminum tube electrodes (CATE). For this purpose, four significant experimental factors were used in four levels pH (6-9), electrolysis time (10-40 min), voltage (6-12 V) and surface area (357-624 cm2). The process parameters were optimized, through performing L16 orthogonal array of Taguchi technique, for the removal of chemical oxygen demand (COD) and turbidity. The percent COD and turbidity reductions were transferred into an accurate S/N ratio for a larger value is the better (LBT) response. The study presents a unique method of finding optimum combination of process parameters to illustrate their effect on the turbidity and COD reduction. The treatment conditions for the maximum elimination of the pollutants were second level of pH (7), third level of ET (30 min), fourth level of voltage (12 V) and second level of surface area (446 cm2). The confirmation experiment results were within the confidence intervals (CI) indicating an acceptable agreement between predicted and observed values. Based on the p-values, the electrolysis time and voltages were found to be the most significant factors for both COD and turbidity reduction. The findings of research indicated, that the Taguchi method can be used successfully for the treatment of paper industry effluent by electrochemical technique.

Recent trends and developments in Fenton processes for industrial wastewater treatment - A critical review

This study reviews the recent developments in the application of Fenton processes in real industrial wastewater treatment, focusing on heterogeneous catalysts and catalyst regeneration/reuse. This article presents the features, inherent advantages or drawbacks, and primary experimental results obtained on established and emerging Fenton processes, highlighting the course of innovations and current scenario in a research field that has recently undergone rapid transition. Therefore, a comprehensive literature survey was conducted to review studies published over the last decade dealing with application of Fenton processes to industrial wastewater treatment. The research in this field is primarily focused on discovering or synthesizing new materials to substitute conventional iron salt Fenton catalysts and/or regenerate and reuse the spent catalyst, in contrast to optimizing the application of existing materials. Hence, the emphasis is on producing reusable materials, transitioning from linear to circular economy. Some of the major challenges identified herein include analyzing or improving heterogeneous catalyst lifetime, determining the predominant pathway of heterogeneous and homogeneous catalysis to pollutant degradation, and defining the best layout to incorporate Fenton processes into full-scale treatment plants, particularly its coupling with biological treatment.

A case study on the treatment and recycling of the effluent generated from a thermo-mechanical pulp mill in Brazil after the installation of a new bleaching process

A Brazilian thermo-mechanical pulp mill (TMP) was evaluating the installation of a proposed bleaching process, with changes in the qualitative and quantitative characteristics of the wastewaters and the Effluent Treatment Plant (ETP). The objectives of this research were to evaluate the treatment plant configuration for the future industrial effluent, consisting of a flotation unit followed by an upflow anaerobic sludge blanket reactor (UASB), an activated sludge process and nanofiltration (NF) using polymeric membranes, and to study the technical feasibility of recycling the treated effluents in the industrial process. The possible options for recycling the treated effluent were determined through a water balance of the mill. The pulp quality was evaluated in laboratory bleaching assays, based on brightness and brightness reversion tests after the recycling of 50%, 75% and 100% of the treated effluent. The buildup of the non-process elements (NPE) in the industrial water cycle after each effluent recycling proportion was evaluated through computer simulation, using the Aspen Plus® simulator software. The future mill effluent, considering the implementation of a proposed bleaching stage with hydrogen peroxide, was generated in the laboratory and treated in a bench-scale effluent plant, simulating the future configuration. The treatment plant removed 99.8%, 99.2% and 61.6% of soluble COD, BOD₅ and color, respectively. The water consumption was highest in the bleaching plant and, therefore, the recycling of 50%, 75% and 100% of the treated effluent for washing the pulp was simulated. The brightness and brightness reversion of the pulp, with 100% of the treated effluent used in the bleaching process, were similar to those provided by fresh water. The recycling of 100% of the treated effluent in the proposed treatment plant was possible in the TMP pulp mill without decreasing the pulp quality.

Adsorptive decontamination of paper mill effluent by nano fly ash: response surface methodology, adsorption isotherm and reusability studies

In the present study, adsorption of colour and other pollutants from agro-based paper mill effluent onto fabricated coal fly ash nanoparticles (CFA-N) have been investigated. Response surface methodology was applied to evaluate the operational conditions for maximum ouster of colour from effluent by nano structured CFA-N. Maximum reduction in colour (92.45%) and other pollutants were obtained at optimum conditions: 60 min interaction time, 60 g/L adsorbent dosage and 80 rpm agitation rate. The regression coefficient values (adjusted R² = 0.7169; predicted R² = 0.7539) established harmony between predicted and the experimental data. The adsorption equilibrium results matched perfectly with both Langmuir and Freundlich isotherms with maximum adsorption capacity of 250 platinum-cobalt/g. Additionally, the efficacy of CFA-N was also assessed in a continuous column mode. Furthermore, the feasibility of treated effluent for irrigation purpose was checked by growing the plant Solanum lycopersicum. Overall, the findings demonstrated the outstanding role of inexpensive and abundantly available CFA-N in treatment of paper mill effluent to the required compliance levels.

