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- Herausgeber: John Wiley & Sons
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- Sprache: Englisch
Green Technologies for Industrial Contaminants is essential for understanding innovative, eco-friendly solutions to combat the pressing challenges of pollution and water scarcity faced by our planet.
Increasing population, environmental pollution, rampant industrialization, and scarcity of water are all major global threats. Significant amounts of pollutants are released from various industries such as textile, paper, leather, rubber, plastic, cosmetics, food, pharmaceuticals, and petroleum industries. A lack of proper treatment facilities has proliferated the discharge of effluents enriched with toxic pollutants such as dyes, heavy metals, organic compounds, and other hazardous chemicals in the environment. Water is a natural treasure and availability of safe and clean water is essential for human health, ecosystems, and sustainable development. The continuous decline of the groundwater table and deterioration of water quality are matters of serious concern. The presence of color in water poses a serious threat to the environment, affecting light penetration and reducing photosynthesis and dissolved oxygen. Most dyes and heavy metals are toxic in nature, which may cause skin irritation, allergies, respiratory disease, mental disorders, tumors, and cancer. Different physical and chemical methods are available for the treatment of industrial effluents but due to their high cost, low efficiency, and sludge generation, these methods are not feasible at large scale.
The synergistic approaches of biochar and microbes have an edge over other techniques, including being eco-friendly, cost-competitive and efficient, achieving complete mineralization, and showing low-waste production. Therefore, the combined application of biochar and microbes for pollutant degradation can be a viable option as it is a low-cost and sustainable effluent treatment system for industries. Green Technologies for Industrial Contaminants provides useful information and applications of microbes (bacteria, algae, fungi) and biochar for the removal of contaminants from industrial effluent and reutilization of waste sludge in the production of biofuel and bioenergy.
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Table of Contents
Cover
Table of Contents
Series Page
Title Page
Copyright Page
Preface
1 Membrane-Assisted Technologies for Treating Pulp and Paper Industry Wastewater
1.1 Introduction
1.2 Membrane-Based Technologies for Wastewater Treatment
1.3 Membrane Classification
1.4 Application of Membrane Technology in the Pulp and Paper Industry
1.5 Conclusion
References
2 Review of Recent Advances in Hazardous Waste Management of Chemical and Textile Industries Using Microbial-Assisted/Algae-Based Technologies
2.1 Introduction
2.2 Different Types of Waste from Chemical and Textile Industries
2.3 Microalgae and their Various Uses
2.4 Waste Treatment Using Microbial-Assisted/Algae-Based Technologies
2.5 Mechanisms of Remediation and the Factors which Influence them
2.6 Application of Various Bioremediation in Managing Industrial Pollution
2.7 Conclusion and Future Aspects for Waste Treatment Using Algae-Based Biomass
References
3 Environmental Contaminants: Sources, Types and Future Challenges: An Update
3.1 Introduction
3.2 Algal and Cyanobacterial Toxins
3.3 Novel Brominated Flame Retardants
3.4 Disinfection by-Products
3.5 Per- and Polyfluoroalkyl Substances (PFAS)
3.6 Hormones and Endocrine-Disrupting Compounds (EDCs)
3.7 Pharmaceuticals and Personal Care Products
3.8 Surfactants and Their Metabolites
3.9 Benzotriazoles and Dioxane
3.10 Plasticizers and Pesticides
3.11 Consequences of Current Trends of Environmental Contaminants
3.12 Future Challenges
References
4 Efficacy of Microbes in the Removal of Pesticides from Watershed System
4.1 Introduction
4.2 Remediation of Pesticides through the Biological Pathway—A Green and Prospective Approach
4.3 Enzymatic Degradation of Pesticide
4.4 Mechanism and Molecular Advancement of Pesticide Degradation
4.5
In-Vitro
Treatment Using Microbial Consortium
References
5 Emerging Environmental Contaminants: Sources, Consequences and Future Challenges
5.1 Introduction to Environmental Contaminants
5.2 Sources of Environmental Contaminants
5.3 Emerging Micro-Pollutants from Various Sources
5.4 Consequences of Emerging Environmental Contaminants
5.5 Contaminations and Their Routes
5.6 Types of Environmental Contaminants
5.7 Conclusion
References
6 Microbial Degradation of Textile Dyes: A Sustainable Approach for Treatment of Industrial Effluents
6.1 Introduction
6.2 Textile Dyes
6.3 Toxicity of Textile Dyes
6.4 Decolourization and Degradation of Textile Dyes
6.5 Microbial Degradation of Dyes
6.6 Fungal Dye Degradation
6.7 Dye Degradation by Fungal Consortia
6.8 Dye Degradation by Co-Microbial Cultures (Bacterial-Fungal Consortia)
6.9 Recent Advances and Future Prospects
6.10 Conclusion
Acknowledgements
References
7 Environmental Cleanup: Xenobiotic Degradation with Enzymes as Decontaminating Agents
7.1 Introduction
7.2 Classification of Xenobiotics
7.3 Catabolic Enzymes of Degradation Pathways
7.4 Hydrocarbon Degradation
7.5 Bioremediation Potential of Microorganisms for Xenobiotic Compounds
7.6 Enzymes
7.7 Conclusion
References
8 Removal of Microplastics from Wastewater: An Approach towards a Sustainable Ecosystem
8.1 Introduction
8.2 Detection Methods for MPs
8.3 Removal Techniques for MPs
8.4 Recent Techniques for Removal of MPs
8.5 Challenges and Future Perspectives
8.6 Conclusion
References
9 Endocrine-Disrupting Chemicals: Current Technologies for Removal from Aqueous Systems
9.1 Introduction
9.2 Common Forms of EDCs
9.3 Wastewater Treatment and EDCs Removal
9.4 Treatment Technologies for EDCs
9.5 Future Prospects
9.6 Conclusion
References
10 Current Status on Emerging Soil Applications of Biochar
10.1 Introduction
10.2 Biochar and Its Contents
10.3 Potential of Biochar to Influence Different Chemical Properties of Soil
10.4 Pyrolyzing Conditions, Nutrient Supplying Capacity, and Decomposition of Biochar
10.5 Impact of Biochar on Physical and Hydrological Properties of Soil
10.6 Effect of Biochar on Soil Biological Properties and Greenhouse Gases Emission
10.7 Influence of Biochar on Crop Yields
10.8 Biochar as a Slow Release Fertilizer
10.9 Conclusion
References
11 Microalgal Biorefineries: An Ingenious Framework towards Wastewater Treatment Coupled with Biofuel Production
11.1 Introduction
11.2 Microalgal Cultivation System
11.3 Generation of Value-Added Products Deploying Microalgae
11.4 Biorefinery Development through Microalgae
11.5 Microalgae-Mediated Wastewater Treatment
11.6 Integrated Wastewater Treatment and Algal Biofuel Production
11.7 Future Prospects
11.8 Conclusions
References
12 Plastic Pollution: Microbial Degradation of Plastic Waste
12.1 Introduction
12.2 Plastic Degradation Methods
12.3 Mechanism Involved in Plastic Degradation
12.4 Genetic Engineering for Plastic Degradation
12.5 Conclusion
References
Index
Also of Interest
End User License Agreement
List of Tables
Chapter 1
Table 1.1 Rejection percentages of impurities obtained for discharge wastewate...
