Environmental Fate and Effects of Pulp and Paper

Mill Effluents

Mark R. Servos

• Publisher: CRC Press
• Year: 2020
• Print ISBN: 9781884015717
• eBook ISBN: 9781000725131
• Edition: 1
• Topic: Naturwissenschaften
• Subtopic: Umweltwissenschaft

In recent years, there have been emerging concerns regarding the fate and effects of pulp and paper mill effluents on the environment. Countries throughout the world are focusing attention on the implementation of regulatory and monitoring programs. In response, industry has begun to implement a variety of process and treatment technologies designed to minimize or eliminate the potential impacts.
Environmental Fate and Effects of Pulp and Paper Mill Effluents explores the most active and critical current research and experimentation from around the world. This comprehensive overview examines the identity and origin of chemicals in pulp mill effluents, environmental fate of chemicals from pulp and paper mills, bioaccumulation of substances from pulp mills to fish and wildlife, field and laboratory studies of biochemical and whole organism responses associated with pulp and paper effluents, integrated monitoring and future research, and policy directions of this rapidly evolving field.
Written by prominent scientists from around the world with contributions from industry, government, and academia, this important new book provides a balanced global perspective of the recent scientific findings and the challenges being faced in the immediate future.

SECTION I

IDENTIFICATION AND ORIGIN OF CHEMICALS AND TOXICITY

Pulp and paper mill effluents are complex mixtures. The characteristics of each effluent are dependent on numerous factors including wood furnish and process technology (including washing, cooking, bleaching, prebleaching, etc.), as well as final effluent treatment. The chemical composition of each effluent varies drastically, as does the toxicity. In an effort to remain competitive, as well as meet new environmental regulations, mills have been rapidly modifying process, bleaching and treatment technologies. These changes have led to dramatic changes in the chemical composition and toxicity of the final effluent. Recent studies have focused on understanding the chemistry, sources and fate of specific chemicals and toxicity within the mills. Considerable progress has been made toward understanding and controlling the release of contaminants, which has greatly reduced the potential threat to the environment.

EFFECTS OF INTERNAL PROCESS CHANGES AND EXTERNAL TREATMENT ON EFFLUENT CHEMISTRY

Lars Strömberg^1,2, Roland Mörck, Filipe de Sousa and Olof Dahlman

¹STFI, Box 5604, S-11486 Stockholm, Sweden

²Present Address: AssiDomän, S-10522 Stockholm, Sweden

During the last decade, a rapid development and introduction to mill-scale of new and modified techniques for production of bleached kraft pulp has occurred in the kraft pulping industry. The main objectives of this development have been to reduce the amount of residual lignin entering the bleach plant and to reduce and subsequently eliminate the use of chlorine in the bleaching process, thereby minimizing the discharge of chlorinated organic matter. This development will also facilitate the closure of the water system in the bleach plant. Results from chemical characterization of effluents from Swedish bleached kraft mills show that the combination of extended delignification in the cooking stage, oxygen delignification and ECF bleaching is capable of bringing the discharge of AOX down to such a low level as 0.2 kg ptp before secondary effluent treatment and to 0.1 kg ptp after secondary treatment. The reduction in the quantity of chlorinated phenolic compounds, resulting from the introduction of ECF bleaching, is even more pronounced than the AOX reduction. TCF bleaching practically eliminates the discharges of chlorinated compounds. Thus, the chlorine content of high molecular weight effluent materials from TCF bleaching of softwood and hardwood kraft pulps was extremely low and fully comparable to the chlorine content found in naturally occurring humic materials. The contents of extractives such as fatty acids, resin acids and sterols in untreated kraft mill effluents were found to vary considerably between different mills. Other factors than the type of bleaching process used may be of large importance for these variations. An effective removal of extractives was observed both in aerated lagoons and in activated sludge plants.

INTRODUCTION

In response to environmental concerns as well as to government regulations on emission of chlorinated organic matter and to market demands, the pulp and paper industry has acted worldwide since the mid-1970s by developing and introducing a number of new processes and process modifications in order to minimize the effluent load of organic matter. Special interest has been directed towards the formation and discharge of chlorinated organic matter. The main strategy behind the development of internal process changes has been to remove as much lignin as possible before the pulp enters the bleach plant and in the last few years also to replace chlorine in the bleaching process by substituting it for other bleaching agents. These advancements have recently been reviewed from an environmental point of view (Axegård et al. 1993).

In order to evaluate the environmental impact of effluents from the production of bleached softwood and hardwood kraft pulps according to the pulping and bleaching technology applied in Swedish mills today, comprehensive chemical and biological characterization studies have been carried out (Haglind et al. 1993). This paper presents the results of studies on the chemical composition of bleached kraft mill effluents (BKMEs) from mills using either conventional or modified cooking in combination with oxygen delignification and elemental chlorine-free (ECF) or totally chlorine-free (TCF) bleaching. The studies have been carried out within the SSVL Environment 93-project – a research project conducted by the Swedish pulp and paper industry.

In order to illustrate the effects of recent process development on the chemical composition of the organic effluent material, the results obtained in the present investigation are compared with corresponding data from somewhat older processes using chlorine as a bleaching agent. In this project, effluents from mills with different types of process conditions were studied both before and after secondary effluent treatment.

MATERIALS AND METHODS

BKMEs were sampled at five kraft mills producing bleached softwood pulp and at two mills producing hardwood kraft pulp. All effluents except those labeled SW-1 and SW-5 were studied both before and after secondary effluent treatment. Process data relevant for the sampling occasions are given in Tables 1 and 2. All effluent samples studied were 24 h composite samples.

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Table 1. Cooking, bleaching and effluent treatment processes studied.

Effluent	Type of Pulp	Cooking Process	Bleaching Process	Effluent Treatment

Table of contents

• Cover
• Title Page
• Copyright Page
• Table of Contents
• Acknowledgments
• Preface
• Foreword: Where were we in 1991?
• Section I: Identification and Origin of Chemicals and Toxicity
• Section II: Environmental Fate
• Section III: Bioaccumulation of Substances from Pulp and Paper Mills to Fish and Wildlife
• Section IV: Field and Laboratory Studies of Biochemical Responses Associated with Pulp and Paper Mill Effluents
• Section V: Field and Laboratory Studies of Whole Organism Responses Associated with Pulp and Paper Mill Effluents
• Section VI: Integrated Monitoring
• Section VII: Future Directions
• Keyword Index