Removal of hard COD from acidic eucalyptus kraft pulp bleach plant effluent streams using oxidoreductases

The bleach plant of a pulp and paper (P&P) mill presents a major source of wastewater containing toxic organic matter characterized as chemical oxygen demand (COD). Due to their high oxidizing power, oxidoreductases hold promise to be a key solution for the removal of dissolved organic material. Here, four oxidoreductases from different enzyme families were selected to treat bleach plant effluents. Haloperoxidase treatment of the final effluent resulted in the highest levels of decolorization (71%) and reduction of aromatic compounds (36%). Using single compound analysis, 27 low molecular weight compounds were found to be persistent throughout the wastewater treatment process and, therefore, classified as hard COD. The tested enzymes efficiently removed several of the identified COD compounds. Hence, this study suggests that the application of oxidoreductases will serve as an environmental-friendly solution for reducing waste from P&P production.

Bioelectrochemical treatment of real-field bagasse-based paper mill wastewater in dual-chambered microbial fuel cell

The present study is aimed at analysing the feasibility of bioelectrochemical treatment of bagasse-based paper mill wastewater. Bioelectrochemical treatment was carried out in dual-chambered microbial fuel cell with plain graphite plates as electrodes. Wastewater from sugarcane bagasse storage and washing units of paper mill was used as anolyte. High power density and current density of 53 mW m^-2 and 173 mA m^-2 at 470 Ω, respectively, could be produced with wastewater treatment efficiency of 85% and coulumbic efficiency of 6%. Whereas, wastewater from pulping and bleaching units of bagasse-based paper mill was not suitable for bioelectrochemical treatment, yielding low power density and current density of 4 mW m^-2 and 16 mA m^-2 respectively at 10,000 Ω. Later, treating blended wastewater containing bagasse wash water and pulping wastewater in the ratio of 9:1 v/v generated higher power density and current density of 73 mW m^-2/202 mA m^-2, respectively, at 470 Ω, with wastewater treatment efficiency and coulumbic efficiency of 82% and 18%, respectively. Lignin and its derivatives present in pulping wastewater mediated electron transfer leading to high power density. Further, compounds in pulping wastewater were also toxic to methanogens growth in anode chamber of MFC, resulting in improved coulumbic efficiency of the blended wastewater treatment.

Bacterial valorization of pulp and paper industry process streams and waste

The pulp and paper industry is a major source of lignocellulose-containing streams. The components of lignocellulose material are lignin, hemicellulose, and cellulose that may be hydrolyzed into their smaller components and used as feedstocks for valorization efforts. Much of this material is contained in underutilized streams and waste products, such as black liquor, pulp and paper sludge, and wastewater. Bacterial fermentation strategies have suitable potential to upgrade lignocellulosic biomass contained in these streams to value-added chemicals. Bacterial conversion allows for a sustainable and economically feasible approach to valorizing these streams, which can bolster and expand applications of the pulp and paper industry. This review discusses the composition of pulp and paper streams, bacterial isolates from process streams that can be used for lignocellulose biotransformations, and technological approaches for improving valorization efforts. KEY POINTS: • Reviews the conversion of pulp and paper industry waste by bacterial isolates. • Metabolic pathways for the breakdown of lignocellulose components. • Methods for isolating bacteria, determining value-added products, and increasing product yields.

Assessment of Sustainability of Bio Treated Lignocellulose-Based Oleogels

The development of biological strategies to obtain new high-added value biopolymers from lignocellulosic biomass is a current challenge for scientific community. This study evaluates the biodegradability and ecotoxicity of new formulated oleogels obtained from fermented agricultural residues with Streptomyces, previously reported to show improved rheological and tribological characteristics compared to commercial mineral lubricants. Both new oleogels exhibited higher biodegradation rates than the commercial grease. Classical ecotoxicological bioassays using eukaryotic organisms (Lactuca sativa, Caenorhabditis elegans) showed that the toxic impact of the produced bio-lubricants was almost negligible and comparable to the commercial grease for the target organisms. In addition, high throughput molecular techniques using emerging next-generation DNA-sequencing technologies (NGS) were applied to study the structural changes of lubricant-exposed microbial populations of a standard soil. Results obtained showed that disposal of biomass-based lubricants in the soil environment did not substantially modify the structure and phylogenetic composition of the microbiome. These findings point out the feasibility and sustainability, in terms of biodegradability and eco-safety, of the new bio-lubricants in comparison with commercial mineral greases. This technology entails a promising biological strategy to replace fossil and non-renewable raw materials as well as to obtain useful biopolymers from agricultural residues with potential for large-scale applications.