Chapter 3
Table 3.1 Overview of some Novel Brominated Flame Retardants (NBFRs) and suspe...
Table 3.2 Classification of surfactants.
Chapter 4
Table 4.1 Microorganisms in degradation of pesticide.
Chapter 5
Table 5.1 Emerging contaminants.
Chapter 6
Table 6.1 Treatment methods for textile effluent.
Table 6.2 Dye degradation by fungal species.
Chapter 9
Table 9.1 Removal methods for EDCs and explanation [30].
Table 9.2 Adsorption capacities of different adsorbents for removal of EDCs.
Table 9.3 Different membrane filtration techniques for removal of EDCs.
Table 9.4 Various microalgae employed in removal of EDCs.
Chapter 11
Table 11.1 Different types of algae harvesting methods either at bench or pilo...
Table 11.2 Microalgae-mediated biorefinery development. Different algal specie...
Table 11.3 Recent advancements of algae-mediated wastewater treatment and biof...
Chapter 12
Table 12.1 Types of pretreatment methods employed for different polymers.
List of Illustrations
Chapter 1
Figure 1.1 (a) Impurities discharged by large-scale Indian pulp and paper indu...
Figure 1.2 (a) Heavy metal content discharged by large-scale Indian pulp and p...
Figure 1.3 (a) Graphical comparison of various pollutants generated from bleac...
Figure 1.4 Concentration of various pollutants obtained from E-stage effluent ...
Figure 1.5 Types of membrane-based processes used in the pulp and paper indust...
Figure 1.6 Classification of membranes.
Figure 1.7 Results of pilot trials of membrane filtration in an integrated pap...
Chapter 2
Figure 2.1 Sample biorefinery of microalgal biomass.
Figure 2.2 Effluent treatment using primary, secondary and biological methods.
Figure 2.3 Sample production system of biofuel using microalgae.
Chapter 3
Figure 3.1 Entry of emerging contaminants into the environment, their issues, ...
Chapter 4
Figure 4.1 Pesticide problems and microbial system application for removal of ...
Figure 4.2 Impact of pesticides on the living organism.
Chapter 5
Figure 5.1 Environmental contamination and its effects on humans.
Figure 5.2 Microplastic and its effects.
Figure 5.3 Effects of PFAS on human and undelivered baby.
Figure 5.4 Effects of PPCPs on the ecosystem.
Figure 5.5 Various sources of ECs and their routes.
Chapter 6
Figure 6.1 Different methods of dye removal
Chapter 7
Figure 7.1 Impact of xenobiotic compounds on environment and human health.
Figure 7.2 Microbial enzymes for detoxification of xenobiotics.
Chapter 10
Figure 10.1 Role of biochar in the circular economy model for sustainable deve...
Chapter 11
Figure 11.1 Schematic presentation of a multi-product biorefinery (biorefinery...
Figure 11.2 Process schematics of an integrated wastewater treatment and algal...
Chapter 12
Figure 12.1 General mechanism involved in the plastic degradation involving mi...
Figure 12.2 A three-step reaction scheme for plastic photodegradation.
Guide
Cover Page
Table of Contents
Series Page
Title Page
Copyright Page
Preface
Begin Reading
Index
Also of Interest
WILEY END USER LICENSE AGREEMENT
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Scrivener Publishing100 Cummings Center, Suite 541JBeverly, MA 01915-6106
Publishers at ScrivenerMartin Scrivener ([email protected])Phillip Carmical ([email protected])
Green Technologies for Industrial Contaminants
Edited by
Riti Thapar Kapoor
and
Rachana Singh
This edition first published 2025 by John Wiley & Sons, Inc., 111 River Street, Hoboken, NJ 07030, USA and Scrivener Publishing LLC, 100 Cummings Center, Suite 541J, Beverly, MA 01915, USA© 2025 Scrivener Publishing LLCFor more information about Scrivener publications please visit www.scrivenerpublishing.com.
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Library of Congress Cataloging-in-Publication Data
ISBN 978-1-394-15928-4
Front cover images supplied by Pixabay.comCover design by Russell Richardson
Preface
The world has witnessed a substantial upswing in economic prosperity, enhancement of living standards and national development due to industrial revolution. Nevertheless, this progress has been accompanied by a growing ecosystem imbalance, and drastic degradation in quality of natural resources. The overpopulation, urbanization, agricultural and industrial practices are generating huge amount of contaminants such as heavy metals, pesticides, pharmaceutical compounds, microplastics and synthetic dyes which are being released into water bodies without any proper treatment and contaminating environmental matrices at a continuous pace. Every year around ten million tons of toxic chemical compounds are released by different industries. The wastewater discharged from industries without any prior treatment negatively affect the natural resources and entire ecosystem. The ubiquitous presence of contaminants in environment poses significant threat to the safety of ecosystem and human health. The wide-spread distribution and long persistence of contaminants seriously threatening the environment and pose adverse effects on aquatic flora and fauna, plants, animals, and human-beings. Different physico-chemical technologies such as filtration, coagulation, flocculation, photocatalytic degradation, adsorption have been developed for the removal of contaminants from environment. Among these treatment methods, adsorption is one of the most sustainable and cost-effective procedure as other methods are expensive, time and energy consuming, require chemicals and generate secondary pollution. Hence, there is an urgent need of highly efficient, cost-effective, green technologies for elimination of pollutants and environment protection. Biochar is a carbon rich and porous material produced through the thermal decomposition of waste biomass or agricultural wastes under controlled oxygen limited conditions. Biochar can significantly remove different toxic pollutants and plays pivotal role in maintaining ecological balance and environment protection. Bioremediation has been considered as one of the most promising technology for removal of pollutants at a large scale. Application of microbes, microbial consortia or microbial enzymes are feasible and flexible green strategies for treatment of different xenobiotic compounds.
Richa Aggrawal et al. group of authors from Chemical Recovery and Biorefinery Division and Biotechnology Division, Central Pulp and Paper Research Institute, Saharanpur, Uttar Pradesh, India, present a comprehensive review on the development of membrane-assisted technologies for treatment of pulp and paper industry wastewater. Bibhab Kumar Lodh from Department of Chemical Engineering, National Institute of Technology Agartala, India focuses on hazardous waste management of chemical and textile industries by using microbial assisted/algae-based technologies. Ravi Kumar Gangwar et al. group of authors from multiple institutions like Hungarian University of Agriculture and Life Science, Gödöllő, Hungary, Department of Biotechnology, Utkarsh School of Management and Technology, Bareilly, Department of Environmental Science, Bareilly College, Bareilly, Uttar Pradesh and College of Agricultural Science, COER University, Roorkee, Uttarakhand, India highlight environmental contaminants, their sources, types and future challenges.
Prasann Kumar and their research group from Department of Agronomy and Department of Plant Pathology, Lovely Professional University, Phagwara, Punjab, and Institute of Agricultural Sciences, Banaras Hindu University, Varanasi, India focus on efficacy of microbes in the removal of pesticides from watershed system. Neetu Talreja and their research group from Division of Chemistry, Alliance University, Bengaluru, Karnataka, Bioserve Biotechnologies, Hyderabad, Telangana, and School of Science & Environmental Studies, Dr. Vishwanath Karad MIT World Peace University, Pune, Maharashtra, India highlight sources, consequences and future challenges of emerging environmental pollutants. Shivanshi Tyagi et al. from Centre for Plant and Environmental Biotechnology, Amity Institute of Biotechnology, Amity University Uttar Pradesh, Noida, India describe microbial degradation of various textile dyes which is a sustainable approach for treatment of industrial effluents. Sonia Sethi and Gokulendra Singh Bhatti from Dr. B. Lal Institute of Biotechnology, Jaipur, Rajasthan, India define various xenobiotic compounds and bioremediation potential of microbial enzymes for xenobiotic compounds. Neha Rana and Piyush Gupta from Department of Pharmaceutical Sciences, KIET Group of Institutions, Ghaziabad and Department of Chemistry, SRM Institute of Science and Technology, Ghaziabad, Uttar Pradesh, India cover removal of microplastics from wastewater and application of current technologies for elimination of endocrine-disrupting chemicals from aqueous system. They also highlight current status on emerging soil applications of biochar. Poulomi Ghosh and Saprativ P. Das from Department of Biotechnology, Institute of Genetic Engineering, Kolkata and Department of Chemical Engineering, Indian Institute of Technology Bombay, India focus on microalgal biorefineries for wastewater treatment coupled with biofuel production. Sushma Rani Tirkey et al. group of authors from multiple institutions like Applied Phycology and Biotechnology Division, CSIR-Central Salt and Marine Chemicals Research Institute, Bhavnagar and School of Basic and Applied Sciences, Dayananda Sagar University, Bengaluru, India describe plastic pollution and their degradation by microbes.
This book focuses on recent developments in sustainable technologies for removal of industrial wastes and environmental clean-up. The intended readers for this book includes environmentalists, scientists, industrial personnel, engineers, and policy makers who wish to utilize green technologies for removal of industrial contaminants. We are very thankful to the authors for contributing chapters and learned reviewers who carefully read and gave valuable feedback on the chapters of book to improve the quality. We would also like to very gratefully acknowledge the wonderful guidance and continuous support from the staff at the Scrivener Book Editorial Office, especially Phil Carmical, Fidel Rivera, Myrna Ting etc.
Riti Thapar Kapoor
Associate ProfessorCentre for Plant and Environmental BiotechnologyAmity Institute of BiotechnologyAmity University Uttar PradeshNoida, Uttar Pradesh, India
Rachana Singh
ProfessorCentre for Plant and Environmental BiotechnologyAmity Institute of BiotechnologyAmity University Uttar PradeshNoida, Uttar Pradesh, India
1Membrane-Assisted Technologies for Treating Pulp and Paper Industry Wastewater
Richa Aggrawal1, Jitender Dhiman2, Anshu1, Shrutikona Das1, Kumar Anupam1* and Ashwani Kumar Dixit1
1Chemical Recovery and Biorefinery Division, Central Pulp and Paper Research Institute, Himmat Nagar, Saharanpur, Uttar Pradesh, India
2Biotechnology Division, Central Pulp and Paper Research Institute, Himmat Nagar, Saharanpur, Uttar Pradesh, India
Abstract
The pulp and paper industry (PPI) is a water-intensive industry. It utilizes billions of cubic meters of water in the papermaking process. After that it produces an enormous amount of wastewater enriched with various contaminants, including biological oxygen demand, chemical oxygen demand, turbidity, color, heavy metal ions, etc. Eliminating these contaminants from PPI wastewater is necessary to meet the norms of various regulatory authorities to preserve the environment and human health. Literature suggests that these water pollutants from PPI can be treated using various technologies such as filtration, adsorption, precipitation, electrodialysis, coagulation, flocculation, floatation, ion-exchange, etc. Nevertheless, these techniques have several de-merits, like the massive requirement of physicochemical reagents, non-uniform pollutant removing capacity, generation of secondary hazardous solid waste, etc. Though these methods can sufficiently treat the above-mentioned impurities from PPI wastewater, the membrane technologies are known for a higher level of performance either implemented individually (reverse osmosis, ultrafiltration, and nanofiltration) or in hybrid configuration (reverse osmosis + ultrafiltration + nanofiltration, membrane + adsorption, membrane distillation, etc.). This chapter aims to present an anthology of different membrane-based techniques; operating parameters; and types, configuration, and characterization of membranes used for evaluation of membrane-based processes concerning the PPI wastewater treatment.
Keywords: Heavy metals, wastewater, membrane technologies, pilot plant, pulp and paper
1.1 Introduction
The pulp and papermaking industries are actively producing large quantities of paper worldwide. Paper production is not limited to writable paper but includes packaging paper, newsprints, charts, tissue paper, recyclable paper, cardboard, etc. Humankind has witnessed massive digitalization in the past few years, but the demand for paper has only increased with the population worldwide. This is because paper is still needed for various traditional tasks such as recordkeeping, official documentation, newspapers, pamphlets, etc. Near the early 2000s, global paper consumption was estimated to be 350 million tons annually [1]. An estimated figure shows that global paper and cardboard consumption reached 408 million tons in 2021 while consumption is expected to continue increasing over the next decade, reaching 476 million tonnes by 2032. India alone produces about 10.11 million tonnes of paper annually, about 2.5% of the world’s total production [2].
Another survey estimated that about 60,000-1,00,000 gallons of water are required to produce one tonne of paper, making the pulp and paper industry a highly water-intensive industry. Almost 47,000-80,000 gallons of this water is converted to wastewater from papermaking industries [3]. Papermaking involves a series of processes, such as cleaning and preparing raw material, beating and pulping, web forming, bleaching, pressing, drying, and producing the finished paper. Pulping may be defined as the disintegration of bulky fibrous matter into singular or smaller agglomerates of fibers which can be done mechanically or chemically. It can be either kraft pulping (use of NaOH, Na2S, and Na2CO3) or sulfite pulping (use of sulfurous acid (H2SO3) and bisulfite ions (HSO3-)) depending upon the type of chemicals used for cooking [4]. Also, the raw materials for pulping may differ in the range of hardwood, softwood, bagasse, wheat straw, grasses, reeds, coniferous woods, non-coniferous woods, etc. The different processes applied for papermaking are the reason for generating various contaminants released into the environment as a part of pulp and paper industry wastewater (PPIW).