Greenhouse gases emissions from duckweed pond system treating polyester resin wastewater containing 1,4-dioxane and heavy metals

Phytoremediation of polyester resin wastewater containing 1,4-dioxane and heavy metals using Lemna gibba (L.gibba) was enhanced by incorporation of perforated polyethylene carrier materials (PCM) onto the duckweed pond (DWP) system. The DWP module was operated at a hydraulic retention times (HRTs) of 2, 4 and 6 days and as well as 1,4-dioxane loading rate of 16, 25 and 48 g/m³.d. The maximum removal efficiency of 54 ± 2.5% was achieved for 1,4-dioxane at an HRT of 6 days and loading rate of 16 g1,4-dioxane/m³.d. Similarly, the DWP system provided removal efficiencies of 28.3 ± 2.1, 93.2 ± 7.6, 95.7 ± 8.9 and 93.6 ± 4.9% for Cd²⁺, Cu²⁺, Zn²⁺ and Ni²⁺ at influent concentration of 0.037 ± 0.01, 1.2 ± 0.9, 27.2 ± 4.7 and 4.6 ± 1.2 mg/L respectively. The structural analysis by Fourier-transform infrared spectroscopy (FTIR) clearly displayed a reduction of 1,4- dioxane in the treated effluent. A strong peak was detected for L. gibba plants at frequency of 3417.71 cm^-1 due to N-H stretching, which confirm the proposed mechanism of partially conversion of 1,4-dioxane into amino acids. Glycine, serine, aspartic, threonine and alanine content were increased in L. gibba by values of 35 ± 2.2, 40 ± 3.2, 48 ± 3.7, 31 ± 2.8, and 56 ± 4.1%, respectively. The contribution of DWP unit as a greenhouse gases (GHG) emissions were relatively low (1.65 gCO₂/Kg BOD_removed.d., and 18.3 gCO₂/Kg _biomass.d) due to photosynthesis process, low excess sludge production and consumption of CO₂ for nitrification process (1.4 gCO₂/kgN _removed.d). Based on these results, it is recommended to apply such a technology for treatment of polyester resin wastewater containing 1,4-dioxane and heavy metals at a HRT not exceeding 6 days.

Wastewater Management: Bibliometric Analysis of Scientific Literature

Two of the greatest challenges that threaten sustainable development are the water supply crisis together with the control of water resources pollution. The United Nations recognises that the right to safe drinking water and sanitation is an essential right, and states are called upon to intensify their efforts to provide the entire population with affordable access to safe drinking water. However, due to population growth and climate change, water resources are under great pressure, producing millions of cubic metres of wastewater. Due to the near impossibility of increasing water supply in a natural way, the importance of wastewater management as a method has grown in recent years, which, although it is not to increase the amount of this resource, but to facilitate its successive use before its final return to the sea. The objective of this article is to carry out a bibliometric analysis regarding the production and impact of the scientific research related to wastewater management indexed in the WoS and Scopus databases. The purpose is to know key aspects such as the progression of production over the years, maturity in research, coverage of the subject, identifying the most discussed topics and therefore identifying the gaps, the most relevant authors and the core of journals through which knowledge in this area is disseminated, as well as its impact through the analysis of citations. This analysis can help future researchers in this field by providing an overview of the current literature that helps them identify new research approaches to position their own work and identify the most relevant authors in this field. Likewise, a comparison is made on coverage and overlap between the two main international databases WoS and Scopus. From the analysis of the 211 articles selected through an advanced search by terms with a time limit set in 2018, it is concluded that we are facing a very incipient field of knowledge that has aroused great interest since 2010, with about half of the articles published in the period 2012–2018. Although WoS and Scopus differ in general terms in scope and coverage policies, both systems are complementary and not exclusive. In the specific area of wastewater management, Scopus is the base that provides the best coverage taking into account the number of articles published and the number of citations received.

Phytotoxicity indexes and removal of color, COD, phenols and ISA from pulp and paper mill wastewater post-treated by UV/H2O2 and photo-Fenton

Pulp and paper mill wastewater (PPMWW) contains high concentrations of recalcitrant compounds that cause toxicity to organisms. Advanced oxidation processes (AOPs) have the ability to degrade these compounds and reduce overall toxicity. Physicochemical characterization and Lactuca sativa toxicity test were conducted to compare the effectiveness of two post-treatments: UV/H₂O₂ and photo-Fenton. A comparison of four phytotoxicity indexes was carried out. PPMWW from a Brazilian treatment plant was characterized by high values of phenols, color, integrated spectral area (ISA), and chemical oxygen demand (COD), and caused significant inhibition to seedling development. The use of both post-treatments allowed the removal of over 75% of phenols, color, ISA, and COD. Although UV/H₂O₂ was more effective in removing phenols and ISA, photo-Fenton better reduced phytotoxicity. The most sensitive phytotoxicity indexes were RGIC_0.8 and GIC_80%, whereas SGC₀, REC_-0.25 and REC_-0.50 better showed the effectiveness of the post-treatments. We suggest the combined use of two phytotoxicity indexes: one that evaluates the effects on seed germination and, another, on root elongation, e.g., SGC₀ and RGIC_0.8. Additionally, we recommend the use of ISA for monitoring programs of wastewater treatments because it is a cost-effective approach that allows narrowing down the search and identification of compounds present in complex mixtures.