The pulp and paper industry generates black liquor (BL) as waste material. This BL contains the contaminants from various processes while papermaking. The pulping stage alone contributes to BL’s most organic and inorganic substances. Because of pulping, various heavy metals, chlorides, silicates, sulfates, and many other compounds present in the raw materials are discharged into BL. Some amount of chemicals used for cooking is also discharged into BL. The bleaching stage releases lignins and chloro-lignins into BL. Almost 1.3 billion tonnes of BL is produced annually around the globe, of which 200 million tonnes of BL is recovered as dry solids from recovery boilers. These dry solids can be further disintegrated to obtain cooking chemicals (about 15 million tonnes) and steam (about 700 million tonnes), which makes BL the fifth most essential fuel generated worldwide [4]. After final papermaking, the BL generated comprises lignin, cellulose, resins, fatty acids, phenolic compounds, and hemicellulose, along with other toxic matter such as color, heavy metals, valuable chemicals, alkalis, organic content, inorganic content, biological oxygen demand (BOD), chemical oxygen demand (COD), total dissolved solid (TDS), total suspended solid (TSS), turbidity, etc.
Discharge values of these parameters are illustrated in Figure 1.1 (a) and (b) for the Indian pulp and paper industry, as suggested by Haq et al. [5], along with heavy metal content discharge in the same industries represented by Figure 1.2 (a) and (b) [5]. Heavy metals may be defined as a group of metals or metalloids that own relatively higher densities when compared to water. These are generally found in the d-block elements of the periodic table. Even in trace amounts, these heavy metals can cause massive damage to human health and the ecosystem. The introduction of heavy metals in PPIW is caused by several factors. The first and foremost reason is the raw material selected. Metals may be accumulated in woods and agro-residues from the soil where they are cultivated, the type of water fed to them for irrigation, and the fertilizers used to produce these raw materials. Other than the raw materials used for papermaking, the chemicals and additives used for pulping serve as the main reason for the presence of these heavy metals in wastewater. Heavy metals which are primarily observed in PPIW are copper (Cu), cadmium (Cd), nickel (Ni), manganese (Mn), lead (Pb), iron (Fe), and chromium (Cr). In contrast, other heavy metals may sometimes also be found in PPIW.
All these harmful pollutants can quickly degrade the environment if discharged untreated. It can cause carcinogenic, mutagenic, and genotoxic effects, becoming toxic or even lethal for human health, ecosystem, and aquatic life. Hence, it has become obligatory to remove these hazardous pollutants from PPIW not only to preserve the environment and maintain ecological balance but also for chemical recovery, to maintain the industry’s reputation, and to avoid any legal penalties due to the reckless discharge of wastewater. Many researchers have worked tirelessly to reduce these impurities from PPIW using numerous techniques, namely phytoremediation, oxidation, flocculation, coagulation, membrane separation, adsorption, electrolysis, etc. [6]. Generally, these techniques can yield good results but sometimes it becomes difficult to use them because of their high cost of adsorbent/flocculating materials, applicability to batch operations, smallscale operation, frequent maintenance, high energy requirement, toxic sludge production, etc. All these problems are countered when the membrane separation technique is used. Removal of contaminants using membrane separation can be achieved in continuous mode and at large-scale plants. No toxic sludge production exists, and the maintenance period is adequate [6].
Figure 1.1 (a) Impurities discharged by large-scale Indian pulp and paper industries (in ppm except pH) BOD: Biological oxygen demand, COD: Chemical oxygen demand, TDS: Total dissolved solids, TSS: Total suspended solids, TP: Total phenol, TN: Total nitrogen, P: Phosphate, Cl: Chloride, K: Potassium and Na: Sodium (in ppm except pH). (b) Impurities discharged by small-scale Indian pulp and paper industries (in ppm except pH) BOD: Biological oxygen demand, COD: Chemical oxygen demand, TDS: Total dissolved solids, TSS: Total suspended solids, TP: Total phenol, TN: Total nitrogen, P: Phosphate.
Figure 1.2 (a) Heavy metal content discharged by large-scale Indian pulp and paper industries. (b) Heavy metal content discharged by small-scale Indian pulp and paper industries.
The Indian paper industry is a highly water-intensive industry consuming large quantities of water. The industry has been progressively improving its water usage while achieving stipulated norms. However, it discharges enormous amounts of polluted effluents whose correct treatment is critical before discharge into the environment. Figures 1.3 (a) and (b) depict various pollutants (TDS, TSS, COD, BOD, color, chloride, and silica) generated from different sections of wood-based and agro-based paper mills [7]. The industry has gradually addressed these environmental challenges by adopting various measures, such as cleaner production technologies and moving towards the at-source reduction of pollutants approach, coupled with end-of-pipe treatment measures with the available wastewater treatment technologies. The closed water circuit is being practiced in most paper mills to minimize freshwater consumption due to the lack of water resources and increasing conflicts over water usage. However, this negatively impacts the paper mill’s product quality, productivity, and overall process efficiency.
Figure 1.3 (a) Graphical comparison of various pollutants generated from bleach alkaline extraction stream of wood-based and agro-based paper mills. (b) Graphical comparison of various pollutants generated from secondary clarifier outlet stream of wood-based and agro-based paper mills.
PPI effluent treatment plants (ETPs) usually perform primary treatment followed by secondary treatment, which addresses biological pollutants. These treatment systems consist mainly of aerated lagoons or activated sludge processes that enable the reduction of organic matter, ranging around 90% reduction of BOD and around 50% in COD. Figure 1.4 illustrates the concentration of various pollutants obtained from the E-stage effluent of a typical agro-based paper mill [7]. However, even with these high removal percentages, residual organic matter, including the inorganic constituents in wastewater, may be above the acceptable limit resulting mainly in color and TDS. Few of the medium and large paper mills have upgraded their ETPs by installing a tertiary treatment system comprising dual media filters/cube settlers, etc. Segregation allows treating process waters or effluents individually, close to where they are created; segregating clean and contaminated water fractions can significantly reduce effluent volume. The global tendency is towards the application of an advanced wastewater treatment system that enables significant improvement in the final wastewater quality or the reuse of the treated wastewater in the production process itself or other beneficial uses rather than discharging it into water bodies. Based on the technology assessment of the Indian paper industry, the membrane filtration process has been identified as the best available technology (BAT) option relevant in the Indian context for treating paper mill effluents.
The membrane separation technique involves passing a solution through a semipermeable barrier or membrane so that one or more species get separated from the solution. The part of the feed that passes through the membrane is called permeate, whereas the part discarded or collected at the interface of the membrane is called retentate. Both permeate and retentate can be fluid or solid, depending upon the type of mixture. The membrane separation technique works based on the pressure difference. The membranes are usually made of polymers, ceramics, or metals. Membrane modules can be flat asymmetric thin-film composite sheets, tubular, hollow fiber, and monolithic. Membrane separation can be classified into many types based on commercial usage, such as reverse osmosis, nano filtration ultra filtration, dialysis, electrodialysis, micro filtration, pervaporation, and gas permeation.
Figure 1.4 Concentration of various pollutants obtained from E-stage effluent of a typical agro-based paper mill.
Disadvantages of membrane separation technologies include fouling in membranes, cake formation at membrane surface leading to decreased efficiency, disintegrating or breaking up membrane materials on treatment with corrosive fluids, etc. However, the most significant problem when dealing with membranes is the considerable cost of production. Membranes are produced using various materials like polymers, ceramics, liquids, gases, etc. Also, they are designed considering the type of separation to be achieved. Hence, its flux, porosity, selectiveness, size, and other parameters are pre-defined, which leads to a considerable spike in the production of separating membranes. Thus, this chapter aims to present an overview of the membrane separation techniques employed to remove heavy metals from pulp and paper industry wastewater.
1.2 Membrane-Based Technologies for Wastewater Treatment
Over time, humans have gained technological superiority in membrane development [8], which resulted in increased membrane usage in wastewater treatment generated from PPI. According to need, different types of membrane-based processes used in PPI are illustrated in Figure 1.5. A brief summary of these processes has been presented in the following subsections.
1.2.1 Ultrafiltration
In Ultrafiltration (UF), a permeable membrane is utilized to eliminate heavy metals, macromolecules, and suspended solids from wastewater generated in PPI. Since the membrane possesses a pore size of 5–20 nm, UF allows water and solutes (low-molecular-weight) to pass through it while hindering the passage of macromolecules. UF separates the compounds having a molecular size from 20 to 100 nm and molecular weight of 1,000 to 100,000 Dalton (Da) [9]. Polycarbonate, cellulose acetate, polyacrylonitrile, polysulfone, and polyvinyl chloride are some polymers used to make UF membranes. Inorganic membranes are also getting famous in wastewater treatment as they have higher levels of durability than organic membranes. Since pores of the UF membrane are larger than ionic radii of heavy metal ions thus, micellar enhanced ultrafiltration (MEUF) and polymer enhanced ultrafiltration (PEUF) are used instead of simple UF. Submerged UF membranes and conventional UF membranes are categories of ultrafiltration membranes.
Figure 1.5 Types of membrane-based processes used in the pulp and paper industry.
1.2.1.1 Micellar-Enhanced Ultrafiltration (MEUF)
MEUF is a technique to eliminate heavy metal ions and organic/inorganic contaminants from industrial wastewater. MEUF is made by creating the bonding of membrane and surfactant. MEUF has high flux and selectivity characteristics, resulting in low-energy consumption, greater heavy metal removal efficiency, and compact size. MEUF is highly recommended for treating wastewater possessing low concentrations of heavy metals [10, 11].
1.2.1.2 Polymer-Enhanced Ultrafiltration (PEUF)
PEUFs are called polymer-supported, polymer-assisted, and complexation-enhanced ultra-filtrations. PEUF permits water and un-complexed components to pass through membrane pores, whereas it blocks heavy metal ions. PEUF shows effective extraction, low-energy cost, recovery, and reuse [12, 13]. PEUFs are manufactured by the integration of binding polymers to UF. Various functional groups such as amine, carboxylated, phosphonic, and sulfonate are responsible for the filtration action of PEUF [14].
1.2.1.3 Submerged Ultrafiltration Membranes
These membranes have open and hollow fibrous structures and are made of Polyvinylidene fluoride (PVDF) material. The transmembrane pressure is 0.5–0.8 Bar. They follow the mechanism of crossflow filtration. These membranes possess lower fluxes and more membrane area. High tolerance of TSS is observed (up to 2000 ppm). These membranes do not require any pre-filtration and have less clean-in place (CIP) requirement due to the continuous self-cleaning of the membranes even with low air pressure.
1.2.1.4 Conventional Ultrafiltration Membranes
These membranes, made of PVDF material, have closed and hollow fibrous structures. The transmembrane pressure is 0.5–2.0 bar. A crossflow deadend filtration type mechanism is followed. These membranes possess higher flux with less membrane area. Pre-filtration is required, and low tolerance of TSS (up to 50 ppm) is observed in these membranes. Also, frequent cleaning of membranes is required through back-wash pumps and CIP.
1.2.2 Nanofiltration
Nanofiltration (NF) is the filtration process to concentrate components with molecular weight >1000 Da. NF can also eliminate solutes in the 0.0005–0.007 μm range with molecular weight >200 Da. The operating range of NF lies betwixt ultra-filtration and reverse osmosis (RO) processes [14]. The membrane of this process comprises thin films of polymer composites possessing negatively charged functional groups. Adding CeO2/Ce7O12 and polyether sulfone can embed antifouling properties in membranes. NF can extract Fe3+, Al3+, Co2+, Cd2+ and Cu2+ from PPIW with an efficiency of 94 to 98% [15, 16].
1.2.3 Microfiltration
The microfiltration (MF) process involves a microporous membrane to separate micron-sized particles, microbes, and contaminants from wastewater. The MF technique is a membrane process driven by low pressure. The pore size of this type of membrane lies in the range of 0.1–10 μm. Various materials, such as polysulfone, ceramics, polypropylene, silica, polyamides, cellulose acetate, polycarbonate, cellulose esters, and some composite materials, are used to manufacture such membranes. This technique is commercially applied in the pharma and biological industries. This technique is not famous for removing heavy metal ions due to the lesser ability of ion separation from wastewater [17].
1.2.4 Forward Osmosis
The forward osmosis (FO) technique is used as a membrane to clean the feed solution without external pressure. Osmotic pressure on the side of the draw solution is usually higher than the other side of the membrane, i.e., on the feed solution side. Due to this pressure difference, the water moves from the lower pressure side, i.e., the feed solution side, to another side of the membrane, i.e., the draw solution side. In contrast, pollutants do not pass through the membrane and stay on the feed solution side. Since no external pressure is needed in FO, it is an energy-saving, eco-friendly technology for wastewater treatment. Nevertheless, forward osmosis has some limitations also, like reconcentration in draw solution, challenges in membrane selection, and internal and external concentration polarization [18–20].
1.2.5 Reverse Osmosis
Reverse osmosis (RO) is a process of pressure-driven type separation in which solution passes through a semipermeable membrane with a pore size betwixt 0.5–1.5 nm that only allows smaller molecules to pass through it. It is clear from the name that this process is the opposite of the normal osmosis process and works under a pressure of 20–70 bar. A membrane with such a small pore size blocks solutes between 0.00025–0.003 μm. RO can extract about 95-99% of pollutants from wastewater. Due to its compact design and high efficiency, RO is widely used in wastewater treatment at the industrial level. The most common disadvantage of RO is deterioration and membrane fouling, which reduces efficiency. Using this technique, various metal ions such as Ni2+, Cr6+, Cu2+, Fe3+, Zn2+, Ni2+, As3+, Sb3+ etc. can be separated from wastewater generated by various industries [21].
1.2.6 Electrodialysis
Electrodialysis (ED) is a technique that separates heavy metal ions under the influence of electric potential difference. In parallel form, alternatively placed cation exchange membranes (CEM) and anion exchange membranes (AEM) are used to eliminate the metal ions from wastewater. From the feed solution, cations pass through CEM, and anions pass through AEM, and these ions are attracted toward the oppositely electrically charged pole. Half of the ED channel produces treated water, i.e., dilute, whereas half expels the concentrated stream. This technique offers various advantages such as a higher rate of water recovery, free of chemicals, no reaction, and can work almost at each pH. However, this technique also encounters disadvantages such as fouling, costly membranes, and the requirement of electric potential. ED has been used to separate Ni2+, Pb2+, K+, Cu2+, Cd2+, Fe3+, Cr6+, Zn2+, As3+, As5+ etc from wastewater [22–26].
1.2.7 Membrane Distillation
Membrane distillation (MD) is a hybrid technique that works under the influence of thermal energy to clean water through the membrane. In this technique, cold and hot water sections are separated by a microporous hydrophobic membrane, which allows water vapors to pass through it and hinder the rest of all molecules. This technique works in four configurations, i.e., sweeping gas membrane distillation, direct contact membrane distillation, vacuum membrane distillation, and air gap membrane distillation. MD technique is very effective, achieving about 96% removal of heavy metals such as As3+, Ca2+, Mg2+, Fe3+, Fe2+, As5+ etc [27, 28].
1.2.8 Liquid Membrane Technology
Liquid membrane (LM) is formed using a thin-layer organic phase that works like a barrier between two liquid phases. LM is non-mixable to feed and permeate solutions; the wastewater treatment process is a single-step process. LM technique is more efficient, very selective, and specific. However, this type of membrane encounters the disadvantage of low stability. Various types of liquid membranes, such as bulk liquid membrane (BLM), supported liquid membrane (SLM), polymer inclusion membrane (PIM), and emulsion liquid membrane (ELM), are used for water treatment. Among these membrane techniques, the SLM process extracts heavy metals like Zn2+, Cd2+, Cu2+, and Fe3+ from wastewater [29–31].
1.3 Membrane Classification
Membranes can be classified based on their structure, i.e., microporous and asymmetrical membranes. Figure 1.6 shows the sub-classification of microporous and asymmetric membranes.
1.3.1 Microporous Membranes
Microporous membranes (MM) are quite indistinguishable in a functioning and structural manner from a traditional filter. A microporous membrane has a thin wall with a spongy morphological design and pore size ranging between 0.01 to 10 μm. MMs possess a stiff and highly voided structure in which pores are interconnected. The main difference between ordinary filter and membrane is the pore size; in the case of the membrane, the pore size is very tiny, lying in the range of 0.01 to 10 μm in diameter. The principle of the membrane is quite simple as it allows water molecules to pass through, whereas it completely blocks the passage of all molecules larger than its pore. In microporous membranes, solute separation is a function of molecular size and pore size distribution. Further, MMs are of two types, isotropic and anisotropic. The fundamental difference between both of them is pore size distribution; in the case of the isotropic membrane, there is uniform pore size all over the membrane structure, whereas, in the case of the anisotropic membrane, there is observed a variation in membrane pore size [32, 33]. MMs are generally made from polymers; a variety of polymers are available in the market, but only a few of them are used to make membranes, e.g., cellulose acetate, polysulfone, and polyvinylidene difluoride [34, 35].
Figure 1.6 Classification of membranes.
1.3.1.1 Cellulose Acetate
This material is one of the first polymer materials to make membranes for RO, UF, and NF applications. Since this membrane is hydrophilic thus, it is more resistant to fouling. The main disadvantage of cellulose acetate membrane is its small pH range and working temperature. Also, since it is a cellulose-based membrane, it is vulnerable to microbial attack [36, 37].
1.3.1.2 Polysulfone
Polysulfone has been the only polymer used in UF and MF membranes since 1975. The significant merit of this polymer membrane is its wide range of resistance toward temperature and pH. This membrane is the sole membrane used in food and dairy applications. The main problem with this membrane is that it is vulnerable to oil, fat, polar solvents, and grease attack [38, 39].
1.3.1.3 Polyvinylidene Difluoride
Polyvinylidene difluoride is a conventional material for membrane manufacturing but is utilized sparingly due to the difficulty of making membranes with good and homogeneous separation properties using this material. The chief merit of this membrane is that it shows excellent resistance toward various hydrocarbons and oxidizing agents [40–42].
1.3.2 Asymmetric Membranes
Asymmetric membranes are comprised of two top layers. One of them is known as the skin, and the second layer is a porous material that acts as a supporting base for the skin. The skin for the asymmetric membrane is manufactured using graphite, metal, ceramics, metal oxides, and various polymers. The skin layer in asymmetric membranes is developed by deposition from solution or plasma and is termed a “non-integrally skinned” structure, otherwise called a composite membrane. These membranes are most suitable for vast volumes of high-load wastewater because the rejection occurs at the surface, and the pore lying under the skin seldom gets clogged. Other asymmetric membranes are classified into two categories, integral asymmetric membranes and composite membranes [43].
1.3.2.1 Integral Asymmetric Membranes
Integral asymmetric membranes comprise two layers, a fine-skin layer and a supporting porous layer. Asymmetric membranes are prepared in a single step, whereas the preparation of composite membranes involves two or more steps. Manufacturing integral asymmetric membranes is done via NIPs (non-solvent-induced phase separation) and TIPs (thermally induced phase separation). NIPs have advantages like low equipment demand and minimum energy consumption, whereas higher solvent need, minimum porosity, and environment poisoning are some disadvantages. Compared to NIPs, TIPs possess a uniform membrane structure, which is easy to handle with superior mechanical strength and applicability to many materials. The main disadvantage of this approach is high energy consumption [44, 45].
1.3.2.2 Composite Membranes
Composite membranes consist of at least two layers of two different materials. The single-layered composite membrane consists of a thin film atop a microporous structure. In contrast, the multilayer composite membrane possesses many layers of different materials in which each layer can perform a specific function. Composite membranes are used instead of anisotropic due to higher fluxes, better selectivity, and a non-fouling structure [46, 47].
1.4 Application of Membrane Technology in the Pulp and Paper Industry
1.4.1 Nano and RO Membrane-Based Separation
Mänttäri and Nyström [48] employed a membrane filtration technique to treat wastewater from two PPIs. NF membranes and low-pressure RO membranes were used to study and compare the effects of retention, flux, permeate quality, etc. The NF and RO membranes used for the study had a 0.045 m2 surface area. Pre-determined combinations of NF and RO membranes were used for the study, namely NF 270, Desal-5-DL, TFC ULP, and ESPA3. Before the experiments, pure water was passed through membranes for one hour. The experiments were carried out for 3 hours in batch mode by recirculating the permeate and concentrate back to the feed vessel. Samples of original feed, permeate, and concentrate from all membrane combinations were analyzed for color, conductivity, pH, BOD, COD, dissolved inorganic carbon (DIC), dissolved organic carbon (DOC), total dissolved carbon (TDC) and UV absorbance, etc. Various types of equipment used for the determination of these parameters were Shimadzu TOC-5000A analyzer (TDC, DOC), UV-vis spectrophotometer (UV absorbance), DRLange ECM Sensor BOD apparatus (BOD), Hach spectrophotometer (color, COD) and atomic absorption spectrometry (metal ion concentration). Other parameters were calculated as total residue (drying of total solids at 378 K), total fixed residue (ash content at 823 K), volatile solid content (difference between total fixed residue and total residue), and DIC (difference of DOC and TDC).
The treated wastewater from pulp mills had lower permeability because of its high inorganic content. Also, this water fouled all sets of membranes, specifically RO membranes. Fouling percentages for different membranes caused due to pulp and paper mill wastewater and pulp mill wastewater were calculated, which were NF 270 (15% and 21%), Desal-5-DL (21% and 16%), TFC ULP (23% and 67%) and ESPA3 (25% and 49%) respectively. This happened due to a more significant osmotic pressure difference on the membrane side of pulp mill wastewater as it had more significant impurities than pulp and paper mill wastewater. The level of impurities highly affected the performance of membranes; however, researchers have emphasized using NF membranes for wastewater filtration due to better efficiency. It was also stated that permeate from NF membranes had good potential for reusage in paper industries. Table 1.1 can be consulted to analyze rejection percentages of various impurities after treatment through different membranes [48]. Also, the performance of NF membranes was found to be better than RO membranes in the case of lower fouling and higher flux. In contrast, RO membranes showed better monovalent ion passage and sulfate retention characteristics.
1.4.2 Flocculent-Based Pre-Treated RO Membrane Separation
Li et al. [49] treated wastewater using PAFSSB flocculant as a pre-treatment for reverse osmosis of PPIW. The researchers stated that PPIW needs to be passed through RO membranes for proper disposal, but before passing it through RO membranes, it needs pre-treatment. Therefore, in this research article, researchers have studied the performance of the PAFSSB flocculant for its effects on the wastewater before it is fed to RO membranes. The wastewater directly obtained from the papermaking industry was analyzed for COD (40 mg/l), pH (6.92), turbidity (0.2 NTU), NH3-N (1.46 mg/l), and EC (77.4 us/cm). SEM analysis of the flocculants was carried out after the flocculation of wastewater was done. For PAFSSB flocs, large and regular ball chains or long chains were observed. This suggested strong adsorption, precipitation, and bridging effect. Wastewater samples and different doses of flocculants were mixed and placed on the flocculating device. After a considerable time, the supernatants were analyzed. Optimal process parameters were obtained by analyzing kinetic factors, pH, dosage, etc. The researchers also studied the effects of different flocculants such as PAC, PAS, PFS, PAFS, PAFSS, and PAFSSB on COD removal. It was observed that these flocculants reduced COD levels by 55%, 54%, 50%, 54%, 44%, and 75%, respectively. Therefore, it was suggested that PAFSSB has the best COD removal effect on wastewater, as the COD came down to 10 mg/l from 40 mg/l after flocculation. The phenomenon was explained by polyhydroxy complex ions Alb and Feb in the flocculant, which was responsible for doubled flocculating ability. The optimal PAFSSB dosage was found to be 1.3 ml/l which was attributed to the suspended solid content of the solution. 6.5-7.5 was observed as the optimal pH range. At optimal pH, the hydrolysis products in the flocculants tend to create clusters or groups, which results in enhanced agglomeration of impurities. A rapid stirring speed of 60s (300 r/min) and a slow stirring speed of 10s (50 r/min) were the optimal kinetic factors. The results suggested that the flocculant successfully reduced the COD of wastewater up to 75% before passing it through RO membranes. Finally, it was concluded that PAFSSB, a cheap and highly effective flocculant, has excellent potential for pre-treatment PPIW before introducing to RO membranes.
Table 1.1 Rejection percentages of impurities obtained for discharge wastewater after treatment through different membranes.
Type of membrane
Retention (%)
Inorganic matter
Cl
-
SO
4
2-
Ca
2+
Na
+
DOC
COD
BOD
5
Color
PPI-1
NF270
95
36
100
99
92
100
95
85
100
Desal-5 DL
88
-14
100
99
80
100
96
85
100
TFC ULP
98
96
99
99
98
99
98
74
100
ESPA3
99
98
100
100
99
100
100
88
100
PPI-2
NF270
94
-38
99
97
92
100
98
53
100
Desal-5 DL
91
-90
99
97
86
100
99
59
100
TFC ULP
97
95
99
96
97
99
95
81
100
ESPA3
97
94
98
99
97
99
97
83
100
1.4.3 Ultrafiltration Membrane Separation
Simonič et al. [50] investigated the potential of UF membranes for treating PPIW for maintaining various water quality parameters such as COD, TSS, TDS, etc. UF was carried out using ceramic tubular membrane modules with a membrane area of 0.23 m2 and 50 nm pore diameter. Al2O3 and ZrO2 were utilized for the preparation of the active surface layer. Initial parameters for wastewater were determined as COD (880 mg/l), pH (7), and TSS (240 mg/l), which were calculated using titration, pH meter, and filtration, respectively. Also, EC (1253 ms/cm) was measured using a conductometer, absorbance at 254 nm (2.14) using a spectrophotometer, and turbidity (174 NTU) through a turbidity meter. The UF experiments were carried out at neutral pH, acidic pH (5.6), and alkaline pH (8.3). Before UF, the wastewater was pre-treated in the form of mechanical filtration. After filtration, the parameters of all three UF types were again examined. For neutral pH, results were as follows: pH (7.4), EC (1104 ms/cm), turbidity (0.7 NTU), absorbance at 254 nm (0.53), COD (420 mg/l) and TSS (0.9 mg/l). At acidic pH, results obtained were pH (6.1), EC (1712 ms/cm), turbidity (0.2 NTU), absorbance at 254 nm (0.40), COD (220 mg/l), and TSS (0.4 mg/l). Also, for alkaline pH, results were observed as pH (8.5), EC (990 ms/cm), turbidity (1.0 NTU), absorbance at 254 nm (0.58), COD (200 mg/l) and TSS (0.5 mg/l). The results clearly stated that conductivity increased while turbidity and TSS decreased at acidic pH conditions of UF. Alkaline and neutral pH observed precipitation of calcium carbonate leading to clogging of membranes. Researchers have stated that ceramic membranes have a lower fouling index when compared to polymeric membranes. It was also stated that the fouling of membranes occurred due to the deposition of suspended solids and colloidal matter at the surface of the membrane. A stable permeate flux of 75 L/h m2 was obtained at a pressure of 1.6 bar for the membrane employed. Finally, it was claimed that UF membranes caused 99.7%, 81.3%, 75.0%, and 99.8% reductions in turbidity, absorbance, COD, and TSS, respectively. The highest performance of UF membranes was observed at pH 6.
1.4.4 Combination of Ultrafiltration and Nanofiltration Membrane-Based Separation
Bates et al. [51] applied a combination of UF and NF membranes to treat PPIW efficiently. The wastewater generated from papermaking industries has a high temperature, pH, and organic matter values. Researchers employed a sulfonated polyethersulfone NF membrane for treatment at a pilot scale, lowering pH and organic matter content, thus allowing the membrane to operate at high recovery. But when the same membrane was tested at plant scale, it started fouling too much because of fine colloidal particles. Therefore, a capillary UF pre-treatment system was utilized before NF treatment to reduce fouling. Membranes were selected based on their properties, such as suitable pH and thermal stability, ability to retain hydroxides, and reject color-inducing lignins. The NF membrane selected by researchers was highly negatively charged and achieved porosity in the range of 500-3000 molecular weight cut-off. Because of the charge-charge repulsion, the negative charge of the membrane helps in rejecting color, organics, and other negatively charged ions. The wastewater from the pulp and papermaking plants had EC (2260 uS/cm), color (2730 PCU), and TOC (600 mg/l).
After treatment through NF membranes, the values effectively reduced to EC (790-1020 uS/cm), color (21 PCU), and TOC (126 mg/l). Feed conditions for wastewater treatment were kept at TSS (10 mg/l), pH (10.3), temperature (49°C), and turbidity (6 NTU). These parameters from the pilot plant were supported by a 4.5 gpm permeate flow rate, 14 flux, and 80-96% recovery rate. At this point, researchers noticed a high fouling rate of NF membranes at the plant scale. Therefore, they employed UF membrane (PES membrane fibers) having an inner diameter of 0.8 mm and an outer diameter of 1.3 mm. Other distinguished membrane characteristics were surface area (500 ft2) in one 60” long module, 200,000 ppm-hrs chlorine tolerance, 100,000 Dalton molecular weight cut-off, and continuous operability at pH 4-11. The UF membrane treatment was also tested at feed conditions of TSS (10 mg/l), pH (10.3), temperature (49°C), and turbidity (6 NTU).
Results revealed that turbidity lowered from 6.1 to 0.24 NTU, TSS reduced to less than 5 from 8.7 mg/l, and TOC level depleted to 530 from 580 mg/l. However, no change in color was observed. Also, the UF membranes operated at 32 GFD of flux, 11.1 gpm permeate flow rate, and 83% recovery rate. NF and UF membranes were observed as separately overcoming each other’s shortcomings. Hence, finally, researchers decided to employ a combination of UF membrane treatment followed by NF membrane treatment. Values for various parameters for UF feed, UF filtrate/NF feed, and NF filtrate after treatment were observed as TDS (2345, 1928, and 973), Colour (12,000, 12,000 and 20), TOC (580, 530, 53) and TSS (8.7, <5 and <5) respectively. UF membranes successfully removed fine particles, whereas NF membranes removed color content from wastewater. The membranes operated at a 90% recovery rate, rejecting only 50% of inorganic matter content. The color was also reduced to 20 PCU from 12000 PCU. Thus, a combination of UF and NF membranes successfully treated pulp and papermaking plant wastewater with very high recovery rates, achieved desired rejections, and overcame one another’s shortcomings.
1.4.5 Pilot Scale-Based Membrane Separation in Pulp and Paper Industry
1.4.5.1 Pilot Plant for the Demonstration of Membrane Filtration (MF) in Indian Pulp and Paper Mills
A pilot membrane filtration plant of 3 m3/hr capacity was set up in some Indian paper mills to treat PPI effluents which include paper machine back-water, ETP outlet, and bleach plant extraction stage effluent to significantly reduce TDS, TSS, BOD, COD, Colour, and other toxic pollutants. Other objectives included are to reduce freshwater consumption and wastewater discharge by increasing recycling of treated effluent, at-source reduction of chloro-organics in bleach plant alkaline extraction-stage stream to obtain the permeate with reduced color and organics levels which can be recycled within various unit operations to reduce ETP load [7].
The pilot plant consisted of a UF feed water/pre-settling tank of 5 m3 capacity. The feed was subjected to a Submerged UF system of 3 m3/hr capacity. The retentate was sent to the sludge storage tank, from where it was sent back to the pre-settling tank. However, the permeate is sent to a Nano/RO system from a micron cartridge filter with the help of a high-pressure pump. With an 80% recovery rate, the recovered permeate was sent to the nano permeate tank of 2 m3 capacity, whereas the retentate was sent to the nano reject tank of 1 m3 capacity. The results obtained from pilot trials of membrane filtration in the integrated paper mill are presented in Figure 1.7[7].
1.4.5.2 UF Membrane E-Stage Bleach Plant Effluent – Commercial Application
UF membranes are commercially utilized to treat E-stage effluent from bleaching plants, which carries 30% of BOD, 60% of COD, and over 80% of total color. A combination of UF followed by NF membranes can successfully remove BOD (45%), COD (60%), and color (over 85%). The concentrate obtained from UF membrane has a low chloride content and a good heating value (10 MJ/kg), so it can be burnt effectively in the recovery boiler. However, UF cannot retain salts and colors of low molecular weight [7].
Figure 1.7 Results of pilot trials of membrane filtration in an integrated paper mill.
The commercial UF system installed at Sanyo Pulp Mill, Japan, achieved a significant reduction in COD (82%) and color (94%) with a flux of 98 L/m2h. The system uses a UF flat membrane with a MWCO of 6000 D capacity of 2,500 m3/d. Also, the commercial UF system installed at MoDo Kraft Mill, Sweden, achieved reduction in dissolved solids (30%), color (81%), and AOX (52%) [7].
1.5 Conclusion
Membrane filtration may optimize loop closure and therefore help to reduce fresh water intake as well as wastewater treatment in pulp and paper mills. Membrane technology is increasingly being adopted when manufacturers are closing their mill production process. Membrane filtration offers a physical barrier to impurities; the wide range of membrane types allows efficient water recycling. Other valuable benefits of the process are the reduction and removal of non-biodegradable organic/inorganic substances, improved product quality because of lower pollution of loop water, reuse of treated effluent in production, recovery of valuable substances such as lignin-based products, coating pigments and minimizing environmental impact because of improved effluent quality.
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